The term ‘Biogas’ refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. This organic matter can include green waste, manure, municipal waste, food waste and sewage. It is a renewable fuel so is attractive for users wishing to reduce their carbon footprint.
Biogas consists mainly of methane and carbon dioxide but may also contain small amounts of hydrogen sulfide (H2S), moisture and siloxanes.
An oxidation catalytic converter will help to reduce emissions of carbon monoxide and methane from an engine running on biogas, however any hydrogen sulfide and siloxanes present will shorten the life-span of the catalytic converter and may also damage the engine. For this reason it is advisable to purify biogas before it is fed into an engine. This purified biogas is referred to as ‘biomethane’.
As with catalytic converters for CNG engines, those used on biogas engines require an exhaust temperature of at least 430 ℃ before they are effective at oxidising methane.