Coal

Coal  —  Sedimentary Rock  — Anthracite coal Composition Primary carbon Secondary sulfur, hydrogen, oxygen, nitrogen Example chemical structure of coal

Coal is a readily combustible black or brownish-black sedimentary rock normally occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon along with variable quantities of other elements, chiefly sulfur, hydrogen, oxygen and nitrogen^{[citation needed]}.

Coal begins as layers of plant matter accumulate at the bottom of a body of water. For the process to continue the plant matter must be protected from biodegradation and oxidization, usually by mud or acidic water. The wide shallow seas of the Carboniferous period provided such conditions. This trapped atmospheric carbon in the ground in immense peat bogs that eventually were covered over and deeply buried by sediments under which they metamorphosed into coal. Over time, the chemical and physical properties of the plant remains (believed to mainly have been fern-like species antedating more modern plant and tree species) were changed by geological action to create a solid material.

Coal, a fossil fuel, is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide anthropogenic sources of carbon dioxide emissions. Gross carbon dioxide emissions from coal usage are slightly more than those from petroleum and about double the amount from natural gas.^[1] Coal is extracted from the ground by mining, either underground by shaft mining through the seams or in open pits.

[edit] Types

Believed approximate position of the proto-continents toward the end of the Carboniferous period; the light blue represents shallow seas where many of today's coal deposits are found, as opposed to deeper waters which gave rise to oil-bearing rocks derived from marine species. The ice caps were known to be very large, lowering sea levels extensively by locking up oceanic waters into solid ice, though how large the ice caps became is a matter of debate.

As geological processes apply pressure to dead biotic material over time, under suitable conditions it is transformed successively into

• Peat, considered to be a precursor of coal, has industrial importance as a fuel in some regions, for example, Ireland and Finland. In its dehydrated form, peat is a highly effective absorbent for fuel and oil spills on land and water
• Lignite, also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation. Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Iron Age
• Sub-bituminous coal, whose properties range from those of lignite to those of bituminous coal are used primarily as fuel for steam-electric power generation. Additionally, it is an important source of light aromatic hydrocarbons for the chemical synthesis industry.
• Bituminous coal, dense mineral, black but sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke
• Steam coal is a grade between bituminous coal and anthracite, once widely used as a fuel for steam locomotives. In this specialized use it is sometimes known as sea-coal in the U.S.^[2] Small steam coal (dry small steam nuts or DSSN) was used as a fuel for domestic water heating
• Anthracite, the highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating. It may be divided further into metamorphically altered bituminous coal and petrified oil, as from the deposits in Pennsylvania
• Graphite, technically the highest rank, but difficult to ignite and is not so commonly used as fuel: it is mostly used in pencils and, when powdered, as a lubricant.

The classification of coal is generally based on the content of volatiles. However, the exact classification varies between countries. According to the German classification, coal is classified as follows:^[3]

The middle six grades in the table represent a progressive transition from the English-language sub-bituminous to bituminous coal, while the last class is an approximate equivalent to anthracite, but more inclusive (the U.S. anthracite has < 6% volatiles).

Cannel coal (sometimes called "candle coal"), is a variety of fine-grained, high-rank coal with significant hydrogen content. It consists primarily of "exinite" macerals, now termed "liptinite".

[edit] Early uses as fuel

Chinese coal miners in an illustration of the Tiangong Kaiwu encyclopedia, published in 1637

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):

Among the materials that are dug because they are useful, those known as coals are made of earth, and, once set on fire, they burn like charcoal. They are found in Liguria… and in Elis as one approaches Olympia by the mountain road; and they are used by those who work in metals.^[4]

