View source for Coal

{{short description|Combustible sedimentary rock composed primarily of carbon}}
{{other uses}}
{{pp-move}}
{{pp-semi-indef}}
{{Use dmy dates|date=December 2016}}
{{Infobox rock
|name=Coal
|type=Sedimentary
|image=Bituminous Coal.JPG
|image_caption=[[Bituminous coal]], the most common [[coal grade]]
|image_size=258px
|composition=[[carbon]]
|composition_secondary={{plainlist|
* [[hydrogen]]
* [[sulfur]]
* [[oxygen]]
* [[nitrogen]]}}
}}
{{Coal sidebar|state=collapsed}}
'''Coal''' is a [[combustible]] black or brownish-black [[sedimentary rock]], formed as [[stratum|rock strata]] called [[coal seams]]. Coal is mostly [[carbon]] with variable amounts of other [[Chemical element|elements]], chiefly [[hydrogen]], [[sulfur]], [[oxygen]], and [[nitrogen]].<ref>{{cite web|last=Blander|first=M|title=Calculations of the Influence of Additives on Coal Combustion Deposits|url=http://www.anl.gov/PCS/acsfuel/preprint%20archive/Files/Volumes/Vol34-2.pdf|publisher=Argonne National Laboratory|access-date=17 December 2011|page=315|url-status=dead|archive-url=https://web.archive.org/web/20100528174436/http://www.anl.gov/PCS/acsfuel/preprint%20archive/Files/Volumes/Vol34-2.pdf|archive-date=28 May 2010}}</ref>
Coal is a type of [[fossil fuel]], formed when dead [[plant matter]] decays into [[peat]] which is converted into coal by the heat and pressure of deep burial over millions of years.<ref name="EIA Coal Explained">{{cite web | url=https://www.eia.gov/energyexplained/index.cfm?page=coal_home | title=Coal Explained | publisher=[[US Energy Information Administration]] | work=Energy Explained | date=21 April 2017 | access-date=13 November 2017 | url-status=live | archive-url=https://web.archive.org/web/20171208115825/https://www.eia.gov/energyexplained/index.cfm?page=coal_home | archive-date=8 December 2017}}</ref> Vast deposits of coal originate in former [[wetland]]s called [[coal forest]]s that covered much of the Earth's tropical land areas during the late [[Carboniferous]] ([[Pennsylvanian (geology)|Pennsylvanian]]) and [[Permian]] times.<ref name=ClealThomas2005>{{cite journal | last1 = Cleal | first1 = C. J. | last2 = Thomas | first2 = B. A. | year = 2005 | title = Palaeozoic tropical rainforests and their effect on global climates: is the past the key to the present? | journal = Geobiology | volume = 3 | issue = 1 | pages = 13–31 | doi = 10.1111/j.1472-4669.2005.00043.x | bibcode = 2005Gbio....3...13C | s2cid = 129219852  |issn = 1472-4669 }}</ref><ref name="SahneyBentonFerry2010RainforestCollapse">{{cite journal |author=Sahney, S. |author2=Benton, M.J. |author3=Falcon-Lang, H.J. | year=2010 | title= Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica | journal=Geology | volume = 38 | pages = 1079–1082 | doi=10.1130/G31182.1 | issue=12 | bibcode=2010Geo....38.1079S}}</ref>
Coal is used primarily as a fuel. While coal has been known and used for thousands of years, its usage was limited until the [[Industrial Revolution]]. With the invention of the [[steam engine]], coal consumption increased.<ref>{{Cite web |last=Wilde |first=Robert |date=2019-06-30 |title=How the Demand for Coal Impacted the Industrial Revolution |url=https://www.thoughtco.com/coal-in-the-industrial-revolution-1221634 |access-date=2024-05-02 |website=ThoughtCo |language=en}}</ref> In 2020, coal supplied about a quarter of the world's [[primary energy]] and over a third of its [[Electricity generation|electricity]].<ref name=IEAstats2>{{cite web | url=https://www.iea.org/statistics/?country=WORLD&year=2016&category=Key%20indicators&indicator=ElecGenByFuel&mode=chart&categoryBrowse=false&dataTable=ELECTRICITYANDHEAT&showDataTable=false | title=Global energy data | publisher=[[International Energy Agency]] }}</ref> Some [[iron]] and [[steel]]-making and other industrial processes burn coal.
The extraction and burning of coal [[Environmental impact of the coal industry|damages the environment]], causing premature death and illness,<ref name="Heal">{{cite web |date=December 2018 |title=Lignite coal – health effects and recommendations from the health sector |url=https://www.env-health.org/wp-content/uploads/2018/12/HEAL-Lignite-Briefing-en_web.pdf |url-status=dead |archive-url=https://web.archive.org/web/20181211010345/https://www.env-health.org/wp-content/uploads/2018/12/HEAL-Lignite-Briefing-en_web.pdf |archive-date=11 December 2018 |access-date=12 February 2024 |publisher=Health and Environment Alliance}}</ref> and it is the largest [[wikt:anthropogenic|anthropogenic]] source of [[carbon dioxide]] contributing to [[climate change]]. Fourteen billion tonnes of carbon dioxide were emitted by burning coal in 2020,<ref name="cebf">{{Cite journal|title={{CO2}} emissions by fuel|url=https://ourworldindata.org/emissions-by-fuel|access-date=2021-01-22|journal=Our World in Data|date=11 May 2020|last1=Ritchie|first1=Hannah|author1-link=Hannah Ritchie |last2=Roser|first2=Max|author2-link=Max Roser }}</ref> which is 40% of total fossil fuel emissions<ref name=phys2018/> and over 25% of total global [[greenhouse gas emissions]].<ref>{{Cite web|url=https://www.resilience.org/stories/2020-01-24/dethroning-king-coal-how-a-once-dominant-fuel-source-is-falling-rapidly-from-favour/|title=Dethroning King Coal – How a Once Dominant Fuel Source is Falling Rapidly from Favour|date=2020-01-24|website=Resilience|language=en-US|access-date=2020-02-08}}</ref> As part of worldwide [[energy transition]], many countries have [[Coal phase-out|reduced or eliminated their use of coal power]].<ref>{{Cite web|date=2020-08-03|title=Analysis: The global coal fleet shrank for first time on record in 2020|url=https://www.carbonbrief.org/analysis-the-global-coal-fleet-shrank-for-first-time-on-record-in-2020|access-date=2021-11-09|website=Carbon Brief|language=en}}</ref><ref>{{Cite web|last=Simon|first=Frédéric|date=2020-04-21|title=Sweden adds name to growing list of coal-free states in Europe|url=https://www.euractiv.com/section/energy/news/sweden-adds-name-to-growing-list-of-coal-free-states-in-europe/|access-date=2021-11-09|website=www.euractiv.com|language=en-GB}}</ref> The [[United Nations Secretary General]] asked governments to stop building new [[coal plants]] by 2020.<ref>{{cite news |title=Tax carbon, not people: UN chief issues climate plea from Pacific 'frontline' |url=https://www.theguardian.com/environment/2019/may/15/tax-carbon-not-people-un-chief-issues-climate-plea-from-pacific-frontline |work=[[The Guardian]] |date=15 May 2019}}</ref>
Global coal use was 8.3 billion tonnes in 2022,<ref name="record levels">{{cite web|author1=Anmar Frangoul
|title=IEA says coal use hit an all-time high last year — and global demand will persist near record levels|url=https://www.cnbc.com/2023/07/27/coal-consumption-hit-an-all-time-high-in-2022-iea-says.html#:~:text=According%20to%20the%20IEA%2C%20coal,a%20record%20high%20last%20year.&text=Coal%20consumption%20increased%20by%203.3,International%20Energy%20Agency%20said%20Thursday.|access-date=2023-09-10|website=CNBC|date=27 July 2023 |language=en}}</ref> and is set to remain at record levels in 2023.<ref name="iea">{{Cite web|last=Frangoul|first=Frangoul|title=Global coal demand set to remain at record levels in 2023|url=https://www.iea.org/news/global-coal-demand-set-to-remain-at-record-levels-in-2023|access-date=2023-09-12|website=iea|date=27 July 2023 |language=en}}</ref> To meet the [[Paris Agreement]] target of keeping [[global warming]] below {{convert|2|C-change|F-change|1}} [[Coal phase-out|coal use needs to halve]] from 2020 to 2030,<ref>{{Cite web|url=https://www.carbonbrief.org/analysis-why-coal-use-must-plummet-this-decade-to-keep-global-warming-below-1-5c|title=Analysis: Why coal use must plummet this decade to keep global warming below 1.5C|date=2020-02-06|website=Carbon Brief|language=en|access-date=2020-02-08}}</ref> and "phasing down" coal was agreed upon in the [[Glasgow Climate Pact]].
The largest consumer and importer of coal in 2020 was [[Coal in China|China]], which accounts for almost half the world's annual coal production, followed by [[Coal in India|India]] with about a tenth. [[Energy in Indonesia#Coal|Indonesia]] and [[Coal in Australia|Australia]] export the most, followed by [[Coal in Russia|Russia]].<ref>{{Cite web|title=Exports – Coal Information: Overview – Analysis|url=https://www.iea.org/reports/coal-information-overview/exports|access-date=2022-01-20|website=IEA|language=en-GB}}</ref><ref name="Overland-2023">{{Cite journal |last1=Overland |first1=Indra |last2=Loginova |first2=Julia |date=2023-08-01 |title=The Russian coal industry in an uncertain world: Finally pivoting to Asia? |journal=Energy Research & Social Science |volume=102 |pages=103150 |doi=10.1016/j.erss.2023.103150 |issn=2214-6296|doi-access=free |bibcode=2023ERSS..10203150O }}</ref>
==Etymology==
The word originally took the form ''col'' in [[Old English]], from reconstructed [[Proto-Germanic]] *''kula''(''n''), from [[Proto-Indo-European]] root *''g''(''e'')''u-lo-'' "live coal".<ref name=etym>{{OEtymD|coal}}</ref> [[Germanic languages|Germanic]] cognates include the [[Old Frisian]] {{lang|ofs|kole}}, [[Middle Dutch]] {{lang|dum|cole}}, [[Dutch language|Dutch]] {{lang|nl|kool}}, [[Old High German]] {{lang|goh|chol}}, [[German language|German]] {{lang|de|Kohle}} and [[Old Norse]] {{lang|non|kol}}. [[Irish language|Irish]] {{lang|ga|gual}} is also a cognate via the Indo-European root.<ref name=etym/>
==Formation of coal==
[[File:Struktura chemiczna węgla kamiennego.svg| thumb|Example chemical structure of coal]]
The conversion of dead vegetation into coal is called [[wikt:coalification|coalification]]. At various times in the geologic past, the Earth had dense forests<ref>{{cite web|title=How Coal Is Formed |url=http://www.fe.doe.gov/education/energylessons/coal/gen_howformed.html|url-status=live|archive-url=https://web.archive.org/web/20170118113211/http://www.fe.doe.gov/education/energylessons/coal/gen_howformed.html|archive-date=18 January 2017}}</ref> in low-lying areas. In these wetlands, the process of coalification began when dead plant matter was protected from [[oxidation]], usually by mud or acidic water, and was converted into [[peat]]. The resulting [[peat bog]]s, which trapped immense amounts of carbon, were eventually deeply buried by sediments. Then, over millions of years, the heat and pressure of deep burial caused the loss of water, methane and carbon dioxide and increased the proportion of carbon.<ref name="BGS">{{cite web | url=https://www.bgs.ac.uk/downloads/start.cfm?id=1404 | title=Coal  | publisher=[[British Geological Survey]] | date=March 2010}}</ref> The grade of coal produced depended on the maximum pressure and temperature reached, with [[lignite]] (also called "brown coal") produced under relatively mild conditions, and [[sub-bituminous coal]], [[bituminous coal]], or [[anthracite|anthracite coal]] (also called "hard coal" or "black coal") produced in turn with increasing temperature and pressure.<ref name="EIA Coal Explained" /><ref>{{Cite book| url = https://books.google.com/books?id=_29tNNeQKeMC&pg=PA18| title = Paleobotany: The Biology and Evolution of Fossil Plants| isbn = 978-0-12-373972-8| author1 = Taylor, Thomas N| author2 = Taylor, Edith L| author3 = Krings, Michael| year = 2009| publisher = Academic Press| url-status = live| archive-url = https://web.archive.org/web/20160516231216/https://books.google.com/books?id=_29tNNeQKeMC&pg=PA18| archive-date = 16 May 2016}}</ref>
Of the factors involved in coalification, temperature is much more important than either pressure or time of burial.<ref>{{cite web |title=Heat, time, pressure, and coalification |url=http://www.uky.edu/KGS/coal/coal-heat-time-pressure.php |website=Kentucky Geological Survey |publisher=University of Kentucky |access-date=28 November 2020}}</ref> Subbituminous coal can form at temperatures as low as {{ convert|35 to 80|C||sp=us}} while anthracite requires a temperature of at least {{convert|180 to 245|C||sp=us}}.<ref>{{cite web |title=Burial temperatures from coal |url=http://www.uky.edu/KGS/coal/coal-burial-temperature.php |website=Kentucky Geological Survey |publisher=University of Kentucky |access-date=28 November 2020}}</ref>
Although coal is known from most geologic [[Period (geology)|periods]], 90% of all coal beds were deposited in the [[Carboniferous]] and [[Permian]] periods.<ref>{{cite book |last1=McGhee |first1=George R. |title=Carboniferous Giants and Mass Extinction: The Late Paleozoic Ice Age World |date=2018 |publisher=Columbia University Press |location=New York |isbn=9780231180979 |pages=98}}</ref> Paradoxically, this was during the [[Late Paleozoic icehouse]], a time of global [[Ice age|glaciation]]. However, the drop in global sea level accompanying the glaciation exposed [[continental shelf|continental shelves]] that had previously been submerged, and to these were added wide [[river delta]]s produced by increased [[erosion]] due to the drop in [[base level]]. These widespread areas of wetlands provided ideal conditions for coal formation.{{sfn|McGhee|2018|pp=88-92}} The rapid formation of coal ended with the [[Permian–Triassic extinction event#Coal Gap|coal gap]] in the [[Permian–Triassic extinction event]], where coal is rare.<ref name="Retallack1996">{{cite journal| last1=Retallack |first1=G. J.|last2= Veevers|first2=J. J.|last3= Morante|first3= R.|title=Global coal gap between Permian–Triassic extinctions and middle Triassic recovery of peat forming plants|journal=GSA Bulletin|volume=108|issue=2|pages=195–207|year=1996|doi = 10.1130/0016-7606(1996)108<0195:GCGBPT>2.3.CO;2|bibcode=1996GSAB..108..195R}}</ref>
Favorable geography alone does not explain the extensive Carboniferous coal beds.{{sfn|McGhee|2018|p=99}} Other factors contributing to rapid coal deposition were high [[oxygen]] levels, above 30%, that promoted intense [[wildfire]]s and formation of [[charcoal]] that was all but indigestible by decomposing organisms; high [[carbon dioxide]] levels that promoted plant growth; and the nature of Carboniferous forests, which included [[lycophyte]] trees whose [[determinate growth]] meant that carbon was not tied up in [[heartwood]] of living trees for long periods.{{sfn|McGhee|2018|pp=98-102}}
