Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Methane shopping experience:

1. Compare - without doubt the biggest advantage that the Methane offers shoppers today is the ability to compare thousands of Methane at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a Methane? Wrong! If the Methane is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about Methane then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling Methane? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Methane and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your Methane wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your Methane then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the Methane site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about Methane, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your Methane, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.

{| class="toccolours" border="1" style="float: right; clear: right; margin: 0 0 1em 1em; border-collapse: collapse;"! | Methane|-| align="center" colspan="2" bgcolor="#ffffff" | |-! | General|-| Other names || Marsh gas Firedamp || |-| [Simplified molecular input line entry specification || C|-| Molar mass ] || |-| International Chemical Identifier || InChI=1/CH4/h1H4|-! | Properties|-| Density and Phase (matter) || 0.717 kg/m³, gas|-| Soluble in Water (molecule) || 3.5 mg/100 ml (17 °C)|-|-| Material safety data sheet || Methane (data page)#Material Safety Data Sheet |-| Directive 67/548/EEC || Highly flammable (F+)|-| NFPA 704 ] || |-| List of S-phrases || , , , |-| Flash point ] || 537 °C|-| Maximum burning
temperature: || 2148 °C|-| Explosive limits ]|-| Methane (data page)#Structure and properties |||-| Methane (data page)#Thermodynamic properties |||-| Methane (data page)#Spectral data || UV/VIS spectroscopy, Infrared spectroscopy, NMR spectroscopy, Mass spectrometry|-! | Related compounds|-| Related alkanes ]Propane[Chloromethane
Formic acid
Formaldehyde|-| | Except where noted otherwise, data are given for
materials in their [standard statewikipedia:Chemical infobox|-|}Methane is a chemical compound with the molecular formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees. Combustion one molecule of methane in the presence of oxygen releases one molecule of (carbon dioxide) and two molecules of : Methane's relative abundance and clean burning process makes it a very attractive fuel. However, because it is a gas (at normal temperature and pressure - see, STP) and not a liquid or solid, methane is difficult to transport from the areas that produce it to the areas that consume it. Converting methane to derivatives that are more easily transported, such as methanol, is an active area of research. Certain microorganisms can effect this selective oxidation using enzymes called methane monooxygenases.

Methane is a relatively potent greenhouse gas with a high global warming potential (i.e., warming effect compared to carbon dioxide). IPCC Third Assessment Report The Third assessment report of the IPCC stated that when averaged over 100 years each kg of warms the Earth 25 times as much as the same mass of . The Fourth assessment report has updated this number to include indirect effects and states that the relative impact of to averaged over 20 years is 72. IPCC Fourth Assessment Report. The reason for this discrepancy is that methane in the atmosphere is eventually oxidised, producing carbon dioxide and water. As a result, methane in the atmosphere has a half life of seven years (every seven years, the amount of methane halves).

So far, the radiative forcing (global warming) effect of methane has been about one-third of that of CO2 . However, there is a large, but unknown, amount of methane in methane clathrates in the ocean floors. Global warming could release this methane, which could cause a further sharp rise in global temperatures. Such releases of methane may have been a major factor in previous major extinction events. The Earth's crust(geology) also contains huge amounts of methane. Large amounts of methane are produced anaerobically by methanogenesis. Other sources include mud volcanoes which are connected with deep geological faults.

Properties Methane is the major component of a natural gas, about 97% by volume. At room temperature and standard pressure, methane is a colorless, odorless gas; the smell characteristic of natural gas is an artificial safety measure caused by the addition of an odorant, often methanethiol or ethanethiol. Methane has a boiling point of −161°Celsius at a pressure of one Atmosphere (unit). As a gas it is flammable only over a narrow range of concentrations (5–15%) in air. Liquid methane does not burn unless subjected to high pressure (normally 4–5 atmospheres.)

