Coal

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Posted by motoman 03/24/2009 @ 13:13

Tags : coal, energy, sciences

News headlines
Suit claims Ala. coal firm funded Colombian terror - The Associated Press
(AP) — Relatives of dozens of slain Colombians sued an Alabama-based coal company in federal court Thursday, accusing it of making millions of dollars in payments to a paramilitary group that sowed terror in the South American country....
Coal explosion at Weston plant injures 1 - Chicago Tribune
A coal explosion at the Weston Power Plant in Rothschild left one person injured. Wisconsin Public Service Corp. said one of three coal mills in Unit 2 of the plant exploded after becoming overpressurized. The cause is under investigation....
DEP halts new coal slurry injections - Forbes
By TIM HUBER , 05.28.09, 09:03 PM EDT Coal slurry will not be allowed to be injected at new underground sites in West Virginia after the state's Department of Environmental Protection issued a moratorium on the practice Wednesday....
Nations Gamble on Carbon Capture - Reuters
By John Gartner - Matter Network Around the world governments are betting billions of dollars on research to develop technology to capture carbon emitted from coal plants. It's probably even money right now whether carbon capture becomes the next thin...
Activists target mountaintop removal coal mining - Free Speech Radio News
The campaign against Massey Energy's mountaintop removal coal mining operations is picking up steam this summer. Last week, some 150 people took part in an action camp – 17 were arrested in civil disobedience actions protesting the controversial...
Excelsior Energy plan for Iron Range coal plant denied - Duluth News Tribune
The Minnesota Public Utilities Commission dealt a blow Thursday to Excelsior Energy's plans to build a gasified coal plant on the Iron Range. Commissioners unanimously rejected Excelsior's petition to reconsider a proposed power purchase agreement with...
Feds scrutinize PRB coal merger - The Casper Star Tribune
By DUSTIN BLEIZEFFER The US Federal Trade Commission has made a "second request" regarding Arch Coal Inc.'s proposed purchase of Rio Tinto Energy America's Jacobs Ranch coal mine in Wyoming's Powder River Basin. The action essentially gives the FTC...
Swine Flu Vaccine Possible by October - Washington Post
Associated Press Colombians Sue Coal Company Over Deaths: Relatives of dozens of slain Colombians sued an Alabama-based coal company in federal court Thursday, accusing it of making millions of dollars in payments to a paramilitary group that sowed...
Steel Authority Profit Falls on Prices, Coal Costs - Bloomberg
By Debarati Roy and Pratik Parija May 28 (Bloomberg) -- Steel Authority of India Ltd., the nation's second-biggest steelmaker, reported a drop in profit for the second straight quarter as metal prices fell and coal costs remained at a record....
Teck Resources in Talks to Sell Coking Coal Assets to Pay Debt - Bloomberg
By Bloomberg News May 27 (Bloomberg) -- Teck Resources Ltd., Canada's biggest base-metals company, is in talks to sell coking-coal assets to Chinese companies to help reduce debt. “We are going through a process” of talks with Chinese companies,...

Coal

Anthracite coal

Coal is a readily combustible black or brownish-black sedimentary rock. 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 along with variable quantities of other elements, chiefly sulfur, hydrogen, oxygen and nitrogen.

Coal was formed from plant remains that were protected by water and mud against oxidization and biodegradation, thus trapping atmospheric carbon in the ground. Over time, the chemical and physical properties of the remains 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 source 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. Coal is extracted from the ground by mining, either underground or in open pits.

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 a large amount of hydrogen. It consists primarily of "exinite" macerals, now termed "liptinite".

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. The earliest recognized use is from the Shenyang area 4000 BC where Neolithic inhabitants had begun carving ornaments from black lignite, but it was not until the Han Dynasty (206 BC–220 AD) that coal was also used for fuel. 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.

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. 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.

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.

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.

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.

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.

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 on a large technical scale in Germany between 1934 and 1945 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 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.

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.

Coal is the official state mineral of Kentucky and the official state rock of Utah. Both U.S. states have an 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.

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

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 back at around USD 40 per barrel as of December 15, 2008, liquid coal has once again lost much of its economic allure.

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

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).

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/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.

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.

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), the burning of 1 kg of coal produces about 2 kW·h/kg(coal) of electrical energy. Since 1 kg coal roughly translates as 1.83 kg of CO2, then 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.

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 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". 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.

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

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.

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.

