Coal

Coal

Example chemical structure of coal

Coal is a fossil fuel formed in ecosystems where plant remains were preserved by water and mud from oxidization and biodegradation, thus sequestering atmospheric carbon. Coal is a readily combustible black or brownish-black rock. It is a sedimentary rock, but the harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. It is composed primarily of carbon and hydrogen along with small quantities of other elements, notably sulfur. Coal is extracted from the ground by coal mining, either underground mining or open pit mining (surface mining).

Coal is the largest source of fuel for the generation of electricity world-wide, as well as the largest world-wide source of carbon dioxide emissions. Carbon dioxide is a greenhouse gas and these emissions contribute to climate change and global warming. In terms of carbon dioxide emissions, coal is slightly ahead of petroleum and about double that of natural gas.

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Early use

Further information: History of coal mining

China was the only ancient civilisation that posessed abundant coal resources. The earliest recognized use is from the Shenyang area 4000 BCE where Neolithic inhabitants had begun carving ornaments from black lignite. During the Han Dynasty coal was also used for fuel.

Outcrop coal was used in Britain during the Bronze Age (2000-3000 years BC), where it has been detected as forming part of the composition of funeral pyres. 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". 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. 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. Evidence of coal's use for iron-working in the city during the Roman period has been found.

There is no evidence that the product was of great importance in Britain before the High Middle Ages, after about AD 1000. Mineral coal came to be referred to as "seacoal," probably because it came to many places in eastern England, including London, by sea. This is accepted as the more likely explanation for the name than that it was found on beaches, having fallen from the exposed coal seams above or washed out of underwater coal seam outcrops. 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. 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. 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.

Uses today

File:DSCN4524 ashtabulacoalcars e2.jpg

Coal rail cars in Ashtabula, Ohio.

Coal as fuel

Further information: Clean coal technology, Coal electricity, and Global warming

Coal is primarily used as a solid fuel to produce electricity and heat through combustion. World coal consumption is about 6.2 billion tons annually. China produced 2.38 billion tons in 2006 and India produced about 447.3 million tons in 2006. 68.7% of China's electricity comes from coal. The USA consumes about 1.053 billion tons of coal each year, using 90% of it for generation of electricity. The world in total produced 6.19 billion tons of coal in 2006.

When coal is used for electricity generation, it is usually pulverized and then 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. "Standard" steam turbines have topped out with some of the most advanced reaching about 35% thermodynamic efficiency for the entire process, which means 65% of the coal energy is waste heat released into the surrounding environment. 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 , and approximately 49% of the United States electricity comes from coal..

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.

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

Approximately 40% of the world electricity production uses coal. The total known deposits recoverable by current technologies, including highly polluting, low energy content types of coal (i.e., lignite, bituminous), might be sufficient for 300 years' use at current consumption levels, although 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). 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.

Coking and use of coke

Main article: Coke (fuel)

Coke burning

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. Metallurgic coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. 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.

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. Currently, this technology is being 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.

Liquefaction - Coal-To-Liquids (CTL)

Coals can also be converted into liquid fuels like gasoline or diesel by several different processes. In the direct liquefaction processes, the coal is either hydrogenated or carbonized. Alternatively, coal can be converted into a gas first, and then into a liquid, by using the Fischer-Tropsch process.

In the Bergius process , coal is liquefied by mixing it with hydrogen gas and heating the system (hydrogenation). This process was used by Germany during World War I and World War II and has been explored by SASOL in South Africa. Several other direct liquefaction processes have been developed, among these being the SRC-I and SRC-II (Solvent Refined Coal) processes developed by Gulf Oil and implemented as pilot plants in the United States in the 1960s and 1970s.. The NUS Corporation developed another hydrogenation process which was patented by Wilburn C. Schroeder in 1976. The process involved dried, pulverized coal mixed with roughly 1wt% molybdenum catalysts. Hydrogenation occurred by use of high temperature and pressure synthesis gas produced in a separate gasifier. The process ultimately yielded a synthetic crude product, Naphtha, a limited amount of C₃/C₄ gas, light-medium weight liquids (C₅-C₁₀) suitable for use as fuels, small amounts of NH₃ and significant amounts of CO₂.

The process of low temperature carbonization (LTC) can also convert coal into a liquid fuel. Coal is coked at temperatures between 450 and 700°C compared to 800 to 1000°C for metallurgical coke. 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. The Karrick process was developed by Lewis C. Karrick, an oil shale technologist at the U.S. Bureau of Mines in the 1920s.

In the Fischer-Tropsch process, an indirect route, coal is first gasified to make syngas (a balanced purified mixture of CO and H₂ gas). Next, Fischer-Tropsch catalysts are used to convert the syngas into light hydrocarbons (like ethane) which are further processed into gasoline and diesel. This method was used by Nazi Germany for many years and is currently being used by Sasol in South Africa. In addition to creating gasoline, syngas can also be converted into methanol, which can be used as a fuel, or into a fuel additive.

