Methane is generated from coal mining operations and from some natural gas pipelines. Greenhouse gases are also released during oil and gas production. Over decades, forests build up an important store of carbon in trees, soil and fallen leaves. When land is cleared, much of this is rapidly converted back to carbon dioxide by burning or decay. Farming Animals, particularly cattle and sheep, produce methane as food breaks down inside them.
Some fertilisers release nitrous oxide.
Rice production in paddy fields generates methane under water. Breakdown of wastes When organic materials, food scraps, garden wastes and paper are dumped in landfills, their decay generates carbon dioxide and methane. Sewage and wastewater treatment plants also release these gases as they break down wastes. Industrial processes Cement and aluminium production, and some other processes involve chemical reactions which produce greenhouse gases. The ocean absorbs carbon dioxide from atmosphere.