What Is Methane? Definition and Importance

Oil Flare Stack
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Methane (chemical symbol CH4) is a colorless, odorless gas composed of one carbon atom and four hydrogen atoms. Methane is also a potent greenhouse gas; when emitted, it stays in the atmosphere and affects the Earth’s climate. It is the second largest cause of global warming after carbon dioxide.

Humans have increased the amount of methane in the atmosphere about 150% since 1750. The extraction of fossil fuels like oil, gas, and coal are the largest source of methane emissions. Humans have also increased methane emissions through intensive agricultural practices, livestock production, and waste disposal. 

Where Does Methane Come From?

Over millions of years, massive quantities of organic matter from plants and animals, both in the sea and on land, become trapped in sediment and are gradually compressed and pushed deeper into the earth. Pressure and heat cause a molecular breakdown that produces thermogenic methane. 

Biogenic methane, on the other hand, is produced by microorganisms in anoxic (oxygen-less) environments that decompose organic matter in a process called fermentation, which produces methane. Anoxic environments include wetlands such as lakes, swamps, and peat bogs. Microbes inside the digestive system of animals and humans also produce methane that gets released by “passing gas” and burping.

According to NASA, about 30% of methane emissions come from wetlands. Oil, gas, and coal extraction are responsible for another 30%. Agriculture, especially livestock, rice cultivation, and waste management constitute 20%. The remaining 20% comes from a combination of smaller sources, including the ocean, biomass burning, permafrost, and—wait for it—termites.  

Natural gas constitutes the single largest anthropogenic source of methane emissions, and is released during oil and gas extraction. Oil and gas reservoirs, which often occur together, exist thousands of feet below the Earth’s surface. Reaching them requires digging wells deep in the ground. Once extracted, oil and gas are moved by pipeline. 

Methane has many beneficial uses. Natural gas is used for heating, cooking, as an alternative fuel to power some cars and buses, and in the manufacturing of organic chemicals. A decade ago, industry promoted natural gas as a cleaner “bridge fuel” to help transition away from oil. But while it emits less at the point of combustion, natural gas produces at least as much greenhouse gas emissions as other fossil fuels over its entire life cycle because of widespread leaks.

The Impact of Methane 

Greenhouse gases like methane stay in the Earth’s atmosphere, allowing sunlight to pass through but trapping heat. By increasing the concentrations of greenhouse gases in the atmosphere, humans are causing global warming.

While methane constitutes a much smaller portion of greenhouse gases overall than carbon dioxide and breaks down after about 10 years, it packs a powerful punch. Methane is about 28 times as potent as carbon dioxide. After falling in the early 2000s, methane emission levels subsequently climbed because of both fossil fuel operations and food production as people consumed more meat.

Emissions From Fossil Fuels

Gas leaks can occur from pipes and other infrastructure throughout natural gas networks, as well as from idle and abandoned wells. Flaring and venting during extraction are two other significant sources of anthropogenic methane emissions. If you’ve ever seen an oil or gas extraction operation with flames shooting from a tall pipe, that’s flaring, or burning off natural gas into the air.

Flaring is done for a variety of reasons, including safety. Because natural gas is often a byproduct of oil extraction, the oil producer may capture gas to use in its operations or deliver it to a natural gas market. But when a producer lacks access to pipelines or other infrastructure to capture and transport gas, it is flared. Low gas prices can also make it cheaper to burn off gas than sell it. Venting, on the other hand, involves the direct release of gas into the atmosphere without burning it.

Oil and gas producers and distributors estimate emissions during drilling, venting, and flaring, along with any gas that leaks from the millions of pipes and connections that make up the gas network. But independent research indicates that methane emissions are much greater than industry-reported figures

Emerging research shows that plastic products like plastic bags, household items, and synthetic clothing are additional sources of methane emissions. This is concerning because plastic production could double in the next two decades, yet direct emissions from plastic products haven’t been considered in the global methane budget, nor in climate models.