Outcrop coal was used in Britain during the Bronze Age (3000–2000 BC), where it has been detected as forming part of the composition of funeral pyres.^[5][6] In Roman Britain, with the exception of two modern fields, "the Romans were exploiting coals in all the major coalfields in England and Wales by the end of the second century AD".^[7] Evidence of trade in coal (dated to about AD 200) has been found at the inland port of Heronbridge, near Chester, and in the Fenlands of East Anglia, where coal from the Midlands was transported via the Car Dyke for use in drying grain.^[8] Coal cinders have been found in the hearths of villas and military 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) although in fact easily accessible surface coal from what became the Somerset coalfield was in common use in quite lowly dwellings locally.^[9] Evidence of coal's use for iron-working in the city during the Roman period has been found.^[10] In Eschweiler, Rhineland, deposits of bituminous coal were used by the Romans for the smelting of iron ore.^[7]

There is no evidence that the product was of great importance in Britain before the High Middle Ages, after about AD 1000.^[11] Mineral coal came to be referred to as "seacoal," probably because it came to many places in eastern England, including London, by sea, but the origin of the term seems to predate this, being used for coal having fallen from the exposed coal seams on cliffs above the shore or washed out of underwater coal seam outcrops.^[11] (See Industrial processes below for modern uses of the term.) These easily accessible sources had largely become exhausted (or could not meet the growing demand) by the 13th century, when underground mining from shafts or adits was developed.^[5] In 1257–59, coal from Newcastle was shipped to London for the smiths and lime-burners building Westminster Abbey.^[11] In London, there is still a Seacoal Lane and a Newcastle Lane (from the coal-shipping city of Newcastle) where, in the seventeenth century, coal was unloaded at wharves along the River Fleet.^[12] An alternative name was "pitcoal," because it came from mines. It was, however, the development of the Industrial Revolution that led to the large-scale use of coal, as the steam engine took over from the water wheel. In 1700, 5/6 of the world's coal was mined in Britain. Without coal, Britain would have run out of suitable sites for watermills by the 1830s.^[13] In 1947, there were some 750,000 miners,^[14] but by 2004 this had shrunk to some 5,000 miners working in around 20 collieries.^[15]

In ancient China, coal was used as fuel by the 4th century AD, but there was little extensive use until the 11th century.^[16]

[edit] Uses today

Coal rail cars

Coal fired power plants provide 49% of consumed electricity in the United States. This is the Castle Gate Plant near Helper, Utah.

[edit] Coal as fuel

Coal is primarily used as a solid fuel to produce electricity and heat through combustion. World coal consumption was about 6,743,786,000 short tons in 2006^[17] and is expected to increase 48% to 9.98 billion short tons by 2030.^[18] China produced 2.38 billion tons in 2006. India produced about 447.3 million tons in 2006. 68.7% of China's electricity comes from coal. The USA consumes about 14% of the world total, using 90% of it for generation of electricity.^[19]

When coal is used for electricity generation, it is usually pulverized and then combusted (burned) in a furnace with a boiler. The furnace heat converts boiler water to steam, which is then used to spin turbines which turn generators and create electricity. The thermodynamic efficiency of this process has been improved over time. Simple cycle steam turbines have topped out with some of the most advanced reaching about 35% thermodynamic efficiency for the entire process. Increasing the combustion temperature can boost this efficiency even further.^[20] Old coal power plants, especially "grandfathered" plants, are significantly less efficient and produce higher levels of waste heat. About 40% of the world's electricity comes from coal,^[21] and in 2008 approximately 49% of the United States electricity came from coal.^[22] The emergence of the supercritical turbine concept envisions running a boiler at extremely high temperatures and pressures with projected efficiencies of 46%, with further theorized increases in temperature and pressure perhaps resulting in even higher efficiencies.^[23]

Other efficient ways to use coal are combined heat and power cogeneration and an MHD topping cycle.

Approximately 40% of the world electricity production uses coal.^[24] The total known deposits recoverable by current technologies, including highly polluting, low energy content types of coal (i.e., lignite, bituminous), is sufficient for many years. However, consumption is increasing and maximal production could be reached within decades (see World Coal Reserves, below).