Potential health effects Methane is not toxic; however, it is highly flammable and may form explosive mixtures with air. Methane is violently reactive with oxidizers, halogens, and some halogen-containing compounds. Methane is also an asphyxiant gas and may displace oxygen in an enclosed space. Asphyxia may result if the oxygen concentration is reduced to below 19.5% by displacement. The concentrations at which flammable or explosive mixtures form are much lower than the concentration at which asphyxiation risk is significant. When structures are built on or near landfills, methane off-gas can penetrate the buildings' interiors and expose occupants to significant levels of methane. Some buildings have specially engineered recovery systems below their basements to actively capture such fugitive off-gas and vent it away from the building. An example of this type of system is in the Dakin Building, Brisbane, California.

Reactions of methane Main reactions with methane are: combustion, steam reforming to syngas, and halogenation. In general, methane reactions are hard to control. Partial oxidation to methanol, for example, is difficult to achieve; the reaction typically progresses all the way to carbon dioxide and water.

Combustion In the combustion of methane, several steps are involved:

Methane is believed to form a formaldehyde (HCHO or ). The formaldehyde gives a formyl Radical (chemistry) (HCO), which then forms carbon monoxide (CO). The process is called oxidative pyrolysis:



Following oxidative pyrolysis, the oxidizes, forming , replenishing the active species, and releasing heat. This occurs very quickly, usually in significantly less than a millisecond.



Finally, the CO oxidizes, forming and releasing more heat. This process is generally slower than the other chemical steps, and typically requires a few to several milliseconds to occur.



Hydrogen activation The strength of the carbon-hydrogen covalent bond in methane is among the strongest in all hydrocarbons, and thus its use as a chemical feedstock is limited. Despite the high activation barrier for breaking the C–H bond, is still the principal starting material for manufacture of hydrogen in steam reforming. The search for catalysts which can facilitate C–H bond activation in methane and other low alkanes is an area of research with considerable industrial significance.

Reactions with halogens Methane reacts with all halogens given appropriate conditions, as follows:



where X is a halogen: fluorine (F), chlorine (Cl), bromine (Br), or iodine (I). This mechanism for this process is called free radical halogenation.

Uses Fuel For more on the use of methane as a fuel, see: natural gas

Methane is important for electrical generation by burning it as a fuel in a gas turbine or steam boiler. Compared to other hydrocarbon fuels, burning methane produces less carbon dioxide for each unit of heat released. Also, methane's heat of combustion is about 802 kJ/mol, which is lower than any other hydrocarbon, but if a ratio is made with the molecular mass (16.0 g/mol) divided by the heat of combustion (802 kJ/mol) it is found that methane, being the simplest hydrocarbon, actually produces the most heat per unit mass than other complex hydrocarbons. In many cities, methane is piped into homes for domestic heating and cooking purposes. In this context it is usually known as natural gas, and is considered to have an energy content of 1,000 BTU/standard cubic foot.

Methane in the form of compressed natural gas is used as a fuel for vehicles, and is claimed to be more environmentally friendly than alternatives such as gasoline/petrol and diesel. Research is being conducted by NASA on methane's potential as a rocket fuel. One advantage of methane is that it is abundant in many parts of the solar system and it could potentially be harvested in situ, providing fuel for a return journey.

Industrial uses Methane is used in industrial chemical processes and may be transported as a refrigerated liquid (liquefied natural gas, or LNG). While leaks from a refrigerated liquid container are initially heavier than air due to the increased density of the cold gas, the gas at ambient temperature is lighter than air. Pipeline transports distribute large amounts of natural gas, of which methane is the principal component.

In the chemical industry, methane is the feedstock of choice for the production of hydrogen, methanol, acetic acid, and acetic anhydride. When used to produce any of these chemicals, methane is first converted to synthesis gas, a mixture of carbon monoxide and hydrogen, by steam reforming. In this process, methane and steam react on a nickel catalyst at high temperatures (700–1100 °C).



The ratio of carbon monoxide to hydrogen in synthesis gas can then be adjusted via the water gas shift reaction to the appropriate value for the intended purpose.



Less significant methane-derived chemicals include acetylene, prepared by passing methane through an electric arc, and the chloromethanes (chloromethane, dichloromethane, chloroform, and carbon tetrachloride), produced by reacting methane with chlorine gas. However, the use of these chemicals is declining, acetylene as it is replaced by less costly substitutes, and the chloromethanes due to health and environmental concerns.

