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what is biogas

Biogas is also known as marsh gas, sludge gas or landfill gas. In comparison to a biogas plant where the process is controlled, the naturally produced emissions leak into the atmosphere. In a biogas plant the produced biogas is collected and does not leak into the atmosphere thus it does not provide an emission source of greenhouse gases but represents active environmental protection.
Biogas is a gaseous mixture consisting mainly of methane (40 – 75 %) and carbon dioxide (25 - 55 %). Additionally, it contains some trace gases such as NH3, H2S or H2 in concentrations of 0 – 10 %.
Different substrates used for anaerobic digestion processes are liquid manure, sewage, maize, grass, sunflower, biodegradable waste, slaughterhouse waste, vegetable and fruit waste.
Organic substrates are digested by microorganisms if provided with suitable environmental conditions: in the absence of air (anaerobic climate) and the absence of light and at adequate temperatures from 35 °C. As end-product of their metabolism these microorganisms produce biogas.
Further end-products from anaerobic digestion are solid or liquid residues which can be used as fertiliser in agriculture.