Agriculture, Livestock, and Food Waste

Cows from a dairy farm in Sherborne, Gloucestershire, United Kingdom stand next to a mound of feed and manure.

Tim Graham/ Getty Images

Agricultural methane emissions include livestock production, rice cultivation, and wastewater. Livestock constitutes the largest share—and also a growing share as global meat consumption continues to increase. According to the United Nations Food and Agriculture Organization (FAO), livestock accounts for 14.5% of total anthropogenic greenhouse gas emissions. 

The bulk of livestock emissions comes from ruminants, animals like cattle, buffalo, sheep, and camels, which produce a lot of methane during digestion, most of it released through burping. Livestock manure is an additional contributor, especially in intensive agriculture systems. Of the methane emissions from ruminants, beef and dairy cattle contribute the most. 

Food waste is another huge challenge. About a third of all food produced in the world for human consumption is never eaten, according to the FAO. That wasted food contributes significantly to overall greenhouse gas emissions (about 8%) and is a major source of methane emissions as food decomposes. 

While the most important sources of anthropogenic methane emissions are agriculture and fossil fuel extraction, humans contribute emissions in other ways. Municipal solid waste landfills are the third-largest source of human-related methane emissions in the United States, according to the EPA. There are also indirect impacts from climate change. A warming planet leads to permafrost melt, which has the potential to release more methane. Biomass burning from wildfires and intentional burning is another culprit.

Human Health Implications

Besides indirect climate-related impacts, methane emissions adversely affect air quality. Methane and other hydrocarbons in natural gas combine with nitrogen oxides to form ozone pollution. Ground-level ozone, also known as smog, exacerbates respiratory diseases like asthma and chronic bronchitis. 

Studies have also linked natural gas drilling and fracking with drinking water contamination so serious that water from taps in homes near drilling operations could be set on fire due to high methane levels. Although limited research indicates that methane isn’t harmful to drink, it can cause explosions and accumulate in enclosed spaces

Regulations

Because methane is both a very potent greenhouse gas and short-lived compared to carbon dioxide, significant methane emissions reductions would have a rapid and important impact on atmospheric warming

One recent study found that moving quickly to cut methane emissions could slow the rate of the Earth’s warming by as much as 30%. But time is short: Methane levels surged in 2020. Significant actions to reverse that trend include reducing oil- and gas-related leaks and intentional gas releases, cleaning up abandoned coal mines, reducing meat and dairy consumption, using burp-reducing cattle feed supplements, and implementing technologies to capture landfill emissions. 

A week after taking office in 2021, President Joe Biden signed an executive order to ban fossil fuel extraction on public lands, responsible for 25% of U.S. greenhouse gas emissions.

On Earth Day 2021, Biden convened the Leaders Summit on Climate and pledged the U.S. would cut greenhouse gas emissions 50% by decade’s end. 

The following week, the U.S. Senate approved the restoration of a key part of the Obama administration’s methane strategy: oil and gas performance standards that target prevention of methane leaks from wells and pipelines. The vote to reinstate the regulations, which the Trump administration dismantled, was regarded as a major step toward meeting new emission targets. 

During the Earth Day summit, leaders of Canada, Norway, Qatar, Saudi Arabia, and the United States, together representing 40% of global oil and gas production, announced the formation of a cooperative forum to develop net-zero emission strategies, which would include expanding renewable energy and shifting away from reliance on hydrocarbons, including limiting methane emissions. 

In 2020, the European Union adopted a methane strategy to cut emissions as part of the European Green Deal, which lays out an ambitious plan to achieve carbon neutrality by 2050, including methane abatement. As the world prepared for the COP26 climate summit in Glasgow, pressure also mounted on China to do more. Whether the collective efforts will be enough to slow global warming and avoid a disastrous tipping point is uncertain, but momentum is accelerating.  

Technology also has a role to play. Methane-capture technologies allow for the storage and reuse of methane emitted by landfills, fossil fuel operations, manure, and other sources as fuel or even as a component of products like clothing and packing materials. Technological innovation alone will not reverse the upward emissions trend. But every effort counts.