HOME

TheInfoList




Coal is a
combustible , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = German language, German , demonym = Germans, German , g ...
black or brownish-black
sedimentary rock Sedimentary rocks are types of rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compoun ...

sedimentary rock
, formed as
rock strata (Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country located mostly in the southern half of South America. Sharing the bulk of the Southern Cone with Chile to the west, the country is ...
called
coal seams Coal mining is the process of extracting coal Coal is a black or brownish-black , formed as called . Coal is mostly with variable amounts of other , chiefly , , , and . Coal is formed when dead decays into and is converted into c ...

coal seams
. Coal is mostly
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
with variable amounts of other elements, chiefly
hydrogen Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

hydrogen
,
sulfur Sulfur (in nontechnical British English: sulphur) is a with the  S and  16. It is , and lic. Under , sulfur atoms form cyclic octatomic molecules with a chemical formula . Elemental sulfur is a bright yellow, line solid at . Sul ...

sulfur
,
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
, and
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
. Coal is formed when dead
plant matter Organic matter, organic material, or natural organic matter refers to the large source of Carbon compounds, carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compo ...
decays into
peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation Vegetation is an assemblage of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the ...
and is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits of coal originate in former
wetland A wetland is a distinct ecosystem that is flooded by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (Anoxic waters, anoxic) processes prevailing, especially in the soils. ...

wetland
s—called
coal forest 250px, Etching depicting some of the most significant plants of the Carboniferous. Coal forests were the vast swathes of wetlands that covered much of the Earth's Tropics, tropical land areas during the late Carboniferous (Pennsylvanian (geology), ...
s—that covered much of the Earth's tropical land areas during the late
Carboniferous The Carboniferous ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisi ...
( Pennsylvanian) and
Permian The Permian ( ) is a and which spans 47 million years from the end of the Period million years ago (Mya), to the beginning of the Period 251.902 Mya. It is the last period of the Era; the following Triassic Period belongs to the Era. The c ...
times. However, many significant coal deposits are younger than this and originate from the
Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles and the Age of Conifers, is the second-to-last era An era is a span of time defined for the purposes of chronology or historiography, as in the regnal eras in the history of a given monarchy ...
and
Cenozoic The Cenozoic ( ; ) is Earth's current geological era An era is a span of time defined for the purposes of chronology or historiography, as in the regnal eras in the history of a given monarchy, a calendar era used for a given calendar, or the ge ...

Cenozoic
eras. Coal is primarily used as a fuel. While coal has been known and used for thousands of years, its usage was limited until the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe Continental Europe or mainland Europe is the contiguous continent A continent is any of several large landmasse ...
. With the invention of the
steam engine from Stott Park Bobbin Mill, Cumbria, England A steam engine is a heat engine In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energ ...

steam engine
, coal consumption increased. In 2020 coal supplied about a quarter of the world's
primary energy Primary energy (PE) is an energy In , energy is the that must be to a or to perform on the body, or to it. Energy is a ; the law of states that energy can be in form, but not created or destroyed. The unit of measurement in the ...
and over a third of its
electricity Electricity is the set of physical Physical may refer to: *Physical examination, a regular overall check-up with a doctor *Physical (album), ''Physical'' (album), a 1981 album by Olivia Newton-John **Physical (Olivia Newton-John song), "Physi ...
. Some
iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), forming much of Earth's and . It is the fourth most common . In its metallic state, iron ...

iron
and
steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appe ...

steel
making and other industrial processes burn coal. The extraction and use of coal causes premature deaths and illness. The use of coal damages the environment, and it is the largest
anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows: * Human imp ...
source of
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is ...

carbon dioxide
contributing to
climate change Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been previous periods of climate change, but the current changes are more rapid than any known even ...
. 14 billion tonnes of carbon dioxide was emitted by burning coal in 2020, which is 40% of the total fossil fuel emissions and over 25% of total global
greenhouse gas emissions Greenhouse gas emissions from human activities strengthen the greenhouse effect The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without th ...
. As part of the worldwide
energy transition Energy transition is a significant structural change in an energy system. Historically, these changes have been driven by the demand for and availability of different fuels. Energy transitions can also result from depletion of energy sources, fo ...
many countries have reduced or eliminated their use of coal power. The
UN Secretary General The secretary-general of the United Nations (UNSG or SG) is the chief administrative officer A chief administrative officer (CAO) is a top-tier executive who supervises the daily operations of an organization and is ultimately responsible for i ...
asked governments to stop building new coal plants by 2020. Global coal use peaked in 2013. But in China it reached higher levels than ever in 2021. To meet the
Paris Agreement The Paris Agreement (french: l'accord de Paris) is an agreement within the United Nations Framework Convention on Climate Change (UNFCCC), on climate change mitigation, Climate change adaptation, adaptation, and Climate finance, finance, signed i ...
target of keeping
global warming Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been , but the current changes are more rapid than any known events in Earth's history. The main cau ...

global warming
to below coal use needs to halve from 2020 to 2030, and phasing down coal was agreed in the Glasgow Climate Pact. The largest consumer and importer of coal is
China China (), officially the People's Republic of China (PRC; ), is a country in . It is the world's , with a of more than 1.4 billion. China spans five geographical and 14 different countries, the in the world after . Covering an area of ap ...
. China mines almost half the world's coal, followed by
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
with about a tenth.
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
accounts for about a third of world coal exports, followed by
Indonesia Indonesia ( ), officially the Republic of Indonesia ( id, Republik Indonesia, links=yes ), is a country in Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia or SEA, is t ...

