The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

M-09
ISBN 92-5-103126-6

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© FAO 1992

Contents

Acknowledgment

Chapter one: Preface and objectives of the review

Sustainable development

Chapter two: Introduction and overview

Chapter three: Short historical background on anaerobic digestion

Historical developments of anaerobic digestion technology
Present interest in anaerobic digestion

Chapter four: Microbiology biochemistry and physiology

Microbiology and biochemistry
Microbial metabolism in anaerobic digestion
Methanogenic bacteria
Homo-acetogenic bacterial metabolism
Hydrolytic and fermentative bacteria
Interspecies hydrogen transfer
The methanogens - distribution and taxonomy
Methanogens in hypersaline environments
Influence of high salt levels on methanogenic digestion
Growth substrates of methanogenic bacteria
Nutritional and physiological requirements
The effects of environaental fact ors on anaerobic digestion
Influence of carbon/nitrogen ratio on digestion
Biodegradability of digester feedstock

Chapter five: Environmental pollution and pathogen control

Environmental pollution
The need for decontamination
The role of blogas in improving rural development, environment and ecology.

Chapter six: Aerobic versus anaerobic wastewater treatment

Aerobic treatment
Anaerobic treatment
Anaerobic treatment systems for municipal wastewater
Anaerobic filter studies
Anaerobic extended and fluidized beds
UASB studies
Conclusions

Chapter seven: Anaerobic processes, plant design and control

Digester types
Sizing of digesters
Comparison of alternative design approaches
Problems and solutions of feedstocks and effluents in full-scale biogas plants (based on hobson, 1987)

Digester feedstocks
Mechanical problems
Chemical and biochemical treatments of feedstocks
Digester effluent

Control device in an anaerobic digestion process
Process control

Chapter eight: Output and its use I

Biogas as an alternative energy source

Domestic uses
Agricultural and industrial uses
Use of biogas for vehicle fuel

The purification of biogas

Physical and chemical properties of hydrogen sulohide
The origins of hydroqen sulphide in biogas plants
The effect of H₂S on the biogas plant and the gas-utilization equipment
Engines
The odour of biogas
Determination of the H₂S content of biogas
Methods for removing H₂S from biogas
Regeneration

Biogas production and utilization in China
Use of biogas in India
Experience of full scale plant of biogas generation at Hambran, Punjab
Effect of temperature variation on gas production

Chapter nine: Output and its use II

Digested slurry: the profit lies in the use of the effluent
Biomass uses without anaerobic digestion

The effect of use on the nitrogen present in the biomass is discussed below.

Biomass uses following anaerobic digestion
Land application of effluent
Algae production
The use of anaerobic fermentation treatment in livestock breeding
Nutritional value of effluent in livestock diets
Fish feeding with digested cow manure
Effluent as a substrate for growing plants and crops

Uses for horticulture
Growth and rooting experiments

Uses of effluent for mushroom production
Composting processes
Process alternatives for composting
Is the composting profitable?
Composition and digestibility of different sized fractions in cattle slurry

Chapter ten: Integrated approach to the anaerobic digestion process

Possible integrated systems
Methodology to assess integrated systems
Existing integrated systems

Chapter eleven: The economics of anaerobic digestion

Introduction
Analysis of economic feasibility for biogas construction
Economic analysis of simple biogas pit for household use in rural area
Economic analyses of cement biogas pits for household use in chinese rural area.
Economic analysis of community biogas plants in China.
Community level plants in India
Experience of economic evaluation in other countries
Economic analysis on electricity generation with biogas in Chinese rural areas
Industrial and commercial feedlots
Feasibility estimate for a turn-key community plant
Economic evaluation study for a full-scale village-community plant

The products of the plant
Feasibility estimate for a turn-key farm waste utilization system

Economic analysis

Summary and conclusions of a full-scale village-community plant
Conclusion from the chinese experience
Problems in evaluating the community indian plants
Organic feedstocks
Labour time involved in collection of organic materials and water, digester operation and maintenance
Maintenance
Economic evaluations

Chapter twelve: Technical and social constraints in integrating biogas plants into farms

Constraints delaying the diffusion of installations
Requirements for an optimally integrated biogas installation
New incentives to build biogas plants

Chapter thirteen: Biogas programs in developing countries

Experience with biogas in China
Potential of biogas generation and biogas digester construction
Biogas utilization
Effluent utilization
Economic aspects
Financial support
Training in biogas technology
Organization of the biogas sector
Potential for biogas generation and digester construction
Experience with biogas in India
Biogas plants
Biogas production
Use of biogas
Utilization of effluent
Cost of installation
Annual costs and savings
Financial assistance from government
Organization of the biogas sector
Organization of energy sector
Utilization of effluent
Costs and benefits
Research and development
Experiences with biogas
Installations
Effluent utilization
Costs and benefits
Experiences with biogas
Organization of the biogas sector
Africa

Appendix 1: References

Appendix 2: Glossary

Appendix 3: Institutes and research workers