One theory suggested that about 360 million years ago, some plants evolved the ability to produce [[lignin]], a complex polymer that made their [[cellulose]] stems much harder and more woody. The ability to produce lignin led to the evolution of the first [[trees]]. But bacteria and fungi did not immediately evolve the ability to decompose lignin, so the wood did not fully decay but became buried under sediment, eventually turning into coal. About 300 million years ago, mushrooms and other fungi developed this ability, ending the main coal-formation period of earth's history.<ref>{{cite book |title=Unsettled: What Climate Science Tells Us, What It Doesn't, and Why It Matters |first=Steven E. |last=Koonin |location=Dallas |publisher=BenBella Books |date=2021 |isbn=9781953295248 |page=44}}</ref><ref>{{cite journal |last1=Floudas |first1=Dimitrios |last2=Binder |first2=Manfred |last3=Riley |first3=Robert |last4=Barry |first4=Kerrie |last5=Blanchette |first5=Robert A. |last6=Henrissat |first6=Bernard |last7=Martínez |first7=Angel T. |last8=Otillar |first8=Robert |last9=Spatafora |first9=Joseph W. |last10=Yadav |first10=Jagjit S. |last11=Aerts |first11=Andrea |last12=Benoit |first12=Isabelle |last13=Boyd |first13=Alex |last14=Carlson |first14=Alexis |last15=Copeland |first15=Alex |last16=Coutinho |first16=Pedro M. |last17=de Vries |first17=Ronald P. |last18=Ferreira |first18=Patricia |last19=Findley |first19=Keisha |last20=Foster |first20=Brian |last21=Gaskell |first21=Jill |last22=Glotzer |first22=Dylan |last23=Górecki |first23=Paweł |last24=Heitman |first24=Joseph |last25=Hesse |first25=Cedar |last26=Hori |first26=Chiaki |last27=Igarashi |first27=Kiyohiko |last28=Jurgens |first28=Joel A. |last29=Kallen |first29=Nathan |last30=Kersten |first30=Phil |last31=Kohler |first31=Annegret |last32=Kües |first32=Ursula |last33=Kumar |first33=T. K. Arun |last34=Kuo |first34=Alan |last35=LaButti |first35=Kurt |last36=Larrondo |first36=Luis F. |last37=Lindquist |first37=Erika |last38=Ling |first38=Albee |last39=Lombard |first39=Vincent |last40=Lucas |first40=Susan |last41=Lundell |first41=Taina |last42=Martin |first42=Rachael |last43=McLaughlin |first43=David J. |last44=Morgenstern |first44=Ingo |last45=Morin |first45=Emanuelle |last46=Murat |first46=Claude |last47=Nagy |first47=Laszlo G. |last48=Nolan |first48=Matt |last49=Ohm |first49=Robin A. |last50=Patyshakuliyeva |first50=Aleksandrina |last51=Rokas |first51=Antonis |last52=Ruiz-Dueñas |first52=Francisco J. |last53=Sabat |first53=Grzegorz |last54=Salamov |first54=Asaf |last55=Samejima |first55=Masahiro |last56=Schmutz |first56=Jeremy |last57=Slot |first57=Jason C. |last58=St. John |first58=Franz |last59=Stenlid |first59=Jan |last60=Sun |first60=Hui |last61=Sun |first61=Sheng |last62=Syed |first62=Khajamohiddin |last63=Tsang |first63=Adrian |last64=Wiebenga |first64=Ad |last65=Young |first65=Darcy |last66=Pisabarro |first66=Antonio |last67=Eastwood |first67=Daniel C. |last68=Martin |first68=Francis |last69=Cullen |first69=Dan |last70=Grigoriev |first70=Igor V. |last71=Hibbett |first71=David S. |title=The Paleozoic Origin of Enzymatic Lignin Decomposition Reconstructed from 31 Fungal Genomes |journal=Science |date=29 June 2012 |volume=336 |issue=6089 |pages=1715–1719 |doi=10.1126/science.1221748|pmid=22745431 |bibcode=2012Sci...336.1715F |hdl=10261/60626 |osti=1165864 |s2cid=37121590 |hdl-access=free }}</ref><ref>{{Cite web | url=https://www.scientificamerican.com/article/mushroom-evolution-breaks-down-lignin-slows-coal-formation |title = White Rot Fungi Slowed Coal Formation|website = [[Scientific American]]}}</ref> Although some authors pointed at some evidence of lignin degradation during the Carboniferous, and suggested that climatic and tectonic factors were a more plausible explanation,<ref>{{Cite journal|last1=Nelsen|first1=Matthew P.|last2=DiMichele|first2=William A.|last3=Peters|first3=Shanan E.|last4=Boyce|first4=C. Kevin|date=2016-01-19|title=Delayed fungal evolution did not cause the Paleozoic peak in coal production|journal=Proceedings of the National Academy of Sciences|language=en|volume=113|issue=9|pages=2442–2447|doi=10.1073/pnas.1517943113|pmid=26787881|pmc=4780611|bibcode=2016PNAS..113.2442N|issn=0027-8424|doi-access=free}}</ref> reconstruction of ancestral enzymes by phylogenetic analysis corroborated a hypothesis that lignin degrading enzymes appeared in fungi approximately 200 MYa.<ref>Ayuso-Fernandez I, Ruiz-Duenas FJ, Martinez AT: Evolutionary convergence in lignin-degrading enzymes. Proc Natl Acad Sci USA 2018, 115:6428-6433.</ref>
One likely tectonic factor was the [[Central Pangean Mountains]], an enormous range running along the equator that reached its greatest elevation near this time. Climate modeling suggests that the Central Pangean Mountains contributed to the deposition of vast quantities of coal in the late Carboniferous. The mountains created an area of year-round heavy precipitation, with no dry season typical of a [[monsoon]] climate. This is necessary for the preservation of peat in coal swamps.<ref>{{cite journal |last1=Otto-Bliesner |first1=Bette L. |author-link1=Bette Otto-Bliesner|title=Tropical mountains and coal formation: A climate model study of the Westphalian (306 MA) |journal=Geophysical Research Letters |date=15 September 1993 |volume=20 |issue=18 |pages=1947–1950 |doi=10.1029/93GL02235|bibcode=1993GeoRL..20.1947O }}</ref>
Coal is known from [[Precambrian]] strata, which predate land plants. This coal is presumed to have originated from residues of algae.<ref name="Tyler1957">{{Cite journal | doi = 10.1130/0016-7606(1957)68[1293:ACFPUH]2.0.CO;2 | bibcode = 1957GSAB...68.1293T | last1 = Tyler | first1 = S.A. | last2 = Barghoorn | first2 = E.S. | last3 = Barrett | first3 = L.P. | title = Anthracitic Coal from Precambrian Upper Huronian Black Shale of the Iron River District, Northern Michigan | journal = Geological Society of America Bulletin | volume = 68 | issue = 10 | page = 1293 | year = 1957 | issn = 0016-7606 }}</ref><ref name="Mancuso1981">{{Cite journal | doi = 10.2113/gsecongeo.76.4.951 | last1 = Mancuso | first1 = J.J. | last2 = Seavoy | first2 = R.E. | title = Precambrian coal or anthraxolite; a source for graphite in high-grade schists and gneisses | journal = Economic Geology | volume = 76 | issue = 4 | pages = 951–54 | year = 1981 | bibcode = 1981EcGeo..76..951M }}</ref>
Sometimes coal seams (also known as coal beds) are interbedded with other sediments in a [[cyclothem]]. Cyclothems are thought to have their origin in [[glacial cycle]]s that produced fluctuations in [[sea level]], which alternately exposed and then flooded large areas of continental shelf.<ref>Stanley, Steven M. ''Earth System History''. New York: W.H. Freeman and Company, 1999. {{ISBN|0-7167-2882-6}}  (p. 426)</ref>
===Chemistry of coalification===
The woody tissue of plants is composed mainly of cellulose, hemicellulose, and lignin. Modern peat is mostly lignin, with a content of cellulose and hemicellulose ranging from 5% to 40%. Various other organic compounds, such as waxes and nitrogen- and sulfur-containing compounds, are also present.<ref>{{cite book |last1=Andriesse |first1=J. P. |title=Nature and Management of Tropical Peat Soils |date=1988 |publisher=Food and Agriculture Organization of the United Nations |location=Rome |isbn=92-5-102657-2 |chapter=The Main Characteristics of Tropical Peats}}</ref> Lignin has a weight composition of about 54% carbon, 6% hydrogen, and 30% oxygen, while cellulose has a weight composition of about 44% carbon, 6% hydrogen, and 49% oxygen. Bituminous coal has a composition of about 84.4% carbon, 5.4% hydrogen, 6.7% oxygen, 1.7% nitrogen, and 1.8% sulfur, on a weight basis.<ref name=Perry>{{cite book |editor1-last=Robert Perry |editor2-last=Cecil Chilton |chapter=Chapter 9: Heat Generation, Transport, and Storage|first=William|last=Reid|title=Chemical Engineers' Handbook |date=1973 |edition=5}}</ref> The low oxygen content of coal shows that coalification removed most of the oxygen and much of the hydrogen a process called ''carbonization''.<ref>{{cite journal |last1=Ulbrich |first1=Markus |last2=Preßl |first2=Dieter |last3=Fendt |first3=Sebastian |last4=Gaderer |first4=Matthias |last5=Spliethoff |first5=Hartmut |title=Impact of HTC reaction conditions on the hydrochar properties and {{CO2}} gasification properties of spent grains |journal=Fuel Processing Technology |date=December 2017 |volume=167 |pages=663–669 |doi=10.1016/j.fuproc.2017.08.010}}</ref>
Carbonization proceeds primarily by [[Dehydration reaction|dehydration]], [[decarboxylation]], and demethanation. Dehydration removes water molecules from the maturing coal via reactions such as<ref name="hatcher-etal-1992">{{cite journal |last1=Hatcher |first1=Patrick G. |last2=Faulon |first2=Jean Loup |last3=Wenzel |first3=Kurt A. |last4=Cody |first4=George D. |title=A structural model for lignin-derived vitrinite from high-volatile bituminous coal (coalified wood) |journal=Energy & Fuels |date=November 1992 |volume=6 |issue=6 |pages=813–820 |doi=10.1021/ef00036a018}}</ref>
:2 R–OH → R–O–R + H<sub>2</sub>O
[[Decarboxylation]] removes carbon dioxide from the maturing coal:<ref name="hatcher-etal-1992"/>
:RCOOH → RH + CO<sub>2</sub>
while demethanation proceeds by reaction such as
:2 R-CH<sub>3</sub> → R-CH<sub>2</sub>-R + CH<sub>4</sub>
:R-CH<sub>2</sub>-CH<sub>2</sub>-CH<sub>2</sub>-R → R-CH=CH-R + CH<sub>4</sub>
In these formulas, R represents the remainder of a cellulose or lignin molecule to which the reacting groups are attached.
Dehydration and decarboxylation take place early in coalification, while demethanation begins only after the coal has already reached bituminous rank.<ref>{{cite web |title=Coal Types, Formation and Methods of Mining |url=http://epcamr.org/home/content/reference-materials/coal-types-formation-and-methods-of-mining/ |publisher=Eastern Pennsylvania Coalition for Abandoned Mine Reclamation |access-date=29 November 2020}}</ref> The effect of decarboxylation is to reduce the percentage of oxygen, while demethanation reduces the percentage of hydrogen. Dehydration does both, and (together with demethanation) reduces the saturation of the carbon backbone (increasing the number of double bonds between carbon).
As carbonization proceeds, [[aliphatic compound]]s convert to [[aromatic compound]]s. Similarly, aromatic rings fuse into [[polyaromatic]] compounds (linked rings of carbon atoms).<ref>{{cite journal |last1=Ibarra |first1=JoséV. |last2=Muñoz |first2=Edgar |last3=Moliner |first3=Rafael |title=FTIR study of the evolution of coal structure during the coalification process |journal=Organic Geochemistry |date=June 1996 |volume=24 |issue=6–7 |pages=725–735 |doi=10.1016/0146-6380(96)00063-0|bibcode=1996OrGeo..24..725I }}</ref> The structure increasingly resembles [[graphene]], the structural element of graphite.
Chemical changes are accompanied by physical changes, such as decrease in average pore size.<ref>{{cite journal |last1=Li |first1=Yong |last2=Zhang |first2=Cheng |last3=Tang |first3=Dazhen |last4=Gan |first4=Quan |last5=Niu |first5=Xinlei |last6=Wang |first6=Kai |last7=Shen |first7=Ruiyang |title=Coal pore size distributions controlled by the coalification process: An experimental study of coals from the Junggar, Ordos and Qinshui basins in China |journal=Fuel |date=October 2017 |volume=206 |pages=352–363 |doi=10.1016/j.fuel.2017.06.028|bibcode=2017Fuel..206..352L }}</ref>
===Macerals===
The macerals are coalified plant parts that retain the morphology and some properties of the original plant. In many coals, individual macerals can be identified visually. Some macerals include:<ref name= KO/>
* vitrinite, derived from woody parts
* lipinite, derived from spores and algae
* inertite, derived from woody parts that had been burnt in prehistoric times
* huminite, a precursor to vitrinite.
In coalification huminite is replaced by vitreous (shiny) ''vitrinite''.<ref>{{cite web |title=Sub-Bituminous Coal |url=http://www.uky.edu/KGS/coal/coal-sub.php |website=Kentucky Geological Survey |publisher=University of Kentucky |access-date=29 November 2020}}</ref> Maturation of bituminous coal is characterized by ''bitumenization'', in which part of the coal is converted to [[bitumen]], a hydrocarbon-rich gel.<ref>{{cite web |title=Bituminous Coal |url=http://www.uky.edu/KGS/coal/coal-bituminous.php |website=Kentucky Geological Survey |publisher=University of Kentucky |access-date=29 November 2020}}</ref> Maturation to anthracite is characterized by ''debitumenization'' (from demethanation) and the increasing tendency of the anthracite to break with a [[conchoidal fracture]], similar to the way thick glass breaks.<ref>{{cite web |title=Anthracitic Coal |url=http://www.uky.edu/KGS/coal/coal-anthracite.php |website=Kentucky Geological Survey |publisher=University of Kentucky |access-date=29 November 2020}}</ref>
{{anchor|Ranks}}
===Types===
[[File:Sydney Mines Point Aconi Seam 038.JPG|thumb|Coastal exposure of the Point Aconi Seam in [[Nova Scotia]]]]
[[File:Coal Rank USGS.png|thumb|upright=1.35|Coal ranking system used by the [[United States Geological Survey]]]]
As geological processes apply [[pressure]] to dead [[biotic material]] over time, under suitable conditions, its [[metamorphic grade]] or rank increases successively into:
* [[Peat]], a precursor of coal
* [[Lignite]], or brown coal, the lowest rank of coal, most harmful to health when burned,<ref name=Heal/> used almost exclusively as fuel for electric power generation
* [[Sub-bituminous coal]], whose properties range between those of lignite and those of bituminous coal, is used primarily as fuel for steam-electric power generation.
* [[Bituminous coal]], a dense sedimentary rock, usually black, but sometimes dark brown, often with well-defined bands of bright and dull material. It is used primarily as fuel in steam-electric power generation and to make [[coke (fuel)|coke]]. Known as steam coal in the UK, and historically used to raise steam in steam locomotives and ships
* [[Anthracite|Anthracite coal]], the highest rank of coal, is a harder, glossy black coal used primarily for residential and commercial [[space heating]].
* [[Graphite]], a difficult to ignite coal which is mostly used in pencils, or powdered for [[lubrication]].
* [[Cannel coal]] (sometimes called "candle coal"), a variety of fine-grained, high-rank coal with significant hydrogen content, which consists primarily of [[liptinite]]. It is related to boghead coal.
There are several international standards for coal.<ref>{{cite web |title=Standards catalogue 73.040 – Coals |url=https://www.iso.org/ics/73.040/x/ |publisher=[[ISO]]}}</ref> The classification of coal is generally based on the content of [[coal volatiles|volatiles]]. However the most important distinction is between thermal coal (also known as steam coal), which is burnt to generate electricity via steam; and [[metallurgical coal]] (also known as coking coal), which is burnt at high temperature to make [[steel]].