Sources of methane Natural gas fields The major source of methane is extraction from geological deposits known as natural gas fields. It is associated with other hydrocarbon fuels and sometimes accompanied by helium and nitrogen. The gas at shallow levels (low pressure) is formed by anaerobic organism decay of organic matter and reworked methane from deep under the Earth's surface. In general, sediments buried deeper and at higher temperatures than those which give Petroleum generate natural gas. Methane is also produced in considerable quantities from the decaying organic wastes of solid waste landfills.

Alternative sources Apart from gas fields an alternative method of obtaining methane is via biogas generated by the fermentation (biochemistry) of organic matter including manure, wastewater sludge, municipal solid waste (including landfills), or any other biodegradable feedstock, under anaerobic conditions. Methane hydrates/clathrates (icelike combinations of methane and water on the sea floor, found in vast quantities) are a potential future source of methane. Some say that significant quantities are also produced by cattleburp. This however, remains to be proven and most scientists refute this as a fact. http://www.mycattle.com/health/dsp_health_article.cfm?storyid=10045http://news.bbc.co.uk/1/hi/scotland/4582174.stm The livestock sector in general (primarily cattle, chickens, and pigs) produces 37% of all human-induced methane".{{cite web |url=http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.htm|title=Livestock’s Long Shadow–Environmental Issues and Options|accessdate=2007-01-04--> However animals "that put their energies into making gas are less efficient at producing milk and meat". Early research has found a number of medical treatments and dietary adjustments that help limit the production of methane in ruminants.http://news.nationalgeographic.com/news/2005/08/0816_050816_cowpollution_2.html http://news.nationalgeographic.com/news/2002/05/0509_020509_belch.html

Industrially, methane can be created from common atmospheric gases and hydrogen (produced, perhaps, by electrolysis) through chemical reactions such as the Sabatier process, Fischer-Tropsch process. Coal bed methane extraction is a method for extracting methane from a coal deposit.

A recent scientific experiment has also yielded results pointing to the fact that all plants produce methane, and as the climate warms they produce more Methane emissions from terrestrial plants under aerobic conditions Nature, January 12, 2006. In fact 600 million metric tons of methane a year are produced, 225 of those produced by plants.

== Methane in Earth's atmosphere ==Methane in the Earth's atmosphere is an important greenhouse gas with a global warming potential of 25 over a 100 year period. This means that a 1 tonne methane emission will have 25 times the impact on temperature of a 1 tonne carbon dioxide emission during the following 100 years. Methane has a large effect for a brief period (about 10 years), whereas carbon dioxide has a small effect for a long period (over 100 years). Because of this difference in effect and time period, the global warming potential of methane over a 20 year time period is 72. The methane concentration has increased by about 150% since 1750 and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases.

The average concentration of methane at the Earth's surface in 1998 was 1,745 ppb. Its concentration is higher in the northern hemisphere as most sources (both natural and human) are larger. The concentrations vary seasonally with a minimum in the late summer.

Methane is created near the surface, and it is carried into the stratosphere by rising air in the tropics. Uncontrolled build-up of methane in Earth's atmosphere is naturally checked—although human influence can upset this natural regulation—by methane's reaction with a molecule known as the hydroxyl radical, a hydrogen-oxygen molecule formed when single oxygen atoms react with water vapor.

Early in the Earth's history—about 3.5 billion years ago—there was 1,000 times as much methane in the atmosphere as there is now. The earliest methane was released into the atmosphere by volcanic activity. During this time, Earth's earliest life appeared. These first, ancient bacteria added to the methane concentration by converting hydrogen and carbon dioxide into methane and water. Oxygen did not become a major part of the atmosphere until photosynthetic organisms evolved later in Earth's history. With no oxygen, methane stayed in the atmosphere longer and at higher concentrations than it does today.

