Biogas is a mixture of gas resulting from the decomposition of organic matter in conditions without the presence of oxygen (anaerobic conditions). The gas mixture formed consists mainly of methane (50 – 75 vol%) and carbon dioxide (25 – 50 vol%). In addition, biogas contains small amounts of hydrogen, hydrogen sulfide, ammonium, and other trace gases.

Biogas is used to produce thermal energy, electricity, and thermal (cooling) energy as part of a cogeneration plant (CHP) and to produce pure methane (enriched biogas).

The production of biogas contributes to the reduction of methane emissions, a gas with a greenhouse effect that has a multiple greater impact than carbon dioxide.

Biogas is generated from liquid and solid animal manure, as well as organic waste and energy crops. The process of biogas production is divided into several phases: hydrolysis, acidogenesis, acetogenesis and methanogenesis.

Biogas power plants are plants where biogas is produced efficiently under controlled conditions.