A more energy-efficient way of using coal for electricity production would be via solid-oxide fuel cells or molten-carbonate fuel cells (or any oxygen ion transport based fuel cells that do not discriminate between fuels, as long as they consume oxygen), which would be able to get 60%–85% combined efficiency (direct electricity + waste heat steam turbine).^{[citation needed]} Currently these fuel cell technologies can only process gaseous fuels, and they are also sensitive to sulfur poisoning, issues which would first have to be worked out before large-scale commercial success is possible with coal. As far as gaseous fuels go, one idea is pulverized coal in a gas carrier, such as nitrogen. Another option is coal gasification with water, which may lower fuel cell voltage by introducing oxygen to the fuel side of the electrolyte, but may also greatly simplify carbon sequestration. However, this technology has been criticised as being inefficient, slow, risky and costly, while doing nothing about total emissions from mining, processing and combustion.^[25] Another efficient and clean way of coal combustion in a form of coal-water slurry fuel (CWS) was well-developed in Russia (since the Soviet Union time). CWS significantly reduces emissions saving the heating value of coal.

[edit] Coking and use of coke

Coke oven at smokeless fuel plant, Wales

Coke is a solid carbonaceous residue derived from low-ash, low-sulfur bituminous coal from which the volatile constituents are driven off by baking in an oven without oxygen at temperatures as high as 1,000 °C (1,832 °F) so that the fixed carbon and residual ash are fused together. Metallurgical coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. The product is too rich in dissolved carbon, and must be treated further to make steel. The coke must be strong enough to resist the weight of overburden in the blast furnace, which is why coking coal is so important in making steel by the conventional route. However, the alternative route to is direct reduced iron, where any carbonaceous fuel can be used to make sponge or pelletised iron. Coke from coal is grey, hard, and porous and has a heating value of 24.8 million Btu/ton (29.6 MJ/kg). Some cokemaking processes produce valuable by-products that include coal tar, ammonia, light oils, and "coal gas".

Petroleum coke is the solid residue obtained in oil refining, which resembles coke but contains too many impurities to be useful in metallurgical applications.

[edit] Ethanol production

The reaction of coal and natural gas was used by a German manufacturer for Buna rubber: Chemische Werke Huls, at Marl, Germany, and AVCO Corp in the US. Consequently several references had described both Huls Arc Process and AVCO rotating arc reactor.^[26][27] Both reactors are of cylindrical shape and have a rotating electric arc. The cathode is at the cylinder axis, while the anode is on the circumference. As methane gas provided the highest yield, then it is forced with coal powder into a vortex passing through the electric arc for few milliseconds.

Huls Arc Process^[28] produced a mixture of acetylene and ethylene gases. The reaction conditions can be varied to determine the needed product. Increasing the Specific Energy Requirement (SER) favors acetylene production, and lower SER is for ethylene:

Enthalpy Change for Ethylene:^[29] = 127.34 kJ/mol, while for acetylene: = 301.4 kJ/mol. As a consequence, recent production processes are using conventional heating instead of electric arc.

Hydration of ethylene gas producing ethanol is the most important process for ethanol production. Vapor phase process is the preferred one^[30] in which ethylene and steam pass over a catalyst. One of the most accepted catalysts is diatomite impregnated with phosphoric acid.

[edit] Gasification

Coal gasification can be used to produce syngas, a mixture of carbon monoxide (CO) and hydrogen (H₂) gas. This syngas can then be converted into transportation fuels like gasoline and diesel through the Fischer-Tropsch process. This technology is currently used by the Sasol chemical company of South Africa to make gasoline from coal and natural gas. Alternatively, the hydrogen obtained from gasification can be used for various purposes such as powering a hydrogen economy, making ammonia, or upgrading fossil fuels.

During gasification, the coal is mixed with oxygen and steam (water vapor) while also being heated and pressurized. During the reaction, oxygen and water molecules oxidize the coal into carbon monoxide (CO) while also releasing hydrogen (H₂) gas. This process has been conducted in both underground coal mines and in coal refineries.