Emissions of methane Houweling et al. (1999) give the following values for methane emissions (Tg/a=teragrams per year):



{| style="text-align: right;" border="1" cellspacing="0" class="wikitable"!rowspan=2|Origin!colspan=3| Emission|-!Mass (Tg/annum)!Type (%/a)!Total (%/a)|-!colspan=4|Natural Emissions|-||Wetlands (incl. Rice agriculture)]s| 20| 7| 3|-||Oceans| 10| 4| 2|-||Natural Total| 270| 100| 45|-!colspan=4|[Anthropogenic|-||Energy| 110| 33| 18|-||Landfills]s (Livestock)| 115| 35| 19|-||Waste treatment| 25| 8| 4|-||Biomass burning| 40| 12| 7|-||Anthropogenic Total| 330| 100| 55|-!colspan=4|Sinks|-||Soils] Hydroxyl| -510| -88| -85|-||Stratosphere loss| -40| -7| -7|-||Sink Total| -580| -100| -97|-!colspan=4|Emissions + Sinks|-||Imbalance (trend)| +20| ~2.78 Tg/ppb| +7.19 ppb/a|}Slightly over half of the total emission is due to human activity.

Living plants (e.g. forests) have recently been identified as a potentially important source of methane. A 2006 paper calculated emissions of 62–236 Tg annum-1, and "this newly identified source may have important implications". However the authors stress "our findings are preliminary with regard to the methane emission strength". These findings have been called into question in a 2007 paper which found "there is no evidence for substantial aerobic methane emission by terrestrial plants, maximally 0.3% of the previously published values".

Long term atmospheric measurements of methane by NOAA show that the build up of methane has slowed dramatically over the last decade, after nearly tripling since pre-industrial times . It is thought that this reduction is due to reduced industrial emissions and drought in wetland areas.

Removal processes The major removal mechanism of methane from the atmosphere is by reaction with the hydroxyl radical (·OH), which may be produced when a cosmic ray strikes a molecule of water vapor:



This reaction in the troposphere gives a methane lifetime of 9.6 years. Two more minor sinks are soil sinks (160 year lifetime) and stratospheric loss by reaction with ·OH, ·Cl and ·O1D in the stratosphere (120 year lifetime), giving a net lifetime of 8.4 years. Oxidation of methane is the main source of water vapor in the upper stratosphere (beginning at pressure levels around 10 kPa).

Sudden release from methane clathrates At high pressures, such as are found on the bottom of the ocean, methane forms a solid clathrate with water, known as methane clathrate. An unknown, but possibly very large quantity of methane is trapped in this form in ocean sediments. The sudden release of large volumes of methane from such sediments into the atmosphere has been suggested as a possible cause for rapid global warming events in the Earth's distant past, such as the Paleocene–Eocene Thermal Maximum of 55 million years ago.

One source estimates the size of the methane hydrate deposits of the oceans at ten trillion tons (10 exagrams). Theories suggest that should global warming cause them to heat up sufficiently, all of this methane could again be suddenly released into the atmosphere. Since methane is twenty-three times stronger (for a given weight, averaged over 100 years) than as a greenhouse gas; this would immensely magnify the greenhouse effect, heating Earth to unprecedented levels (see Clathrate gun hypothesis).

Release of methane from bogs Although less dramatic than release from clathrates, but already happening, is an increase in the release of methane from bogs as permafrost melts. Although records of permafrost are limited, recent years (1999 to 2007) have seen record thawing of permafrost in Alaska and Siberia.

Recent measurements in Siberia show that the methane released is five times greater than previously estimated .

Extraterrestrial methane Methane has been detected or is believed to exist in several locations of the solar system. It is believed to have been created by Wiktionary:abiotic processes, with the possible exception of Life on Mars.



Traces of methane gas are present in the thin atmosphere of the Earth's Moon.

Methane has also been detected in interstellar clouds.



