View source for Chemistry:Methane emissions

{{short description|Sources of methane gas in Earth's atmosphere}}
<noinclude>{{Pie chart
    |caption= Sources of methane emissions due to human activity (year 2020 estimates) <ref name=Initiative />
    | value1 =33
    | label1 =Fossil Fuel Use
    | color1 =blue
    | value2 =30
    | label2 =Animal Agriculture
    | color2 =yellow
    | value3 =18
    | label3 =Plant Agriculture
    | color3 =green
    | value4 =15
    | label4 =Waste
    | color4 =brown
    | value5 =4
    | label5 =All Other
    | color5 =purple
}}</noinclude>
Increasing '''methane emissions''' are a major contributor to the rising concentration of [[Chemistry:Greenhouse gas|greenhouse gas]]es in Earth's atmosphere, and are responsible for up to one-third of near-term global heating.<ref name=Initiative>{{cite web |url=https://www.globalmethane.org/documents/gmi-mitigation-factsheet.pdf |title=Global Methane Emissions and Mitigation Opportunities |publisher=Global Methane Initiative |year=2020}}</ref><ref name=IPCCforce>{{Cite report |url=https://www.ipcc.ch/report/ar5/wg1/summary-for-policymakers/figspm-05/ |title=IPCC Fifth Assessment Report - Radiative Forcings (AR5 Figure SPM.5) |publisher=[[Organization:Intergovernmental Panel on Climate Change|Intergovernmental Panel on Climate Change]] |year=2013}}</ref> During 2019, about 60% (360 million tons) of [[Chemistry:Methane|methane]] released globally was from human activities, while natural sources contributed about 40% (230 million tons).<ref name=ieasources>{{cite web |url=https://www.iea.org/data-and-statistics/charts/sources-of-methane-emissions-2 |title=Sources of methane emissions |publisher=[[Organization:International Energy Agency|International Energy Agency]] |access-date=2020-08-20}}</ref><ref name=carbpro>{{Cite web|url=https://www.globalcarbonproject.org/methanebudget/index.htm|title=Global Carbon Project (GCP)|website=www.globalcarbonproject.org|access-date=2019-07-25}}</ref>  Reducing methane emissions by capturing and utilizing the gas can produce simultaneous environmental and economic benefits.<ref name=Initiative /><ref>{{cite report |url=https://www.iea.org/reports/methane-tracker-2020#a-compelling-case-for-action |title=Methane - A compelling case for action |publisher=[[Organization:International Energy Agency|International Energy Agency]] |date=2020-08-20}}</ref>

Since the Industrial Revolution, concentrations of [[Earth:Atmospheric methane|methane in the atmosphere]] have more than doubled, and about 20 percent of the warming the planet has experienced can be attributed to the gas.<ref>Borunda, A. (2021, May 03). Methane facts and information. Retrieved April 6, 2022, from [https://web.archive.org/web/20210218020654/https://www.nationalgeographic.com/environment/article/methane]</ref> About one-third (33%) of anthropogenic emissions are from gas release during the extraction and delivery of fossil fuels;  mostly due to [[Chemistry:Gas venting|gas venting]] and [[Physics:Gas leak|gas leak]]s from both active fossil fuel infrastructure and orphan wells.<ref>{{Cite web|last=Leber|first=Rebecca|date=2021-08-12|title=It's time to freak out about methane emissions|url=https://www.vox.com/22613532/climate-change-methane-emissions|access-date=2022-01-05|website=Vox|language=en}}</ref>  Russia is the world's top methane emitter from oil and gas.<ref>{{Cite news|url= https://www.euractiv.com/section/climate-environment/opinion/putting-a-lid-on-russias-planet-heating-methane-emissions/ |title= Putting a lid on Russia's planet-heating methane emissions |last=Trakimavicius|first=Lukas|work=EurActiv|access-date=2023-07-26|language=en-US}}</ref><ref>{{cite news |author1=Timothy Puko |title=Who Are the World's Biggest Climate Polluters? Satellites Sweep for Culprits |url=https://www.wsj.com/articles/who-are-the-worlds-biggest-climate-polluters-satellites-sweep-for-culprits-11634635980?mod=hp_lead_pos7 |access-date=19 October 2021 |work={{wipe|The Wall Street Journal}} |date=19 October 2021 |quote=Russia is the world’s top source of methane emissions from the oil-and-gas industry}}</ref>  

Animal agriculture is a similarly large source (30%);  primarily because of [[Biology:Enteric fermentation|enteric fermentation]] by [[Biology:Ruminant|ruminant livestock]] such as cattle and sheep. According to the Global Methane Assessment published in 2021, methane emissions from livestock (including cattle) are the largest sources of agricultural emissions worldwide<ref>Jones, E. (2021, November 12). Yes, cattle are the top source of methane emissions in the US. Retrieved April 6, 2022, from https://www.verifythis.com/article/news/verify/environment-verify/cattle-cows-the-top-source-of-methane-emissions-in-united-states/536-8d5bf326-6955-4a9c-8ea5-761d73ba464c</ref> A single cow can make up to 99 kg of methane gas per year.<ref>Quinton, A. (2022, January 06). Cows and climate change. Retrieved April 6, 2022, from https://www.ucdavis.edu/food/news/making-cattle-more-sustainable</ref> Ruminant livestock can produce 250 to 500 L of methane per day.<ref>{{cite web |last1=Johnson |first1=K A |date=1995-08-01 |title=Methane emissions from cattle |url=https://academic.oup.com/jas/article-abstract/73/8/2483/4632901 |accessdate=2023-04-27 |website=academic.oup.com}}</ref>

Human consumer waste flows, especially those passing through landfills and [[Earth:Wastewater treatment|wastewater treatment]], have grown to become a third major category (18%). Plant agriculture, including both food and [[Biology:Biomass|biomass]] production, constitutes a fourth group (15%), with rice production being the largest single contributor.<ref name="Initiative" /><ref name="nationalgeo">{{Cite web|url=https://www.nationalgeographic.com/environment/global-warming/methane/|archive-url=https://web.archive.org/web/20190417010815/https://www.nationalgeographic.com/environment/global-warming/methane/|url-status=dead|archive-date=April 17, 2019|title=Methane, explained|date=2019-01-23|website=National Geographic|publisher=nationalgeographic.com|access-date=2019-07-25}}</ref>

The world's [[Earth:Wetland|wetland]]s contribute about three-quarters (75%) of the enduring natural sources of methane.<ref name=ieasources /><ref name=carbpro /> Seepages from near-surface [[Chemistry:Hydrocarbon|hydrocarbon]] and [[Physics:Clathrate hydrate|clathrate hydrate]] deposits, [[Physics:Volcanic gas|volcanic releases]], [[Biology:Wildfire|wildfire]]s, and [[Biology:Termite|termite]] emissions account for much of the remainder.<ref name="nationalgeo" />   Contributions from the surviving wild populations of ruminant mammals are vastly overwhelmed by those of cattle, humans, and other livestock animals.<ref>{{Cite news |url=https://spectrum.ieee.org/energy/environment/planet-of-the-cows |author=Vaclav Smil |title=Planet of the Cows |newspaper=IEEE Spectrum |date=2017-03-29 | access-date=2020-09-08}}</ref>

''The Economist'' recommended setting methane emissions targets as a reduction in methane emissions would allow for more time to tackle the more challenging carbon emissions".<ref name="economist_2021">{{Cite news |date=2021-03-31 |title=Governments should set targets to reduce methane emissions |newspaper=The Economist |url=https://www.economist.com/leaders/2021/03/31/governments-should-set-targets-to-reduce-methane-emissions |access-date=October 10, 2021 |issn=0013-0613}}</ref><ref name="Terazono_2021">{{Cite news |last1=Terazono |first1=Emiko |last2=Hodgson |first2=Camilla |date=2021-10-10 |title=How methane-producing cows leapt to the frontline of climate change |work=Financial Times |url=https://www.ft.com/content/73e5f1fc-76ac-48b0-871a-7fa4e8bda69b |access-date=October 10, 2021}}</ref>

==Atmospheric concentration and warming influence==
{{Further|Earth:Atmospheric methane}}
[[File:Globally averaged atmospheric CH4 and its annual growth rate GATM.png|thumb|250px|Globally averaged atmospheric concentration and its annual growth rate.<ref name="methanebudget"/> In April 2022, NOAA reported an annual increase in global atmospheric methane of 17 parts per billion (ppb) in 2021—averaging 1,895.7 ppb in that year—the largest annual increase recorded since systematic measurements began in 1983; the increase during 2020 was 15.3 ppb, itself a record increase.<ref name=NOAA_20220407>{{cite web |title=Increase in atmospheric methane set another record during 2021 / Carbon dioxide levels also record a big jump |url=https://www.noaa.gov/news-release/increase-in-atmospheric-methane-set-another-record-during-2021 |website=NOAA.gov |date= 7 April 2022 |archive-url=https://web.archive.org/web/20220407164038/https://www.noaa.gov/news-release/increase-in-atmospheric-methane-set-another-record-during-2021 |archive-date=7 April 2022 |url-status=live }}</ref>]]
The [[Earth:Atmospheric methane|atmospheric methane]] (CH<sub>4</sub>) concentration is increasing and exceeded 1860 parts per billion in 2019, equal to two-and-a-half times the pre-industrial level.<ref>[https://esrl.noaa.gov/gmd/ccgg/trends_ch4/ Earth System Research Laboratory Global Monitoring Division], NOAA, May 5, 2019</ref> The methane itself causes ''direct [[Astronomy:Radiative forcing|radiative forcing]]'' that is second only to that of [[Chemistry:Carbon dioxide|carbon dioxide]] (CO<sub>2</sub>).<ref name="butmon">{{Cite web |url=https://www.esrl.noaa.gov/gmd/aggi/aggi.html |title=The NOAA Annual Greenhouse Gas Index (AGGI) |publisher=NOAA Global Monitoring Laboratory/Earth System Research Laboratories |author=Butler J. and Montzka S. |year=2020 }}</ref>  Due to interactions with oxygen compounds stimulated by sunlight, CH<sub>4</sub> can also increase the atmospheric presence of shorter-lived [[Chemistry:Ozone|ozone]] and water vapour, themselves potent warming gases: atmospheric researchers call this amplification of methane's near-term warming influence ''indirect radiative forcing''.<ref>{{Cite journal |journal=Environ. Res. Lett. |volume=4 |number=4 |year=2009 |title=The indirect global warming potential and global temperature change potential due to methane oxidation |vauthors=Boucher O, Friedlingstein P, Collins B, Shine KP |page=044007 |doi=10.1088/1748-9326/4/4/044007|bibcode=2009ERL.....4d4007B |doi-access=free }}</ref> When such interactions occur, longer-lived and less-potent CO<sub>2</sub> is also produced.  Including both the direct and indirect forcings, the increase in atmospheric methane is responsible for about one-third of near-term global heating.<ref name=Initiative /><ref name=IPCCforce />

Though methane causes far more heat to be trapped than the same mass of carbon dioxide, less than half of the emitted CH<sub>4</sub> remains in the atmosphere after a decade. On average, carbon dioxide warms for much longer, assuming no change in rates of carbon sequestration.<ref>{{cite web|title=Understanding Global Warming Potentials|date=12 January 2016|url=https://www.epa.gov/ghgemissions/understanding-global-warming-potentials|access-date=2019-09-09}}</ref><ref name="IPCC_AR5" /> The [[Physics:Global warming potential|global warming potential]] (GWP) is a way of comparing the warming due to other gases to that from carbon dioxide, over a given time period. Methane's GWP<sub>20</sub> of 85 means that a ton of CH<sub>4</sub> emitted into the atmosphere creates approximately 85 times the atmospheric warming as a ton of CO<sub>2</sub> over a period of 20 years.<ref name="IPCC_AR5">Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang (2013) [http://www.climatechange2013.org/images/report/WG1AR5_Chapter08_FINAL.pdf "Anthropogenic and Natural Radiative Forcing"]. Table 8.7 on page 714.  In: ''Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change''. Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. [http://www.climatechange2013.org/images/report/WG1AR5_Chapter08_FINAL.pdf Anthropogenic and Natural Radiative Forcing]</ref> On a 100-year timescale, methane's GWP<sub>100</sub> is in the range of 28–34.