(Coal) + O₂ + H₂O → H₂ + CO

If the refiner wants to produce gasoline, the syngas is collected at this state and routed into a Fischer-Tropsch reaction. 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

High prices of oil and natural gas are leading to increased interest in "BTU Conversion" technologies such as gasification, methanation and liquefaction. The Synthetic Fuels Corporation was a U.S. government-funded corporation established in 1980 to create a market for alternatives to imported fossil fuels (such as coal gasification). The corporation was discontinued in 1985.

In the past, coal was converted to make coal gas, which was piped to customers to burn for illumination, heating, and cooking. At present, the safer natural gas is used instead.

[edit] Liquefaction

Coal can also be converted into liquid fuels such as gasoline or diesel by several different processes. In the direct liquefaction processes, the coal is either hydrogenated or carbonized. Hydrogenation processes are the Bergius process,^[31] the SRC-I and SRC-II (Solvent Refined Coal) processes and the NUS Corporation hydrogenation process.^[32][33] In the process of low-temperature carbonization, coal is coked at temperatures between 360 °C (680 °F) and 750 °C (1,380 °F). These temperatures optimize the production of coal tars richer in lighter hydrocarbons than normal coal tar. The coal tar is then further processed into fuels. Alternatively, coal can be converted into a gas first, and then into a liquid, by using the Fischer-Tropsch process. An overview of coal liquefaction and its future potential is available.^[34]

Coal liquefaction methods involve carbon dioxide (CO₂) emissions in the conversion process. If coal liquefaction is done without employing either carbon capture and storage technologies or biomass blending, the result is lifecycle greenhouse gas footprints that are generally greater than those released in the extraction and refinement of liquid fuel production from crude oil. If CCS technologies are employed, reductions of 5-12% can be achieved in CTL plants and up to a 75% reduction is achievable when co-gasifying coal with commercially demonstrated levels of biomass (30% biomass by weight) in CBTL plants.^[35] For most future synthetic fuel projects, Carbon dioxide sequestration is proposed to avoid releasing it into the atmosphere. Sequestration will, however, add to the cost of production. Currently all US and at least one Chinese synthetic fuel projects,^[36] include sequestration in their process designs.

[edit] Refined coal

Refined coal is the product of a coal-upgrading technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals. It is one form of several pre-combustion treatments and processes for coal that alter coal's characteristics before it is burned. The goals of pre-combustion coal technologies are to increase efficiency and reduce emissions when the coal is burned. Depending on the situation, pre-combustion technology can be used in place of or as a supplement to post-combustion technologies to control emissions from coal-fueled boilers.

[edit] Industrial processes

Finely ground bituminous coal, known in this application as sea coal, is a constituent of foundry sand. While the molten metal is in the mould the coal burns slowly, releasing 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.^[37] 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.^[38]

[edit] Cultural usage

Coal is the 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 uphold that children who misbehave will receive only a lump of coal from Santa Claus for Christmas in their stockings instead of presents.

It is also customary and lucky in Scotland to give coal as a gift on New Year's Day. It happens as part of First-Footing and represents warmth for the year to come.

[edit] Coal as a traded commodity

In North America, Central Appalachian coal futures contracts are currently traded on the New York Mercantile Exchange (trading symbol QL). The trading unit is 1,550 short tons (1,410 t) per contract, and is quoted in U.S. dollars and cents per ton. Since coal is the principal fuel for generating electricity in the United States, coal futures contracts provide coal producers and the electric power industry an important tool for hedging and risk management.^[39]

In addition to the NYMEX contract, the IntercontinentalExchange (ICE) has European (Rotterdam) and South African (Richards Bay) coal futures available for trading. The trading unit for these contracts is 5,000 tonnes (5,500 short tons), and are also quoted in U.S. dollars and cents per ton.^[40]

The price of coal increased from around $30.00 per short ton in 2000 to around $150.00 per short ton as of September 2008. As of October 2008, the price per short ton had declined to $111.50. Prices further declined to $71.25as of October 2010. ^[41]

