Biogas is the primary useful product produced by the anaerobic digestion (AD) process.
It is similar to natural gas, in that it is largely made up of methane, being about 50-70% methane and 25-45% carbon dioxide (CO2), along with some impurities.
Biogas is usually burned locally to the AD plant, to produce electricity and/or heat.
Depending on its composition, the higher and lower heating values of biogas range from about 19 to 26 megajoules (MJ) of energy per cubic metre (m3) of gas.
In practical terms, this means that one m3 of biogas can produce about 6 kilowatt-hours (kWh) of energy.
Biogas can also be injected into the gas main grid if it is cleaned of CO2, to make the methane content closer to that of natural gas, about 95% methane. At this point the biogas becomes known as biomethane.
Biomethane can also be used in motor vehicles, but currently this isn’t a common application.
Page Last Updated: 15 December 2020