[[Hilt's law]] is a geological observation that (within a small area) the deeper the coal is found, the higher its rank (or grade). It applies if the thermal gradient is entirely vertical; however, [[metamorphism]] may cause lateral changes of rank, irrespective of depth. For example, some of the coal seams of the [[Madrid, New Mexico]] coal field were partially converted to anthracite by [[contact metamorphism]] from an igneous [[Sill (geology)|sill]] while the remainder of the seams remained as bituminous coal.<ref>{{cite journal |last1=Darton |first1=Horatio Nelson |title=Guidebook of the Western United States: Part C - The Santa Fe Route, with a side trip to Grand Canyon of the Colorado |journal=U.S. Geological Survey Bulletin |date=1916 |volume=613 |page=81 |doi=10.3133/b613|bibcode=1916usgs.rept....2D |hdl=2027/hvd.32044055492656 |hdl-access=free }}</ref>
==History==
{{Further|History of coal mining}}
[[File:Tiangong Kaiwu Coal Mining.gif|thumb|upright|Chinese coal miners in an illustration of the ''Tiangong Kaiwu'' encyclopedia, published in 1637]]
The earliest recognized use is from the [[Shenyang]] area of China where by 4000 BC [[Neolithic]] inhabitants had begun carving ornaments from black lignite.<ref>Golas, Peter J and Needham, Joseph (1999) ''Science and Civilisation in China''. Cambridge University Press. pp. 186–91. {{ISBN|0-521-58000-5}}</ref> Coal from the [[Fushun]] mine in northeastern China was used to smelt [[copper]] as early as 1000 BC.<ref>[https://www.britannica.com/EBchecked/topic/122863/coal coal] {{webarchive|url=https://web.archive.org/web/20150502202950/https://www.britannica.com/EBchecked/topic/122863/coal |date=2 May 2015 }}. Encyclopædia Britannica.</ref> [[Marco Polo]], the Italian who traveled to China in the 13th century, described coal as "black stones&nbsp;... which burn like logs", and said coal was so plentiful, people could take three hot baths a week.<ref>[http://factsanddetails.com/china.php?itemid=47&catid=2 Marco Polo In China]. Facts and Details. Retrieved on 11 May 2013. {{webarchive |url=https://web.archive.org/web/20130921073525/http://factsanddetails.com/china.php?itemid=47&catid=2 |date=21 September 2013 }}</ref> In Europe, the earliest reference to the use of coal as fuel is from the geological treatise ''On Stones'' (Lap. 16) by the Greek scientist [[Theophrastus]] (c. 371–287 BC):<ref name = "Mattusch">{{Cite book| first=Mattusch|last= Carol |year=2008| title = Metalworking and Tools| editor-link=John Peter Oleson|editor-last = Oleson| editor-first= John Peter| series = The Oxford Handbook of Engineering and Technology in the Classical World| publisher = Oxford University Press| isbn= 978-0-19-518731-1| pages= 418–38 (432)}}</ref><ref>{{Cite book|url = https://books.google.com/books?id=qvTDGRMPU5kC|title = Greek Science of the Hellenistic Era: A Sourcebook|first1 = Georgia L.|last1 = Irby-Massie|first2 = Paul T.|last2 = Keyser|publisher = Routledge|year = 2002|at = 9.1 "Theophrastos", p. 228|isbn = 978-0-415-23847-2|url-status=live|archive-date = 5 February 2016|archive-url = https://web.archive.org/web/20160205090207/https://books.google.com/books?id=qvTDGRMPU5kC}}</ref>
{{blockquote|Among the materials that are dug because they are useful, those known as ''anthrakes'' [coals] are made of earth, and, once set on fire, they burn like charcoal [anthrakes]. They are found in Liguria&nbsp;... and in Elis as one approaches Olympia by the mountain road; and they are used by those who work in metals.|Theophrastus, On Stones (16) <ref>"το δ'  εκ  της  κατακαύσεως  ὅμοιον  γίνεται  γη   κεκαυμένη. οὓς  δε  καλοῦσιν  ευθὺς  ἄνθρακας των  ὀρυττομένων  δια  την  χρείαν  εισί  γεώδεις,  ἐκκαίονται  δε και πυροῦνται  καθάπερ  οἱ  ἄνθρακες. εισὶ δε  περί  τε  την Λιγυστικὴν ὅπου  και το  ἤλεκτρον, και  εν  τη  Ήλεία  βαδιζόντων   Όλυμπίαζε   την  δι' ὄρους,  οΐς   και  οἱ  χαλκεΐς   χρῶνται." [https://kb.osu.edu/dspace/bitstream/handle/1811/32541/THEOPHRASTUS_CALEY.pdf?sequence=1 ΠΕΡΙ ΛΙΘΩΝ], p. 21.</ref>}}
{{anchor|outcrop coal}}[[Outcrop]] coal was used in Britain during the [[Bronze Age]] (3000–2000 BC), where it formed part of [[funeral]] [[pyre]]s.<ref name = "Britannicacoal">Britannica 2004: ''Coal mining: ancient use of outcropping coal''</ref><ref>{{cite book |title=Science and Civilisation in China |url=https://archive.org/details/sciencecivilisat00need_094 |url-access=limited |first2= Peter J |last2=Golas |first1=Joseph |last1=Needham |pages = [https://archive.org/details/sciencecivilisat00need_094/page/n204 186]–91 | publisher =Cambridge University Press |year=1999 |isbn= 978-0-521-58000-7}}</ref> In [[Roman Britain]], with the exception of two modern fields, "the [[Mining in Roman Britain|Romans]] were exploiting coals in all the major coalfields in [[England]] and [[Wales]] by the end of the second century AD".<ref name="Smith 1997, 322–324">{{cite journal|author=Smith, A.H.V. |year=1997|title=Provenance of Coals from Roman Sites in England and Wales|journal=Britannia|volume=28|pages=297–324 (322–24)|jstor=526770|doi=10.2307/526770|s2cid=164153278 }}</ref> Evidence of trade in coal, dated to about AD 200, has been found at the [[Heronbridge Roman Site|Roman settlement at Heronbridge]], near [[Chester]]; and in the [[The Fens|Fenlands]] of [[East Anglia]], where coal from the [[English Midlands|Midlands]] was transported via the [[Car Dyke]] for use in drying grain.<ref>{{Cite book| last = Salway | first = Peter | year = 2001 | title = A History of Roman Britain|isbn=978-0-19-280138-8 | publisher = Oxford University Press}}</ref> Coal cinders have been found in the hearths of [[Roman villa|villas]] and [[Roman forts]], particularly in [[Northumberland]], dated to around AD 400. In the west of England, contemporary writers described the wonder of a permanent brazier of coal on the altar of [[Minerva]] at [[Aquae Sulis]] (modern day [[Bath, Somerset|Bath]]), although in fact easily accessible surface coal from what became the [[Somerset coalfield]] was in common use in quite lowly dwellings locally.<ref>Forbes, RJ (1966): ''Studies in Ancient Technology''. Brill Academic Publishers, Boston.</ref> Evidence of coal's use for [[iron]]-working in the city during the Roman period has been found.<ref>{{cite book| last = Cunliffe| first = Barry W.| author-link = Barry Cunliffe| title = Roman Bath Discovered| publisher = Routledge| year = 1984| location = London| pages = 14–15, 194| isbn = 978-0-7102-0196-6}}</ref> In [[Eschweiler]], [[Rhineland]], deposits of [[bituminous coal]] were used by the Romans for the smelting of [[iron ore]].<ref name="Smith 1997, 322–324"/>
[[File:Men of the Mine- Life at the Coal Face, Britain, 1942 D8263.jpg|thumb|left|Coal miner in Britain, 1942]]
{{anchor|Sea coal}}
No evidence exists of coal being of great importance in Britain before about AD 1000, the [[High Middle Ages]].<ref name = "TCC">{{cite book|last=Cantril|first=T.C.|title=Coal Mining|publisher=Cambridge University Press|location=Cambridge|year= 1914 | pages = 3–10| oclc =156716838}}</ref> Coal came to be referred to as "seacoal" in the 13th century; the wharf where the material arrived in London was known as Seacoal Lane, so identified in a charter of [[Henry III of England|King Henry III]] granted in 1253.<ref>{{cite book|title=Oxford English Dictionary|date=1 December 2010|publisher=Oxford University Press|chapter=coal, 5a|title-link=Oxford English Dictionary}}</ref> Initially, the name was given because much coal was found on the shore, having fallen from the exposed coal seams on cliffs above or washed out of underwater coal outcrops,<ref name = "TCC" /> but by the time of [[Henry VIII of England|Henry VIII]], it was understood to derive from the way it was carried to London by sea.<ref>[[John Caius]], quoted in Cantril (1914).</ref> In 1257–1259, coal from [[Newcastle upon Tyne]] was shipped to London for the [[metalsmith|smiths]] and [[lime (material)|lime]]-burners building [[Westminster Abbey]].<ref name = "TCC" /> Seacoal Lane and Newcastle Lane, where coal was unloaded at wharves along the [[River Fleet]], still exist.<ref>{{cite book|last=Trench|first= Richard |author2=Hillman, Ellis|title=London Under London: A Subterranean Guide|publisher=John Murray|location=London|year=1993| edition= Second | page=33|isbn=978-0-7195-5288-5}}</ref>
These easily accessible sources had largely become exhausted (or could not meet the growing demand) by the 13th century, when underground extraction by [[shaft mining]] or [[adit]]s was developed.<ref name="Britannicacoal" /> The alternative name was "pitcoal", because it came from mines.
[[File:The Harmsworth atlas and Gazetter 1908 (135852999).jpg|thumb|right|Coal production of the world in 1908 as presented by ''The Harmsworth atlas and Gazetter'']]
Cooking and home heating with coal (in addition to firewood or instead of it) has been done in various times and places throughout human history, especially in times and places where ground-surface coal was available and firewood was scarce, but a widespread reliance on coal for home hearths probably never existed until such a switch in fuels happened in London in the late sixteenth and early seventeenth centuries.<ref name="Goodman-2020">{{Citation |last=Goodman |first=Ruth |year=2020 |author-link=Ruth Goodman (historian) |title=The Domestic Revolution: How the Introduction of Coal Into Victorian Homes Changed Everything |publisher=Liveright |isbn=978-1631497636 |postscript=.}}</ref> Historian [[Ruth Goodman (historian)|Ruth Goodman]] has traced the socioeconomic effects of that switch and its later spread throughout Britain<ref name="Goodman-2020"/> and suggested that its importance in shaping the industrial adoption of coal has been previously underappreciated.<ref name="Goodman-2020"/>{{rp|xiv-xix}}
The development of the [[Industrial Revolution]] led to the large-scale use of coal, as the [[steam engine]] took over from the [[water wheel]]. In 1700, five-sixths of the world's coal was mined in Britain. Britain would have run out of suitable sites for watermills by the 1830s if coal had not been available as a source of energy.<ref name = "Wrigley">{{Cite book| title = Continuity, Chance and Change: The Character of the Industrial Revolution in England| first = EA| last = Wrigley| isbn = 978-0-521-39657-8| publisher = Cambridge University Press| year = 1990| url = https://archive.org/details/isbn_0521396573}}</ref> In 1947 there were some 750,000 miners in Britain,<ref name="BBC News">{{Cite news | url = http://news.bbc.co.uk/2/hi/business/551544.stm | title = The fall of King Coal | work = BBC News | date = 6 December 1999 | url-status = live | archive-url = https://web.archive.org/web/20160306015837/http://news.bbc.co.uk/2/hi/business/551544.stm | archive-date = 6 March 2016}}</ref> but the last deep coal mine in the UK closed in 2015.<ref>{{cite news |title=UK's last deep coal mine Kellingley Colliery capped off |url=https://www.bbc.com/news/uk-england-york-north-yorkshire-35803048 |work=[[BBC]] |date=14 March 2016}}</ref>
A grade between bituminous coal and anthracite was once known as "steam coal" as it was widely used as a fuel for [[steam locomotive]]s. In this specialized use, it is sometimes known as "sea coal" in the United States.<ref>[[Funk and Wagnalls]], quoted in {{cite book|title=Oxford English Dictionary|publisher=Oxford University Press|year=1989|edition=2|chapter=sea-coal|title-link=Oxford English Dictionary}}</ref> Small "steam coal", also called ''dry small steam nuts'' (DSSN), was used as a fuel for domestic [[water heating]].
Coal played an important role in industry in the 19th and 20th century. The predecessor of the [[European Union]], the [[European Coal and Steel Community]], was based on the trading of this commodity.<ref>{{cite web | url = https://carleton.ca/ces/eulearning/history/moving-to-integration/the-european-coal-and-steel-community/ | title = The European Coal and Steel Community | website = EU Learning | publisher = Carleton University School of European Studies | access-date = 14 August 2021 | url-status = live|archive-url=https://web.archive.org/web/20150417011518/http://carleton.ca:80/ces/eulearning/history/moving-to-integration/the-european-coal-and-steel-community/ |archive-date=17 April 2015 }}</ref>
Coal continues to arrive on beaches around the world from both natural erosion of exposed coal seams and windswept spills from cargo ships. Many homes in such areas gather this coal as a significant, and sometimes primary, source of home heating fuel.<ref>{{Cite web|url=https://www.alaskapublic.org/2018/03/22/cost-of-cold-staying-warm-in-homer/|title=Cost of Cold: Staying warm in Homer|last1=Bolton|first1=Aaron|last2=Homer|first2=KBBI-|date=2018-03-22|website=Alaska Public Media|language=en-US|access-date=2019-01-25}}</ref>
==Composition==
Coal consists mainly of a black mixture of diverse organic compounds and polymers. Of course, several kinds of coals exist, with variable dark colors and variable compositions. Young coals (brown coal, lignite) are not black. The two main black coals are bituminous, which is more abundant, and anthracite. The % carbon in coal follows the order anthracite > bituminous > lignite > brown coal. The fuel value of coal varies in the same order. Some anthracite deposits contain pure carbon in the form of [[graphite]].
For bituminous coal, the elemental composition on a dry, ash-free basis of 84.4% carbon, 5.4% hydrogen, 6.7% oxygen, 1.7% nitrogen, and 1.8% sulfur, on a weight basis.<ref name=Perry/> This composition reflects partly the composition of the precursor plants. The second main fraction of coal is ash, an undesirable, noncombustable mixture of inorganic minerals. The composition of ash is often discussed in terms of oxides obtained after combustion in air:
{| class=wikitable
|+ Ash composition, weight percent
| {{chem2|SiO2}}|| 20–40
|-
| {{chem2|Al2O3}}||10–35
|-
| {{chem2|Fe2O3}}||5–35
|-
| CaO||1–20
|-
| MgO||0.3–4
|-
| {{chem2|TiO2}}||0.5–2.5
|-
| {{chem2|Na2O}} & {{chem2|K2O}}||1–4
|-
| {{chem2|SO3}}||0.1–12<ref>Combines with other oxides to make sulfates.</ref>
|-
|}
Of particular interest is the sulfur content of coal, which can vary from less than 1% to as much as 4%. Most of the sulfur and most of the nitrogen is incorporated into the organic fraction in the form of [[organosulfur compound]]s and [[heterocycle|organonitrogen compound]]s. This sulfur and nitrogen are [[covalent bond|strongly bound]] within the hydrocarbon matrix. These elements are released as SO<sub>2</sub> and NO<sub>x</sub> upon combustion. They cannot be removed, economically at least, otherwise. Some coals contain inorganic sulfur, mainly in the form of [[iron pyrite]] (FeS<sub>2</sub>). Being a dense mineral, it can be removed from coal by mechanical means, e.g. by [[froth flotation]]. Some sulfate occurs in coal, especially weathered samples. It is not volatilized and can be removed by washing.<ref name= KO>{{cite book |doi=10.1002/0471238961.0315011222151818.a01.pub3 |chapter=Coal |title=Kirk-Othmer Encyclopedia of Chemical Technology |date=2016 |last1=Hower |first1=James |pages=1–63 |isbn=978-0-471-48494-3 }}</ref>
Minor components include:
{| class=wikitable
|+ Average content
! Substance !! Content
|-
| [[Mercury (element)|Mercury]] (Hg)
|align=right| {{val|0.10|0.01|u=[[Parts-per notation|ppm]]}}<ref name="lab_hg">{{cite web|title=Mercury in coal: a review; Part 1. Geochemistry |author=Ya. E. Yudovich, M.P. Ketris |url=http://www.labtechgroup.com/support/hg-1-yudovich.pdf |archive-url=https://web.archive.org/web/20140901135845/http://www.labtechgroup.com/support/Hg-1-Yudovich.pdf |archive-date=1 September 2014 |date=21 April 2010 |access-date=22 February 2013 |publisher=labtechgroup.com |url-status=dead}}</ref>
|-
| [[Arsenic]] (As)
|align=right| {{nowrap|1.4–71 [[Parts-per notation|ppm]]}}<ref name="usgs_fs2005">{{cite web|title=Arsenic in Coal|url=http://pubs.usgs.gov/fs/2005/3152/fs2005-3152.pdf|date=28 March 2006|access-date=22 February 2013 |publisher=pubs.usgs.gov|url-status=live|archive-date=9 May 2013|archive-url=https://web.archive.org/web/20130509051812/http://pubs.usgs.gov/fs/2005/3152/fs2005-3152.pdf}}</ref>
|-
| [[Selenium]] (Se)
|align=right| {{nowrap|3 [[Parts-per notation|ppm]]}}<ref name="acs_env">{{cite book|title=Selenium in Our Environment – Trace Elements in the Environment|volume=123|page=96|doi=10.1021/ba-1973-0123.ch006|date=1973|chapter=Selenium in Our {{sic|Enviro|ment|nolink-y}} |series=Advances in Chemistry|last1=Lakin|first1=Hubert W.|isbn=978-0-8412-0185-9}}</ref>
|}
As minerals, Hg, As, and Se are not problematic to the environment, especially since they are only trace components. They become however mobile (volatile or water-soluble) when these minerals are combusted.
