Methane has also been detected in interstellar clouds.
Biogas, produced by wetlands and landfills, is another source of methane.
Being the simplest hydrocarbon, the combustion of methane produces more heat per gram than other hydrocarbons.
One liter of methane clathrate solid would contain, on average, 168 liters of methane gas (at 25 °C and 100 kPa pressure).
Consequently, it is difficult to predict future concentrations of methane in the atmosphere .
Methane is not toxic, but because it is highly flammable it can form mixtures with air that are explosive.
The Earth's mantle is the main reservoir of methane, and large quantities of this gas have been found in geological deposits known as natural gas fields.
Large quantities of methane have been found in sediments on the ocean floor, where it is trapped in cage-like ice crystals known as methane clathrates.
To produce any of these chemicals, methane is first made to react with steam in the presence of a nickel catalyst at high temperatures (700–1,100 °C).
Methane can also be extracted from coal deposits.
When methane is burned in the presence of oxygen, the reaction—called a combustion reaction—produces carbon dioxide, water, and a large amount of heat.
The researchers noted that "this newly identified source may have important implications for the global methane budget and may call for a reconsideration of the role of natural methane sources in past climate change."
Methane in the Earth's atmosphere is an important "greenhouse gas" that contributes to the "greenhouse effect."
Biogas is a mixture of methane, carbon dioxide, and small amounts of other gases.
Traces of methane gas are present in the thin atmosphere of the Earth's Moon.
Methane is widely used as a fuel, but it is also a starting material for the synthesis of other compounds.
Two additional sets of processes that remove minor quantities of methane are: (a) the activity of aerobic microbes in soils, and (b) reactions with ·OH, ·Cl, and ·O(1D) in the stratosphere.
The average concentration of methane at the Earth's surface in 1998 has been estimated as 1,745 ppb (parts per billion) .
Until recently, the consensus view has been that most of the methane from biological sources was produced by processes in oxygen-poor environments.
When methane is made to react with chlorine gas, various chloromethanes are produced: chloromethane, dichloromethane, chloroform, and carbon tetrachloride.
Scientists think that early in the Earth's history—about 3.5 billion years ago—there was one thousand times as much methane in the atmosphere as there is now.
Methane clathrates are thought to be formed when methane gas streams rising from geological faults come in contact with cold seawater.
Each molecule of methane is small, consisting of four atoms of hydrogen attached to a single atom of carbon through covalent bonds.
Acetylene may be replaced by less costly substitutes, and the chloromethanes are used less often because of health and environmental concerns.
Nonetheless, the rates of emission of methane by different sources in the biosphere are highly variable and difficult to assess.
Methane has been detected or is believed to exist in several locations of the solar system beyond our planet, as listed below.
Based on these processes, the estimated lifetime of methane in the atmosphere has been calculated to be 8.4 years .
Large deposits of methane have been found in a form known as methane clathrate, under sediments on the ocean floors.
Currently, methane is a minor constituent of our planet's atmosphere.
When structures are built on or near landfills, methane off-gas can penetrate the building interior and expose occupants to significant levels of methane.
Under the proper conditions, methane reacts with all the halogens.
Nonetheless, methane is still the principal starting material for the manufacture of hydrogen.
Methane is the simplest hydrocarbon, with the chemical formula CH4.
Natural gas fields are currently the main source from which methane is extracted for human use.
At room temperature and pressure, methane is a colorless, odorless gas, lighter than air.
Greenhouse gases (including water vapor, carbon dioxide, and methane) absorb the heat being emitted and prevent it from escaping into space.