Biogas is obtained as the one of the end product of anaerobic digestion is natural gas (methane) for energy production, nutrient rich organic slurry, and other marketable inorganic products. Biogas is a convenient energy carrier, suitable for many different applications. The biogas can be combusted in a co-generation unit to produce green energy. The simplest application of biogas is the direct use for cooking and lighting, but, nowadays, in many countries purified biogas is used for combined heat and power generation (CHP) or it is upgraded and fed into natural gas grids, used as vehicle fuel or in fuel cells. At 35 percent conversion efficiency, each pound of volatile solids digested generates kWh of energy. Thus, Calorific value of one cubic meter of the biogas is equivalent to 6 kWh or that produced with half liter of diesel oil.