==Uses==
Most coal is used as fuel. 27.6% of world energy was supplied by coal in 2017 and Asia used almost three-quarters of it.<ref>{{cite web |title=Primary energy |url=https://www.bp.com/en/global/corporate/energy-economics/statistical-review-of-world-energy/primary-energy.html |access-date=5 December 2018 |publisher=[[BP]]}}</ref> Other large-scale applications also exist. The [[energy density]] of coal is roughly 24 [[megajoule]]s per kilogram<ref>{{cite web |last=Fisher |first=Juliya |year=2003 |title=Energy Density of Coal |url=http://hypertextbook.com/facts/2003/JuliyaFisher.shtml |url-status=live |archive-url=https://web.archive.org/web/20061107152122/http://hypertextbook.com/facts/2003/JuliyaFisher.shtml |archive-date=7 November 2006 |access-date=25 August 2006 |work=The Physics Factbook}}</ref> (approximately 6.7 [[kilowatt-hours]] per kg). For a coal power plant with a 40% efficiency, it takes an estimated {{convert|325|kg|abbr=on}} of coal to power a 100&nbsp;W lightbulb for one year.<ref>{{cite web |date=2000-10-03 |title=How much coal is required to run a 100-watt light bulb 24 hours a day for a year? |url=http://science.howstuffworks.com/question481.htm |url-status=live |archive-url=https://web.archive.org/web/20060807235142/http://science.howstuffworks.com/question481.htm |archive-date=7 August 2006 |access-date=25 August 2006 |work=Howstuffworks}}</ref>
===Electricity generation===
{{Main|Coal-fired power station}}[[File:Grand Junction Trip 92007 098.JPG|thumb|[[Castle Gate Power Plant]] near Helper, Utah, US]]
[[File:Ashtabulacoalcars e2.jpg|thumb|Coal rail cars]]
[[File:Komatsu bulldozer pushing coal in Power plant Ljubljana (winter 2017).jpg|thumb|[[Bulldozer]] pushing coal in [[Ljubljana Power Station]], Slovenia]]
In 2022, 68% of global coal use was used for electricity generation.<ref name=":0" />{{Rp|page=11}}
Coal burnt in [[list of coal power stations|coal power stations]] to [[electricity generation|generate electricity]] is called '''thermal coal'''. It is usually pulverized and then burned in a furnace with a [[boiler]].<ref name="World Coal">[http://www.worldcoal.org/coal/uses-of-coal/coal-electricity/ Total World Electricity Generation by Fuel (2006)] {{webarchive|url=https://web.archive.org/web/20151022093430/http://www.worldcoal.org/coal/uses-of-coal/coal-electricity/|date=22 October 2015}}. Source: IEA 2008.</ref> The furnace heat converts boiler water to [[steam]], which is then used to spin [[turbine]]s which turn [[electrical generator|generators]] and create electricity.<ref>{{cite web |title=Fossil Power Generation |url=http://w1.siemens.com/responsibility/en/environment/portfolio/fossil_power_generation.htm |url-status=dead |archive-url=http://arquivo.pt/wayback/20090929225531/http://w1.siemens.com/responsibility/en/environment/portfolio/fossil_power_generation.htm |archive-date=29 September 2009 |access-date=23 April 2009 |publisher=Siemens AG}}</ref> The [[thermodynamic efficiency]] of this process varies between about 25% and 50% depending on the pre-combustion treatment, turbine technology (e.g. [[supercritical steam generator]]) and the age of the plant.<ref>J. Nunn, A. Cottrell, A. Urfer, L. Wibberley and P. Scaife, [http://www.docstoc.com/docs/80110435/TA-28-Vic-elec-grid-YED-2000-Final "A Lifecycle Assessment of the Victorian Energy Grid"] {{webarchive|url=https://web.archive.org/web/20160902132119/http://www.docstoc.com/docs/80110435/TA-28-Vic-elec-grid-YED-2000-Final|date=2 September 2016}}, Cooperative Research Centre for Coal in Sustainable Development, February 2003, p. 7.</ref><ref>{{cite web |title=Neurath F and G set new benchmarks |url=http://www.alstom.com/Global/Power/Resources/Documents/Brochures/neurath-fandg-supercritical-steam-power-plant-new-benchmarks.pdf |url-status=live |archive-url=https://web.archive.org/web/20150401132704/http://www.alstom.com/Global/Power/Resources/Documents/Brochures/neurath-fandg-supercritical-steam-power-plant-new-benchmarks.pdf |archive-date=1 April 2015 |access-date=21 July 2014 |publisher=Alstom}}</ref>
A few [[integrated gasification combined cycle]] (IGCC) power plants have been built, which burn coal more efficiently. Instead of pulverizing the coal and burning it directly as fuel in the steam-generating boiler, the [[coal gasification|coal is gasified]] to create [[syngas]], which is burned in a [[gas turbine]] to produce electricity (just like natural gas is burned in a turbine). Hot exhaust gases from the turbine are used to raise steam in a [[heat recovery steam generator]] which powers a supplemental [[steam turbine]]. The overall plant efficiency when used to provide [[combined heat and power]] can reach as much as 94%.<ref>[http://ipaper.ipapercms.dk/DONGENERGY/Internet/UK/ThermalPower/AVVbrochure2012UK/ Avedøreværket] {{webarchive|url=https://web.archive.org/web/20160129110317/http://ipaper.ipapercms.dk/DONGENERGY/Internet/UK/ThermalPower/AVVbrochure2012UK/|date=29 January 2016}}. Ipaper.ipapercms.dk. Retrieved on 11 May 2013.</ref> IGCC power plants emit less local pollution than conventional pulverized coal-fueled plants. Other ways to use coal are as [[coal-water slurry fuel]] (CWS), which was developed in the [[Soviet Union]], or in [[magnetohydrodynamic generator|an MHD topping cycle]]. However these are not widely used due to lack of profit.
In 2017 38% of the world's electricity came from coal, the same percentage as 30 years previously.<ref>{{cite web |date=2018-06-15 |title=The most depressing energy chart of the year |url=https://www.vox.com/energy-and-environment/2018/6/15/17467164/energy-chart-renewables-coal-climate-change |access-date=30 October 2018 |publisher=Vox}}</ref> In 2018 global installed capacity was 2[[terawatt|TW]] (of which 1TW is in China) which was 30% of total electricity generation capacity.<ref name="Cornot-Gandolfe 2018">{{cite book |last1=Cornot-Gandolfe |first1=Sylvie |url=https://www.ifri.org/sites/default/files/atoms/files/cornot_gandolphe_coal_exit_2018.pdf |title=A Review of Coal Market Trends and Policies in 2017 |date=May 2018 |publisher=Ifri |archive-url=https://web.archive.org/web/20181115153650/https://www.ifri.org/sites/default/files/atoms/files/cornot_gandolphe_coal_exit_2018.pdf |archive-date=2018-11-15 |url-status=live}}</ref> The most dependent major country is South Africa, with over 80% of its electricity generated by coal;<ref>{{cite web |title=Energy Revolution: A Global Outlook |url=https://www.drax.com/wp-content/uploads/2018/12/Energy-Revolution-Global-Outlook-Report-Final-Dec-2018-COP24.pdf |url-status=live |archive-url=https://web.archive.org/web/20190209123738/https://www.drax.com/wp-content/uploads/2018/12/Energy-Revolution-Global-Outlook-Report-Final-Dec-2018-COP24.pdf |archive-date=2019-02-09 |access-date=7 February 2019 |publisher=Drax}}</ref> but China alone generates more than half of the world's coal-generated electricity.<ref>{{cite news |date=28 March 2021 |title=China generated over half world's coal-fired power in 2020: study |url=https://www.reuters.com/article/us-climate-change-china-coal/china-generated-over-half-worlds-coal-fired-power-in-2020-study-idUSKBN2BK0PZ |access-date=14 September 2021 |work=[[Reuters]] |quote=China generated 53% of the world's total coal-fired power in 2020, nine percentage points more that five years earlier}}</ref> Efforts around the world to reduce the use of coal have led some regions to switch to natural gas and [[renewable energy]]. In 2018 coal-fired power station [[capacity factor]] averaged 51%, that is they operated for about half their available operating hours.<ref>{{Cite report |url=https://endcoal.org/wp-content/uploads/2020/03/BoomAndBust_2020_English.pdf |title=Boom and Bust 2020: Tracking the Global Coal Plant Pipeline |last1=Shearer |first1=Christine |last2=Myllyvirta |first2=Lauri |date=March 2020 |publisher=[[Global Energy Monitor]] |last3=Yu |first3=Aiqun |last4=Aitken |first4=Greig |last5=Mathew-Shah |first5=Neha |last6=Dallos |first6=Gyorgy |last7=Nace |first7=Ted |access-date=27 April 2020 |archive-url=https://web.archive.org/web/20200327062155/https://endcoal.org/wp-content/uploads/2020/03/BoomAndBust_2020_English.pdf |archive-date=27 March 2020 |url-status=dead}}</ref>
===Coke===
{{Main|Coke (fuel)}}
[[File:Coke Ovens Abercwmboi.jpg|right|thumb|Coke oven at a [[smokeless fuel]] plant in [[Wales]], United Kingdom]]
Coke is a solid carbonaceous residue that is used in manufacturing steel and other iron-containing products.<ref name="World Coal Steel">{{cite web|title=How is Steel Produced?|url=https://www.worldcoal.org/coal/uses-coal/how-steel-produced|publisher=[[World Coal Association]]|access-date=April 8, 2017|url-status=live|archive-url=https://web.archive.org/web/20170412114829/https://www.worldcoal.org/coal/uses-coal/how-steel-produced|archive-date=12 April 2017|date=2015-04-28}}</ref> Coke is made when [[metallurgical coal]] (also known as ''coking coal'') is baked in an oven without oxygen at temperatures as high as 1,000&nbsp;°C, driving off the volatile constituents and fusing together the fixed carbon and residual ash. Metallurgical coke is used as a fuel and as a [[reducing agent]] in [[smelting]] iron ore in a [[blast furnace]].<ref>[http://www.steelonthenet.com/cost-bof.html Blast furnace steelmaking cost model] {{webarchive|url=https://web.archive.org/web/20160114013811/http://www.steelonthenet.com/cost-bof.html |date=14 January 2016 }}. Steelonthenet.com. Retrieved on 24 August 2012.</ref> The carbon monoxide produced by its combustion reduces [[hematite]] (an [[iron oxide]]) to iron.
:{{chem2|2 Fe2O3 + 6 CO -> 4 Fe + 6 CO2}}
[[Pig iron]], which is too rich in dissolved carbon, is also produced.
The coke must be [[Coke strength after reaction|strong enough]] to resist the weight of overburden in the blast furnace, which is why coking coal is so important in making steel using the conventional route. Coke from coal is grey, hard, and porous and has a heating value of 29.6 MJ/kg. Some coke-making processes produce byproducts, including [[coal tar]], [[ammonia]], light oils, and [[coal gas]].
[[Petroleum coke]] (petcoke) is the solid residue obtained in [[oil refining]], which resembles coke but contains too many impurities to be useful in metallurgical applications.
===Production of chemicals===
[[File:Coal to chemicals routes diagram.jpg|upright=1.35|thumb|Production of chemicals from coal]]
Chemicals have been produced from coal since the 1950s. Coal can be used as a feedstock in the production of a wide range of chemical fertilizers and other chemical products. The main route to these products was [[coal gasification]] to produce [[syngas]]. Primary chemicals that are produced directly from the syngas include [[methanol]], [[hydrogen]], and [[carbon monoxide]], which are the chemical building blocks from which a whole spectrum of derivative chemicals are manufactured, including [[olefins]], [[acetic acid]], [[formaldehyde]], ammonia, [[urea]], and others. The versatility of [[syngas]] as a precursor to primary chemicals and high-value derivative products provides the option of using coal to produce a wide range of commodities. In the 21st century, however, the use of [[Coalbed methane|coal bed methane]] is becoming more important.<ref>{{Cite web|title=Coal India begins process of developing Rs 2,474 crore CBM projects {{!}} Hellenic Shipping News Worldwide|url=https://www.hellenicshippingnews.com/coal-india-begins-process-of-developing-rs-2474-crore-cbm-projects/|website=www.hellenicshippingnews.com|access-date=2020-05-31}}</ref>
Because the slate of chemical products that can be made via coal gasification can in general also use feedstocks derived from [[natural gas]] and [[petroleum]], the chemical industry tends to use whatever feedstocks are most cost-effective. Therefore, interest in using coal tended to increase for higher oil and natural gas prices and during periods of high global economic growth that might have strained oil and gas production.