All of these liquid fuel production methods release carbon dioxide (CO₂) in the conversion process, far more than is released in the extraction and refinement of liquid fuel production from petroleum. If these methods were adopted to replace declining petroleum supplies, carbon dioxide emissions would be greatly increased on a global scale. For future liquefaction projects, Carbon dioxide sequestration is proposed to avoid releasing it into the atmosphere, though no pilot projects have confirmed the feasibility of this approach on a wide scale. As CO₂ is one of the process streams, sequestration is easier than from flue gases produced in combustion of coal with air, where CO₂ is diluted by nitrogen and other gases. Sequestration will, however, add to the cost.

The reaction of coal and water using high temperature heat from a nuclear reactor offers promise of liquid transport fuels that could prove carbon-neutral compared to petroleum use. The development of a reliable nuclear reactor that could provide 900 to 1000 deg C process heat, such as the pebble bed reactor, would be necessary.

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.[1] It is one form of several pre-combustion treaments 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.

Full Article Refined coal

Coal as a traded commodity

The price of coal has gone up from around $30 per short ton in 2000 to around $150.00 per short ton as of September 26th, 2008. As of October 31, 2008, the price per short ton has declined to $111.50.

In North America, a Central Appalachian coal futures contract is currently traded on the New York Mercantile Exchange (trading symbol QL). The trading unit is 1,550 short tons 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, the futures contract provides coal producers and the electric power industry an important tool for hedging and risk management.

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 metric tons, and are also quoted in U.S. dollars and cents per ton.

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.

Environmental effects

Main article: Environmental effects of coal

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

These effects include:

• release of carbon dioxide and methane, both of which are greenhouse gases, which are causing climate change and global warming according to the IPCC. Coal is the largest contributor to the human-made increase of CO2 in the air.
• generation of hundred 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
• interference with groundwater and water table levels
• impact of water use on flows of rivers and consequential impact on other land-uses
• dust nuisance
• subsidence above tunnels, sometimes damaging infrastructure
• rendering land unfit for other uses
• 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, including 2,800 from lung cancer.
• coal-fired power plant releases emissions including mercury, selenium, and arsenic which are harmful to human health and the environment.

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 some authors have suggested could 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 USD per barrel, (break-even cost). With oil prices climbing up to as high as 145 USD per barrel (posted on July 11, 2008), coal has become a viable financial alternative to oil for the time being, although current production is small.

Among commercially mature technologies, advantage for indirect coal liquefaction over direct coal liquefaction are reported by Williams and Larson (2003). Estimates are reported for sites in China where break-even cost for coal liquefaction may be in the range between 25 to 35 USD/barrel of oil.Template:Fact date=October 2007'

Intensive research and project developments have been implemented from 2001. The World CTL Award is granted to personalities having brought eminent contribution to the understanding and development of Coal liquefaction. The 2009 presentation ceremony will take place in Washington DC (USA) at the World CTL 2009 Conference (25-27 March, 2009).

Energy density

Main article: Energy value of coal

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

The energy density of coal can also be expressed in kilowatt-hours for some unit of mass, the units that electricity is most commonly sold in, 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—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 computer for one year requires 876 kW·h (100 W × 24 h/day × 365 {days in a year} = 876000 W·h = 876 kW·h). Converting this power usage into physical coal consumption:

${\frac {876\ \mathrm {kW\cdot h} }{2.0\ \mathrm {kW} \cdot \mathrm {h/kg} }}=438\ \mathrm {kg\ of\ coal} =966\ \mathrm {pounds\ of\ coal}$

It takes 438 kg (966 lb) of coal to power a computer for one full year. 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.

Relative carbon cost

Because coal is at least 50% carbon (by mass), then 1 kg of coal contains at least 0.5 kg of carbon, which is

${\frac {0.5\ \mathrm {kg} }{\mathrm {12} \cdot \mathrm {kg/kmol} }}={\frac {1}{24}}\ \mathrm {kmol}$ where 1 mol is equal to N_A (Avogadro Number) particles.

This combines with oxygen in the atmosphere during combustion, producing carbon dioxide, with an atomic weight of (12 + 16 × 2 = mass(CO₂) = 44 kg/kmol), so 1⁄24 kmol of CO₂ is produced from the 1⁄24 kmol present in every kilogram of coal, which once trapped in CO₂ weighs approximately

${\frac {1}{24}}\ \mathrm {kmol} \cdot {\frac {44\ \mathrm {kg} }{\mathrm {kmol} }}={\frac {11}{6}}\ \mathrm {kg} \approx 1.83\ \mathrm {kg}$.

This can be used to put a carbon-cost of energy on the use of coal power. Since the useful energy output of coal is about 30% of the 6.67 kW·h/kg(coal), we can say about 2 kW·h/kg(coal) of energy is produced. Since 1 kg coal roughly translates as 1.83 kg of CO₂, we can say that using electricity from coal produces CO₂ at a rate of about 0.915 kg/(kW·h), or about 0.254 kg/MJ.

