The term 'biogas' is commonly used to refer to a gas which has been produced by the biological breakdown of organic matter in the absence of oxygen. Biogas is a mixture that is produced by microorganisms during the decomposition of vegetable and animal wastes in an oxygen‐free environment. It consists of methane (60–70%), carbon dioxide (30–40%) and hydrogen‐sulfide (0–2%).
For its production, plant seeds that are rich in oil (e.g. sunflower), vegetables rich in carbohydrates (e.g. potato, wheat, corn, beet), fiber‐rich plants (e.g. flax), other plant and tree remains (e.g. branches, hay, roots, bark), and animal remains can be utilized as raw material. Municipal and industrial waste can also be utilized on the condition that they are purified from inorganic materials like plastic and glass.