Methane emissions are important as reducing them can buy time to tackle carbon emissions.<ref>{{Cite news|last1=Terazono|first1=Emiko|last2=Hodgson|first2=Camilla|date=2021-10-10|title=How methane-producing cows leapt to the frontline of climate change|work=Financial Times|url=https://www.ft.com/content/73e5f1fc-76ac-48b0-871a-7fa4e8bda69b|access-date=2021-10-10}}</ref><ref>{{Cite news|date=2021-03-31|title=Governments should set targets to reduce methane emissions|newspaper=The Economist|url=https://www.economist.com/leaders/2021/03/31/governments-should-set-targets-to-reduce-methane-emissions|access-date=2021-10-10|issn=0013-0613}}</ref>

==Overview of emission sources==
[[File:The Global Methane Budget 2008–2017.png|thumb|upright=1.4|The main sources of methane for the decade 2008–2017, estimated by the [[Organization:Global Carbon Project|Global Carbon Project]]<ref name="methanebudget"/>]]

[[File:Methane global emissions from the five broad categories.png|thumb|230px|"Methane global emissions from the five broad categories for the 2008–2017 decade for top-down inversion models and for bottom-up models and inventories (right dark coloured box plots).<ref name="methanebudget"/>{{Clarify|reason=not all the right box plots are dark colored - maybe the diagram should be removed?|date=April 2021}}]]

Biogenic methane is actively produced by microorganisms in a process called [[Engineering:Methanogenesis|methanogenesis]].  Under certain conditions, the process mix responsible for a sample of methane may be deduced from the ratio of the [[Physics:Isotopes of carbon|isotopes of carbon]], and through analysis methods similar to carbon dating.<ref>{{Cite journal |url=https://doi.org/10.1038/nature19797 |title=Upward revision of global fossil fuel methane emissions based on isotope database |author=Schwietzke, S., Sherwood, O., Bruhwiler, L. |display-authors=0 |journal=Nature |publisher=Springer Nature |issue=7623 |pages=88–91 |year=2016 |volume=538 |doi=10.1038/nature19797|pmid=27708291 |bibcode=2016Natur.538...88S |s2cid=4451521 }}</ref><ref>{{Cite journal |url=https://doi.org/10.1038/s41586-020-1991-8 |title=Preindustrial <sup>14</sup>CH<sub>4</sub> indicates greater anthropogenic fossil CH<sub>4</sub> emissions |author=Hmiel, B., Petrenko, V.V., Dyonisius, M.N. |display-authors=0 |journal=Nature |publisher=Springer Nature |issue=7795 |pages=409–412 |year=2020 |volume=578 |doi=10.1038/s41586-020-1991-8|pmid=32076219 |bibcode=2020Natur.578..409H |s2cid=211194542 }}</ref>

===Anthropogenic===
[[File:Map of methane emissions from four source categories.png|thumb|300px|Map of methane emissions from four source categories<ref name="methanebudget">{{cite journal |title=The Global Methane Budget 2000–2017 |journal=Earth System Science Data |date=15 July 2020 |volume=12 |issue=3 |pages=1561–1623 |doi=10.5194/essd-12-1561-2020 |url=https://essd.copernicus.org/articles/12/1561/2020/ |access-date=28 August 2020 |language=en |issn=1866-3508|last1=Saunois |first1=Marielle |last2=Stavert |first2=Ann R. |last3=Poulter |first3=Ben |last4=Bousquet |first4=Philippe |last5=Canadell |first5=Josep G. |last6=Jackson |first6=Robert B. |last7=Raymond |first7=Peter A. |last8=Dlugokencky |first8=Edward J. |last9=Houweling |first9=Sander |last10=Patra |first10=Prabir K. |last11=Ciais |first11=Philippe |last12=Arora |first12=Vivek K. |last13=Bastviken |first13=David |last14=Bergamaschi |first14=Peter |last15=Blake |first15=Donald R. |last16=Brailsford |first16=Gordon |last17=Bruhwiler |first17=Lori |last18=Carlson |first18=Kimberly M. |last19=Carrol |first19=Mark |last20=Castaldi |first20=Simona |last21=Chandra |first21=Naveen |last22=Crevoisier |first22=Cyril |last23=Crill |first23=Patrick M. |last24=Covey |first24=Kristofer |last25=Curry |first25=Charles L. |last26=Etiope |first26=Giuseppe |last27=Frankenberg |first27=Christian |last28=Gedney |first28=Nicola |last29=Hegglin |first29=Michaela I. |last30=Höglund-Isaksson |first30=Lena |bibcode=2020ESSD...12.1561S |display-authors=29 |doi-access=free }}</ref>]]

{{As of|2020}}, emission volumes from some sources remain more uncertain than others; due in part to localized emission spikes not captured by the limited global measurement capability.  The time required for a methane emission to become well-mixed throughout earth's [[Earth:Troposphere|troposphere]] is about 1–2 years.<ref>{{Cite web |url=https://earthobservatory.nasa.gov/features/MethaneMatters |title=Methane Matters |publisher=NASA Earth Observatory |author=Adam Voiland and Joshua Stevens |date=8 March 2016 |access-date=2020-09-15}}</ref>

[[Astronomy:Earth observation satellite#Environmental monitoring|Satellite data]] indicate over 80% of the growth of methane emissions during 2010–2019 are tropical terrestrial emissions.<ref>{{cite news |title={{chem|CH|4}} responsible for more than 80% of recent atmospheric methane growth |url=https://www.upi.com/Science_News/2022/03/16/CH4-responsible-80-recent-atmospheric-methane-growth/1481647467272/ |access-date=27 April 2022 |work=UPI |language=en}}</ref><ref>{{cite journal |last1=Feng |first1=Liang |last2=Palmer |first2=Paul I. |last3=Zhu |first3=Sihong |last4=Parker |first4=Robert J. |last5=Liu |first5=Yi |title=Tropical methane emissions explain large fraction of recent changes in global atmospheric methane growth rate |journal=Nature Communications |date=16 March 2022 |volume=13 |issue=1 |pages=1378 |doi=10.1038/s41467-022-28989-z|pmid=35297408  |pmc=8927109 |bibcode=2022NatCo..13.1378F |language=en |issn=2041-1723}}</ref>

There is accumulating research and data showing that oil and gas industry methane emissions – or from fossil fuel extraction, distribution and use – are much larger than thought.<ref>{{cite news |title=Gas flares aren't as efficient at burning off methane as assumed |url=https://www.sciencenews.org/article/gas-flare-leak-methane-burning-climate |access-date=21 October 2022 |work=Science News |date=29 September 2022}}</ref><ref>{{cite journal |last1=Plant |first1=Genevieve |last2=Kort |first2=Eric A. |last3=Brandt |first3=Adam R. |last4=Chen |first4=Yuanlei |last5=Fordice |first5=Graham |last6=Gorchov Negron |first6=Alan M. |last7=Schwietzke |first7=Stefan |last8=Smith |first8=Mackenzie |last9=Zavala-Araiza |first9=Daniel |title=Inefficient and unlit natural gas flares both emit large quantities of methane |journal=Science |date=30 September 2022 |volume=377 |issue=6614 |pages=1566–1571 |doi=10.1126/science.abq0385 |pmid=36173866 |bibcode=2022Sci...377.1566P |s2cid=252621958 |url=https://www.science.org/doi/10.1126/science.abq0385 |language=en |issn=0036-8075|url-access=subscription}}</ref><ref>{{cite journal |last1=Hmiel |first1=Benjamin |last2=Petrenko |first2=V. V. |last3=Dyonisius |first3=M. N. |last4=Buizert |first4=C. |last5=Smith |first5=A. M. |last6=Place |first6=P. F. |last7=Harth |first7=C. |last8=Beaudette |first8=R. |last9=Hua |first9=Q. |last10=Yang |first10=B. |last11=Vimont |first11=I. |last12=Michel |first12=S. E. |last13=Severinghaus |first13=J. P. |last14=Etheridge |first14=D. |last15=Bromley |first15=T. |last16=Schmitt |first16=J. |last17=Faïn |first17=X. |last18=Weiss |first18=R. F. |last19=Dlugokencky |first19=E. |title=Preindustrial 14CH4 indicates greater anthropogenic fossil CH4 emissions |journal=Nature |date=20 February 2020 |volume=578 |issue=7795 |pages=409–412 |doi=10.1038/s41586-020-1991-8|pmid=32076219 |bibcode=2020Natur.578..409H |s2cid=211194542 |url=https://escholarship.org/uc/item/77682176 }}</ref><ref>{{cite journal |last1=Gorchov Negron |first1=Alan M. |last2=Kort |first2=Eric A. |last3=Conley |first3=Stephen A. |last4=Smith |first4=Mackenzie L. |title=Airborne Assessment of Methane Emissions from Offshore Platforms in the U.S. Gulf of Mexico |journal=Environmental Science & Technology |date=21 April 2020 |volume=54 |issue=8 |pages=5112–5120 |doi=10.1021/acs.est.0c00179 |pmid=32281379 |bibcode=2020EnST...54.5112G |issn=0013-936X|doi-access=free }}</ref><ref>{{cite journal |last1=Zhang |first1=Yuzhong |last2=Gautam |first2=Ritesh |last3=Pandey |first3=Sudhanshu |last4=Omara |first4=Mark |last5=Maasakkers |first5=Joannes D. |last6=Sadavarte |first6=Pankaj |last7=Lyon |first7=David |last8=Nesser |first8=Hannah |last9=Sulprizio |first9=Melissa P. |last10=Varon |first10=Daniel J. |last11=Zhang |first11=Ruixiong |last12=Houweling |first12=Sander |last13=Zavala-Araiza |first13=Daniel |last14=Alvarez |first14=Ramon A. |last15=Lorente |first15=Alba |last16=Hamburg |first16=Steven P. |last17=Aben |first17=Ilse |last18=Jacob |first18=Daniel J. |title=Quantifying methane emissions from the largest oil-producing basin in the United States from space |journal=Science Advances |date=1 April 2020 |volume=6 |issue=17 |pages=eaaz5120 |doi=10.1126/sciadv.aaz5120 |pmid=32494644 |pmc=7176423 |bibcode=2020SciA....6.5120Z |doi-access=free }}</ref>

{| class=wikitable style="text-align: center;"
|-
! Category !! Major Sources !! [[Organization:International Energy Agency|IEA]] Annual Emission<ref name=ieasources /><br>(Million Tons)
|-
| rowspan="3" | Fossil fuels
| [[Chemistry:Gas venting#Gas field and gas pipeline practices|Gas distribution]]
| 45
|-
| [[Chemistry:Gas venting#Oil field practice relating to unwanted gas|Oil wells]]
| 39*
|-
| [[Chemistry:Gas venting#Coal mining and coalbed methane activity|Coal mines]]
| 39
|-
| Biofuels
| [[Physics:Anaerobic digestion|Anaerobic digestion]]
| 11
|-
| rowspan="3" | Industrial agriculture
| [[Biology:Enteric fermentation|Enteric fermentation]]
| rowspan="3" | 145
|-
| Rice paddies <!-- column 1+3 occupied -->
|-
| [[Earth:Manure management|Manure management]] <!-- column 1+3 occupied -->
|-
| [[Biology:Biomass|Biomass]]
| [[Biology:Biomass#Environmental impact|Biomass burning]]
| 16
|-
| rowspan="2" | Consumer waste
| Solid waste<br>[[Chemistry:Landfill gas|Landfill gas]]
| rowspan="2" | 68
|-
| Wastewater <!-- column 1+3 occupied -->
|-
! colspan="2" style="text-align: right; | Total anthropogenic
! 363
|-
! colspan="3" style="text-align: left; font-size: 0.85em; font-weight: normal;" | * An additional 100 million tons (140 billion cubic meters) of gas is [[Chemistry:Routine flaring|flared]] each year from oil wells.<ref>{{Cite web |url=https://www.worldbank.org/en/programs/zero-routine-flaring-by-2030 |title=Zero Routine Flaring by 2030 |publisher=World Bank |access-date=2020-09-18}}</ref><br><em>Additional References:</em> <ref name=Initiative /><ref name=faq>{{cite web|url=https://www.globalmethane.org/about/methane.aspx|title=About Methane|publisher=Global Methane Initiative|access-date=2020-09-15}}</ref><ref name=epame>{{cite web|url=https://www.epa.gov/ghgemissions/overview-greenhouse-gases|title=Overview of Greenhouse Gases|first=OA|last=US EPA|date=23 December 2015|website=US EPA}}</ref><ref>{{cite web|url=http://www.fao.org/news/story/en/item/216137/icode/|title=Agriculture's greenhouse gas emissions on the rise|publisher=FAO|access-date=2017-04-19}}</ref><ref>{{cite news|journal=The Guardian|year=2016|url=https://www.theguardian.com/environment/2016/oct/05/fossil-fuel-industrys-methane-emissions-far-higher-than-thought| title=Fossil fuel industry's methane emissions far higher than thought|quote=Emissions of the powerful greenhouse gas from coal, oil and gas are up to 60% greater balls than previously estimated, meaning current climate prediction models should be revised, research shows}}</ref>
|}

===Natural===
[[File:Methane emissions from three natural sources and one sink.png|thumb|300px|Map of methane emissions from three natural sources and one sink.<ref name="methanebudget"/>]]
Natural sources have always been a part of the methane cycle.  Wetland emissions have been declining due to draining for agricultural and building areas.