This estimate compares favourably with the U.S. Energy Information Agency's 1999 report on CO₂ emissions for energy generation, which quotes a specific emission rate of 950 g CO₂/(kW·h). By comparison, generation from oil in the U.S. was 890 g CO₂/(kW·h), while natural gas was 600 g CO₂/(kW·h). Estimates for specific emission from nuclear power, hydro, and wind energy vary, but are about 100 times lower. See environmental effects of nuclear power for estimates.

Underground fires

There are hundreds of coal fires 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 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. 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. 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.

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 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". 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.

Production trends

File:2005coal.PNG

Coal output in 2005

A coal mine in Jharkhand, India. India has about 10% of world's coal reserves.

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

World coal reserves

At the end of 2006 the recoverable coal reserves amounted around 800 or 900 gigatons. The United States Energy Information Administration gives world reserves as 998 billion short tons (equal to 905 gigatons), approximately half of it being hard coal. At the current production rate, this would last 164 years. At the current global total energy consumption of 15 terawatt, there is enough coal to provide the entire planet with all of its energy for 57 years.

The 998 billion tons of recoverable coal reserves estimated by the Energy Information Administration are equal to about 4,417 BBOE (billion barrels of oil equivalent). The amount of coal burned during 2001 was calculated as 2.337 GTOE (gigatonnes of oil equivalent), which is about 46 million barrels of oil equivalent per day. Were consumption to continue at that rate those reserves would last about 263 years. As a comparison, natural gas provided 51 million barrels (oil equivalent), and oil 76 million barrels, per day during 2001.

British Petroleum, in its annual report 2007, estimated at 2006 end, 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.

US 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, Australia, China, India and South Africa.

Note the table below.

Proved recoverable coal reserves at end-2006 (million tonnes (teragrams))

Country	Bituminous & anthracite	SubBituminous & lignite	TOTAL	Share
USA	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
Thailand	0	1,354	1,354	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
TOTAL	478,771	430,293	909,064	100.0

• Recent discoveries in the Thar region of Pakistan have given rise to a discovery of nearly 185 billion tonnes. [2]

Major coal producers

Production of Coal by Country and year (million tonnes)

Country	2003	2004	2005	2006	Share
China	1722.0	1992.3	2204.7	2380.0	.384
USA	972.3	1008.9	1026.5	1053.6	.170
India	375.4	407.7	428.4	447.3	.072
Australia	351.5	366.1	378.8	373.8	.060
Russia	276.7	281.7	298.5	309.2	.050
South Africa	237.9	243.4	244.4	256.9	.041
Germany	204.9	207.8	202.8	197.2	.032
Indonesia	114.3	132.4	146.9	195.0	.031
Poland	163.8	162.4	159.5	156.1
Total World	5187.6	5585.3	5886.7	6195.1	1

See also: List of countries by coal production

Major coal exporters

Exports of Coal by Country and year (million short tonnes)

Country	2003	2004	2005	Share
Australia	238.1	247.6	257.6	.320
Indonesia	107.8	131.4	147.6	.134
China	103.4	95.5	79.0	.098
South Africa	78.7	74.9	77.5	.096
South America	57.8	65.9	68.8	.086
Russia	41.0	55.7	62.3	.077
USA	43.0	48.0	49.9	.062
Canada	27.7	28.8	31.0	.039
Poland	16.4	16.3	16.4	.020
Vietnam	N/A	10.3	14.1	.018
Total	713.9	764.0	804.2	1

See also

• Abiogenic petroleum origin
• Asphaltene
• Australian Coal Alliance
• Biochar
• Carbochemistry
• Carbon sequestration
• Charcoal
• Clean coal
• Coal assay
• Coal dust
• Coal in China
• Coal Measure (stratigraphic unit)
• Coal Mine Safety and Health Act of 1969 (in the US)
• Coal mining
• Coal phase out
• Coal-tar
• Energy value of coal
• Fluidized bed combustion
• Gasification
• History of coal mining
• Major coal producing regions
• Mountaintop removal mining
• Underground Coal Gasification
• World Coal Institute

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 (2003). "A comparison of direct and indirect liquefaction technologies for making fluid fuels from coal" (PDF). Energy for Sustainable Development. VII: 103–129. {{cite journal}}: Unknown parameter |month= ignored (help)
• Outwater, Alice (1996). Water: A Natural History. New York, NY: Basic Books. ISBN 0-465-03780-1. OCLC 37785911.
• Smith, Duane A. (1993). Mining America: The Industry and the Environment, 1800-1980. Lawrence, KS: University Press of Kansas. p. 210. ISBN 0870813064. {{cite book}}: Unknown parameter |month= ignored (help)
• Freese, Barbara (2003). Coal: A Human History. Penguin Books. ISBN 0-7382-0400-5. OCLC 51449422.

External links

• European Association for Coal and Lignite
• SourceWatch: Coal Issues portal
• International Energy Agency
• World Coal Institute
• Clean coal technologies
• 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
• World Coal-To-Liquids 2008 Conference 3 & 4 April 2008 - Paris