Indonesia
and
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe Eastern Europe is the eastern region of . There is no consistent definition of the precise area it covers, partly because th ...
.


Etymology

The word originally took the form ''col'' in
Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language English is a West Germanic language of the Indo-European language family The Indo-European languages are a language family A language ...
, from
Proto-Germanic Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the reconstructed Reconstruction may refer to: Politics, history, and sociology *Reconstruction (law), the transfer of a company's (or several companies') business to a new ...
*''kula''(''n''), which in turn is hypothesized to come from the
Proto-Indo-European Proto-Indo-European (PIE) is the theorized common ancestor of the Indo-European language family The Indo-European languages are a language family A language is a structured system of communication used by humans, including speech ( ...
root *''g''(''e'')''u-lo-'' "live coal".
Germanic Germanic may refer to: * Germanic peoples, an ethno-linguistic group identified by their use of the Germanic languages ** List of ancient Germanic peoples and tribes * Germanic languages :* Proto-Germanic language, a reconstructed proto-language of ...

Germanic
cognates include the
Old Frisian Old Frisian was a West Germanic language spoken between the 8th and 16th centuries in the area between the Rhine ), Surselva Surselva Region is one of the eleven administrative districts Administrative division, administrative unitArticl ...
''kole'',
Middle Dutch Middle Dutch is a collective name for a number of closely related West Germanic languages, West Germanic dialects whose ancestor was Old Dutch and was spoken and written between 1150 and 1500. The language served as a minority language in the Holy ...
''cole'',
Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () *Dutch language , spoken in Belgium (also referred as ''flemish'') Dutch may also refer to:" Castle * Dutch Castle Places * ...
''kool'',
Old High German Old High German (OHG, german: Althochdeutsch, German abbr. ) is the earliest stage of the German language, conventionally covering the period from around 750 to 1050. There is no standardised or supra-regional form of German at this period, and ...
''chol'',
German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German nationality law * German language The German la ...

German
''Kohle'' and
Old Norse Old Norse, Old Nordic, or Old Scandinavian is a stage of development of North Germanic dialects before their final divergence into separate Nordic languages. Old Norse was spoken by inhabitants of Scandinavia Scandinavia; : ''Skades ...
''kol'', and the
Irish Irish most commonly refers to: * Someone or something of, from, or related to: ** Ireland, an island situated off the north-western coast of continental Europe ** Northern Ireland, a constituent unit of the United Kingdom of Great Britain and North ...
word ''gual'' is also a cognate via the
Indo-European The Indo-European languages are a language family native to western and southern Eurasia. It comprises most of the languages of Europe together with those of the northern Indian subcontinent and the Iranian Plateau. Some European languages of ...
root.


Geology

Coal is composed of
macerals A maceral is a component, organic in origin, of coal 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, ele ...
,
minerals In geology Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers ...

minerals
and water.
Fossils A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the a ...

Fossils
and
amber Amber is fossil A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was ...

amber
may be found in coal.


Formation

The conversion of dead vegetation into coal is called coalification. At various times in the geologic past, the Earth had dense forests in low-lying wetland areas. In these wetlands, the process of coalification began when dead plant matter was protected from
biodegradation Biodegradation is the breakdown of organic matter Organic matter, organic material, or natural organic matter refers to the large source of Carbon compounds, carbon-based compounds found within natural and engineered, terrestrial, and aquatic ...
and
oxidation Redox (reduction–oxidation, pronunciation: or ) is a type of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter ...

oxidation
, usually by mud or acidic water, and was converted into
peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation Vegetation is an assemblage of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the ...
. This trapped the carbon in immense
peat bog A bog or bogland is a wetland A wetland is a distinct ecosystem An ecosystem is a community (ecology), community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These Bio ...

peat bog
s that 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 in the proportion of carbon. The grade of coal produced depended on the maximum pressure and temperature reached, with
lignite Lignite, often referred to as brown coal, is a soft, brown, combustible , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official langu ...

lignite
(also called "brown coal") produced under relatively mild conditions, and
sub-bituminous coalSub-bituminous coal is a type of lower grade coal which contains 35%-45% carbon. The properties of this type are between those of lignite, the lowest grade coal, and those of bituminous coal, the second highest grade of coal. Sub-bituminous coal is p ...
,
bituminous coal Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen or asphalt. It is of higher quality than lignite and Sub-bituminous coal, Sub-bituminous coal, but of poorer quality than anthracite. Formation ...