[edit] Environmental effects

Aerial photograph of Kingston Fossil Plant coal fly ash slurry spill site taken the day after the event

There are a number of adverse environmental effects of coal mining and burning, specially in power stations including:

• Generation of hundreds of millions of tons of waste products, including fly ash, bottom ash, flue gas desulfurization sludge, that contain mercury, uranium, thorium, arsenic, and other heavy metals
• Acid rain from high sulfur coal
• Interference with groundwater and water table levels
• Contamination of land and waterways and destruction of homes from fly ash spills such as Kingston Fossil Plant coal fly ash slurry spill
• Impact of water use on flows of rivers and consequential impact on other land-uses
• Dust nuisance
• Subsidence above tunnels, sometimes damaging infrastructure
• Coal-fired power plants without effective fly ash capture are one of the largest sources of human-caused background radiation exposure
• Coal-fired power plants shorten nearly 24,000 lives a year in the United States, including 2,800 from lung cancer^[42]
• Coal-fired power plants emit mercury, selenium, and arsenic which are harmful to human health and the environment^[43]
• Release of carbon dioxide, a greenhouse gas, which causes climate change and global warming according to the IPCC and the EPA. Coal is the largest contributor to the human-made increase of CO₂ in the air^[44]

[edit] Economic aspects

Coal liquefaction is one of the backstop technologies that could potentially limit escalation of oil prices and mitigate the effects of transportation energy shortage that will occur under peak oil. This is contingent on liquefaction production capacity becoming large enough to satiate the very large and growing demand for petroleum. Estimates of the cost of producing liquid fuels from coal suggest that domestic U.S. production of fuel from coal becomes cost-competitive with oil priced at around $35 per barrel,^[45] (break-even cost). With oil prices as low as around $40 per barrel in the U.S. as of December 2008, liquid coal lost some of its economic allure in the U.S., but will probably be re-vitalized, similar to oil sand projects, with an oil price around $70 per barrel.

In China, due to an increasing need for liquid energy in the transportation sector, coal liquefaction projects were given high priority even during periods of oil prices below $40 per barrel.^[46] This is probably because China prefers not to be dependent on foreign oil, instead utilizing its enormous domestic coal reserves. As oil prices were increasing during the first half of 2009, the coal liquefaction projects in China were again boosted, and these projects are profitable with an oil barrel price of $40.^[47]

China is by far the largest producer of coal in the world.^[48] It has now become the world's largest energy consumer^[49] but relies on coal to supply about 70% of its energy needs.^[50] An estimated 5 million people work in China's coal-mining industry.^[51]

Among commercially mature technologies, advantages for indirect coal liquefaction over direct coal liquefaction are reported by Williams and Larson (2003).

[edit] Energy density

The energy density of coal, i.e. its heating value, is roughly 24 megajoules per kilogram.^[52]

The energy density of coal can also be expressed in kilowatt-hours, the units that electricity is most commonly sold in, per units of mass to estimate how much coal is required to power electrical appliances. One kilowatt-hour is 3.6 MJ, so the energy density of coal is 6.67 kW·h/kg. The typical thermodynamic efficiency of coal power plants is about 30%, so of the 6.67 kW·h of energy per kilogram of coal, 30% of that—2.0 kW·h/kg—can successfully be turned into electricity; the rest is waste heat. So coal power plants obtain approximately 2.0 kW·h per kilogram of burned coal.

As an example, running one 100-watt lightbulb for one year requires 876 kW·h (100 W × 24 h/day × 365 day/year = 876000 W·h = 876 kW·h). Converting this power usage into physical coal consumption:

It takes 438 kg (966 lb) of coal to power a 100 W lightbulb for one year.^[53] One should also take into account transmission and distribution losses caused by resistance and heating in the power lines, which is in the order of 5–10%, depending on distance from the power station and other factors.

