Biogas is a result of anaerobic fermentation of organic materials. Biogas can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste. Biogas is a metabolic product of the participating methanogens and acidogens, the prerequisites for its production are a lack of oxygen, a pH value from 6.5 to 7.5 and a constant temperature of 35-45°C (mesophilic) or 45-55°C (thermophilic).
The digestion period or retention period is typically between 10 and 30 days depending upon the type of digestion employed. The anaerobic digestion systems of today operate largely within the mesophilic temperature range. Biogas is primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of Hydrogen Sulfide (H2S) moisture. The gases methane, hydrogen, and carbon monoxide (CO) can be combusted or oxidized with oxygen. This energy allows biogas to be used as a fuel; it can be used for any heating purpose, such as cooking. It can also be used in a gas engine to convert the energy in the gas into electricity and heat.