bituminous coal
, or
anthracite Anthracite, also known as hard coal, is a hard, compact variety of coal that has a lustre (mineralogy)#Submetallic lustre, submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of ...

anthracite
(also called "hard coal" or "black coal") produced in turn with increasing temperature and pressure. Of the factors involved in coalification, temperature is much more important than either pressure or time of burial. Subbituminous coal can form at temperatures as low as while anthracite requires a temperature of at least . Although coal is known from most geologic periods, 90% of all coal beds were deposited in the
Carboniferous The Carboniferous ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisi ...
and
Permian The Permian ( ) is a and which spans 47 million years from the end of the Period million years ago (Mya), to the beginning of the Period 251.902 Mya. It is the last period of the Era; the following Triassic Period belongs to the Era. The c ...
periods, which represent just 2% of the Earth's geologic history. Paradoxically, this was during the Late Paleozoic icehouse, a time of global
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the o ...

glaciation
. However, the drop in global sea level accompanying the glaciation exposed
continental shelf A continental shelf is a portion of a continent A continent is any of several large landmass A landmass, or land mass, is a large region In geography Geography (from Greek: , ''geographia'', literally "earth descriptio ...

continental shelf
s that had previously been submerged, and to these were added wide
river delta A river delta is a landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the ...

river delta
s produced by increased
erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific ...

erosion
due to the drop in
base level In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the processe ...
. These widespread areas of wetlands provided ideal conditions for coal formation. The rapid formation of coal ended with the coal gap in the
Permian–Triassic extinction event The Permian–Triassic extinction event, also known as the P–Tr extinction, the P–T extinction, the End-Permian Extinction, and colloquially as the Great Dying, formed the boundary between the Permian The Permian ( ) is a geologic period ...
, where coal is rare. Favorable geography alone does not explain the extensive Carboniferous coal beds. Other factors contributing to rapid coal deposition were high
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
levels, above 30%, that promoted intense
wildfire A wildfire, bushfire, wildland fire or rural fire is an unplanned, unwanted, uncontrolled fire BBQ. Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction ...

wildfire
s and formation of
charcoal Charcoal is a lightweight black carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 perc ...

charcoal
that was all but indigestible by decomposing organisms; high
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is ...

carbon dioxide
levels that promoted plant growth; and the nature of Carboniferous forests, which included
lycophyte The lycophytes, when broadly circumscribed, are a vascular plant (tracheophyte) subgroup of the kingdom Plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a process used by plants and ot ...
trees whose determinate growth meant that carbon was not tied up in
heartwood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plant A woody plant is a plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a p ...

heartwood
of living trees for long periods. One theory suggested that about 360 million years ago, some plants evolved the ability to produce
lignin Lignin is a class of complex organic polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese business group, and its s ...

lignin
, a complex polymer that made their
cellulose Cellulose is an organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior ...

cellulose
stems much harder and more woody. The ability to produce lignin led to the evolution of the first
trees In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organiz ...

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. However, a 2016 study largely refuted this idea, finding extensive evidence of lignin degradation during the Carboniferous, and that shifts in lignin abundance had no impact on coal formation. They suggested that climatic and tectonic factors were a more plausible explanation. 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 A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation In meteorology Meteorology is a branch of the (which include and ), with a major focus on . The study of meteorology ...

monsoon
climate. This is necessary for the preservation of peat in coal swamps. Coal is known from
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologi ...

Precambrian
strata, which predate land plants. This coal is presumed to have originated from residues of algae. Sometimes coal seams (also known as coal beds) are interbedded with other sediments in a cyclothem. Cyclothems are thought have their origin in
glacial cycle#REDIRECT Ice age#REDIRECT Ice age {{Redirect category shell, 1= {{R from move {{R from ambiguous term {{R from other capitalisation {{R unprintworthy ...
{{Redirect category shell, 1= {{R from move {{R from ambiguous term {{R from other ca ...
s that produced fluctuations in
sea level Mean sea level (MSL) (often shortened to sea level) is an average In colloquial, ordinary language, an average is a single number taken as representative of a list of numbers, usually the sum of the numbers divided by how many numbers are in th ...

sea level
, which alternately exposed and then flooded large areas of continental shelf.