See also

References

External links

{| class="toccolours" border="1" style="float: right; clear: right; margin: 0 0 1em 1em; border-collapse: collapse;"! | Methane|-| align="center" colspan="2" bgcolor="#ffffff" | |-! | General|-| Other names || Marsh gas Firedamp || |-| [Simplified molecular input line entry specification || C|-| Molar mass ] || |-| International Chemical Identifier || InChI=1/CH4/h1H4|-! | Properties|-| Density and Phase (matter) || 0.717 kg/m³, gas|-| Soluble in Water (molecule) || 3.5 mg/100 ml (17 °C)|-|-| Material safety data sheet || Methane (data page)#Material Safety Data Sheet |-| Directive 67/548/EEC || Highly flammable (F+)|-| NFPA 704 ] || |-| List of S-phrases || , , , |-| Flash point ] || 537 °C|-| Maximum burning
temperature: || 2148 °C|-| Explosive limits ]|-| Methane (data page)#Structure and properties |||-| Methane (data page)#Thermodynamic properties |||-| Methane (data page)#Spectral data || UV/VIS spectroscopy, Infrared spectroscopy, NMR spectroscopy, Mass spectrometry|-! | Related compounds|-| Related alkanes ]Propane[Chloromethane
Formic acid
Formaldehyde|-| | Except where noted otherwise, data are given for
materials in their [standard statewikipedia:Chemical infobox|-|}Methane is a chemical compound with the molecular formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees. Combustion one molecule of methane in the presence of oxygen releases one molecule of (carbon dioxide) and two molecules of : Methane's relative abundance and clean burning process makes it a very attractive fuel. However, because it is a gas (at normal temperature and pressure - see, STP) and not a liquid or solid, methane is difficult to transport from the areas that produce it to the areas that consume it. Converting methane to derivatives that are more easily transported, such as methanol, is an active area of research. Certain microorganisms can effect this selective oxidation using enzymes called methane monooxygenases.

Methane is a relatively potent greenhouse gas with a high global warming potential (i.e., warming effect compared to carbon dioxide). IPCC Third Assessment Report The Third assessment report of the IPCC stated that when averaged over 100 years each kg of warms the Earth 25 times as much as the same mass of . The Fourth assessment report has updated this number to include indirect effects and states that the relative impact of to averaged over 20 years is 72. IPCC Fourth Assessment Report. The reason for this discrepancy is that methane in the atmosphere is eventually oxidised, producing carbon dioxide and water. As a result, methane in the atmosphere has a half life of seven years (every seven years, the amount of methane halves).

So far, the radiative forcing (global warming) effect of methane has been about one-third of that of CO2 . However, there is a large, but unknown, amount of methane in methane clathrates in the ocean floors. Global warming could release this methane, which could cause a further sharp rise in global temperatures. Such releases of methane may have been a major factor in previous major extinction events. The Earth's crust(geology) also contains huge amounts of methane. Large amounts of methane are produced anaerobically by methanogenesis. Other sources include mud volcanoes which are connected with deep geological faults.

Properties Methane is the major component of a natural gas, about 97% by volume. At room temperature and standard pressure, methane is a colorless, odorless gas; the smell characteristic of natural gas is an artificial safety measure caused by the addition of an odorant, often methanethiol or ethanethiol. Methane has a boiling point of −161°Celsius at a pressure of one Atmosphere (unit). As a gas it is flammable only over a narrow range of concentrations (5–15%) in air. Liquid methane does not burn unless subjected to high pressure (normally 4–5 atmospheres.)

Potential health effects Methane is not toxic; however, it is highly flammable and may form explosive mixtures with air. Methane is violently reactive with oxidizers, halogens, and some halogen-containing compounds. Methane is also an asphyxiant gas and may displace oxygen in an enclosed space. Asphyxia may result if the oxygen concentration is reduced to below 19.5% by displacement. The concentrations at which flammable or explosive mixtures form are much lower than the concentration at which asphyxiation risk is significant. When structures are built on or near landfills, methane off-gas can penetrate the buildings' interiors and expose occupants to significant levels of methane. Some buildings have specially engineered recovery systems below their basements to actively capture such fugitive off-gas and vent it away from the building. An example of this type of system is in the Dakin Building, Brisbane, California.

Reactions of methane Main reactions with methane are: combustion, steam reforming to syngas, and halogenation. In general, methane reactions are hard to control. Partial oxidation to methanol, for example, is difficult to achieve; the reaction typically progresses all the way to carbon dioxide and water.

Combustion In the combustion of methane, several steps are involved:

Methane is believed to form a formaldehyde (HCHO or ). The formaldehyde gives a formyl Radical (chemistry) (HCO), which then forms carbon monoxide (CO). The process is called oxidative pyrolysis:



Following oxidative pyrolysis, the oxidizes, forming , replenishing the active species, and releasing heat. This occurs very quickly, usually in significantly less than a millisecond.



