Biogas is the result of the fermentation of organic matters of different origins (animal waste, farming residues, urban sewage, humid fraction of urban waste, etc.)  in the absence of oxygen through a biological process, known as anaerobic digestion, that produces a composed mixture from methane and carbon dioxide (biogas). The combustion of biogas can generate thermal energy, electric energy or, with cogeneration systems, the combination of both.
Biogas now represents one of the most interesting resources in the field of development and promotion of renewable energy sources because of its specific production and use characteristics.