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. 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. This implies that chemical processes during coalification must remove most of the oxygen and much of the hydrogen, leaving carbon, a process called ''carbonization''. Carbonization proceeds primarily by
dehydration In physiology, dehydration is a lack of total body water In physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies ...
,
decarboxylation Decarboxylation is a chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical A chemical substance is a form of matter having constant ...

decarboxylation
, and demethanation. Dehydration removes water molecules from the maturing coal via reactions such as :2 R–OH → R–O–R + H2O :2 R-CH2-O-CH2-R → R-CH=CH-R + H2O Decarboxylation removes carbon dioxide from the maturing coal and proceeds by reaction such as :RCOOH → RH + CO2 while demethanation proceeds by reaction such as :2 R-CH3 → R-CH2-R + CH4 :R-CH2-CH2-CH2-R → R-CH=CH-R + CH4 In each of 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. 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 In organic chemistry Organic chemistry is a branch of chemistry that studies the structure, properties and reactions of organic compounds, which contain carbon in covalent bonding.Clayden, J.; Greeves, N. and Warren, S. (2012) ''Organic Chemistr ...
s (carbon compounds characterized by chains of carbon atoms) are replaced by
aromatic compound Aromatic compounds are those chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held tog ...
s (carbon compounds characterized by rings of carbon atoms) and aromatic rings begin to fuse into polyaromatic compounds (linked rings of carbon atoms). The structure increasingly resembles
graphene Graphene () is an allotrope of carbon Carbon Carbon (from la, carbo "coal") is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an ...

graphene
, the structural element of graphite. Chemical changes are accompanied by physical changes, such as decrease in average pore size. The macerals (organic particles) of lignite are composed of ''huminite'', which is earthy in appearance. As the coal matures to sub-bituminous coal, huminite begins to be replaced by vitreous (shiny) ''vitrinite''. Maturation of bituminous coal is characterized by ''bitumenization'', in which part of the coal is converted to
bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous The viscosity of a fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or externa ...

bitumen
, a hydrocarbon-rich gel. 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.


Types

As geological processes apply
pressure Pressure (symbol: ''p'' or ''P'') is the force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mass to change its velocity (e.g. moving fr ...

pressure
to dead
biotic material Biotic material or biological derived material is any material that originates from living organisms. Most such materials contain carbon Carbon (from la, carbo "coal") is a chemical element Image:Simple Periodic Table Chart-blocks.svg, ...
over time, under suitable conditions, its
metamorphic grade upright=1.35, Schematic representation of a metamorphic reaction. Abbreviations of minerals: act = actinolite; chl = Chlorite group">chlorite The chlorite ion, or chlorine dioxide anion An ion () is a particle, atom or molecule with a ...
or rank increases successively into: *
Peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation Vegetation is an assemblage of species and the they provide. It is a general term, without specific reference to particular , life forms, structure, ...
, a precursor of coal *
Lignite Lignite, often referred to as brown coal, is a soft, brown, combustible , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official langu ...

Lignite
, or brown coal, the lowest rank of coal, most harmful to health, used almost exclusively as fuel for electric power generation ** Jet, a compact form of lignite, sometimes polished; used as an ornamental stone since the
Upper Palaeolithic The Upper Paleolithic (or Upper Palaeolithic) also called the Late Stone Age is the third and last subdivision of the Paleolithic The Paleolithic or Palaeolithic or Palæolithic (), also called the Old Stone Age, is a period in human prehis ...

Upper Palaeolithic
*
Sub-bituminous coalSub-bituminous coal is a type of lower grade coal which contains 35%-45% carbon. The properties of this type are between those of lignite, the lowest grade coal, and those of bituminous coal, the second highest grade of coal. Sub-bituminous coal is p ...
, whose properties range between those of lignite and those of bituminous coal, is used primarily as fuel for steam-electric power generation. *
Bituminous coal Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen or asphalt. It is of higher quality than lignite and Sub-bituminous coal, Sub-bituminous coal, but of poorer quality than anthracite. Formation ...

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. Known as steam coal in the UK, and historically used to raise steam in steam locomotives and ships *
Anthracite Anthracite, also known as hard coal, is a hard, compact variety of coal that has a lustre (mineralogy)#Submetallic lustre, submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of ...

Anthracite
, the highest rank of coal, is a harder, glossy black coal used primarily for residential and commercial
space heating A space heater is a device used to heat a single, small area; central heating is used to heat many connected areas, such as the rooms of a house. Space heaters are powered by electricity Electricity is the set of physical phenomena associ ...
. *
Graphite Graphite (), archaically referred to as plumbago, is a Crystallinity, crystalline form of the element carbon with its atoms arranged in a Hexagonal crystal system, hexagonal structure. It occurs naturally in this form and is the most stable for ...

Graphite
is difficult to ignite and not commonly used as fuel; it is most used in pencils, or powdered for
lubrication Lubrication is the process or technique of using a lubricant A lubricant is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the f ...
. *
Cannel coal Cannel coal or candle coal is a type of bituminous coal Image:Coal bituminous.jpg, 275px, Bituminous coal Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen or asphalt. It is of higher quality th ...
(sometimes called "candle coal") is a variety of fine-grained, high-rank coal with significant hydrogen content, which consists primarily of
liptiniteIn coal geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the proces ...
. There are several international standards for coal. The classification of coal is generally based on the content of
volatiles Volatiles are the group of chemical elements and chemical compounds that can be readily Volatility (chemistry), vaporized. In contrast with volatiles, elements and compounds that are not readily vaporized are known as Refractory (planetary scien ...
. 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 Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appe ...