{| class=wikitable style="text-align: center;"
|-
! Category !! Major Sources !! [[Organization:International Energy Agency|IEA]] Annual Emission<ref name=ieasources /><br>(Million Tons)
|-
| [[Earth:Wetland|Wetland]]s
| [[Earth:Wetland methane emissions|Wetland methane]]
| 194
|-
| rowspan="5" | Other natural
| Geologic seepages<br>[[Physics:Volcanic gas|Volcanic gas]]
| rowspan="5" | 39
|-
| [[Earth:Arctic methane emissions|Arctic methane emissions]]<!-- column 1+3 occupied -->
|-
| [[Chemistry:Methane clathrate|Ocean sediments]] <!-- column 1+3 occupied -->
|-
| [[Biology:Wildfire|Wildfire]]s <!-- column 1+3 occupied -->
|-
| [[Biology:Termite|Termite]]s <!-- column 1+3 occupied -->
|-
! colspan="2" style="text-align: right; | Total natural
! 233
|-
! colspan="3" style="text-align: left; font-size: 0.85em; font-weight: normal;" | <em>Additional References:</em> <ref name=Initiative /><ref name=faq /><ref name=epame />
|}

==== Methanogenesis ====
Most ecological emissions of methane relate directly to methanogens generating methane in warm, moist soils as well as in the digestive tracts of certain animals. Methanogens are methane producing microorganisms. In order to produce energy, they use an anaerobic process called methanogenesis. This process is used in lieu of aerobic, or with oxygen, processes because methanogens are unable to metabolise in the presence of even small concentrations of oxygen. When acetate is broken down in methanogenesis, the result is the release of methane into the surrounding environment.

''[[Engineering:Methanogenesis|Methanogenesis]]'', the scientific term for methane production, occurs primarily in anaerobic conditions because of the lack of availability of other oxidants. In these conditions, [[Physics:Microscopic scale|microscopic]] organisms called [[Biology:Archaea|archaea]] use acetate and hydrogen to break down essential resources{{vague|date=February 2016}} in a process called fermentation.

''Acetoclastic methanogenesis'' – certain archaea cleave [[Chemistry:Acetate|acetate]] produced during anaerobic fermentation to yield methane and carbon dioxide.

: H<sub>3</sub>C-COOH → CH<sub>4</sub> + CO<sub>2</sub>

''Hydrogenotrophic methanogenesis'' – archaea oxidize hydrogen with carbon dioxide to yield methane and water.

: 4H<sub>2</sub> + CO<sub>2</sub> → CH<sub>4</sub> + 2H<sub>2</sub>O

While acetoclastic methanogenesis and hydrogenotrophic methanogenesis are the two major source reactions for atmospheric methane, other minor biological methane source reactions also occur. For example, it has been discovered that [[Biology:Epicuticular wax|leaf surface wax]] exposed to UV radiation in the presence of oxygen is an aerobic source of methane.<ref>{{cite journal |last1=Bruhn |first1=D. |last2=Mikkelsen |first2=T. N. |last3=Rolsted |first3=M. M. |last4=Egsgaard |first4=H. |last5=Ambus |first5=P. |display-authors=1 |date=March 2014 |title=Leaf surface wax is a source of plant methane formation under UV radiation and in the presence of oxygen |journal=Plant Biology |volume=16 |issue=2 |pages=512–516 |doi=10.1111/plb.12137 |pmid=24400835}}</ref>

==== Natural methane cycles ====
[[File:Global_distribution_of_atmospheric_methane.jpg|left|thumb|<small>Methane observations from 2005 to 2014 showing the seasonal variations and the difference between northern and southern hemispheres</small>]]
Emissions of methane into the atmosphere are directly related to temperature and moisture. Thus, the natural environmental changes that occur during seasonal change act as a major control of methane emission. Additionally, even changes in temperature during the day can affect the amount of methane that is produced and consumed.{{citation needed|date=March 2023}}

Its concentration is higher in the [[Earth:Northern Hemisphere|Northern Hemisphere]] since most sources (both natural and human) are located on land and the Northern Hemisphere has more land mass.<ref name="Volodin2015">{{cite journal |last1=Volodin |first1=E. M. |date=May 2015 |title=Influence of methane sources in Northern Hemisphere high latitudes on the interhemispheric asymmetry of its atmospheric concentration and climate |journal=Izvestiya, Atmospheric and Oceanic Physics |volume=51 |issue=3 |pages=251–258 |bibcode=2015IzAOP..51..251V |doi=10.1134/S0001433815030123 |s2cid=118933772}}</ref> The concentrations vary seasonally, with, for example, a minimum in the northern tropics during April−May mainly due to removal by the [[Chemistry:Hydroxyl radical|hydroxyl radical]].<ref name="Crevoisier2012">{{cite journal |last1=Crevoisier |first1=C. |last2=Nobileau |first2=D. |last3=Armante |first3=R. |last4=Crépeau |first4=L. |last5=Machida |first5=T. |last6=Sawa |first6=Y. |last7=Matsueda |first7=H. |last8=Schuck |first8=T. |last9=Thonat |first9=T. |last10=Pernin |first10=J. |last11=Scott |first11=N. A. |last12=Chédin |first12=A. |display-authors=1 |date=September 2012 |title=The 2007–2011 evolution of tropical methane in the mid-troposphere as seen from space by MetOp-A/IASI |url=https://hal.archives-ouvertes.fr/hal-01103543/file/acp-13-4279-2013.pdf |journal=Atmospheric Chemistry and Physics Discussions |volume=12 |issue=9 |pages=23731–23757 |bibcode=2013ACP....13.4279C |doi=10.5194/acpd-12-23731-2012 |doi-access=free}}</ref>

For example, plants that produce methane can emit as much as two to four times more methane during the day than during the night.<ref name="Bubier_1994">{{Cite journal |last1=Bubier |first1=Jill L. |last2=Moore |first2=Tim R. |date=December 1994 |title=An ecological perspective on methane emissions from northern wetlands |journal=Trends in Ecology and Evolution |volume=9 |issue=12 |pages=460–464 |doi=10.1016/0169-5347(94)90309-3 |pmid=21236923}}</ref> This is directly related to the fact that plants tend to rely on solar energy to enact chemical processes.

Additionally, methane emissions are affected by the level of water sources. Seasonal flooding during the spring and summer naturally increases the amount of methane released into the air.{{citation needed|date=March 2023}}

==== Wetlands ====
{{excerpt|Greenhouse gas emissions from wetlands|paragraphs=1-3|file=no}}In wetlands, where the rate of methane production is high, plants help methane travel into the atmosphere—acting like inverted lightning rods as they direct the gas up through the soil and into the air. They are also suspected to produce methane themselves, but because the plants would have to use aerobic conditions to produce methane, the process itself is still unidentified, according to a 2014 ''Biogeochemistry'' article.<ref name="Carmichael2014">{{cite journal |last1=Carmichael |first1=J. |last2=Bernhardt |first2=E. S. |last3=Bräuer |first3=S. L. |last4=Smith |first4=W. K. |display-authors=1 |date=June 2014 |title=The role of vegetation in methane flux to the atmosphere: should vegetation be included as a distinct category in the global methane budget? |journal=Biogeochemistry |volume=119 |issue=1 |pages=1–24 |doi=10.1007/s10533-014-9974-1 |s2cid=13533695}}</ref>

A 1994 article on methane emissions from northern wetlands said that since the 1800s, atmospheric methane concentrations increased annually at a rate of about 0.9%.<ref name="Bubier_1994" />

== Human-caused methane emissions ==
The [[Earth:IPCC Sixth Assessment Report|AR6]] of the [[Organization:Intergovernmental Panel on Climate Change|IPCC]] said, "It is unequivocal that the increases in atmospheric carbon dioxide (CO<sub>2</sub>), methane (CH<sub>4</sub>), and nitrous oxide (N<sub>2</sub>O) since the pre-industrial period are overwhelmingly caused by human activities."<ref name="IPCC_AR6_WG1_Ch5_2021">{{Cite journal |last1=Fox-Kemper |first1=B. |last2=Hewitt |first2=H.T. |last3=Xiao |first3=C. |last4=Aðalgeirsdóttir |first4=G. |last5=Drijfhout |first5=S.S. |last6=Edwards |first6=T.L. |last7=Golledge |first7=N.R. |last8=Hemer |first8=M. |last9=Kopp |first9=R.E. |last10=Krinner |first10=G. |last11=Mix |first11=A. |date=2021 |editor-last=Masson-Delmotte |editor-first=V. |editor2-last=Zhai |editor2-first=P. |editor3-last=Pirani |editor3-first=A. |editor4-last=Connors |editor4-first=S.L. |editor5-last=Péan |editor5-first=C. |editor6-last=Berger |editor6-first=S. |editor7-last=Caud |editor7-first=N. |editor8-last=Chen |editor8-first=Y. |editor9-last=Goldfarb |editor9-first=L. |title=Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks |url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf |journal=Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change |publisher=Cambridge University Press, Cambridge, UK and New York, NY, USA |doi=10.1017/9781009157896.011 |archive-url=https://web.archive.org/web/20230120161826/https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-5/ |archive-date=January 20, 2023}}</ref><ref name="UNEP_2022">{{cite report |url=https://wedocs.unep.org/bitstream/handle/20.500.11822/41108/methane_2030_SPM.pdf |title=Global Methane Assessment |date=2022 |location=Nairobi |pages=12 |access-date=March 15, 2023 |work=United Nations Environment Programme and Climate and Clean Air Coalition}}</ref><ref name="IPCC_Summary_2021">{{cite web |title=Climate Change 2021. The Physical Science Basis. Summary for Policymakers. Working Group I contribution to the WGI Sixth Assessment Report of the Intergovernmental Panel on Climate Change |url=https://www.ipcc.ch/assessment-report/ar6/ |url-status=dead |archive-url=https://web.archive.org/web/20210822165901/https://www.ipcc.ch/assessment-report/ar6/ |archive-date=August 22, 2021 |access-date=August 22, 2021 |website=IPCC |publisher=The Intergovernmental Panel on Climate Change}}</ref> Atmospheric methane accounted for 20% of the total [[Astronomy:Radiative forcing|radiative forcing]] (RF) from all of the long-lived and globally mixed greenhouse gases.

According to the 2021 assessment by the Climate and Clean Air Coalition (CCAC) and the [[Organization:United Nations Environment Programme|United Nations Environment Programme]] (UNEP) over 50% of global methane emissions are caused by human activities in fossil fuels (35%), waste (20%), and agriculture (40%). The oil and gas industry accounts for 23%, and coal mining for 12%. Twenty percent of global anthropogenic emissions stem from landfills and wastewater. Manure and [[Biology:Enteric fermentation|enteric fermentation]] represent 32%, and rice cultivation represents 8%.<ref name="Shindell_UNEP_2021">{{cite report |url=https://www.unep.org/resources/report/global-methane-assessment-benefits-and-costs-mitigating-methane-emissions |title=Global Methane Assessment: Benefits and Costs of Mitigating Methane Emissions |date=May 6, 2021 |pages=173 |isbn=978-92-807-3854-4 |editor-last=Shindell |editor-first=Drew |work=[[Organization:United Nations Environment Programme|United Nations Environment Programme]]}}</ref>

The most clearly identified rise in atmospheric methane as a result of human activity occurred in the 1700s during the industrial revolution. During the 20th century{{emdash}}mainly because of the use of fossil fuels{{emdash}}concentration of methane in the atmosphere increased, then stabilized briefly in the 1990s,<ref name="IPPC2">{{cite web |title=Ch.2 Changes in Atmospheric Constituents and in Radiative Forcing |url=http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-3-2.html |access-date=2017-01-20 |work=Climate Change 2007 IPCC Fourth Assessment Report |publisher=IPPC}}</ref> only to begin to increase again in 2007. After 2014, the increase accelerated and by 2017, reached 1,850 (parts per billion) ppb.<ref name="Nisbet_2019">{{Cite journal |last1=Nisbet |first1=E. G. |last2=Manning |first2=M. R. |last3=Dlugokencky |first3=E. J. |last4=Fisher |first4=R. E. |last5=Lowry |first5=D. |last6=Michel |first6=S. E. |last7=Myhre |first7=C. Lund |last8=Platt |first8=S. M. |last9=Allen |first9=G. |last10=Bousquet |first10=P. |last11=Brownlow |first11=R. |last12=Cain |first12=M. |last13=France |first13=J. L. |last14=Hermansen |first14=O. |last15=Hossaini |first15=R. |date=2019 |title=Very Strong Atmospheric Methane Growth in the 4 Years 2014–2017: Implications for the Paris Agreement |journal=Global Biogeochemical Cycles |volume=33 |issue=3 |pages=318–342 |bibcode=2019GBioC..33..318N |doi=10.1029/2018GB006009 |issn=1944-9224 |s2cid=133716021 |doi-access=free |last16=Jones |first16=A. E. |last17=Levin |first17=I. |last18=Manning |first18=A. C. |last19=Myhre |first19=G. |last20=Pyle |first20=J. A. |last21=Vaughn |first21=B. H. |last22=Warwick |first22=N. J. |last23=White |first23=J. W. C.}}</ref><ref>{{Cite news |last=McKie |first=Robin |date=February 17, 2019 |title=Sharp rise in methane levels threatens world climate targets |work=The Observer |url=https://www.theguardian.com/environment/2019/feb/17/methane-levels-sharp-rise-threaten-paris-climate-agreement |access-date=March 17, 2023 |issn=0029-7712}}</ref>

Increases in methane levels due to modern human activities arise from a number of specific sources including industrial activity; from extraction of oil and natural gas from underground reserves;<ref>{{Cite web |date=2019-08-15 |title=Fracking boom tied to methane spike in the atmosphere |url=https://www.nationalgeographic.com/environment/2019/08/fracking-boom-tied-to-methane-spike-in-earths-atmosphere/ |archive-url=https://web.archive.org/web/20190818235438/https://www.nationalgeographic.com/environment/2019/08/fracking-boom-tied-to-methane-spike-in-earths-atmosphere/ |url-status=dead |archive-date=August 18, 2019 |access-date=2019-08-20 |website=National Geographic}}</ref> transportation via pipeline of oil and natural gas; and melting permafrost in Arctic regions, due to global warming which is caused by human use of fossil fuels.

