Biogas Systems in
India
by Robert Jon
Lichtman
Illustrations by
William Gensel
VITA
1600 Wilson Boulevard,
Suite 500
Arlington, Virginia
22209 USA
Tel:
703/276-1800 * Fax:
703/243-1865
Internet:
pr-info@vita.org
in cooperation
with
The Committee on Science
and Technology
for Developing Countries
(COSTED)
Central Leather Research
Institute
Adyar, Madras 600 026
India
This publication is one
of a series
issued by VITA to document
the activities
of its worldwide Renewable
Energy Program.
ISBN
0-86619-167-4
Composed and produced in Arlington,
Virginia, by VITA, Inc.
[C] 1983, Volunteers in Technical Assistance, Inc.
Table of
Contents
Preface
Abbreviations
and Terminology
Introduction
I.
Rural Energy Consumption and Biogas
Potential
II.
An Overview of Biogas Systems
III.
Digester Designs
IV.
System Operation
V.
Gas Distribution and Use
VI.
Economic Analysis of a Village System
VII.
Village Utilization
VIII.
Conclusions and Recommendations
Notes
Appendix
Bibliography
Preface
An important
common theme underlies much of the current literature
on the
application of technology within both developed and
developing
nations. Any technology has a complex
series of
impacts on
the environment in which that technology operates.
The concern
over a technology's "appropriateness" is based on
the need to
determine clearly who will be affected by use of
the
technology and in what ways.
Behind the
concept of "appropriate technology" is the belief
that the
complex interactions between a technology and its
environment
should be made "visible."
Only then can a technology
be evaluated
properly. By describing explicitly the
impact
of a
technology, the selection criteria for the technology also
become
explicit. If we choose a technology
that pollutes a
river, but
which also provides permanent jobs for 10,000 workers,
we presumably
either value employment benefits over
environmental
costs or else were ignorant of the pollution
effects at
the time we made the decision.
The choice of
a technology is "appropriate" or "inappropriate"
only in the
context of the demands we place upon it.
The subtle
trade-offs
between these often conflicting demands are at the
real core of
any debate over the choice of a technology.
Appropriate
technology is
less a problem of hardware than of appropriate
data
collection, decision-making, financing, installation,
and use--with
all the problems of sorting out competing
demands and
value judgements in each of these tasks.
This study is
an assessment of the "appropriateness" of biogas
technology in
meeting some of the needs of India's rural population.
Such an
assessment is quite complicated, despite claims
that a biogas
system is a simple village-level technology.
While there
is evidence that biogas systems have great promise,
they are
subject to certain constraints. It is
impossible to
describe here
all the factors that one might study to assess
any
technology. I only hope that the
approach used in this
study will
help others.
One
difficulty in studying biogas technology is the fragmented
and often
anecdotal nature of the research and development
work.
In order to provide this snapshot of the
state-of-the-art
in India, I
have had to enlist the aid of a bewildering number
of government
officials, industrialists, university researchers,
missionaries,
social workers, journalists, voluntary
groups,
farmers, merchants, and villagers.
While I will
never be able
to express fully my gratitude to the hundreds of
people who
have helped me piece this puzzle together, I am
particularly
indebted to the following:
Dr. A.K.N. Reddy, and the ASTRA team,
Indian Institute of
Science, Bangalore; K.K. Singh, PRAD,
State Planning
Institute, Lucknow; Dr. Ram Baux Singh,
Etawah; T.R.
Satishchandran, Energy Adviser, Planning
Commission,
Government of India; Dr. S. Shivakumar,
Madras Institute
of Development Studies; Dr. C.R.
Muthukrishnan, IIT,
Madras; John Finlay and David Fulford of
Development and
Consulting Services, Butwal Technical
Institute, Butwal,
Nepal; D. Kumar and M. Sathianathan,
Center for Science
for Villages, Wardha; Dr. C.V. Seshadri
and Rathindranath
Roy, Murugappa Chettiar Research Centre,
Madras; C.R. Das,
Coordinator, Tata Energy Research
Institute, Bombay; and
the staff at the Central Leather Research
Institute,
Madras, all of whom were extremely
helpful, generous, and
patient with a stranger in a strange land.
I am
extremely grateful to Dr. S. Radhakrishnan, Scientific
Secretary of
the Committee on Science and Technology in Developing
Countries
(COSTED), Indian Institute of Technology,
Madras, for
his constant trust and financial support throughout
the course of
my research. John Westley and the staff
of the
U.S. Agency
for International Development (USAID), New Delhi
Mission,
provided both editing and typing assistance, as well
as a research
grant (USAID/India Purchase Order IN-P-O-67).
The
staff of
Volunteers in Technical Assistance (VITA) spent many
long hours
editing the final manuscript and bringing it out in
its present
form. Of course, the views expressed in
this study
are my own,
and do not represent the official position of VITA,
USAID, the
U.S. Government, or any other body.
Finally, I am
deeply indebted to Dr. Y. Nayudamma, Distinguished
Scientist,
Central Leather Research Institute, Madras.
without his
guidance, friendship, and unyielding support, none
of this would
have been possible. All of these
individuals have
immeasurably
deepened my understanding of biogas technology, as
well as of
India itself. Any errors or omissions
contained in
this study
are due to my own failure to utilize their considerable
insights.
Robert Jon Lichtman
December
1982
Abbreviations
and Terminology
BHP
= brake horsepower
crore
= 10,000,000 rupees
hr
= hour
kcal
= kilocalorie (1,000 calories)
kwh
= kilowatt-hour
lakh
= 100,000 rupees
[m.sup.3] =
cubic meter
MT
= million tonnes
MTCR
= million tonnes of coal replacement
Rs
= Indian rupee(s)
tonne
= metric ton (1,000 kg)
Rs 1.00
=
US$0.125 at the time of this study
Introduction
The term
"biogas" system is somewhat of a misnomer.
Though
biogas
systems are often viewed as an energy supply technology,
the Chinese
regard their systems primarily as a means to provide
fertilizer
and the sanitary disposal of organic residues.
Gas is
considered a useful by-product.(1) In
India, interest in
biogas is due
to its potential as a fuel substitute for firewood,
dung,
kerosene, agricultural residues, diesel, petroleum,
and
electricity, depending on the particular task to be performed
and on local
supply and price constraints. Thus,
biogas
systems
provide three primary products: energy,
fertilizer, and
waste
treatment. For the sake of convenience,
the term "biogas
system"
in this study will refer to the technology of digesting
organic
wastes anaerobically to produce an excellent fertilizer
and a
combustible gas, and to dispose of agricultural residues,
aquatic
weeds, animal and human excrement, and other organic
matter.
While use of
biogas systems is not restricted to rural areas,
the
difficulties of retrofitting such systems in urban areas,
supplying a
balanced charge of biomass, generating adequate
pipeline
pressure, and minimizing capital costs all suggest
that biogas
systems will be more easily adapted, in the short
term, to
rural areas. This study therefore is focused
on rural
utilization
of biogas systems.(2)
I.
Rural Energy Consumption
and Biogas Potential
Biogas has
great potential for supplying energy for cooking,
lighting, and
small-scale industry in rural India. This
section
will show
through a series of calculations that biogas theoretically
can play a
significant, if not major, role in meeting
many of these
needs, as well as in supplying fertilizer and
helping to
solve other development problems.
Readers not
interested in
these calculations should skip to Section II on
Page 11; the
important point is that biogas holds considerable
promise and
deserves further study.
To assess
properly the potential of biogas systems for meeting
a variety of
rural needs, one would have to know the total
amount of
organic material (biomass) available annually; that
is, material
for which there are no other more productive uses.
Biomass that
could be employed as feed material would have to
be studied
carefully with respect to the annual output of each
material, the
average biogas yield per unit of material, collection
and
transportation costs, and the availability of the
material over
time.
Unfortunately
such data do not exist in India with any degree
of
reliability. No accurate data exist on
the annual supply of
water
hyacinth, congress grass, banana stems, and other biomass
that can
serve as a feed material to a biogas system.
Since many
agricultural residues are used as fodder, knowledge
of the net
availability of these residues is important to avoid
conflicting
demands on their use. Statistics on the
amount of
residue per
crop, though available, tell nothing of the end use
of the
residue. Revelle cites aggregate
figures of 34-39 MT of
crop residues
consumed annually as fuel.(3)
Even annual
dung output is a matter of some controversy.
Desai
estimates
that out of the 114-124 MT (dry weight) of dung produced
annually,
about 36 MT dry weight are burned as fuel.(4) The
Working Group
on Energy Policy calculates that 73 MT of dung
are used as
fuel,(5) without specifying if this is a dry weight
figure (dry
weight = approximately 1/5 of wet weight).
Revelle
uses a World
Bank estimate of 68 MT burned as fuel (out of a
total of
120-310 MT) and suggests that 83 percent of this, 56
MT (dry
weight), is consumed in rural areas.(6)
The Indian
Ministry of Agriculture offers data on livestock
Population
and dung voided per animal per annum as shown in
Table
I-1. Again, there is uncertainty about
the percentage of
dung produced
in rural areas. To be conservative, we
will
assume that
there are roughly 237.5 million cattle, buffalo,
and young
stock (from Table I-1), and that their collectible
daily yield
from night droppings (when cattle are tied up near
a dwelling)
is approximately 8.0 kg per head.(7)
Using Revelle's
estimate of
rurally produced dung at 83 percent of the total,
annual rural
dung production would be over 575.6 MT wet weight,
or 115.1 MT
dry weight.
Various
estimates shed little light on the percentage of dung
collected, or
on factors affecting dung output, such as cattle
species, body
weight, diet, etc. Data will also vary
regionally
and
seasonally. If we assume that there is
a 20 percent weight
loss during
collection of the 115.1 MT dry weight of rural dung
(calculated above),
then the net available dung is 92.1 MT.
To
this can be
added 34 MT dry weight of crop residues that are
burned
annually. This gives a total of about
126 MT (dry) of
biomass that
is available for biogas systems.
Assuming an
average gas
yield of 0.2 [m.sup.3]/kg (dry) for the biomass(8) and a
calorific
value of 4,700 kcal/[m.sup.3] for biogas(9), the available
biomass would
yield roughly 25 billion [m.sup.3] for biogas.
This is
Table I-1
Potential Annual Availability of Dung (1972)(10)
Annual
Number of
Daily
Output/hd. Total
Animals
Output/
(millions
(millions
Livestock
(Millions)
Head (kg) of
tonnes) of tonnes)
Cattle
131.4
10
3.65 479.6
(3 + years
old)
Buffalo
37.8
10
3.65 138.0
(3 + years
old)
Young
stock 68.3
3.3
1.20 82.0
Sheep and
goats 108.4
1.1
.4 43.4
___________
TOTAL 743.0
Total = 743
MT (wet weight)
Total minus
20 percent collection loss =
594.4 MT (wet weight)
=
118.9 MT (dry weight)
equivalent to
118 trillion kcal. This estimate
probably is low,
because it
does not include numerous weeds and aquatic biomass
that might be
used as a feedstock for biogas plants, but which
currently
have no alternative uses.
Assuming
biogas burners have a thermal efficiency of 60 percent,
the potential
net energy for cooking from biogas is
roughly 71
trillion kcal per annum. Approximately
975 trillion
kcal are
currently consumed during the burning of dung, firewood,
charcoal, and
crop residues for domestic use (cooking,
water
heating, etc.).(11) Of that figure, 87
percent is used in
cooking.(12)
Therefore, approximately 848 trillion kcal
per annum
is consumed
in cooking in rural India. This figure,
when combined
with a 10
percent average thermal efficiency of
"chulahs"(13)
(mud/clay stoves) and the vast number of open
cooking
fires, gives a net energy consumption of approximately
85 trillion
kcal per annum for cooking. We will
assume that
rural cooking
needs consume about 85 percent of this figure, so
that the
annual net energy consumption for rural areas is 72.3
trillion
kcal. Thus, biogas can essentially
provide the net
usable energy
currently consumed in cooking from all noncommercial
fuel sources
in rural India.
The amount of
total solids in biogas slurry prepared from 126
billion kg
(dry weight) of organic matter, the minimum amount
annually
available for fuel and fertilizer (from our previous
calculations),
is roughly 630 billion kg (wet weight), assuming
for
simplification that both plant wastes and dung contain 20
percent
solids.
Given current
practices, this biomass would be mixed with water
at a 1:1
ratio if it was to be fed into a biogas system.
The
total
influent would weigh 1.2 trillion kg.
Twenty percent of
this would be
lost during microbial digestion. Of the
remainder,
the
percentage of total solids per kg of weight of slurry
would be
about 6.4 percent. The digested biomass
thus would
contain 61 MT
of solids.
Table I-2
shows the relative fertilizer content of biogas
slurry and
farmyard manure.(14) Based on this
table, 61 MT of the
total solids
in biogas slurry would yield approximately 1.037
MT of nitrogen
(N), .976 MT of phosphorus pentoxide ([P.sub.2][O.sub.5]), and
.610 MT of
potassium monoxide ([K.sub.2.O]) per annum.
Without a
more detailed picture of the current end uses of
organic
residues, it is difficult to assess accurately the
potential
impact of a large-scale biogas program on overall
fertilizer
supply. Importation of chemical
fertilizer is a
function of
the gap between demand and domestic production.
Domestic
production is comprised of indigenous production of
chemical
fertilizers and the use of organic residues and wastes
that are
composted as farmyard manure. Any net
increase in the
Table I-2
Average
Fertilizer Value of Biogas Slurry and Farmyard Manure
(Percentage of dry weight)
Substance
N
[P.sub.2][.O.sub.5]
[K.sub.2.O]
Total
Biogas
slurry 1.7
1.6
1.0 4.25
Farmyard
manure + compost 1.0
0.6
1.2 2.8
amount of
fertilizer derived from organic residues can be used
to offset
imports, assuming of course that domestic production
of chemical
fertilizers remains constant. The net
increase in
available
fertilizer attributable to biogas slurry is derived
from the
following calculations:(15)
a)
[F.sub.n] = [F.sub.ba] + ([F.sub.fyma] -
[F.sub.fym])
where:
[F.sub.n] = the net increase in fertilizer
[F.sub.ba] = fertilizer value of currently
burnt biomass, if it
was digested anaerobically instead.
[F.sub.fyma] = fertilizer value of biomass
currently composted as
farmyard manure, if it was digested
anaerobically.
[F.sub.fym] = fertlizer value of biomass
currently composted as
farmyard manure.
b)
Surveys from 13 states during 1962-69 found
that 72
percent of total dung is collected on an
average from
urban and rural areas.
When this figure is combined with
earlier calculations, we find that 92.1 MT
of rural dung
(dry weight) X 72 percent = 66.3 MT of
dung (dry weight)
that is actually used as manure in rural
areas each year.
An estimated 10 MT (dry weight) of a
possible 34 MT of
agricultural residues are added to
this. This produces a
total of 76.3 MT of dung and agricultural
residues that
currently are being used for fertilizer in
rural areas.
The remaining 25.8 MT of dung and 24 MT of
agricultural
residues, or a total of 49.8 MT (dry
weight), currently
are consumed as fuel, assuming the same
rate of collection
and distribution as explained above.
c)
Using the calculations from (b) above and
Table II, the
values for [F.sub.ba], [F.sub.fyma], and
[F.sub.fym] are shown below. Values
are in MT:
N
[P.sub.2][O.sub.5]
[K.sub.2.O]
_____
_______ _______
[F.sub.ba]
.847
.797 .498
[F.sub.fyma]
1.297
1.221 .763
[F.sub.fym]
.763
.458 .916
d)
Therefore, the net increase in fertilizer
due to digesting
available organic material in biogas is
approximately:
[F.sub.ba] + ([F.sub.fyma] - [F.sub.fym])
= [F.sub.n] (a)
.847 + (1.297 - .763) = 1.381 MT of N.
.797 + (1.221 - .458) = 1.560 MT of
[P.sub.2][O.sub.5]
.498 + (0.763 - .916) = .345 MT of
[K.sub.2]O
In 1979-1980,
1.295 MT of N, .237 MT of P, and .473 MT of K
were imported
at a cost of Rs 887.9 crores with additional subsidies
of Rs 320
crores.(16) While our calculations show
the
enormous
potential of biogas slurry in meeting domestic fertilizer
needs, it
must be noted that to organize such an effort
would be a
massive task. Manure would have to be
collected from
very diffuse
points and transported to farms as needed.
Fertilizer
requirements
will increase dramatically as India's population
approaches
one billion people shortly after 2000 A.D.,
including an
increased demand for chemical fertilizers.
Organic
fertilizers
from the slurry of biogas systems could certainly
contribute to
fertilizer supply needs. Our analysis
is probably
somewhat
understated in that, as additional residues will be
available
from increased crop production, a potential increase
in cattle
population or improved cattle diet will mean more
dung.
Also, a variety of organic materials such as
water hyacinth,
forest
litter, and other under-utilized biomass could
all be
digested, increasing the fertilizer derived from biogas
slurry.
The above
discussion is intended only to illustrate the order
of magnitude
of the potential impact of large-scale utilization
of biogas
systems. Much of the data used were
aggregated from
small and
often inaccurate sample surveys, causing considerable
margins of
error. This problem will be discussed
further at the
end of this
section.
Additional
insight into the potential contribution of biogas
systems can
be obtained from recent projections of rural energy
demand.
Commercial and noncommercial energy demand,
based on
the Report of
the Working Group on Energy Policy, is shown in
Table I-3.
This data is
the basis of the Reference Level Forecast of the
study, an
extrapolation of current trends. It is
interesting to
note that the
household sector (90 percent of India's households
are in rural
areas) is assumed to account for almost all
noncommercial
fuel consumption throughout this period, except
for 50 MTCR
of firewood, agricultural residues, and bagasse
that are used
in industry. The Working Group also
suggests that
noncommercial
fuels, as a percentage of total household demand,
will
gradually decline from the current 83.9 percent to 49.7
percent, and
that the percentage of the total noncommercial
fuel demand
in all of India will drop from 43.5 percent to 11.5
percent.
Table I-3
Reference Level
Forecast
Energy Demand (1976 - 2000)
In Household and
All-India
In Millions of Tonnes of Coal
Replacement (MTCR)(17)
Commercial Fuels
MTCR (percent of
total)
1976
1983
2000
_____________
______________
______________
Household
37.4 (16.1)
51.6 (20.2)
165.5 (50.3)
All-India
252.7 (56.5)
390.2 (65.7)
1,261.3 (88.5)
Non-Commercial Fuels
MTCR (percent of total)
1976
1983
2000
_____________
______________
______________
Household
194.6 (83.9)
204.1 (79.8)
163.5 (49.7)
All-India
194.6 (43.5)
204.1 (34.3)
163.5 (11.5)
Note:
Indian coal contains 5,000 kcal/kg.
The Working
Group does not view this situation as desirable,
and offers an
Optimal Level Forecast based on a series of policy
recommendations.
This is shown in Table I-4.
For this
optimistic projection to be realized (assuming total
demand
remains the same), commercial fuels will need to be
substituted
increasingly by noncommercial fuels. By
1983, noncommercial
demand for
all-India must increase by 1.3 MTCR over
present
projections.
Table I-4
Optimal Level
Forecast(*)
Energy Demand (1982 -
2000)
For Household Sector and
All-India
In Millions of Tonnes of Coal
Replacement (MTCR)(18)
Commercial Fuels
MTCR (percent of
total)
1983
2000
_____________
______________
Households
51.6 (20.0)(*)
134.3 (41.0)(*)
All-India
388.9 (65.4)
1,017.8 (71.3)
Non-Commercial Fuels
MTCR (percent of
total)
1983
2000
_____________
______________
Households
204.1 (80.0)
194.7 (59.0)
All-India
205.4 (34.6)(*)
407.0 (28.7)(*)
(*)
Note: The author has calculated
commercial fuel demand for
households and non-commercial fuel
demand for All-India
on the assumption that the
Reference Level Forecast
total demand for each category
remains constant.
A relative increase in demand for
commercial fuels
would cause a relative decrease in
demand for non-commercial
fuels.
Conservation measures would reduce
overall demand, and thus reduce the
amount of non-commercial
fuels needed to bridge the gap
between
supply and demand.
The actual figures are not included
in the Report of
the Working Group on Energy Policy.
By the year
2000, the household noncommercial fuel demand must
increase by
31.2 MTCR, and noncommercial fuel demand in all of
India must
increase by 273.5 MTCR if commercial fuel consumption
is to remain
at the level suggested in the Optimal
Forecast
(without additional conservation).
Though these
projections can be criticized for relying on
suspect
sample data(19) or questionable assumptions,(20) The Report
of the
Working Group nonetheless shows clearly that an increase
in energy
from noncommercial, renewable resources is a high
priority.
The report specifically describes biogas
systems as
"the
most promising alternative energy technology in the household
sector,"
although it does not minimize some of the problems
associated
with the technology.(21)
The optimal
level forecast for irrigation and lighting (based
on a series
of recommended conservation measures) is shown in
Table I-5.
Table I-5
Electricity and Diesel Demand:
Irrigation and Rural Lighting
(1976 - 2000)(22)
Increase
1978
1983
2000
1978-2000
IRRIGATION
Diesel
2.6
4.6
6.6 +
4.0
(billion
liters)
Electricity
14.2
16.0
28.0
+13.8
(billions of
KWH)
HOUSEHOLD
ELECTRICITY
4.4 10.7
32.2
+21.5
(billions of
KWH)
(With
rural (3.7)
(9.6)
(29.0)
(+25.3)
households at
90 percent of
total)
________
_________
_________
__________
Total
Rural 17.9
25.6
57.0
+39.1
Electric
Demand
(billions of
KWH)
NOTE:
Electric pumps consume approximately 3,000
KWH/year/
pumpset (at about 5 HP/pumpset).
Diesel pumps consume approximately
1,000 liters (.8
tonnes) of diesel fuel/year/pumpset.
In 1978-1979,
an estimated 360,000 electric pumpsets and 2.7
million
diesel pumps were used for irrigation.
Future growth is
projected to
increase to 5.4 million electric pumpsets and 3.3
million
diesel pumps by 1983. The estimated
ultimate potential
of 15.4
million energized wells optimistically is reached by
the year
2000, when there will be 11 million electric pumpsets
and 4.4
million diesel pumps in operation.
Animal-power lifting
devices are
expected to decline from around 3.7 million in 1978
to 660,000 by
the year 2000.(23)
As shown in
Table I-5, the total increase in projected diesel
fuel demand
for irrigation between 1978-2000 is 4 billion
liters or 16
billion BHP-hrs, since .25 liters of diesel generate
1
BHP-hr. For the same period, rural
electricity demand
(irrigation
and household lighting) is expected to increase by
39.1 billion
kwh. Modified diesel engines can run on
a mixture
of 80 percent
biogas and 20 percent diesel. Since .25
liters of
diesel = 1
BHP, .05 liters can be mixed with .42 [m.sub.3] of biogas
to generate
the same power. Using a conversion
factor of 1 BHP
= .74 kwh,
.07 liters of diesel mixed with .56 [m.sub.3] of biogas
will generate
1 kwh.(24) Therefore, the 16 billion
BHP-hrs required
by the year
2000 to run diesel pumpsets could be supplied
by a little
over 6.7 billion [m.sub.3] of biogas and .8 billion
liters of
diesel fuel. Alternatively, the 39.1
billion kwh
required for
rural electricity needs could be supplied by 21.9
billion
[m.sup.3] of biogas and 2.74 billion liters of diesel fuel.
We have
previously calculated that at least 25 billion [m.sub.3] of
biogas is
potentially available from current patterns of biomass
use.
If, and it is a big "if", an
alternative cooking fuel
could be
supplied to those areas that presently rely on dung
and plant
wastes, perhaps with fuelwood plantations, this biomass
could be
shifted toward meeting a large share of increased
demand for
commercial fuels in rural areas. Since
food production
and cattle
population will have to increase to keep pace
with
population growth, the amount of available biomass, and
hence biogas,
will expand similarly. The total
increase in
rural
commercial fuel demand could be met by a mix of 28.6
billion
[m.sub.3] of biogas and 3.6 billion liters of diesel, which is
less than the
4 billion liters projected in Table I-5.
Such
a
substitution seems well within the range of technical
possibilities.
Some of the
economic aspects of substituting biogas for diesel
and
electricity are discussed in section VI.
In many villages,
the costs of
connection to the nearest central grid are prohibitive
even if the
load were increased to include lighting,
pumpsets,
etc.(25) For some areas, biogas may
represent the only
viable
technology, whether or not the gas is burned directly or
converted to
electricity. As the Working Group
notes, despite
the fact that
roughly half of India's villages are electrified,
population
increases have kept the percentage of total households
that are
electrified relatively constant at 14 percent.
Within
"electrified" villages, only 10-14 percent of the houses
obtain
electricity for household applications.
Only 5 percent
of rural
houses use electricity for lighting because rural
family
incomes cannot support the high installation cost of
electricity.(26)
As an
alternative, a benefit of a large-scale biogas program
could be to
free up the millions of tonnes of firewood that are
consumed
annually for cooking. Using the Working
Group on
Energy's norm
of 1 MT of firewood (all types) = .95 MTCR, this
represents
almost 66.8 MTCR, which is over 30 percent of the
increased
demand for noncommercial fuels, or 10 percent of the
increased
demand for commercial fuels in the optimal level
forecast for
the year 2000. While the actual use of
this vast
amount of
energy would depend on the economic, social, and
managerial
constraints associated with various thermal conversion
processes,
the possibilities for converting this energy
into
electricity, gas, or pyrolytic oil deserve serious
consideration.
Before biogas
could be used as a substitute for commercial
fuels, a
number of complex energy demand, investment, and
development
issues would need to be analyzed carefully.
Such an
analysis is
far beyond the scope of this study.
Nevertheless,
it is in
India's interest to raise these questions since there
are many
different energy supply mixes that are technically
possible,
given India's resources. The preceeding
discussion is
intended only
to show the magnitude of the potential
contribution
that biogas systems could make to India's energy
and
fertilizer needs.
A number of
technical, political, and organizational problems
must be
solved before a large-scale biogas program can be
undertaken.
The remainder of this study is devoted to
exploring
these
problems in some detail.
II.
An Overview of Biogas Systems
Most biogas
systems consist of a basic series of operations,
which is
described briefly in this chapter.
There may be certain
variations or
additions to this basic schematic design,
especially if
the system is integrated with other "biotechnologies,"
such as algae
ponds or pisciculture, or if additional
uses can be
found for carbon dioxide ([CO.sub.2]) that is present
in
biogas. A brief description of the
different aspects of a
biogas system
is necessary before discussing the economic and
social
dimensions of the technology.
RAW MATERIAL
(BIOMASS) COLLECTION
Almost any
organic, predominantly cellulosic material can be
used as a
feed material for a biogas system. In
India, the
Hindi name
for these systems, "gobar" (dung) gas plants, is
imprecise.
This is shown by the following list of
common
organic
materials that may be used in gobar gas plants:(27)
*
algae
*
animal wastes
*
crop residues
*
forest litter
*
garbage and kitchen wastes
*
grass
*
human wastes
*
paper wastes
*
seaweed
*
spent waste from sugar cane refinery
*
straw
*
water hyacinth and other aquatic weeds
Table II-1 on
the following page shows some laboratory yields
associated
with different biomass. It is important
to remember
that the
amount of gas produced from different kinds of biomass
depends on a
number of variables. The most important
of these
include the
temperature and the amount of time that the biomass
is retained
in the digester, which is called the loading rate.
Unless stated
otherwise, all biomass has been tested at 35 [degrees] C
and retained
for a 35-day period.
Despite the
obvious sanitation benefits of feeding human feces
into a biogas
digester, this practice produces a per capita
daily gas
yield of only about .025 [m.sup.3].
This means that the
excrement
from perhaps 60 people would be needed to provide
enough gas
for the cooking needs of a family of five people.
In
addition,
excessive slurry dilution can result from uncontrolled
Table II-1 Gas Yields for Selected
Organic Materials(28)
Material
Gas yield in [m.sup.3]/kg of volatile solids
cattle dung
.20
human feces
.45
banana stems
.75
water hyacinth
.79
eucalyptus leaves
.89
rinsing in a
community latrine, since all the latrine
water will
enter the digester. Corrosive hydrogen
sulfide ([H.sub.2]S)
is more
prevalent in human waste than in animal dung.
This may
adversely
affect engines run on the biogas unless the gas is
passed
through iron filings for purification.
Nevertheless, the
role of human
enteric pathogens in the communication of disease
is well
established. Therefore, latrines could
be incorporated
into a biogas
system, provided they are accepted by villagers,
affordable,
not disruptive of the digestion process, and not
harmful to
any engine operation. Safe procedures
for handling
both influent
and effluent also must be developed.
More research
is needed to
understand the effects of different combinations
of
temperatures and retention times in killing harmful
pathogens
that could remain in the digested slurry.
Water
hyacinth is particularly appealing because it is not used
as animal
fodder, and therefore does not present any "food or
fuel"
choices. In addition to its higher gas
yield, water
hyacinth
produces gas that appears to have a greater methane
content and
more soil nutrients than digested dung.
However,
there are
some drawbacks to using water hyacinth.
One is that
its water
requirements are vast. Through
transpiration from its
leaves,
hyacinth absorbs from three to seven times the amount
of water that
would normally be lost to surface evaporation
from the
water occupied by the hyacinth. Water
hyacinth also
can become a
breeding ground for mosquitoes and snails, although
these can be
controlled by introducing predator fish.(29)
There are
certain annoyances associated with the use of this
and other
plant materials. Younger plants yield
more gas than
older plants,
which may necessitate greater discrimination in
the manner in
which biomass is collected. Plants may
have to be
dried and
shredded to ensure proper mixing, dilution, and
digestion.
It may often be necessary to add urine to
maintain a
proper carbon
to nitrogen (C/N) ratio. There have
been many
field reports
of scum build-up, clogged inlet tanks, and toxicity
to
methanogenic bacteria (due to the "shock" caused by the
introduction
of different biomass materials).
However, these
reports are
sketchy, and the problems could be due to improper
digester
design or operation. Water hyacinth is
almost always
mixed with
dung; there is little reliable field experience
using water
hyacinth as the sole input, although this has
been done
successfully in laboratories, as will be discussed
shortly.
Several
Indian research groups have been experimenting with
"bio-dung"--a
fuel cake and/or biogas feed material made from
dried and
partially composted organic matter of varying combinations.(30)
Excellent gas
yields have been reported with this
still
experimental idea, but documentation is insufficient.
Nonetheless,
this practice of "partial digestion" of the
biomass in
plastic bags seems similar to the 10-day "predigestion"
period
observed in China, where organic material is composted
prior to batch
loading in family digesters.(31) The
Chinese
report faster gas production if material is partially
digested.
The process probably reduces the [CO.sub.2]
present in the
early phases
of digestion by simply releasing it in the
atmosphere as
the gas percolates up through the compost pits.
There are
many advantages claimed by proponents of "bio-dung,"
such as its
greater gas yield, higher calorific value, potential
for
generating revenue as a saleable product, eradication
of harmful
weeds, and making family-scale digesters affordable
to those who
own fewer than three to four cattle.
There is
little
evidence currently available to evaluate these
possibilities.
MIXING AND
FEEDING RAW MATERIAL INTO THE DIGESTER
There has
been a good deal of experimentation with the digestion
of organic
materials in various combinations.
Regardless
of the
biomass used, it must be loaded without being diluted
excessively
with water. Most researchers mix fresh
dung and/or
sun-dried
organic matter with water at roughly a 1:1 ratio.
If
the plant
matter is still green or the cattle diet is rich in
straw, the
ratio should be changed slightly to about 1:0.8.
Materials
should have a C/N ratio of roughly 30:1 due to the
digestive
requirements of methanogenic bacteria.
The relative
proportions
of different material should be adjusted to
maintain this
ratio.(32)
The inlet
tank can become clogged when assorted feeds of different
sizes and
composition materials are mixed.
Fibrous
material can
be shredded to avoid this. Different digester
designs,
incorporating larger inlets, may alleviate this problem
Most Indian
systems work best if the biomass and water are
mixed
thoroughly in the inlet tank prior to injection into the
digester.