[edit] Carbon intensity

Commercial coal has a carbon content of at least 70%. Coal with a heating value of 6.67 kWh per kilogram as quoted above has a carbon content of roughly 80%, which is

, where 1 mol equals to N_A (Avogadro Number) atoms.

Carbon combines with oxygen in the atmosphere during combustion, producing carbon dioxide, with an atomic weight of (12 + 16 × 2 = 44 kg/kmol). The CO₂ released to air for each kilogram of incinerated coal is therefore

.

This can be used to calculate an emission factor for CO₂ from the use of coal power. Since the useful energy output of coal is about 30% of the 6.67 kWh/kg(coal), the burning of 1 kg of coal produces about 2 kWh of electrical energy. Since 1 kg coal emits 2.93 kg CO₂, the direct CO₂ emissions from coal power are 1.47 kg/kWh, or about 0.407 kg/MJ.

The U.S. Energy Information Agency's 1999 report on CO₂ emissions for energy generation,^[54] quotes a lower emission factor of 0.963 kg CO₂/kWh for coal power. The same source gives a factor for oil power in the U.S. of 0.881 kg CO₂/kWh, while natural gas has 0.569 kg CO₂/kWh. Estimates for specific emission from nuclear power, hydro, and wind energy vary, but are about 100 times lower.

[edit] Underground fires

There are hundreds of coal fires burning around the world.^[55] 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 wildfires. Coal seams can be set on fire by spontaneous combustion or contact with a mine fire or surface fire. A grass fire in a coal area can set dozens of coal seams on fire.^[56][57] Coal fires in China burn 109 million tons of coal a year, emitting 360 million metric tons of CO₂. This contradicts the ratio of 1:1.83 given earlier, but it amounts to 2-3% of the annual worldwide production of CO₂ from fossil fuels, or as much as emitted from all of the cars and light trucks in the United States.^[58][59] In Centralia, Pennsylvania (a borough located in the Coal Region of the United States), an exposed vein of coal ignited in 1962 due to a trash fire in the borough landfill, located in an abandoned anthracite strip mine pit. Attempts to extinguish the fire were unsuccessful, and it continues to burn underground to this day. The Australian Burning Mountain was originally believed to be a volcano, but the smoke and ash comes from a coal fire which may have been burning for over 5,500 years.^[60]

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. Local people once used this method to mine ammoniac. This place has been well-known since the time of Herodotus, but European geographers misinterpreted the Ancient Greek descriptions as the evidence of active volcanism in Turkestan (up to the 19th century, when the Russian army invaded the area).

The reddish siltstone rock that caps many ridges and buttes in the Powder River Basin (Wyoming), and in western North Dakota is called porcelanite, which also may resemble the coal burning waste "clinker" or volcanic "scoria".^[61] 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.^[62] Wild coal fires in the area were reported by the Lewis and Clark Expedition as well as explorers and settlers in the area.^[63]

[edit] Production trends

Coal output in 2005

A coal mine in Wyoming, United States. The United States has the world's largest coal reserves.

In 2006, China was the top producer of coal with 38% share followed by the USA and India, according to the British Geological Survey.

[edit] World coal reserves

Coal reserves in BTUs as of 2009

At the end of 2006 the recoverable coal reserves amounted to around 800 or 900 gigatons. The United States Energy Information Administration gives world reserves as 930 billion short tons^[64] (equal to 843 gigatons) as of 2006. At the current extraction rate, this would last 132 years.^[65] However, the rate of coal consumption is annually increasing at 2-3% per year and, setting the growth rate to 2.5% yields an exponential depletion time of 56 years (in 2065).^[66] At the current global total energy consumption of 15.7 terawatts,^[67] there is enough coal to provide the entire planet with all of its energy for 37 years (assuming 0% growth in demand and ignoring transportation's need for liquid fuels).^{[original research?]}

The 930 billion short tons of recoverable coal reserves estimated by the Energy Information Administration are equal to about 4,116 BBOE (billion barrels of oil equivalent).^{[citation needed]} The amount of coal burned during 2007 was estimated at 7.075 billion short tons, or 133.179 quadrillion BTU's.^[68] This is an average of 18.8 million BTU per short ton. In terms of heat content, this is about 57,000,000 barrels (9,100,000 m³) of oil equivalent per day. By comparison in 2007, natural gas provided 51,000,000 barrels (8,100,000 m³) of oil equivalent per day, while oil provided 85.8 million barrels per day.