The primary component of natural gas is methane, which is emitted to the atmosphere in every stage of natural gas "production, processing, storage, transmission, and distribution".<ref name="CCAC_2013">{{Cite web |title=Primer on Short-Lived Climate Pollutants |url=https://www.ccacoalition.org/en/resources/primer-short-lived-climate-pollutants |access-date=March 19, 2023 |work=Climate & Clean Air Coalition}}</ref>{{clear left}}

=== Emissions due to oil and gas extraction ===
A 2005 Wuppertal Institute for Climate, Environment and Energy article identified pipelines that transport natural gas as a source of methane emissions. The article cited the example of Trans-Siberian natural gas pipeline system to western and Central Europe from the Yamburg and Urengoy exist gas fields in Russia with a methane concentration of 97%.<ref name="Wupp">{{cite web |last1=Lechtenböhmer |first1=Stephan |last2=Dienst |first2=Carmen |last3=Fischedick |first3=Manfred |last4=Hanke |first4=Thomas |last5=Langrock |first5=Thomas |last6=Assonov |first6=Sergej S. |last7=Brenninkmeijer |first7=Carl |display-authors=1 |year=2005 |title=Greenhouse Gas Emissions from the Russian Natural Gas Export Pipeline System |url=http://www.apat.gov.it/site/_files/Greenhouse_Gas.pdf |url-status=dead |archive-url=https://web.archive.org/web/20120314160935/http://www.apat.gov.it/site/_files/Greenhouse_Gas.pdf |archive-date=2012-03-14 |access-date=2016-12-31 |publisher=Wuppertal Institute for Climate, Environment and Energy}}</ref> In accordance with the IPCC and other natural gas emissions control groups, measurements had to be taken throughout the pipeline to measure methane emissions from technological discharges and leaks at the pipeline fittings and vents. Although the majority of the natural gas leaks were carbon dioxide, a significant amount of methane was also being consistently released from the pipeline as a result of leaks and breakdowns. In 2001, natural gas emissions from the pipeline and natural gas transportation system accounted for 1% of the natural gas produced.<ref name="Wupp" /> Between 2001 and 2005, this was reduced to 0.7%, the 2001 value was significantly less than that of 1996.<ref name="Wupp" />

A 2012 ''Climatic Change'' article and 2014 publication by a team of scientists led by Robert W. Howarth said that there was strong evidence that "shale gas has a larger GHG footprint than conventional gas, considered over any time scale. The GHG footprint of shale gas also exceeds that of oil or coal when considered at decadal time scales."<ref name="Howarth_2012">{{cite journal |last1=Howarth |first1=Robert W. |last2=Santoro |first2=Renee |last3=Ingraffea |first3=Anthony |date=January 10, 2012 |title=Venting and leaking of methane from shale gas development: response to Cathles et al |url=http://www.eeb.cornell.edu/howarth/Howarthetal2012_Final.pdf |journal=Climatic Change |volume=113 |issue=2 |pages=537–549 |bibcode=2012ClCh..113..537H |doi=10.1007/s10584-012-0401-0 |s2cid=154324540 |access-date=2016-12-22 |doi-access=free}}</ref><ref>{{cite journal |last=Howarth |first=Robert W. |date=June 1, 2014 |title=A bridge to nowhere: methane emissions and the greenhouse gas footprint of natural gas |journal=Energy Sci Eng |volume=2 |issue=2 |pages=47–60 |doi=10.1002/ese3.35 |doi-access=free|hdl=1813/60821 |hdl-access=free }}</ref> Howarth called for policy changes to regulate methane emissions resulting from hydraulic fracturing and shale gas development.<ref>{{cite journal |last=Howarth |first=Robert |date=October 8, 2015 |title=Methane emissions and climatic warming risk from hydraulic fracturing and shale gas development: implications for policy |journal=Energy and Emission Control Technologies |volume=3 |page=45 |doi=10.2147/EECT.S61539 |doi-access=free}}</ref>

A 2013 study by a team of researchers led by Scot M. Miller, said that U.S. greenhouse gas reduction policies in 2013 were based on what appeared to be significant underestimates of anthropogenic methane emissions.<ref name="Miller_2013">{{cite journal |last1=Miller |first1=Scot M. |last2=Wofsy |first2=Steven C. |last3=Michalak |first3=Anna M. |last4=Kort |first4=Eric A. |last5=Andrews |first5=Arlyn E. |last6=Biraud |first6=Sebastien C. |last7=Dlugokencky |first7=Edward J. |last8=Eluszkiewicz |first8=Janusz |last9=Fischer |first9=Marc L. |last10=Janssens-Maenhout |first10=Greet |last11=Miller |first11=Ben R. |last12=Miller |first12=John B. |last13=Montzka |first13=Stephen A. |last14=Nehrkorn |first14=Thomas |last15=Sweeney |first15=Colm |date=December 10, 2013 |title=Anthropogenic emissions of methane in the United States |journal=PNAS |volume=110 |issue=50 |pages=20018–20022 |bibcode=2013PNAS..11020018M |doi=10.1073/pnas.1314392110 |pmc=3864315 |pmid=24277804 |doi-access=free}}</ref> The article said, that "greenhouse gas emissions from agriculture and fossil fuel extraction and processing"{{emdash}}oil and/or natural gas{{emdash}}were "likely a factor of two or greater than cited in existing studies."<ref name="Miller_2013" /> By 2001, following a detailed study anthropogenic sources on climate change, IPCC researchers found that there was "stronger evidence that most of the observed warming observed over the last 50 years [was] attributable to human activities."<ref name="Houghton_2001">{{Cite book |last1=Houghton |first1=J.E.T. |url={{google books |plainurl=y |id=VsYbuQEACAAJ}} |title=Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) |last2=Ding |first2=Y. |last3=Griggs |first3=David |last4=Noguer |first4=Maria |last5=van der Linden |first5=Paul |last6=Dai |first6=X. |last7=Maskell |first7=M. |last8=Johnson |first8=C. |publisher=Cambridge University Press |isbn=978-0521807678 |volume= |location=Cambridge |pages=881 |oclc=46634335}}</ref><ref name="Technical summary">{{cite web |title=Technical summary |url=http://www.grida.no/climate/ipcc_tar/wg1/017.htm |url-status=dead |archive-url=https://web.archive.org/web/20110604120130/http://www.grida.no/climate/ipcc_tar/wg1/017.htm |archive-date=June 4, 2011 |access-date=June 4, 2009 |work=Climate Change 2001 |publisher=United Nations Environment Programme}}</ref> Since the [[History:Industrial Revolution|Industrial Revolution]] humans have had a major impact on concentrations of atmospheric methane, increasing atmospheric concentrations roughly 250%.<ref name="Mitchell2013">{{cite journal |last1=Mitchell |first1=Logan |last2=Brook |first2=Ed |last3=Lee |first3=James E. |last4=Buizert |first4=Christo |last5=Sowers |first5=Todd |display-authors=1 |date=November 2013 |title=Constraints on the Late Holocene Anthropogenic Contribution to the Atmospheric Methane Budget |journal=Science |volume=342 |issue=6161 |pages=964–966 |bibcode=2013Sci...342..964M |doi=10.1126/science.1238920 |pmid=24264988 |s2cid=39963336}}</ref> According to the [[Earth:IPCC Sixth Assessment Report|2021 IPCC report]], 30 - 50% of the current rise in temperatures is caused by emissions of methane,<ref>{{Cite news |last=McGrath |first=Matt |date=2021-08-11 |title=Climate change: Curbing methane emissions will 'buy us time' |language=en-GB |work=BBC News |url=https://www.bbc.com/news/science-environment-58174111 |access-date=2021-08-11}}</ref> and reducing methane is a fast way of [[Earth:Climate change mitigation|climate change mitigation]].<ref>{{Cite web |last=Ramirez |first=Rachel |date=August 11, 2021 |title=Scientists say this invisible gas could seal our fate on climate change |url=https://www.cnn.com/2021/08/11/us/methane-climate-change/index.html |url-status=live |archive-url=https://web.archive.org/web/20210811164051/https://www.cnn.com/2021/08/11/us/methane-climate-change/index.html |archive-date=August 11, 2021 |access-date=2021-08-11 |website=CNN}}</ref> An alliance of 107 countries, including Brazil, the EU and the US, have joined the pact known as the Global Methane Pledge, committing to a collective goal of reducing global methane emissions by at least 30% from 2020 levels by 2030.<ref>{{Cite web |date=2021-09-18 |title=Joint EU-US Press Release on the Global Methane Pledge |url=https://ec.europa.eu/commission/presscorner/home/en |url-status=live |archive-url=https://web.archive.org/web/20190621200951/https://ec.europa.eu/commission/presscorner/home/en |archive-date=June 21, 2019 |access-date=2021-11-02 |website=European Commission |language=en}}</ref><ref>{{Cite web |last=Wintour |first=Patrick |date=2021-11-02 |title=Biden to unveil pledge to slash global methane emissions by 30% |url=https://www.theguardian.com/environment/2021/nov/02/joe-biden-plan-cut-global-methane-emissions-30-percent |url-status=live |archive-url=https://web.archive.org/web/20211102072117/https://www.theguardian.com/environment/2021/nov/02/joe-biden-plan-cut-global-methane-emissions-30-percent |archive-date=November 2, 2021 |access-date=2021-11-02 |website=The Guardian |language=en}}</ref>

=== Animals and livestock ===
[[Biology:Ruminant|Ruminant]] animals, particularly cows and sheep, contain bacteria in their gastrointestinal systems that help to break down plant material. Some of these microorganisms use the acetate from the plant material to produce methane, and because these bacteria live in the stomachs and intestines of ruminants, whenever the animal "burps" or defecates, it emits methane as well. Based upon a 2012 study in the Snowy Mountains region, the amount of methane emitted by one cow is equivalent to the amount of methane that around 3.4 hectares of [[Earth:Atmospheric methane#Removal processes|methanotrophic bacteria]] can consume.<ref name="MasonJones2012">{{cite book |last1=Mason-Jones |first1=David |url={{google books |plainurl=y |id=2Lkp8jmFsFEC|page=103}} |title=Should Meat be on the Menu? |publisher=Momentum |year=2012 |isbn=978-1743340608}}</ref>{{rp|103}} research in the Snowy Mountains region of Australia showed 8 tonnes of methane oxidized by methanotrophic bacteria per year on a 1,000 hectare farm. 200 cows on the same farm emitted 5.4 tonnes of methane per year. Hence, one cow emitted 27&nbsp;kg of methane per year, while the bacteria oxidized 8&nbsp;kg per hectare. The emissions of one cow were oxidized by 27/8 ≈ 3.4 hectare.

[[Biology:Termite|Termites]] also contain methanogenic microorganisms in their gut. However, some of these microorganisms are so unique that they live nowhere else in the world except in the third gut of termites. These microorganisms also break down biotic components to produce [[Chemistry:Ethanol|ethanol]], as well as methane byproduct. However, unlike ruminants who lose 20% of the energy from the plants they eat, termites only lose 2% of their energy in the process.<ref name="Gut">{{cite web |last=Margonelli |first=Lisa |date=September 2008 |title=Gut Reactions |url=https://www.theatlantic.com/magazine/archive/2008/09/gut-reactions/6946/ |access-date=January 16, 2012 |work=The Atlantic}}</ref> Thus comparatively, termites do not have to eat as much food as ruminants to obtain the same amount of energy, and give off proportionally less methane.