The reserve life is an estimate based only on current production levels for the countries shown, and makes no assumptions of future production or even current production trends.

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Clean coal technology

Clean coal technology is an umbrella term used to describe technologies being developed that aim to reduce the environmental impact of coal energy generation. These include chemically washing minerals and impurities from the coal, gasification (see also IGCC), treating the flue gases with steam to remove sulfur dioxide, carbon capture and storage technologies to capture the carbon dioxide from the flue gas and dewatering lower rank coals (brown coals) to improve the calorific quality, and thus the efficiency of the conversion into electricity.

Clean coal technology usually addresses atmospheric problems resulting from burning coal. Historically, the primary focus was on sulfur dioxide and particulates, due to the fact that it is the most important gas which leads to acid rain. More recent focus has been on carbon dioxide (due to its impact on global warming) as well as other pollutants. Concerns exist regarding the economic viability of these technologies and the timeframe of delivery, potentially high hidden economic costs in terms of social and environmental damage, and the costs and viability of disposing of removed carbon and other toxic matter.

Coal, which is primarily used for the generation of electricity, is the second largest domestic contributor to carbon dioxide emissions in the USA. The public has become more concerned about global warming which has led to new legislation. The coal industry has responded by running advertising touting clean coal in an effort to counter negative perceptions, as well as by putting more than $50 billion towards the development and deployment of clean coal technologies, including carbon capture and storage. The expenditure has been unsuccessful to date in that there is not a single commercial scale coal fired power station in the US that captures and stores more than token amounts of CO2.

In the early 20th century, prior to World War II, "clean coal" (also called "smokeless coal") referred to anthracite and high-grade bituminous coal, used for cooking and home heating.

According to the United Nations Intergovernmental Panel on Climate Change, the burning of coal, a fossil fuel, is blamed for climate change and global warming. (See the UN IPCC Fourth Assessment Report). As 25.5% of the world's electrical generation in 2004 was from coal-fired generation (see World energy resources and consumption), reaching the carbon dioxide reduction targets of the Kyoto Protocol will require modifications to how coal is utilized.

The latest in clean coal technologies, carbon capture and sequestration, is a means to capture carbon dioxide emissions from coal-fired plants and permanently bury them underground. Currently, there are more than 80 carbon capture and sequestration projects underway in the United States. Sequestration technology has yet to be tested on a large scale and may not be safe or successful. Sequestered CO2 may eventually "leak" up through the ground, may lead to unexpected geological instability or may cause contamination of aquifers used for drinking water supplies. There are also concerns that plans to pump some of the sequestered CO2 into certain oil and gas reserves, to help make the fuels easier to pump out of the ground, will lead to increased concentrations of CO2 in potential fuel supplies. This would have to be removed or released during the refining process.

Supporters of clean coal use the Great Plains Synfuels plant to support the technical feasibility of carbon dioxide sequestration. Carbon dioxide from the coal gasification is shipped to Canada where it is injected into the ground to aid in oil recovery. Supporters acknowledge that economics can be problematic for carbon sequestration.

The byproducts of coal combustion are considerably hazardous to the environment if not properly contained. This is clean coal's largest challenge, both from the practical and public relations perspectives.

While it is possible to remove most of the sulfur dioxide (SO2), nitrogen oxides (NOx) and particulate (PM) emissions from the coal-burning process, carbon dioxide (CO2) emissions and radionuclides will be more difficult to address. Technologies exist to capture and store CO2, but they have not yet been utilized on a large-scale commercial basis due to the high economic costs.

Coal-fired power plants are the largest aggregate source of mercury: 50 tons per year come from coal power plants out of 150 tons emitted nationally in the USA and 5000 tons globally. In the USA, neither the combustion products of oil, nor their associated solid or liquid waste streams, are considered to be major contributors to mercury pollution.

Coal burning industries have previously succeeded in significantly reducing pollutants. Current coal fired electric generating plants emit 70% fewer regulated emissions (total mass per energy produced) than in 1970. This factoid includes values for NOx, SOx, volatile organic compounds, particulate matter, and carbon monoxide emissions only. SOx formed the greatest proportion of these emissions in 1970, where significant gains had been made in order to combat acid rain.