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.


History

The earliest recognized use is from the Shenyang area of China where by 4000 BC Neolithic inhabitants had begun carving ornaments from black lignite. Coal from the Fushun mine in northeastern China was used to smelt copper as early as 1000 BC. Marco Polo, the Italian who traveled to China in the 13th century, described coal as "black stones ... which burn like logs", and said coal was so plentiful, people could take three hot baths a week. 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): Outcrop coal was used in Britain during the Bronze Age (3000–2000 BC), where it formed part of funeral pyres.Britannica 2004: ''Coal mining: ancient use of outcropping coal'' 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". 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. 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. Evidence of coal's use for iron-working in the city during the Roman period has been found. In Eschweiler, Rhineland, deposits of
bituminous coal Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen or asphalt. It is of higher quality than lignite and Sub-bituminous coal, Sub-bituminous coal, but of poorer quality than anthracite. Formation ...

bituminous coal
were used by the Romans for the smelting of iron ore. No evidence exists of coal being of great importance in Britain before about AD 1000, the High Middle Ages. 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. 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, 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. In 1257–1259, coal from Newcastle upon Tyne was shipped to London for the metalsmith, smiths and lime (material), lime-burners building Westminster Abbey. Seacoal Lane and Newcastle Lane, where coal was unloaded at wharves along the River Fleet, still exist. 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 adits was developed. The alternative name was "pitcoal", because it came from mines. 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. Historian Ruth Goodman (historian), Ruth Goodman has traced the socioeconomic effects of that switch and its later spread throughout Britain and suggested that its importance in shaping the industrial adoption of coal has been previously underappreciated. The development of the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe Continental Europe or mainland Europe is the contiguous continent A continent is any of several large landmasse ...
led to the large-scale use of coal, as the
steam engine from Stott Park Bobbin Mill, Cumbria, England A steam engine is a heat engine In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energ ...

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. In 1947 there were some 750,000 miners in Britain but the last deep coal mine in the UK closed in 2015. A grade between bituminous coal and anthracite was once known as "steam coal" as it was widely used as a fuel for steam locomotives. In this specialized use, it is sometimes known as "sea coal" in the United States. Small "steam coal", also called ''dry small steam nuts'' (or 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. 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.


Emission intensity

Emission intensity is the Life-cycle greenhouse-gas emissions of energy sources, greenhouse gas emitted over the life of a generator per unit of electricity generated. The emission intensity of coal power stations is high, as they emit around 1000g of CO2eq for each kWh generated, while natural gas is medium-emission intensity at around 500g CO2eq per kWh. The emission intensity of coal varies with type and generator technology and exceeds 1200g per kWh in some countries.


Energy density

The energy density of coal is roughly 24 megajoules per kilogram (approximately 6.7 kilowatt-hours per kg). For a coal power plant with a 40% efficiency, it takes an estimated of coal to power a 100 W lightbulb for one year. 27.6% of world energy was supplied by coal in 2017 and Asia used almost three quarters of it.


Chemistry


Composition

The composition of coal is reported either as a proximate analysis (moisture, volatile matter, fixed carbon, and ash) or an ultimate analysis (ash, carbon, hydrogen, nitrogen, oxygen, and sulfur). The "volatile matter" does not exist by itself (except for some adsorbed methane) but designates the volatile compounds that are produced and driven off by heating the coal. A typical bituminous coal may have an ultimate analysis 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. The composition of ash, given in terms of oxides, varies: Other minor components include:


Coking coal and use of coke to smelt iron

Coke is a solid carbonaceous residue derived from coking coal (a low-ash, low-sulfur bituminous coal, also known as ''metallurgical coal''), which is used in manufacturing
steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appe ...

steel
and other iron products. Coke is made from coking coal by baking in an oven without oxygen at temperatures as high as 1,000 °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. The carbon monoxide produced by its combustion reduces hematite (an iron oxide) to
iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), forming much of Earth's and . It is the fourth most common . In its metallic state, iron ...

iron
. Waste carbon dioxide is also produced together with pig iron, which is too rich in dissolved carbon so must be treated further to make steel. Coking coal should be low in ash,
sulfur Sulfur (in nontechnical British English: sulphur) is a with the  S and  16. It is , and lic. Under , sulfur atoms form cyclic octatomic molecules with a chemical formula . Elemental sulfur is a bright yellow, line solid at . Sul ...

sulfur
, and phosphorus, so that these do not migrate to the metal. 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 cokemaking 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.