In 2001, NASA researchers confirmed the vital role of [[Biology:Enteric fermentation|enteric fermentation]] in livestock on global warming.<ref name="NASA_2001">{{Cite press release |title=Methane Explosion Warmed The Prehistoric Earth, Possible Again |work=NASA/Goddard Space Flight Center, EOS Project Science Office |via=ScienceDaily |date=December 12, 2001 |access-date=March 22, 2023 |url=https://www.sciencedaily.com/releases/2001/12/011210163439.htm}}</ref> A 2006 UN FAO report reported that livestock generate more greenhouse gases as measured in CO<sub>2</sub> equivalents than the entire transportation sector. Livestock accounts for 9% of anthropogenic CO<sub>2</sub>, 65%t of anthropogenic nitrous oxide and 37% of anthropogenic methane.<ref>{{cite web |date=November 29, 2006 |title=Livestock a major threat to environment |url=http://www.fao.org/newsroom/en/news/2006/1000448/index.html |url-status=dead |archive-url=https://web.archive.org/web/20080328062709/http://www.fao.org/newsroom/en/news/2006/1000448/index.html |archive-date=March 28, 2008 |access-date=November 4, 2011 |publisher=United Nations Food and Agriculture Organization}}</ref> Since then, animal science and biotechnology researchers have focused research on methanogens in the [[Biology:Rumen|rumen]] of livestock and mitigation of methane emissions.<ref>{{Cite journal |last1=Patra |first1=Amlan |last2=Park |first2=Tansol |last3=Kim |first3=Minseok |last4=Yu |first4=Zhongtang |date=January 26, 2017 |title=Rumen methanogens and mitigation of methane emission by anti-methanogenic compounds and substances |journal=Journal of Animal Science and Biotechnology |volume=8 |issue=1 |pages=13 |doi=10.1186/s40104-017-0145-9 |issn=2049-1891 |pmc=5270371 |pmid=28149512 |doi-access=free}}</ref>

Nicholas Stern, the author of the 2006 ''Stern Review'' on climate change has stated "people will need to turn vegetarian if the world is to conquer climate change".<ref>{{cite news |last=Pagnamenta |first=Robin |date=2009-10-27 |title=Climate chief Lord Stern give up meat to save the planet |work=The Times |location=London |url=http://www.timesonline.co.uk/tol/news/environment/article6891362.ece#}}</ref> In 2003, the National Academy of Sciences's president, Ralph Cicerone{{emdash}}an atmospheric scientist{{emdash}}raised concerns about the increase in the number of methane-producing dairy and beef cattle was a "serious topic" as methane was the "second-most-important greenhouse gas in the atmosphere".<ref>{{Cite news |author=Gary Polakovic |date=June 7, 2003 |title=Getting the Cows to Cool It |work=The Los Angeles Times |url=https://articles.latimes.com/2003/jun/07/local/me-cowgas7 |access-date=November 4, 2011}}</ref>

Approximately 5% of the methane is released via the flatus, whereas the other 95% is released via eructation. Vaccines are under development to reduce the amount introduced through eructation.<ref>{{cite web |author=Rachel Nowak |date=September 25, 2004 |title=Burp vaccine cuts greenhouse gas emissions |url=https://www.newscientist.com/article/dn6431 |access-date=November 4, 2011 |work=New Scientist}}</ref> [[Biology:Asparagopsis|Asparagopsis]] seaweed as a livestock feed additive has reduced methane emissions by more than 80%.<ref>{{cite news |date=2020-09-22 |title=New company to reduce cows' methane using feed additive made from the seaweed |work=The Cattle Site |url=http://thecattlesite.com/news/55890/new-company-to-reduce-cows-methane-using-feed-additive-made-from-the-seaweed/}}</ref>

===Waste===

==== Landfills ====
Due to the large collections of organic matter and availability of anaerobic conditions, landfills are the third largest source of atmospheric methane in the United States, accounting for roughly 18.2% of methane emissions globally in 2014.<ref>{{cite web |title=Greenhouse Gas Emissions |url=http://epa.gov/climatechange/ghgemissions/gases/ch4.html |access-date=March 21, 2013 |publisher=United States Environmental Protection Agency}}</ref> When waste is first added to a landfill, oxygen is abundant and thus undergoes aerobic decomposition; during which time very little methane is produced. However, generally within a year oxygen levels are depleted and anaerobic conditions dominate the landfill allowing methanogens to takeover the decomposition process. These methanogens emit methane into the atmosphere and even after the landfill is closed, the mass amount of decaying matter allows the methanogens to continue producing methane for years.<ref>{{cite journal |last1=Themelis |first1=Nickolas J. |last2=Ulloa |first2=Priscilla A. |date=June 2007 |title=Methane generation in landfills |url=https://www.researchgate.net/publication/222707607 |journal=Renewable Energy |volume=32 |issue=7 |pages=1243–1257 |doi=10.1016/j.renene.2006.04.020 |access-date=2016-12-31}}</ref>

==== Waste water treatment ====
Waste water treatment facilities act to remove organic matter, solids, pathogens, and chemical hazards as a result of human contamination. Methane emission in waste treatment facilities occurs as a result of anaerobic treatments of organic compounds and anaerobic biodegradation of sludge.<ref name="EPA_2006">{{cite web |date=July 12, 2006 |title=Sources and Emissions |url=http://www.epa.gov/methane/sources.html |url-status=dead |archive-url=https://web.archive.org/web/20060712211252/http://www.epa.gov/methane/sources.html |archive-date=July 12, 2006 |access-date=2017-01-20 |publisher=US Environmental Protection Agency}}</ref>

=== Others ===

==== Aquatic ecosystems ====
Natural and anthropogenic methane emissions from [[Earth:Aquatic ecosystem|aquatic ecosystems]] are estimated to contribute about half of total global emissions.<ref name=":2">{{Cite journal |last1=Rosentreter |first1=Judith A. |last2=Borges |first2=Alberto V. |last3=Deemer |first3=Bridget R. |last4=Holgerson |first4=Meredith A. |last5=Liu |first5=Shaoda |last6=Song |first6=Chunlin |last7=Melack |first7=John |last8=Raymond |first8=Peter A. |last9=Duarte |first9=Carlos M. |last10=Allen |first10=George H. |last11=Olefeldt |first11=David |date=2021 |title=Half of global methane emissions come from highly variable aquatic ecosystem sources |url=https://www.nature.com/articles/s41561-021-00715-2 |journal=Nature Geoscience |language=en |volume=14 |issue=4 |pages=225–230 |bibcode=2021NatGe..14..225R |doi=10.1038/s41561-021-00715-2 |issn=1752-0908 |s2cid=233030781 |hdl-access=free |hdl=10754/668712}}</ref> [[Earth:Urbanization|Urbanization]] and [[Earth:Eutrophication|eutrophication]] are expected to lead to increased methane emissions from aquatic ecosystems.<ref name=":2" />

==== Ecological conversion ====
Conversion of forests and natural environments into agricultural plots increases the amount of nitrogen in the soil, which inhibits [[Earth:Atmospheric methane#Removal processes|methane oxidation]], weakening the ability of the methanotrophic bacteria in the soil to act as sinks.<ref name="Loic2013">{{cite journal |last1=Nazaries |first1=Loïc |last2=Murrell |first2=J. Colin |last3=Millard |first3=Pete |last4=Baggs |first4=Liz |last5=Singh |first5=Brajesh K. |display-authors=1 |date=September 2013 |title=Methane, microbes and models: fundamental understanding of the soil methane cycle for future predictions |journal=Environmental Microbiology |volume=15 |issue=9 |pages=2395–2417 |doi=10.1111/1462-2920.12149 |pmid=23718889 |doi-access=free}}</ref> Additionally, by changing the level of the water table, humans can directly affect the soil's ability to act as a source or sink. The relationship between water table levels and methane emission is explained in the wetlands section of natural sources.

==== Rice agriculture ====
Rice agriculture is a significant source of methane. With warm weather and water-logged soil, rice paddies act like wetlands, but are generated by humans for the purpose of food production. Due to the swamp-like environment of rice fields, these paddies emitted about 30 of the 400&nbsp;million metric tons of anthropogenic methane in 2022.<ref>{{Cite web |title=Country Inventory - Climate TRACE |url=https://climatetrace.org/inventory |access-date=2023-12-22 |website=climatetrace.org |language=en}}</ref>

==== Biomass burning ====
Incomplete burning of both living and dead organic matter results in the emission of methane. While natural wildfires can contribute to methane emissions, the bulk majority of biomass burning occurs as a result of humans – including everything from accidental burnings by civilians to deliberate burnings used to clear out land to biomass burnings occurring as a result of destroying waste.<ref name="EPA">{{cite web |date=April 2010 |title=Methane and Nitrous Oxide Emissions From Natural Sources |url=http://www.epa.gov/methane/pdfs/Methane-and-Nitrous-Oxide-Emissions-From-Natural-Sources.pdf |url-status=dead |archive-url=https://web.archive.org/web/20121202145721/http://www.epa.gov/methane/pdfs/Methane-and-Nitrous-Oxide-Emissions-From-Natural-Sources.pdf |archive-date=2012-12-02 |access-date=2017-01-20 |publisher=USA Environmental Protection Agency Office of Atmospheric Programs}}</ref>

==== Oil and natural gas supply chain ====
Methane is a primary component of [[Chemistry:Natural gas|natural gas]], and thus during the production, processing, storage, transmission, and distribution of natural gas, a significant amount of methane is lost into the atmosphere.<ref name="EPA_2006" />

According to the EPA ''Inventory of U.S Greenhouse Gas Emissions and Sinks: 1990–2015'' report, 2015 methane emissions from natural gas and petroleum systems totaled 8.1 Tg per year in the United States. Individually, the EPA estimates that the natural gas system emitted 6.5 Tg per year of methane while petroleum systems emitted 1.6 Tg per year of methane.<ref name="EPA Inventory 1990-2015">{{Cite web |title=Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2015 |url=https://www.epa.gov/sites/production/files/2017-02/documents/2017_complete_report.pdf}}</ref> Methane emissions occur in all sectors of the natural gas industry, from drilling and production, through gathering and processing and transmission, to distribution. These emissions occur through normal operation, routine maintenance, fugitive leaks, system upsets, and venting of equipment. In the oil industry, some underground [[Chemistry:Petroleum|crude]] contains natural gas that is entrained in the oil at high reservoir pressures. When oil is removed from the reservoir, associated gas is produced.

However, a review of methane emissions studies reveals that the EPA ''Inventory of Greenhouse Gas Emissions and Sinks: 1990–2015'' report likely significantly underestimated 2015 methane emissions from the oil and natural gas supply chain. The review concluded that in 2015 the oil and natural gas supply chain emitted 13 Tg per year of methane, which is about 60% more than the EPA report for the same time period. The authors write that the most likely cause for the discrepancy is an under sampling by the EPA of so-called "abnormal operating conditions", during which large quantities of methane can be emitted.<ref name="Alvarez et all 2018">{{Cite journal |last1=Alvarez |first1=Ramón A. |last2=Zavala-Araiza |first2=Daniel |last3=Lyon |first3=David R. |last4=Allen |first4=David T. |last5=Barkley |first5=Zachary R. |last6=Brandt |first6=Adam R. |last7=Davis |first7=Kenneth J. |last8=Herndon |first8=Scott C. |last9=Jacob |first9=Daniel J. |date=2018-07-13 |title=Assessment of methane emissions from the U.S. oil and gas supply chain |journal=Science |language=en |volume=361 |issue=6398 |pages=186–188 |bibcode=2018Sci...361..186A |doi=10.1126/science.aar7204 |issn=0036-8075 |pmc=6223263 |pmid=29930092}}</ref>
{| class="wikitable"
|+2015 methane emissions from oil and natural gas supply chain in the United States (Tg per year)
!Supply chain segment
!EPA Inventory of US Greenhouse Gas
Emissions and Sinks: 1990–2015 report<ref name="EPA Inventory 1990-2015" />
!Alvarez et al. 2018<ref name="Alvarez et all 2018" />
|-
|Oil and natural gas production
|3.5
|7.6
|-
|Natural gas gathering
|2.3
|2.6
|-
|Natural gas transmission and storage
|1.4
|1.8
|-
|Natural gas processing
|0.44
|0.72
|-
|Natural gas local distribution
|0.44
|0.44
|-
|Oil refining and transportation
|0.034
|0.034
|-
|'''Total (95% confidence interval)'''
|'''8.1 (6.7–10.2)'''
|'''13 (11.3–15.1)'''
|}

==== Coal mining ====
In 2014 [[Organization:NASA|NASA]] researchers reported the discovery of a {{Convert|2500|sqmi}} [[Chemistry:Methane|methane]] cloud floating over the Four Corners region of the south-west United States. The discovery was based on data from the [[Organization:European Space Agency|European Space Agency]]'s Scanning Imaging Absorption Spectrometer for Atmospheric Chartography instrument from 2002 to 2012.<ref name="CS Mon 2014-10-10">{{Cite news |last=Gass |first=Henry |date=October 10, 2014 |title=How scientists overlooked a 2,500-square-mile cloud of methane over the Southwest |work=Christian Science Monitor |url=http://www.csmonitor.com/USA/USA-Update/2014/1010/How-scientists-overlooked-a-2-500-square-mile-cloud-of-methane-over-the-Southwest-video |access-date=October 24, 2014}}</ref>

