Methane is released from both anthropogenic (man-made) and natural sources. Landfills, oil and natural gas systems, agricultural operations, coal mining, stationary and mobile combustion, wastewater treatment, and some industrial processes are examples of anthropogenic emission sources. Natural sources include wetlands, soil, animals, and vegetation. The amount of methane emitted into the atmosphere varies by source category: landfills emit nearly all of their methane within one year; agriculture is the largest single source of atmospheric methane, accounting for about 25% of global emissions; and waste management is another large source at 28%. Other natural sources such as decomposing vegetation or livestock contribute significantly too.
People have been aware of the threat that burning fuels in an unvented way poses to the environment for many years. In fact, up until the early 1900s, most fuel was burned without any form of pollution control, with the result that urban areas often had very poor air quality. This changed when two Swedish scientists, Svante Arrhenius and Fredrick Lindblom, proposed solutions for reducing pollution from fossil fuels. They suggested that increasing the temperature of fuel burners could reduce the release of pollutants into the atmosphere. The technology needed to carry out this idea wasn't available at the time but it forms the basis of modern thermal oxidizers. Today, these devices use platinum or other precious metals as catalysts to speed the oxidation process, which then prevents further oxidation of the methane inside them.
Human activities that emit methane include the production of fossil fuels, the cattle sector, rice farming, biomass burning, and waste management. These operations emit large amounts of methane into the atmosphere. Changes in land use also affect how much methane is released into the environment. For example, deforestation and soil degradation allow bacteria to consume much of the organic carbon content of the soil, which reduces its ability to store carbon.
Methane is a greenhouse gas more potent than CO2 over a short time frame (i.e., decades). It also depletes oxygen from the air, causing climate change and forming ozone which can lead to respiratory problems for those who live with it daily. However, since methane is absorbed by soil, trees, and other natural processes, it does not last as long as CO2 in the atmosphere. Therefore, even if you stopped emitting all methane today, it would still be around for future generations to enjoy.
In conclusion, humans produce about 9 million tons of methane each year, mostly from livestock and fossil fuel sources. This amount is enough to fill up half of London every day. Thus, methane is an important factor in determining how fast climate change progresses, although it is also consumed again by living things (including animals) and becomes part of the carbon cycle.
Natural gas is mostly composed of methane. Methane is released into the atmosphere through natural gas extraction, processing, storage, transmission, and distribution, as well as crude oil production, refining, transportation, and storage. Coal mining also contributes to CH4 emissions. The amount of natural gas that exists in the world is estimated to be approximately 3200 billion cubic meters (bcm), while the amount of carbon dioxide emitted per year is roughly equal to that of gasoline consumption by all passenger vehicles in America.
Methane has a higher global-warming potential than other greenhouse gases such as CO2 or NOx. It can remain in the atmosphere for up to 20 years, but if burned it will contribute to 16 percent of carbon dioxide emissions over the long term.
Methane emissions are generally divided into two categories: direct emissions from landfills and manure management practices, and indirect emissions through decomposition of plant material. Landfills are one of the most important sources of methane emissions in the United States; according to some estimates, they account for more than 25% of U.S. methane emissions. Indirect emissions through decomposition of plant material are significant in tropical countries like India or Brazil where landfills are scarce.
Manure management is another source of methane emission. In fact, livestock production accounts for about 15% of methane emissions worldwide, with the largest source being cow flatulence.
Methane is a potent greenhouse gas generated through human activities such as natural gas leaks and cattle production, as well as natural sources such as wetlands. Methane is a climatic pollutant with a limited air lifespan of about 12 years. The main source of atmospheric methane is from animals via their manure, but there are other sources including agriculture and fossil fuel industries. Reduction of these sources can reduce atmospheric methane levels.
In addition to being a greenhouse gas, methane is also highly flammable. It is estimated that 10% of all fires in the United States are caused by livestock operations, most of which are due to manure storage facilities. Manure storage facilities often use open-air pens or tanks that can leak gas if they are not properly constructed.
Livestock production accounts for approximately 14% of global carbon dioxide emissions. The main source of methane pollution comes from livestock production itself (e.g., rice paddies used as livestock feed), but it also results from landfills, sewage treatment plants, and garbage dumps that contain food waste and animal feces.
There are several ways to reduce your impact on climate change and pollution at the same time: stop driving cars, eat less meat, use renewable energy, etc. But if you want to make a real difference, you need to invest in sustainable practices.
Methane is mined. Methane is generated by both natural sources, such as wetlands, and human activities, such as agriculture and the production of fossil fuels. However, coal may also be a generator of methane. The gas leaks from coal seams and is frequently drained off through ventilation systems to keep workers safe. This gas is called "free gas" and includes all of the molecules that were once part of hydrocarbons but have now separated out as gaseous molecules.
Coal contains about 5% free gas. The rest of the gas is dissolved in the solid matrix of the coal. Some of this gas can be released when the coal is heated above 200 degrees Celsius, but most of it remains trapped until the heat of deep mining or combustion releases it.
Free gas has a significant impact on the economics of coal mining. It increases the cost of extraction because more energy is required to release it, and it also reduces the value of the coal because some of its energy is lost as gas instead of being used.
Methane is also generated by microorganisms during anaerobic digestion of organic material containing carbon and hydrogen, such as manure, food waste, cellulose, and protein-rich materials. Manure is the main source of methane in livestock farming. Other sources include rice paddy soils, fish ponds, and decomposing plant matter.
Biogenic methane is created by biological (plant and animal) processes. This is carbon that has recently been generated from carbon dioxide (CO2) in the environment. Methane emissions contribute to further warming (as methane is a more potent greenhouse gas than CO2). Methanogenesis is the process by which bacteria produce methane. The three main sources of biogenic methane are wetlands, soil, and manure storage facilities.
Wetlands and grasslands store large amounts of carbon in their tissues. When these lands are drained or burned, much of this carbon is released into the atmosphere. Wetlands also act as natural filtors, removing pollutants from water bodies. Around one-fifth of the world's land area is covered by wetlands, but only 5% of that area is protected to conserve its carbon content. Grasslands cover about 15 million km2 of the planet's land surface. Like wetlands, when these lands are converted for agriculture or fuel production, they can no longer retain carbon. Manure storage facilities are another source of biogenic methane. Animals, when fed on diets containing high levels of starch or sugar, produce several gases including some types of methane. Storing this gas is problematic because it creates greenhouse gas emissions as well as hazardous substances that must be dealt with after the animals die or are removed from the facility.
Methanogens are a group of organisms that create methane.