Use in foundry components

Finely ground bituminous coal, known in this application as sea coal, is a constituent of foundry sand. While the molten metal is in the Molding (process), mould, the coal burns slowly, releasing Reducing agent, reducing gases at pressure, and so preventing the metal from penetrating the pores of the sand. It is also contained in 'mould wash', a paste or liquid with the same function applied to the mould before casting. Sea coal can be mixed with the clay lining (the "bod") used for the bottom of a cupola furnace. When heated, the coal decomposes and the bod becomes slightly friable, easing the process of breaking open holes for tapping the molten metal.


Alternatives to coke

Scrap steel can be recycled in an electric arc furnace; and an alternative to making iron by smelting is direct reduced iron, where any carbonaceous fuel can be used to make sponge or pelletised iron. To lessen carbon dioxide emissions
hydrogen Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

hydrogen
can be used as the reducing agent and biomass or waste as the source of carbon. Historically, charcoal has been used as an alternative to coke in a blast furnace, with the resultant iron being known as charcoal iron.


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 (H2) 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. 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. During gasification, the coal is mixed with
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

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 Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

hydrogen
gas (H2). 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'') + O2 + H2O → H2 + 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 + H2O → CO2 + H2


Liquefaction

Coal can be converted directly into synthetic fuels equivalent to gasoline or diesel by hydrogenation or carbonization. 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. State owned China Energy Investment runs a coal liquefaction plant and plans to build 2 more. Coal liquefaction may also refer to the cargo hazard when shipping coal.


Production of chemicals

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 Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

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. 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. Much coal to chemical production is in China where coal dependent provinces such as Shanxi are struggling to control its pollution.


Electricity generation


Precombustion treatment

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). 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.


Power plant combustion

Coal burnt as a solid fuel in list of coal power stations, coal power stations to electricity generation, generate electricity is called thermal coal. Coal is also used to produce very high temperatures through combustion. Early deaths due to air pollution 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. Efforts around the world to reduce the use of coal have led some regions to switch to natural gas and electricity from lower carbon sources. When coal is used for electricity generation, it is usually pulverized and then burned in a furnace with a boiler (see also Pulverized coal-fired boiler).Total World Electricity Generation by Fuel (2006)
. Source: IEA 2008.
The furnace heat converts boiler water to steam, which is then used to spin turbines which turn electrical generator, generators and create electricity. 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. 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%. IGCC power plants emit less local pollution than conventional pulverized coal-fueled plants; however the technology for carbon capture and storage after gasification and before burning has so far proved to be too expensive to use with coal. 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. In 2018 global installed capacity was 2terawatt, TW (of which 1TW is in China) which was 30% of total electricity generation capacity. The most dependent major country is South Africa, with over 80% of its electricity generated by coal; but China alone generates more than half of the world's coal-generated electricity. peak coal, Maximum use of coal was reached in 2013. In 2018 coal-fired power station capacity factor averaged 51%, that is they operated for about half their available operating hours.


Coal industry


Mining

About 8000 Mt of coal are produced annually, about 90% of which is hard coal and 10% lignite. just over half is from underground mines. 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. 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.


As a traded commodity

China mines almost half the world's coal, followed by
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
with about a tenth.
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
accounts for about a third of world coal exports, followed by
Indonesia Indonesia ( ), officially the Republic of Indonesia ( id, Republik Indonesia, links=yes ), is a country in Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia or SEA, is t ...

Indonesia
and
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe Eastern Europe is the eastern region of . There is no consistent definition of the precise area it covers, partly because th ...
; while the largest importers are Energy in Japan, Japan and India. The price of metallurgical coal is volatile and much higher than the price of thermal coal because metallurgical coal must be lower in sulfur and requires more cleaning. 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 (see Cost of electricity by source). However, for China this is forecast for the early 2020s and for south-east Asia not until the late 2020s. In India building new plants is uneconomic and, despite being subsidized, existing plants are losing market share to renewables.


Market trends

Of the List of countries by coal production, countries which produce coal China mines by far the most, almost half the world's coal, followed by less than 10% by India. China is also by far the largest consumer. Therefore, market trends depend on Energy policy of China, Chinese energy policy. Although the effort to reduce pollution 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.


Major producers

Countries with annual production higher than 300 million tonnes are shown.


Major consumers

Countries with annual consumption higher than 500 million tonnes are shown. Shares are based on data expressed in tonnes oil equivalent.


Major exporters

Exporters are at risk of a reduction in import demand from India and China.


Major importers


Damage to human health

The use of coal as fuel causes ill health and deaths. Mining and processing of coal causes air and water pollution. Coal-powered plants emit nitrogen oxides, sulfur dioxide, particulate pollution and heavy metals, which adversely affect human health. 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, mostly in India and China. Burning coal is a major emitter of sulfur dioxide, which creates PM2.5 particulates, the most dangerous form of air pollution. 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.Coal Pollution Damages Human Health at Every Stage of Coal Life Cycle, Reports Physicians for Social Responsibility
. ''Physicians for Social Responsibility''. psr.org (18 November 2009)
Annual health costs in Europe from use of coal to generate electricity are estimated at up to €43 billion. In China, improvements to air quality and human health would increase 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. 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." Breathing in coal dust causes coalworker's pneumoconiosis or "black lung", so-called because the coal dust literally turns the lungs black from their usual pink color. In the United States 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. 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. Around 10% of coal is ash: coal ash is hazardous and toxic to human beings and some other living things. 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.


