Methane is largely a product of incomplete decomposition and is produced by a group of bacteria called methanogens under anaerobic conditions. The major sources of methane include freshwater wetlands, enteric fermentation in cattle and flooded rice fields. Biomass burning also produces methane. Major gases contributing in greenhouse effect with their percentage contribution are given in the given pie chart. Efficient engine (for example, multi point fuel injection engine) can reduce the unburnt carbons (like methane etc.) in auto emission.