Landfill gas is a waste product that is relatively easy to obtain.
Bacteria decompose the organic part of the waste and thereby produce landfill gas. It contains the flammable methane that gas engines run on. However, depending on the type of waste that decomposes, the composition of landfill gas is different and so is the methane content. On average, between 35 and 60 percent of landfill gas consists of methane, the rest is carbon dioxide. And the amount of methane has a great influence on the performance of the engine. If the methane number of the gas is too low, the engines begin to knock: then parts of the compressed gas-air mixture explode even before it has been fully ignited by the spark of the spark plug and the engine's performance drops.