Damage to the environment

Coal mining and coal fueling of power stations and industrial processes can cause major environmental damage. Water systems are affected by coal mining. For example, mining 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 would use significant quantities of water. 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 (SO2) was released, over half of which was from burning coal. After release, the sulfur dioxide is oxidized to H2SO4 which scatters solar radiation, hence its increase in the atmosphere exerts a cooling effect on 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, whereas carbon dioxide remains in the atmosphere for hundreds of years. Release of SO2 also contributes to the widespread acidification of ecosystems. 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 fires are burning at any given time. For example, Brennender Berg has been burning since 1668 and is still burning in the 21st century. The production of coke from coal produces ammonia, coal tar, and gaseous compounds as by-products which if discharged to land, air or waterways can pollute the environment. The Whyalla steelworks is one example of a coke producing facility where liquid ammonia was discharged to the marine environment.


Underground fires

Thousands of coal fires are burning around the world. 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 A wildfire, bushfire, wildland fire or rural fire is an unplanned, unwanted, uncontrolled fire BBQ. Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction ...

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. Coal fires in China burn an estimated 120 million tons of coal a year, emitting 360 million metric tons of CO2, amounting to 2–3% of the annual worldwide production of CO2 from fossil fuels. In Centralia, Pennsylvania (a Borough (Pennsylvania), borough located in the Coal Region of the United States), an exposed vein of anthracite ignited in 1962 due to a trash fire in the borough landfill, located in an abandoned anthracite coal, anthracite Surface mining, strip mine pit. Attempts to extinguish the fire were unsuccessful, and it Centralia mine fire, continues to burn underground to this day. The Australian Burning Mountain was originally believed to be a volcano, but the smoke and ash come from a coal fire that has been burning for some 6,000 years. At Kuh i Malik in Yagnob Valley, Tajikistan, coal deposits have been burning for thousands of years, creating vast underground labyrinths full of unique minerals, some of them very beautiful. The reddish siltstone rock that caps many ridges and buttes in the Powder River Basin in Wyoming and in western North Dakota is called ''porcelanite'', which resembles the coal burning waste "clinker" or volcanic "scoria". Clinker is rock that has been fused by the natural burning of coal. In the Powder River Basin approximately 27 to 54 billion tons of coal burned within the past three million years. Wild coal fires in the area were reported by the Lewis and Clark Expedition as well as explorers and settlers in the area.


Climate change

The largest and most long-term effect of coal use is the release of carbon dioxide, a greenhouse gas that causes
climate change Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been previous periods of climate change, but the current changes are more rapid than any known even ...
. Coal-fired power plants were the single largest contributor to the growth in global CO2 emissions in 2018,Gençsü (2019), p. 8 40% of the total fossil fuel emissions, and more than a quarter of total emissions. Coal mining can emit methane, another greenhouse gas. In 2016 world gross carbon dioxide emissions from coal usage were 14.5 gigatonnes. For every megawatt-hour generated, coal-fired electric power generation emits around a tonne of carbon dioxide, which is double the approximately 500 kg of carbon dioxide released by a natural gas-fired electric plant. 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. To keep global warming below 1.5 °C or 2 °C hundreds, or possibly thousands, of coal-fired power plants will need to be retired early.


Pollution mitigation


Standards

Local pollution standards include GB13223-2011 (China), India, the Industrial Emissions Directive (EU) and the Clean Air Act (United States).


Satellite monitoring

Satellite monitoring is now used to crosscheck national data, for example Sentinel-5 Precursor has shown that Chinese control of SO2 has only been partially successful. It has also revealed that low use of technology such as SCR has resulted in high NO2 emissions in South Africa and India.


Combined cycle power plants

A few Integrated gasification combined cycle (IGCC) coal-fired power plants have been built with coal gasification. Although they burn coal more efficiently and therefore emit less pollution, the technology has not generally proved economically viable for coal, except possibly in Japan although this is controversial.


Carbon capture and storage

Although still being intensively researched and considered economically viable for some uses other than with coal; carbon capture and storage has been tested at the Petra Nova and Boundary Dam Power Station, Boundary Dam coal-fired power plants and has been found to be technically feasible but not economically viable for use with coal, due to reductions in the cost of solar PV technology.


