methane: a colourless flammable gas produced naturally from rotting organic waste, as in landfill sites or animal excreta. Formula: CH4. Methane is produced naturally from rotting vegetation in marshes, where it can sometimes catch fire, creating the phenomenon called will o the wisp, a light flickering over a marsh. Large quantities may also be formed in the rumen of cattle. It occurs as the product of animal excretions in livestock farming. Excreta from livestock can be passed into tanks where methane is extracted leaving the slurry which is then used as fertiliser. The methane can be used for heating or as a power source. Methane is also a greenhouse gas, and it has been suggested that methane from rotting vegetation, from cattle excreta, from water in paddy fields, and even from termites nests, all contribute to the greenhouse effect. Understanding the production and management of methane can help farmers reduce greenhouse gas emissions and utilize methane as a renewable energy source, contributing to environmental sustainability and farm profitability.