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		The Purification of Biogas (GTZ, 1985, 33 p.)
			(introduction...)
			0. Introduction
			1. Properties of hydrogen sulphide
			2. The origins of hydrogen sulphide in biogas plants
			3. The effect of hydrogen sulphide on the biogas plant and the gas-utilization equipment
			4. Determination of the hydrogen sulphide content of biogas
			5. Methods for removing hydrogen sulphide from biogas
			6. Purifying absorbent
			7. Requirements on the absorbent
			8. The desulphurizing apparatus
			9. Operation procedures for gas desulphurization
			10. Summary
			Appendix

0. Introduction

This review attempts to set out the procedures for removing hydrogen sulphide from biogas.
Hydrogen sulphide is particularly harmful when biogas is used in internal combustion engines. Its chemical reactions and those of its combustion product - sulphur dioxide, quickly lead to severe corrosion and wear on engines.

The only practical way of removing the hydrogen sulphide on a small scale is by dry desulphurization using ferrous substances. Locally available, iron-containing soil is suitable for use as the purifying agent in Third World countries. This manual contains a detailed description of criteria for designing the purification chamber. It also presents the basic steps for manufacturing the purifying agent or absorbent.

The paper is mainly directed at staff in the various regional biogas advisory services. In particular the colleagues must give assistance in selecting the soils, and sometimes carry out investigations to identify the composition of the substances. Only an optimally applied purification agent can ensure a long life for the gas user, particularly engines, and avoid unnecessary repairs and maintenance on the plant equipment.