Measures of appropriateness: the resource requirements of anaerobic digestion (biogas) systems

Anaerobic digesters have a potential for providing fuel, fertilizer, and a sanitary means of waste disposal in rural areas of less developed countries. Despite these potential benefits, digesters have had a disappointingly low success rate in many LDCs. Poor economics may explain these failures in some cases but poor fits between digesters and local conditions - a lack of appropriateness - can also be a useful indicator.Using a detailed accounting framework, we disaggregate anaerobic digestion systems into five subsystems, analogous to the subsystem components of the nuclear power fuel cycle. Relying on published information from India and China, we compare 38 fixed-and floating-dome digester models and note qualitative and quantitative differences in their uses of construction and operating resources. Environmental and social resources used in the subsystems are also discussed. A tentative ‘specifications plate’ for anaerobic digestion systems is proposed. This provides quantitative measures of the appropriateness of particular systems in different settings.