Many of these inlet tanks have a removable
plug to
block the
inlet pipe during mixing.
Alternatively, the Chinese
seem to use
less water and spend less time mixing material.
This is
perhaps due to their batch feeding process, which
eliminates
the need to add slurry daily.(33)
DIGESTION(34)
Anaerobic
digestion consists broadly of three phases:
1.
Enzymatic hydrolysis--where the fats,
starches, and proteins
contained in cellulosic biomass are broken
down into simple
compounds.
2.
Acid formation--where acid-forming bacteria
break down
simple compounds into acetic acids and
volatile solids.
3.
Methane formation--where methanogenic
bacteria digest these
acids and solids and give off [CH.sub.4],
[CO.sub.2], and traces of [H.sub.2]S.
Any remaining
indigestible matter is found in either the
"supernatant"
(the spent liquids from the original slurry) or
the
"sludge" (the heavier spent solids).
These two products are
often
described as "slurry" because the influent in most Indian
plants is
diluted with water at about a 1:1 ratio to form a
relatively
homogenous, liquid-like mixture. In
China, the
supernatant
and sludge generally settle into separate layers in
either the
digester itself or in the output tank, and are
removed
separately by buckets that are lowered to different
depths.
During the
first phase of digestion, a great deal Of [CO.sub.2] is
produced and
pH drops off to roughly 6.2 (pH values of less
than 6.2 are
toxic to the bacteria needed for digestion).
After
about ten
days, pH begins to rise, stabilizing at between 7-8.
Temperatures
below 15 [degrees] C (60 [degrees] F) significantly reduce gas production.
During the
winter months, many family-scale biogas systems
in northern
India reportedly produce only 20-40 percent of
their summer
yields. Similarly, Chinese plants often
produce
almost no gas
during winter, and more than half the annual
energy
required for cooking must be provided by burning crop
residues
directly. However, the need for a
backup source of
energy to
supplement a biogas system can probably be eliminated
with some of
the design modifications suggested in the next
section.
Higher temperatures generally increase gas
production,
reduce
retention time, and increase loading rates, once the
bacteria
adjust to the warmer environment.
Mesophilic bacteria
favor temperatures
near 35 [degrees] C (95 [degrees] F).
Thermophilic bacterial
strains are
found in the 50-60 [degrees] C (122-140 [degrees] F) range.
The
addition of
nitrogen-rich urine seems to aid in gas production
during
winter, especially when it is combined with plant
wastes.
Digesting the wet straw flooring from cattle
sheds, if
available, is
a convenient way to add urine to the influent.
The microbial
population of methanogenic bacteria will decrease
as slurry
flows out from the digester. These
bacteria have a
doubling rate
of roughly 40 hours. However, this slow
growth
rate can be
overcome by greatly increasing the microbial population.
There has
been informal discussion among experts about
a process,
reportedly developed in Belgium, that uses a membrane
to retain the
methanogenic bacteria inside the digester.
Gas yield per
kg of biomass reportedly increases by a factor of
5-10 when the
membrane is used. If these claims can
be documented,
and if the
membrane is both affordable and durable, it
would be an
important development. There also is
sketchy
evidence that
methanogenic bacteria are pressure sensitive.
This might be
a problem in some fixed dome systems, which can
generate
pressure above a water column of 80-90 cm.
More
research is
needed on this point.
The effect of
animal diet on gas yield has received far less
attention
than it deserves. Cattle can be either
well fed or
near
starvation, depending on the income of a farmer and the
time of
year. Farmers often barely maintain
their cattle until
just prior to
plowing season, when the diet is increased to
fatten the
cattle for work. Obviously, the less an
animal eats,
the less dung
it produces. The more cellulose,
especially in
fibrous
materials, that it eats, the greater the gas yield will
be.
More research is needed to determine the
optimal diet for
cattle given
their use as a source of milk, motive power, and
combustible
energy (biogas), and also considering local resources,
available
capital, and knowledge constraints.(35)
Even
without this
research, however, it is clear that diet, grazing
habits, and
costs of collection will greatly affect the net
available
dung yield per animal.
Many
statistics quoted in the literature simply may not apply
to a
particular locale. These include data on
dung yield of
animals, gas
yield of dung, temperature, the nature and nutrient
content of
other materials digested, and the [CH.sub.4] content,
which can
vary 50-70 percent for a given quantity of biogas,
depending on
diet. Inaccuracies usually manifest
themselves in
an
overestimation of gas availability and overall benefits.
Norms
mentioned in numerous studies are useful guides to these
questions but
cannot replace micro-analysis.
A great deal
of research is furthering our understanding of the
microbiological
aspects of biogas systems.(36) If gas
yield could
be increased
and retention time reduced, production costs would
decrease,
since a smaller volume of biomass per cubic meter of
gas would be
required. Some of the areas or research
include
ways to
increase the growth rate of methanogenic bacteria,
improve the
digestibility of lignin, develop microbiological.
innoculins
that would increase gas production, develop bacterial
strains that
are less sensitive to cold weather, identify
micro-organisms
involved in digestion, and separate acid-forming
and
methanogenic bacteria. As of the
writing of this
study, there
have been no major documented performance breakthroughs
achieved as a
result of this research.
III.
Digester Designs
There are
many ways to design biogas systems. The
designs
discussed in
this study are by no means the only possibilities.
They either
have been tested extensively or were in the midst
of serious
research and development during the writing of this
study.
Groups attempting to develop their own
systems should
use the
illustrations in this section only as guides.
The
characteristics
and costs of labor, construction materials,
land, etc.,
will vary according to local conditions and the end
uses of the
system's gas and slurry.
The Khadi and
Village Industries Commission (KVIC) design has
been
developed over the past 15 years and is similar to the
53p18.gif (600x600)
majority of
systems currently operating in India (see Figure III-1).(37)
As of 1981,
KVIC claims to have built about 80,000 of
these
systems, although there are no reliable data on how many
of the units
are actually operating, temporarily shut down, or
nonfunctioning.
The KVIC system consists of a deep well and
a
floating drum
that usually is made of mild steel. The
system
collects the
gas and keeps it at a relatively constant pressure.
As more gas
is produced, the drum gas holder rises.
As
the gas is
consumed, the drum falls. Actual
dimensions and
weight of the
drum are functions of energy requirements.
A long
distribution
pipeline that might necessitate greater pressure
to push gas
through its length would require a heavier drum,
perhaps
weighted with concrete or rocks.
Biomass slurry moves
through the
digester because the greater height of the inlet
tank creates
more hydrostatic pressure than the lower height of
the outlet
tank. A partition wall in the tank
prevents fresh
material from
"short circuiting" the digestion process by displacement
as it is
poured into the inlet tank. Only
material
that has been
thoroughly digested can flow up and over the
partition
wall into the outlet tank.
Most KVIC
systems are designed to retain each daily charge for
50 days,
although this has been reduced to 35 days in newer
units.
The slurry should be agitated slightly to
prevent any
chance of
stratification. This is accomplished by
daily rotation
of the drum
about its guide post for about 10 minutes.
In
Nepal, some
gas holders have been painted to look like prayer
wheels.
They are turned during frequent religious
ceremonies,
or
"puja" (individual prayer).
The Nepali group, Development
and
Consulting Services (DCS), Butwal, also has modified the
KVIC gas pipe
connection. It has attached an
underground fixed
pipe to the
guidepost, feeding gas through the guidepipe rather
than connnecting
a flexible hose to the roof of the gas holder.
53p19.gif (600x600)
DCS uses a
taper design for high water table areas (see Figure III-2)
and a
straight design for low water table areas (see
Figure
III-3).
53p20.gif (600x600)
KVIC systems
are reliable if properly maintained, although drum
corrosion has
historically been a major problem. It
appears
that the
quality of steel manufactured in India may have
declined
during the early 1960s. There are
anecdotes of
unpainted
systems built before then that are still functioning.
Drums should
be coated once a year with a rustproof bitumin
paint.
Oil can also be introduced into the top of
the digester
slurry,
effectively coating the steel drum as it rises and
falls.
KVIC designs
of over 100 [m.sup.3] have been constructed for institutions
such as
schools, dairies, and prisons. Though
construction
economies of
scale exist for all digesters, the use of
mild steel
accounts for 40 percent of the system cost.
KVIC
systems are
relatively expensive. The smallest
family KVIC system
costs well
over Rs 4,000 (US$500) to install. KVIC
has experimented
with a number
of materials, including plastics, for
dome
construction. The Structural
Engineering Research Center,
Rourkee, has
done work with ferrocement, reducing costs somewhat.
Ferrocement
gas holders become extremely heavy as their
scale
increases, and they require proper curing and a fair
amount of
manufacturing skill. The curing process
requires that
domes be
either submerged in water for 14 days or else wrapped
in
water-soaked cloth or jute sacks for 28 days.
This raises
questions
about their use, or at least their fabrication, in
many
villages. KVIC would like to
prefabricate both gas holders
and digester
sections at regional centers and then transport
these out to
villages. This would create rural
industry and
employment,
and introduce quality control into the manufacturing
process.
Dr. A.K.N.
Reddy and his colleagues at the Cell for the Application
of Science
and Technology to Rural Areas (ASTRA), and
the Indian
Institute of Science, Bangalore, have modified the
KVIC design
in several important ways. The result
is a shallower,
broader
digester than the KVIC design. Table
III-1 shows
some
statistical comparisons between the two designs.(38)
ASTRA also
examined the retention time for a charge of biomass,
given
Bangalore climatic conditions, and reduced the 50-day
retention
period suggested by KVIC to 35 days. It
observed that
since almost
80 percent of the total amount of gas produced was
generated
within the shorter time, the increase in digester
capacity
necessary to more completely digest slurry did not
seem
justified. Further research on cutting
down retention time
as a way to
reduce system costs may suggest other design modifications.
The shorter
the retention period, the less digester
volume (and
hence, lower cost of construction) is required for
the storage
of the same volume of organic material.
As shown in
Table III-I,
the ASTRA unit, though almost 40 percent cheaper
than the KVIC
unit, had a 14 percent increase in gas yield.
Its
improved
performance needs to be monitored over time.(39)
Table III-1
Comparison of KVIC and
ASTRA designs
for similar Biogas
Plants(40)
KVIC
ASTRA
Rated daily
gas output 5.66
5.66
Gas holder
diameter (m) 1.83
2.44
Gas holder
height (m) 1.22
0.61
Gas holder
volume ([m.sup.3])
3.21
2.85
Digester
diameter (m) 1.98
2.59
Digester
depth (m) 4.88
2.44
Digester
depth-diameter ratio 2.46
0.94
Digester
volume ([m.sup.3]) 15.02
12.85
Capital cost
of plant (Rs) 8,100.00
4,765.00
Relative
costs 100.00
58.80
Daily loading
(kg fresh dung) 150.00
150.00
Mean
temperature (Celsius) 27.60
27.60
Daily gas
yield ([m.sup.3]/day) 4.28 [+ or -]
0.47 4.39[+ or -] 0.60
Actual
capacity/rated capacity
75.6% 86.4%
Gas yield
(cm/g fresh dung) 28.5 [+ or -]
3.2 32.7 [+ or -] 4.0
Improvement
in gas yield
--
+14.2%
The ASTRA
group conducted a series of tests on existing biogas
systems and
found that there was uniform slurry temperature and
density
throughout the digester,(41) and that the heat lost in
biogas
systems occurs mainly through the gas holder roof.
It
also found
that when the colder-temperature water was mixed
with dung to
make slurry, the charge shocked the indigenous
bacteria and
retarded gas production. The result was
a 40
percent or
more reduction in gas yield.(42)
An important
goal thus was to control the temperature of the
slurry.
This raised a number of problems:
maintaining the
slurry
temperature at the 35 [degrees] C (95 [degrees] F) optimum; heating the
daily charge
to minimize temperature loss due to colder ambient
temperatures;
and providing insulation for the floating drum
gas
holder. ASTRA found an ingenious
solution to all these
needs.
It installed a transparent tent-like solar
collector on
53p23.gif (600x600)
top of an
ASTRA floating drum gas holder (see Figure III-4).(43)
This was done
by modifying the drum design so that its side
walls
extended up beyond the holder roof, forming a container
in which to
place water. This water was drawn from
the
collector,
heated by the sun, and mixed with the daily charge
of dung.
Preliminary data from the 1979 Bangalore
rainy season
showed an
increase in gas yield of about 11 percent with this
solar heating
system. During this often cloudy
period, the
temperature
of the water in the collector was only 45 [degrees] C (112 [degrees] F)
compared with
the 60 [degrees] C (140 [degrees] F) temperature recorded during the
summer
months. More work is needed to improve
the cost and performance
of this solar
heating method, but its potential for
reducing
system costs seems promising, especially on a village
scale.
In addition, distilled water can be obtained
by collecting
the
condensate as it runs down the inclined collector roof.
The ASTRA
group is constructing a 42.5 [m.sup.3] biogas system in Pura
village,
Tumkur District, near Bangalore, that eventually will
incorporate
ferrocement gas holders and solar heating systems,
enabling the
group to evaluate its ideas in an actual village
context.
Dr. C. Gupta, Director of the TATA Energy
Research
Center,
Pondicherry, is constructing an ASTRA design biogas
system with a
community latrine in Ladakh, Jammu and Kashmir
State, where
the 3,600-meter altitude and chilly winter
temperatures
will provide valuable data on the performance of
this
design. Most recently, ASTRA has
reportedly constructed a
2.3 [m.sup.3]
fixed dome plant for Rs 900 (US$112).
It may be possible
to reduce
this cost further by experimenting with a compacted
earth pit
that would be covered by a brick dome.
The costs of
constructing
the brick digester would thereby be eliminated.
Such
experiments are still quite recent and the data on performance
and
durability are not yet available. Parts
of
Karnataka
have large, brick-producing activities, and the easy
availability
of inexpensive bricks may account partially for
this low
cost. Nevertheless, the potential
exists for large
reductions in
system costs, which could alter dramatically the
economics of
biogas systems.
The Planning
Research and Action Division (PRAD) of the State
Planning
Institute, Lucknow, has been conducting biogas research
at its Gobar
Gas Experimental Station, Ajitmal (near
Etawah),
Uttar Pradesh, for more than 20 years.
PRAD constructed
the 80
[m.sup.3] community system in the village of Fateh Singh-Ka-Purva,
which will be
discussed later in this study. After
several
years of
experimentation with designs modified from the
fixed dome
systems popular in the People's Republic of China,
PRAD
developed the "Janata" fixed-dome plant.(44)
The PRAD
design has several advantages. A Janata
plant system
can be built
for about two-thirds the cost of a KVIC system of
similar
capacity, depending on local conditions, prices, and
the
availability of construction materials.
The magnitude of
savings due
to the all-brick Janata design may diminish with
increased
capacity, but there is little data regarding large
fixed-dome
plants. One of the key features of the
Janata and
other
fixed-dome designs is that inlet and outlet tank volumes
are
calculated to ensure minimum and maximum gas pressures due
to the
volumes displaced by the changing volumes of both gas
and slurry
inside the system.
Janata
designs are relatively easy to construct and maintain
because they
have no moving parts and because corrosion is not
a
problem. One drawback is that Janata
plants may require periodic
cleaning due
to scum build-up. As gas pressure
increases
in a fixed
volume, the pressure pushes some of the slurry out
of the
digester and back into both the inlet and outlet tanks,
causing the
slurry level in each tank to rise. As
gas is consumed,
the slurry
level in the tanks drops and slurry flows
53p250.gif (600x600)
back into the
digester itself (See Figures III-5a through III-5d).
Such movement
probably acts as helpful agitation, but
the motion
may also cause heavier material to settle on the
bottom of the
digester. The result then is that only
the supernatant
flows through
the system. Such buildup has been
reported
occasionally,
and may result in a gradual accumulation of
sludge that
could cause clogging.
The more
serious problem is posed by the heterogeneous nature
of even the
most well-mixed influent. Lighter
material can form
a layer of
scum that remains unbroken precisely because the
plants are
designed to prevent the slurry level from descending
below the top
of the inlet and outlet tank openings in the
digester, which
might allow gas to escape through the tanks.
This problem
of scum build-up may be more serious in large-scale
plants, and
may require the installation of stirring
devices.
The digester
must be cleaned if build-up does occur.
Someone
must descend
into the unit through the outlet tank and scrape
out the
sludge. The Janata plant has no sealed
manhole cover in
the
dome. This differs from Chinese plants,
for which sludge
removal is
assumed to be a regular part of normal operation.
With the
Janata plant, extreme caution must be used when entering
the digester
since concentrated [CH.sub.4] is highly toxic and
potentially
explosive. The Chinese often test this
by lowering
a caged bird
or small animal into an emptied digester, exposing
it to the
gases for some time, and then descending only if the
animal lives.
More research
is needed on the kinetics and fluid dynamics of
fixed-dome
plants. The ASTRA observation of
homogeneous slurry
density in
the KVIC unit would seem to conflict with some field
reports,
although poor maintenance and lack of thorough mixing
may account
for such discrepancies.
An important
advantage of Janata plants is that their required
construction
materials are usually available locally.
Lime and
mortar can
substitute for concrete. Neither steel
(which often
is scarce)
nor ferrocement are needed, which reduces dependence
on often
unreliable outside manufacturing firms and suppliers.
The dome of
the Janata plant does require a good deal of
skilled
masonry, including several layers of plastering, to
ensure a
leak-proof surface. Many early plants
leaked badly.
PRAD reports
this is no longer a problem due to extensive
construction
experience and the fact than it has trained many
local masons
in Uttar Pradesh who can competently construct
such units.
Although PRAD
recommends constructing a raised platform to
support the
earthen mound that serves as the form for the construction
of the brick
dome, the Chinese build brick domes with
little or no
support scaffolding. It is difficult to
learn this
technique
unless one visits a construction team in China.
The
few manuals
that exist are inadequate in explaining the construction
method, often
omitting details such as the angle at
which bricks
should be laid to form the correct arc for the
dome, or the
number of rings required for bricks of unknown
dimensions.
Using some
PRAD diagrams and A Chinese Biogas Manual, translated
by the
Intermediate Technology Development Group (London,
1980), the
author directed the construction of a modified 2 [m.sup.3]
Janata plant
to be used as an experimental digester at the
Indian
Institute of Technology, Madras. A
free-standing dome
was
successfully constructed, but the process took three days
and required
vigilant monitoring of cracks that occasionally
began to
spread around different areas of the brick rings that
formed the
dome. The safety of masons working
under the emerging
dome was
cause for some concern. The weight of
the partially
formed arc
sections easily could have proven fatal if someone
had been
caught underneath a collapsing section.
It also
was difficult
to set the bricks at a proper angle.
The dome
emerged
somewhat misshapen, despite the use of a two-pole system
in which one
pole defined the vertical axis and the other,
equal to the
radius of a sphere formed by "extending" the dome,
pivoted about
a nail. By rotating the vertical pole
360 [degrees] and
lining up
each brick ring with the angle formed by pivoting the
"radius"
pole between 45 [degrees] and 135 [degrees] (off the horizontal), the
correct dome
arc, and hence each brick's proper angle, should
have been
readily apparent. However, due to the
irregular surface
of the
bricks, the varying amounts of concrete applied to
the bricks,
and the reluctance of the masons, for whatever
reason, to
use the device frequently, the dome construction
became a
matter of educated guesswork.
Given the
short time many of the Janata systems have been
operating,
the possibility still exists that micro-cracks may
develop in
the dome over several years. The Center
for Science
for Villages,
Wardha, has covered the top of its fixed-dome
plants with
water so that any leaks will be visible as bubbles.
This idea
could be further modified to incorporate an ASTRA
type solar
collector to produce warm water for hot charging.
However, one
of the additional advantages of the fixed-dome
designs is
that they are largely underground. This
frees the
surface land
area for alternative use. Improved
system performance
due to solar
heating must be evaluated against other
possible uses
of the land.
Fixed-dome
plants release stored gas at pressures as high as 90
cm (36")
of water column. As gas is consumed,
and in spite of
the changing
slurry level, pressures do drop. The
amount of gas
inside the
dome at any time can be estimated crudely by measuring
changes in
the slurry level in the inlet and outlet tank
(as long as
the daily charge has settled in the digester).
There is some
concern that flame temperatures drop with lower
pressures,
increasing cooking time and gas consumption.
However,
there seems
to be little complaint from individual users
on this
point. Minimizing gas consumption
during cooking can be
of great
importance in a village system that requires gas for
uses other
than cooking. There are few data on the
economic and
thermodynamic
efficiencies of diesel or petrol engines or of
generators
powered by a fixed-dome system.
Presumably, more
diesel would
be consumed as pressure drops. Gas
pressure regulators
have been
discussed periodically as a way to alleviate
this
problem. Regulators can ensure that
enough pressure is
maintained
throughout a distribution system, and that occasional
high pressure
will not blow out valves or pipe joints.
Work
is now under
way in Sri Lanka near the University of Peredeniya,
in Uttar
Pradesh, and in Bihar on fixed-dome plants as
large as 50
[m.sup.3]. Plants of this size have
been reported in
China, but
little information is available to confirm this.
It
remains to be
seen if cost reductions observed in small-scale,
fixed-dome plants
will be repeated or even improved with increased
scale.
Constructing large domes from bricks, or
even
from
ferrocement, may prove difficult and/or expensive since
their
performance and durability remain a matter of speculation.
Variations on
the fixed-dome design have been reported in
Taiwan, where
heavy gauge collapsible Hypalon/Neoprene bags
have been
used as digesters.(45) The Sri A.M.M. Murrugappa
Chettiar
Research Center (MCRC), Madras, has developed a brick
digester with
a high-density polyethelene gas holder supported
53p30.gif (600x600)
by a geodesic
frame (see Figure III-6). The frame is
bolted to
the digester
walls, and the plastic gas holder is retained by a
water
seal. The MCRC plant is still being
tested in several
Tamil
villages and few performance data are available.
The
plant is less
expensive than the PRAD Janata design and has the
advantage of
being easily and quickly installed.
However, major
questions
remain concerning this design's durability and safety.
Only
small-scale systems have been constructed, although
larger
systems are planned.(46)
Development
and Consulting Services (DCS) of the Butwal Technical
Institute,
Butwal, Nepal, has begun field testing a horizontal
plug-flow
digester design based on the work of Dr.
William
Jewell of Cornell University (USA). A
long, shallow,
horizontal
system night require less water, be less susceptible
to scum
formation and clogging, and foster greater gas production.
A plug-flow
system should be easier to clean, and would
require less
excavation, helping to reduce costs.
This system
has great
promise; a prototype should be developed within a
year.(47)
The Jyoti
Solar Energy Institute, Vallabh Vidynagar, Gujarat
(near Anand),
has done some interesting design work in conjunction
with the
research on agricultural residues discussed
earlier.
JSEI researchers found that a scum layer was
forming
in
experimental digesters that were fed with banana stems,
water
hyacinth, and eucalyptus leaves. This
layer gradually
reduced gas
production to almost zero. The researchers
concluded
that the scum
layer formed because the fresh biomass contained
a good deal
of oxygen between its cell walls. Since
the
shredded
sections were lighter than the water they displaced,
the biomass
tended to float to the surface of the slurry.
During
experimental
batch feeding, this scum layer was observed to
sink
gradually to the digester floor as digestion progressed.
The scum
layer that has troubled many of the digesters used for
agricultural
residues seems to form when fresh biomass, entering
at the bottom
of the digester, pushes up against heavier,
older biomass
that is settling toward the digester floor.
The
lighter
biomass causes the heavier layer to rise, creating the
thick scum
layer. JSEI engineers devised an
ingenious system of
loading fresh
biomass through the top of the gas holder to the
surface of
the slurry by means of a plunger arrangement (see
53p31.gif (600x600)
Figure
III-7). This ensures that the heavier,
partially digested
material
settles to the digester floor unimpeded by the
lighter biomass.
The JSEI innovation could be an important
breakthrough
in the use of agricultural and forest residues in
biogas
systems. In addition to solving the
problem of scum
build-up, the
JSEI technique also seems to eliminate the
necessity of
excessive shredding or drying of residues, making
the handling
of these materials far less cumbersome and time-consuming.
Biomass is
merely chopped into 2-3 cm (.75-1.25")
squares and
then is pushed into the digester through a cylindrical
tube inserted
into the floating gas holder. The tube
is
always in
contact with the slurry, even with the dome at
maximum
height, so that no gas can escape.
There remain
a number of questions concerning the relative performance
of fixed-dome
plants versus floating drum plants.
Conflicting
data have been reported concerning equipment life,
material
durability, gas production, delivered gas pressure,
and
installation and maintenance costs. The
Department of
Science and
Technology has established five regional testing
centers where
different designs of similar capacity are being
monitored
under symmetrical, controlled conditions in different
agro-climatic
regions. One such station visited by
the author,
in
Gandhigram, Tamil Nadu, appears to have insufficient
resources to
assess accurately the performance of the different
biogas
systems that have been constructed.
More rigorous comparative
research on
fixed-dome plants is needed, especially
after further
design improvements, such as those done by ASTRA,
are
completed. The effects of agitation,
digester wall protrusions,
and partition
walls to improve gas yield need to be
analyzed in
different digester designs. It is not
yet clear if
the cost
advantages of fixed-dome digesters outweigh the performance
advantages of
floating-drum digesters. This may be a
function of
the uses of the gas in a particular village, which
determines
the relative importance of providing gas at a
constant
pressure and the effectiveness and cost of pressure
regulators
currently under development. More
research is needed
before any
conclusions can be made.
There are
numerous experimental digesters with modifications of
the designs
described in the preceeding discussion.
MCRC is
planning to
link its biogas plants with other biotechnology
projects,
such as pisciculture, algae growth, and organic
farming.
The Indian Institute of Technology - Delhi
Center for
Rural
Development and Appropriate Technology is developing a
system that
will grow algae in the supernatant of a fixed-dome
system.
It will recycle the algae to supplement the
daily raw
material
charge. The system will provide
fertilizer, gas,
oxygenated
water for irrigation, and animal nutrients such as
single cell
proteins for fodder.(48) The idea is to
generate the
maximum yield
per unit of local resources. Integrated
systems
have a great
deal of potential, although their often elegant
simplicity
requires a great deal of skilled operation and
effective
maintenance.
IV.
System Operation
The
appropriate role of a biogas system in producing heat,
light,
refrigeration, and motive power can be determined after
end-use
energy requirements over time have been assessed carefully,
including any
anticipated demand from population growth.
The system's
capacity should be based on a careful analysis of
costs, local
climate and soil conditions, and the net availability
of
biomass. This latter consideration must
account for
competing
uses of crop wastes and dung, animal diet, grazing
habits,
difficulty of biomass collection, and the availability
of
labor. Also, the probabilities of the
survey data remaining
constant over
time must be assessed.
Many
family-sized systems have been designed with insufficient
capacity to
produce gas when it is needed at different times
during the
day or year. In India's colder northern
climates,
the drop in
gas production during winter often has been underestimated.
Great care
should be exercised in preparing plant
feasibility
studies so that different contingencies can be
accommodated
without disrupting the operation of the system.
For example,
farmers often sell cattle during droughts (if the
cattle
survive), and this obviously reduces dung availability.
Baseline
surveys of available biomass can be distorted if conducted
during
periods of exceptionally good harvests or failed
monsoons.
It probably
is wise to build two or more medium-size plants in
a village
rather than one large plant, even though the total
cost may
increase. If problems or maintenance
force a temporary
shutdown in
one of the digesters, the entire system will not be
disrupted.
If small-scale, fixed-dome system costs call
be reduced
to around Rs
400-500 (US$50-62), which does not seem
impossible,
clusters of small systems might be a more cost-effective
way to
provide energy than one large system.
Some of
the
complexities of planning village energy systems are discussed
in the
following section on the economic analysis of
biogas
systems.(49)
Biogas plants
require certain care during their initial starting
up or
"charging." If a digester
contains a partition wall,
slurry must
be added from both the inlet and outlet tanks to
This chapter
presents certain points that are not usually
covered in
discussions about biogas systems. The
author recommends
John Finlay's
Operation and Maintenance of Gobar Gas
Plants[N]
(1978) for a more complete description of how biogas
systems
operate.
equalize
pressure and prevent collapse of the wall.
While not
essential,
introducing either composted manure or digested
slurry as
seed material to the digester will speed up the
initial
charging. There is some disagreement
over how best to
start up a
plant. One suggestion is to fill the
digester as
rapidly as
possible until the outlet tank begins to overflow,(50)
ensuring that
the seed material is twice the volume of the
fresh biomass
initially fed into the system. Another
is to
increase
gradually over a three-week period the amount of biomass
mass
introduced daily to the system.(51) The
inlet and outlet
tanks are
then covered and digestion begins.
The plant
should begin producing gas within 7-20 days, depending
on
temperature, agitation, etc. This
initial gas is largely
[CO.sub.2]
and should be released into the atmosphere; it will burn
poorly, if at
all. This step may have to be
repeated. Within a
month after charging,
however, the system usually will have
developed a
kind of critical mass of bacteria that is stable
enough to
digest the daily biomass charge and produce gas.
Care should
be taken to ensure that the biomass fed into the
system is
relatively free from sand, gravel, and coarse fibers.
Many inlet
tanks have a floor that slopes away from the opening
through which
material flows into the digester. The
opening is
blocked
during slurry mixing and the slurry is allowed to
settle for
several minutes. The plug is then
removed and, as
the slurry
drains into the digester, heavier sediments and foreign
matter
collect at the lower end of the sloped inlet tank
floor.
This material can be removed after the
slurry has
drained into
the digester. Material should be mixed
thoroughly.
Shredders,
screens, and mixing devices may be required for
village scale
systems that handle a large amount of different
raw
materials. These precautions are
recommended to reduce the
chances of
the digester becoming clogged in either the inlet or
outlet tanks,
or of having a scum layer form in the digester
itself.
More research is needed to understand the
sensitivity
of biogas
systems to variations in the biomass charge.
Similarly,
ideal rates
of loading different materials at different
temperatures
need to be determined. Many of the
guidelines for
operating
biogas systems are based on trial and error observation
in the
field. The systems work, but their
efficiency could
be increased
and their costs reduced.
Systems
should be built in a sunny area to take advantage of
solar
radiation. They should be at least 5-10
meters from a
source of
drinking water sources, especially if human wastes
are
used. This is particularly important
with large-scale systems,
which could
represent concentrated sources of enteric
(intestinal)
pathogens if they leak. Adequate space
should be
provided for
raw material and water-mixing as well as for
slurry
handling and storage. Land and water
requirements are a
critical and
often underemphasized part of a biogas system.
Care must be
taken to minimize water condensation in the gas
lines
(possibly by including water traps), isolate sparks and
flames from
the gas lines (by including flame traps), and prevent
pipe freezing
in winter. Provision must be made for
frequent
inspection
and maintenance of the system (including pipelines).
There also
must be proper handling of the slurry to
conserve
nutrients and minimize contact with pathogens in both
the influent
and effluent.
If a biogas
system is not performing as it should, the following
trouble-shooting
sequence is suggested.(52)
1.
Check temperature of the influent
mixture. Sudden cooling of
the slurry in the digester can impede
microbiological digestion.
Temperature variations should be kept to a
minimum.
2.
Check loading rate of organic
materials. Overloading will
cause material to flow out of the digester
before the slurry
has been digested.
3.
Check pH levels, which may drop below the
6.0-7.0 minimum.
Add lime to increase the pH level, if
necessary.
4.
Check for toxic material in the influent,
and alter the composition
of materials - mixed in the slurry.
Whenever
daily feeding procedures are altered, the change
should be
introduced gradually so that the microbial population
has time to
adjust to the new environment.
V.
Gas Distribution and Use
Gas
distribution systems can cost from several hundred rupees
for a family
system to as much as three/fourths the total cost
of a village
scale digester (exclusive of pumpsets, engines,
generators,
etc.). Distribution costs can offset
the scale
economies of
larger digesters. The distribution
system in a
particular
village will be determined by local conditions,
e.g., the
distance between the points to which the gas must be
distributed
(houses, pumpsets, or industries), the availability
of organic
material, the difficulty of collection, and the
availability
and cost of construction materials.
