Biogas results from the anaerobic digestion process of certain bacteria. The gas produced consists mainly of methane (CH4), carbon dioxide (CO2), moisture and hydrogen sulfide (H2S) as well as traces of carbon monoxide (CO) nitrogen (N2) and Oxygen (O2). Biogas is one of the most important technologies for the production of power from renewable and clean resources. It is a safe and clean application for treating animal manure and organic waste from industries and households. Biogas technology creates employment opportunities and reduces pollution into the air, water and soil. The energy produced from biogas can replace natural gas or be utilized in district heating and electricity.

Anaerobic digestion is the process in which certain microorganisms decompose organic matter into biogas without the presence of oxygen. The produced biogas is a colorless, odorless and flammable gas which has an energy content of 37.3 MJ/m3. The percent of methane to carbon dioxide varies depending on the input materials (feedstock) and the completeness of the process. The biomass used in this process has high moisture content, such as animal dung, sewage sludge, crop byproducts, and organic waste from households and industries.

Any organic waste has the ability to produce biogas: manure, animal slurry, fruit and vegetable waste, slaughter house waste, meat packing waste, dairy factory waste, brewery and distillery waste, primary wastewater sludge etc. Fiber-rich waste such as wood and leafs are difficult to digest and make poor feedstock for digesters.

The biogas process is a natural process that takes place in a variety of anaerobic environments, such as the intestinal tract of animals, marine and fresh water sediment, sewage sludge, paddy fields, water logged soils, volcanic hot springs and deep sea hydrothermal vents. Anaerobic digestion also occurs in landfills, where municipal waste was buried in soil with very low oxygen concentration. The produced biogas (methane) can be collected by pipeline networks and utilized as a source of energy.

Anaerobic degradation or digestion involves the breakdown of biomass through the concerted efforts of a wide range of microorganisms in the absence of oxygen. The general principal of biomass is the degradation of organic materials (e.g. protein, fats, carbohydrates) in anaerobic conditions, where bacteria convert the organic material into methane, carbon dioxide and water.