Coal burning power plants produce large amounts of solid and liquid waste products, mostly in the form of fly-ash and bottom ash. These waste products are stored in landfills and large ponds. Increasing emission controls at the plants results in increased waste products. It is estimated that coal burning power plants produce over 100 million tons of waste per year and that well over 2 billion tons of waste is stored at plants in the USA. While the hazard content of ash by percentage is very low, the concentration of millions of tons at plant sites creates the danger of significant pollution in the event of containment failures. A small fraction of coal ash is beneficially used in the manufacture of concrete and other construction materials. The use of ash in construction materials sequesters the hazardous ingredients and prevents their release in quantities large enough to be hazardous. Unfortunately the economics of beneficial use are such that some subsidy would be required from the power plant for widespread use. As it stands now, most electric utilities prefer to store the ash rather than subsidize beneficial use and in most cases charge for sale of the ash. As a result of these policies, most power plant waste continues to be stored in ponds and landfills.

The Cost of CCS section of the Carbon capture and storage article details the lifetime costs for natural gas, pulverized coal, and Integrated Gasification Combined Cycle (IGCC) with and without carbon capture. Carbon capture and sequestration is one of the newest technologies to fall under the 'clean coal' umbrella.

A 2003 study conducted by the International Energy Agency (IEA) on greenhouse gases, found that the cost of building a Shell-designed IGCC that doesn't capture carbon could cost $1,371 per kW and a comparable system that captures carbon could cost $1,860 per kW." These costs can be contrasted with other types of plants in economics of new plants. In September 2008, the Government Accountability Office (GAO) released a report recommending that the government lead the way in addressing any issues surrounding the large-scale development of carbon capture and sequestration, saying that the high cost of carbon capture technologies, especially those used to retrofit existing plants, is a key barrier to the commercial deployment of carbon capture. A demonstration plant based on chilled ammonia and storage is planned to be launched in 2009 in West Virginia. If the technology is successful on a 20MW equivalent plant at Mountaineer, there are plans to extend the technology to 450-MW coal-fired units at in Oologah, Oklahoma.

FutureGen was a US government project announced by President George W. Bush in 2003 to build a near zero-emissions coal-fueled power plant to produce hydrogen and electricity while using carbon capture and storage.

FutureGen was a public-private partnership to build the world's first near zero-emissions coal-fueled power plant. The 275-megawatt plant was intended to prove the feasibility of producing electricity and hydrogen from coal while capturing and permanently storing carbon dioxide underground. FutureGen was to be designed, developed and operated by the FutureGen Industrial Alliance, a non-profit consortium of coal mining and electric utility companies formed to partner with the DOE on the FutureGen project. The project was still in the development stage when its funding was canceled in January 2008. The decision of the location of the host site, subject to DOE’s completing NEPA environmental reviews, was announced by the Alliance in December 2007 after a two-year bidding and review process. Construction was scheduled to begin in 2009, with full-scale plant operations to begin in 2012.

During the 2008 U.S. Presidential campaign, candidates John McCain and Barack Obama expressed interest in the development of clean coal technologies as part of an overall comprehensive energy plan. President Obama called for five first-of-their-kind clean coal plants in the U.S. Government groups have also advocated for the development and deployment of advanced clean coal technologies, including the U.S. Chamber of Commerce, which recommended that the president, within the first 100 days, establish a fund managed by fossil-fuel utilities for the research and development of carbon capture and storage at private, academic and government sites. The recommendation also calls on Congress to "commit to doubling research and development funding over five years for renewable energy technologies, as well as clean coal energy." In September 2008, the Government Accountability Office released a report recommending government leadership to advance the progress of carbon capture and storage technology, noting that the cost of implementing the technologies were an impediment to their commercial-scale usage.

The US Department of Energy is working with private industry in developing clean coal technologies. One of the clean coal technologies being developed is carbon sequestration, capturing carbon dioxide and eliminating or slowing its release back into the atmosphere. Another technology under development is Integrated Gasification Combined Cycle or IGCC. The development of clean coal also creates the possibility of international business for the United States and other world markets.

In Australia, clean coal is often referred to by Prime Minister Kevin Rudd as a possible way to reduce greenhouse gas emissions. The previous Prime Minister John Howard has stated that nuclear power is a better alternative, as clean coal technology may not prove to be economically favorable.

Prominent environmentalists, including Dan Becker, director of the Sierra Club's Global Warming and Energy Program, believe that the term clean coal is misleading: "There is no such thing as 'clean coal' and there never will be. It's an oxymoron" and an industry's hype, there's no such thing as clean coal. The Sierra Club's Coal Campaign has launched a site refuting the clean coal statements and advertising of the coal industry.