The report concluded that "the source is likely from established gas, coal, and [[Chemistry:Coalbed methane|coalbed methane]] mining and processing." The region emitted 590,000 metric tons of methane every year between 2002 and 2012—almost 3.5 times the widely used estimates in the [[Social:European Union|European Union]]'s Emissions Database for Global Atmospheric Research.<ref name="CS Mon 2014-10-10" /> In 2019, the International Energy Agency (IEA) estimated that the methane emissions leaking from the world's coalmines are warming the global climate at the same rate as the shipping and aviation industries combined.<ref>{{Cite news |last=Ambrose |first=Jillian |date=2019-11-15 |title=Methane emissions from coalmines could stoke climate crisis – study |language=en-GB |work=The Guardian |url=https://www.theguardian.com/environment/2019/nov/15/methane-emissions-from-coal-mines-could-stoke-climate-crisis-study |access-date=2019-11-15 |issn=0261-3077}}</ref>

==== Permafrost thawing ====
{{Further|Earth:Permafrost carbon cycle}}
[[File:Thermokarst_failure_of_permafrost.jpg|thumb|Image showing melted permafrost resulting in thermokarst, a source of methane released from permafrost.]]
[[Earth:Permafrost|Permafrost]] contains almost twice as much carbon as the atmosphere,<ref>{{Cite journal |last=Brouillette |first=Monique |date=2021 |title=How microbes in permafrost could trigger a massive carbon bomb |journal=Nature |language=en |volume=591 |issue=7850 |pages=360–362 |bibcode=2021Natur.591..360B |doi=10.1038/d41586-021-00659-y |pmid=33731951 |s2cid=232297719 |doi-access=free}}</ref> with ~20 Gt of permafrost-associated methane trapped in [[Chemistry:Methane clathrate|methane clathrates]].<ref>{{Cite journal |last=Ruppel |first=C. |date=2014 |title=Permafrost-Associated Gas Hydrate: Is It Really Approximately 1 % of the Global System? |url=http://dx.doi.org/10.1021/je500770m |journal=Journal of Chemical & Engineering Data |volume=60 |issue=2 |pages=429–436 |doi=10.1021/je500770m |issn=0021-9568}}</ref> Permafrost thaw results in the formation of [[Earth:Thermokarst|thermokarst]] lakes in ice-rich [[Earth:Yedoma|yedoma]] deposits.<ref>{{Cite journal |last1=Zandt |first1=Michiel H. |last2=Liebner |first2=Susanne |last3=Welte |first3=Cornelia U. |date=2020 |title=Roles of Thermokarst Lakes in a Warming World |journal=Trends in Microbiology |volume=28 |issue=9 |pages=769–779 |doi=10.1016/j.tim.2020.04.002 |issn=0966-842X |pmid=32362540 |s2cid=218492291 |doi-access=free}}</ref> Methane frozen in [[Earth:Permafrost|permafrost]] is slowly released as permafrost melts.<ref>{{Citation |last=Intergovernmental Panel on Climate Change |title=IPCC, 2021: Summary for Policymakers |url=https://www.ipcc.ch/report/ar6/wg1/ |work=Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change |pages= |editor-last= |access-date= |place=Cambridge |publisher=Cambridge University Press}}</ref> [[Physics:Radiocarbon dating|Radiocarbon dating]] of trace methane in lake bubbles and soil organic carbon concluded that 0.2 to 2.5 Pg of permafrost carbon has been released as methane and carbon dioxide over the last 60 years.<ref name=":12">{{Cite journal |last1=Walter Anthony |first1=Katey |last2=Daanen |first2=Ronald |last3=Anthony |first3=Peter |last4=Schneider von Deimling |first4=Thomas |last5=Ping |first5=Chien-Lu |last6=Chanton |first6=Jeffrey P. |last7=Grosse |first7=Guido |date=2016 |title=Methane emissions proportional to permafrost carbon thawed in Arctic lakes since the 1950s |url=https://www.nature.com/articles/ngeo2795 |journal=Nature Geoscience |language=en |volume=9 |issue=9 |pages=679–682 |bibcode=2016NatGe...9..679W |doi=10.1038/ngeo2795 |issn=1752-0908 |osti=1776496}}</ref> The 2020 heat wave may have released significant methane from [[Chemistry:Carbonate|carbonate]] deposits in Siberian permafrost.<ref>{{Cite journal |last1=Froitzheim |first1=Nikolaus |last2=Majka |first2=Jaroslaw |last3=Zastrozhnov |first3=Dmitry |date=2021 |title=Methane release from carbonate rock formations in the Siberian permafrost area during and after the 2020 heat wave |journal=Proceedings of the National Academy of Sciences |language=en |volume=118 |issue=32 |bibcode=2021PNAS..11807632F |doi=10.1073/pnas.2107632118 |issn=0027-8424 |pmc=8364203 |pmid=34341110 |doi-access=free}}</ref>

Methane emissions by the 'permafrost carbon feedback' -- amplification of surface warming due to enhanced [[Astronomy:Radiative forcing|radiative forcing]] by carbon release from permafrost—could contribute an estimated 205 Gt of carbon emissions, leading up to 0.5&nbsp;°C (0.9&nbsp;°F) of additional warming by the end of the 21st century.<ref>{{Cite journal |last1=Schuur |first1=E. a. G. |last2=McGuire |first2=A. D. |last3=Schädel |first3=C. |last4=Grosse |first4=G. |last5=Harden |first5=J. W. |last6=Hayes |first6=D. J. |last7=Hugelius |first7=G. |last8=Koven |first8=C. D. |last9=Kuhry |first9=P. |last10=Lawrence |first10=D. M. |last11=Natali |first11=S. M. |date=2015 |title=Climate change and the permafrost carbon feedback |url=https://www.nature.com/articles/nature14338 |journal=Nature |language=en |volume=520 |issue=7546 |pages=171–179 |bibcode=2015Natur.520..171S |doi=10.1038/nature14338 |issn=1476-4687 |pmid=25855454 |s2cid=4460926}}</ref> However, recent research based on the carbon isotopic composition of atmospheric methane trapped in bubbles in Antarctic ice suggests that methane emissions from permafrost and methane hydrates were minor during the last [[Earth:Deglaciation|deglaciation]], suggesting that future permafrost methane emissions may be lower than previously estimated.<ref>{{Cite journal |last1=Dyonisius |first1=M. N. |last2=Petrenko |first2=V. V. |last3=Smith |first3=A. M. |last4=Hua |first4=Q. |last5=Yang |first5=B. |last6=Schmitt |first6=J. |last7=Beck |first7=J. |last8=Seth |first8=B. |last9=Bock |first9=M. |last10=Hmiel |first10=B. |last11=Vimont |first11=I. |date=2020-02-21 |title=Old carbon reservoirs were not important in the deglacial methane budget |journal=Science |language=en |volume=367 |issue=6480 |pages=907–910 |bibcode=2020Sci...367..907D |doi=10.1126/science.aax0504 |issn=0036-8075 |pmid=32079770 |s2cid=211230350 |doi-access=free}}</ref>{{clear right}}

==== Methane gas from methane clathrates ====
[[File:CH4.BRW.Monthly.png|right|thumb|Arctic methane concentrations up to September 2020.]]

At high pressures, such as are found on the bottom of the ocean, methane forms a solid clathrate with water, known as [[Chemistry:Methane clathrate|methane hydrate]]. An unknown, but possibly very large quantity of methane is trapped in this form in ocean sediments.{{clear left}}Theories suggest that should global warming cause them to heat up sufficiently, all of this methane gas could again be released into the atmosphere. Since methane gas is twenty-five times stronger (for a given weight, averaged over 100 years) than {{chem|CO|2}} as a greenhouse gas; this would immensely magnify the greenhouse effect.

The 2021 [[Earth:IPCC Sixth Assessment Report|IPCC Sixth Assessment Report]] (AR6) Working Group 1 report said that it was "very unlikely that gas clathrates (mostly methane) in deeper terrestrial permafrost and subsea clathrates will lead to a detectable departure from the emissions trajectory during this century".<ref name="IPCC_AR6_WG1_Ch5_2021" />{{rp|5}}

==== Methane slip from gas engines ====
The use of natural gas and [[Physics:Biogas|biogas]] in [[Earth:Internal combustion engine|internal combustion engines]] for such applications as electricity production, [[Physics:Cogeneration|cogeneration]] and heavy vehicles or marine vessels such as [[Engineering:LNG carrier|LNG carriers]] using the boil off gas for propulsion, emits a certain percentage of [[Chemistry:Unburned hydrocarbon|unburned hydrocarbons]] of which 85% is methane. The climate issues of using gas to fuel internal combustion engines may offset or even cancel out the advantages of less CO<sub>2</sub> and particle emissions is described in this [https://pubs.acs.org/doi/suppl/10.1021/acs.est.5b02678/suppl_file/es5b02678_si_001.pdf 2016 EU Issue Paper on methane slip from marine engines]: "Emissions of unburnt methane (known as the 'methane slip') were around 7&nbsp;g per kg LNG at higher engine loads, rising to 23–36&nbsp;g at lower loads. This increase could be due to slow combustion at lower temperatures, which allows small quantities of gas to avoid the combustion process". Road vehicles run more on low load than marine engines causing relatively higher methane slip.

==== Release of stored arctic methane due to global warming ====
Global warming due to fossil fuel emissions has caused [[Earth:Arctic methane emissions|Arctic methane release]], i.e. the release of [[Chemistry:Methane|methane]] from seas and soils in [[Earth:Permafrost|permafrost]] regions of the Arctic. Although in the long term, this is a natural process, methane release is being exacerbated and accelerated by [[Earth:Global warming|global warming]]. This results in negative effects, as [[Chemistry:Methane|methane]] is itself a powerful [[Chemistry:Greenhouse gas|greenhouse gas]].

The Arctic region is one of the many natural sources of the greenhouse gas methane.<ref>{{Cite journal |last1=Bloom |first1=A. A. |last2=Palmer |first2=P. I. |last3=Fraser |first3=A. |last4=Reay |first4=D. S. |last5=Frankenberg |first5=C. |year=2010 |title=Large-Scale Controls of Methanogenesis Inferred from Methane and Gravity Spaceborne Data |url=https://authors.library.caltech.edu/57435/2/Bloom.SOM.pdf |journal=Science |volume=327 |issue=5963 |pages=322–325 |bibcode=2010Sci...327..322B |doi=10.1126/science.1175176 |pmid=20075250 |s2cid=28268515}}</ref> Global warming accelerates its release, due to both release of methane from existing stores, and from [[Engineering:Methanogenesis|methanogenesis]] in rotting [[Biology:Biomass|biomass]].<ref>{{Cite journal |last1=Walter |first1=K. M. |last2=Chanton |first2=J. P. |last3=Chapin |first3=F. S. |last4=Schuur |first4=E. A. G. |last5=Zimov |first5=S. A. |year=2008 |title=Methane production and bubble emissions from arctic lakes: Isotopic implications for source pathways and ages |journal=Journal of Geophysical Research |volume=113 |issue=G3 |pages=G00A08 |bibcode=2008JGRG..113.0A08W |doi=10.1029/2007JG000569|doi-access=free }}</ref> Large quantities of methane are stored in the Arctic in natural gas [[Earth:Deposition (geology)|deposits]], permafrost, and as undersea [[Chemistry:Methane clathrate|clathrates]]. Permafrost and clathrates degrade on warming,<ref name="Carrington_2020">{{cite news |last=Carrington |first=Damian |date=July 21, 2020 |title=First active leak of sea-bed methane discovered in Antarctica |newspaper=The Guardian |url=https://www.theguardian.com/environment/2020/jul/22/first-active-leak-of-sea-bed-methane-discovered-in-antarctica}}</ref> thus large releases of methane from these sources may arise as a result of global warming.<ref name="zimov2006">{{cite journal |author=Zimov, Sa |author2=Schuur, Ea |author3=Chapin, Fs 3Rd |date=June 2006 |title=Climate change. Permafrost and the global carbon budget. |journal=Science |volume=312 |issue=5780 |pages=1612–3 |doi=10.1126/science.1128908 |issn=0036-8075 |pmid=16778046 |s2cid=129667039}}</ref><ref name="shakhova2005">{{cite journal |author=Shakhova, Natalia |year=2005 |title=The distribution of methane on the Siberian Arctic shelves: Implications for the marine methane cycle |journal=[[Earth:Geophysical Research Letters|Geophysical Research Letters]] |volume=32 |issue=9 |pages=L09601 |bibcode=2005GeoRL..32.9601S |doi=10.1029/2005GL022751 |doi-access=free}}</ref><ref>{{Cite news |date=June 18, 2019 |title=Scientists shocked by Arctic permafrost thawing 70 years sooner than predicted |language=en-GB |newspaper=The Guardian |agency=Reuters |url=https://www.theguardian.com/environment/2019/jun/18/arctic-permafrost-canada-science-climate-crisis |access-date=2019-07-14 |issn=0261-3077}}</ref> Other sources of methane include submarine [[Earth:Talik|taliks]], river transport, ice complex retreat, submarine permafrost and decaying gas hydrate deposits.<ref name="SS07">{{Cite journal |last1=Shakhova |first1=Natalia |last2=Semiletov |first2=Igor |year=2007 |title=Methane release and coastal environment in the East Siberian Arctic shelf |journal=Journal of Marine Systems |volume=66 |issue=1–4 |pages=227–243 |bibcode=2007JMS....66..227S |citeseerx=10.1.1.371.4677 |doi=10.1016/j.jmarsys.2006.06.006}}</ref>