Coal to chemical processes require substantial quantities of water.<ref>{{Cite web|title=Coal-to-Chemicals: Shenhua's Water Grab|url=http://www.chinawaterrisk.org/opinions/coal-to-chemicals-shenhuas-water-grab-2/|website=China Water Risk|language=en-US|access-date=2020-05-31}}</ref> Much coal to chemical production is in China<ref name=OILDRUM9371>{{cite web|title=China's Coal to Chemical Future|url=http://www.theoildrum.com/node/9371|publisher=The Oil Drum.Com|access-date=3 March 2013|author=Rembrandt|format=Blog post by expert|date=2 August 2012}}</ref><ref name=ICIS022712>{{cite news|title=China develops coal-to-olefins projects, which could lead to ethylene self-sufficiency|url=http://www.icis.com/Articles/2012/02/27/9535534/china-develops-coal-to-olefins-projects-which-could-lead-to-ethylene.html|author= Yin, Ken|access-date=3 March 2013|newspaper=ICIS Chemical Business|date=27 February 2012}}</ref> where coal dependent provinces such as [[Shanxi]] are struggling to control its pollution.<ref>{{cite news |title=Smog war casualty: China coal city bears brunt of pollution crackdown |url=https://www.reuters.com/article/us-china-pollution-economy-insight/smog-war-casualty-china-coal-city-bears-brunt-of-pollution-crackdown-idUSKCN1NV2RB |work=[[Reuters]] |date=27 November 2018}}</ref>
===Liquefaction===
{{Main|Coal liquefaction}}
Coal can be converted directly into [[synthetic fuel]]s equivalent to gasoline or diesel by [[hydrogenation]] or [[carbonization]].<ref>{{cite web|url=http://www.netl.doe.gov/research/Coal/energy-systems/gasification/gasifipedia/direct-liquefaction|title=Direct Liquefaction Processes|publisher=National Energy Technology Laboratory|access-date=16 July 2014|url-status=live|archive-date=25 July 2014|archive-url=https://web.archive.org/web/20140725082303/http://www.netl.doe.gov/research/Coal/energy-systems/gasification/gasifipedia/direct-liquefaction}}</ref> Coal liquefaction emits more carbon dioxide than liquid fuel production from [[crude oil]]. Mixing in biomass and using CCS would emit slightly less than the oil process but at a high cost.<ref>{{cite journal |title=Economic and environmental analyses of coal and biomass to liquid fuels |journal=Energy |volume=141|pages=76–86|doi=10.1016/j.energy.2017.09.047|year=2017|last1=Liu|first1=Weiguo|last2=Wang|first2=Jingxin|last3=Bhattacharyya|first3=Debangsu |last4=Jiang|first4=Yuan |last5=Devallance|first5=David|doi-access=free|bibcode=2017Ene...141...76L }}</ref> State owned [[China Energy Investment]] runs a coal liquefaction plant and plans to build 2 more.<ref>{{cite news |title=CHN Energy to build new coal-to-liquid production lines |url=http://en.silkroad.news.cn/2018/0813/106231.shtml |agency=Xinhua News Agency |date=13 August 2018}}</ref>
Coal liquefaction may also refer to the cargo hazard when shipping coal.<ref>{{cite news |title=New IMSBC Code requirements aim to control liquefaction of coal cargoes |url=https://www.hellenicshippingnews.com/new-imsbc-code-requirements-aim-to-control-liquefaction-of-coal-cargoes/ |work=Hellenic Shipping News Worldwide |date=29 November 2018 |access-date=1 December 2018 |archive-date=3 August 2020 |archive-url=https://web.archive.org/web/20200803211939/https://www.hellenicshippingnews.com/new-imsbc-code-requirements-aim-to-control-liquefaction-of-coal-cargoes/ |url-status=dead }}</ref>
===Gasification===
{{Main|Coal gasification|Underground coal gasification}}
Coal gasification, as part of an [[integrated gasification combined cycle]] (IGCC) coal-fired power station, is used to produce [[syngas]], a mixture of [[carbon monoxide]] (CO) and hydrogen (H<sub>2</sub>) gas to fire gas turbines to produce electricity. Syngas can also be converted into transportation fuels, such as [[gasoline]] and [[Diesel fuel|diesel]], through the [[Fischer–Tropsch process]]; alternatively, syngas can be converted into [[methanol]], which can be blended into fuel directly or converted to gasoline via the methanol to gasoline process.<ref>{{cite web |url=http://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/methanol-to-gasoline |title=Conversion of Methanol to Gasoline |publisher=National Energy Technology Laboratory |access-date=16 July 2014 |url-status=live |archive-url=https://web.archive.org/web/20140717225057/http://www.netl.doe.gov/research/Coal/energy-systems/gasification/gasifipedia/methanol-to-gasoline |archive-date=17 July 2014}}</ref> Gasification combined with Fischer–Tropsch technology was used by the [[Sasol]] chemical company of [[South Africa]] to make chemicals and motor vehicle fuels from coal.<ref>{{Cite news|title=Sasol Is Said to Plan Sale of Its South Africa Coal Mining Unit |url=https://www.bloomberg.com/news/articles/2019-09-18/sasol-is-said-to-plan-sale-of-its-south-africa-coal-mining-unit|newspaper=Bloomberg.com|date=18 September 2019|access-date=2020-05-31}}</ref>
During gasification, the coal is mixed with [[oxygen]] and [[steam]] while also being heated and pressurized. During the reaction, oxygen and water molecules [[Redox|oxidize]] the coal into carbon monoxide (CO), while also releasing [[hydrogen]] gas (H<sub>2</sub>). This used to be done in underground coal mines, and also to make [[town gas]], which was piped to customers to burn for illumination, heating, and cooking.
: 3C (''as Coal'') + O<sub>2</sub> + H<sub>2</sub>O → H<sub>2</sub> + 3CO
If the refiner wants to produce gasoline, the syngas is routed into a Fischer–Tropsch reaction. This is known as indirect coal liquefaction. If hydrogen is the desired end-product, however, the syngas is fed into the [[water gas shift reaction]], where more hydrogen is liberated:
: CO + H<sub>2</sub>O → CO<sub>2</sub> + H<sub>2</sub>
==Coal industry==
{{main|:Category:Coal companies|Coal mining|Coal by country|Coal industry in China|Coal industry in Pakistan|Coal industry in India|Coal companies of Australia}}
===Mining===
{{main|Coal mining}}
[[File:Miners at the Virginia-Pocahontas Coal Company Mine.jpg|thumb|Coal miners in the [[Appalachia]] region in 1974]]
About 8,000 Mt of coal are produced annually, about 90% of which is hard coal and 10% lignite. {{As of|2018}} just over half is from underground mines.<ref>{{cite web |title=Coal mining |url=https://www.worldcoal.org/coal/coal-mining |publisher=[[World Coal Association]] |access-date=5 December 2018|date=2015-04-28 }}</ref> The coal mining industry employs almost 2.7 million workers.<ref>{{cite news |title=Coal industry faces 1 million job losses from global energy transition - research |url=https://www.reuters.com/markets/coal-industry-faces-1-million-job-losses-global-energy-transition-research-2023-10-10/ |work=Reuters |date=10 October 2023}}</ref> More accidents occur during underground mining than surface mining. Not all countries publish [[mining accident]] statistics so worldwide figures are uncertain, but it is thought that most deaths occur in [[List of coal mining accidents in China|coal mining accidents in China]]: in 2017 there were 375 coal mining related deaths in China.<ref>{{cite news |title=China: seven miners killed after skip plummets down mine shaft |url=https://www.theguardian.com/world/2018/dec/16/miners-killed-in-south-west-china-mining-accident |newspaper=[[The Guardian]] |date=16 December 2018|agency=Agence France-Presse }}</ref> Most coal mined is thermal coal (also called steam coal as it is used to make steam to generate electricity) but metallurgical coal (also called "metcoal" or "coking coal" as it is used to make coke to make iron) accounts for 10% to 15% of global coal use.<ref>{{cite magazine |title=The One Market That's Sure To Help Coal |url=https://www.forbes.com/sites/judeclemente/2018/08/12/the-one-market-thats-sure-to-help-coal/#570c071f6f6e |magazine=[[Forbes]] |date=12 August 2018}}</ref>
===As a traded commodity===
{{See also|Cost of electricity by source}}[[File:Art work of Toledo, Ohio - DPLA - 0a107364e8d8eb430ebc183d28c46463 (page 125) (cropped).jpg|thumb|right|Extensive coal docks seen in [[Toledo, Ohio]], 1895]]
[[Coal in China|China mines]] almost half the world's coal, followed by [[Coal in India|India]] with about a tenth.<ref name="BPReview2016">{{cite web |title=BP Statistical review of world energy 2016 |url=http://www.bp.com/content/dam/bp/excel/energy-economics/statistical-review-2016/bp-statistical-review-of-world-energy-2016-workbook.xlsx |url-status=live |archive-url=https://web.archive.org/web/20161202103642/http://www.bp.com/content/dam/bp/excel/energy-economics/statistical-review-2016/bp-statistical-review-of-world-energy-2016-workbook.xlsx |archive-date=2 December 2016 |access-date=8 February 2017 |publisher=British Petroleum |format=XLS}}</ref>  At 471 Mt and a 34% share of global exports, Indonesia was the largest exporter by volume in 2022, followed by Australia with 344 Mt and Russia with 224 Mt.<ref name=":1">{{Cite web |title=Trade – Coal 2023 – Analysis |url=https://www.iea.org/reports/coal-2023/trade |access-date=2024-10-28 |website=IEA |language=en-GB}}Text was copied from this source, which is available under a [[creativecommons:by/4.0/|Creative Commons Attribution 4.0 International License]]</ref> Other major exporters of coal are the United States, South Africa, Colombia, and Canada.<ref name=":0" />{{Rp|page=118}} In 2022, China, India, and Japan were the biggest importers of coal, importing 301, 228, and 184 Mt respectively.<ref name=":0" />{{Rp|page=117}}  Russia is increasingly orienting its coal exports from Europe to Asia as Europe transitions to renewable energy and subjects Russia to sanctions over its invasion of Ukraine.<ref name="Overland-2023" />
The price of metallurgical coal is volatile<ref>{{cite web |title=Coal 2017 |url=https://eneken.ieej.or.jp/data/7732.pdf |archive-url=https://web.archive.org/web/20180620012116/http://eneken.ieej.or.jp/data/7732.pdf |archive-date=2018-06-20 |url-status=live |publisher=[[International Energy Agency|IEA]] |access-date=26 November 2018}}</ref> and much higher than the price of thermal coal because metallurgical coal must be lower in sulfur and requires more cleaning.<ref>{{cite web |title=Coal Prices and Outlook |url=https://www.eia.gov/energyexplained/index.php?page=coal_prices |publisher=U.S. Energy Information Administration}}</ref> Coal futures contracts provide coal producers and the [[electric power industry]] an important tool for [[Hedge (finance)|hedging]] and [[risk management]].
In some countries, new onshore [[wind power|wind]] or [[solar power|solar]] generation already costs less than coal power from existing plants.<ref>{{Cite news| title = New wind and solar generation costs fall below existing coal plants |work=Financial Times| access-date = 2018-11-08| url = https://www.ft.com/content/af6915c8-e2eb-11e8-a6e5-792428919cee}}</ref><ref>{{cite web |title=Lazard's Levelized Cost of Energy ('LCOE') analysis – Version 12.0 |url=https://www.lazard.com/media/450773/lazards-levelized-cost-of-energy-version-120-vfinal.pdf |archive-url=https://web.archive.org/web/20181109235056/https://www.lazard.com/media/450773/lazards-levelized-cost-of-energy-version-120-vfinal.pdf |archive-date=2018-11-09 |url-status=live |access-date=9 November 2018}}</ref>
However, for China this is forecast for the early 2020s<ref name="CarbTrk2018">{{cite web |title=40% of China's coal power stations are losing money |url=https://www.carbontracker.org/40-of-chinas-coal-power-stations-are-losing-money/ |publisher=Carbon Tracker |access-date=11 November 2018|date=2018-10-11 }}</ref> and for southeast Asia not until the late 2020s.<ref>{{cite web |title=Economic and financial risks of coal power in Indonesia, Vietnam and the Philippines |url=https://www.carbontracker.org/reports/economic-and-financial-risks-of-coal-power-in-indonesia-vietnam-and-the-philippines/ |publisher=Carbon Tracker |access-date=9 November 2018}}</ref> In India, building new plants is uneconomic and, despite being subsidized, existing plants are losing market share to renewables.<ref>{{cite news |title=India's Coal Paradox |url=https://oilprice.com/Energy/Coal/Indias-Coal-Paradox.html |date=5 January 2019}}</ref>
In many countries in the Global North, there is a move away from the use of coal and former mine sites are being used as a tourist attraction.<ref>{{Cite journal |last1=Pukowiec-Kurda |first1=Katarzyna |last2=Apollo |first2=Michal |date=2024-08-27 |title=From coal to tourism: a game-changer in the sustainable transition process |url=https://www.emerald.com/insight/content/doi/10.1108/JTF-05-2024-0086/full/html |journal=Journal of Tourism Futures |language=en |doi=10.1108/JTF-05-2024-0086 |issn=2055-5911|doi-access=free }}</ref>
===Market trends===
{{See also|List of countries by coal production}}
[[File:Coal production by region, OWID.svg|thumb|upright=1.8|Coal production by region]]
In 2022, China used 4520 Mt of coal, comprising more than half of global coal consumption. India, the European Union, and the United States,  were the next largest consumers of coal, using 1162, 461, and 455 Mt respectively.<ref name=":0">{{Cite web |date=2023-12-15 |title=Coal 2023 – Analysis |url=https://www.iea.org/reports/coal-2023 |access-date=2024-10-28 |website=IEA |language=en-GB}}</ref>{{Rp|page=114}}  Over the past decade, China has almost always accounted for the lion's share of the global growth in coal demand.<ref>{{Cite web |title=Consumption – Coal Information: Overview – Analysis |url=https://www.iea.org/reports/coal-information-overview/consumption |access-date=2024-10-28 |website=IEA |language=en-GB}}Text was copied from this source, which is available under a [[creativecommons:by/4.0/|Creative Commons Attribution 4.0 International License]]</ref> Therefore, international market trends depend on [[Energy policy of China|Chinese energy policy]].<ref name="IEA2018">{{cite web |date=2018 |title=Coal 2018:Executive Summary |url=https://webstore.iea.org/download/summary/2415 |url-status=dead |archive-url=https://web.archive.org/web/20181218193720/https://webstore.iea.org/download/summary/2415 |archive-date=18 December 2018 |access-date=18 December 2018 |publisher=[[International Energy Agency]]}}</ref>
Although the government effort to reduce air pollution in China means that the global long-term trend is to burn less coal, the short and medium term trends may differ, in part due to Chinese financing of new coal-fired power plants in other countries.<ref name="Cornot-Gandolfe 2018" />
Preliminary analysis by [[International Energy Agency]] (IEA) indicates that global coal exports reached an all-time high in 2023. Through to 2026, the IEA expects global coal trade to decline by about 12%, driven by growing domestic production in coal-intensive economies such as China and India and [[coal phase-out]] plans elsewhere, such as in Europe.<ref name=":1" /> While thermal coal exports are expected to decline by about 16% by 2026, exports of metallurgical coal are expected to slightly increase by almost 2%.<ref name=":1" />
==Damage to human health{{anchor|Health_effects}}==
[[File:2021 Death rates, by energy source.svg|thumb|Deaths caused as a result of fossil fuel use, especially coal (areas of rectangles in chart) greatly exceed those resulting from production of [[renewable energy]] (rectangles barely visible in chart).<ref name="OWID_SafestEnergy_2021">{{cite journal |last1=Ritchie |first1=Hannah |last2=Roser |first2=Max |title=What are the safest and cleanest sources of energy? |url=https://ourworldindata.org/safest-sources-of-energy |journal=Our World in Data |archive-url=https://web.archive.org/web/20240115112316/https://ourworldindata.org/safest-sources-of-energy |archive-date=15 January 2024 |date=2021 |url-status=live }} Data sources: Markandya & Wilkinson (2007); UNSCEAR (2008; 2018); Sovacool et al. (2016); IPCC AR5 (2014); Pehl et al. (2017); Ember Energy (2021).</ref>]]
The use of coal as fuel causes health problems and deaths.<ref>[http://www.lungusa.org/assets/documents/healthy-air/toxic-air-report.pdf Toxic Air: The Case for Cleaning Up Coal-fired Power Plants]. American Lung Association (March 2011) {{webarchive |url=https://web.archive.org/web/20120126123239/http://www.lungusa.org/assets/documents/healthy-air/toxic-air-report.pdf |date=26 January 2012 }}</ref> The mining and processing of coal causes air and water pollution.<ref name="Hendryx-2020">{{Cite journal|last1=Hendryx|first1=Michael|last2=Zullig|first2=Keith J.|last3=Luo|first3=Juhua|date=2020-01-08|title=Impacts of Coal Use on Health|journal=Annual Review of Public Health|volume=41 |doi=10.1146/annurev-publhealth-040119-094104|pmid=31913772|issn=0163-7525|doi-access=free|pages=397–415}}</ref> Coal-powered plants emit nitrogen oxides, sulfur dioxide, particulate pollution, and heavy metals, which adversely affect human health.<ref name="Hendryx-2020" /> [[Coalbed methane extraction|Coal bed methane extraction]] is important to avoid mining accidents.
