Domestic biogas digesters in developing countries: Performance and selection of appropriate design for mass dissemination

Over 44 million biogas digesters of several designs are disseminated in Developing Countries (DCs) to improve access to modern energy services to 2.6 billion people who depend on traditional biomass. In terms of numbers this technology seems to be of high performance and any designs could be mass disseminated everywhere in DCs. This paper has two objectives: (i) to present an overview of domestic digesters performance in DCs, (ii) to describe a Decision Making Model (DMM) that is developed to identify the most appropriate digester design for mass dissemination in a particular region. Performances are characterized in terms of functional state, effectiveness in producing biogas, process efficiency and pathogen reduction: 50% of the digesters in DCs are reported in good functional state and 80% provide 3-4 hours of biogas per day. In terms of process efficiency, 58-94% volatile solids degradation is reported, 96% coliform and 99% Escherichia coli are eliminated. The DMM is based on the Analytic Hierarchy Process, the Energy Indicators for Sustainable Development and other performance indicators. It is applied to rural areas of Cameroon to select the digester design among five types. The Nepali GGC2047 design seems to result as the most appropriate for mass dissemination in this country