ABSTRACT
Mention small-scale anaerobic digesters (SSADs) and eyebrows will be raised. Some identify this with the ‘low’ technology approach adopted by millions in south-east Asia for heating food with biogas generated from inverted barrels or underground vessels with gas holding capacity. Conversely, small-scale digesters are thought of as a mixed bag of different technologies in the more financially driven economies where the large scale tends to dominate. However, the possibilities of what could be achieved by SSADs are substantial. From a sustainability perspective, what if every farm or community could have electricity and heating, or indeed cooling and transport fuel, without the dependency on global markets with a rapid payback of 3–5 years? With SSADs all of the electricity and heat could be used within a system that reduces greenhouse gas (GHG) emissions (only about 22 per cent of energy generated at a power station is received by the consumer — 7 per cent transmission losses for 30 per cent electricity generation from coal). The impact of anaerobic digestion (AD) on anthropomorphic GHG emissions would contribute about 4–7 per cent of heat and power for the UK to help meet national and European obligations by 2020 (Lukehurst, 2009).