The deadly [[Pea soup fog#London|London smog]] was caused primarily by the heavy use of coal. Globally coal is estimated to cause 800,000 premature deaths every year,<ref name="Endcoal health">{{cite web |title=Health |url=https://endcoal.org/health/ |publisher=Endcoal |access-date=3 December 2018 |archive-date=22 December 2017 |archive-url=https://web.archive.org/web/20171222052743/https://endcoal.org/health/ |url-status=dead }}</ref> mostly in India<ref name="Economist2018">{{cite news |title=India shows how hard it is to move beyond fossil fuels |newspaper=The Economist |url=https://www.economist.com/briefing/2018/08/02/india-shows-how-hard-it-is-to-move-beyond-fossil-fuels |date=2 August 2018}}</ref> and China.<ref>[https://www.who.int/quantifying_ehimpacts/publications/preventing-disease/en/ Preventing disease through healthy environments: a global assessment of the burden of disease from environmental risks] {{webarchive|url=https://web.archive.org/web/20160730124831/http://www.who.int/quantifying_ehimpacts/publications/preventing-disease/en/ |date=30 July 2016 }}. World Health Organization (2006)</ref><ref>{{cite book |url=https://www.who.int/healthinfo/global_burden_disease/GlobalHealthRisks_report_full.pdf|isbn=978-92-4-156387-1|date=2009|publisher=World Health Organization|title=Global Health Risks: Mortality and Burden of Disease Attributable to Selected Major Risks|url-status=live|archive-url=https://web.archive.org/web/20120214111235/http://www.who.int/healthinfo/global_burden_disease/GlobalHealthRisks_report_full.pdf|archive-date=14 February 2012}}</ref><ref>{{cite web|url=https://www.who.int/mediacentre/factsheets/fs313/en/ |title=WHO – Ambient (outdoor) air quality and health |work=who.int |access-date=7 January 2016 |url-status=dead |archive-date=4 January 2016 |archive-url=https://web.archive.org/web/20160104165807/http://www.who.int/mediacentre/factsheets/fs313/en/}}</ref>
Burning coal is a major contributor to [[sulfur dioxide]] emissions, which creates PM2.5 [[particulates]], the most dangerous form of air pollution.<ref>{{Cite news|url=https://storage.googleapis.com/planet4-international-stateless/2019/08/e40af3dd-global-hotspot-and-emission-sources-for-so2_16_august-2019.pdf |archive-url=https://web.archive.org/web/20191003074644/https://storage.googleapis.com/planet4-international-stateless/2019/08/e40af3dd-global-hotspot-and-emission-sources-for-so2_16_august-2019.pdf |archive-date=2019-10-03 |url-status=live|title=Global SO2 emission hotspot database|date=August 2019|publisher=[[Greenpeace]]}}</ref>
Coal smokestack emissions cause [[asthma]], [[strokes]], reduced [[intelligence]], [[artery]] blockages, [[heart attacks]], [[congestive heart failure]], [[cardiac arrhythmias]], [[mercury poisoning]], [[Stenosis|arterial occlusion]], and [[lung cancer]].<ref name="psr_coal-damages-health">[http://www.psr.org/news-events/press-releases/coal-pollution-damages-human-health.html Coal Pollution Damages Human Health at Every Stage of Coal Life Cycle, Reports Physicians for Social Responsibility] {{webarchive|url=https://web.archive.org/web/20150731182839/http://www.psr.org/news-events/press-releases/coal-pollution-damages-human-health.html |date=31 July 2015 }}. ''Physicians for Social Responsibility''. psr.org (18 November 2009)</ref><ref>Burt, Erica; Orris, Peter and Buchanan, Susan (April 2013) [http://noharm.org/lib/downloads/climate/Coal_Literature_Review_2.pdf Scientific Evidence of Health Effects from Coal Use in Energy Generation] {{webarchive|url=https://web.archive.org/web/20150714193454/http://noharm.org/lib/downloads/climate/Coal_Literature_Review_2.pdf |date=14 July 2015 }}. University of Illinois at Chicago School of Public Health, Chicago, Illinois, US</ref>
Annual health costs in Europe from use of coal to generate electricity are estimated at up to €43 billion.<ref>{{cite web|title=The Unpaid Health Bill – How coal power plants make us sick|url=https://www.env-health.org/unpaid-health-bill-how-coal-power-plants-make-us-sick/|publisher=Health and Environment Alliance|access-date=15 December 2018|date=2013-03-07}}</ref>
In China, early deaths due to air pollution coal plants have been estimated at 200 per GW-year, however they may be higher around power plants where scrubbers are not used or lower if they are far from cities.<ref>{{Cite web |date=2016-11-18 |title=Coal in China: Estimating Deaths per GW-year |url=http://berkeleyearth.org/deaths-per-gigawatt-year/ |access-date=2020-02-01 |website=Berkeley Earth |language=en-US}}</ref>  Improvements to China's air quality and human health would grow with more stringent climate policies, mainly because the country's energy is so heavily reliant on coal. And there would be a net economic benefit.<ref>{{cite web|title=Health benefits will offset cost of China's climate policy|date=23 April 2018 |url=https://news.mit.edu/2018/study-health-benefits-will-offset-cost-china-climate-policy-0423|publisher=[[MIT]]|access-date=15 December 2018}}</ref>
A 2017 study in the ''[[Economic Journal]]'' found that for Britain during the period 1851–1860, "a one standard deviation increase in coal use raised infant mortality by 6–8% and that industrial coal use explains roughly one-third of the urban mortality penalty observed during this period."<ref>{{Cite journal|last1=Beach|first1=Brian|last2=Hanlon|first2=W. Walker|title=Coal Smoke and Mortality in an Early Industrial Economy|journal=[[The Economic Journal]] |volume=128|issue=615|language=en|pages=2652–2675|doi=10.1111/ecoj.12522|issn=1468-0297|year=2018|s2cid=7406965}}</ref>
Breathing in [[coal dust]] causes [[coalworker's pneumoconiosis]] or "black lung", so called because the coal dust literally turns the lungs black.<ref>{{cite web|url=http://www.webmd.com/lung/tc/black-lung-disease-topic-overview|title=Black Lung Disease-Topic Overview|work=WebMD|url-status=live|archive-url=https://web.archive.org/web/20150710021533/http://www.webmd.com/lung/tc/black-lung-disease-topic-overview|archive-date=10 July 2015}}</ref> In the US alone, it is estimated that 1,500 former employees of the coal industry die every year from the effects of breathing in coal mine dust.<ref>{{cite web|url=http://www.umwa.org/?q=content/black-lung|title=Black Lung|work=umwa.org|access-date=7 January 2016|url-status=live|archive-url=https://web.archive.org/web/20160203042713/http://www.umwa.org/?q=content%2Fblack-lung|archive-date=3 February 2016}}</ref>
Huge amounts of coal ash and other waste is produced annually. Use of coal generates hundreds of millions of tons of ash and other waste products every year. These include [[fly ash]], [[bottom ash]], and [[flue-gas desulfurization]] sludge, that contain [[mercury (element)|mercury]], [[uranium]], [[thorium]], [[arsenic]], and other [[heavy metals]], along with non-metals such as [[selenium]].<ref>World Coal Association [http://www.worldcoal.org/pages/content/index.asp?PageID=127 "Environmental impact of Coal Use"] {{webarchive|url=https://web.archive.org/web/20090223203113/http://www.worldcoal.org/pages/content/index.asp?PageID=127 |date=23 February 2009 }}</ref>
Around 10% of coal is ash.<ref>{{cite web|archive-url=https://web.archive.org/web/20150720233354/http://www.epa.gov/cleanenergy/energy-and-you/affect/coal.html|archive-date=20 July 2015|url=http://www.epa.gov/cleanenergy/energy-and-you/affect/coal.html|title=Coal|work=U.S. Environmental Protection Agency |date=2014-02-05}}</ref> [[Coal ash]] is hazardous and toxic to human beings and some other living things.<ref>{{cite web|url=http://www.psr.org/environment-and-health/code-black/coal-ash-toxic-and-leaking.html|title=Coal Ash: Toxic – and Leaking|work=psr.org|url-status=live|archive-url=https://web.archive.org/web/20150715170100/http://www.psr.org/environment-and-health/code-black/coal-ash-toxic-and-leaking.html|archive-date=15 July 2015}}</ref> Coal ash contains the radioactive elements [[uranium]] and [[thorium]]. Coal ash and other solid combustion byproducts are stored locally and escape in various ways that expose those living near [[coal plants]] to radiation and environmental toxics.<ref name="sa-coal-ash-more-rdactiv">{{cite web|url=http://www.scientificamerican.com/article/coal-ash-is-more-radioactive-than-nuclear-waste|title=Coal Ash Is More Radioactive than Nuclear Waste|author=Hvistendahl, Mara|work=Scientific American|date=13 December 2007|url-status=live|archive-url=https://web.archive.org/web/20150710171812/http://www.scientificamerican.com/article/coal-ash-is-more-radioactive-than-nuclear-waste/|archive-date=10 July 2015}}</ref>
==Damage to the environment==
{{Main|Environmental impact of the coal industry}}
[[File:Aerial view of ash slide site Dec 23 2008 TVA.gov 123002.jpg|thumb|Aerial photograph of the site of the [[Kingston Fossil Plant]] coal fly ash slurry spill taken the day after [[Kingston Fossil Plant coal fly ash slurry spill|the event]]]]
[[Coal mining]], [[coal combustion wastes]], and [[flue gas]] are causing major environmental damage.<ref>{{Cite web |title=Coal and the environment |url=https://www.eia.gov/energyexplained/coal/coal-and-the-environment.php |access-date=2023-01-27 |website=U.S. Energy Information Administration (EIA)}}</ref><ref>{{Cite web |last=Zagoruichyk |first=Anastasiia |date=2022-07-06 |title=Emissions from mining cause 'up to £2.5tn' in environmental damages each year |url=https://www.carbonbrief.org/emissions-from-mining-cause-up-to-2-5tn-in-environmental-damages-each-year/ |access-date=2023-01-27 |website=Carbon Brief |language=en}}</ref>
Water systems are affected by coal mining.<ref>{{cite journal|title=Environmental Impact of Coal Mining on Water Regime and Its Management|author=Tiwary, R. K. |journal=Water, Air, & Soil Pollution|year=2001|volume=132|pages=185–99|doi=10.1023/a:1012083519667|bibcode=2001WASP..132..185T |s2cid=91408401 }}</ref> For example, the mining of coal affects [[groundwater]] and [[water table]] levels and acidity. Spills of fly ash, such as the [[Kingston Fossil Plant coal fly ash slurry spill]], can also contaminate land and waterways, and destroy homes. Power stations that burn coal also consume large quantities of water. This can affect the flows of rivers, and has consequential impacts on other land uses. In areas of [[water scarcity]], such as the [[Thar Desert]] in [[Pakistan]], coal mining and coal power plants contribute to the depletion of water resources.<ref>{{cite news |title=Pakistan's Coal Trap |url=https://www.dawn.com/news/1387151 |work=Dawn |date=4 February 2018}}</ref>
One of the earliest known impacts of coal on the [[water cycle]] was [[acid rain]]. In 2014, approximately 100 [[Orders of magnitude (mass)#106 to 1011 kg|Tg]]/S of [[sulfur dioxide]] (SO<sub>2</sub>) was released, over half of which was from burning coal.<ref>{{Cite journal|last1=Zhong|first1=Qirui|last2=Shen |first2=Huizhong|last3=Yun|first3=Xiao|last4=Chen|first4=Yilin|last5=Ren|first5=Yu'ang|last6=Xu |first6=Haoran|last7=Shen|first7=Guofeng|last8=Du |first8=Wei|last9=Meng|first9=Jing|last10=Li |first10=Wei|last11=Ma|first11=Jianmin|date=2020-06-02|title=Global Sulfur Dioxide Emissions and the Driving Forces|url=https://doi.org/10.1021/acs.est.9b07696|journal=Environmental Science & Technology |volume=54|issue=11|pages=6508–6517|doi=10.1021/acs.est.9b07696|pmid=32379431|bibcode=2020EnST...54.6508Z |s2cid=218556619|issn=0013-936X}}</ref> After release, the sulfur dioxide is oxidized to H<sub>2</sub>SO<sub>4</sub> which scatters solar radiation, hence its increase in the atmosphere exerts a cooling effect on the climate. This beneficially masks some of the warming caused by increased greenhouse gases. However, the sulfur is precipitated out of the atmosphere as acid rain in a matter of weeks,<ref>{{cite journal|title=The oxidation rate and residence time of sulphur dioxide in the arctic atmosphere |author1=Barrie, L.A. |author2=Hoff, R.M. |journal=Atmospheric Environment|volume=18|issue=12|year=1984 |pages=2711–2722|doi=10.1016/0004-6981(84)90337-8|bibcode=1984AtmEn..18.2711B }}</ref> whereas carbon dioxide remains in the atmosphere for hundreds of years. Release of SO<sub>2</sub> also contributes to the widespread acidification of ecosystems.<ref>Human Impacts on Atmospheric Chemistry, by PJ Crutzen and J Lelieveld, Annual Review of Earth and Planetary Sciences, Vol. 29: 17–45 (Volume publication date May 2001)</ref>
Disused coal mines can also cause issues. Subsidence can occur above tunnels, causing damage to infrastructure or cropland. Coal mining can also cause long lasting fires, and it has been estimated that thousands of [[coal seam fire]]s are burning at any given time.<ref name="Deep underground">{{cite magazine |magazine=[[Time (magazine)|Time]] |date=23 July 2010 |author=Cray, Dan |title=Deep Underground, Miles of Hidden Wildfires Rage |url=http://www.time.com/time/health/article/0,8599,2006195,00.html |archive-url= https://web.archive.org/web/20100728003147/http://www.time.com/time/health/article/0,8599,2006195,00.html |archive-date=28 July 2010 |url-status=dead}}</ref> For example, [[Brennender Berg]] has been burning since 1668, and is still burning in the 21st century.<ref name="mineralienatlas">{{cite web |title=Das Naturdenkmal Brennender Berg bei Dudweiler |trans-title=The natural monument Burning Mountain in Dudweiler |language=de |work=Mineralienatlas |access-date=3 October 2016 |url=https://www.mineralienatlas.de/?l=3741}}</ref>
The production of coke from coal produces ammonia, coal tar, and gaseous compounds as byproducts which if discharged to land, air or waterways can pollute the environment.<ref>{{cite web|title=World Of Coke: Coke is a High Temperature Fuel|url=http://www.ustimes.com/WorldOfCoke/|website=www.ustimes.com|access-date=16 January 2016|url-status=live|archive-url=https://web.archive.org/web/20151127154337/http://www.ustimes.com/WorldOfCoke/ |archive-date=27 November 2015}}</ref> The [[Whyalla steelworks]] is one example of a coke producing facility where liquid ammonia was discharged to the marine environment.<ref>{{Cite book|last1=Rajaram|first1=Vasudevan |url=https://books.google.com/books?id=5uTM2jFMzH4C&pg=PA113|title=Sustainable Mining Practices: A Global Perspective|last2=Parameswaran|first2=Krishna |last3=Dutta|first3=Subijoy|publisher=[[CRC Press]]|year=2005 |isbn=978-1-4398-3423-7|location=|pages=113}}</ref>
===Climate change===
[[File:1979- Radiative forcing - climate change - global warming - EPA NOAA.svg|thumb|upright=1.5 | The warming influence (called [[radiative forcing]]) of long-lived greenhouse gases has nearly doubled in 40 years, with carbon dioxide being the dominant driver of global warming.<ref name="NOAA_AGGI_2023">{{cite web |title=The NOAA Annual Greenhouse Gas Index (AGGI) |url=https://gml.noaa.gov/aggi/aggi.html |website=NOAA.gov |publisher=National Oceanic and Atmospheric Administration (NOAA) |archive-url=https://web.archive.org/web/20241005195609/https://gml.noaa.gov/aggi/aggi.html |archive-date=5 October 2024 |date=2024 |url-status=live }}</ref>]]
