Methane (CH4)

 Methane is the simplest hydrocarbon with the chemical formula CH₄. Methane is an odourless and colourless gas and is sometimes called swamp gas due to the fact that it is formed during decomposition of organic matter in anaerobic environments¹. Methane is a greenhouse gas. In order to compare the effect of different greenhouse gases, emissions are converted into carbon dioxide equivalents².

Uses

Methane is the main component of natural gas and biogas³, both used as fuels and for energy production. Methane is also used for detection of radiation, as reference gas in combustion processes, within chemical synthesis and as carrier of carbon within metallurgy and nuclear physics⁴.

Sources and transportation pathways

There are both natural and anthropogenic sources of methane. The concentration of methane in the atmosphere has more than doubled in a hundred years. The natural emissions are of about the same magnitude as those caused by humans. During the last 650 000 years the concentration of methane has fluctuated between 400 and 700 ppb (parts per billion), but during the 2000^th century the concentration has increased to over 1700 ppb. The largest emission sources of methane in Sweden are livestock, i.e. the digestion of cattle, and landfills⁵. Globally, the largest emission sources are rice farming, emissions from coal mines and natural gas, combustion of waste, wastewater treatment and livestock.

The most important transportation pathway is by air.

Effects on environment and health

Methane is a greenhouse gas that contributes to the increased greenhouse gas effect⁶. The increased greenhouse gas effect results in an increase of the average temperature on earth, which for example leads to climate change and rising of the sea level^7,8.

Exposure to high levels of methane may cause suffocation as methane displaces the oxygen from the air⁹. Methane is a highly explosive and flammable gas¹⁰.

International agreements and regulations

Methane is regulated by the UN Framework Convention on Climate Change (UNFCCC) and the EU MMR regulation (525/2013/EU). The UN Protocol on PRTRs and the EU E-PRTR regulation (166/2006/EG) regulate how data on methane emissions is made available.

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¹ https://rib.msb.se/Portal/Template/Pages/Kemi/Substance.aspx?id=392&q=metan&p=1
² http://www.naturvardsverket.se/Sa-mar-miljon/Statistik-A-O/Vaxthusgaser-konsumtionsbaserade-utslapp-fran-exporterande-foretag/Koldioxidekvivalenter/
³ http://www.naturvardsverket.se/Sa-mar-miljon/Klimat-och-luft/Klimat/Darfor-blir-det-varmare/Andra-vaxthusgaser/
⁴ https://rib.msb.se/Portal/Template/Pages/Kemi/Substance.aspx?id=392&q=metan&p=1
⁵ https://www.smhi.se/kunskapsbanken/klimat/kortlivade-klimatpaverkande-luftfororeningar-slcp/metan-1.99802
⁶ http://www.naturvardsverket.se/Sa-mar-miljon/Klimat-och-luft/Klimat/Darfor-blir-det-varmare/Andra-vaxthusgaser/
⁷ http://www.ipcc.ch/pdf/assessment-report/ar5/syr/AR5_SYR_FINAL_SPM.pdf
⁸ http://www.smhi.se/kunskapsbanken/klimat/vaxthuseffekten-1.3844
⁹ https://rib.msb.se/portal/template/pages/kemi/Substance.aspx?id=392&q=metan&p=1
¹⁰ https://echa.europa.eu/information-on-chemicals/cl-inventory-database/-/discli/details/107761