The use of trucks running on liquefied natural gas (LNG) instead of diesel is not a suitable measure for climate protection in road freight transport. Even in an optimistic scenario, greenhouse gas (GHG) emission reductions of less than 10 % are achieved when using LNG instead of diesel.
In theory, natural gas (methane) has several properties that make it an attractive fuel for combustion engines. Due to its molecular structure methane has a lower carbon content than diesel and produces around 25 % less CO2 per unit of energy. However, natural gas must be compressed or liquefied to achieve the volumetric energy density required for its use as a transport fuel. While the volumetric energy density of LNG is still approximately 40 % lower than the volumetric energy density of diesel, it is significantly higher than that of compressed natural gas (CNG), making LNG a suitable fuel for long-haul transportation. The LNG is stored on in vacuum-insulated fuel tanks at temperatures of -125 °C to -160 °C.
Although LNG trucks have lower tailpipe CO2 emissions due to the more favourable chemical composition of the fuel, they produce other GHGs elsewhere. In particular, the operation of the vehicles leads to considerable methane emissions. When released in to the atmosphere unburnt, methane is a very potent greenhouse gas. Further CO2 and methane emissions take place during fuel extraction and supply (well-to-tank emissions, WTT).