Because the
gas is usually released from a floating drum holder
at a pressure
of less than 20 cm of water column, the total
length of the
distribution pipeline is probably limited to less
than 2
kilometers unless booster pumps are used, which increases
costs.
As delivery pressure decreases with pipeline
distance, the
flame velocity gradually becomes too low to support
a stable
flame. Similarly, pumpsets for biogas
that are
too far from
the digester will require either an expensive
pipeline, a
gas storage vessel/bag of some sort, or possible
conversion of
the biogas to electricity.
Many
different materials have been used in constructing pipelines,
such as GI
pipe and PVC or HDP plastics. It would
seem
possible to
use clay or earthen pipe as well.
Problems of gas
leaks,
durability, and rodent damage vary with material characteristics
and care in
construction. Generally, plastic pipes
with a
diameter greater than 35 mm seem best for cost optimization,
ease of
construction, and favorable friction characteristics
to aid in gas
flow.(53) The availability of large
quantities
of plastic
piping may be a problem in certain locales.
One way to
reduce the cost of pipelines might be to use the
same pipeline
for delivering drinking or irrigation water as
well as
gas.(54) Water condensation in the
pipeline would have to
be monitored
carefully, as would any possible health hazards.
There are
several descriptive accounts from China and Sri Lanka
of using bags
to store and transport gas to run pumpsets and
tractors, and
possibly to meet household cooking and lighting
needs.(55)
Kirloskar Oil Engines, Limited, is
experimenting with
a
rayon-coated rubber bag that has enough capacity to power a
5 hp pumpset
for two hours. It would cost
approximately Rs 500
(US$40).
The general problem with such bags is that
they must
be large
enough to enable the gas to be released at the
10-12 cm
water column pressure that is required for stove or
engine
use. Unless compressed in some way, a
bag to provide
enough gas
for the daily cooking and gas requirements for a
single family
would have to be almost as big as the hut to
which it was
attached. In addition, the safety and
durability
of such a
system are debatable, given the rigors of village use
and the
susceptability of such a system to vandalism.
Despite
the presence
of [CO.sub.2] in biogas, puncturing a bag in the vicinity
of a flame
could cause a large fire. The danger is
magnified if
the gas is
purified by bubbling it through time to increase its
calorific
value.
Nonetheless,
a centralized delivery scheme where a few "regional"
pipelines are
laid near clusters of huts, and from which
individual
consumers fill their own storage bags, might have
certain
advantages. It may ultimately be
cheaper than a full-scale
pipeline
system. It could expand easily if
demand increased,
and would
free families from being restricted to using
gas only
during certain times of the day. Most
community systems
have several
uses for gas and deliver gas only during
fixed times
of peak demand, especially during morning and
evening
cooking periods. This staggered delivery
is designed to
minimize gas
waste, but can be inconvenient for villagers, who
occasionally
have to work during the time gas is delivered in
their
area.(56) A decentralized "gas
bag" system might facilitate
plant
management and the easy monitoring of gas consumption.
It
might also
allow for more efficient use of the gas.
There are
problems with
this concept, but it has not yet received adequate
attention
from biogas system designers.
The costs of
pressurized biogas cylinders, similar to Liquid
Propane Gas
(LPG), seem prohibitive. Biogas can
only be liquified
at -83
[degrees] C (-117 [degrees] F) and at a pressure of approximately 3.2
meters of
water column. Reddy has estimated that
such a gas
cylinder
system could almost double the cost of a pipeline in
Pura
village.(57) It is doubtful that
individual families would
have
sufficient capital to purchase cylinders (Rs 300-700/cylinder).
However, this
concept should not be completely dismissed.
The
revenue-generating potential of a large-scale
biomass
system might justify an investment in a pressurized gas
cylinder
system. The compressor itself could be
powered by the
biogas
system.
Using biogas
for cooking is more complicated than the literature
suggests.
KVIC (1980), Finlay (1978), National Academy
of
Sciences
(1977), Bhatia (1977), the Indian Council of Scientific
and
Industrial Research (1976), and Parikh and Parikh
(1979) all
suggest that gas requirements for cooking vary between
0.2 and 0.4
[m.sub.3]/person/day, although some anecdotal field
reports
suggest that these figures may be high.(58)
The
difficulty in establishing norms for gas required for cooking
is due to our
scanty knowledge of rural cooking habits.
The
key to
formulating cooking norms is to determine the usable or
net energy
used by a family to prepare meals.
There are several
levels of
analysis needed to generalize about net available
cooking
energy. Diet varies regionally
according to climate,
custom,
income, etc. Even the quality
(calorific value) of
identical
fuel sources, such as firewood, varies regionally.
Finally, the
efficiencies of stoves (often a group of stones),
and
consequently the thermal efficiencies of different fuels,
are also
highly variable.
A detailed
investigation of these variables would begin to shed
some light on
village cooking needs. These are more
difficult
to determine
than the cooking needs of a wealthier farmer, who
is the most
likely consumer of a family-sized biogas plant, and
on whom data
do exist. At the moment, there is no
accurate way
to generalize
about the gas required for village cooking.
KVIC
did attempt
to generate data on the calorific value, thermal
efficiency,
and "effective heat" of different fuels,(59) but no
description
of its methodology is included in its report.
It
also assigned
calorific values of biogas and wood, which conflict
with other
analyses, thus leaving KVIC information open
to question.
Gas
requirements for cooking can affect significantly the performance
and economic
viability of a village system, depending
on competing
uses for the gas. This is especially
true if non-cooking
uses of
biogas are a source of revenue. More
research
and
development are needed on cooking burners, stoves, and
cooking
vessels (and on their heat conducting properties),
which collectively
affect the efficiency of gas consumption.
The relative
system efficiencies of metal and terracotta cookware
need to be
analyzed. Though metal is a better
conductor of
heat, it also
cools faster. Terracotta vessels take
longer to
heat yet they
retain their heat. Rice cooked in
terracotta
vessels often
is cooked only until half-done. The
vessel is
then removed
from the fire, and the remainder of the cooking is
done with the
heat that radiates from the walls of the terracotta
vessel.
This is why both energy consumption and
cooking
costs need to
be analyzed with respect to cooking systems,
i.e., the
fabrication of all utensils, their collective thermal
properties,
the costs of the various components (energy source,
stove,
vessel) over their useful lives, and the nature of the
foods or
liquids being heated.
The Gas
Crafters' iron burner recommended by KVIC costs Rs 100.
Though
"rated" at 60 percent efficiency, there have been complaints
about its air
valve becoming clogged with fat and oil,
and that not
all cooking vessels rest upon it equally well.
Developing
and Consulting Services, Butwal, Nepal, claims to
have both
improved this design and reduced its cost to Rs 80.(60)
There have
been other attempts by the Gandhigram Trust and PRAD
to develop simple
ceramic burners for as little as Rs 20, but
these are
still experimental and little is known about their
performance
or durability. There are many
photographs of a
variety of
ceramic, bamboo, and stone-filled tin can burner
designs from
China,(61) but again, no performance, durability, or
cost data
exist. The stove used for cooking with
biogas may
itself have
to be modified to achieve maximum efficiency.
The
Chinese often
seem to set their cooking vessels on top of simple
burners in
deep stoves that surround the vessels, thereby
using heat
more efficiently.(62)
Social or
cultural factors must be considered when designing a
distribution
system. The flame properties of biogas
make burners
difficult to
light unless a cooking vessel is resting on
the burner
prior to lighting the gas. This can
conflict with
certain
religious ceremonies that reverse the procedure as part
of the need
to show reverence toward fire.(63)
Village cooking
requirements
may be significantly affected by season.
In many
areas, when
labor demand increases during harvesting and planting,
groups of
workers are fed at staggered times throughout
the day.
During these peak times, stoves often are
kept hot all
day for as
long as two months of the year. Such
increases in
cooking energy
requirements need to be studied by anyone involved
with the
establishment of a village system.
The decision
to use gas directly for lighting gas lamps, as
opposed to
running a diesel generator to produce electricity
for electric
lights, depends on the local demand for electricity.
Ghate found
that while electric lighting consumed less gas
than direct
gas lighting, gas lamps are far cheaper in terms of
cost per
delivered candle power. Electric lights
are brighter
and more
reliable than gas lamps. Roughly .13
[m.sup.3]/hr of gas is
needed to
energize one gas lamp. Slightly less
gas is needed
for electric
lighting, depending on the generator output.(64)
Ghate admits
that his data are open to question and that the
high cost of
electric lighting might make sense if a generator
also was used
for other operations.
Biogas has
been used successfully to power all types of internal
combustion
engines. This raises the technical
possibility
of biogas
providing energy for rural agriculture as well as for
industrial
machinery and transportation. There are
various
reports of
tractors powered by methane stored in huge bags
towed behind
the tractor. The practicality and
economics of
such a scheme
are open to question, given little hard data.
Stationary
motive power for operating pumpsets, milling and
grinding
operations, refrigerators, threshers, chaffers, and
generators,
etc., seems to be a more appropriate match between
energy source
and end-use demand. Petrol engines have
been run
solely on
biogas by the KVIC, several of the Indian Institutes
of
Technology, and PRAD, among others.
Since most agricultural
engines are
diesel powered, the remainder of this discussion
will be
confined to biogas-diesel (dual fuel) engine operation.
The use of
biogas in engines could be of great importance to
rural
development projects, providing motive power to areas
where the
availability or cost of commercial energy (diesel
fuel or
electricity) has precluded mechanized activities.
A diesel
engine carburetor is easily modified to accommodate
biogas.
The necessary conversion skills and
materials exist in
most
villages. Kirloskar Oil and Engines,
Limited has marketed
dual fuel
biogas-diesel engines for several years at a price
roughly Rs
600 more than regular diesel engines.
Their line
features a
modified carburetor and a grooved head for swirling
the biogas,
which was found to improve performance.
Kirloskar
does not sell
the carburetor separately. The firm
encourages
farmers to
consider "the option" when they purchase a new
engine.
Kirloskar engineers report that good engine
performance
occurs with a
biogas to diesel mixture of 4:1, which works out
to .42
[m.sup.3] of biogas per BHP/hr.(65) In
actual operation, the
ratio may
exceed 9:1. The mixture is regulated by
a governor
that reduces
the amount of diesel flow as more gas is introduced,
keeping power
output constant. There is an observed
drop
in the
engine's thermal efficiency with greater gas consumption.
However,
research at IIT-Madras has shown that this may
be due to the
leanness of the biogas mixture.
Reducing incoming
air improves
performance except at full power output.
Generally,
efficiency
increases with power output.(66) The gas should be
delivered to
the engine at a pressure of 2.57-7.62 cm water
column.(67)
Removal of [CO.sub.2] also improves engine performance.
Biogas makes
engines run hotter, and therefore proper cooling
is
important. Biogas slurry should not be
used to cool engines
since the
suspended solids can clog the cooling mechanism and
act as an insulator,
thereby trapping heat. Air-cooled
engines
must be used
if slurry is mixed with irrigation water that
normally
would be used as a coolant.
There is
little available data on the potentially corrosive
effects of
the [H.sub.2]S present in biogas, although engines have
been run for
some time with no reported corrosion.
Iron filings
can be used
to filter out [H.sub.2]S. In addition
to the reduced
operating
costs for fuel engines, removing [H.sub.2]S has produced the
following
benefits:
1.
Reduced emission of CO.
0
2.
Increased engine life (up to four times normal life).
3.
At least a 50 percent reduction in maintenance costs due
to longer life of lubrication oil.
Freedom from gum,
carbon, and lead deposits.
4.
Lower idling speed and immediate power response.(68)
When energy
conversion efficiency losses are calculated for
diesel
generators, roughly 1 kwh is generated for every 0.56 [m.sup.3]
of
biogas. A 15-KVA diesel generator (12
kw) running two 3.75
kw electric
pumps (5 hp) for eight hours a day would require
almost 53.8
[m.sup.3]/day, compared to 33.6 [m.sup.3] if the pumps were
powered with
dual fuel engines. This is because of
the difficulty
of finding
electrical generators that are matched exactly
to peak power
requirements.
Slurry Use
and Handling
The effluent
from a biogas plant can be either sludge, supernatant,
or slurry
depending on the design and operation of the
system.
Most Indian systems have slurry as their
output. The
remainder of
this discussion pertains to slurry that is formed
primarily by
mixing dung and water, although it probably
applies to
any digested biomass.
The main
advantage of anaerobic digestion is that it conserves
nitrogen if
the slurry is handled properly. Though
approximately
20 percent of
the total solids contained in the organic
material are
lost during the digestion process, the nitrogen
content
remains largely unchanged. The nitrogen
is in the form
of ammonia,
which makes it more accessible when the effluent is
used as
fertilizer. Aerobic digestion, on the
other hand, produces
nitrates and
nitrites. These are likely to leach
away in
the soil, do
not become as readily fixed to clay and humus, and
are not as
easily used by water-borne algae.(69)
Bhatia cites
earlier observations
that the amount of ammoniated nitrogen
increases to
almost 50 percent of the total nitrogen content of
anaerobically
digested dung, as compared to 26 percent in fresh
dung.(70)
The quality
of organic manures is greatly affected by handling
and storage
methods. Table V-1 shows nitrogen loss
related to
storage time.
Biogas slurry
can be handled in any of the following ways, with
the choice
depending on both cost and convenience:
1.
Semi-dried in pits and carried/transported
to the fields.
2.
Mixed with cattle bedding or other organic
straw in pits to
absorb slurry, and then transported to the
fields.
3.
If a high water table exists and (1) or (2)
are done, then
the "reformed" slurry that has
been mixed with ground water
can be lifted out of the pit in buckets
and dried further.
4.
Applied directly to fields with irrigation
water or through
aerial spraying.(72)
Table V-1(71)
Nitrogen Lost Due to Heat and
Volitilization
in Farmyard Manure (FYM) and Biogas Slurry
Loss as Percentage
Manure
of
Total N
FYM applied
to fields immediately 0
FYM piled for
2 days before application 20
FYM piled for
14 days before application 45
FYM piled 30
days 50
Biogas slurry
applied immediately 0
Biogas slurry
(dried) 15
Biogas slurry
can be a problem to store and transport, depending
on local land
use, the amount of effluent produced daily,
the distance
from the digester to the fields, and the willingness
of workers to
handle slurry and deliver it to either
household
pits or fields. There may be some merit
to evaporating
the water
from the slurry, thereby reducing storage space
requirements,
and then recycling the water back into the biogas
system.
This should aid the digestion process,
facilitate
slurry
handling, and reduce net water consumption.
The following
are additional benefits of using biogas slurry:
*
Potentially decreasing the incidence of
plant pathogens and
insects in succeeding crops.(73)
*
Speeding the composting process by using
additional organic
materials that can be added to a compost
pit.
*
Reducing the presence of odor, white ants,
flies, mosquitoes,
and weed seeds in the compost pits.
*
Making it difficult to steal manure.(74)
It is
necessary to compare the nutrient content of biogas slurry
with that of
other composting methods to determine the best
use of
resources and evaluate alternative investments.
A well-managed
compost pit
may yield manure that is only marginally
inferior to
that from a biogas system. The cost of
a biogas
system must
be compared with the utility of its effluent.
There
is a great
deal of confusing literature on the subject, which
analyzes
fertilizer contents, handling, and application methods.
More
scientific research in this area is needed so that
accurate
comparisons between different composting methods can
be made.
The most
practical and perhaps most useful kind of research
would be to
study field conditions by applying chemical fertilizers,
composted
manures, and digested slurry to experimental
plots and
carefully monitoring the crop yields for each group.
There have
been reports from China indicating that use of biogas
slurry
increases crop yields 10-27 percent per hectare compared
areas that
receive manure that is aerobically composted.(75)
Unfortunately,
and as is the case with much of the
literature on
the Chinese experience, there is insufficient
data to
substantiate descriptive reports. In
any case, care
should be
taken to ensure that handling and application techniques
follow
exactly either those methods currently in use in
villages or
those that could easily be adopted by villagers.
Too often,
the laboratory tells us nothing about actual practice
in the field.
VI.
Economic Analysis of a Village System
Numerous
articles and books, have attempted to examine the
economics of
biogas systems.(76) Most of these
analyses have been
concerned
with family-scale systems, hypothetical village systems,
or the Fateh
Singh-Ka-Purva system in Uttar Pradesh.
Often the
conclusions of these studies are based on certain
critical
assumptions over which, not surprisingly, there is
considerable
disagreement. These assumptions range
from values
assigned to
capital and annual costs, calorific values for
fuels, and
thermal efficiencies, to per capita energy consumption,
market
prices, and the opportunity costs of labor,
energy,
organic residues, and capital. The
nutrient content and
end-uses of
different organic materials also are subject to
debate.(77)
It is beyond
the scope of this study to untangle these disagreements.
Many of them
are due to our limited knowledge of
rural
life. Others are rooted in basic
disagreements over
"correct"
economic theory, which sometimes approach the level
of a
theological dispute or metaphysical debate in which one
either
"believes" or "does not believe."
This is especially
true in the
cases of social rates of discount and opportunity
costs.
Such questions employ many economists, and
it is unlikely
that the
following discussions will either threaten those
positions or
reconcile such divergent opinions.
Many economic
studies attempt to assess the overall impact of
the
large-scale adoption of biogas plants.
These include the
costs and
benefits to society as a whole, as well as the macro-level
resource
demands for steel, cement, manpower, and other
factors
required for a massive biogas program.
Such analysis is
valuable when
the range of costs and benefits of individual and
village
systems is known. However, this range
cannot be determined
accurately at
the present time because so little is known
about rural
energy consumption patterns.
The analysis
presented here has the relatively modest objective
of assessing
the performance of a particular biogas system in a
particular
village. It studies a large
village-scale system.
Such systems
have been more exhaustively analyzed than small
family
plants, and also hold more promise for realistically
meeting the
energy needs of the rural poor. Two
measures of
performance
will be examined.
1.
The net impact of the biogas system on the
village economy
as a whole, determined by the net present
value (NPV) of
quantifiable annual benefits minus
costs. NPV measures the
value of future benefits and costs and
discounts them back
to the present using a given interest
rate.
2.
The ability of the biogas system to bring in
enough revenue
to ensure its self-sufficient
operation. This is measured in
terms of an undiscounted payback period
derived from annual
income minus annual capital and operating
expenditures.
These two performance
measurements are useful in determining if
the village
"product" is increased as a result of the introduction
of the system
and if the system can pay for itself.
Four
limits to
these measurements require further discussion.
1.
There are serious shortcomings to such
social benefit-cost
analyses due to the difficulty of
quantifying many of the
effects of a project.(78)
For example, some important values
pertaining to this study are difficult to
measure:
*
Labor freed from gathering firewood or other fuels, and
from cooking meals.
The greater amount of useful energy
from biogas could reduce the time
required for cooking by
one-half to two-thirds.
*
Decreased incidence of eye and lung diseases and irritations,
improved cleanliness in the kitchen,
and greater
ease in cleaning cooking utensils due
to the clean burning
biogas.
This is in sharp contrast to chulahs, which spread
smoke and carbon deposits throughout
the kitchen area.
*
The improved quality and quantity of food consumed due to
crop yields that are increased because
energy is available
for water pumping, and because the
nutrient and humus content
of the slurry make it a better
fertilizer than that
derived from traditional village
composting methods.
*
Freeing manure piles from white ants, weed seed, and odor,
and making the manure more difficult to
steal due to its
semi-liquid state.
Theft of manure has been a problem in
some villages where the manure is
scarcer than in the
village under study here.
*
Effects of better lighting on education by creating more
time for readinq and study, on the
possible reduction in
birth rates, and on increased equality
among villagers
because prestigious electric lighting
is available to all.
*
The increased sense of confidence and self-reliance that a
successful biogas system might instill
in the villagers,
with the long-term potential for
greater intra-village
cooperation, innovation and invention,
and employment
generation and investment.
*
Changes in the demand for various resources such as fossil
fuels, chemical fertilizers, etc., and
some secondary
effects associated with these changes
such as foreign
exchange requirements, release of
atmostpheric hydrocarbons,
rate of soil depletion, and
deforestation. Overall
soil quality might increase if large
quantities of
biogas slurry, which is rich in
nitrogen and humus, were
spread over the fields.
*
Development of rural industries that require a cheap,
dependable energy supply, such as
biogas.
*
Impact of the system on the village distribution of income,
which may vary according to income,
cattle, and land
ownership.
All of these
important effects are excluded from the analysis
because of
the difficulty of assigning a cardinal value to
them.
This results in lost data and will distort
the cost and
benefit
calculations.
2.
Net present value (NPV) calculations suffer
from a number of
theoretical limitations, the most serious
being the inability
of an NPV figure to represent fully the
real utility of
a project.
Certainly, a negative or zero NPV indicates that
a project is not worth pursuing.
However, a positive NPV,
even if quite large, does not necessarily
imply that a project
should be implemented.
The NPV of a particular project
must be evaluated along with the NPV of
all other projects
that could be implemented with the same
factor inputs of
natural resources, labor, and
capital. However, these other
projects may or may not achieve similar
goals. The criteria
used to select projects may themselves
vary according to the
perceived priority of the goals.
This often depends on who
is doing the perceiving.
A landless peasant, a block development
officer, or a social scientist all may
have quite
different ideas about the needs of the
poor. Such are the
methodological and political complexities
of determining the
best use of resources.
This problem is fundamental to development
planning.
3.
Even if one project stands out among many as
having the
greatest NPV, this tells us nothing about
the critical problems
of cash flow and access to capital.
The inclusion of
cash flow and payback data in the economic
analysis that
follows is presented to help remedy this
deficiency. However,
even a project that seems financially
viable is not
automatically guaranteed access to
capital. Local and
national politics, lending institutions'
perceptions of the
project's risks, and/or government
perception of a project's
importance (which affects a variety of
possible incentives
such as price controls, subsidies, loan
guarantees, taxes,
compulsory legislation, etc.) dramatically
influence a
project's financial viability.
The problem of access to
capital is excluded from the analysis.
4.
All prices used in these calculations are
market prices,
which are affected by the performance of
the larger economy
--inflation, material availability,
infrastructure performance,
government price setting, etc.
Shadow price calculations
do not alter the fact that benefits and
costs will
occur within the prevailing economic
context. These benefits
and costs may be subjected to many
political and economic
distortions.
Thus, any analytical framework for assessing
the project may well distort the
"real" impact of the project.
On the other hand, while reliance on
prevailing prices
and rates of discount may reduce the
precision of the following
analysis, it does account for the actual
market
constraints that a village biogas system
would face,
defining minimal performance requirements.
The village
system discussed in the following analysis is being
constructed
by the ASTRA group in Pura Village. It
will incorporate
advanced
design features and be self-supporting in terms
of its annual
operating costs. (The Karnataka State
Government
is providing
the capital investment.) The data base
for the
analysis is
obtained from A.K.N. Reddy, et al., A Community
Biogas System
for Pura Village (1979).
ASTRA has
provided information on Pura village and cattle population,
cooking
needs, dung availability, and some of the biogas
system
component costs. Unfortunately, much of
the actual
data
necessary for an accurate analysis are simply not available.
All estimates
and assumptions are explained in detail and
are the sole
responsibility of the author, who is grateful to
Dr. Reddy for
his kind permission to use some of the preliminary
data in this
study. Readers should note that
conclusions
that may be
drawn from the following discussion should in no
way be used
to judge the performance of the actual system under
construction
in Pura. The following analysis
proceeds from
certain
assumptions that differ slightly from those upon which
the Pura system
is based. Some of the data and cost
estimates
for the
actual Pura system will be subject to revision.
Nonetheless,
the available
data from the Pura system will enable us
to obtain a
fair picture of how well a village biogas system
will fare
financially.
The ASTRA
biogas system under construction in Pura village has
four main
functions:
1.
Provide cooking gas for each household.
2.
Operate a pumpset for 20 minutes a day to
fill an overhead
storage tank with water.
This should satisfy village
domestic water requirements and provide
the water needed to
dilute the dung and clean the inlet and
outlet tanks.
3.
Operate a generator for three hours to
provide electric
lighting in the 42 households that
currently are not
connected to the central grid.
4.
Operate a dual fuel engine to run a ball
mill as part of a
rice husk cement manufacturing operation.
The original
feasibility study for Pura specified the construction
of a single
42.5 [m.sup.3] ASTRA design digester with a mild
steel
floating-drum gasholder. It would
provide enough biogas
for all the
above operations. The release of gas
would be
synchronized
with various end-uses throughout the day.
The 42.5
[m.sup.3]
capacity was determined by the biogas requirements of the
various
system tasks, and allowed for some population
increase.
The ASTRA
team estimated that the 56 households (357 people) in
Pura would
require 11,426 [m.sup.3] of gas per year for cooking.
This
averages
about 0.088 [m.sup.3] per person per day.
Although this is
less than the
0.2-0.3 [m.sup.3] per person per day norms cited by KVIC
and others,
we will assume that ASTRA's figure is correct for
the level of
subsistence and diet in Pura village.
The annual
gas required to operate all of the engines is estimated
at 3,767
[m.sup.3]. This is calculated as shown
in Table VI-1 on
the following
page.
Total system
requirements for cooking and engine operations are
15,193
[m.sup.3] of gas per year. Based on
ASTRA observations, an
estimated
average of 7.35 kg fresh dung per animal can be collected
from the
night droppings of tied cattle. Added
to this
figure is an
estimated 401.5 kg of collected organic matter--which
also could be
2.65 kg more dung per head. This gives
an
equivalent of
10 kg of dung or dung equivalent per animal per
day.
Regardless of the actual amount of biomas
fed into the
system, a 5
percent loss is assumed in collection and handling.
So, of the
532,900 kg available, 506,255 kg/biomass/year is
actually
used. This is roughly 1,387 kg/biomass
that could be
fed into the
system daily. These estimates are very
conservative.
Cattle
population is held constant, and cropping patterns
are unchanged
from the present mix. Both of these
factors are
likely to
change during the life of the system in a way that
probably will
increase the availability of biomass.
The maximum
amount of gas produced from these estimates of
Pura's
available biomass is described in the analysis as the
maximum
output scenario. The cost of a system
designed to produce
only enough
biogas to perform specified tasks is described
as the
minimum cost scenario. The two
scenarios differ in the
amount of
biomass that will be fed into the system.
This
affects the
required digester volumes and digester costs.
Table VI-1. Annual Gas
Requirement
Function
Gas Requirement
1.
Water pumping
(20 minutes/day) X (.42 [m.sup.3] gas/
BHP/hr) X (5
hp) X (358 days) =
251 [m.sup.3]
2.
Operating diesel gener-
(3 hr/day) X (.42 [m.sup.3] gas/BHP/hr)
ator for lighting
X (5 hp) X (358 days) = 2,256
[m.sup.3]
3.
Operating ball mill for
(2 hr/day) X (.42 [m.sup.3] gas/BHP/hr)
rice husk cement manu-
X (5 hp) X (300 days) = 1,260 [m.sup.3]
facturing
TOTAL
3,767 [m.sup.3]
The system is
shut down one week each year for repairs,
cleaning,
etc., which may become less over time.
It is
assumed that
there is no unforseen vandalism, natural
disasters,
etc.
The daily
biomass charge is determined by the gas requirements
of the tasks
to be performed. It equals the daily
gas demand
for all uses
divided by the gas yield per kg of biomass.
The
analysis
considers three different levels of demand, which
correspond to
three different biogas systems. For
each of these
three
systems, which are described as Models 1, 2, and 3, both
the minimum
cost and maximum output scenarios are examined.
It
should be
noted that the digester with sufficient capacity to
digest all
the net available biomass--the maximum output
scenario--is
identical for all three models. Because
the gas
demand is
different in each model due to the different tasks
performed,
any surplus gas that will be available in the maximum
output
scenario will vary with each model, even though the
digester
costs will remain constant.
The three
models are described below:
Model 1:
Provides enough biogas for cooking, electric
lighting,
and domestic water requirements for
the village,
as well as water to operate the
biogas system.
Model 2:
Provides gas for cooking, electric lighting,
water,
and operating the ball mill to grind
rice husks to
produce rice husk cement.
Model 3:
Provides gas only for electric lighting and
the rice
husk cement operation.
Table VI-2
shows the gas and biomass requirements for the
models, based
on earlier calculations.
The Pura
village plan calls for two digesters of roughly
21.5
[m.sup.3] capacity each. Two smaller
systems were decided upon
after a risk
analysis demonstrated that this reduced the "downtime"
the system
due to repairs and maintenance. At a
given
moment, only
one of the digesters should be out of service so
that service
will not be disrupted completely, as would be the
case with one
large digester. As described in Table
VI-1, the
system is
assumed to have an annual repair and maintenance
period of one
week.
The system
used in the following economic analysis is based on
the
redesigned ASTRA system with one major modification:
the
analysis
assumes that a small volume of water covered by a
sheet of
polyethelene is held on top of the gas holders by
retaining
walls similar to the ASTRA design described earlier.
The
polyethelene is treated for ultraviolet radiation.
This
simple solar
water heater reduces system cost and improves performance
due to the
increased gas yield that can be expected
from
"hot charging" the slurry mixture.
Field reports indicate
that the
"hot charge" system, when combined with the practice
of mixing
dung with other organic materials, could easily increase
gas yield by
25 percent.
This means
the biogas system, which normally would produce gas
at the rate
of roughly .038 [m.sup.3]/kg of fresh biomass, now has a
gas yield of
.0475 [m.sup.3]/kg of fresh biomass.
This is a very
conservative
estimate. Empirical results may show
that gas
yield almost
doubles. While actual gas production
rates will
fluctuate
slightly due to seasonal ambient temperature changes,
the gas yield
of .0475 [m.sup.3]/kg fresh biomass represents an average
or minimum
gas production figure, and is used for year
round
calculations.
A number of
system costs need to be described in detail, since
they differ
for each of the models. The capital
costs for two
biogas
systems that each have half the total system capacity,
and which are
built with ferrocement gas-holders and solar
water heater
attachments, are shown in Table VI-3.
Information
is based on
detailed calculations and discussions with ASTRA
biogas
engineers. Table VI-4 shows system
costs in addition to
digester
costs.
ASTRA surveys
also indicate that approximately 150,000 kg of
firewood are
collected for cooking purposes. Of
that, 4 percent
is purchased
at Rs 0.04/kg. While time spent
gathering firewood
is reduced by
almost 36,950 hours, the direct annual
monetary
savings that
accrue from the biogas system's operation are only
about Rs 240
(150,000 kg of firewood) X (4 percent purchased) X
(Rs .04 kg
firewood) = approximately Rs 240.
Despite a relative
Table VI-2 Gas and Biomass
Requirements for Different models
Under Minimum Cost and
Maximum Output Scenarios
(in
[m.sup.3] per day)
Model 1
Model 2 Model 3
Cooking, Lighting, Lighting,
Pumping,
Cooking, Lighting,
Pumping, and Ball
and Ball Mill
and Pumping
Mill Operation
Operation
System
Design Minimum
Maximum
Minimum Maximum
Minimum
Maximum
Scenario
Cost
Output Cost
Output
Cost Output
Cooking
31.3
31.3
31.3 31.3
--
--
Water
Pumping 0.7
0.7
0.7
0.7 0.7
0.7
Lighting
6.3
6.3
6.3 6.3
6.3
6.3
Ball
Mill --
-- 4.2
4.2
4.2 4.2
Surplus
Gas --
26.7
--
22.5 --
53.8
Total Gas
Required
(Approximately)
38.3 65.0
42.5
65.0 11.2
65.0
Total Annual
Biomass
Required 294,306kg
506,255kg
326,579kg 506,255kg
86,021kg
506,255kg
(fresh dung
equivalent)
Note:
Biomass required for each model is based on a gas yield of .0475
[m.sup.3]/kg.
