From: Quazi, A.R. [NGO Forum for DWSS] Study on the re-use of excreta in Bangladesh. In: Environmental Sanitation Case Studies to be published by IRC International Water and Sanitation Centre.
Biogas is a mixture of methane (60%) and carbon dioxide (40%), produced by anaerobic digestion of organic material, usually animal dung, human excreta and crop residue. Small-scale biogas digesters provide fuel for domestic lighting, cooling and cooking. Large-scale biogas plants are able to produce sufficient gas to fuel engines to generate electricity. The (thermal) energy available from biogas is about 6 kWh/m3m³. This corresponds to half a litre of diesel oil and 5.5 kg of firewood. 1 kg of human faeces generates about 50 litres of biogas: 1 kg of cattle dung delivers 40 litres of biogas, and 1 kg of chicken droppings generates about 70 litres of biogas.
[[Image:Biogas_as_source_of_energy.PNG|thumb|right|150px|[[Biogas as source of energy |Biogas as source of energy]], in Bangladesh (for credits, click the picture)]]