BP, in its 2007 report, estimated at 2006 end that there were 909,064 million tons of proven coal reserves worldwide, or 147 years reserves-to-production ratio. This figure only includes reserves classified as "proven"; exploration drilling programs by mining companies, particularly in under-explored areas, are continually providing new reserves. In many cases, companies are aware of coal deposits that have not been sufficiently drilled to qualify as "proven". However, some nations haven't updated their information and assume reserves remain at the same levels even with withdrawals. Collective projections generally predict that global peak coal production may occur sometime around 2025 at 30 percent above current production in the best case scenario, depending on future coal production rates.^[69]

Continental United States coal regions

Of the three fossil fuels, coal has the most widely distributed reserves; coal is mined in over 100 countries, and on all continents except Antarctica. The largest reserves are found in the USA, Russia, China, India and Australia. Pakistan also has newly discovered large reserves.^[70]

Note the table below.

Proved recoverable coal reserves at end-2006 (million tonnes (teragrams))^[71]

Country	Bituminous & anthracite	SubBituminous & lignite	TOTAL	Share
United States	111,338	135,305	246,643	27.1
Russia	49,088	107,922	157,010	17.3
China	62,200	52,300	114,500	12.6
India	90,085	2,360	92,445	10.2
Australia	38,600	39,900	78,500	8.6
South Africa	48,750	0	48,750	5.4
Ukraine	16,274	17,879	34,153	3.8
Kazakhstan	28,151	3,128	31,279	3.4
Poland	14,000	0	14,000	1.5
Brazil	0	10,113	10,113	1.1
Germany	183	6,556	6,739	0.7
Colombia	6,230	381	6,611	0.7
Canada	3,471	3,107	6,578	0.7
Czech Republic	2,094	3,458	5,552	0.6
Indonesia	740	4,228	4,968	0.5
Turkey	278	3,908	4,186	0.5
Greece	0	3,900	3,900	0.4
Hungary	198	3,159	3,357	0.4
Pakistan	0	3,050	3,050	0.3
Bulgaria	4	2,183	2,187	0.2
Serbia	200	1,800	2,000	0.18
Thailand	0	1,354	1,354	0.1
Mexico	860	351	1,211	0.1
North Korea	300	300	600	0.1
New Zealand	33	538	571	0.1
Spain	200	330	530	0.1
Zimbabwe	502	0	502	0.1
Romania	22	472	494	0.1
Venezuela	479	0	479	0.1
All others	4,691	24,111	28,802	3.1
TOTAL	478,771	430,293	909,064	100

[edit] Major coal producers

The reserve life is an estimate based only on current production levels and proved reserves level for the countries shown, and makes no assumptions of future production or even current production trends. For comparison, data for the European Union is also shown.

Production of Coal by Country and year (million tonnes)^[71][72]

Country	2003	2004	2005	2006	2007	2008	Share	Reserve Life (years)
China	1722.0	1992.3	2204.7	2380.0	2526.0	2782.0	42.5 %	41
USA	972.3	1008.9	1026.5	1053.6	1040.2	1062.8	18.0 %	224
EU	638.0	628.4	608.0	595.5	593.4	587.7	5.2 %	51
India	375.4	407.7	428.4	447.3	478.4	521.7	5.8 %	114
Australia	351.5	366.1	378.8	385.3	399.0	401.5	6.6 %	190
Russia	276.7	281.7	298.5	309.2	314.2	326.5	4.6 %	481
South Africa	237.9	243.4	244.4	244.8	247.7	250.4	4.2 %	121
Indonesia	114.3	132.4	146.9	195.0	217.4	229.5	4.2 %	19
Germany	204.9	207.8	202.8	197.2	201.9	192.4	3.2 %	35
Poland	163.8	162.4	159.5	156.1	145.9	143.9	1.8 %	52
Total World	5187.6	5585.3	5886.7	6195.1	6421.2	6781.2	100 %	142

