Biogas consists of 50-60 percent of methane, a combustible gas, with the remainder being largely CO2. Natural gas or compressed natural gas (CNG) consists of 98 percent of methane. In order to be able to feed biogas into the natural gas network, it must have the same methane content as natural gas. To achieve that, the biogas will be scrubbed (= “washed”), so as to remove the CO2, for which a number of techniques are now available.
When biogas has a methane content of 98 percent, it is called “biomethane”, which can be fed into the existing gas network and tapped at any place, say at a gas pump at a natural gas fuelling station. Every vehicle operated with gas can be fuelled with biomethane without causing any problems.
A vehicle fueled with biomethane reduces the CO2 emissions by up to 90 percent in comparison to a vehicle run with a gasoline engine – and decreases the costs for the driver per kilometer by 50 percent. The processing of biogas into biomethane began in the Pliening biogas plant near Munich in late 2006. Today, more than 160 plants feed their gas directly into the gas network. The gas can be tapped from the network anywhere and be converted into power or heat; it can be used as fuel for vehicles or it can be stored for several months. If biomethane is liquefied into liquefied natural gas (LNG), it can – due to its high energy density – even be used as fuel for trucks and ships. The first ships with LNG engines are currently put into operation.