Finally, the CO oxidizes, forming and releasing more heat. This process is generally slower than the other chemical steps, and typically requires a few to several milliseconds to occur.



Hydrogen activation The strength of the carbon-hydrogen covalent bond in methane is among the strongest in all hydrocarbons, and thus its use as a chemical feedstock is limited. Despite the high activation barrier for breaking the C–H bond, is still the principal starting material for manufacture of hydrogen in steam reforming. The search for catalysts which can facilitate C–H bond activation in methane and other low alkanes is an area of research with considerable industrial significance.

Reactions with halogens Methane reacts with all halogens given appropriate conditions, as follows:



where X is a halogen: fluorine (F), chlorine (Cl), bromine (Br), or iodine (I). This mechanism for this process is called free radical halogenation.

Uses Fuel For more on the use of methane as a fuel, see: natural gas

Methane is important for electrical generation by burning it as a fuel in a gas turbine or steam boiler. Compared to other hydrocarbon fuels, burning methane produces less carbon dioxide for each unit of heat released. Also, methane's heat of combustion is about 802 kJ/mol, which is lower than any other hydrocarbon, but if a ratio is made with the molecular mass (16.0 g/mol) divided by the heat of combustion (802 kJ/mol) it is found that methane, being the simplest hydrocarbon, actually produces the most heat per unit mass than other complex hydrocarbons. In many cities, methane is piped into homes for domestic heating and cooking purposes. In this context it is usually known as natural gas, and is considered to have an energy content of 1,000 BTU/standard cubic foot.

Methane in the form of compressed natural gas is used as a fuel for vehicles, and is claimed to be more environmentally friendly than alternatives such as gasoline/petrol and diesel. Research is being conducted by NASA on methane's potential as a rocket fuel. One advantage of methane is that it is abundant in many parts of the solar system and it could potentially be harvested in situ, providing fuel for a return journey.

Industrial uses Methane is used in industrial chemical processes and may be transported as a refrigerated liquid (liquefied natural gas, or LNG). While leaks from a refrigerated liquid container are initially heavier than air due to the increased density of the cold gas, the gas at ambient temperature is lighter than air. Pipeline transports distribute large amounts of natural gas, of which methane is the principal component.

In the chemical industry, methane is the feedstock of choice for the production of hydrogen, methanol, acetic acid, and acetic anhydride. When used to produce any of these chemicals, methane is first converted to synthesis gas, a mixture of carbon monoxide and hydrogen, by steam reforming. In this process, methane and steam react on a nickel catalyst at high temperatures (700–1100 °C).



The ratio of carbon monoxide to hydrogen in synthesis gas can then be adjusted via the water gas shift reaction to the appropriate value for the intended purpose.



Less significant methane-derived chemicals include acetylene, prepared by passing methane through an electric arc, and the chloromethanes (chloromethane, dichloromethane, chloroform, and carbon tetrachloride), produced by reacting methane with chlorine gas. However, the use of these chemicals is declining, acetylene as it is replaced by less costly substitutes, and the chloromethanes due to health and environmental concerns.

Sources of methane Natural gas fields The major source of methane is extraction from geological deposits known as natural gas fields. It is associated with other hydrocarbon fuels and sometimes accompanied by helium and nitrogen. The gas at shallow levels (low pressure) is formed by anaerobic organism decay of organic matter and reworked methane from deep under the Earth's surface. In general, sediments buried deeper and at higher temperatures than those which give Petroleum generate natural gas. Methane is also produced in considerable quantities from the decaying organic wastes of solid waste landfills.