If continuous growth in usage at the rate of the years 2003 to 2006 from the table above (6.0948% pa compound) is assumed, reserves would be exhausted in about 31 years (sum of geometric progression).^{[citation needed]}

[edit] Major coal exporters

Exports of Coal by Country and year (million short tons)^[73][74][75]

Country	2003	2004	2005	2006	2007	2008	Share
Australia	238.1	247.6	255.0	255.0	268.5	278.0	25.6%
Indonesia	107.8	131.4	142.0	192.2	221.9	228.2	21.0%
Russia	41.0	55.7	98.6	103.4	112.2	115.4	10.6%
USA	43.0	48.0	51.7	51.2	60.6	83.5	7.7%
Colombia	50.4	56.4	59.2	68.3	74.5	81.5	7.5%
China	103.4	95.5	93.1	85.6	75.4	68.8	6.3%
South Africa	78.7	74.9	78.8	75.8	72.6	68.2	6.3%
Canada	27.7	28.8	31.2	31.2	33.4	36.5	3.4%
Total	713.9	764.0	936.0	1,000.6	1,073.4	1,087.3	100%

[edit] Major coal importers

Imports of Coal by Country and year (million short tons)^[76]

Country	2006	2007	2008	Share
Japan	199.7	209.0	206.0	19.4%
South Korea	84.1	94.1	107.1	10.1%
India	52.7	29.6	70.9	6.7%
Taiwan	69.1	72.5	70.9	6.7%
Germany	50.6	56.2	55.7	5.2%
Total	991.8	1,056.5	1,063.2	100%

[edit] See also

Energy portal

[edit] References

[edit] Further reading

• Walter Licht, Thomas Dublin (2005). The Face of Decline: The Pennsylvania Anthracite Region in the Twentieth Century. Cornell University Press. ISBN 0-8014-8473-1. OCLC 60558740. 
• Long, Priscilla (1991). Where the Sun Never Shines: A History of America's Bloody Coal Industry. New York, NY: Paragon House. ISBN 1557784655. OCLC 25236866. 
• Rottenberg, Dan (2003). In the Kingdom of Coal; An American Family and the Rock That Changed the World. Routledge. ISBN 0-415-93522-9. OCLC 52348860. 
• Robert H. Williams and Eric D. Larson (December 2003). "A comparison of direct and indirect liquefaction technologies for making fluid fuels from coal" (PDF). Energy for Sustainable Development VII: 103–129. http://www.ieiglobal.org/ESDVol7No4/dclversussicl.pdf. 
• Outwater, Alice (1996). Water: A Natural History. New York, NY: Basic Books. ISBN 0-465-03780-1. OCLC 37785911. 
• Smith, Duane A. (May 1993). Mining America: The Industry and the Environment, 1800-1980. Lawrence, KS: University Press of Kansas. p. 210. ISBN 0870813064. 
• Freese, Barbara (2003). Coal: A Human History. Penguin Books. ISBN 0-7382-0400-5. OCLC 51449422. 

[edit] External links

Wikimedia Commons has media related to: Coal

Look up coal in Wiktionary, the free dictionary.

• Coal explained with coal terms for kids.
• Energy KIDS - Coal page from USA's Department of Energy.
• European Association for Coal and Lignite
• SourceWatch: Coal Issues portal
• International Energy Agency
• World Coal Institute
• World Coal-To-Liquids
• Advanced methods of using coal (Japanese Coal Energy Center)
• USDOE Hydrogen from Coal Research
• Coal Preparation
• Wyoming Coal from the University of Wyoming
• Coal - origin, purification and consumption
• Energy Options: Coal, Nightly Business Report