This is a breakdown by source of the yearly methane (CH4) emissions from human activities and processes. It is expressed as weight in megatonnes (Mt). Human-induced methane emissions increase atmospheric methane, which is warming the Earth. The sources of human methane emissions are
Livestock emits methane that is produced in the animals' digestive system. Most methane is emitted from the mouth during rumination. A much smaller amount of methane is emitted from the manure. Depending on how the manure is managed, i.e., wet or dry, more methane is emitted. Wet management leads to higher methane emissions than dry management. However, dry management also emits nitrous oxide (N2O), which is another potent greenhouse gas.Wikipedia: Atmospheric methane; Farm animals
Fugitive methane emissions are from the intentional and accidental release of methane, which happens during the extraction, storage, and transportation processes in the fossil fuel industry. Examples are methane leaks during oil and gas handling, storage, transport, incomplete combustion, and many more. Also, methane is deliberately ventilated from mines during the extraction of coal.
Methane is a primary part of “gas”, also called “natural gas” or “fossil gas”. Natural gas is used, for example, for heating and electricity generation, whereby it emits CO2 during the combustion process. However, when natural gas leaks (unburned) it contains a lot of fugitive methane emissions.Wikipedia: Natural gas
Waste from landfills and wastewater produces a lot of methane when biodegradable material breaks down without oxygen.Wikipedia: Atmospheric methane; Landfills and wastewater treatment
Crop production emissions are largely from rice cultivation, which generates large amounts of methane during plant growth. These emissions are from flooded paddies, which create the swamp-like environment of rice fields. There are agricultural techniques to reduce emissions significantly, like periodic drainage and aeration. Rice is the main staple for about half the world’s population, and its emissions are a significant part of total human methane emissions.Wikipedia: Atmospheric methane; Rice agriculture
Fuel combustion emissions are mostly from the incomplete combustion of fossil fuels. As mentioned before, natural gas consists largely of methane, and when the combustion does not happen completely, methane enters the atmosphere.
Other human-induced methane emissions include industrial processes and product uses.
The unit megatonne (Mt) describes the weight of emitted methane per year.Wikipedia: Megatonne
Emissions from livestock and fugitive emissions from fossil fuels are the two largest contributors, each accounting for about a third of total emissions. Livestock emissions are still growing on a yearly basis with minimal fluctuation. Fugitive emissions from fossil fuels rose rapidly after the second world war until the 1970s and continued increasing until around 2005; since then, the emissions have been relatively stable till this day. Emissions related to waste are also very significant and also continue to increase steadily every year. Crop production and fuel combustion have had relatively stable emissions for a long time. Other sources of human-induced methane emissions are negligible.
The PRIMAP-hist dataset is a rich dataset that combines several published sources to create a historical emissions time series for methane and many other greenhouse gasses.PRIMAP-hist
PRIMAP-histCredits: Gütschow, J. and Pflüger, M.: The PRIMAP-hist national historical emissions time series (1750-2021) v2.4.2 (2.4.2), https://doi.org/10.5281/zenodo.7727475, 2023.Update cycle: yearlyDelay: 1-2 years