Economics

In 2018 USD 80 billion was invested in coal supply but almost all for sustaining production levels rather than opening new mines. In the long term coal and oil could cost the world trillions of dollars per year. Coal alone may cost Australia billions, whereas costs to some smaller companies or cities could be on the scale of millions of dollars. 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. Bank loans to finance coal are a risk to the Indian economy. 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. Air pollution from coal storage and handling costs the USA almost 200 dollars for every extra ton stored, due to PM2.5. Coal pollution costs the EU €43 billion each year. Measures to cut air pollution benefit individuals financially and the economies of countries such as China.


Subsidies

Broadly defined total subsidies for coal in 2015 have been estimated at around US$2.5 trillion, about 3% of global GDP. G20 countries provide at least US$63.9 billion of government support per year for the production of coal, including coal-fired power: many subsidies are impossible to quantify 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. In the EU state aid to new coal-fired plants is banned from 2020, and to existing coal-fired plants from 2025. As pf 2018, government funding for new coal power plants was supplied by Exim Bank of China, the Japan Bank for International Cooperation and Indian public sector banks. Energy in Kazakhstan#Coal, Coal in Kazakhstan was the main recipient of coal consumption subsidies totalling US$2 billion in 2017. coal in Turkey#Subsidies, Coal in Turkey benefited from substantial subsidies in 2021.


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. 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. As of 2021 this may be helping to cause a carbon bubble which could cause financial instability if it bursts.


Politics

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 The Paris Agreement (french: l'accord de Paris) is an agreement within the United Nations Framework Convention on Climate Change (UNFCCC), on climate change mitigation, Climate change adaptation, adaptation, and Climate finance, finance, signed i ...
. 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. In May 2021, the G7 members agreed to end new direct government support for international coal power generation.


Corruption

Allegations of corruption are being investigated in India and China.


Opposition to coal

Opposition to coal pollution was one of the main reasons the modern environmental movement started in the 19th century.


Transition away from coal

In order to meet global climate goals and provide power to those that don't currently have it coal power must be reduced from nearly 10,000 TWh to less than 2,000 TWh by 2040. Phasing out coal has short-term health and environmental benefits which exceed the costs, but some countries still favor coal, and there is much disagreement about how quickly it should be phased out. However many countries, such as the Powering Past Coal Alliance, have already or are transitioned away from coal; the largest transition announced so far being Germany, which is due to shut down its last coal-fired power station between 2035 and 2038. Some countries use the ideas of a "Just Transition", for example to use some of the benefits of transition to provide early pensions for coal miners. However low-lying Pacific Islands are concerned the transition is not fast enough and that they will be inundated by sea level rise; so they have called for OECD countries to completely phase out coal by 2030 and other countries by 2040. In 2020, although China built some plants, globally more coal power was retired than built: the
UN Secretary General The secretary-general of the United Nations (UNSG or SG) is the chief administrative officer A chief administrative officer (CAO) is a top-tier executive who supervises the daily operations of an organization and is ultimately responsible for i ...
has also said that OECD countries should stop generating electricity from coal by 2030 and the rest of the world by 2040. Phasing down coal was agreed at COP26 in the Glasgow Climate Pact.


Peak coal


Switch to cleaner fuels and lower carbon electricity generation

Coal-fired generation puts out about twice as much carbon dioxide—around a tonne for every megawatt hour generated—as electricity generated by burning natural gas at 500 kg of greenhouse gas per megawatt hour. In addition to generating electricity, natural gas is also popular in some countries for heating and as an Natural gas vehicle, automotive fuel. The use of Energy in the United Kingdom, coal in the United Kingdom declined as a result of the development of North Sea oil and the subsequent dash for gas during the 1990s. In Canada some Thermal power station, coal power plants, such as the Hearn Generating Station, switched from coal to natural gas. In 2017, coal power in the United States provided 30% of the electricity, down from approximately 49% in 2008, due to plentiful supplies of low cost natural gas obtained by hydraulic fracturing of tight shale formations.


Coal regions in transition

Some coal-mining regions are highly dependent on coal.


Employment

Some coal miners are concerned their jobs may be lost in the transition. A just transition from coal is supported by the European Bank for Reconstruction and Development.


Bioremediation

The white rot fungus ''Trametes versicolor'' can grow on and metabolize naturally occurring coal. The bacteria Diplococcus has been found to degrade coal, raising its temperature.


Cultural usage

Coal is the List of U.S. state minerals, rocks, stones and gemstones, official state mineral of Kentucky and the official state rock of Utah; both U.S. 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 stockings 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.


See also

* * * * * * * (stratigraphic unit) * * * * * * * * * * * *


References


Sources

*


Notes


Further reading

* *


External links


Coal Transitions

World Coal Association

Coal – International Energy Agency

Coal Online – International Energy Agency

Coal Research at the National Energy Technology Laboratory

CoalExit

European Association for Coal and Lignite

Coal news and industry magazine

Global Coal Plant Tracker

Centre for Research on Energy and Clean Air
* * * {{Authority control Coal, Coal mining Economic geology Fuels Sedimentary rocks Solid fuels