[2]. It is smokeless, hygienic and more convenient to use than other solid fuels [3]. Average temperature of Bangladesh ranges from 20oC to 30o C. This is an ideal temperature for the fermentation of organic materials. So biogas is a prospective alternative source of energy in Bangladesh. Anaerobic digestion has been considered as waste-to-energy technology, and is widely used in the treatment of different organic wastes, for example: organic fraction of municipal solid waste, sewage sludge, food waste, animal manure, etc [4].
Anaerobic treatment comprises of decomposition of organic material in the absence of free oxygen and production of methane, carbon dioxide, ammonia and traces of other gases and organic acids of low molecular weight [5]. Raw materials for biogas fermentation such as cow dung, poultry waste, water hyacinth, straw, weeds, leaf, human and animal excrement, domestic rubbish and industrial solid and liquid wastes are easily available in Bangladesh.