Table VI-3 Biogas Digester
Capital Costs for Models 1-3
Model 1
Model 2
Model 3
Minimum
Maximum
Minimum Maximum
Minimum
Maximum
Cost
Output
Cost Output
Cost
Output
Daily Gas
Capacity ([m.sup.3] 38.3
65.0
42.5 65.0
11.2
65.0
Digester
System Cost 13,400
22,100
15,000 22,100
4,500
22,100
(Rs)
Table VI-4 System Costs for
models 1-3 (in Rs)
Model
1 Model 2
Model 3
Equipment
5 hp engine and
15,500
15,500 15,500
KVA generator
Electrical system
5,500
5,500
5,500
Pumpset
700
700
700
Ball mill
--
4,750
4,750
Shed for equipment
3,000
6,000 6,000
Water tank
550
550
550
Miscellaneous (including
8,000
8,000
8,000
roughly Rs 1,500 for
technical supervision)
Subtotal
33,250 41,000
41,000
Gas pipeline for village
10,000
10,000
--
Total
43,250
51,000 41,000
abundance of
forests, Pura villagers spend an average of three
hours per day
collecting firewood. In other areas,
where deforestation
pressures are
far more serious, the price of firewood
would be much
higher, increasing the value of savings from
reduced
firewood consumption. In such areas,
more dung would be
burned as
fuel, so greater benefits would be realized by recapturing
the
fertilizer value of the dung. Another
possibility
might be that
some of the Rs 8,000 used to purchase miscellaneous
material for
Model 3 could be freed up, since items like
pipe
fittings, valves, etc., would not be needed if the distribution
pipeline were
not constructed. Some of these savings
could be used
to purchase improved wood-burning stoves that
could reduce
firewood consumption by as much as 50 percent.
This would
amount to only Rs 120 in total reduced village firewood
purchases,
but would save more than 18,400 hours in collecting
firewood.
Additional benefits and costs that might
accrue from
the creation of village woodlots have lot been
considered.
No direct
government subsidy for the biogas system is considered
in this
analysis. There may be some cases where
the NPV
of the system
in a village is positive, but the system generates
insufficient
cash flow to be viable financially.
Such
cases might
justify a possible subsidy if shadow prices and
shadow wage
rates are included in the NPV calculations and the
NPV remains
positive.
It may be
possible for Pura villagers to form an "association"
if they can
prove that the project will largely benefit the
poor.
Indian lending institutions can be somewhat
flexible
about the
criteria used to determine if a particular group can
qualify as an
"association." Associations
are eligible to
obtain loans
at 4 percent interest. We have assumed
such eligibility
in our
calculations, although the effects of a loan at
10 percent
also have been analyzed. To simplify
calculations,
it has been
assumed in the analysis that loans will be amortized
over 5 years,
in equal installments, with a one-year
grace
period. The equal installments are
calculated using
coefficients
from standard annuity payment tables.
For a 4
percent loan
paid back over 5 years in equal installments, the
annual
payment equals the total borrowed capital divided by
4.452.
For a loan at 10 percent with similar terms,
the annual
payment equals
the total borrowed capital divided by 3.791.
The
use of
annuity formulas tends to spread capital costs over
time,
increasing the NPV of a project. The
distortions caused
by this
simplified way of calculating loan payments are very
small in this
analysis due to the large operating costs of the
system.
In addition, the impact of inflation on the
various
costs and
benefits has been ignored. Rural wage
rates are the
largest
component of operating costs, and are not expected to
rise
significantly. If they did rise, the
increase probably
would be
canceled out by the increased savings caused by the
reduced
consumption of increasingly costly commercial fuels.)
We have
assumed further that dung is provided to the system
free of
charge except for labor costs, which are discussed
below.
Slurry also will be distributed freely on
the basis of
the amount of
dung contributed by each household. We
have
assumed that
water and land will be made available for free to
the system by
the villagers who have agreed to do so as a
demonstration
of their willingness to participate in the
project.
At the time
of this writing, there was little information
readily
available on the distribution of and crop yields from
land holdings
in Pura. Given a village of Pura's size
and population,
the land
under cultivation could be approximately 60
hectares.
A typical yield of rice paddy for these
holdings
would be
1,500 kg/hectare/year. An estimate of
the average
price a
farmer obtains for this paddy is about Rs 90/quintal
(100 kgs).
There is no information on the percentage of
agricultural
production consumed by the villagers themselves
versus the
percentage that might be sold in markets outside the
village.
To simplify the calculations, we will assume
that the
village
consumes all that it grows.
Furthermore, we will assume
that the
nutrient and humus content of biogas slurry (consisting
of at least
all the dung currently applied as manure) is
such that it
has the net effect of increasing agricultural
yields by 10
percent over those obtained through current fertilizer
practices,
even if these include the application of
chemical
fertilizers.
Increases of
greater than 10 percent have been reported in
China, where
the extensive recycling of agricultural and animal
wastes,
including aerobic composting of wastes, is an ancient
tradition.
The 10 percent increase in yield is assumed
to be a
net increase
over existing methods of "scientific composting."
Thus, if the
villagers sold the expected increase in crop
yields, the
net increase in village revenue from agriculture
(IA),
attributable to the use of biogas slurry equals (60
hectares) X
(10 percent increase/hectare) X (1,500 kg of
paddy/hectare)
X (Rs 90/100 kg of paddy). This equals
Rs 8,100
for the
maximum output scenario. In the minimum
cost scenarios,
proportionately
less revenue would be generated because less
biomass would
be digested. The specific IA's for the
minimum
cost scenario
of each of the three models is calculated by
multiplying
Rs 8,100 by the ratio of biomass consumed in each
minimized
cost scenario. That figure then is
divided by
506,255,
which is the biomass consumed in the maximum output
scenario in
all three models.
This measure
of the benefit of biogas slurry is used
because it
represents a
tangible cash benefit. Many economic
analyses
derive
monetary benefits from the use of slurry by assessing
the nutrient
content of biogas slurry, determining the equivalent
quantity of
chemical fertilizer, and converting this to a
monetary
benefit by multiplying the quantity by the unit price
of chemical
fertilizer. The problem with this
method is that it
implies that
a farmer would have purchased the marginal equivalent
amount of
fertilizer. It is not clear at all that
farmers
would have
made such purchases in the absence of available
biogas
slurry; whether the money is actually "saved" is a
matter of
debate. What is clear is that some
increase in agricultural
productivity
will occur due to the superior nutrient
and humus
characteristics of biogas slurry. This
will result in
increased
earnings. Even so, while the 10 percent
increase in
yield is a
reasonable estimate, it needs to be
corroborated by
empirical
results from field tests that also analyze the yield
empirical
alternative composting techniques.
The increased
agricultural productivity for the minimum cost
scenario for
each Model is calculated by multiplying the ratio
of biomass
required for the minimum cost system times the ratio
of biomass
required for the maximum output system times Rs
8,100, as
explained earlier. The increased
Agricultural productivity
resulting
from using the slurry in each of he
minimum cost
systems is shown below:
Model 1
= 294,306 kg
X Rs
8,100 =
Rs 4,709
506,255 kg
Model 2
= 326,579 kg
X Rs
8,100 =
Rs 5,225
506,255 kg
Model 3
= 86,021 kg
X Rs
8,100 =
Rs 1,376
506,255 kg
According to
ASTRA surveys, Pura village annually consumes
1,938 liters
of kerosene, at Rs 2.25 per liter, for lighting.
This annual
expenditure of Rs 4,360 for lighting will be
reduced as
follows:
(42 households) X (40 watt bulb/house) X (3
hrs/days) X
(358 days) X
(Rs 0.44/kwh) = Consumption (C)
C
= approximately Rs 791
1,000/kw
However,
because the Rs 791 is paid by villagers to the village
biogas
operation, it also appears as a village benefit, i.e.,
income from
the sale of energy. Therefore, the
village as a
whole saves
all money previously spent on kerosene purchases
(Rs
4,360). In terms of the cash flow position
of the biogas
system, the
sale of electricity for lighting is treated as
revenue of
approximately Rs 791.
A series of
costs and benefits related to each model requires
more detailed
explanation. Labor costs for the
different models
are as
follows:
Model 1:
Cooking, Lighting and Pumping
1 skilled laborer/supervisor =
(Rs 7.50/day) X (363 days)
= Rs 2,737.50
3 unskilled laborers =
(Rs 5/day) X (3 persons) X (365
days) = +5,475.00
Total labor costs =
Rs 8,212.50
Model 2:
Cooking, Lighting, Pumping and Ball Mill
Operation
and
Model 3:
Lighting, Pumping and Ball Mill Operation
Same as Model 1
=
Rs 8,212.50
Plus the cost of 1 supervisor at
(Rs 300/month) X (12 months)
=
3,600.00
Total
=
Rs 11,812.50
These labor
costs are reflected in the cash flow calculations.
However, in
the village benefit calculations, it is assumed for
purposes of
simplicity and lack of actual data that wages paid
to operate
the system will be spent within the village itself.
Therefore,
labor "costs" to the village are cancelled by an
equal amount
of village "benefits" that would accrue from those
wages being
spent on village goods and services.
This clearly
is a gross
oversimplification of complex capital flows.
However,
given the
orders of magnitude involved, this approach
will suffice
for our purposes.
Operation and
maintenance costs for each model are shown in
Table VI-5.
Table VI-5 Annual Operation and
Maintenance Costs
Model 1
Model 2
Model 3
Digester
Maintenance 250.00
250.00
250.00
Diesel Fuel
(a)
for running pumpset
79.75
79.75 79.75
generator
724.95
724.95 724.95
ball mill
--
-- --
Lubrication
Oil (b)
for running pumpset
47.25
47.25
47.25
generator
429.60
429.60 429.60
ball mill
--
240.00 240.00
Raw Material
Purchase (c) --
4,800.00
4,800.00
(a) A 5 hp
dual fuel engine requires .05 liters of diesel fuel/BHP/hour.
At Rs
2.70/liter, a 5 hp engine costs Rs 0.675/hr to
operate.
Diesel fuel consumption figures are derived
by:
Pumping:
(20 minutes/day) X (358 days) X (Rs 675) = 79.75
Generator:
(3 hours/day) X (358 days) X (Rs 675) = 724.95
Ball Mill:
(2 hours/day) X (300 days) X (Rs 675) = 405.00
(b)
Similarly, lubrication costs for a 5 hp engine/hr are:
(.008
liters of
lube oil/BHP/hr) X (Rs 10/liter of oil) X (5 hp) = Rs
.40.
This cost is multiplied by the same running
times as shown
above.
(c) 24,000 kg
of lime will be purchased from a nearby village at
Rs 0.20/kg,
and will be mixed with the ground rice husks to
produce
cement.
Finally, we
will assume that the surplus gas generated in the
maximum
output scenario could be sold at the equivalent diesel
or
electricity price, and that demand will keep pace with
supply.
This represents a potentially large source
of revenue
to the
system. The conversion factors for the
equivalent prices
of diesel and
electricity can be calculated as follows:
Surplus gas
sold as diesel. The value of surplus
gas sold as
diesel equals
the difference between the cost of running an
engine on
biogas and the cost of running it on diesel fuel, as
is shown in
Table VI-6.
Table VI-6 Fuel Costs of Generating 1
BHP with a Diesel
and a Dual Fuel Engine
Standard
Dual fuel
Diesel engine
biogas engine
Diesel
fuel (.25 liters/BHP/hr)
(.05 liters/BHP/hr)
consumed
X Rs 2.70 = Rs .68
X Rs 2.70 = Rs .14
Lubricating
(.015 liters/BHP/hr)
(.008 liters/BHP/hr)
oil
consumed X Rs 10 = Rs .15
X Rs 10 = Rs .08
Combined cost of diesel
Combined cost of diesel
Total
fuel and lubricating
fuel and lubricating
oil = Rs .83
oil = Rs .22
The total
difference in the combined cost of diesel fuel and
lubricating
oil for a standard diesel engine and for a dual
fuel biogas
engine is Rs 0.83 - Rs 0.22 = Rs 0.61/BHP/hr.
A
dual fuel
biogas engine thus saves Rs 0.61 in fuel and lubricating
oil costs for
each hour it operates.
We know that
0.42 [m.sup.3] of biogas are needed to generate one BHP/hr.
We can use
the following formula to calculate the Equivalent
Diesel
Price/[m.sup.3] (EDP/[m.sup.3]):
(0.42
[m.sup.3] biogas/BHP/hr) X (EDP/[m.sup.3]) = Rs 0.61.
EDP/[m.sup.3]
= Rs
0.61 =
Rs 1.48/[m.sup.3]
Rs 0.42/[m.sup.3]
This shows
that biogas is competitive with diesel
fuel when it
can be sold
at a price no greater than Rs 1.48/[m.sup.3].
This calculation
uses current
prices and assumes that a dual fuel engine
will reduce
by half the amount of lubricating oil consumed.
Surplus gas
sold as electricity. The value of
surplus gas sold
as
electricity is calculated by equating the cost of running a
diesel
generator with biogas with the cost of purchasing a kwh
from the
central grid. We know that 1 BHP = .74
kwh, the running
cost of
operating a diesel engine to produce 1 BHP-hr = Rs
.22 (from
above), and the local cost of electricity is Rs .44/kwh.
Therefore,
the equivalent electricity price (EEP) = (.42
[m.sup.3]/BHP/hr)
x (EEP/[m.sup.3]) + Rs 0.22 = (.74 kwh/BHP) x (Rs .44) = Rs
.25.
The analysis
of an energy or development project is only as
good as the
quality of its assumptions. Many
studies bury these
assumptions
in obscure appendices. Conclusions and
generalizations
made in the
body of such studies are rarely subjected to
a critical
eye; instead, they are taken by the reader as given.
This study
includes the detailed intermediate calculations for
the models to
facilitate the reader's understanding and criticism
of the
simulations. Some of the
notations--such as the use
of the
underline (_) sign--are awkward. They
are written in
this way to
correspond in appearance to the computer printouts
in the
Appendix, which describe the detailed baseline simulation
for all of
the models. Readers not interested in
the mathematical
derivation of
the NPV and payback calculations may
skip to pages
61-62 and skim the left-hand column for a sense
of the key
benefits and costs. Conclusions from
the analysis
begin on page
75.
Table VI-7
shows the notation, including all constant values,
that is used
through the analysis to describe all system variables
for the three
models under each scenario.
Table VI-7 Analysis to Describe All
System Variables
D
=
Total biomass yield per annum, corrected for handling
losses and system down-time as a
function of the Minimized
Cost or Maximized Output scenario.
D_L
=
Diesel required for running a generator set (genset)
per annum:
(.05 liters/hr/BHP) X (3 hrs) X (5 hp) (358
days) = 268.5 liters.
D_LC
=
Cost of the digester, gas holder, and solar water
heater, as a function of system
capacity.
D_P
=
Diesel required for pump operation per annum:
(.05
liters/hr/BHP) X (5 hp) X (20
min/day) X (358 days) =
29.5 liters.
D_RC
=
Diesel required for running the ball mill used to
produce rice cement:
(.05 liters/hr/BHP) X (5 hp) X (2
hrs X (300 days) = 150 liters.
E
=
Cost of all accessories, connections, electrical
wiring, shelters, pumpsets, genset
gas burners, and
miscellaneous equipment, as a
function of tasks to be
performed in the three Models.
G
=
The gas yield of .0475 [m.sup.3]/kg fresh biomass.
G_C
=
Gas required for cooking per annum.
Calculated earlier
as approximately 11,425 [m.sup.3].
G_L
=
Gas required for electric lighting per annum = 2,255
[m.sup.3] biogas (previously
calculated).
G_P
=
Gas required for pumping water = 251 [m.sup.3] (previously
calculated).
G_RC
=
Gas required for operating the ball mill that is used
in the production of rice husk
cement per year: 1,260
[m.sup.3] biogas (previously
calculated).
IA
=
Marginal increase in agricultural income due to nutrient
and humus content of biogas slurry
as a function
of total quantity of organic
material digested, in
rupees/annum.
Though the actual value of IA will fluctuate
due to changing crop yields and
market prices,
IA is treated as a constant for the
sake of simplicity.
L
=
Labor costs at a function of the different models, in
rupees/year.
LO_P
=
Lubricating oil for pumping per annum:
(.008 liters/BHP/hr)
X (5 hp) X (20 min/day) X (358 days)
= 4.7
liters.
LO_L
=
Lubricating oil for lighting per annum:
(.008 liters/BHP/hr)
X (3 hrs) X (5 hp) X (358 days) = 43
liters.
LO_RC =
Lubricating oil for lighting per
annum: (.008 liters/BHP/hr)
X (2 hrs) X (5 hp) X (300 days) = 24
liters.
LO
=
Total annual cost of lubricating oil:
LO P + LO L + LO
RC.
M
=
Material cost (lime) for manufacturing rice husk
cement, in rupees/year.
N
=
The economic life of the system:
15 years.
N_LC
=
Period in which the loan will be amortized:
five
years.
P
=
Cost of distribution pipeline to supply cooking gas:
Rs 10,000.
P_D
=
Unit price of diesel fuel at Rs 2.70/liter.
P-DS
=
Unit price of surplus energy sold as diesel at Rs
148/[m.sup.3] or Rs .74/[m.sup.3].
P-ES
=
Unit price of surplus energy sold as electricity at Rs
.44/kwh, the current rate in
Karnataka, at Rs .2.5/[m.sup.3].
P-FW
=
Unit price of firewood at Rs .04/kg.
P-K
=
Unit prices of kerosene at Rs 2.25/liter.
P-LO
Unit price of lubricating oil at Rs
10.00/liter.
R
=
Revenue from commercial operations--the annual sales
of rice husk cement.
The Pura village operation hopes
to produce 80 tonnes of rice husk
cement per year.
This will be sold at Rs 400/tonne, or
a total of
Rs 32,000.
For the purposes of analysis, the effects
of four levels of annual sales--Rs 0,
Rs 10,000, Rs
20,000, and Rs 30,000--have been
calculated. To
simplify the analysis, revenue is
held constant over
time.
In actuality, it would
fluctuate with demand.
R-LC
=
Interest rate of loan, calculated at both 4 percent
and 10 percent.
***
The following
equations have been used for certain intermediate
calculations:
1.
Annual Recurring Cost Calculations
Capital Cost of System (K)
=
(D___LC) +
P + E
+ the
Amortization
Coefficient (a
function
of N_LC) and (R_LC),
as
explained previously).
Cost of Diesel for Operat-
=
(P__D) X [(D__P) + (D__L) +
ing the System (DF)
D_RC)].
Cost of Lubricating Oil
=
(P__L) X [(LO__L) + (LO__P) +
for Operating System (LO)
(LO_RC)].
Cost of Operation and
=
L + M + Rs 250 (miscellaneous
Maintenance
annual maintenance).
2.
Annual Benefit Calculations
Energy saved from Reduced
=
(P K) X 1,983 liters of
Kerosene Consumption
kerosene saved annually
Energy saved from Reduced
=
(150,000 kg) X (.04 ) X (P_FW),
Firewood Consumption
as explained previously.
Total Gas Produced Annu-
= D X G.
ally (G-T)
Surplus Gas Available
=
(G T) - [(G C) + (G L) + (G P) +
Annually (G S)
(G_RC)].
Sale of Surplus Gas Con-
=
(G_S) X (P DS) X (0.9). The
verted to Diesel
(0.9) is a utilization factor,
since
not all energy produced
would
be used.
Sale of Surplus Gas Con-
=
(G_S) X (P__DS) X (0. 9), as
verted to Electricity
explained above.
3.
Net Benefits--Costs to
=
[Expenditures Saved From Reduced
village
Consumption of Kerosene
and
Firewood + IA + (Sales of
Surplus Energy at either Diesel
or
Electricity Equivalent
Price) +
R] - [Annual Capital
Cost +
Diesel Cost + LO + M +
Rs
250]. Labor costs are excluded
from this
calculation as
explained
earlier. The Rs 250
is for
routine maintenance.
Finally,
although all costs are calculated on the basis of the
system
operating at full capacity, we will assume that there
will be
periodic maintenance delays, and that the system will
not supply
gas every day each year. This will
affect the amount
of surplus
gas available, and will reduce the benefits realized
from fuel
savings of firewood, kerosene, etc. The
daily amount
of biomass
still will be fed into the system, so the IA will
remain
unaffected. Since the rice husk cement
operation runs
only 300 days
a year, the seven-day maintenance is assumed to
occur during
the 65-day slack period. To correct the
calculations
for the
system's "down time," energy saved from reduced
kerosene and
firewood consumption, and sale of surplus gas are
multiplied by
one week divided by 52 weeks = 0.981.
Discussion of
Modeling Results
We are
interested primarily in whether or not the biogas systems
described
earlier enable the village to be "better off."
This is
measured by the positive NPV, as explained earlier.
We
also are
studying whether the systems generate sufficient revenues
to cover
their operating and capital costs, as measured
by the
undiscounted payback period. The
computer program developed
for this
analysis was designed to enable the user to
modify any of
the 27 variables to isolate and examine their
effect on
economic performance. For the purposes
of this
analysis, two
main types of variables were examined.
1.
The interest rate of the loan (R_LC) was
examined at 4 percent
and 10 percent for all models.
2.
The system revenues for the models, the sale
of surplus gas
(P_DS) , and the revenues from the sale of
rice husk cement
(R) were set at various levels.
Revenue from the sale of
gas, available only in the maximum output
scenarios for all
models, was examined at zero, as well as
at the equivalent
price of:
diesel fuel (Rs 1.48/[m.sup.3]), one-half the equivalent
price of diesel fuel (Rs .74/[m.sup.3]),
and the equivalent price
of electricity (Rs .25/[m.sup.3]
Revenue from the sale of rice
husk cement was set in Models 2 and 3 at
zero, Rs 10,000,
20,000, and 30,000. Model 1 has no
provisions for running an
industry.
In addition,
the impact of a hypothetical technological break-through
that somehow
reduces the cost of the digesters by 50
percent (1/2
D_LC) was examined. In this simulation,
interest
rates and
revenues from the sale of rice husk cement vary, as
explained
earlier, and revenues from the sale of surplus gas
are set at
zero and the diesel equivalent.
The results
from these combinations of different interest
rates, sales
of surplus gas, sales of rice husk cement, and
digester
costs are shown in the summary Tables VI-10a through
VI-10d.
Before
discussing the results of this analysis in detail, it
must be
remembered that all the figures are rough and indicative
only of
orders of magnitude. For example, in
evaluating
the NPV
figures, it is most important to note whether or not
the values
are positive and "large," such as more than
Rs 10,000.
This enables us to state with reasonable
confidence
whether a
particular biogas system would provide a village with
a net gain.
Payback
figures need to be viewed more exactly.
As the data
will show,
differences in the loan repayment schedule, amortized
over five
years with a one-year grace period, dramatically
affect the
ability of systems to pay for themselves.
Any
system that
does not repay the loan in the first year, in addition
to covering
its operating costs, will require working
capital from
a source that is external to the biogas system.
Even though
the system pays for itself in the long run, the
cash flow
generated from its operation may be insufficient to
meet
short-term debt servicing, especially through the sixth
year of the
project. Thus, if operations are to
continue, the
deficit must
be offset by an external source of funds.
This
might include
user charges or subsidies, as will be discussed
later.
In this
analysis, the economic life of system components is
held constant
at 15 years for all calculations. The
biggest
source of
error here could be a shorter life of the diesel
engine.
But with proper maintenance and the reduced
deterioration
observed in
laboratory engines run on biogas, an equipment
life of 15
years seems reasonable. Of the 144
cases examined,
there were
seven in which the payback occurred only in the
ninth year or
later. In those seven cases, a 10-year
economic
life for
system components would mean that the project would
not be
financially viable.
The basic
challenge to any village embarking on a large-scale
biogas
project, of course, is to cover the running capital
costs of the
system. Tables VI-8 and VI-9 below show
these
costs in some
detail. The figures in these tables are
taken
from the
detailed baseline benefit-costs calculations found in
the
photocopied computer printouts in the Appendix.
Interest
rates will be discussed in greater depth shortly. However,
if the
capital for the system were borrowed at the higher
rate of 10
percent, the annual cash flow during the repayment
of the loan
would be only 8-10 percent higher than if the money
were obtained
at the preferred rate for associations of 4 percent
(as shown in
Table VI-8). In view of the sum of
money
involved, the
interest is not of great importance.
Table VI-8
Baseline Data:
Annual Operating Deficit (in Rupees)
for Models 1-3 (Full Cost
Digesters)
MODEL 1
Years
Min. Cost
Max. Output
1, 7-15
8,993
8,993
2-6 at 4
percent interest 21,718
23,672
at 10 percent interest
23,936
26,231
MODEL 2
Years[\N
Min. Cost
Max. Output
1, 7-15
18,038
18,038
2-6 at 4
percent interest 32,863
34,458
at 10 percent interest
35,448
37,320
MODEL 3
Years
Min. Cost
Max. Output
1, 7-15
18,038
18.038
2-6 at 4
percent interest 28,258
32,211
at 10 percent interest
30,040
34,683
Similarly, as
shown in Table VI-9, if the costs of the digester
are cut in
half due to a technological breakthrough, the annual
cash deficits
during repayment of the loan range from only 2-11
percent less
than those obtained with the digester at "full"
cost.
Since the other fixed costs of the systems
are so large,
savings
resulting from reducing the digester costs are surprisingly
trivial when
spread over the five-year loan repayment
period.
None of the
systems pay for themselves as a result of cash
savings
derived directly from operations.
Savings "derived
directly from
operations" would include reduced fuel and fertilizer
consumption
expenditures and, technically, any multiplier
effect
stemming from the alternative use of saved capital.
It would not
include revenues from the sale of surplus
gas, surplus
slurry, or products or services provided by industries
run on the
gas. This distinction between savings
and
revenues is
important because the savings will be far less
likely to
fluctuate than revenues, which are affected by market
forces.
Savings will accrue as long as demand,
prices, and system
performances
do not decline. Of the three models
examined,
only model 1
(cooking gas, electric lighting, and village water
pumping)
yields a positive NPV from the direct savings accruing
to the
village over the system's 15 operating years (see Table
VI-8).
The size of the NPV increases slightly for
the systems
with
digesters at half cost. Only in the
case of the Model 3
maximum
output system (with capital borrowed at 4 percent) does
a negative
NPV become positive. Yet even here, the
NPV is an
insignificant
Rs 1,497. Even with no direct revenue
from operations,
11-he Model 1
village gains economically from constructing
the
system. Of course, it may be somewhat
unfair to
criticize a
village system designed to run a small industry
when the
projected revenue from the industry is arbitrarily set
at zero.
However, the critical importance of that
revenue is
underscored
by doing so.
Table VI-9
Baseline Data:
Annual Operating Deficit (in Rupees)
for Models 1-3, with Digester Costs
Reduced 50 Percent
MODEL 1
Years
Min. Cost
Max. Output
1, 7-15
8,893
8,893
2-6 at 4
percent interest 20,213
21,190
at 10 percent interest
22,169
23,316
MODEL 2
Years
Min. Cost
Max. Output[N]
1, 7-15
18,038
18,038
2-6 at 4
percent interest 31,178
31,976
at 10 percent interest
33,496
34,406
MODEL 3
Years
Min. Cost
Max. Output
1, 7-15
18,038
18,038
2-6 at 4
percent interest 27,753
29,729
at 10 percent interest
29,447
31,768
With all
these cautionary notes, we now move to examine the
economic
performance of the biogas systems, using different
levels of
annual revenue obtained from either the sale of
surplus gas
or the sale of rice husk cement (or both).
All data
can be found
in Tables VI-10a through VI-10d below.
Table VI-10a
Net Present Value (NPV) and Payback Period at Different Interest Rates for the
Three Models
With No Revenue
from Sales of Rice Husk Cement
Note:
NPV in rupees is listed first.
Calculations assume a 15-year life of the system.
Payback
period in years is in parentheses. If
the system will not pay back over 15 years, (0) is listed.
MODEL
TWO
MODEL ONE COOKING,
LIGHTING MODEL THREE
INTEREST
RATE BIOGAS
COOKING & LIGHTING
& INDUSTRY
LIGHTING & INDUSTRY
OF THE
LOAN PRICE
Min Cost
Max Output Min
Cost Max Output
Min Cost
Max Output
(R_LC)
(Rs/[m.sup.3)
Model
Model Model
Model
Model
Model
4%
0.00
14,454 33,512
-30,274
-13,902
-44,577 -7,057
(0) (0)
(0)
(0)
(0) (0)
4%
0.25
50,180
680
26,438
(0)
(0)
(0)
4%
0.74
82,849
29,261
92,087
(0)
(0)
(0)
4%
1.48
132,187
72,425
191,231
(0)
(0)
(9)
10%
0.00
6,809 24,692
-39,182 -23,768
-50,718
-15,573
(0) (0)
(0)
(0)
(0) (0)
10%
0.25
41,360
-9,186
17,921
(0)
(0)
(0)
10%
0.74
74,029
19,395
83,571
(0)
(0)
(0)
10%
1.48
123,366
62,558
182,715
(0)
(0)
(11)
4% = Interest
rate charged to associations. 10% =
Higher interest rate.
Rs
0/[m.sup.3] assume no revenues from the sale of biogas; Rs 0.25/[m.sup.3] =
Equivalent price of electricity;
Rs
0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] =
Equivalent price of diesel fuel.
Table VI-10b
Net Present Value (NPV) and Payback Period at Different Interest Rates for the
three Models
With Revenues
of Rs 10,000 from Sales of Rice Husk Cement
Note:
NPV in rupees is listed first.
Calculations assume a 15-year life of the system.
Payback
period in years is in parentheses. If
the system will not pay back over 15 years, (0) is listed.
MODEL TWO
MODEL ONE COOKING,
LIGHTING MODEL THREE
INTEREST
RATE BIOGAS
COOKING & LIGHTING
& INDUSTRY
LIGHTING & INDUSTRY
OF THE
LOAN PRICE
Min Cost
Max Output
Min Cost Max Output
Min Cost Max
Output
(R_LC)
(Rs/[m.suup.3)
Model
Model
Model Model
Model
Model
4%
0.00
45,788
62,159
31,485
69,004
(0)
(0)
(0)
(0)
4%
0.25
76,741
102,499
(0)
(0)
4%
0.74
105,322
168,149
(0)
(15)
4%
1.48
148,486
267,293
(0)
(1)
10%
0.00
36,880
52,293
25,344
60,488
(0) (0)
(0)
(0)
10%
0.25
66,875
93,983
(0)
(0)
10%
0.74
95,456
159,632
(0)
(0)
10%
1.48
138,620
258,776
(0)
(1)
4% = Interest
rate charged to associations. 10% =
Higher interest rate.
Rs
0/[m.sup.3] assumes no revenues from the sale of biogas; Rs 0. 25/[m.sup.3] =
Equivalent price of electricity;
Rs
0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] =
Equivalent price of diesel fuel.
Table VI-10c
Net Present Value (NPV) and Payback Period at Different Interest Rates for the
Three Models
With Revenues of Rs
20,000 from Sales of Rice Husk Cement
Note:
NPV in rupees is listed first.
Calculations assume a 15-year life of the system.
Payback
period in years is in parentheses. If
the system will not pay back over 15 years, (0) is listed.
MODEL TWO
MODEL
ONE
COOKING, LIGHTING
MODEL THREE
INTEREST
RATE BIOGAS
COOKING & LIGHTING
& INDUSTRY
LIGHTING & INDUSTRY
OF THE
LOAN PRICE
Min Cost
Max Output Min Cost
Max Output
Min Cost Max Output
(R_LC)
(Rs/[m.sup.3])
Model
Model Model
Model
Model Model
4%
0.00
121,849
138,220
107,546 145,066
(0)
(0)
(0) (0)
4%
0.25
152,803
178,560
(0)
(12)
4%
0.74
181,384
244,210
(11) (1)
4%
1.48
224,547
343,354
(7) (1)
10%
0.00
112,941
128,354
101,405 136,549
(0) (0)
(0)
(0)
10%
0.25
142,936
170,044
(0)
(14)
10%
0.74
171,518
235,693
(13) (1)
10%
1.48
214,681
334,837
(8) (1)
4% = Interest
rate charged to associations. 10% =
Higher interest rate.
Rs
0/[m.sup.3] assumes no revenues from the sale of biogas; Rs 0.25/[m.sup.3] =
Equivalent price of electricity;
Rs
0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] =
Equivalent price of diesel fuel.
Table VI-10d
Net Present Value (NPV) and Payback Period at Different Interest Rates for the
Three Models
With Revenues of Rs
30,000 from Sales of Rice Husk Cement
Note:
NPV in rupees is listed first.
