Biogas is generated when bacteria degrades biological material in the absence of oxygen, in a process known as anaerobic digestion. Since biogas is a mixture of methane (also known as marsh gas or natural gas) and carbon dioxide it is a renewable fuel produced from waste treatment. Raw biogas can be combusted to produce heat and/or power; it also can be transformed into biomethane through a process known as scrubbing – which removes impurities including carbon dioxide, siloxanes and hydrogen sulphides – followed by compression. Biomethane can be injected directly into natural gas networks and used as a substitute for natural gas in internal combustion engines without fear of corrosion.