The largest and most long-term effect of coal use is the release of carbon dioxide, a [[greenhouse gas]] that causes [[climate change]]. Coal-fired power plants were the single largest contributor to the growth in global CO<sub>2</sub> emissions in 2018,<ref name="Gençsü 2019, p. 8">Gençsü (2019), p. 8</ref> 40% of the total fossil fuel emissions,<ref name="phys2018">{{cite web|url=https://phys.org/news/2018-12-china-unbridled-export-coal-power_1.html|title=China's unbridled export of coal power imperils climate goals|access-date=7 December 2018}}</ref> and more than a quarter of total emissions.<ref name="cebf" />{{refn|14.4 gigatonnes coal/50 gigatonnes total|group=note}} Coal mining can emit methane, another greenhouse gas.<ref>{{cite news |title=China's Coal Plants Haven't Cut Methane Emissions as Required, Study Finds |url=https://www.nytimes.com/2019/01/29/climate/china-coal-climate-change.html |work=[[The New York Times]] |date=29 January 2019}}</ref><ref>{{Cite web|url=https://www.carbonbrief.org/coal-mines-emit-more-methane-than-oil-and-gas-sector-study-finds|title=Coal mines emit more methane than oil-and-gas sector, study finds|last=Gabbatiss|first=Josh|date=2020-03-24|website=Carbon Brief|language=en|access-date=2020-03-29}}</ref>
In 2016 world gross [[carbon dioxide emissions]] from coal usage were 14.5 gigatonnes.<ref>{{cite web |title=Emissions |url=http://www.globalcarbonatlas.org/en/CO2-emissions |publisher=Global Carbon Atlas |access-date=6 November 2018}}</ref> For every megawatt-hour generated, coal-fired electric power generation emits around a tonne of carbon dioxide, which is double the approximately 500&nbsp;kg of carbon dioxide released by a [[natural gas]]-fired electric plant.<ref>{{cite web|title=How much carbon dioxide is produced when different fuels are burned?|work=eia.gov|url=https://www.eia.gov/tools/faqs/faq.cfm?id=73&t=11|access-date=7 January 2016|url-status=live|archive-date=12 January 2016|archive-url=https://web.archive.org/web/20160112095655/http://www.eia.gov/tools/faqs/faq.cfm?id=73&t=11}}</ref> The emission intensity of coal varies with type and generator technology and exceeds 1200&nbsp;g per kWh in some countries.<ref>{{cite journal |last1=Tranberg |first1=Bo |last2=Corradi |first2=Olivier |last3=Lajoie |first3=Bruno |last4=Gibon |first4=Thomas |last5=Staffell |first5=Iain |last6=Andresen |first6=Gorm Bruun |year=2019 |title=Real-Time Carbon Accounting Method for the European Electricity Markets |journal=Energy Strategy Reviews |volume=26 |pages=100367 |arxiv=1812.06679 |bibcode=2019EneSR..2600367T |doi=10.1016/j.esr.2019.100367 |s2cid=125361063}}</ref> In 2013, the head of the UN climate agency advised that most of the world's coal reserves should be left in the ground to avoid catastrophic global warming.<ref>{{cite news|title=Leave coal in the ground to avoid climate catastrophe, UN tells industry|url=https://www.theguardian.com/environment/2013/nov/18/leave-coal-avoid-climate-catastrophe-un|url-status=live|archive-url=https://web.archive.org/web/20170102164315/https://www.theguardian.com/environment/2013/nov/18/leave-coal-avoid-climate-catastrophe-un|archive-date=2 January 2017|newspaper=The Guardian |date=2013-11-18 |last1=Vidal|first1=John|last2=Readfearn|first2=Graham}}</ref> To keep global warming below 1.5&nbsp;°C or 2&nbsp;°C hundreds, or possibly thousands, of coal-fired power plants will need to be retired early.<ref>{{Cite web|url=https://www.nationalgeographic.com/environment/2019/07/we-have-too-many-fossil-fuel-power-plants-to-meet-climate-goals/|archive-url=https://web.archive.org/web/20190702105444/https://www.nationalgeographic.com/environment/2019/07/we-have-too-many-fossil-fuel-power-plants-to-meet-climate-goals/|url-status=dead|archive-date=2 July 2019|title=We have too many fossil-fuel power plants to meet climate goals |date=2019-07-01 |website=Environment|language=en|access-date=2019-09-30}}</ref>
===Underground fires===
{{Main|Coal-seam fire}}
Thousands of coal fires are burning around the world.<ref>{{cite web |title=Sino German Coal fire project |url=http://www.coalfire.caf.dlr.de/projectareas/world_wide_distribution_en.html |url-status=dead |archive-url=https://web.archive.org/web/20050830091254/http://www.coalfire.caf.dlr.de/projectareas/world_wide_distribution_en.html |archive-date=30 August 2005 |access-date=9 September 2005}}</ref> Those burning underground can be difficult to locate and many cannot be extinguished. Fires can cause the ground above to subside, their combustion gases are dangerous to life, and breaking out to the surface can initiate surface [[wildfire]]s. Coal seams can be set on fire by [[spontaneous combustion]] or contact with a [[mine fire]] or surface fire. Lightning strikes are an important source of ignition. The coal continues to burn slowly back into the seam until oxygen (air) can no longer reach the flame front. A grass fire in a coal area can set dozens of coal seams on fire.<ref>{{cite web |title=Committee on Resources-Index |url=http://resourcescommittee.house.gov/archives/108/testimony/johnmasterson.htm |url-status=dead |archive-url=https://web.archive.org/web/20050825231038/http://resourcescommittee.house.gov/archives/108/testimony/johnmasterson.htm |archive-date=25 August 2005 |access-date=9 September 2005}}</ref><ref>{{cite web |title=Snapshots 2003 |url=http://www.fire.blm.gov/textdocuments/6-27-03.pdf |url-status=dead |archive-url=https://web.archive.org/web/20060218013724/http://www.fire.blm.gov/textdocuments/6-27-03.pdf |archive-date=18 February 2006 |access-date=9 September 2005 |work=fire.blm.gov}}</ref> Coal fires in China burn an estimated 120 million tons of coal a year, emitting 360 million metric tons of CO<sub>2</sub>, amounting to 2–3% of the annual worldwide production of CO<sub>2</sub> from [[fossil fuel]]s.<ref>{{cite web |title=EHP 110-5, 2002: Forum |url=http://ehp.niehs.nih.gov/docs/2002/110-5/forum.html |url-status=dead |archive-url=https://web.archive.org/web/20050731081620/http://ehp.niehs.nih.gov/docs/2002/110-5/forum.html |archive-date=31 July 2005 |access-date=9 September 2005}}</ref><ref>{{cite web |title=Overview about ITC's activities in China |url=http://www.itc.nl/personal/coalfire/activities/overview.html |url-status=dead |archive-url=https://web.archive.org/web/20050616004903/http://www.itc.nl/personal/coalfire/activities/overview.html |archive-date=16 June 2005 |access-date=9 September 2005}}</ref>
==Pollution mitigation and carbon capture==
[[File:Figure_1-_Sample_Layout_of_Emissions_Controls_at_a_Coal_Power_Plant_(7315637538)_(cropped).jpg|thumb|Emissions controls at a [[coal fired power plant]]]]{{Main|Coal pollution mitigation|Carbon capture and storage}}
Systems and technologies exist to mitigate the [[Health and environmental impact of the coal industry|health and environmental impact of burning coal]] for energy.
===Precombustion treatment===
{{Main|Refined coal}}
Refined coal is the product of a coal-upgrading technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals. It is one form of several precombustion treatments and processes for coal that alter coal's characteristics before it is burned. [[Thermal efficiency]] improvements are achievable by improved pre-drying (especially relevant with high-moisture fuel such as lignite or biomass).<ref>{{cite web |title=The Niederraussem Coal Innovation Centre |url=http://www.rwe.com/web/cms/mediablob/en/234504/data/2378/5/rwe-power-ag/innovations/coal-innovation-centre/Brochure-The-Niederaussem-Coal-Innovation-Centre.pdf |url-status=live |archive-url=https://web.archive.org/web/20130722025133/http://www.rwe.com/web/cms/mediablob/en/234504/data/2378/5/rwe-power-ag/innovations/coal-innovation-centre/Brochure-The-Niederaussem-Coal-Innovation-Centre.pdf |archive-date=22 July 2013 |access-date=21 July 2014 |publisher=RWE}}</ref> The goals of precombustion coal technologies are to increase efficiency and reduce emissions when the coal is burned. Precombustion technology can sometimes be used as a supplement to postcombustion technologies to control emissions from coal-fueled boilers.
=== Post combustion approaches ===
Post combustion approaches to mitigate pollution include [[flue-gas desulfurization]], [[selective catalytic reduction]], [[electrostatic precipitators]], and [[fly ash]] reduction.
=== Carbon capture and storage ===
[[Carbon capture and storage]] (CCS) can be used to capture carbon dioxide from the [[flue gas]] of coal power plants and  bury it securely in an underground reservoir. Between 1972 and 2017, plans were made to add CCS to enough coal and gas power plants to sequester 161 million tonnes of {{chem|CO|2|}} per year, but by 2021 98% of these plans had failed.<ref name=":23">{{Cite journal |last=Kazlou |first=Tsimafei |last2=Cherp |first2=Aleh |last3=Jewell |first3=Jessica |date=October 2024 |title=Feasible deployment of carbon capture and storage and the requirements of climate targets |url=https://www.nature.com/articles/s41558-024-02104-0 |journal=Nature Climate Change |language=en |volume=14 |issue=10 |pages=1047–1055, Extended Data Fig. 1 |at= |doi=10.1038/s41558-024-02104-0 |issn=1758-6798|pmc=11458486 }}</ref>  Cost, the absence of measures to address long-term liability for stored CO<sub>2</sub>, and limited social acceptability have all contributed to project cancellations.<ref name=":122">{{Cite web |date=2023-09-26 |title=Net Zero Roadmap: A Global Pathway to Keep the 1.5 °C Goal in Reach – Analysis |url=https://www.iea.org/reports/net-zero-roadmap-a-global-pathway-to-keep-the-15-0c-goal-in-reach |access-date=2024-09-11 |website=IEA |language=en-GB}}</ref>{{Rp|pages=|page=133}} As of 2024, CCS is in operation at only four coal power plants and one gas power plant worldwide.<ref name=":21">{{Cite web |title=Global Status Report 2024 |url=https://www.globalccsinstitute.com/resources/global-status-report/ |access-date=2024-10-19 |website=Global CCS Institute |pages=57-58 |language=en-AU}}</ref>
=== "Clean coal" and "abated coal" ===
[[File:Acce-clean-coal-carolers.jpg|thumb|Coal industry groups have promoted the idea of "clean coal". In one video by the [[American Coalition for Clean Coal Electricity]], coal lumps are portrayed as characters singing carols with names like "Frosty the Coalman."<ref>{{Cite web |last=Grandia |first=Kevin |date=2008-12-09 |title=Give the gift of Asthma and a Warmer Planet this Christmas |url=https://www.desmog.com/2008/12/09/accce-clean-coal-carolers/ |access-date=2024-11-02 |website=DeSmog |language=en-US}}</ref>|alt=Cartoon of seven lumps of coal in Christmas-themed attire, standing in an open doorway with songbooks, singing. A banner says "The Clean Coal Carolers". |left]]
Since the mid-1980s, the term "clean coal" has been widely used with various meanings.<ref name=":02">{{Cite web |last=McDonald |first=Jessica |date=2018-11-09 |title=Clearing Up the Facts Behind Trump’s 'Clean Coal' Catchphrase |url=https://www.factcheck.org/2018/11/clearing-up-the-facts-behind-trumps-clean-coal-catchphrase/ |access-date=2024-10-30 |work=FactCheck.org}}</ref> Initially, "clean coal technology" referred to scrubbers and catalytic converters that reduced the pollutants that cause acid rain.<ref name=":12">{{Cite journal |last=Thorbjörnsson |first=Anders |last2=Wachtmeister |first2=Henrik |last3=Wang |first3=Jianliang |last4=Höök |first4=Mikael |date=2015-04-01 |title=Carbon capture and coal consumption: Implications of energy penalties and large scale deployment |url=https://linkinghub.elsevier.com/retrieve/pii/S2211467X14000716 |journal=Energy Strategy Reviews |series=Clean Coal Development |volume=7 |pages=18–28 |doi=10.1016/j.esr.2014.12.001 |issn=2211-467X}}</ref> The scope then expanded to include reduction of other pollutants such as mercury.<ref name=":02" /> Recently, the term has come to encompass the use of CCS to reduce greenhouse gas emissions (GHG).<ref name=":12" /> In political discourse, the phrase "clean coal" is sometimes used to suggest that coal itself can be clean.<ref name=":02" /> This suggestion is false: Technologies to mitigate emissions are implemented in the plants where coal is processed and burned, but coal as a product is intrinsically dirty.<ref name=":02" />
In discussions on greenhouse gas emissions, another common term is "abatement" of coal use. In the [[2023 United Nations Climate Change Conference]], an agreement was reached to phase down unabated coal use.<ref name=":6" /> Since the term ''abated'' was not defined, the agreement was criticized for being open to abuse.<ref name=":6">{{Cite web |last=Khourdajie |first=Alaa Al |last2=Bataille |first2=Chris |last3=Nilsson |first3=Lars J. |date=2023-12-13 |title=The COP28 climate agreement is a step backwards on fossil fuels |url=https://theconversation.com/the-cop28-climate-agreement-is-a-step-backwards-on-fossil-fuels-219753 |access-date=2024-10-01 |website=The Conversation |language=en-US}}</ref> Without a clear definition, is possible for fossil fuel use to be called "abated" if it uses CCS only in a minimal fashion, such as capturing only 30% of the emissions from a plant.<ref name=":6" />
The IPCC considers fossil fuels to be unabated if they are "produced and used without interventions that substantially reduce the amount of GHG emitted throughout the life-cycle; for example, capturing 90% or more from power plants."<ref>{{Cite web |date=4 April 2022 |title=WGIII Summary for Policymakers Headline Statements |url=https://www.ipcc.ch/report/ar6/wg3/resources/spm-headline-statements/ |access-date=2024-10-02 |website=Intergovernmental Panel on Climate Change |language=en}}</ref><ref name=":11">{{Cite web |last=Staff |first=Carbon Brief |date=2023-12-05 |title=Q&A: Why defining the ‘phaseout’ of ‘unabated’ fossil fuels is so important at COP28 |url=https://www.carbonbrief.org/qa-why-defining-the-phaseout-of-unabated-fossil-fuels-is-so-important-at-cop28/ |access-date=2024-10-02 |website=Carbon Brief |language=en}}</ref>
==Economics==
In 2018 {{USD| 80 billion}} was invested in coal supply but almost all for sustaining production levels rather than opening new mines.<ref>{{Cite web|url=https://webstore.iea.org/login?ReturnUrl=%2fdownload%2fdirect%2f2738%3ffileName%3dWEI2019.pdf&fileName=WEI2019.pdf|title=World Energy Investment 2019|website=webstore.iea.org|access-date=2019-07-14|archive-date=22 June 2020|archive-url=https://web.archive.org/web/20200622140004/https://webstore.iea.org/login?ReturnUrl=%2Fdownload%2Fdirect%2F2738%3FfileName%3DWEI2019.pdf&fileName=WEI2019.pdf|url-status=dead}}</ref>
In the long term coal and oil could cost the world trillions of dollars per year.<ref>{{Cite news|url=https://www.theguardian.com/environment/2018/dec/10/tackle-climate-or-face-financial-crash-say-worlds-biggest-investors |title=Tackle climate or face financial crash, say world's biggest investors|last=Carrington|first=Damian|date=2018-12-10|work=The Guardian|access-date=2019-07-22|language=en-GB|issn=0261-3077}}</ref><ref>{{Cite journal |last1=Kompas|first1=Tom|last2=Pham|first2=Van Ha|last3=Che|first3=Tuong Nhu|date=2018|title=The Effects of Climate Change on GDP by Country and the Global Economic Gains From Complying With the Paris Climate Accord|journal=Earth's Future|language=en|volume=6|issue=8|pages=1153–1173|doi=10.1029/2018EF000922|bibcode=2018EaFut...6.1153K|issn=2328-4277|doi-access=free|hdl=1885/265534|hdl-access=free}}</ref> Coal alone may cost Australia billions,<ref>{{cite news |title=Labor opposes plan to indemnify new coal plants and warns it could cost billions |url=https://www.theguardian.com/environment/2018/oct/24/labor-opposes-plan-to-indemnify-new-coal-plants-warns-it-could-cost-billions |work=The Guardian |date=24 October 2018}}</ref> whereas costs to some smaller companies or cities could be on the scale of millions of dollars.<ref>{{cite news |title=Superfund Scandal Leads to Prison Time for Coal Lobbyist, Lawyer |url=https://www.sierraclub.org/sierra/birmingham-superfund-scandal-leads-prison-time-for-coal-lobbyist-lawyer-drummond |publisher=Sierra Club |date=24 October 2018}}</ref> The economies most damaged by coal (via climate change) may be India and the US as they are the countries with the highest [[social cost of carbon]].<ref>{{cite journal |title=Country-level social cost of carbon |journal=Nature Climate Change |volume=8 |issue=10 |pages=895–900 |doi=10.1038/s41558-018-0282-y |bibcode=2018NatCC...8..895R |year=2018 |last1=Ricke |first1=Katharine |last2=Drouet |first2=Laurent |last3=Caldeira |first3=Ken |last4=Tavoni |first4=Massimo |hdl=11311/1099986 |s2cid=135079412 |hdl-access=free }}</ref> Bank loans to finance coal are a risk to the Indian economy.<ref name=Economist2018/>