Calculations assume a 15-year life of the system.
Payback
period in years is in parentheses. If
the system will not pay back over 15 years, (0) is listed.
MODEL TWO
MODEL ONE
COOKING, LIGHTING
MODEL THREE
INTEREST
RATE BIOGAS
COOKING & LIGHTING
& INDUSTRY
LIGHTING & INDUSTRY
OF THE
LOAN PRICE
Min Cost
Max Output Min Cost
Max Output
Min Cost Max Output
(R_LC)
(Rs/[m.sup.3])
Model
Model Model
Model
Model Model
4%
0.00
197,910
214,281
183,607 221,127
(7)
(7)
(1) (1)
4%
0.25
228,864
254,621
(1)
(1)
4%
0.74
257,445
320,271
(1) (1)
4%
1.48
300,608
419,415
(1) (1)
10%
0.00
189,002
204,415 177,466
212,610
(8) (9)
(1)
(7)
10%
0.25
218,998
246,105
(7) (1)
10%
0.74
247,579
311,754
(1)
(1)
10%
1.48
290,742
410,899
(1)
(1)
4% = Interest
rate charged to associations. 10% =
Higher interest rate.
Rs
0/[m.sup.3] assumes no revenues from the sale of biogas; Rs 0.25/[m.sup.3] =
Equivalent price of electricity;
Rs
0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] =
Equivalent price of diesel fuel.
Table VI-11a
Net Present Value (NPV) and Payback Period at Different Cement Revenue and
Interest Rates
With the Cost of the
Digester Reduced by One-half
Note:
NPV in rupees is listed first.
Calculations assume a 15-year life of the system.
Payback
period in years is in parentheses. If
the system will not pay back over 15 years, (0) is listed.
REVENUE
MODEL TWO
FROM
INTEREST
MODEL ONE COOKING,
LIGHTING MODEL THREE
CEMENT
RATE OF BIOGAS
COOKING & LIGHTING
& INDUSTRY
LIGHTING & INDUSTRY
SALES
THE LOAN PRICE
Min Cost
Max Output Min
Cost Max Output
Min Cost
Max Output
(Rs)
(R_LC) (Rs/[m.sup.3])
Model
Model Model
Model
Model Model
0
0.04 0.00
19,641
42,566
-24,468
-5,348 -42,835
1,497
(0) (0)
(0)
(0)
(0) (0)
0
0.04 1.48
141,740
80,978
199,785
(0) (0)
(8)
0
0.10 0.00
12,899
34,737
-32,364 -13,723
-48,672
-5,528
(0)
(0)
(0) (0)
(0)
(0)
0
0.10 1.48
133,411
72,603
192,760
(0)
(0)
(9)
10,000
0.04 0.00
51,593
70,713
33,226 77,558
(0) (0)
(0)
(0)
10,000
0.04 1.48
157,039
275,846
(0) (1)
10,000
0.10
0.00
43,697
62,338 27,389
70,533
(0) (0)
(0)
(0)
10,000
0.10 1.48
148,665
268,821
(0) (1)
4% = Interest
rate charged to associations. 10% =
Higher interest rate.
Rs
0/[m.sup.3] assumes no revenues from the sale of biogas; Rs 0.25/[m.sup.3] =
Equivalent price of electricity;
Rs
0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] =
Equivalent price of diesel fuel.
Table VI-11b
Net Present Value (NPV) and Payback Period at Different Cement Revenue and
Interest Rates
With the Cost of the
Digester Reduced by One-half
Note:
NPV in rupees is listed first.
Calculations assume a 15-year life of the system.
Payback
period in years is in parentheses. If
the system will not pay back over 15 years, (0) is listed.
REVENUE
MODEL
TWO
FROM
INTEREST
MODEL ONE COOKING,
LIGHTING
MODEL THREE
CEMENT
RATE OF BIOGAS
COOKING & LIGHTING
& INDUSTRY
LIGHTING & INDUSTRY
SALES
THE LOAN PRICE
Min Cost
Max Output Min
Cost Max Output
Min Cost
Max Output
(Rs)
(R_LC)
(Rs/[m.sup.3])
Model Model
Model
Model
Model Model
20,000
0.04 0.00
127,654
146,774
109,288 153,619
(0)
(0)
(0) (0)
20,000
0.04 1.48
233,100 351,907
(1)
(1)
20,000
0.10 0.00
119,759
138,339
103,450 146,594
(0) (0)
(0)
(0)
30,000
0.10
1.48
224,726
344,882
(7) (1)
30,000
0.04 0.00
213,715
222,835
185,349 229,680
(1) (1)
(1)
(1)
30,000
0.04 1.48
309,162
427,969
(1) (1)
30,000
0.10 0.00
195,820
214,460
179,511 222,655
(7)
(7)
(1) (1)
10,000
1.10 1.48
300,787 420,943
(1)
(1)
4% = Interest
rate charged to associations. 10% =
Higher interest rate.
Rs
0/[m.sup.3] assumes no revenues from the sale of biogas; Rs 0.25/[m.sup.3] =
Equivalent price of electricity;
Rs 0.74/[m.sup.3]
= One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] = Equivalent
price of diesel fuel.
Model
1--Cooking and Lighting
As discussed
earlier, Model 1 has a positive NPV in both the
minimum cost
and maximum output cases. The size of
the NPV is
larger in the
maximum output case since surplus gas is sold for
profit.
Under the most optimistic conditions--with
digester
costs cut in
half, the highest price obtained from gas sales
(Rs 1.48, the
diesel equivalent), and the 4 percent interest
rate on
borrowed capital--the NPV is Rs 140,740.
Even so, as in
all cases of
Model 1, the system is unable to generate sufficient
revenue to
pay for its annual operating deficits.
These
deficits
range from almost Rs 9,000 for years 1 and years 7-15,
to Rs 20,200-26,200
during the loan repayment years, 2-6.
The
system
therefore would require either a subsidy or user charge
to finance
construction and operation.
Model
2--Cooking, Lighting, and Small Industry
In the
minimum cost case, annual cash deficits range from Rs
18,000 for
year 1 and years 7-15 to between Rs 31,200-Rs 35,500
in years 2-6
(see Tables VI-8 and VI-9). Without
revenue from
the sale of
rice husk cement, the system has a negative NPV and
cannot pay
for itself. When annual sales are
greater than Rs
10,000, the
NPV becomes positive. But it is only
after sales
reach Rs
30,000 per year that the system pays for itself.
The
higher
interest rate only slows payback by one year.
However,
the payback
period is 7-8 years, which still necessitates an
external cash
source. The one exception to this is
the combination
of the half
cost digester with a 4 percent loan, which
pays for
itself during the first year.
If the Model
2 system capacity is expanded to accommodate more
biomass input
(the maximum output case), then the baseline
annual cash
deficits (from Tables VI-8 and VI-9) range from Rs
18,000 in
years 1 and years 7-15 to Rs 32,200-Rs 37,300 in
years
2-6. NPVs are positive if surplus gas
is sold at the
price of
diesel fuel, at half the price of diesel fuel, and, of
course, if
the digester cost is halved and surplus gas is sold
as diesel
fuel. If surplus gas is sold at the
equivalent price
of
electricity and there are no cement sales revenues, the NPV
is barely
positive with a 4 percent loan. It
becomes negative
if the loan
is 10 percent, but reverts back to positive if
sales
revenues are at least Rs 10,000. The
maximum output case
pays back in
7-8 years (depending on interest rates) if revenues
are at least
Rs 20,000 and if the surplus gas is sold at
the diesel
equivalent. It pays back in 11-13 years
if the gas
is sold at
half the diesel equivalent. The system
does not pay
back if the
gas is sold at the electricity equivalent price.
The half-cost
digester case pays back in the first year if revenue
is at least
Rs 20,000, if gas is sold at the diesel
equivalent,
and if the interest rate is 4 percent.
It takes
seven years
if the rate is 10 percent. If revenue
is Rs 30,000
and no
surplus gas is sold, the situation is much like the
minimum cost case.
There is a payback of 7-9 years, or of 1-7
years if the
digester costs are halved. If revenue
is at least
Rs 30,000,
and if surplus gas is sold, the payback occurs during
the first
year. However, there is a seven-year
payback when
gas is sold
at the electricity equivalent and the loan is made
at 10
percent.
Model
3--Lighting and Industry
Based on
annual deficits of Rs 18,038 for years 1 and years
7-15, and of
Rs 27,700-Rs 30,000 in years 2-6, the minimum cost
systems have
positive NPV if revenues from the sale of rice
husk cement
are at least Rs 10,000. They pay back
in the first
year if
revenues are at least Rs 30,000. A
system designed for
the maximum
output case, with either revenue of at least Rs
10,000 or
surplus gas sales (at the electricity or diesel
equivalent),
shows a positive NPV when the baseline annual
deficit is Rs
18,030 in years 1 and years 7-15, and Rs 29,700-Rs
34,600 in
years 2-6.
Payback
periods are more complicated. In the
case of a full-price
digester,
selling surplus gas at the diesel equivalent
without any
revenue from cement sales results in a payback of
9-11 years,
depending on the loan rate. Under
similar conditions,
reducing the
digester cost by half improves the payback
position only
slightly to 8-9 years. Surplus gas sold
at half
the diesel,
or electricity, equivalent does not enable the system
to be viable
financially. If no gas is sold, but
cement
sales are Rs
10,000, none of the systems pay back.
With sales
of Rs 10,000
and surplus gas sold at the diesel equivalent,
payback
occurs during the first year for both the full- and
half-cost
digester systems. With similar cement
sales, but with
surplus gas
sold at half-diesel equivalent, payback occurs only
in the
fifteenth year with a 4 percent loan.
It does not occur
at all at 10
percent or when the gas is sold at the electricity
equivalent.
If no surplus gas is sold, the system does
not pay
back if
revenue from cement sales are Rs 20,000.
At the diesel
equivalent,
and with surplus gas sold in addition to a profit
of Rs 20,000
on cement sales, a system with a full- or halfcost
digester will
pay back in the first year. The same is
true
with Rs
20,000 in cement sales, and the surplus gas sold at the
half-diesel
equivalent combination. On the other
hand, when the
same level of
cement sale is combined with surplus gas sold at
the
electricity equivalent, it only yields a 12-14 year payback.
If cement
sales are Rs 30,000 and no surplus gas is sold,
the system
pays back in either the first or seventh year,
depending on
the interest rate. However, in the
half-cost
digester
case, the same system pays back immediately, regardless
of the
interest rate. The system has a one
year payback
period if
cement sales exceed Rs 30,000, and if surplus gas is
sold at any
of the three prices.
SOME
CONCLUSIONS
Certain
generalizations can be made from the summary data in
Tables VI-10a
through VI-10d:
1.
Of the 144 different ways in which the three
models of biogas
systems might perform, the systems pay
back during the
life of the system in 55 cases (38 percent
of the total). Of
the cases in which payback occurred, 35
(25 percent) had
payback within the first year of the
project's existence.
One-fourth of the cases examined seem
extremely economical
when they have an adequate cash flow.
In addition, only 32
of the 144 cases (22 percent) showed a
negative NPV. This
suggests that the village will show a net
gain from building
one of these systems in almost 80 percent
of the situations
that were modeled.
However, these optimistic findings presume
a source of revenue from the sale of rice
husk cement
or surplus gas.
2.
Half of the 144 cases were examined with a 4
percent interest
rate for borrowed capital; the other half
had a 10
percent rate.
Thirty-two of the 72 cases analyzed at 4
percent interest paid back during the life
of the project.
Thirty-one cases paid back at 10
percent. The one remaining
situation at 4 percent paid back only in
the fifteenth year
of
the project. The remaining eight cases
do not pay back at
all.
Interest rates for borrowed capital do not seem to
affect the total number of projects that
pay back. Twenty
two cases pay back during the first year
at 4 percent while
15
cases pay back during the first year at 10 percent.
The
lower interest rate increases by 10
percent the number of
systems with an immediate payback.
(Thirty percent of the 4
percent situations pay back within one
year versus 20
percent for the higher interest
cases). In most cases, the
higher interest rate extended the payback
period by only one
to two years.
Lower interest rates clearly improve the
chances for a system to pay back
immediately. But, the
number of viable projects is relatively
unaffected by interest
rates.
Viable projects are considered to be those with
those with a means of covering the
deficits occurring prior
to payback, and which require no external
source of cash
during the years of loan repayment.
3.
Of the three basic models examined, Model 1
(cooking, gas
and electric lighting) does not pay back
even when the sale
of surplus gas and digester costs are cut
in half. Model 2
(cooking, lighting, and small industry--rice
husk cement
production) payback occurs in 26 of the 64
possible cases.
Of these, 10 cases (16 percent) pay back
during the project's
first year.
In Model 3 (lighting, rice husk cement
production), payback occurs in 37 of the
64 possible cases
(58 percent).
Of these, 27 cases (42 percent) pay back in
the first year.
Again, the data show the substantial impact
of being able to sell surplus gas and rice
husk cement.
All things being equal, it is more
profitable to maintain a
village system as a public utility and
fertilizer plant than
as a source of cooking gas.
However, such an approach only
is possible in a village in which:
a.
An alternative energy source such as wood from carefully
managed woodlots could be supplied at
an affordable price
to every household in the
village. This is necessary
since the system would take away
people's only cooking
fuel.
b.
An alternative source of animal fodder could be found.
This is necessary because the biogas system reduces the
amount of village biomass available
for fodder. This
might be done by using some of the
biogas slurry to grow
algae or other sources of protein and
roughage. However,
both algae and roughage cultivation,
as well as village
woodlots, will require more project
money, organization
building, and technical support.
These additional costs
might be financed with the profits
from a system with
quick payback. Nonetheless, the
opportunity costs of such
resources cannot be ignored.
Given the greater managerial
complexity and increased
resource demands of Model 3, in most
cases it seems far
more preferable to link a village
system that supplies
cooking gas with either a small
industry or the sale of
surplus gas.
The concept of using a biogas system as an
industrial energy unit deserves
further study in view of
the competitive unit energy costs
derived from even a
village-scale system.
4.
Of the 36 cases pertaining to the minimum
cost models, eight
(22 percent) pay back within the life of
the project and
five (14 percent) pay back within the 15
year project life.
Of these, 32 (30 percent) pay back in the
first year.
Resource opportunity costs, as well as the
problem of
estimating effective demand for surplus
gas and rice husk
cement, bear directly on these
findings. If sufficient
resources and demand exist, there does
seem to be a greater
chance of economic viability with the
larger systems that
can run an industry and provide additional
energy. But it is
essential that this question be examined
in a particular
village with its unique set of
opportunities and
constraints.
5.
The minimum cost Models (both 2 and 3) that
run an industry
must realize income of at least Rs 30,000
during the period
of loan repayment if they are to be
viable, even if digester
costs are halved (see Tables VI-8 and
VI-9). Payback occurs
in eight of 24 cases.
Of these, five pay back in the first
year.
The case that comes closest to modeling the expected
performance of the Pura system (full-cost
digester, no sale
of surplus gas) shows a payback of 7-9
years, depending on
interest rates.
This result is interesting because it does
not assume that
capital would be provided free of charge, as
the Karnataka State Government is doing
for Pura. Nonetheless,
the
project would need assistance during the loan
repayment years to cover the operating
deficit that would
occur during that period.
6.
In the 18 maximum output cases for each of
the Models, surplus
gas was set at different prices to examine
the effect
of those prices on economic
performance. At the equivalent
price of diesel (Rs 1.48/[m.sup.3]), 12
cases (67 percent) pay back
during the life of the project.
Eight of these (44 percent)
pay back during the first year.
Setting the price at one-half
the diesel equivalent (Rs .74), nine cases
(50 percent)
pay back.
Six of these (30 percent) pay back in the first
year.
As one would expect, the lower price of
the electricity
equivalent (Rs .25/[m.sup.3]) yields only
six cases that paid back
(30 percent), and of these, only three
paid back in the
first year (17 percent).
In each of the models, the price of
surplus gas interacts with the different
sales levels of
rice husk cement.
In 75 percent of these cases, payback
occurs only if cement sales exceed Rs
20,000. Systems that
sell gas at half the equivalent price of
diesel fuel perform
surprisingly well when compared to those
that sell gas at
the full diesel equivalent.
Making energy available at half
price might well attract certain
small-scale industries to
rural areas.
However, quantities of surplus gas are limited
since a village must use most of the
available biogas to
meet basic cooking, pumping, and lighting
needs.
7.
The effect of cutting digester costs in half
was studied,
assuming that surplus gas sold at the
diesel equivalent in
the maximum output system.
Of the 54 cases examined, digesters
at full cost paid back in 20 instances (40
percent of
the total).
Half-cost digesters also paid back in the same
20 situations.
Full-cost digesters paid back during the
first year in 11 of these cases (20
percent). Half-cost
digesters paid back during the first year
in 15 (28 percent)
of these cases, a slight improvement over
the more expensive
design.
This suggests that, based on the limited number of
systems examined here, there may be only
limited justification
in devoting a great deal of effort towards
reducing
digester costs.
The effect of cutting digester costs in a
large-scale system is marginal unless the
"fixed costs" of
labor, diesel engines, generators, and the
gas pipeline are
also reduced.
Even if one could assume that 56 individual
family-scale plants could be built at Rs
500 each, and if
labor were free, the costs of installing
these plants to
provide cooking gas and gas lighting
easily would approach
Rs 31,000.
This is not much less than the Rs 43,000 proposed
for
Model 1. It also ignores the problems
of providing an
adequate supply of water for mixing with
the biomass and
resolving struggles over "dung
rights" that might occur with
family-size plants.
This analysis
by no means exhausts all the possibilities of
various
system components. In particular, there
are two possible
sources of
revenue that have not been included:
user
charges, and
returning to the project a portion of income
raised from
increased agricultural yields. Due to
the historical
reluctance of
many villagers to pay for cooking gas that
substitutes
for energy that was perceived as "free," it seemed
sensible to
first examine the conditions under which biogas
systems might
pay for themselves. Similarly, given
the uncertainties
surrounding
the magnitude of increased agricultural
productivity
that would be attributed to a biogas system, the
effects of
returning to the project a portion of any marginal
increase in
agricultural income were excluded from our calculations.
Still, one can
speculate about the impact of including
these
potential sources of revenue.
From Table
VI-8, we know that the annual operating deficit for
the maximum
output Model 1 system is Rs 8,993 in years 1 and 7-15,
and Rs
23,672-Rs 26,231 in years 2-6, depending on the
interest rate
charged on borrowed capital. If Rs
4,000 of the
Rs 8,100
expected increase in agricultural income were somehow
returned to
the project, the annual operating deficit would be
cut to Rs
4,993 in years 1 and years 7-15 and to Rs 19,672-Rs
22,231 in
years 2-6. If these deficits somehow
were divided
among the 56
families, the average cost per family would be
approximately
Rs 7.50 per month (Rs 90 per year) for years 1
and 7-15,
which seems quite affordable. The
average costs during
the period of
loan repayment still would be prohibitive (Rs
397 per year
per family). This figure might be a
justification
for a
government grant for the cost of system construction.
Since we know
that operating costs can be covered by the village,
and the system
can sell surplus gas at the diesel equivalent,
the annual
revenue would increase by (26.7 [m.sup.3]/day) X (358
days/yr) X
(0.9 utilization factor) X (Rs 1.48/[m.sup.3] Diesel
Equivalent
Price), which equals Rs 12,730. If a
little over Rs
5,000 of the
increased agricultural revenue were returned to
the project,
the average user charge per family would be about
Rs 100 per
year during the period of loan repayment (years
2-6).
At all other times, the system would show a
profit. We
have not
discussed the willingness of villagers, especially
larger land
holders, to return a portion of their increased
income to the
project.
If nothing
else, it should be obvious that the question of
whether or
not village-scale biogas systems are economic is one
of considerable
complexity. Under certain assumptions,
the biogas
systems
analyzed here seem to perform well.
These assumptions
are related
to two types of demand:
1.
Rural Energy Demand.
Would villagers be willing to pay user
charges for gas used for cooking and
lighting? Would small-scale
industries purchase surplus gas if it were
sold at
prices competitive with diesel fuel and
electricity?
2.
Small-Scale Industries Demand.
Which goods and services
could be produced by small-scale industries
that are powered
by biogas?
Could these goods and services be sold in sufficient
quantitites to provide biogas systems with
needed revenue?
We know very
little about these questions, although the methodology
exists for
deriving some empirical answers.
Increased
knowledge of
rural capital flows and distribution is desperately
needed to
determine both the priority that villagers
ascribe to
rural energy systems and the economic viability
of these
systems. This is only another way of
stating the
obvious,
which is that rural energy problems cannot be separated
from the
problem of development within a larger political
economy.
VII.
Village Utilization
As shown in
the previous section, the economics of a village-scale
biogas system
can be deceptively complex. Yet of all
the
various
aspects of biogas systems, the least studied is perhaps
the most
important: how do such systems affect
people's lives?
The
experience with biogas systems to date sheds little useful
information on
this question. The Chinese claim that
they will
have
installed as many as 20 million biogas plants by the end
of the early
1980's--depending on which of the various estimates
one
reads. Technical teams sponsored by the
UN; the
Intermediate
Technology Development Group (ITDG), London; the
International
Development Research Center (IDRC), Ottawa; and
others all
have reported observing or hearing about "large"
biogas
systems. These usually are connected to
an institution
such as a
dairy or school. There is no detailed
study available
that
documents the existence and performance of an integrated
Chinese
biogas production and distribution system that is used
by an entire
community. In fact, the Chinese
experience seems
to be
distinguished by a reliance on individual family ownership
and
maintenance of biogas systems, although the labor,
biomass, and
delivery of construction materials may be provided
"free"
by a communal production brigade.(79)
Even in
China, there is little information available on the
number of
biogas plants actually working versus the total
number
installed, nor on the performance levels of the working
systems.
S.K. Subramanian, discussing the efforts of
other
Asian
countries, says that while some nations report the
installation
of tens of thousands of systems, the systems are
almost
exclusively small-scale family plants.(80)
For many
years prior to the watershed 1973 oil embargo, the
KVIC served
as an undaunted promoter of biogas systems in
India.
Progress since then has been slow but
steady. At the
close of the
fifth Five-Year Plan in 1980, KVIC claimed to have
installed
80,000 family-sized systems in India.
There is no
reliable data
on how many of these plants are actually in operation.
An estimate
of 50-75 percent was made by several independent
observers
contacted during the preparation of this
study.
Despite the fact that the KVIC has trained
more than
2,000 people
to provide technical assistance throughout India
as part of a
youth self-employment project, biogas plant owners
frequently
complain about poor servicing and inadequate access
to technical
information. Some of the problems of
drum and pipe
corrosion,
clogging and scum build-up, and low gas yield are
undoubtedly
due to faulty management, improper maintenance, and
insufficient
amounts of biomass fed into the digester.
Yet,
because so
little effort has been mounted to popularize biogas
systems, and
because travel budgets for technical personnel are
so meager,
plant operators are rarely informed about solutions
to technical
problems.
The
government subsidy program designed to stimulate the adoption
of biogas
systems is cumbersome and, to a certain extent,
regressive.
Plants with a capacity of more than 6
[m.sup.3] presently
are
ineligible for any direct subsidy since they are considered
quite
economical. The result is that
wealthier farmers who own
the three or
more cattle currently necessary to operate a small
system can
receive a subsidy, whereas a village project that
would benefit
rich and poor alike is ineligible.
Though the
specific
terms of the subsidy have varied over the last several
years, the
current program is based on a central government
grant alloted
to the state governments. State
governments
actually
manage the program by determining the specific guidelines
that will be
followed. In general, 20-25 percent of
the
system
installation cost is subsidized. Fifty
percent of the
cost
generally is borrowed at 9-12 percent interest, payable
over three to
five years. The remainder is paid in
cash by the
user,
although the relative size of the loan and down payment
vary.
Subsidies usually go directly to the bank to
reduce the
size of the
loan or to act as collateral. Few state
governments
have
authorized designs other than the expensive KVIC model as
eligible for
the subsidy. The government of Uttar
Pradesh has
approved the
Janata system, but most other state governments
are not aware
of the fixed-dome design. Plants using
night soil
also are
ineligible. Delays of one year in
obtaining the subsidy
are common.
Many banks do not have a competent staff to
manage the
program. An informal sample of several
banks in
Madras
revealed that even the chief agricultural loan officers
knew very
little about biogas systems and the subsidy program.
The Chinese
and, to a lesser extent, the Nepalese biogas programs
are managed
by local or regional organizations that were
established
specifically to help coordinate funding for and
provide
technical assistance to biogas system construction and
operation.
The Chinese seem to have linked regional
extension
organizations
with macro-level planning bodies so that sufficient
capital and
construction materials are generated to fulfill
production
targets. In addition, an extensive
promotional
campaign
using radio broadcasts, permanent exhibitions, films,
and posters
is used to generate interest in biogas plants.
Finally, the
Chinese social structure seems to lend itself to
the rapid
diffusion of biogas technology. The
traditions of
waste
recycling and collective effort are strong.
The system of
government
eliminates the need to appeal to individual families
if the
communal leadership accepts an idea. An
effective extension
system, in
which people are trained to construct and
operate
biogas plants and then help train others, generates
technology
dissemination by "chain reaction."
At the same time,
a
decentralized research and development system appears to have
encouraged a
great deal of autonomous local innovation.
Funds
presumably
were provided for local experimentation with different
biogas system
designs.(81) Other countries would do
well to
study the
particulars of the Chinese experience to judge more
accurately
which aspects of China's biogas development program
could be
adapted to different socio-cultural settings.
The Biogas
Corporation, a public/private sector company in
Nepal,
guarantees system performance for five years and does
its own
installation. The Agricultural
Development Bank of
Nepal
provides loans at six percent.
In sharp
contrast to both the Chinese and Nepalese programs,
the Indian
effort has been fragmented among the KVIC (which
also is
charged with promoting more than 20 other small-scale
industries),
the Ministries of Agriculture and Rural Reconstruction,
State Khadi
Gramodyog (village industry) Boards,
banks,
contractors and builders, state agricultural departments,
and
agro-industries corporations. It is
remarkable
perhaps that
the Indian program has achieved even its modest
success(82)
despite the serious problems of inadequate technical
assistance,
cumbersome financing procedures, and overlapping or
conflicting
institutional jurisdictions.
The KVIC has
proposed a program to reach the 12 million families
who own
sufficient (three to five) cattle to operate a
family-size
biogas system. The KVIC believes that
regional mass
production of
prefabricated ferrocement digester/gasholder
segments
could significantly lower the costs of small-scale
systems.
Even assuming that individual families pay
for
installation
and operation of their own systems so that the
government
does not have to subsidize biogas systems directly,
and also
assuming that the overhead costs (including subsidies,
credit
facilities, technical assistance, and staff requirements)
to the
government for a large-scale biogas manufacturing
program are
only Rs 100 per family, the total overhead costs of
such a
program could easily approach Rs 120 crores ($156
million).
Such a
program raises a number of important questions regarding
the equitable
use of scarce capital and the effects of such a
program on
rural income distribution.
Dung is a
source of both fuel and income for the poor who, in
addition to
using dung they are able to find for cooking and
space
heating, also sell dung to generate a meager income.
If
"free"
dung becomes monetized, then the poor, who will not have
access to
family-scale systems, may be deprived of both income
and
fuel. It may be possible to lessen the
cattle-ownership
constraint by
a combination of solar heated digesters and the
use of
biomass other than dung. However, the
capital costs and
land
requirements of these systems would still be beyond the
means of the
vast majority of poor village families.
The KVIC
scheme also raises the question of tradeoffs between
centralized
versus decentralized fabrication of biogas plants.
It is
possible that both rapid installation and quality control
would be more
easily accomplished if units could be mass-produced.
The
possibility does exist for production economies
of
scale. Yet, a more decentralized
approach, in which individual
villagers
would become skilled in and develop a business
from building
and operating biogas systems, might generate far
more
employment, consume less steel and cement, and rely more
on local
materials that are renewable and have a low opportunity
cost.
Furthermore, it would be likely to foster
greater
rural
self-reliance and innovation, reducing the potential for
bureaucratic
delays, corruption, and infrastructure obstructions
that often
plague large-scale, centrally directed projects.
The challenge
of a decentralized scheme is how to
develop
effective ways of providing technical assistance and
financing for
these systems. Some suggestions for
such a
program are
contained in the conclusion of this study.
As biogas
systems become more dependable and less expensive,
the task of
defining the appropriate role of the government in
promoting
them assumes greater importance. It is
possible that
a
government-sponsored production effort might itself become an
obstacle to
the large-scale use of biogas systems.
The most
immediate need in the development of biogas systems is
to gain
considerably more experience with actual village-scale
systems.
There have been several attempts to develop
such systems
in
India. One of these in Kodumenja
village, Karimnagar
district,
Andhra Pradesh, was sponsored by the Rural Electrification
Corporation,
Limited, and the Indian Council of
Scientific
and Industrial Research (CSIR). The
system consists
of a ring of
24 interconnected ferrocement floating-drum
digesters,
with a total capacity of 128 [m.sup.3].
It is designed to
provide
cooking gas and lighting for 60 families, and to operate
five
pumpsets. The system's capital costs
are more than Rs
1.25 lakhs
($15,625). There have been many
problems with the
ferrocement
domes cracking due to improper fabrication, and the
defective
domes have been replaced. As of May
1980, however,
the system
was operating at only half its capacity because the
village was
in the midst of a political feud. Half
the population
refused to
contribute dung to support a system that would
also benefit
their rivals.
Another
community-scale plant in the village of Fateh Singh-Ka-Purva,
Bhagayanagar
Block, near Ajitmal, Etawah District, Uttar
Pradesh, was
designed and installed by PRAD with a grant from
UNICEF.
The system required a capital investment of
about Rs
1.65 lakhs
($20,625) for two plants of 35 [m.sup.3] and 45 [m.sup.3] respectively,
a dual fuel 5
hp engine, a generator, gas distribution
pipeline,
cooking burners, electrical wiring, and miscellaneous
equipment.
The 80 [m.sup.3] system was to have provided
cooking and
lighting
(electric) for 27 households (177 people) in addition
to running
pumpsets, a chaff cutter, and a thresher.
Fatah
Singh-Ka-Purva is an unusual village in that the residents
are
relatively comfortable economically.
Almost every
household
owns land, and income is distributed rather evenly.
The villagers
are of the same occupational caste (shepherds),
and were
enthusiastic about building the biogas system.
The
spatial
layout of the village is such that all households are
clustered
around one or two areas, which simplifies gas distribution
53p86.gif (600x600)
(see Figure
VII-1). Finally, the village initially
had
an unusually
high cattle to family ratio (4:1), compared to the
national average
of 2.5:1.
The
advantages Fateh Singh-Ka-Purva enjoyed due to its socio-economic
conditions,
the technical competence of PRAD, the
financial and
organizational assistance of the local and state
government
authorities, and the good offices of UNICEF all were
cast aside
somewhat rudely by the unpredictable changes of
nature.
A serious drought resulted in the death or
forced sale
of a number
of cattle, reducing the cattle population by almost
13 percent
(from 117 to 97). This reduced the
amount of dung
available to
the system. The system continues to
struggle just
to meet
cooking and lighting needs. It will not
be possible in
the immediate
future for the biogas system also to run
machinery.
During the
author's visit, a substantial number of dung cakes
were observed
drying in the sun. Ironically, they
were spread
around the
southern exposure of one of the digester bases.
The
residents of
the village are not contributing the required
amount of
dung, perhaps 30 percent less than needed.
Some villagers
seem to
prefer the taste of milk when it is slowly
boiled over
the more diffused heat of dung cakes.
Similarly,
the cooking
of rotis, a kind of thin fritter, requires special
burners to
distribute heat over a broad surface area.
People
are sometimes
inconvenienced by the fixed timings of gas
release,
restricted to two hours in the morning and two hours
in the
evening, especially if they have to work late in the
fields.
Some fuel is saved to heat water for
bathing, washing,
and cooking,
especially during the winter months when gas production
falls anyway
due to the effect of lower temperature on
microbial
digestion. Finally, the author also
observed some
frustration
on the part of the site engineer who, having left
the project
for two weeks, found certain tasks uncompleted or
improperly
executed. This seems to be related to
village
politics;
some families do not support the president of the
project
"association."
