Processed biogas is methane

Processed biogas − or biomethane − is chemically almost identical to natural gas. The minimum methane content requirement for processed biogas is becoming established at the level of 95–98%. Because natural gas and processed biogas consist mainly of methane, processed biogas can be used alongside natural gas to fuel natural gas vehicles (NGVs) and the gases can also be mixed. Biogas differs from natural gas in that it is renewable and carbon dioxide neutral in terms of its climate effects.

In most cases the transport use of processed biogas calls for a reserve fuel system. This is particularly relevant when gas is used to fuel heavy vehicles such as buses and lorries as they do not have engines capable of running on two fuels like bifuel cars do. In such cases there are two alternatives available: connecting the biogas system to the natural gas network or equipping the biogas filling station with a liquefied natural gas (LNG) storage tank and vaporiser.

More than half the gas used in Sweden as a transport fuel is processed biogas and the rate in Switzerland is almost 40%. Other countries utilising biogas in transport include Austria, the Netherlands and Spain.