Rice is grown in paddy fields, and in order for the grain to flourish, these fields need to be flooded. The amount of water needed ends up blocking oxygen from getting to the soil, which creates the perfect conditions for bacteria that release methane.

Rice is the nutritious staple crop for more than half of the world’s people, but growing rice produces methane, a greenhouse gas more than 30 times as potent as carbon dioxide. Methane from rice contributes around 1.5 percent of total global greenhouse gas emissions, and could grow substantially.

Methane emission from rice fields is the result of bacterial processes — production in flooded anaerobic microsites and consumption (oxidation) in aerobic microsites). Flooding of rice fields promotes anaerobic fermentation of C sources supplied by the rice plants and other incorporated organics, resulting in the formation of CH4.

Methane in rice paddies is produced by microscopic organisms that respire CO2, like humans respire oxygen. More CO2 in the atmosphere makes rice plants grow faster, and the extra plant growth supplies soil microorganisms with extra energy, pumping up their metabolism.