Both these
community systems distribute cooking gas freely.
Slurry is
distributed proportionately on the basis of per-household
contribution.
People are reluctant to pay for lighting,
which is not
perceived as a real need. Since cooking
fuel
formerly was
"free," they are unwilling to pay for it now even
though biogas
is more convenient and cleaner.
Villagers, while
enthusiastic
about the potential of the system, also have the
political
accumen to realize that these projects are really not
theirs.
They see that the systems are the showpieces
of scientists
and
development agencies that cannot afford to let the
projects
fail. When a central government team
visited Fateh
Singh-Ka-Purva,
villagers inquired what else could be "given"
to them
similar to the biogas plant. No mention
was made of
paying for
additional services. The incentive to
assume
managerial
and operational responsibility for these projects is
simply
lacking on the part of the villagers, and eventual self-sufficient
management
seems problematic.
Neither
system is financially viable, in terms of cash flow,
net present
value calculations, or other economic performance
measurements.
In fairness to these projects, it must be
remembered
that they
were pioneering efforts designed to demonstrate
the technical
feasibility of village-scale biogas systems.
They
also are
intended to help technologists and planners understand
some of the
impact of this technology on village life.
These
goals were
accomplished. While the analyses of
economists are
helpful in
developing analytical methods and generating useful
data on
village household energy consumption patterns,(83) any
criticism of
these particular projects on economic grounds,
even if only
implied, seems somewhat unfair. By
contrast, the
ASTRA system
under construction in Pura village is designed to
be both
profitable and self-sustaining. As
such, it represents
the next
logical and necessary step in the development of village
biogas
systems.
Two of the
largest village systems yet attempted in India, each
with a daily
capacity of about 200 [m.sup.3], are under construction
in the Gujarati
villages of Khoraj, Gandhigram District, and
Khubthal,
Ahmedabad District. These systems are
based on the
ASTRA-modified
KVIC design, which includes the solar water
heater.
Designed and constructed, and to be managed,
by the
Gujarat
AgroIndustries Corporation, both systems will supply
more than 100
families in each village with gas for cooking.
Biomass
inputs will include dung, human wastes from a community
latrine, and
agricultural residues. According to the
unpublished
feasibility
report, families will have to pay to connect
their homes
to the main gas pipeline. In addition,
all dung
will be
purchased, slurry will be sold, and villagers will have
to pay for
the gas. Both systems require an
investment of just
over Rs 2
lakhs ($25,000) each. These systems
will receive subsidies
from the
state government for approximately one-third of
this
investment cost. It will be interesting
to monitor the
progress of
these projects, especially the willingness of the
villagers to
pay for gas, the performance of the systems and
community
latrines, and the long-term financial viability of
the systems.
Technical
Questions
Based on what
we know about biogas systems, a number of problems
must be
resolved before a program can be disseminated on a
large
scale. Relatively little data exists on
the net energy
needed to
prepare particular meals, nor on how this is affected
by
agro-climatic variations, income levels, and local customs.
Such
information is necessary to determine the required
capacity of a
biogas system in conjunction with whatever other
operations
are fueled by the biogas. More
information is needed
on the most
efficient stove and burner designs, and on the
effect of
different types of cookware materials on gas use.
One of the
few benefits of the inefficient and often smoky
chulahs is
that the smoke or odor aids in controlling mosquitoes
and
termites. Use of a clean burning fuel
such as biogas
might upset
this balance. It may be that biogas
systems can be
introduced in
certain local situations only in conjunction with
different
housing construction techniques or pest control
measures.
Slurry
handling and distribution can be both time consuming and
annoying.
Villagers express little interest in
contributing
free labor to
biomass collection and slurry mixing, although in
Fateh
Singh-Ka-Purva they do assist in the delivery of slurry
to individual
compost piles, central storage pits, or crop
lands.
A large-scale community plant run on a
continuous basis
produces more
slurry than can be used daily; convenient storage
facilities
must be provided. Alternative means of
handling biogas
slurry
require further research within the context of village
skills and
capital constraints. These include
possible
mechanized
distribution, direct application of manure versus
"seeding"
existing compost pits, or incorporation into integrated
feed/fertilizer/fuel
systems such as algae ponds,
pisciculture,
etc.
Water and
land use requirements of biogas systems can be substantial.
Large-scale
underground plants can reduce land
requirements
unless plants are covered by a solar pond.
Villagers
will have to
assess the opportunity cost of land occupied
by a biogas
system. Community biogas technical
teams have
in the past
viewed the free donation of land and water for biogas
systems as a
kind of litmus test of a village's commitment
to the
system. This may not be an unreasonable
approach, but it
should not be
assumed that land and water will always be available
or close
enough to points of use to prevent high distribution
costs.
In addition, ways to recycle the water and
reduce
the system's
water demand, currently almost equal to the weight
of biomass
added, need to be developed. Finally,
the spatial
distribution
of huts, sheds, wells, etc., in many villages may
increase gas
distribution costs dramatically. This
is due to
both the cost
of the pipe and to the need to compensate for
pressure
losses over long distances. These
distribution concerns,
coupled with
villager complaints about the inconvenience
of fixed
timings for the release of gas for both cooking and
lighting,(84)
suggest that alternative techniques for the decentralized
storage of
gas need to be investigated. Storage
sacks
with a
compressible inner bag to maintain sufficient gas
pressure
could be developed. Safety
problems--the danger of
explosion due
to puncture--and of practical storage volume need
to be
surmounted. The potential advantages of
a more decentralized
system have
been discussed earlier.
Of course,
these technical questions are in addition to numerous
other areas
requiring further research and development, as
discussed in
Section III. These include the use of
agricultural
and forest
residues, the merits of fixed-dome versus floating-drum
and plug-flow
designs, the relative importance of constant
gas pressure,
and ways to increase gas production throughout
the year.
Financial
Viability
The most
obvious economic challenge to community biogas systems
is to make
them viable financially. The economic
analysis of
the previous
section shows that, given the reluctance of villagers
to accept
user charges, community biogas systems will
have to find
some other way to generate revenue or "cross-subsidization,"
even with
significant cost reductions and
improved
system performance. Alternatives could
be in the form
of a
"subsidiary" commercial operation or the direct sale of
surplus gas
to a small-scale industry. As was
mentioned
earlier,
speculating on potential revenues is a far cry from
actually
generating rural industrial energy demand.
In fact, it
is unclear if
the increased availability of inexpensive energy
would be a
sufficient stimulus to generate rural industries.
Community
biogas systems somehow must demonstrate that external
revenue
sources will materialize as expected.
Whether or not
lending
institutions develop confidence in such assessments
remains to be
seen.
The
difficulty in getting villagers to accept user charges will
vary from
village to village. Villages spending a
significant
proportion of
the "village product" on energy will naturally be
less
resistant to some of the progressive pricing schemes suggested
by Parikh and
Parikh and by Moulik and Srivastava.(85)
These authors
suggest various pricing policies that combine
higher unit
prices for wealthier families, and either "free"
(subsidized)
community cooking and latrine facilities or the
allocation of
gas on the basis of free labor contributions by
the
poor.(86) These sensible pricing
policies rely on a series of
untested
assumptions regarding the detailed keeping of records
and monitoring
of consumption that would be required to make
such systems
work. Furthermore, in many if not most
villages,
biogas is a
substitute for what villagers perceive to be "free"
fuels:
dung, agricultural residues, or even
firewood. Admittedly,
such a
perspective may seem somewhat shortsighted given
deforestation,
population growth pressures, and the high cost
in time to a
woman who has to walk for hours to gather fuel.
But it is
difficult for a villager to justify paying for something
that can be
obtained at the low cost of his, or more
likely, her
labor.
This outlook
raises a much larger question concerning the perception
of both
villagers and economists regarding the utility
of investing
scarce capital in energy systems. Are
village
energy projects
a response to clearly stated village demands,
or are
potable water, adequate shelter, an affordable supply of
food, and a
sufficient income to release a family from
perpetual
debt perceived as more important? The
problem of
"what is
to be done" certainly will vary from village to village.
It probably
even varies from season to season. The
village
energy
bandwagon should be jumped on first by villagers,
and only then
by economists and planners.
The overall
effect of biogas systems on the local distribution
of income is
unknown. Bhatia and Nairam found that,
as one
would expect,
energy consumption increases with income.
Even in
a relatively
homogeneous village such as Fateh Singh-Ka-Purva,
free cooking
gas increases discretionary income the most for
those with
the most income.(87) Some potentially
harmful effects
already have
been mentioned. Dung currently is sold
by members
of the lower
castes to earn a meager income. A
biogas system
might take
away that income source from them.
Furthermore, an
increased
demand for dung or crop residues might deprive the
poor of
fuel. In addition, people who own more
land and cattle
clearly will
benefit more from a proportionate distribution of
biogas
slurry. One could even speculate that,
over time,
increased agricultural
productivity, energy, and income might
make it
possible for wealthier villagers to substitute capital
for labor,
gradually mechanizing their agricultural operations,
and
displacing some farm laborers.
While no one
would deny the serious threats posed by deforestation,
it is by no
means clear that such ecological damage is
always caused
by the increasing rural demand for cooking fuel.
While this
undoubtedly may be an important cause in many
specific
areas, discussions with staff in the Ministry of
Forestry
revealed a great deal of uncertainty about whether it
is the main
one. For example, some large
construction firms
allegedly do
not report the full number of trees they cut,
harvesting
more than they are allowed by permit.
Finally,
there has been no attempt to assess the costs of providing
the technical
assistance, servicing, financing mechanisms,
and
performance monitoring that would have to be an
integral part
of any large-scale biogas promotion program.
These
overhead costs will occur regardless of whether a large-scale
program
creates the decentralized, "spontaneous" adoption
advocated by
many village technology groups, or the large,
centrally
coordinated, mass-production and installation programs
favored by
some in government and industry. The
high
costs of even
unprofitable experimental village systems can
only heighten
apprehension on this point. The goal of
research
and
development efforts must be to generate system designs that
will minimize
the dependence of villages on outside money,
material, and
technical assistance.
Sociological
Questions
The paucity
of sociological, anthropological, and organizational
analyses,
even of the two community systems discussed
earlier,
makes any treatment of such questions a matter of
speculation.(88)
Perhaps the most basic concern is the extent
to
which a real
sense of community exists in villages where biogas
systems are
installed. It is clear that many
villages are in
fact
"communities," i.e., they exhibit a shared sense of values
and goals, have
cooperative networks that enable the ebb and
flow of daily
events to occur reasonably peacefully, and enjoy
a sense of
trusted or accountable village leadership.
However,
many villages
are less fortunate. Village life can be
quite
tempestuous,
with an abundance of rivalries and struggles
related to
the rights of caste, marital or family discord, and
indebtedness.
For example, it remains to be seen if people
of
one caste
will always be willing to consume gas distributed by
the same
pipeline that is used by lower castes.
There already
is evidence that a serious political feud has
effectively
curtailed the operation of the village system in
Kodumunja.
To a lesser extent, factionalism also is
operating
in Fateh
Singh-Ka-Purva. This form of protest or
manipulation
could
seriously affect the cash flow position of a particular
system,
especially if loan payments are outstanding or if the
biogas system
is linked to one or more external commercial
operations.
If such a disruption, caused either by the
withholding
of organic
raw material or by outright sabotage, continues
for a long
time, the long-term financial viability of
the system
and its dependent industries could be threatened.
A
related point
is how rugged or durable biogas systems need to
be to survive
in the village, and how this affects costs.
An attitude
of either cooperation or obstruction may prevail,
depending on
the relationship of different interest groups to
the flow of
benefits derived from the operation of the biogas
system.
A political minority might want to prevent
those in
power from
receiving praise from villagers for successfully
operating a
biogas system. Such behavior has been
observed in
successful
attempts to block the construction of irrigation
canals that
clearly would have benefited a village as a whole.
The costs of
potential loss of political power resulting from
the
construction of the canal were perceived by the victorious
opposition as
far greater than whatever gains would have been
realized with
the canal's operation. In addition, the
detailed
record
keeping necessary for the technical and economical operation
of the system
would have conferred a great deal of power
and
responsibility on the plant supervisor.
The range of potential
abuse of such
power has not been examined in this study
since the
dedicated efforts of the technical teams involved in
the current
village projects effectively preclude malevolence
and
corruption. However, such individuals
may not always be
present in
many villages. The dependence of the villagers
on
the ethical
conduct of the system manager creates the conditions
for
abuse. Some system of making
supervisory personnel
accountable
to the villagers clearly is essential.
This might
be done
through the Panchayat governments; however, even the
record of
these bodies in safeguarding the interests of the
poor is mixed
at best.
If villagers,
especially women, spend a good portion of their
day
collecting fuel and cooking, a biogas system could create a
fair amount
of leisure time. It is not clear how
this would be
viewed and
utilized by villagers. Many benefits of
a biogas
system will
be most attractive to women: ease and
cleanliness
in cooking,
freedom from smoky kitchens and associated eye and
respiratory
diseases, and freedom from tedious grinding,
threshing,
and chaffing operations that could be mechanized
with the use
of dual fuel engines. Will men agree
that these
benefits are
desirable? It is unclear how much influence women
enjoy over
major investment decisions in the family.
This could
be an
important consideration in promoting or marketing biogas
systems.
The ability
of villagers to accept the concepts of collective
ownership and
communal living will vary. Collective
ownership
of the land
occupied by the biogas system, as well as of the
system
itself, cannot be taken for granted.
Similarly, people
may or may
not respond positively to community kitchen and
latrine
facilities. Community latrines pose
special complications.
First, the
flow of water from the latrines to the system
somehow must
be regulated so as not to result in excessive
dilution of
the biomass fed into the system.
Second, the ritual
of walking to
the field early in the morning is one of the few
times during
the day when women find the privacy to socialize
among themselves,
free from other responsibilities. This
may
also be true
for the time spent collecting firewood.
It is not
clear that
these practices will be discontinued easily.
Finally, some
people view biogas, and "appropriate technology"
in general,
as an agent of social change. They
reason that
because these
technologies require a great deal of both stewardship
and
cooperative action on the part of users, the introduction
of
appropriate technologies will foster the necessary
behavior and
attitudes, even if these are outside the villagers'
own
experience. Such "technological
determinism" may
indeed exist,
and there certainly are examples of it.
However,
the critical
question remains: to what extent can a
technology
be
"beyond" the present village culture and still be adopted by
the villagers
without causing undesirable socio-economic
effects?
Given that there is resistance to change,
who will
decide that
"this" technology is in fact appropriate for
"these"
villagers, or that the social change required by a
technology is
desirable? Biogas systems affect some
basic
aspects of
village life: the distribution of land,
water,
fertilizer,
fuel, and income. It remains to be seen
whether
biogas
systems can be adopted on a large scale without a political
struggle to
secure equitable access to these resources.
These
choices, if they are in fact choices, force us to confront
the
"appropriateness" of biogas systems.
After much more
experience
with these systems, we might be in a position to
evaluate
biogas systems as a whole, voicing a collective
approval or
disapproval. But at this stage of
development, such
a
pronouncement is unwise and potentially destructive.
The problem
of actually introducing a technology, such as village-scale
biogas
systems, is one of staggering complexity.
No
one has
analyzed fully how to transfer such a technology from
the
laboratory to the village as a necessary phase of research
and
development. It often is assumed that
once technical problems
are solved
and biogas systems can pay for themselves on
paper,
villagers will accept biogas because it is a good idea
whose time
has come. For example, there is an
extremely dedicated,
private group
of village energy specialists and biotechnologists
who are
working in a number of Tamil Nadu villages.
This group
has worked closely with a particular village for
several years
and still has a difficult time convincing certain
families to
experiment with small family-scale digesters.
The
families
agree that biogas is a good thing, but are engaged in
a highly
profitable, but illegal, venture, producing arrak (a
strong
alcoholic beverage) and selling it in Madras.
These
families feel
that their lives are progressing quite nicely and
seem
threatened by the presence of outsiders pushing biogas
systems.
Far too little attention has been devoted
towards
understanding
under what conditions villagers will actually use
biogas
systems. How will they adapt to these
systems without
massive,
unrealistic, and possibly undesirable intervention by
government
officials, engineers, technologists, or
international
lending
agencies?
An extensive
training program undertaken by a voluntary agency,
Action for
Food Production (AFPRO), New Delhi, to train masons
to construct
fixed-dome Janata design plants has been only
partially
successful. AFPRO has found that even
though masons
know what to
do, they lack the self-confidence to construct
these plants
without supervision. AFPRO's experience
suggests
that training
and extension work for promoting biogas systems
(as well as
for technology in general) must deal with psychological
issues as
well as with technical knowhow. If
biogas
systems
cannot be designed, constructed, operated, and maintained
largely by
the people who will use them, their "appropriateness"
in providing
energy, fertilizers, and that messy
thing called
rural development seems dubious at best.
Nevertheless,
it is important to acknowledge that despite the
potentially
serious managerial and sociological problems that
may occur
during the operations of village biogas systems, this
does not mean
such problems necessarily will occur.
There are
numerous
examples of villagers adapting to radical departures
from their
traditional way of life once they were convinced of
the merits of
the new way. While vested interests
will attempt
to control
any change, the judicious intervention by a village
elder,
popular chief minister, or perhaps even the prime minister,
can
immobilize obstructionist forces.
Before such "marketing"
is done,
village-scale biogas systems must be economical
and reliable,
and their impact on different village groups
better
understood.
The point
behind this discussion of questions still to be
resolved is
not to condemn biogas systems. Rather,
it is to
show that
despite a great deal of promise, serious questions do
remain.
By specifying these uncertainties, a much
clearer sense
emerges of
what is needed in the future.
VIII.
Conclusions and Recommendations
In 1974,
Prasad, Prasad, and Reddy published "Biogas Plants:
Prospects,
Problems, and Tasks" in the Economic and Political
Weekly.
This highly influential article is a
masterful synthesis
of a great
amount of seemingly unrelated data. It
remains
the most
concise and comprehensive statement about biogas systems.
In the years
since, the ASTRA group, Bangalore, has conducted
extensive
research and development to improve system
designs and
increase gas yield through the use of solar energy.
ASTRA has
also begun to deepen our understanding of village
resource and
energy flows. PRAD, in Lucknow, has
undertaken
development
and extension of small brick, fixed-dome digester
designs with
reasonable success. Other groups like
MCRC,
Madras, have
experimented with low-cost hybrid digester designs
and
integrated energy-food-fertilizer systems.
Two village-scale
systems have
been built and are functioning with mixed
degrees of
success, and at least three promising systems are
under
construction. The Department of Science
and Technology of
the
Government of India has spent Rs 56 lakhs (roughly
$700,000) on
its three year, "All-India Coordinated Project on
Biogas."
This program sponsors research on the
microbiology of
digestion,
ferrocement gas-holder construction, dual fuel
engines,
etc., and has established several regional biogas system
testing
centers. Other groups are also
conducting experiments
with biogas,
as discussed earlier.
After
numerous on-site visits and discussions, it seems that
small,
nongovernmental, often undercapitalized groups have contributed
most to the
further development of biogas systems.
The
government
All-India Coordinated Project has not matched the
autonomous
small research groups in terms of the quality,
creativity,
and long-term usefulness of their research.
The
small teams
are often constrained by lack of resources and
insufficient
"clout" to secure access to materials and monitoring
equipment.
Furthermore, their often tenuous financial
situation
makes it
difficult for them to keep dedicated and competent
research,
development, and implementation teams intact.
Such groups
are especially difficult to maintain due to the
system of
rewards and incentives in Indian research.
These
incentives
are either heavily biased toward Western basic
research or
else respond to the needs of Indian industry and
government
agencies.
Despite the
achievements of some groups, it is clear that many
of the basic
questions posed in the 1974 biogas article in the
Economic and
Political Weekly still remain unanswered.
System
performance
must improve; costs must be reduced, a variety of
organic
matter still awaits practical field level digestion,
the relative
advantages of fixed-dome vs. floating-drum gas-holders
must be
established, and the unknowns surrounding the
operation and
management of village-scale systems remain.
Much
more work
needs to be done to piece together the data to answer
these
questions more definitively. In
fairness, it must be
noted that
system construction, start-up, and operation must be
evaluated for
at least one year before any conclusions may be
drawn concerning
performance of a particular system.
Even more
time-consuming,
and perhaps of greater necessity, is the difficult
process of
identifying a village that could use a biogas
system to
meet local needs. Promoters would then
need to establish
the trust and
credibility to work there, collecting all
relevant
data, and finally designing and constructing a large-scale
system.
Biogas systems research also must compete
with
the full
range of energy technology research, from solar
collectors to
breeder reactors.
Happily, the
pace of biogas systems work is accelerating.
The
Pura village
project will be quite helpful in assessing the
potential
contribution of biogas systems in meeting rural
needs.
The Pura system is based on detailed
resource surveys
and will be
coupled with an industry. The system is
an advanced
design, and
has village operation and self-management as a
primary
goal. PRAD is reportedly constructing
several large
50-80
[m.sup.3] fixed-dome village-scale systems that should help
answer some
of the questions about both the cost and performance
of the
fixed-dome design. There are plans for
constructing
6-20
village-scale systems as part of the Department of Science
and
Technology's further work in collaboration with KVIC, PRAD,
the Center
for Science for Villages, and the Indian Institute
of
Management, Ahmedabad.
While more
village experience is needed, it is unclear whether
the
government sponsored approach will include the most cost-effective
designs,
integration of a small industry, and a
genuine
attempt to design and implement the systems with the
equal
participation of villagers. Even if the
executing group
plans to
march into a number of villages and, in the space of
several
months, "drop" large-scale biogas systems in those villages
and then
monitor system operation, some technical data
will be
generated. However, these systems will
be operating in
the peculiar
context of an "outside" project that villagers
will treat
with the same range of bemused, annoyed, bewildered,
and
manipulative attitudes that have been observed in similar
projects.
Such a scheme would be grandiose in scale,
but
limited in
usefulness.
If the
experiences of the dedicated research and extension
groups such
as ASTRA, PRAD, Center for Science for Villages,
MCRC, Butwal
Technical Institute, Appropriate Technology Development
Association,
and others are any guide, the nurturing of
an equal
relationship with villagers based on mutual learning
and respect
is a difficult, slow process that demands a complex
mix of
scientific, management, and communications skills,
coupled with
a great deal of commitment on the part of the
technical
assistance team. Effective village
energy technology
work and,
probably, effective rural development are possible
only if done
at the micro-level.
Most of the
remaining technical questions concerning biogas
systems could
be resolved easily within two to three years
given
adequate funding and proper coordination of research
efforts.
Some ways to do this, in order of increasing
difficulty,
are suggested
below:
1.
Create a network among the small biogas
research groups so
that their
work becomes complementary and a greater exchange of
experiences
and knowledge occurs. The smaller
groups understandably,
and probably
correctly, wish to preserve their
autonomy.
They are wary of any incorporation into a
large
government-sponsored
research effort. However, these groups
also suffer
from an ignorance of each other's work due to poor
communications,
financial constraints precluding frequent contacts,
and
reluctance for a variety of reasons to take time
away from
their own work and share their findings with others.
This network
must evolve from the groups themselves so that the
autonomy of
each remains unthreatened. Any external
funding for
this type of
network, whether from private foundations, government
ministries,
or international lending agencies, must protect
the autonomy
of the participating groups. There may
be
some tension
between the needs of the funding source to have
accountability
for its sponsored projects and the desire of
some network
participants to merely exchange information and
not publish
until their work is completed. This is
not a question
of jealously
guarding trade secrets to protect potential
profits or
prestige. Many of these groups have had
many painful
experiences
with outside interests that distort or exploit
their years
of work. The smaller groups often have
special
relationships
with villages; outside interference can potentially
undo years of
establishing credibility and trust.
Despite
these
challenges, the advantages of small groups sharing
their work
among themselves are numerous, and a framework for
cooperation
can be developed if the groups themselves are
willing to do
so.
2.
Create a more harmonious relationship among
national planners,
national
laboratories, and the smaller research and
development
groups. The exact nature of this
relationship is
difficult to
specify, and a discussion of Indian institutional
politics and
bureaucratic jurisdictions is beyond the scope of
this
study. It would appear possible that
smaller research and
development
groups could suggest areas of basic research in
which they
lack resources or competence. These
areas could then
be taken up
by national laboratories and planning bodies.
There are
several such research areas worth mentioning:
a.
Analyses of the thermal efficiencies of
different fuels as a
function of the appliances in which the
fuels are burned.
The variations found in different
agroclimatic regions must
be identified so that reliable energy
consumption norms can
be established.
b.
Surveys of energy flows in rural areas to
establish a set of
norms for different agroclimatic
areas. It is essential to
reduce the number of possible permutations
due to customs,
diet, geography, local costs, appliance
efficiency, crop and
animal husbandry patterns, etc., if rural
energy planning is
to move beyond macro-level guesswork and
costly micro-level
analyses.
c.
Identification of small industries that can
make use of the
type of energy available from biogas
systems. These industries
must have a high probability of achieving
a profit to
enable a village system to be viable
financially. Their
various financial, technical,
organizational, and marketing
aspects need to be understood
thoroughly. Some industries
that seem to have promise are:
dairies; refrigeration; use
of Ca[CO.sub.2]-based products; grinding;
milling; threshing; chaffing;
food processing, rice husk cement
manufacturing; brick
and tile making; some melting operations;
fertilizer manufacturing;
animal feed and fodder; pyrolytic
processes; and
oil expelling and extraction.
3.
Effective village energy planning will be
possible only if
an
organizational infrastructure is created to deliver usable
energy
technologies to villages. Such an
infrastructure must be
able to
undertake:
a.
An assessment of needs, conducted jointly by villagers
and planners.
b.
The development of responses to those needs which may or
may not involve the installation of
such hardware as a
biogas system.
c.
The implementation and monitoring of work.
These three
phases of rural energy planning must be integrated,
which clearly
is a difficult management problem. This
integration
will require
some creative organizational development.
Many of the
existing groups concerned with rural energy issues
have
considerable individual strengths, but are isolated from
each
other. They frequently approach energy
planning in a fragmented
way due to
limited resources. The result is that
technologists
experiment in
laboratories with technologies that are
of
questionable use to villagers, while many social scientists
criticize the
technologists' R&D efforts, often without understanding
adequately
the potential of the technology.
Meanwhile,
voluntary
agencies often use unproven technologies whose many
impacts are
only dimly appreciated and for which sufficient
financing and
technical assistance resources do not exist.
Invariably,
these three groups--technologists, social scientists,
and village
voluntary agencies--engage in destructive
rounds of
recriminations. A way must be found to
bring them
together.
One way to
nurture the kind of integration required would be to
form state
level rural energy groups. The state
level seems an
appropriate
scale in terms of available resources, common language,
politics, and
existing institutions and programs.
These
groups would
consist of representatives from private research
teams,
universities, state government officials, industry,
lending
institutions, and voluntary agencies.
While some of
these
individual representatives might serve as advisers, there
would also be
a need for a full-time staff. The
energy group
would have
the following functions:
1.
Coordinate the state-wide rural research and
development
efforts of
existing institutions, eliminating duplication and
ensuring that
research designs incorporate the perspectives of
economists,
anthropologists/sociologists, and voluntary
agencies.
2.
Organize the extensive exchange of rural
energy information
within the
state, among other Indian states, and with other
countries,
especially throughout Asia. The
considerable difficulties
encountered
by the author in obtaining reliable information
for this
study, necessitating repeated personal visits
throughout
India, underscores the need for information
exchange.
3.
Fund and evaluate demonstration projects,
and, if necessary,
create new
research groups to do this.
4.
Organize a "rural energy
corps." The corps would consist of
people
trained in conducting energy/ecological surveys and
would help
villagers select technologies that seem appropriate
to local
needs. It would do this by helping
people to obtain
financing,
secure access to materials, organize construction or
training
programs, and ensure the proper operation and maintenance
of
hardware. The corps would live in
strategically chosen
villages for
several years to maximize the effect of demonstration
projects,
provide ongoing technical assistance, and
monitor
progress carefully. If corps members
work with existing
voluntary
groups that already have established themselves in
villages, so
much the better. Where no such organizations
exist, the
corps could form the nucleus of a larger rural
development
effort that would be a natural outgrowth of
"energy"
work.
Aided by
coordination from the rural energy group and the vast
field
experience of the rural energy corps, energy planning
would become
an important aspect of development planning.
Energy
planning cannot be separated from land use, ownership
patterns,
caste relations, the division of labor between men
and women,
access to credit, and the economic and political
relationships
between urban and rural areas. It is a
dangerous
delusion to
treat rural energy planning as a matter of developing
and
installing "appropriate" hardware.
A firm link between
the
multidisciplinary coordination of the energy group and the
local planning
and implementation work of the rural energy
corps, each
learning from the other, will help protect against
such myopic
planning.
If promising
energy technologies, like biogas systems, are to
contribute to
rural life, the almost infinite number of system
designs and
variations must be reduced and simplified to a few
basic
systems. As Dr. A.K.N. Reddy suggests,
this work must be
based on a
much deeper understanding of the village economy and
ecosystem.
It may be possible to classify villages
broadly by
the nature of
their resource flows, and to use biogas system
designs that
would correspond to established patterns of consumption.
At a minimum,
a methodology must be developed to
allow a
technical team to assess easily, quickly, and accurately
a village's
resource flows. Such a methodology is
vital for
determining
the best investments in energy and other technologies,
and also for
the broader development problem of the
optimal use
of local resources. The organization of
state-level
energy groups
and a rural energy corps would be an important
first step
toward addressing some of these questions.
None of this
work will be possible without the help and trust
of villagers
themselves. Efforts must be made to
reduce the
divisions of
caste, religion, and education that have so crippled
India.
One way to begin building a cooperative
village
environment
is to have a technical team work with a receptive
village
leadership to define simple projects that require collective
work.
These projects should be executed easily and
have
immediate and
demonstrable results, such as improved village
road
drainage, construction of pit toilets, or a collective
lift
irrigation system. This would
demonstrate the technical
team's
credibility and competence, and would provide the villagers
with a sense
of confidence and willingness to cooperate.(89)
Using this
experience as a foundation, more complex
projects,
such as a village biogas system, could be discussed
to see if
villagers felt this system made sense to them, given
their
perception of their needs. In this way,
villagers could
correctly
feel that they chose a biogas system because it would
make their
lives easier, and thus would feel a sense of responsibility
and ownership
toward the system. They also would have
confidence in
the technical team and themselves, as proved by
the
successful completion of the earlier project.
As discussed
earlier, a number of areas require more research
and
development work to improve the performance of biogas systems.
However, far
more effort is needed to link the laboratory
with
villagers. The shifting of emphasis
toward joint research
and
development in partnership with villagers, responding to
their sense
of their needs, would be a radical departure from
the current
thrust of much rural energy research, which prefers
the isolation
of the laboratory and the cleanliness of the conference
room.
However romantic this approach may sound, it
poses great
challenges to scientists, planners, and villagers
alike, even
assuming that the will exists to embark upon this
path.
At the moment, it is difficult to be hopeful
about the
likelihood of
such a commitment. There are numerous
barriers
that make
this approach difficult. Even so, the
barriers must
be
overcome. Women and children spend
one-third to one-half of
their waking
hours collecting fuel. Crops are lost
because
there is no
energy to run even installed pumpsets.
Mountainsides
are denuded
and croplands destroyed. Entire
generations
of children
cannot study in the evening because there is no
light.
While many of these conditions have existed
for perhaps
thousands of
years, one can only wonder how much longer villagers
will tolerate
them, especially given the rising expectations
caused by
increasingly modern communications systems and
political and
commercial marketing.
During the
preparation of this study, the author met literally
hundreds of
college students, government officials, university
faculty, and
industrialists who were at least convincingly
sincere in
their expressed desire to live and work with villages
on rural
energy problems. The often cited
obstacle preventing
these
educated and committed individuals from doing so
is the
absence of an organization that would provide adequate
technical and
financial support, both for their work and their
personal
lives. There is a vast, potentially
renewable energy
source--human
talent--that remains untapped in India.