Alternative sources Apart from gas fields an alternative method of obtaining methane is via biogas generated by the fermentation (biochemistry) of organic matter including manure, wastewater sludge, municipal solid waste (including landfills), or any other biodegradable feedstock, under anaerobic conditions. Methane hydrates/clathrates (icelike combinations of methane and water on the sea floor, found in vast quantities) are a potential future source of methane. Some say that significant quantities are also produced by cattleburp. This however, remains to be proven and most scientists refute this as a fact. http://www.mycattle.com/health/dsp_health_article.cfm?storyid=10045http://news.bbc.co.uk/1/hi/scotland/4582174.stm The livestock sector in general (primarily cattle, chickens, and pigs) produces 37% of all human-induced methane".{{cite web |url=http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.htm|title=Livestock’s Long Shadow–Environmental Issues and Options|accessdate=2007-01-04--> However animals "that put their energies into making gas are less efficient at producing milk and meat". Early research has found a number of medical treatments and dietary adjustments that help limit the production of methane in ruminants.http://news.nationalgeographic.com/news/2005/08/0816_050816_cowpollution_2.html http://news.nationalgeographic.com/news/2002/05/0509_020509_belch.html

Industrially, methane can be created from common atmospheric gases and hydrogen (produced, perhaps, by electrolysis) through chemical reactions such as the Sabatier process, Fischer-Tropsch process. Coal bed methane extraction is a method for extracting methane from a coal deposit.

A recent scientific experiment has also yielded results pointing to the fact that all plants produce methane, and as the climate warms they produce more Methane emissions from terrestrial plants under aerobic conditions Nature, January 12, 2006. In fact 600 million metric tons of methane a year are produced, 225 of those produced by plants.

== Methane in Earth's atmosphere ==Methane in the Earth's atmosphere is an important greenhouse gas with a global warming potential of 25 over a 100 year period. This means that a 1 tonne methane emission will have 25 times the impact on temperature of a 1 tonne carbon dioxide emission during the following 100 years. Methane has a large effect for a brief period (about 10 years), whereas carbon dioxide has a small effect for a long period (over 100 years). Because of this difference in effect and time period, the global warming potential of methane over a 20 year time period is 72. The methane concentration has increased by about 150% since 1750 and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases.

The average concentration of methane at the Earth's surface in 1998 was 1,745 ppb. Its concentration is higher in the northern hemisphere as most sources (both natural and human) are larger. The concentrations vary seasonally with a minimum in the late summer.

Methane is created near the surface, and it is carried into the stratosphere by rising air in the tropics. Uncontrolled build-up of methane in Earth's atmosphere is naturally checked—although human influence can upset this natural regulation—by methane's reaction with a molecule known as the hydroxyl radical, a hydrogen-oxygen molecule formed when single oxygen atoms react with water vapor.

Early in the Earth's history—about 3.5 billion years ago—there was 1,000 times as much methane in the atmosphere as there is now. The earliest methane was released into the atmosphere by volcanic activity. During this time, Earth's earliest life appeared. These first, ancient bacteria added to the methane concentration by converting hydrogen and carbon dioxide into methane and water. Oxygen did not become a major part of the atmosphere until photosynthetic organisms evolved later in Earth's history. With no oxygen, methane stayed in the atmosphere longer and at higher concentrations than it does today.

Emissions of methane Houweling et al. (1999) give the following values for methane emissions (Tg/a=teragrams per year):



{| style="text-align: right;" border="1" cellspacing="0" class="wikitable"!rowspan=2|Origin!colspan=3| Emission|-!Mass (Tg/annum)!Type (%/a)!Total (%/a)|-!colspan=4|Natural Emissions|-||Wetlands (incl. Rice agriculture)]s| 20| 7| 3|-||Oceans| 10| 4| 2|-||Natural Total| 270| 100| 45|-!colspan=4|[Anthropogenic|-||Energy| 110| 33| 18|-||Landfills]s (Livestock)| 115| 35| 19|-||Waste treatment| 25| 8| 4|-||Biomass burning| 40| 12| 7|-||Anthropogenic Total| 330| 100| 55|-!colspan=4|Sinks|-||Soils] Hydroxyl| -510| -88| -85|-||Stratosphere loss| -40| -7| -7|-||Sink Total| -580| -100| -97|-!colspan=4|Emissions + Sinks|-||Imbalance (trend)| +20| ~2.78 Tg/ppb| +7.19 ppb/a|}Slightly over half of the total emission is due to human activity.

Living plants (e.g. forests) have recently been identified as a potentially important source of methane. A 2006 paper calculated emissions of 62–236 Tg annum-1, and "this newly identified source may have important implications". However the authors stress "our findings are preliminary with regard to the methane emission strength". These findings have been called into question in a 2007 paper which found "there is no evidence for substantial aerobic methane emission by terrestrial plants, maximally 0.3% of the previously published values".