China is the largest producer of coal in the world. It is the world's largest energy consumer, and [[coal in China]] supplies 60% of its primary energy. However two fifths of China's coal power stations are estimated to be loss-making.<ref name="CarbTrk2018" />
Air pollution from coal storage and handling costs the US almost 200 dollars for every extra ton stored, due to PM2.5.<ref>{{cite journal |title=The local air pollution cost of coal storage and handling: Evidence from U.S. power plants |journal=Journal of Environmental Economics and Management|volume=92|pages=360–396 |doi=10.1016/j.jeem.2018.09.005|year=2018|last1=Jha|first1=Akshaya|last2=Muller|first2=Nicholas Z. |bibcode=2018JEEM...92..360J |s2cid=158803149}}</ref> Coal pollution costs the {{€|43 billion}} each year.<ref>{{cite magazine |title=The human cost of coal in the UK: 1600 deaths a year|magazine=New Scientist |url=https://www.newscientist.com/article/mg22029461.800-the-human-cost-of-coal-in-the-uk-1600-deaths-a-year.html|url-status=live|archive-url=https://web.archive.org/web/20150424025154/http://www.newscientist.com/article/mg22029461.800-the-human-cost-of-coal-in-the-uk-1600-deaths-a-year.html|archive-date=24 April 2015}}</ref> Measures to cut air pollution benefit individuals financially and the economies of countries<ref>{{cite news|url=https://www.economist.com/blogs/freeexchange/2014/02/environmentalism|title=Environmentalism|date=4 February 2014|newspaper=The Economist|access-date=7 January 2016|url-status=live|archive-url=https://web.archive.org/web/20160128191945/http://www.economist.com/blogs/freeexchange/2014/02/environmentalism|archive-date=28 January 2016}}</ref><ref>{{cite web |title=Air Pollution and Health in Bulgaria |url=http://env-health.org/IMG/pdf/heal_briefing_air_bulgaria_eng.pdf |archive-url=https://web.archive.org/web/20151227144303/http://env-health.org/IMG/pdf/heal_briefing_air_bulgaria_eng.pdf |archive-date=2015-12-27 |url-status=live |publisher=HEAL |access-date=26 October 2018}}</ref> such as China.<ref>{{cite journal |title=Health-related benefits of air quality improvement from coal control in China: Evidence from the Jing-Jin-Ji region |journal=Resources, Conservation and Recycling|volume=129|pages=416–423|doi=10.1016/j.resconrec.2016.09.021 |year=2018|last1=Sun|first1=Dong|last2=Fang|first2=Jing|last3=Sun|first3=Jingqi|bibcode=2018RCR...129..416S }}</ref>
===Subsidies===
{{See also|Fossil fuel subsidies}}
Subsidies for coal in 2021 have been estimated at {{US$|19 billion}}, not including electricity subsidies, and are expected to rise in 2022.<ref>{{Cite web |title=Support for fossil fuels almost doubled in 2021, slowing progress toward international climate goals, according to new analysis from OECD and IEA - OECD |url=https://www.oecd.org/newsroom/support-for-fossil-fuels-almost-doubled-in-2021-slowing-progress-toward-international-climate-goals-according-to-new-analysis-from-oecd-and-iea.htm |access-date=2022-09-27 |website=www.oecd.org}}</ref> {{As of|2019}} [[G20]] countries provide at least {{US$|63.9 billion}}<ref name="Gençsü 2019, p. 8"/> of government support per year for the production of coal, including coal-fired power: many subsidies are impossible to quantify<ref name=ClimateTransparency2019>{{Cite web|url=https://www.climate-transparency.org/wp-content/uploads/2019/05/Managing-the-phase-out-of-coal-DIGITAL.pdf |archive-url=https://web.archive.org/web/20190524071757/https://www.climate-transparency.org/wp-content/uploads/2019/05/Managing-the-phase-out-of-coal-DIGITAL.pdf |archive-date=2019-05-24 |url-status=live|title=MANAGING THE PHASE-OUT OF COAL A COMPARISON OF ACTIONS IN G20 COUNTRIES|date=May 2019|website=Climate Transparency}}</ref> but they include {{US$|27.6 billion}} in domestic and international public finance, {{US$|15.4 billion}} in fiscal support, and {{US$|20.9 billion}} in state-owned enterprise (SOE) investments per year.<ref name="Gençsü 2019, p. 8"/> In the EU state aid to new coal-fired plants is banned from 2020, and to existing coal-fired plants from 2025.<ref>{{cite news |title=Deal reached on EU energy market design, incl end of coal subsidies License: CC0 Creative Commons |url=https://renewablesnow.com/news/deal-reached-on-eu-energy-market-design-incl-end-of-coal-subsidies-637143/ |publisher=Renewables Now |date=19 December 2018}}</ref> As of 2018, government funding for new coal power plants was supplied by [[Export–Import Bank of China|Exim Bank of China]],<ref name="Urgewald 2018">{{cite web |title=Regional Briefings for the 2018 Coal Plant Developers List |url=https://coalexit.org/sites/default/files/inline-files/Regional%20Briefings%20CPDL_10-04-2018_final.pdf |publisher=Urgewald |access-date=27 November 2018}}</ref> the [[Japan Bank for International Cooperation]] and Indian public sector banks.<ref>{{cite news |title=The World Needs to Quit Coal. Why Is It So Hard? |url=https://www.nytimes.com/2018/11/24/climate/coal-global-warming.html |archive-url=https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2018/11/24/climate/coal-global-warming.html |archive-date=2022-01-01 |url-access=limited |work=[[The New York Times]] |date=24 November 2018}}{{cbignore}}</ref> [[Energy in Kazakhstan#Coal|Coal in Kazakhstan]] was the main recipient of coal consumption subsidies totalling US$2 billion in 2017.<ref>{{cite web |title=Fossil-fuel subsidies|url=https://www.iea.org/weo/energysubsidies/ |publisher=[[International Energy Agency|IEA]] |access-date=16 November 2018}}</ref> [[coal in Turkey#Subsidies|Coal in Turkey]] benefited from substantial subsidies in 2021.<ref>{{Cite web|title=Turkey|url=https://ember-climate.org/global-electricity-review-2021/g20-profiles/turkey/|access-date=2021-10-09|website=Ember|date=28 March 2021|language=en-GB|archive-date=27 October 2021|archive-url=https://web.archive.org/web/20211027043904/https://ember-climate.org/global-electricity-review-2021/g20-profiles/turkey/|url-status=dead}}</ref>
===Stranded assets===
Some coal-fired power stations could become [[stranded assets]], for example [[China Energy Investment]], the world's largest power company, risks losing half its capital.<ref name="CarbTrk2018" /> However, state-owned electricity utilities such as [[Eskom]] in South Africa, [[Perusahaan Listrik Negara]] in Indonesia, [[Sarawak Energy]] in Malaysia, [[Taipower]] in Taiwan, [[EGAT]] in Thailand, [[Vietnam Electricity]] and [[EÜAŞ]] in Turkey are building or planning new plants.<ref name="Urgewald 2018b">{{cite web|title=Regional Briefings for the 2018 Coal Plant Developers List|url=https://coalexit.org/sites/default/files/inline-files/Regional%20Briefings%20CPDL_10-04-2018_final.pdf |access-date=27 November 2018|publisher=Urgewald}}</ref> As of 2021 this may be helping to cause a [[carbon bubble]] which could cause financial instability if it bursts.<ref>{{Cite web |url=https://cosmosmagazine.com/climate/stranded-fossil-fuel-assets-may-prompt-4-trillion-crisis|title='Stranded' fossil fuel assets may prompt {{US$|long=no|4 trillion}} crisis|website=[[Cosmos (Australian magazine)|Cosmos]] |date=4 June 2018 |access-date=2019-09-30}}</ref><ref>{{Cite web|last=Carrington|first=Damian|date=2021-09-08|title=How much of the world's oil needs to stay in the ground?|url=https://www.theguardian.com/environment/2021/sep/08/climate-crisis-fossil-fuels-ground|url-status=live|access-date=2021-09-10|website=The Guardian|language=en |archive-date=8 September 2021 |archive-url=https://web.archive.org/web/20210908153408/https://www.theguardian.com/environment/2021/sep/08/climate-crisis-fossil-fuels-ground}}</ref><ref>{{Cite journal|last1=Welsby|first1=Dan|last2=Price|first2=James |last3=Pye |first3=Steve|last4=Ekins|first4=Paul|date=2021-09-08|title=Unextractable fossil fuels in a 1.5 °C world|journal=Nature|language=en|volume=597|issue=7875|pages=230–234|doi=10.1038/s41586-021-03821-8 |pmid=34497394 |bibcode=2021Natur.597..230W|issn=1476-4687|doi-access=free}}</ref>
==Politics==
{{See also|Politics of climate change}}
Countries building or financing new coal-fired power stations, such as China, India, Indonesia, Vietnam, Turkey and Bangladesh, face mounting international criticism for obstructing the aims of the [[Paris Agreement]].<ref name="Cornot-Gandolfe 2018" /><ref>{{Cite web|url=https://www.spglobal.com/marketintelligence/en/news-insights/latest-news-headlines/5-asian-countries-building-80-of-new-coal-power-carbon-tracker-65232956|title = 5 Asian countries building 80% of new coal power – Carbon Tracker}}</ref><ref>{{Cite web|url=https://electrek.co/2021/09/14/egeb-76-of-proposed-coal-plants-have-been-canceled-since-2015/|title=EGEB: 76% of proposed coal plants have been canceled since 2015|date=14 September 2021}}</ref> In 2019, the Pacific Island nations (in particular [[Vanuatu]] and [[Fiji]]) criticized Australia for failing to cut their emissions at a faster rate than they were, citing concerns about coastal inundation and erosion.<ref name=Guardian2018>{{cite news |title=Pacific nations under climate threat urge Australia to abandon coal within 12 years |url=https://www.theguardian.com/environment/2018/dec/14/pacific-nations-under-climate-threat-urge-australia-to-abandon-coal-within-12-years |work=[[The Guardian]] |date=13 December 2018}}</ref> In May 2021, the G7 members agreed to end new direct government support for international coal power generation.<ref>{{Cite web |last=Fiona |first=Harvey |author-link=Fiona Harvey |date=2021-05-21 |title=Richest nations agree to end support for coal production overseas |url=http://www.theguardian.com/environment/2021/may/21/richest-nations-agree-to-end-support-for-coal-production-overseas |access-date=2021-05-22 |website=The Guardian |language=en}}</ref>
[[File:Coral not coal protest at India Finance Minister Arun Jaitley Visit to Australia (25563929593).jpg| right|thumb|Protesting against damage to the [[Great Barrier Reef]] caused by [[climate change in Australia]]]]
==Cultural usage==
Coal is the [[List of U.S. state minerals, rocks, stones and gemstones|official state mineral]] of [[Kentucky]],<ref>{{cite web|url=http://sos.ky.gov/kids/all/symbols/mineral.htm |title=Kentucky: Secretary of State – State Mineral |date=20 October 2009 |access-date=7 August 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110527221124/http://www.sos.ky.gov/kids/all/symbols/mineral.htm |archive-date=27 May 2011 }}</ref> and the official state rock of [[Utah]]<ref>{{cite web|title=Utah State Rock – Coal |url=http://pioneer.utah.gov/research/utah_symbols/rock.html|work=Pioneer: Utah's Online Library |publisher=Utah State Library Division|access-date=7 August 2011|url-status=live|archive-url=https://web.archive.org/web/20111002183417/http://pioneer.utah.gov/research/utah_symbols/rock.html |archive-date=2 October 2011}}</ref> and [[West Virginia]].<ref>{{Cite web |title=WVGES Frequently Asked Questions |url=https://www.wvgs.wvnet.edu/www/faq/faq.htm |access-date=2023-09-25 |website=www.wvgs.wvnet.edu |language=en}}</ref> These [[US states]] have a historic link to coal mining.
Some cultures hold that children who misbehave will receive only a lump of coal from [[Santa Claus]] for Christmas in their [[christmas stocking|stocking]]s instead of presents.
It is also customary and considered lucky in [[Scotland]] and the [[North of England]] to give coal as a gift on [[New Year's Day]]. This occurs as part of [[first-footing]] and represents warmth for the year to come.<ref name=Scotsman>{{cite web |last=Jack |first=Lauren |date=20 December 2022 |title=What is First Footing? Where the Scottish Hogmanay tradition comes from and common first footing gifts |website=scotsman.com |publisher=National World Publishing, LTD |url=https://www.scotsman.com/heritage-and-retro/heritage/what-is-first-footing-where-the-scottish-hogmanay-tradition-comes-from-and-common-first-footing-gifts-3960956 |access-date=21 November 2024 }}</ref>
==See also==
{{Portal|Geology|Energy}}
* {{annotated link|Biochar}}
* {{annotated link|Carbochemistry}}
* {{annotated link|Coal analysis}}
* {{annotated link|Coal blending}}
* {{annotated link|Coal homogenization}}
* {{annotated link|Coal measures}} (stratigraphic unit)
* {{annotated link|Health and environmental impact of the coal industry}}
* {{annotated link|Fluidized bed combustion}}
* {{annotated link|Fossil fuel phase-out}}
* {{annotated link|Gyttja|Gytta}}
* {{annotated link|Coal-mining region}}
* {{annotated link|Mountaintop removal mining}}
* {{annotated link|Subcoal}}
* {{annotated link|The Coal Question|''The Coal Question''}}
* {{annotated link|Tonstein}}
* {{annotated link|FutureCoal}}
== Notes ==
{{Reflist|group="note"}}
{{notelist}}
==References==
{{Reflist}}
==Further reading==
* {{cite book|last = Freese|first = Barbara|title = Coal: A Human History|year = 2003|publisher = Penguin Books|isbn = 978-0-7382-0400-0|oclc = 51449422|url = https://archive.org/details/coalhumanhistory00free_0}}
* {{cite book |last= Thurber |first=Mark |year=2019 |title=Coal |publisher=Polity Press |isbn=978-1509514014}}
* {{cite book |last1=Paxman |first1=Jeremy |title=Black Gold : The History of How Coal Made Britain. |date=2022 |publisher=William Collins |isbn=9780008128364}}
==External links==
{{Wikibooks |Historical Geology|Peat and coal}}
{{Wikibooks |High School Earth Science|Nonrenewable Energy Resources#Coal|Coal}}
{{Commons}}
{{Wiktionary}}
* [https://coaltransitions.org/ Coal Transitions]
* [https://www.iea.org/fuels-and-technologies/coal Coal – International Energy Agency]
* [https://coalexit.org/ CoalExit]
* [https://euracoal.eu/ European Association for Coal and Lignite]
* [http://www.worldcoal.com/ Coal news and industry magazine]
* [https://globalenergymonitor.org/projects/global-coal-plant-tracker/ Global Coal Plant Tracker]
* [https://energyandcleanair.org/ Centre for Research on Energy and Clean Air]
* {{cite EB1911|wstitle=Coal|volume=6|pages=574–93|short=1}}
* {{cite NIE|wstitle=Coal|short=1}}
* {{cite Collier's|wstitle=Coal|short=1}}
{{coal|state=expanded}}
{{Energy country lists|state=collapsed}}
{{electricity generation}}
{{Rock type}}
{{Authority control}}
[[Category:Coal| ]]
[[Category:Coal mining]]
[[Category:Economic geology]]
[[Category:Fuels]]
[[Category:Sedimentary rocks]]
[[Category:Solid fuels]]
[[Category:Fossil fuels]]