All that
is needed is
the vision to organize it.
Notes
(1) China:
Recycling of Organic Wastes in Agriculture (1978),
FAO Soils
Bulletins 40-41; China: Azolla
Propagation and Small-Scale
Biogas
Technology (1979). Also see:
M.N. Islam, "A Report
on Biogas
Programme in China" (1979).
(2) C.R. Prasad, K.K. Prasad, and A.K.N.
Reddy, "Biogas Plants:
Prospects and
Problems and Tasks," in Economic and Political
Weekly
(1974). Bombay has had a large-scale
municipal sewage
gas plant in
operation for some time, as have several other
cities in
India. R.K. Pachauri, Energy and
Economic Development
in India
(1977) suggests that there is great promise for biogas
systems in
urban areas. There are reports from the
People's
Republic of
China of municipal plants used to generate electricity.
See Chen
Ru-Chen et al., "A Biogas Power Station in
Fashan:
Energy from Night Soil" (1978).
(3) Roger Revelle, "Energy Use in
Rural India," in Science
(June 1976),
p. 971.
(4) Ashok Desai, India's Energy
Economy: Facts and Their Interpretation
(1980), pp.
44-61.
(5) N.B. Prasad, et al., Report of the
Working Group on Energy
Policy
(1979), p. 27.
(6) Revelle, op. cit., p. 970.
(7) A.K.N. Reddy et al., A Community
Biogas Plant System for
Pura Village
(1979). Sheep and goat dung are not
included in
the
calculations due to the difficulty in collection.
The
8.0 kg/head
average fits well with one set of detailed
observations.
(8) Based on empirical observations, ibid.
(9) KVIC, "Gobar Gas:
Why and How" (1977), p. 14.
Reddy, ibid,
p. 18,
observes a higher calorific value biogas (5,340-6,230
kcal/[m.sup.3]
but the conservative KVIC figures are used to
account for
variations in methane content due to temperature
and cattle
diet variation in India. Also, the
calorific value
for crop
residues is slightly overstated. However,
in view of
the large
amount of biomass, such as water hyacinth, that has
been omitted
from the calculations, this calorific value will
suffice.
(10) S.S. Mahdi and R.V. Misra,
"Energy Substitution in Rural
Domestic
Sector--Use of Cattle Dung as a Source of Fuel"
(1979), pp.
3-11. No data are given for yield of
goat dung; 0.1
kg/goat/day
has been assumed and the calculation corrected
accordingly.
(11) Revelle, op. cit., p. 973.
(12) Reddy, op. cit., p. 21.
This figure, based on data collected
in Pura
Village, is a very crude measure of the percentage
of total
energy used in cooking. Little is known
about the
all-India
range of variations of this figure, especially in the
north where
water heating and space heating requirements will
vary
seasonally. The figure probably
overstates energy consumed
in
cooking. This is acceptable for our
purpose since we are
looking for
conservative estimates.
(13) Ibid, p. 11.
(14) Fertilizer Association of India,
Handbook of Fertilizer
Usage (1980),
p. 76. The calculations of the
fertilizer content
of organic
materials are therefore conservative estimates.
(15) Madhi and Misra, op. cit., p. 5.
(16) The Hindu, 27, July 1980, p. 6, and
discussions with the
Fertilizer
Association of India.
(17) N.B. Prasad et al., op. cit., pp.
14-16, 32.
(18) Ibid., pp. 16, 32.
(19) See Ashok Desai, op. cit.
National Sample Survey Data and
NCAER fuel
consumption surveys are notorious for relying on
interviews
rather than actual measurement of fuel consumption.
An all-India
survey of energy consumption currently being prepared
by NCAER
attempts to improve data collection by establishing
local norms
for energy consumed in cooking, heating
water, etc.,
and then interviewing people about their eating
habits, daily
routines, etc. From this data, energy consumption
is computed
based on the norms, rather than by asking
people to
"remember" or visualize how much firewood they collect
daily.
However, the latter information may be used
to
crosscheck
survey data.
(20) One assumption that seems
questionable is the rate of substitution
of
noncommercial fuels by commercial fuels.
This is
based on
rapid progress in coal production and delivery, village
electrification,
greater availability of kerosene, increased
hydrogeneration,
conservation measures, greater use of
nuclear
power, and increased petroleum production to name a
few.
Recent power sector performance would
suggest that such
coordination
and efficiency is not likely.
Similarly, with population
increasing to
an estimated 920 million by the year
2000, it is
hard to imagine noncommercial fuel consumption
dropping as
the Working Group suggests. Finally,
the effects of
increased
agricultural production and the associated increased
availability
of crop residues and cattle population (and
therefore
dung) are not discussed in any detail.
(21) Ibid, pp. 35-36.
(22) Ibid, pp. 70-71.
(23) Ibid, pp. 37-39.
(24) These consumption figures are based
on discussions with
Kirloskar Oil
Engines, Ltd. Experiments have shown
that actual
diesel
consumption is reduced 90 percent. The
80 percent norm
is used to
account for performance fluctuations in engines of
different
ages, condition, etc.
(25) Reddy estimates for Pura Village that
although a pumpset
cost Rs
5,000, the electricity board can spend upwards of Rs
11,000
connecting the pumpset to the Central Government system.
See Reddy,
op. cit., p. 24.
(26) N.B. Prasad, et al., op. cit., p. 78.
(27) See National Academy of Sciences
(USA), Methane Generation
from Human,
Animal, and Agricultural Wastes, (1977), pp. 66-69;
C.R. Das and
Sudhir D. Ghatnekar, "Replacement of Cow Dung by
Fermentation
of Aquatic and Terrestrial Plants for use as Fuel
Fertilizer
and Biogas Plant Feed" (1970); private communication
with R.M.
Dave, Jyoti Solar Energy Institute, Vallabh Vidyanagar;
B.R. Guha et
al., "Production of Fuel Gas and Compost
Manure from
Water Hyacinth and its Techno-Economical Aspects
(sic) (1977);
P. Rajasekaran et al., "Effects of Farm Waste on
Microbiological
Aspects of Biogas Generation" (1980); T.K.
Ghose et al.,
"Increased Methane Production in Biogas" (1979);
P.V.R.
Subrahmanyam, "Digestion of Night Soil
and Aspects of
Public
Health" (1977); N. Sriramulu and B.N. Bhargava, "Biogas
from Water
Hyacinth" (1980); FAO, China:
Azolla Propagation
and
Small-Scale Biogas Technology (1978); N. Islam, "A Report
on Biogas
Programme of China" (sic) (1979), and Barnett et al.,
Biogas
Technology in the Third World (1978).
(28) Personal correspondence with R.M.
Dave, op. cit.
(29) K.V. Gopalakrishnan and B.S. Murthy,
"The Potentiality of
Water
Hyacinth for Decentralized Power Generation in Developing
Countries,"
(sic) in Regional Journal of Energy, Heat, and Mass
Transfer,
vol. 1, no. 4. (1979), pp. 349-357.
(30) C.R. Das and S. Gatnekar, op. cit.
(31) Islam and FAO, op. cit.
(32) National Academy of Sciences, op.
cit.
(33) Islam, op. cit.
(34) Sources of information on the
microbiological and engineering
aspects of
digestion include sources previously cited
(c.f. 30) as
well as FAO, China: Recycling of
Organic Wastes in
Agriculture
(1978); John L. Fry; Practical Building of Methane
Power Plants
for Rural Energy Independence (1974); John Finlay,
"Efficient,
Reliable Cattle Dung Gas Plants:
Up-to-date Development
in
Nepal" (1978); and the United Nations University,
Bioconversion
of Organic Residues for Rural Communities (1979).
The information contained in the text has
been obtained from
the above
sources and is a representative compilation of
observed
results from both laboratory and field tests.
It
cannot be
overemphasized that the figures cited will vary
depending on
local conditions. Any project team
referring to
this study or
the references cited would be wise to analyze
thoroughly
site conditions rather than to use these figures as
the database
for a particular project.
(35) See T.R. Preston, "The Role of
Ruminants in the Bioconversion
of Tropical
By-Products and Wastes into Food and Fuel," in
United
Nations University, op. cit., pp. 47-53.
The author is
grateful to
Dr. C.V. Seshadri, Director, Murugappa Chettiar
Research
Centre (MCRC) (Madras) for several helpful discussions
on this
topic.
(36) Some of the centers of
microbiological research in India
are ASTRA,
Indian Institute of Science (Bangalore); Center for
Science for
Villages (Wardha); Indian Institute of Sciences
(New Delhi);
Maharashtra Association for the Cultivation of
Science
(Pune); Shri A.M.M. Murugappa Chetiar Research Centre
(Madras); The
National Environmental Engineering Research
Institute
(Nagpur); Tamil Nadu Agricultural University
(Coimbatore);
and Jyoti Solar Energy Institute, Vallabh
Vidyanagar.
(37) See Khadi and Village Industries Commission,
Gobar Gas:
Why and How,
1979.
(38) D.K. Subramanian, P. Rajabapaiah and
Amulya K.N. Reddy,
"Studies
in Biogas Technology, Part II:
Optimisation of Plant
Dimensions,"
in Proceedings of the Indian Academy of Sciences,
vol. c2, Part
3 (September 1979), op. 365-379.
(39) Ibid, p. 368.
(40) Ibid, p. 373.
(41) P. Rajapapaiah et al., "Studies
in Biogas Technology, Part
I:
Performance of a Conventional Biogas
Plant," in ibid, pp.
357-63.
(42) C.R. Prasad and S.R. Sathyanarayan,
"Studies in Biogas
Technology,
Part III: Thermal Analysis," in
ibid, pp. 377-86.
(43) Amulya K.N. Reddy et al.,
"Studies in Biogas Technology,
Part IV:
A Novel Biogas Plant Incorporating a Solar
Water
Heater and
Solar Still," in ibid, pp. 387-93.
(44) S. Bahadur and K.K. Singh, Janata
Biogas Plants (1980).
(45) See E.I. DeSilva, "Biogas
Generation: Development Problems
and Tasks--An
Overview," in United Nations University, op.
cit., p.
89. For additional biogas experiences,
see S.K.
Subramanian,
Biogas Systems in Asia (1977) and Subramanian's
later
abridgement of the same in Barnett et al., Biogas
Technology in
the Third World: A Multidisciplinary
Review
(1978), pp.
97-126.
(46) Personal discussions with MCRC staff,
Madras.
(47) Personal discussions with John Finlay
and David Fulford,
Development
and Consulting Service, Butwal, Nepal.
(48) Personal discussions with Dr. S.V.
Patwardhan, Director,
Center for
Rural Development, Indian Institute of Technology
(Delhi).
MCRC (Madras) is also researching and
developing
integrated
biomass systems for villages.
(49) Although the National Academy of
Sciences, op. cit., pp.
61-83,
contains some helpful illustrations of system planning,
Reddy et al.,
A Community Biogas Plant System for Pura Village
(1979) is a
more comprehensive treatment of the type of
analysis
needed to design an appropriate biogas system.
A more
generalized,
relatively simple methodology needs to be developed
to enable
technical teams and villagers to design energy
systems
jointly.
(50) John Finlay, "Operation and
Maintenance of Gobar Plants"
(1978), p. 3.
(51) National Academy of Sciences, op.
cit., p. 85
(52) Ibid, pp. 92-93.
For an excellent, extremely detailed
troubleshooting
methodology, see Finlay, op. cit., pp. 10-16.
(53) G.L. Patankar, Recent Developments in
Gobar Gas Technology
(1977),
United Nations Economic and Social Commission for Asia
and the
Pacific (ESCAP), Report of the Workshop on Biogas Technology
and Utilization
(1975), p. 16.
(54) Suggested by Amulya K.N. Reddy.
(55) FAO, China:
Azolla Propagation and Small-Scale Biogas
Technology
(1978), p. 59, and Intermediate Technology
Development
Group, A Chinese Biogas Manual (1979), p. 64.
(56) Discussions with villagers using the
community system in
Fateh
Singh-Ka-Purva.
(57) Reddy et al., A Community Biogas
Plant System for Pura
Village
(1979), pp. 36-37.
(58) Ibid, p. 80.
This figure (.07 [m.sup.3]/person/day) seems
low,
but the methodology
deriving it is correct. This suggests
that
a
re-examination of the database nay be necessary.
(59) KVIC, ibid, p. 13.
See also:
Ramesh Bhatia, "Economic
Appraisal of
Biogas Units in India: A Framework for
Social
Benefit Cost
Analysis," in Economic and Political Weekly
(1977), pp.
1515-516, for a related discussion concerning the
need for
research in this area.
(60) Finlay, op. cit., pp. 4-5.
(61) Intermediate Technology Development
Group, op. cit., and
FAO, op.
cit., pp. 50-55.
(62) See photograph, FAO, op. cit., p. 59.
(63) The author is grateful to John Finlay
for this interesting
aspect of
prayer rituals in Nepal.
(64) P.B. Ghate, "Biogas:
A Pilot Project to Investigate a
Decentralized
Energy System" (1978), pp. 21-22.
(65) Kirloskar Oil Engines Limited,
"Kirloskar Gobar Gas Dual
Fuel
Engine" (1980), p. 6.
(66) K. Kasturirangan et al., "Use of
Gobar Gas in a Diesel
Fuel
Engine" (1977).
(67) ESCAP, op. cit., p. 21.
(68) Ibid and personal discussions with
Kirloskar Engineers.
See
also: Ramesh Bhatia, "Energy
Alternatives for Irrigation
Pumping:
Some Results for Small Farms in North
Bihar" (1979).
(69) John L. Fry, Practical Building of
Methane Power Plants
for Rural
Energy Independence (1974), p. 39.
(70) Bhatia, op. cit., p. 1507.
(71) Cited by John Finlay, op. cit., from
an earlier study by
Yarwalker and
Agrawal, "Manure and Fertilizers" (Nagpur:
Agricultural-Horticultural
Publishing House) (n.d.).
(72) Finlay, ibid.
(73) National Academy of Sciences, op.
cit., p. 51.
(74) S.K. Subramanian, "Biogas
Systems in Asia: A Survey" in
Bennett et
al., op. cit., p. 99.
(75) See the brief references to 17
percent increased wheat
yield in Wu
Chin County and subsequent discussion concerning
Jiongsu
Province, in FAO Soils Bulletin #40, op. cit., p. 47.
(76) See Andrew Barnett, "Biogas
Technology: A Social and
Economic
Assessment," in Barnett et al., Biogas Technology in
the Third
World (1978), pp. 69-96; Ramesh Bhatia, "Economic
Appraisal of
Biogas Units in India: A Framework for
Social
Cost-Benefit
Analysis" (1977).
"Energy Alternatives for Irrigation
Pumping: Some Results
for Small
Farm in North Bihar" (1978); Bhatia and Miriam
Naimar,
"Renewable Energy Sources, The Community Biogas Plant"
(1979); P.B.
Ghate, "Biogas: A Pilot Project to
Investigate a
Decentralized
Energy System" (1978); KVIC, "Gobar Gas:
Why and
How"
(1980); Indian Council of Agricultural Research, "The
Economics of
Cow Dung Gas Plants" (1976); Arjun Makhiajani and
Alan Poole,
Energy and Agriculture in the Third World (1975);
T.K. Moulik,
and U.K. Strivatsava, Biogas Plants at the Village
Level:
Problems and Prospect in Gujarat (1976) and
Biogas
Systems in
India: A Socio-Economic Evaluation
(1978); J.K.
Parikh and
K.S. Parikh, "Mobilization and impacts of Biogas
Technologies"
(1977); C.R. Prasad, K.K. Prasad, and A.K.N.
Reddy,
"Biogas Plants: Prospects,
Problems and Tasks" (1977);
K.K.
Prasad and A.K.N. Reddy, "Technological
Alternatives and
the Indian
Energy Crisis" (1977); and A.K.N. Reddy et al., A
Community
Biogas Plant System for Pura Village (1979).
(77) See Shishir Mukherjee and Anita Arya,
"Comparative
Analysis of
Social Cost-Benefit Studies of Biogas Plants"
(1978).
(78) See Andrew Barnett, "The Social
and Economic Assessment of
Biogas
Technology" (1979), David French, "The Economics of
Energy
Technologies" (1979), and L. Squire and Herman van der
Tak, Economic
Analysis of Projects (1975).
(79) Islam, op. cit., p. 18.
(80) Subramaniam, S.K., Biogas Systems in
Asia (1977).
(81) Islam, op. cit., pp. 46-52.
(82) For an excellent discussion of the
performance of KVIC
biogas
systems, a socio-economic profile of users, and a solid
analysis of
the organizational weaknesses of the Indian biogas
programme,
see T.K. Moulik, U.K. Srivastava and P.M. Shingi,
Biogas System
in India: A Socio-Economic Evaluation
(1978). The
author is
indebted to Dr. Srivastava for several helpful
discussions
on these issues.
(83) Ramesh Bhatia and Miriam Naimar, op.
cit. This is a
thoughtful
analysis of the Fateh Singh-ka-Purva Project.
See
also:
P.B. Ghate, "Biogas:
A Pilot Project to Investigate a
Decentralized
Energy System" (1978), and Shahzad Bahadur and
S.C. Agarwal,
"Community Biogas Plant at Fateh Singh-Ka-Purva:
An Evaluation
Report" (Lucknow: PRAD, 1980).
(84) Bhatia and Naimar, ibid, point out
that villages may
actually
prefer kerosene for lighting since they control the
timing of its
use. It would be interesting to conduct
an
analysis of
energy consumption over time, comparing kerosene
lamps and
direct biogas lamps. Despite
potentially higher
energy
efficiencies with biogas lighting methods, it is possible
that a good
deal of gas would be wasted due to the timed
release.
Once the gas is in the pipeline it is
subject to
pressure
losses, conversion losses (running generators with no
storage
battery), and losses due to venting into the atmosphere
if people
forget to close a valve or have inefficient lamps.
(85) These reasons, coupled with an
unfamiliarity with the concept
of paying for
a "municipal service," cast doubt on the
Parikhs'
notion of charging different progressive prices for
the
biogas. See Jyoti K. Parikh and Kirit
S. Parikh, "Mobilization
and Impact of
Biogas Technologies," in Energy (1977).
The
other problem
with this otherwise sensible idea is that it is
not clear
that poor people would be willing to cook in community
kitchens even
if they would receive gas free or at
nominal
cost. It has proven historically
difficult to
"purchase"
such cooperative, collective living.
(86) Ibid, and T.K. Moulik and U.K.
Srivastava, Biogas Plants
at the
Village Level: Problems and Prospects
in Gujarat (1975),
pp. 110-11.
(87) Bhatia and Naimar, op. cit., pp. 26-28.
(88) This section is based on discussions
with a great number
of rural
social workers, sociologists, private voluntary organizations,
and even a
few difficult conversations with some
villagers.
I am especially grateful to Dr. Shivakumar
of the
Madras
Institute of Development Studies, Dr. Amulya K.N. Reddy,
Indian
Institute of Science (Bangalore), Dr. K. Oomen, Department
of Sociology,
Jawaharlal Nehru University (New Delhi),
Dr. C.V.
Seshadri and Rathindranath Roy, MCRC (Madras), and
Dr. Y.
Nayudamma, Central Leather Research Institute (Madras).
See also a
very thoughtful article by Hermalata Dandekar,
"Gobar
Gas Plants: How Appropriate are
They?" in Economic and
Political
Weekly (1980), pp. 887-92.
(89) Ibid. This excellent idea
is the way many rural development
teams
establish their credibility and create a sense of
the possible
through collective effort. The
Sarvodaya Movement
in Sri Lanka
is an example of this approach, although it goes
one, perhaps
necessary, step further by presenting this narrow
concept of
technological change within a highly developed sense
of Buddhist
values. Villagers respond to this
because it is a
natural
extension of their traditional cultural ethos.
Appendix
NPV and Payback Analysis for
Baseline Data
Models 1-3
(Full cost digester, no revenue from
either
the sale or surplus gas or rice husk
cement)
Note:
For a detailed explanation of symbols used,
please refer
to pp. 59-61 in the text.
VITA is
grateful to the Department of Computer Sciences, Indian
Institute of
Technology, Madras, India, for providing this
printout.
MODEL 1:
COOKING & LIGHTING
D = 294306.00
R =
0.00 P_DS = 0.00
R_LC = 0.04
D =
2943 6.000 G =
0.047
L = 9212.500
N_LC =
5.000 P_LC =
10.000
D_L =
273.750 G_C =
11425.000
LO_L = 43.800
P =
10000.000 R =
0.000
D_LC = 13400.000
G_L = 2300.000
LO_P =
4.800 P_D =
2.700
R_LC = 0.040
D_P =
30.120 G_P =
253.000
LO_RC =
0.000
P_DS =
0.000
D_RC =
0.000 G_RC =
0.000
M = 0.000
P_FW =
0.040
E =
33250.000 I
=
4709.000 N =
0.000
P_K = 2.250
YEAR
1
2
3 4
5
6
7-1C 11-15
ANNUAL
RECURRING COSTS
LOAN AMORTIZATION
0.00
12724.62 12724.62
12724.62
13724.62 12724.62
0.00
0.00
ENERGY (DIESEL)
820.45
820.45 820.45
820.45
820.45
820.45 3281.75
4102.24
LUBE OIL
486.00
486.00 486.00
486.00
486.00
486.00 1944.00
2430.00
(LABOR)
8212.50
8212.50 8212.50
8212.50
8212.50
8212.50
32850.00 41062.50
OPERATIONS AND MAINTENANCE
250.00
250.00 250.00
250.00
250.00
250.00 1000.00
1250.00
TOTAL RECURRING COSTS
1556.45
14281.06 14281.06
14281.06
14281.06 14281.06
6225.75
7782.24
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.50
4360.50 4360.50
4360.50
4360.50
4360.50 17442.00
21802.50
FIREWOOD
240.00
240.00 240.00
240.00
240.00
240.00 960.00
1200.00
INCREASED AGRI PRODUCTIVITY
4709.00
4709.00 4709.00
4709.00
4709.00
4709.00 18836.00
23545.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00
0.00
0.00 0.00
ELECY
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
REVENUE FROM CCMM OPNS
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
TOTAL ANNUAL BENEFITS
9222.09
9222.09 9222.09
9222.09
9222.09
9222.09 36388.34
46110.43
BENEFITS-COSTS
TO VILLAGE =
(((ENERGY
SAVED (WOOD + KEROSENE)
+ SALE OF
SURPLUS GAS) < .981)
+ COMMERCIAL
REVENUE + INCREASED
AGRICULTURAL
YIELD - LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ OPERATIONS
& MAINTENANCE) 7665.64
-5058.97
-5058.97 -5058.97
-5058.97
-5058.97
30662.55 38329.18
NET PRESENT
WORTH (15 YEARS): 14454.44
ANNUAL CASH
FLOW
((SALE OF
SURPLUS GAS + 791.00)
< .991 +
COMMERCIAL REVENUE) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ LABOR + DP.
& MAINTENANCE) -8992.97
-21717.59
-21717.59 -21717.59 -21717.59
-21717.59
-35971.89 -44564.86
NO PAYBACK
MODEL 1:
COOKING & LIGHTING
D = 294306.00
R =
0.00 P_DS = 0.00
R_LC =0.10
D =
294306.000 G =
0.047
L = 8212.500
N_LC =
5.000 P_LD =
10.000
D_L =
273.750 G_C =
11425.000
LO_L = 43.800
P =
10000.000 R =
0.040
D_LC = 13400.000
G_L = 2300.000
LO_P =
4.800 P_D =
2.700
R_LC = 0.100
D_P =
30.120 G_P =
253.000
LO_RC =
0.000
P_DS =
0.000
D_RC =
0.000 G_RC =
0.000
M = 0.000
P_FW =
0.040
E =
33250.000 I
=
4709.000 N =
0.000
P_K = 2.250
YEAR
1
2 3
4
5 6
7-10
11-15
ANNUAL
RECURRING COSTS
LOAN AMORTIZATION
0.00
14943.29 14943.29
14943.29
14943.29 14943.29
0.00
0.00
ENERGY (DIESEL)
820.45 820.45
820.45
820.45 820.45
820.45
3281.79 4102.24
LUBE OIL
486.00
486.00 486.00
486.00
486.00
486.00 1944.00
2430.00
(LABOR)
8212.50
8212.50 8212.50
8212.50
8212.50 8212.50
32850.00
41062.50
OPERATIONS AND MAINTENANCE
250.00
250.00 250.00
250.00
250.00
250.00 1000.00
1250.00
TOTAL RECURRING COSTS
1556.45
16499.73 16499.73
16499.73
16499.73 16499.73
6225.79
7782.24
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.50
4360.50 4360.50
4360.50
4360.50
4360.50 17442.00
21802.50
FIREWOOD
240.00 240.00
240.00
240.00 240.00
240.00
960.00 1200.00
INCREASED AGRI PRODUCTIVITY
4709.00
4709.00 4709.00
4709.00
4709.00
4709.00 18836.00
23545.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
ELECY
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
REVENUE FROM CCMM OPNS
0.00
0.00
0.00
0.00 0.00
0.00
0.00 0.00
TOTAL ANNUAL BENEFITS
9222.09
9222.09 9222.09
9222.09
9222.09
9222.09 36388.34
46110.43
BENEFITS-COSTS
TO VILLAGE =
(((ENERGY
SAVED (WOOD + KEROSENE)
+ SALE OF
SURPLUS GAS) < .981)
+ COMMERCIAL
REVENUE + INCREASED
AGRICULTURAL
YIELD - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ OPERATIONS
& MAINTENANCE) 7665.64
-7277.64
-7277.64 -7277.64
-7277.64
-7277.64
30662.55 38323.13
NET PRESENT
WORTH (15 YEARS): 6808.51
ANNUAL CAST
FLOW =
((SALE OF
SURPLUS GAS + 791.00)
< .991 +
COMMERCIAL REVENUE) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ LABOR + DP.
& MAINTENANCE) -8992.97
-2353.25
-23936.25 -23936.25 -23536.25
-23936.25
-35971.89 -44564.86
NO PAYBACK
MODEL 1:
COOKING & LIGHTING
D = 506255.00
R =
0.00 P_DS = 0.00
R_LC =0.04
D =
506255.000 G =
0.047
L = 8212.500
N_LC =
5.000 P_LC =
10.000
D_L =
273.750 G_C =
11425.000
LO_L = 43.800
P =
10000.000 R =
0.000
D_LC = 22100.000
G_L = 2300.000
LO_P =
4.800 P_D =
2.700
R_LC = 0.040
D_P =
30.120 G_P =
253.000 LO_RC =
0.000
P_DS =
0.000
D_RC =
0.000 G_RC =
0.000
M = 0.000
P_FW =
0.040
E =
33250.000 I
=
8100.000 N =
0.000
P_K =
2.250
YEAR
1
2
3 4
5
6
7-10 11-15
ANNUAL
RECURRING COSTS
LOAN AMORTIZATION
0.00
14678.80 14678.80
14678.80
14678.80 14678.80
0.00
0.00
ENERGY (DIESEL)
820.45
820.45 820.45
820.45
820.45
820.45 3281.75
4102.24
LUBE OIL
486.00
486.00 486.00
486.00
486.00
486.00 1944.00
2430.00
(LABOR)
8212.50
8212.50 8212.50
8212.50
8212.50
8212.50 32850.00
41062.50
OPERATIONS AND MAINTENANCE
250.00
250.00 250.00
250.00
250.00
250.00 1000.00
1250.00
TOTAL RECURRING COSTS
1556.45
16235.24 16235.24
16235.24
16235.24 16235.24
6225.79
7782.24
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.50
4360.50 4360.50
4360.50
4360.50
4360.50
17442.00
21802.50
FIREWOOD
240.00
240.00 240.00
240.00
240.00
240.00 960.00
1200.00
INCREASED AGRI PRODUCTIVITY
8100.00
8100.00 8100.00
8100.00
8100.00
8100.00 32400.00
40500.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
ELECY
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
REVENUE FROM CCMM OPNS
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
TOTAL ANNUAL BENEFITS
12613.09
12613.09 12613.09
12613.09
12613.09 12613.09
50452.34
63065.43
BENEFITS-COSTS
TO VILLAGE =
(((ENERGY
SAVED (WOOD + KEROSENE)
+ SALE OF
SURPLUS GAS) < .981)
+ COMMERCIAL
REVENUE + INCREASED
AGRICULTURAL
YIELD - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ OPERATIONS
& MAINTENANCE) 11056.64
-3622.15
-3622.15 -3622.15
-3622.15
-3622.15
44226.55 55283.18
NET PRESENT
WORTH (15 YEARS): 33512.33
ANNUAL CASH
FLOW =
((SALE OF
SURPLUS GAS + 791.00)
< .991 +
COMMERCIAL REVENUE) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ LABOR + DP.
& MAINTENANCE) -8992.97
-23671.77
-23671.77 -23671.77
-23671.77 -23671.77
-35971.89
-44564.86
NO PAYBACK
MODEL 1:
COOKING & LIGHTING
D =
506255.00
R = 0.00
P_05 = 0.00
R_LC = 0.10
D =
506255.000 G =
0.047
L = 8212.500
N_LC =
5.000 P_LO = 10.000
D_L =
273.750 G_C = 11425.000
LO_L =
43.800 P =
10000.000
R = 0.000
D_LC = 22100.000
G_L = 2300.000
LO_P =
4.800 P_D =
2.700
R_LC = 0.100
D_P =
30.120 G_P =
253.000
LO_RC =
0.000 P_DS =
0.000
C_RC =
0.000 G_RC =
0.000
M = 0.000
P_FW =
0.040
E =
33250.000 IA =
8100.000
N = 0.000
P_K =
2.250
YEAR
1
2
3 4
5
6
7-10 11-15
ANNUAL
RECURRING COSTS
LOAN AMORTIZATION
0.00
17238.20 17238.20
17238.20
17238.20
17238.20 0.00
0.00
ENERGY (DIESEL)
320.45
320.45 820.45
820.45
820.45
820.45 3281.75
4102.24
LUBE OIL
486.00
486.00
486.00 486.00
486.00
486.00
1944.00 2430.00
(LABOR)
8212.50
8212.50 8212.50
8212.50
8212.50
8212.50 32950.00
41062.50
OPERATIONS AND MAINTENANCE
250.00
250.00 250.00
250.00
250.00
250.00 1000.00
1250.00
TOTAL RECURRING COSTS
1536.45
18794.64
18794.64
18794.64 18794.64
18794.64
6225.79 7782.24
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.50
4360.50 4360.50
4360.50
4360.50
4360.50 17442.00
21802.50
FIREWOOD
240.00
240.00 240.00
240.00
240.00
240.00 960.00
1200.00
INCREASED AGRI PRODUCTIVITY
8100.00
8100.00 8100.00
8100.00
8100.00
8100.00 32400.00
40500.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
ELEC Y
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
REVENUE FROM COMM OPNS
0.00
0.00
0.00
0.00
0.00
0.00 0.00
0.00
TOTAL ANNUAL BENEFITS
12613.09
12613.09
12613.09
12613.09 12613.09
12613.09
50452.34 63065.43
BENEFITS-COSTS
TO VILLAGE =
(((ENERGY
SAVED (WOOD + KEROSENE)
+ SALE OF
SURPLUS GAS) + .981)
+ COMMERCIAL
REVENUE + INCREASED
AGRICULTURAL
YIELD - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ OPERATIONS
& MAINTENANCE)
11056.64 -6181.55
-6181.55
-6181.55
-6181.55 -6181.55
44226.55
55283.13
NET PRESENT
WORTH (15 YEARS): 24692.20
ANNUAL CASH
FLOW =
((SALE OF
SURPLUS GAS + 791.001
% .981 +
COMMERCIAL REVENUE) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ LABOR + DP.
& MAINTENANCE) -8992.97
-26231.16
-26231.16 -26231.16
-26231.16 -26231.16
-35971.39
-44964.86
NO PAYBACK
MODEL 2: COOKING, LIGHTING &
INDUSTRY
D =
326579.00 R =
0.00 P_DS = 0.00
R_LC = 0.04
D
= 326579.