Long term atmospheric measurements of methane by NOAA show that the build up of methane has slowed dramatically over the last decade, after nearly tripling since pre-industrial times . It is thought that this reduction is due to reduced industrial emissions and drought in wetland areas.

Removal processes The major removal mechanism of methane from the atmosphere is by reaction with the hydroxyl radical (·OH), which may be produced when a cosmic ray strikes a molecule of water vapor:



This reaction in the troposphere gives a methane lifetime of 9.6 years. Two more minor sinks are soil sinks (160 year lifetime) and stratospheric loss by reaction with ·OH, ·Cl and ·O1D in the stratosphere (120 year lifetime), giving a net lifetime of 8.4 years. Oxidation of methane is the main source of water vapor in the upper stratosphere (beginning at pressure levels around 10 kPa).

Sudden release from methane clathrates At high pressures, such as are found on the bottom of the ocean, methane forms a solid clathrate with water, known as methane clathrate. An unknown, but possibly very large quantity of methane is trapped in this form in ocean sediments. The sudden release of large volumes of methane from such sediments into the atmosphere has been suggested as a possible cause for rapid global warming events in the Earth's distant past, such as the Paleocene–Eocene Thermal Maximum of 55 million years ago.

One source estimates the size of the methane hydrate deposits of the oceans at ten trillion tons (10 exagrams). Theories suggest that should global warming cause them to heat up sufficiently, all of this methane could again be suddenly released into the atmosphere. Since methane is twenty-three times stronger (for a given weight, averaged over 100 years) than as a greenhouse gas; this would immensely magnify the greenhouse effect, heating Earth to unprecedented levels (see Clathrate gun hypothesis).

Release of methane from bogs Although less dramatic than release from clathrates, but already happening, is an increase in the release of methane from bogs as permafrost melts. Although records of permafrost are limited, recent years (1999 to 2007) have seen record thawing of permafrost in Alaska and Siberia.

Recent measurements in Siberia show that the methane released is five times greater than previously estimated .

Extraterrestrial methane Methane has been detected or is believed to exist in several locations of the solar system. It is believed to have been created by Wiktionary:abiotic processes, with the possible exception of Life on Mars.



Traces of methane gas are present in the thin atmosphere of the Earth's Moon.

Methane has also been detected in interstellar clouds.



See also

References

External links



BBC - Weather Centre - Climate Change - Methane
BBC Weather's climate change site. All the issues and key topics including global warming, greenhouse effect, ozone, kyoto, politics and the environment.

BBC - Weather Centre - Features - Climate Change, Environment and ...
Methane (CH4) is also known as Natural Gas. As a trace gas in the atmosphere, methane has a more warming effect than carbon dioxide - 21 times more on a molecule by molecule basis ...

Methane - Wikipedia, the free encyclopedia
Methane is a chemical compound with the molecular formula CH 4. It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees ...

BBC NEWS | Science/Nature | Methane on Mars could signal life
Scientists speculate that methane detected in the Martian atmosphere could be a sign of microbial life.

BBC NEWS | Science/Nature | Hints of methane's renewed rise
Levels of the greenhouse gas methane appear to be rising again after years of stability, data suggests.

Methane
Simple explanation of methane in the framework of the history of the Universe ... Physical Environment > Methane This site tells the story of the history of the universe.

US EPA - Methane
EPA's Methane Energy Programs promote profitable opportunities for reducing emissions of methane, an important greenhouse gas.

Chemical of the Week -- Methane
METHANE. Methane is a colorless, odorless gas with a wide distribution in nature. It is the principal component of natural gas, a mixture containing about 75% CH 4, 15% ethane (C 2 ...

Methane Gas Hydrates - HSE Horizon Scanning Intelligence Group short ...
Methane Gas Hydrates - HSE Horizon Scanning Intelligence Group short report

Safety (MSDS) data for methane
Safety (MSDS) data for methane ... Glossary of terms on this data sheet. The information on this web page is provided to help you to work safely, but it is intended to be an ...

 

Methane



 
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