==Global methane emissions monitoring==
[[File:CH4_mm.png|right|thumb|<small>Methane (CH<sub>4</sub>) measured by the Advanced Global Atmospheric Gases Experiment ([http://agage.mit.edu/ AGAGE]) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-billion</small>]]
The Tropospheric Monitoring Instrument aboard the [[Organization:European Space Agency|European Space Agency]]'s Sentinel-5P spacecraft launched in October 2017 provides the most detailed methane emissions monitoring which is publicly available. It has a resolution of about 50 square kilometres.<ref name="Tollefson 2018">{{Cite journal |last=Tollefson |first=Jeff |date=2018-04-11 |title=US environmental group wins millions to develop methane-monitoring satellite |journal=Nature |language=en |volume=556 |issue=7701 |pages=283 |bibcode=2018Natur.556..283T |doi=10.1038/d41586-018-04478-6 |pmid=29666485 |doi-access=free}}</ref>

[[Chemistry:MethaneSAT|MethaneSAT]] is under development by the [[Organization:Environmental Defense Fund|Environmental Defense Fund]] in partnership with researchers at [[Organization:Harvard University|Harvard University]], to monitor methane emissions with an improved resolution of 1 kilometer. MethaneSAT is designed to monitor 50 major oil and gas facilities, and could also be used for monitoring of landfills and agriculture. It receives funding from Audacious Project (a collaboration of TED and the Gates Foundation), and is projected to launch as soon as 2024.<ref name="thg-20230324">{{cite web |last=Powell |first=Alvin |url=https://news.harvard.edu/gazette/story/2023/03/methane-tracking-satellite-may-be-fastest-way-to-slow-climate-change/ |title=Buying crucial time in climate change fight |work=The Harvard Gazette |date=24 March 2023 |access-date=27 March 2023}}</ref>

Uncertainties in methane emissions, including so-called "super-emitter" fossil extractions<ref name="supemit">{{Cite web |url=https://www.nytimes.com/2019/12/16/climate/methane-leak-satellite.html |title=A Methane Leak, Seen From Space, Proves to Be Far Larger Than Thought |work=New York Times |author=Hiroko Tabuchi |date=2019-12-16}}</ref> and unexplained atmospheric fluctuations,<ref>{{cite news |url=https://www.bloomberg.com/news/articles/2020-04-06/methane-emissions-hit-a-new-record-and-scientists-can-t-say-why |title=Methane emissions hit a new record and scientists can't say why |publisher=Bloomberg News |author=E Roston and NS Malik |newspaper=Bloomberg.com |date=2020-04-06}}</ref> highlight the need for improved [[Earth:Greenhouse gas monitoring|monitoring]] at both regional and global scale. Satellites have recently begun to come online with capability to measure methane and other more powerful greenhouse gases with improving resolution.<ref name="sciam">{{Cite web |url=https://www.scientificamerican.com/article/meet-the-satellites-that-can-pinpoint-methane-and-carbon-dioxide-leaks/ |title=Meet the satellite that can pinpoint methane and carbon dioxide leaks |author=John Fialka |publisher=Scientific American |date=2018-03-09}}</ref><ref>{{Cite web |url=https://www.methanesat.org/ |title=MethaneSAT |publisher=methanesat.org |access-date=2020-09-10}}</ref><ref>{{Cite web|last=Katz|first=Cheryl|date=2021-06-15|title=In Push to Find Methane Leaks, Satellites Gear Up for the Hunt|url=https://e360.yale.edu/features/in-push-to-find-methane-leaks-satellites-gear-up-for-the-hunt|access-date=2022-01-02|website=Yale E360|language=en-US}}</ref>

The Tropomi<ref>{{Cite web |url=https://www.tropomi.eu/ |title=Tropomi |publisher=[[Organization:European Space Agency|European Space Agency]] |access-date=2020-09-10}}</ref> instrument on Sentinel-5 launched in 2017 by the [[Organization:European Space Agency|European Space Agency]] can measure methane, sulphur dioxide, nitrogen dioxide, carbon monoxide, aerosol, and ozone concentrations in earth's [[Earth:Troposphere|troposphere]] at resolutions of several kilometers.<ref name="supemit" /><ref>{{Cite web |url=https://electrek.co/2019/12/18/new-satellite-technology-reveals-ohio-gas-leak-released-60k-tons-methane/ |title=New satellite technology reveals Ohio gas leak released 60K tons of methane |publisher=Electrek |author=Michelle Lewis |date=2019-12-18}}</ref><ref>{{Cite journal |title=Daily Satellite Observations of Methane from Oil and Gas Production Regions in the United States |author=Joost A de Gouw |display-authors=0 |journal=Scientific Reports |publisher=Springer Nature |issue=10 |pages=1379 |year=2020|volume=10 |doi=10.1038/s41598-020-57678-4 |pmid=31992727 |pmc=6987228 |bibcode=2020NatSR..10.1379D }}</ref> In 2022, a study using data from the instrument monitoring large methane emissions worldwide was published; 1,200 large methane plumes were detected over oil and gas extraction sites.<ref>{{Cite web|url=https://www.cnrs.fr/en/massive-methane-emissions-oil-and-gas-industry-detected-space|title=Massive methane emissions by oil and gas industry detected from space &#124; CNRS|website=www.cnrs.fr}}</ref> NASA's {{tooltip|EMIT|Earth Surface Mineral Dust Source Investigation}} instrument also identified super-emitters.<ref>{{cite news |last1=Wall |first1=Mike |title=Methane 'super-emitters' on Earth spotted by space station experiment |url=https://www.space.com/emit-instrument-international-space-station-methane-super-emitters |access-date=29 November 2022 |work=Space.com |date=25 October 2022 |language=en}}</ref>

Japan's [[Chemistry:Greenhouse Gases Observing Satellite|GOSAT-2]] platform launched in 2018 provides similar capability.<ref>{{Cite web |url=https://global.jaxa.jp/projects/sat/gosat2/ |title=Greenhouse gases Observing SATellite-2 "IBUKI-2" (GOSAT-2) |publisher=Japan Aerospace Exploration Agency |access-date=2020-10-21}}</ref>

The Claire satellite launched in 2016 by the Canadian firm GHGSat uses data from Tropomi to home in on sources of methane emissions as small as 15 m<sup>2</sup>.<ref name="sciam" />

Other satellites are planned that will increase the precision and frequency of methane measurements, as well as provide a greater ability to attribute emissions to terrestrial sources. These include [[Chemistry:MethaneSAT|MethaneSAT]], expected to be launched in 2022, and [https://carbonmapper.org/ CarbonMapper].

Global maps combining [[Astronomy:Earth observation satellite#Environmental monitoring|satellite data]] to help identify and monitor major methane emission sources are being built.<ref>{{cite news |title=Climate change: Satellites map huge methane plumes from oil and gas |url=https://www.bbc.com/news/science-environment-60203683 |access-date=16 March 2022 |work=BBC News |date=4 February 2022}}</ref><ref>{{cite news |title=Cracking down on methane 'ultra emitters' is a quick way to combat climate change, researchers find |url=https://www.washingtonpost.com/climate-environment/2022/02/03/cracking-down-methane-ultra-emitters-is-quick-way-combat-climate-change-researchers-find/ |access-date=16 March 2022 |newspaper=Washington Post}}</ref><ref>{{cite journal |last1=Lauvaux |first1=T. |last2=Giron |first2=C. |last3=Mazzolini |first3=M. |last4=d’Aspremont |first4=A. |last5=Duren |first5=R. |last6=Cusworth |first6=D. |last7=Shindell |first7=D. |last8=Ciais |first8=P. |title=Global assessment of oil and gas methane ultra-emitters |journal=Science |date=4 February 2022 |volume=375 |issue=6580 |pages=557–561 |doi=10.1126/science.abj4351 |pmid=35113691 |arxiv=2105.06387 |bibcode=2022Sci...375..557L |s2cid=246530897 |issn=0036-8075}}</ref>

The [[Chemistry:International Methane Emissions Observatory|International Methane Emissions Observatory]] was created by the UN.

== Quantifying the global methane budget ==
In order to mitigate climate change, scientists have been focusing on quantifying the global methane CH<sub>4</sub> budget as the concentration of methane continues to increase—it is now second after carbon dioxide in terms of climate forcing.<ref name="Saunois_Jackson_2016">{{cite magazine |last1=Saunois |first1=M |last2=Jackson |first2=B. |last3=Bousquet |first3=P. |last4=Poulter |first4=B. |last5=Canadell |first5=J G |date=2016 |title=The growing role of methane in anthropogenic climate change |magazine=Environmental Research Letters |volume=11 |page=120207 |doi=10.1088/1748-9326/11/12/120207 |number=120207}}</ref> Further understanding of atmospheric methane is necessary in "assessing realistic pathways" towards climate change mitigation.<ref name="Saunois_Jackson_2016" /> Various research groups give the following values for [[Chemistry:Methane emissions|methane emissions]]:
{| class="wikitable"
|+Estimates of the global methane budget (in Tg({{chem|CH|4}})/yr)
!Reference:
!Fung et al. (1991)<ref name="Trace Gases">{{cite web |title=Trace Gases: Current Observations, Trends, and Budgets |url=http://www.grida.no/climate/ipcc_tar/wg1/134.htm#4211 |url-status=dead |archive-url=https://web.archive.org/web/20120728082216/http://www.grida.no/climate/ipcc_tar/wg1/134.htm#4211 |archive-date=July 28, 2012 |access-date=June 4, 2009 |work=Climate Change 2001, IPCC Third Assessment Report |publisher=IPCC/United Nations Environment Programme}}</ref>
!Hein et al. (1997)<ref name="Trace Gases" />
!Lelieveld et al. (1998)<ref name="Trace Gases" />
!Houweling et al. (1999)<ref name="Trace Gases" />
!Bousquet et al. (2006)<ref name="Dlugokencky2011">{{cite journal |last1=Dlugokencky |first1=E. J. |last2=Nisbet |first2=E. G. |last3=Fisher |first3=R. |last4=Lowry |first4=D. |display-authors=1 |date=May 2011 |title=Global atmospheric methane: budget, changes and dangers |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |volume=369 |issue=1943 |pages=2058–2072 |bibcode=2011RSPTA.369.2058D |doi=10.1098/rsta.2010.0341 |pmid=21502176 |s2cid=8823692 |doi-access=}}</ref>
!'''Saunois et al. (2016)'''<ref name="Saunois_Bousquet_2016">{{cite journal |last1=Saunois |first1=M. |last2=Bousquet |first2=M. |last3=Poulter |first3=B. |display-authors=0 |date=December 12, 2016 |title=The Global Methane Budget 2000–2012 |url=https://essd.copernicus.org/articles/8/697/2016/essd-8-697-2016.html |journal=Earth System Science Data |language=en |volume=8 |issue=2 |pages=697–751 |bibcode=2016ESSD....8..697S |doi=10.5194/essd-8-697-2016 |issn=1866-3508 |access-date=28 August 2020 |doi-access=free|hdl=1721.1/108811 |hdl-access=free }}</ref>
!'''Saunois et al. (2020)'''<ref name="Saunois_2020">{{cite journal |last1=Saunois |first1=M. |last2=Stavert |first2=A.R. |last3=Poulter |first3=B. |display-authors=0 |date=July 15, 2020 |title=The Global Methane Budget 2000–2017 |url=https://essd.copernicus.org/articles/12/1561/2020/ |journal=Earth System Science Data (ESSD) |language=en |volume=12 |issue=3 |pages=1561–1623 |bibcode=2020ESSD...12.1561S |doi=10.5194/essd-12-1561-2020 |issn=1866-3508 |access-date=28 August 2020 |doi-access=free}}</ref>
|-
!Base year:
!1980s
!–
!1992
!–
!–
!2003–2012
!2008-2017
|-
! colspan="8" |Natural sources
|-
| class="table-rh" |[[Earth:Wetland|Wetlands]]
|115
|237
|225<ref name="table4.2c" group="nb">Rice included under wetlands.</ref>
|145
|{{val|147|15}}
|167 (127–202)
|181 (159-200)
|-
| class="table-rh" |[[Biology:Termite|Termites]]
|20
|–
|20
|20
|{{Val|23|4}}
| rowspan="3" |64 (21–132)
| rowspan="3" |37 (21–50)
|-
| class="table-rh" |[[Earth:Ocean|Ocean]]
|10
|–
|15
|15
|{{Val|19|6}}
|-
| class="table-rh" |[[Chemistry:Hydrate|Hydrates]]
|5
|–
|10
|–
|–
|-
! colspan="8" |Anthropogenic sources
|-
| class="table-rh" |Energy
|75
|97
|110
|89
|{{Val|110|13}}
|105 (77–133)
|111 (81-131)
|-
| class="table-rh" |Landfills
|40
|35
|40
|73
|{{Val|55|11}}<ref name="table1a" group="nb">Landfills total includes domestic sewage and animal waste.</ref>
| rowspan="4" |188 (115-243)
| rowspan="4" |217 (207-240)
|-
| class="table-rh" |[[Biology:Ruminant|Ruminants]] (livestock)
|80
|90<ref name="table4.2b" group="nb">Waste treatment included under ruminants.</ref>
|115
|93
|
|-
| class="table-rh" |Waste treatment
|–
|<ref name="table4.2b" group="nb" />
|25
|–
|<ref name="table1a" group="nb" />
|-
| class="table-rh" |Rice agriculture
|100
|88
|<ref name="table4.2c" group="nb" />
|–
|{{Val|31|5}}
|-
| class="table-rh" |Biomass burning
|55
|40
|40
|–
|{{Val|50|8}}
| rowspan="2" |34 (15–53)
| rowspan="2" |30 (22-36)
|-
| class="table-rh" |Other
|–
|–
|–
|20
|{{Val|90|14}}<ref name="table1b" group="nb">Contains a small amount of natural emissions from wild ruminants</ref>
|-
! colspan="8" |Sinks
|-
| class="table-rh" |[[Chemistry:Soil|Soils]]
|10
|
|30
|40
|{{Val|21|3}}
|33 (28–38)
|38 (27-45)
|-
| class="table-rh" |[[Earth:Troposphere|Tropospheric]] OH
|450
|489
|510
|
|{{Val|448|1}}
| rowspan="2" |515
| rowspan="2" |518 (474–532)
|-
| class="table-rh" |[[Earth:Stratosphere|Stratospheric]] loss
|
|46
|40
|
|{{Val|37|1}}
|-
! colspan="8" |Source versus sink imbalance
|-
| class="table-rh" |Total source
|500
|587
|600
|
|{{Val|525|8}}
|558 (540–568)
|576 (550-594)
|-
| class="table-rh" |Total sink
|460
|535
|580
|
|506
|548
|556 (501–574)
|}
{{clear left}}