0 G =
0.047
L = 11812.500
N_LC =
5.000 P_LO = 10.000
D_L =
273.750 G_C = 11425.000
LO_L =
43.800 P =
10000.000
R = 0.000
D_LC = 15000.000
G_L = 2300.000
LO_P =
4.800 P_D =
2.700
R_LC = 0.040
D_P =
30.120 G_P =
253.000
LO_RC =
0.000 P_DS =
0.000
C_RC =
150.000 G_RC = 1260.000
M =
4800.000 P_FW =
0.040
E =
41000.000 IA =
5225.000
N = 0.000
P_K =
2.250
YEAR
1
2
3 4
5
6
7-10 11-15
ANNUAL
RECURRING COSTS
LOAN AMORTIZATION
0.00
14824.80 14824.80
14824.80
14824.80
14324.80 0.00
0.00
ENERGY (DIESEL)
1225.45
1225.45 1225.45
1225.45
1225.45
1225.45 4901.79
6127.24
LUBE OIL
726.00
726.00
726.00 726.00
726.00
726.00
2904.00 3630.00
(LABOR)
11812.50
11812.50 11812.50
11812.50
11812.50
11812.50 47250.00
55062.50
OPERATIONS AND MAINTENANCE
5050.00
5050.00 5050.00
5050.00
5050.00
5050.00 20200.00
25250.00
TOTAL RECURRING COSTS
7001.44
21826.24 21826.24
21826.24
21826.24
21826.24 28005.77
35007.21
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.10
4360.50 4360.50
4360.50
4360.50
4360.50 17442.00
21802.50
FIREWOOD
240.00
240.00 240.00
240.00
240.00
140.00 960.00
1200.00
INCREASED AGRI PRODUCTIVITY
5225.00
5225.00 5225.00
5225.00
5225.00
5225.00 20900.00
20125.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00
0.00 0.04
0.00
ELEC Y
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
REVENUE FROM COMM OPNS
0.00
0.00
0.00
0.00
0.00 0.00
0.00
0.00
TOTAL ANNUAL BENEFITS
9738.09
9738.09
9738.09
9738.09 9738.09
9738.09
38952.34 48690.43
BENEFITS-COSTS
TO VILLAGE =
(((ENERGY
SAVED (WOOD + KEROSENE)
+ SALE OF
SURPLUS GAS) + .981)
+ COMMERCIAL
REVENUE + INCREASED
+
AGRICULTURAL YIELD) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ OPERATIONS
& MAINTENANCE) 2736.60
-12088.15
12088.15 -12088.15
-12088.15
-12088.15 -10946.58
13683.22
NET PRESENT
WORTH (15 YEARS): 20273.67
ANNUAL CASH
FLOW =
((SALE OF
SURPLUS GAS + 791.001
% .981 +
COMMERCIAL REVENUE) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ LABOR + DP.
& MAINTENANCE) -19037.57
-32862.77
-32862.77 -32862.77
-32862.77
-32862.77 -72151.88
-90189.8
NO PAYBACK
MODEL 2: COOKING, LIGHTING &
INDUSTRY
D =
326579.00 R =
0.00
P_DS = 0.00
R_LC = 0.10
D =
326579.000 G =
0.047
L = 11812.500
N_LC =
3.001 P_LC = 10.000
D_L =
273.750 G_C = 11425.000
LC_L =
43.800 P =
10000.000
R = 0.000
D_LC = 15000.000
G_L = 2300.000
LC_P =
4.800 P_D =
2.700
R_LC = 0.100
D_P =
30.120 G_P =
253.000
LC_RC =
0.000
P_DS =
0.000
C_RC =
150.000 G_RC = 1260.000
M =
4800.000 P_FW =
0.040
E =
41000.000 IA =
5225.000
N = 0.000
P_K =
1.250
YEAR
1
2
3 4
5
6
7-10
11-15
ANNUAL
RECURRING COSTS
LOAN AND AMORTIZATION
0.00
17409.66 17409.66
17409.66
17409.66
17409.66 0.00
0.00
ENERGY (DIESEL)
1225.45
1225.45 1225.45
1225.45
1225.45
1225.45 4901.79
6127.24
LUBE OIL
726.00
726.00 726.00
726.00
726.00
726.00 2904.00
3630.00
(LABOR)
11812.50
11812.50
11812.50 11812.50
11812.50
11812.50 47250.00
59062.50
OPERATIONS AND MAINTENANCE
5050.00
5050.00 5050.00
5050.00
5050.00
5050.00 20200.00
25250.00
TOTAL RECURRING COSTS
7001.44
24411.10
24411.10 24411.10
24411.10
24411.10
28005.77 35007.21
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.50
4360.50 4360.50
4360.50
4360.50
4360.50 17442.00
21802.50
FIREWOOD
240.00 240.00
240.00
240.00
240.00 240.00
960.00
1200.00
INCREASED AGRI PRODUCTIVITY
5225.00
5225.00 5225.00
5225.00
5225.00
5225.00 20900.00
26125.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
ELEC Y
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
REVENUE
FROM COMM OPNS
0.00 0.00
0.00
0.00
0.00 0.00
0.00
0.00
TOTAL ANNUAL BENEFITS
9738.09
9738.09 9738.09
9738.09
9738.09
9738.09
38952.34
48690.43
BENEFITS-COSTS TO VILLAGE =
(((ENERGY SAVED (WOOD + KEROSENE)
+ SALE OF SURPLUS GAS) + .9811
+ COMMERCIAL REVENUE + INCREASED
AGRICULTURAL YIELDS - (LOAN
AMORTIZATION + DIESEL + LUBE OIL
+ OPERATIONS & MAINTENANCE)
2736.64
-14673.01 -14673.01
-14673.01
-14673.01
-14673.01 10946.58
13683.22
NET PRESENT WORTH (15 YEARS):
-39181.57
ANNUAL CASH FLOW =
((SALE OF SURPLUS GAS + 791.001
% .981 + COMMERCIAL REVENUE - (LOAN
AMORTIZATION + DIESEL + LUBE OIL
+ LABOR + OP. & MAINTENANCE)
-18037.97
-35447.63 -35447.63
-35447.63
-35447.63
-35447.63 -72151.88
-90189.81
NO PAYBACK
MODEL 2: COOKING, LIGHTING &
INDUSTRY
D
= 506255.00
R = 0.00
P_DS = 0.00
R_LC = 0.04
D =
506255.000 G =
0.041
11812.500 N
LC = 5.000
P_LC = 10.000
D L =
273.750 G_C = 11425.000
LO_L =
43.800 P =
10000.000
R = 0.000
D_LC =
22107.100 G_L =
2300.000
LO_F = 4.800
P_D =
2.700 R_LC =
0.040
D_P
= 30.120
G_P =
253.000 LO_RC =
0.000
P_DS =
0.000
C_RC =
150.000 G_RC = 1260.000
M =
4800.000 P_FW =
0.040
E =
41000.000 IA =
8100.000
N = 0.000
P_K
= 2.250
YEAR
1
2
3 4
5
6
7-10 11-15
ANNUAL
RECURRING COSTS
LOAN AMORTIZATION
0.00
16419.59 16419.59
16419.59
16419.59 16419.59
0.00
0.00
ENERGY (DIESEL)
1225.45
1225.45 1225.45
1225.45
1225.45
1225.45 4901.79
6127.24
LUBE OIL
726.00
726.00 726.00
726.00
726.00
726.00
2904.00
3630.00
(LABOR)
11812.50
11812.50 11812.50
11812.50
11812.50
11812.50 47250.00
59062.50
OPERATIONS AND MAINTENANCE
5050.00
5050.00 5050.00
5050.00
5050.00
5050.00 20200.00
25250.00
TOTAL RECURRING COSTS
7001.44
23421.03
23421.03
23421.03 23421.03
23421.03
28005.77 35007.21
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.50
4360.50
4360.50
4360.50 4360.50
4360.50
17442.00
21802.50
FIREWOOD
240.00
240.00
240.00
240.00 240.00
240.00
960.00 1200.00
INCREASED AGRI PRODUCTIVITY
8100.00
8100.00
8100.00 8100.00
8100.00
8100.00
32400.00 40500.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
ELEC Y
0.00
0.00 0.00
0.00
0.00
0.00 0.00
0.00
REVENUE FROM COMM OPNS
0.00
0.00
0.00
0.00 0.00
0.00
0.00 0.00
TOTAL ANNUAL BENEFITS
12613.09
12613.09
12613.09
12613.09 12613.09
12613.09
50452.34 63065.43
BENEFITS-COSTS
IN VILLAGE =
((( ENERGY
SAVED (WOOD + KEROSENE)
+ SALE OF SURPLUS
GAS) + .981)
+ COMMERCIAL
REVENUE + INCREASED
+
AGRICULTURAL YIELD - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ OPERATIONS
& MAINTENANCE)
5611.64 -10807.94
-10807.94
-10807.94
-10807.94 -10807.94
22446.58
28058.22
NET PRESENT
WORTH (15 YEARS): -13902.12
ANNUAL CASH
FLOW =
((SALE OF
SURPLUS GAS + 191.001
% .981 +
COMMERCIAL REVENUE - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ LABOR + DP.
& MAINTENANCE)
-13037.57 -34457.55
-34457.55
-34457.55
-34457.55 -34457.55
-72151.66
-90185.61
NO PAYBACK
MODEL 2: COOKING, LIGHTING &
INDUSTRY
O =
506255.00
R = 0.00
P_OS = 0.00
R_LC = 0.10
O =
506255.000 G =
0.047
L = 11812.500
N_LC =
5.000 P_LC =
10.000
O_L =
273.750 G_C = 11425.000
LO_L =
43.800 P
=10000.000
R = 0.000
O_LC = 22100.000
G_L = 2300.000
LC_P =
4.800 P_D =
2.700
R_LC = 0.100
O_P =
30.120 G_P =
253.000
LC_RC = 0.000
P_DS =
0.000
0.000
P_FW =
0.040
O_RC =
150.000 G_RC = 1260.000
M =
4800.000
E =
41000.000 1A=
8100.000
N = 0.000
P_K =
2.250
YEAR
1
2
3 4
5
6 7-10
11-15
ANNUAL
RECURRING COSTS
LOAN AMORTIZATION
0.00
19282.51
19282.51 19282.51
19282.51
19282.51 0.00
0.00
ENERGY (DIESEL)
1225.45
1225.45 1225.45
1225.45
1225.45 1225.45
4901.79
6127.24
LUBE OIL
726.00
726.00 726.00
726.00
726.00 726.00
2904.00
3630.00
(LABOR)
11812.50
11812.50 11812.50
11812.50
11812.50 11812.50
47250.00
59062.50
OPERATIONS AND MAINTENANCE
5050.00
5050.00 5050.00
5050.00
5050.00 5050.00
20200.00
25250.50
TOTAL RECURRING COSTS
7001.44
26283.95 26283.95
26283.95
26283.95 26283.95
28005.77
35007.21
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.50
4360.50 4360.50
4360.50
4360.50 4360.50
17442.00
21802.50
FIREWOOD
240.00
240.00 240.00
240.00
240.00 240.00
960.00
1200.00
INCREASED AGRI PRODUCTIVITY
8100.00
8100.00 8100.00
8100.00
8100.00 8100.00
32400.00
40500.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
ELEC Y
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
REVENUE FROM COMM OPNS
0.00 0.00
0.00
0.00 0.00
0.00
0.00 0.00
TOTAL ANNUAL BENEFITS
12613.09
12613.09 12613.09
12613.09
12613.09 12613.09
50452.34
63065.43
BENEFITS-COSTS
TO VILLAGE =
(((ENERGY
SAVED (WOOD + KEROSENE)
+ SALE OF
SURPLUS GAS) + .9811
+ COMMERCIAL
REVENUE + (INCREASED
AGRICULTURAL
YIELDS) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ OPERATIONS
& MAINTENANCE) 5611.64
-13670.87 -13670.87 -13670.87 -13670.87
-13670.87 22446.58
28058.22
NET PRESENT
WORTH (15 YEARS): -23768.18
ANNUAL CASH
FLOW =
((SALE OF
SURPLUS GAS + 791.001
+.981 +
COMMERCIAL REVENUE) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ LABOR + OP.
& MAINTENANCE) -18037.97
-37320.48 -37320.48 -37320.48 -37320.48
-37320.48 -72151.88
-90189.81
NO PAYBACK
MODEL 3: LIGHTING & INDUSTRY
O
= 86021.00
R = 0.00
P_DS = 0.00
R_LC = 0.04
O =
86121.000 G =
0.041
L = 11812.500
N_LC = 5.000
P_LC = 10.000
O_L =
273.750 G_C =
0.000
LO_L = 43.800
P =
0.000 R =
0.000
O_LC =
4500.000 G_L =
2300.000
LO_F = 4.800
P_D =
2.700 R_LC =
0.040
O_P =
30.120 G_P =
253.000
LO_RC =
0.000
P_DS = 0.000
O_RC =
150.000 G_RC = 1260.000
M =
4807.000 P_FW = 0.020
E =
41000.000 IA =
1376.000
N = 0.000
P_K =
2.250
YEAR
1
2
3 4
5
6 7-10
11-15
ANNUAL
RECURRING COSTS
LOAN AMORTIZATION
0.00
10220.13 10220.13
10220.13 10220.13
10220.13 0.00
0.00
ENERGY (DIESEL)
1225.45
1225.45 1225.45
1225.45
1225.45 1225.45
4901.79
6127.24
LUBE OIL
726.00
726.00 726.00
726.00
726.00 726.00
2904.00
3630.00
(LABOR)
11812.50
11812.50 11812.50
11812.50 11812.50
11812.50 47250.00
55062.50
OPERATIONS AND MAINTENANCE
5050.00
5050.00 5050.00
5050.00
5050.00 5050.00
20200.00
25250.00
TOTAL RECURRING COSTS
7001.44
17221.57
17221.57 17221.57 17221.57
17221.57
28005.77 35007.21
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.50
4360.50
4360.50 4360.50
4360.50
4360.50 17442.00
21802.50
FIREWOOD
120.00
120.00
120.00 120.00
120.00
120.00 480.00
600.00
INCREASED AGRI PRODUCTIVITY
1376.00
1376.00 1376.00
1376.00
1376.00 1376.00
5504.00
6880.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
ELEC Y
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
REVENUE FROM COMM OPNS
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
TOTAL ANNUAL BENEFITS
5771.36
5771.36
5771.36 5771.36
5771.36
5771.36 23085.45
28856.82
BENEFITS-COSTS
IN VILLAGE =
(((ENERGY
SAVED (WOOD + KEROSENE)
+ SALE OF
SURPLUS GAS) + .9811
+ COMMERCIAL
REVENUE + INCREASED
AGRICULTURAL
YIELDS) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ OPERATIONS
& MAINTENANCE)
-1230.08 -11450.20 -11450.20
-11450.20 -11450.20 -11450.20
-4920.31 -6150.89
NET PRESENT
WORTH (15 YEARS): -44576.51
ANNUAL CASH
FLOW =
((SALE OF
SURPLUS GAS + 791.001
+ .981 +
COMMERCIAL REVENUE) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ LABOR + OP.
& MAINTENANCE) -18087.97
-28258.09 -28258.09 -28258.09 -28258.09
-28258.09 -72151.88
-90189.81
NO PAYBACK
MODEL 3: LIGHTING & INDUSTRY
O =
86071.00 R.
0.00 P_DS = 0.00
R_LC = 0.10
O =
86021.00 G =
0.047
I = 11812.500
N_LC =
5.000 P_LD = 10.000
O_L =
273.750 G_C =
0.000
LO_L = 43.800
P =
0.000 R =
0.000
O_LC =
4500.000 G_L =
2300.000
LO_P = 4.800
P_D =
2.100 R_LC =
0.100
O_P =
30.120 G_P =
253.000
LO_RC = P_DS =
0.000
0.000
P_FW =
0.020
O_RC =
150.000 G_RC = 1260.000
M =
4800.000 P_K =
2.250
E =
41000.000 IA =
1376.000
N = 0.000
YEAR
1
2
3 4
5
6
7-10 11-15
ANNUAL
RECURRING COSTS
LOAN AMORTIZATION
0.00
12002.11 12002.11
12002.11
12001.11 12002.11
0.00
0.00
ENERGY (DIESEL)
1225.45
1225.45 1225.45
1225.45
1225.45 1225.45
4901.75
6127.24
LUBE OIL
726.00
726.00 726.00
726.00
726.00 726.00
2904.00
3630.00
(LABOR)
11812.50
11812.50 11812.50
11812.50
11812.50 11812.00
47250.00
59062.50
OPERATIONS AND MAINTENANCE
5050.00
5050.00 5050.00
5050.00
5050.00 5050.00
20200.00
25250.00
TOTAL RECURRING COSTS
7001.44
19003.55
19003.55 19003.55
19003.55
19003.55 28005.77
35007.21
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.50
4360.50
4360.50 4360.50
4360.50
4360.50 17442.00
21802.50
FIREWOOD
120.00
120.00
120.00 120.00
120.00
120.00 480.00
600.00
INCREASED AGRI PRODUCTIVITY
1376.00
1376.00 1376.00
1376.00
1376.00 1376.00
5504.00
6880.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
ELEC Y
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
REVENUE FROM COMM OPNS
0.00
0.00
0.00 0.00
0.00
0.00 0.00
0.00
TOTAL ANNUAL BENEFITS
5771.36
5771.36
5771.36 5771.36
5771.36
5771.36 23085.45
28856.82
BENEFITS-COSTS
IN VILLAGE =
(((ENERGY
SAVED (WOOD + KEROSENE)
+ SALE OF
SURPLUS GAS) + .9811
+ COMMERCIAL
REVENUE + INCREASED
AGRICULTURAL
YIELDS) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ OPERATIONS
& MAINTENANCE)
-1230.08 -13232.19
-13232.19
-13232.19 -11232.19
13232.19
-4920.31 -6150.35
NET PRESENT
WORTH (15 YEARS): -50717.55
ANNUAL CASH
FLOW =
((SALE OF
SURPLUS GAS) + 791.001
+ .981 +
COMMERCIAL REVENUE) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ LABOR + OP.
& MAINTENANCE)
-18037.51 -30040.08
-30040.08
-30040.08 -30040.08
-30040.08
-72151.88 -90189.81
NO PAYBACK
MODEL 3: LIGHTING & INDUSTRY
D= 506255.00
R =
0.00 P_DS = 0.00
R_LC = 0.04
O =
506255.000 G =
0.041
L = 11812.500
N_LC = 5.000
P_LC = 10.000
O_L =
273.750 G_C =
0.000
LO_L = 43.800
P =
0.000 R =
0.000
D_LC = 22100.000
G_I = 2300.000 LO_F
= 4.800
P_D = 2.700
R_LC=
0.040
O_P =
30.120 G_P =
253.000
LO_RC =
0.000
P_DS = 0.000
O_RC =
150.000 G_RC= 1260.000
M =
4800.000 P_FW = 0.020
E =
41000.000 IA =
8100.000
N = 0.000
P_K =
2.250
YEAR
1
2
3 4
5
6
7-10 11-15
ANNUAL
RECURRING COSTS
LOAN AMORTIZATION
0.00
14173.41 14173.41
14173.41
14173.41
14173.41
0.00 0.00
ENERGY (DIESEL)
1225.45
1225.45 1225.45
1225.45
1225.45 1225.45
4901.79
6127.24
LUBE OIL
726.00
726.00 726.00
726.00
726.00 726.00
2904.00
3630.00
(LABOR)
11812.50
11812.50 11812.50
11812.50
11812.50 11812.50
47250.00
59062.00
OPERATIONS AND MAINTENANCE
5050.00
5050.00 5050.00
5050.00
5050.00 5050.00
20200.00
25250.00
TOTAL RECURRING COSTS
7001.44
21174.85
21174.85 21174.85
21174.85
21174.85 28005.77
35007.21
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4160.50
4360.50 4360.50
4360.50
4360.50 4360.50
17442.00
21802.50
FIREWOOD
120.00
120.00 120.00
120.00
120.00 120.00
480.00
600.00
INCREASED AGRI PRODUCTIVITY
8100.00
8100.00 8100.00
8100.00
8100.00 8100.00
32400.00
40500.00
SURPLUS ENERGY INTO DIESEL
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
ELEC Y
0.00
0.00
0.00
0.00 0.00
0.00
0.00 0.00
REVENUE FROM COMM OPNS
0.00
0.00
0.00 0.00
0.00
0.00
0.00 0.00
TOTAL ANNUAL BENEFITS
12495.36
12495.36
12495.36 12496.36
12496.36
12496.36 49981.45
62476.82
BENEFITS-COSTS
TO VILLAGE =
(((ENERGY
SAVED
(WOOD + KEROSENE)
+ SALE OF
SURPLUS GAS) + .9811
+ COMMERCIAL
REVENUE + INCREASED
AGRICULTURAL
YIELD) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ OPERATIONS
& MAINTENANCE)
5493.92 -8679.98
-8679.48
-8679.48 -8679.48
-8679.48
21975.69 27469.61
NET PRESENT
WORTH (15 YEARS): -7056.68
ANNUAL CASH
FLOW =
((SALE OF
SURPLUS GAS) + 791.001
+.981 +
COMMERCIAL REVENUE) - (LOAN
AMORTIZATION
+ DIESEL + LUBE OIL
+ LABOR + OP.
& MAINTENANCE) -18037.57
-32211.38 -32211.38
-32211.38 -32211.38
-32211.38
-72151.88 -90189.81
NO PAYBACK
MODEL 3
: LIGHTING & INDUSTRY
D = 506255.00
R =
0.00 P_0S = 0.00 R_LC = 0.10
D=
506255. 00 G=
0.041
L= 11812.500
N_LC=
5.000 P_LO=
10.000
O_L=
273.750 G_C=
0.000
LO_L= 43.800
P= 0.000
R=
0.000
O_LC=
22100.000 G_L=
2300.000
LC_F= 4.800
P_D=
2.700 R_LC=
0.100
O_P=
30.170 G_P=
253.000
LC_RC=
0.000
P_DS=
0.000
O_BC=
150.000 G_RC=
1260.000
M= 4300.000
P_PW=
0.020
E=
41000.000 L =
8100.000
A= 0.000
P_X=
2.250
YEAR
1
2
3 4
5 6
7-10
11-15
ANNUAL
RECURRING COSTS
LOAN
AMORTIZATION
0.00 16644.68
16644.68
16644.68 16644.68
16644.68
0.00 0.00
ENERGY
(DIESEL) 1225.45
1225.45
1225.45 1225.45
1225.45
1225.45 4901.79
6127.24
LUBE OIL
726.00
726.00
726.00 726.00
726.00
726.00 2904.00
3630.00
11812.50
11812.50
11812.50 11812.50
11812.50
11812.50 47250.00
59062.50
OPERATIONS
AND MAINTENANCE 5050.00
5050.00
5050.00 5050.00
5050.00
5050.00 20200.00
25250.00
TOTAL
RECURRING COSTS 7001.44
23646.13
23646.13 23646.13
23646.13
23646.13 28005.77
35007.21
ANNUAL
BENEFITS
ENERGY SAVED - KEROSENE
4360.50
4360.50 4360.50
4360.50
4360.50 4360.50
17442.00
21802.50
FIREWOOD
120.00
120.00 120.00
120.00
120.00 110.00
480.00
600.00
INCREASED
AGRI PRODUCTIVITY 8100.00
8100.00
8100.00 8100.00
8100.00
8100.00 32400.00
60500.00
SURPLUS
ENERGY INTO DIESEL 0.00
0.00
0.00 0.00
0.00
0.00 0.00
0.00
ELECY
0.00
0.00 0.00
0.00
0.00 0.00
0.00
0.00
REVENUE FROM
COMM OPNS 0.00
0.00
0.00 0.00
0.00
0.00 0.00
0.00
TOTAL ANNUAL
BENEFITS 12495.66
12495.36
12495.36 12495.36
12495.34
12495.36 49981.45
62476.32
BENEFITS-COSTS
IN VILLAGE =
(((ENERGY
SAVED LOAN KEROSENED)
* SALE OF
SURPLUS GAS) (.981)
* COMMERCIAL
REVENUE - INCREASED
AGRICULTURAL
YIELDS - (LOAN
AMORTIZATION
& DIESEL + LURF OIL
* OPERATIONS
& MAINTENANCE) 5493.92
-11150.76 -11150.76 -11150.76 -11150.16 -11150.76
21915.65 27469.61
NET PRESENT
WORTH (15 YEARS): -1557 .17
ANNUAL CASH
FLOW =
((SALE OF
SURPLUS GAS (751.00)
1.981 *
COMMERCIAL REVENUE - (LOAN
AMORTIZATION
* DIESEL * LURF OIL
* LABOR * OP.
& MAINTENANCE) -18037.57 -34682.65
-34682.65 -34682.65 -34682.65 -34682.65 -78151.89 -90189.81
Bibliography
"Action
Research in Community Biogas," in Voluntary Action.
New
Delhi:
Association of Voluntary Agencies for Rural
Development,
September
1980.
Bahadur,
Shahzad and Singh, K.K. Janata Biogas Plants.
Lucknow,
Uttar
Pradesh: Planning Research and Action
Division, State
Planning
Institute, U.P., 1980.
Barnett,
Andrew; Pyle, Leo; and Subramanian, S.K. Biogas
Technology in
the Third World: A Multi-disciplinary
Review.
Ottawa:
International Development Research Centre,
1978.
Bhatia,
Ramesh. "Economic Appraisal of
Biogas Units in India:
Framework for
Social Benefit-Cost Analysis."
Economic and
Political
Weekly 12 (1977): nos. 13-14.
A Community
Biogas Plant System for Pura Village.
Bangalore:
Karnataka
State Council for Science and Technology, 1979.
Dandekar,
Hematalata. "Gobar Gas
Plants: How Appropriate are
They."
Economic and Political Weekly 15 (May 17,
1980).
Das, C.R. and
Ghathekar, S.D. "Replacement of
Cowdung by Fermentation
of Aquatic
and Terrestrial Plants for use as a Fuel,
Fertilizer,
and Biogas Plant Feed," in Documentation Notes.
Bombay:
Tata Energy Research Institute, January
1980.
Desai,
Ashok. "India's Energy Consumption:
Composition and
Trends,"
Energy Policy. September 1978.
"Efficient,
Reliable Cattle Dung Gas Plants:
Up-to-date Development
in
Nepal." Bangkok:
Expert Group Meeting on Biogas
Development,
U.N. Economical Social Committee for Asia and the
Pacific, June
1978.
FAO.
China:
Recycling of organic wastes in Agriculture.
FAO
Soils
Bulletin, no. 40. Rome:
FAO, 1978.
FAO.
China:
Azolla Propagation and Small-Scale Biogas Technology.
FAO Soils
Bulletin, no. 41. Rome:
FAO, 1979.
Finlay, John
H. Operation and Maintenance of Gobar
Gas Plants.
Butwal,
Nepal:
Development and Consulting Services, United
Mission to
Nepal, 1978.
Fry, L.
John. Practical Building of Methane
Power Plants for
Rural Energy
Independence. Andover, Hampshire, U.K.:
Chapel
River Press,
1974.
Ghate, P.B.
"Biogas: A Pilot Project to
Investigate a Decentralized
Energy
System." Lucknow, Uttar
Pradesh: PRAD, State
Planning
Institute, U.P., 1978.
Indian
Council of Agricultural Research. The
Economics of Cow
Dung Gas
Plants. New Delhi:
Indian Council of Agricultural
Research,
1976.
India's
Energy Economy: Facts and Their
Interpretation. Bombay:
Center for
Monitoring Indian Economy, 1980.
Intermediate
Technology Development Group (ITDG). A
Chinese
Biogas Manual.
London:
ITDG, 1979.
Islam,
M.N. A Report on Biogas Programme of
China (sic). Dacca:
Department of
Chemical Engineering, Bangladesh University of
Engineering
and Technology, 1979.
Kasturirangan,
K., et al. "Use of Gobar Gas as
Direct Fuel."
Available
from the Department of Mechanical Engineering, Indian
Institute of
Technology, Madras.
Makhijani,
Arjun. "Energy Policy for Rural
India," Economic-Political
Weekly,
special issue (August 1977): 145-164.
Makhijani,
Arjun and Poole, Alan. Energy and
Agriculture in the
Third
World. Cambridge, MA:
Ballinger Publishing Co., 1975.
McGarry,
Michael and Stainforth, Jill. Compost,
Fertilizer, and
Biogas
Production from Human and Farm Wastes in the People's
Republic of
China. Ottawa:
International Development Research
Centre, 1978.
Methane
Generation from human, Animal, and Agricultural
Wastes.
Washington, D.C.:
1977.
Moulik, T.K.
and Srivastava, U.K. Biogas Plants at
the Village
Level:
Problems and Prospects in Gujarat.
Ahmedabad:
Center for
Management in
Agriculture, Institute of Management, 1975.
Moulik, T.K.
and Srivastava, U.K.; and Singh, P.M.
Biogas
Systems in
India: A Socio-Economic
Evaluation. Ahmedabad:
Indian
Institute of Management, 1978.
Mukharjee,
S.K. and Arya, Anita. Comparative
Analysis of Social
Cost Benefit Studies of Biogas Plants.
Ahmedabad:
Indian
Institute of Management, 1979.
National
Academy of Sciences (NAS). Making
Aquatic Weeds Useful:
Some Perspectives for Developing
Countries. Washington,
D.C.:
NAS, 1976.
National
Council of Applied Economic Research.
Survey of Rural
Energy
Consumption in Northern India. 1977.
Parikh, Jyoti
K., and Parikh, Kirit S.
"Mobilization and
Impacts of
Biogas Technologies." Energy, vol.
2. London:
Pergamon
Press, 1977: 441-55.
Patankar,
G.L. Recent Developments in Gobar Gas
Technology.
Bombay:
Gobar Gas Development Centre, Khadi and
Village Industries
Commission,
1977.
Prasad, C.R.;
Prasad, K.K.; and Reddy, Amulya K.N. "Biogas
Plants:
Prospects, Problems and Tasks" in
Economic and
Political
Weekly 11 (August 1974): 1347-64.
Prasad, N.B.
et al. Report of the Working Group on
Energy
Policy.
New Delhi:
Planning Commission, Government of India,
1979.
Reddy, Amulya
K.N. et al. "Studies in Biogas
Technology: Parts
I-IV,"
"Performance of a Conventional Biogas Plant," "Optimisation
of Plant
Dimensions," "Thermal Analysis," and "A Novel
Biogas Plant
Incorporating a Solar Water Heater and Solar
Still"
in Proceedings of the Indian Academy of Sciences, vol.
C2, part
3. Bangalore:
Indian Institute of Sciences, September
1979:
357-96.
Reddy, Amulya
K.N. and Prasad, K. Krishna.
"Technological
Alternatives
and the Indian Energy Crisis" in Economic and
Political
Weekly, special issue (August 1977):
1465-502.
Revelle,
Roger. "Energy Use in Rural India," Science (June
4,1976):
969-475.
Ru-Chen, Chen
et al. "A Biogas Power Station in
Foshan: Energy
From Night
Soil." Guangzhou, China:
Guangzhou Institute of
Energy
Commission, 1978.
Sathianathan,
M.A. Biogas:
Achievements and Challenges.
New
Delhi:
Association of Voluntary Agencies for Rural
Development,
1975.
Subramanian,
S.K. Biogas Systems in Asia.
New Delhi:
Management
Development
Institute, 1977.
United
Nations Economic and Social Commission for Asia and
Pacific
(ESCAP). Report of the Workshop on
Biogas Technology
and
Utilization. Bangkok:
ESCAP, 1975.
United
Nations University (UNU). Bioconversion
of Organic
Residues for
Rural Communities. UNU:
Tokyo, 1979, especially:
DaSilva,
E.J. "Biogas Generation:
Developments, Problems,
and
Tusles--An Overview."
Matsuzaki,
T. "Continuous Composting System
for Disposal and
Utilization
of Animal Wastes at the Village Level."
Preston,
T.R. "The Role of Ruminants in the
Bioconversion of
Tropical
By-products and Wastes into Food and Fuel.
Seshadri,
C.V. "Analysis of Bioconversion
Systems at the
Village
Level."
========================================
========================================
