Etymology
The word originally took the form ''col'' inGeology
Coal is composed ofFormation
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 byTypes
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 ofEmission 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
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 emissionsGasification
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 withLiquefaction
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
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 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 byMarket 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
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 ResponsibilityDamage to the 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 surfaceClimate change
The largest and most long-term effect of coal use is the release of carbon dioxide, a greenhouse gas that causesPollution 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 theCorruption
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: thePeak 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