== National reduction policies ==
[[File:Abatement potential of policy measures, 2021.jpg|thumb|An International Energy Agency graphic showing the potential of various emission reduction policies for addressing global methane emissions.]]
[[File:Methane emissions projections.png|thumb|upright=1.2|Global anthropogenic methane emissions from historical inventories and future [[Earth:Shared Socioeconomic Pathways|Shared Socioeconomic Pathways]] (SSP) projections.<ref name="methanebudget"/>]]

China implemented regulations requiring coal plants to either capture methane emissions or convert methane into {{CO2}} in 2010.  According to a Nature Communications paper published in January 2019, methane emissions instead increased 50 percent between 2000 and 2015.<ref>{{cite news |last1=Brooks Hays |title=Regulations haven't slowed China's growing methane emissions |url=https://www.upi.com/Science_News/2019/01/29/Regulations-havent-slowed-Chinas-growing-methane-emissions/2581548781889/ |access-date=31 January 2019 |work=UPI |date=29 January 2019 |quote=China's methane emissions increased 50 percent between 2000 and 2015}}</ref><ref>{{Cite journal|title=China's coal mine methane regulations have not curbed growing emissions|first1=Scot M.|last1=Miller|first2=Anna M.|last2=Michalak|first3=Robert G.|last3=Detmers|first4=Otto P.|last4=Hasekamp|first5=Lori M. P.|last5=Bruhwiler|first6=Stefan|last6=Schwietzke|date=January 29, 2019|journal=Nature Communications|volume=10|issue=1|pages=303|doi=10.1038/s41467-018-07891-7|pmid=30696820|pmc=6351523|bibcode=2019NatCo..10..303M}}</ref>

In March 2020, Exxon called for stricter methane regulations, which would include detection and repair of [[Chemistry:Methane leak|methane leak]]s, minimization of venting and releases of unburned methane, and reporting requirements for companies.<ref>{{Cite web|url=https://thehill.com/changing-america/sustainability/energy/485670-exxon-calls-for-tighter-regulations-of-methane|title=Exxon calls for tighter regulations of methane|last=Guzman|first=Joseph|date=2020-03-03|website=TheHill|language=en|access-date=2020-03-04}}</ref>  However, in August 2020, the U.S. Environmental Protection Agency rescinded a prior tightening of methane emission rules for the U.S. oil and gas industry.<ref>{{Cite web |url=https://www.forbes.com/sites/alisondurkee/2020/08/10/epa-reportedly-set-to-rescind-obama-era-methane-rules-as-white-house-speeds-environmental-rollbacks-ahead-of-election/#53f0610543fb |title=EPA Rescinds Obama-Era Methane Rules As White House Speeds Environmental Rollbacks Ahead Of Election |author=Alison Durkee |work=Forbes |date=August 10, 2020}}</ref><ref>{{Cite web |url=https://www.cnbc.com/2019/08/29/trump-to-roll-back-methane-climate-change-regulations.html |title=Critics rail against Trump's methane proposal as an 'unconscionable assault on environment' |author=Emma Newburger |publisher=CNBC |date=August 29, 2020}}</ref>

[[File:Methane emissions for 2017 by region, source category, and latitude.jpg|thumb|upright=1.2|Methane emissions for 2017 by region, source category, and latitude.<ref>{{cite journal |last1=Jackson |first1=R B |last2=Saunois |first2=M |last3=Bousquet |first3=P |last4=Canadell |first4=J G |last5=Poulter |first5=B |last6=Stavert |first6=A R |last7=Bergamaschi |first7=P |last8=Niwa |first8=Y |last9=Segers |first9=A |last10=Tsuruta |first10=A |title=Increasing anthropogenic methane emissions arise equally from agricultural and fossil fuel sources |journal=Environmental Research Letters |date=14 July 2020 |volume=15 |issue=7 |pages=071002 |doi=10.1088/1748-9326/ab9ed2 |bibcode=2020ERL....15g1002J |issn=1748-9326|doi-access=free }}</ref>]]

== Approaches to reduce emissions ==

=== Natural gas industries ===
About 40% of methane emissions from the fossil fuel industry could be "eliminated at no net cost for firms", according to the [[Organization:International Energy Agency|International Energy Agency]] (IEA) by using existing technologies.<ref name="economist_2021" /> Forty percent represents 9% of all human methane emissions.<ref name="economist_2021" /> 

To reduce emissions from the natural gas industries, the EPA developed the Natural Gas STAR Program, also known as Gas STAR.<ref name="EPA_2006" />

The Coalbed Methane Outreach Program (CMOP) helps and encourages the mining industry to find ways to use or sell [[Chemistry:Coalbed methane|methane]] that would otherwise be released from the coal mine into the atmosphere.<ref name="EPA_2006" />

In 2023, the European Union agreed to legislation that will require fossil fuel companies to monitor and report methane leaks and to repair them within a short time period. The law also compels remediation of methane venting and [[Chemistry:Routine flaring|methane flaring]]. The United States and China stated that they will include methane reduction targets in their next climate plans but have not enacted rules that would compel monitoring, reporting or repair of methane leaks.<ref>The Guardian, 15 Nov. 2023 [ https://www.theguardian.com/environment/2023/nov/15/eu-agrees-law-to-curb-methane-emissions-fossil-fuel-industry "EU Agrees Law to Curb Methane Emissions from Fossil Fuel Industry: Rules Would Require Firms to Report Emissions, Find and Fix leaks, and Limit Wasteful Venting and Flaring] </ref>

=== Livestock ===
In order to counteract the amount of methane that ruminants give off, a type of drug called monensin (marketed as rumensin) has been developed. This drug is classified as an [[Physics:Ionophore|ionophore]], which is an antibiotic that is naturally produced by a harmless bacteria strain. This drug not only improves feed efficiency but also reduces the amount of methane gas emitted from the animal and its manure.<ref name="Rumensin_2010">{{cite web |title=Use of Rumensin in Dairy Diets |date=August 21, 2012 |website=eXtension |first1=Mike |last1=Hutjens |url=http://www.extension.org/pages/Use_of_Rumensin_in_Dairy_Diets |access-date=February 27, 2011 |archive-date=July 9, 2010 |archive-url=https://web.archive.org/web/20100709202232/http://www.extension.org/pages/Use_of_Rumensin_in_Dairy_Diets |url-status=dead }}</ref>

In addition to medicine, specific [[Earth:Manure management|manure management]] techniques have been developed to counteract emissions from livestock manure. Educational resources have begun to be provided for small farms. Management techniques include daily pickup and storage of manure in a completely closed off storage facility that will prevent runoff from making it into bodies of water. The manure can then be kept in storage until it is either reused for fertilizer or taken away and stored in an offsite compost. Nutrient levels of various animal manures are provided for optimal use as compost for gardens and agriculture.<ref name="Bradley">{{cite web |last1=Bradley |first1=Athena Lee |publisher=Northeast Recycling Council, Inc |date=June 2008 |title=Manure Management for Small and Hobby Farms |url=http://www.nerc.org/documents/manure_management/manure_management_handbook.pdf |access-date=2016-12-31}}</ref>

=== Crops and soils ===
In order to reduce effects on methane oxidation in soil, several steps can be taken. Controlling the usage of nitrogen enhancing fertilizer and reducing the amount of nitrogen pollution into the air can both lower inhibition of methane oxidation. Additionally, using drier growing conditions for crops such as rice and selecting strains of crops that produce more food per unit area can reduce the amount of land with ideal conditions for methanogenesis. Careful selection of areas of land conversion (for example, plowing down forests to create agricultural fields) can also reduce the destruction of major areas of methane oxidation.{{citation needed|date=March 2023}}

=== Landfills ===
To counteract methane emissions from landfills, on March 12, 1996, the EPA (Environmental Protection Agency) added the "Landfill Rule" to the Clean Air Act. This rule requires large landfills that have ever accepted municipal solid waste, have been used as of November 8, 1987, can hold at least 2.5&nbsp;million metric tons of waste with a volume greater than 2.5&nbsp;million cubic meters, and/or have nonmethane organic compound (NMOC) emissions of at least 50 metric tons per year to collect and combust emitted [[Chemistry:Landfill gas|landfill gas]].<ref name="Landfill">{{cite web |title=Landfill Methane Energy Recovery |publisher=Power Partners |date=December 11, 2009 |url=http://www.uspowerpartners.org/Topics/SECTION6Topic-LandfillMethane.htm |access-date=2016-12-31 |url-status=dead |archive-url=https://web.archive.org/web/20150929005545/http://www.uspowerpartners.org/Topics/SECTION6Topic-LandfillMethane.htm |archive-date=September 29, 2015 }}</ref> This set of requirements excludes 96% of the landfills in the USA. While the direct result of this is landfills reducing emission of non-methane compounds that form smog, the indirect result is reduction of methane emissions as well.

In an attempt to absorb the methane that is already being produced from landfills, experiments in which nutrients were added to the soil to allow [[Biology:Methanotroph|methanotroph]]s to thrive have been conducted. These nutrient supplemented landfills have been shown to act as a small scale methane sink, allowing the abundance of methanotrophs to sponge the methane from the air to use as energy, effectively reducing the landfill's emissions.<ref>{{cite journal |last1=Lizik |first1=William |last2=Im |first2=Jeongdae |last3=Semrau |first3=Jeremy D. |last4=Barcelona |first4=Michael J. |title=A field trial of nutrient stimulation of methanotrophs to reduce greenhouse gas emissions from landfill cover soils |journal=Journal of the Air & Waste Management Association |volume=63 |issue=3 |pages=300–309 |doi=10.1080/10962247.2012.755137 |pmid=23556240 |year=2013|s2cid=20450110 |doi-access=}}</ref>

==See also==

*China United Coalbed Methane
*[[Earth:Climate change feedback|Climate change feedback]]
*[[Earth:Greenhouse gas emissions|Greenhouse gas emissions]]
*[[Chemistry:Greenhouse Gases Observing Satellite-2|Greenhouse Gases Observing Satellite-2]]
*[[Organization:Global Methane Initiative|Global Methane Initiative]]
*[[Chemistry:Fugitive gas emissions|Fugitive gas emissions]]

==Notes==
{{Reflist|30em|group=nb}}

==References==
{{reflist}}

==External links==
* {{cite web | title=Main sources of methane emissions | website=What's Your Impact | date=2014-03-14 | url=https://whatsyourimpact.org/greenhouse-gases/methane-emissions | ref={{sfnref | What's Your Impact | 2014}} | access-date=2018-03-06}}
* {{cite web | title=Greenhouse Gas Emissions - Methane Emissions | website=EIA | date=2011-03-31 | url=https://www.eia.gov/environment/emissions/ghg_report/ghg_methane.php | ref={{sfnref | EIA | 2011}} | access-date=2018-03-06}}

[[Category:Methane]]

{{Sourceattribution|Methane emissions}}