Complaints focus on the environmental impacts of coal extraction, high costs to sequester carbon, and uncertainty of how to manage end result pollutants and radionuclides.

Critics of the planned power plants assert that there is no such thing as clean coal and that the plant will still release large amounts of pollutants compared to renewable energy sources such as wind power and solar power. However, there is yet to be a commercial scale wind or solar project capable of replacing baseload fuels like coal.

The 2007 Australian of the Year, paleontologist and influential environmental activist Tim Flannery made the assertion that the concept of clean coal might not be viable for all geographical locations.

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Coal power in the United States

Electricity production from coal power by year in the USA from 1995 to 2006.

Coal power accounts for about half of the electricity production in the United States. Utilities buy more than 90 percent of the coal mined in the United States .

In 2006, there were 1493 coal-powered units at the electrical utilities across the US, with the total nominal capacity of 335.8 GW (compared to 1024 units at nominal 278 GW in 2000). The actual average generated power from coal in 2006 was 227.1 GW (1.991 trillion kilowatt-hours per year), the highest in the world and still slightly ahead of China (1.95 trillion kilowatt-hours per year) at that time. Back in 2000, the US average production of electricity from coal was 224.3 GW (1.966 trillion kilowatt-hours per year). In 2006, the U.S. consumed 1,026,636,000 short tons (931,349,000 metric tons) or 92.3% of coal for electricity generation.

Average share of electricity generated from coal in the US has dropped slightly, from 52.8% in 1997 to 49.0% in 2006. However, due to growth of the total demand for electricity, the net production of coal-generated electricity increased over the same period from 1.845 to 1.991 trillion kilowatt-hours per year in absolute terms.

The coal plants are mostly base-load plants and account for about 32% of the peak electricity production in the summer, when the electricity demand is the highest and the auxiliary (mostly non-coal) plants are added to the grid.

The average share of electricity generated from coal power was projected to increase again with a coal plant building boom. As of 2007, 154 new coal-fired plants are on the drawing board in 42 states. The Energy Department forecasted that coal's share will rise to 57 percent by 2030, fueled in part by rising natural gas prices, but in 2008 it has said that the conversion from coal to biomass power is a growing trend in the United States .

Byproducts of coal plants have been linked to acid rain.

While these 86 plants have a capacity of 107.1 GW, or 9.9% of total U.S. electric capacity, they emitted 5,389,592 tons of SO2 in 2006 – which represents 28.6% of U.S. SO2 emissions from all sources.

Emissions from electricity generation account for the largest share of U.S. greenhouse gases, 38.9% of U.S. production of carbon dioxide in 2006 (with transportation emissions close behind, at 31%). Although coal power only accounted for 49% of the U.S. electricity production in 2006, it was responsible for 83% of CO2 emissions caused by electricity generation that year, or 1,970 Tg of CO2 emissions. Further 130 Tg of CO2 were released by other industrial coal-burning applications.

U.S. coal-fired electricity-generating power plants owned by utilities emitted an estimated 48 tons of mercury in 1999, the largest source of man-made mercury pollution in the U.S. In 1995-96, this accounted for 32.6% of all mercury emitted into the air by human activity in the U.S. In addition, 13.1% was emitted by coal-fired industrial and mixed-use commercial boilers, and 0.3% by coal-fired residential boilers, bringing the total U.S. mercury pollution due to coal combustion to 46% of the U.S. man-made mercury sources. In contrast, China's coal-fired power plants emitted an estimated 200 ± 90 tons of mercury in 1999, which was about 38% of Chinese human-generated mercury emissions (45% being emitted from non-ferrous metals smelting).

In 2007 an advertising campaign was launched to improve public opinion on coal power titled America's Power. This was done by Americans for Balanced Energy Choices, a pro-coal organization started in 2000.

In the face of increasing electricity demand through the 2000s, the US has seen a "Growing Trend Against Coal-Fired Power Plants". In 2006 through 2007 there was first a bullish market attitude towards coal with the expectation of a new wave of plants, but political barriers and pollution concerns escalated potentially, which is likely to damage plans for new generation and put pressure on older plants. In 2007, 59 proposed coal plants were cancelled, abandoned, or placed on hold by sponsors as a result of financing obstacles, regulatory decisions, judicial rulings, and new global warming legislation.

The Stop Coal campaign has called for a moratorium on the construction of any new coal plants and for the phase out of all existing plants, citing concern for global warming. Others have called for a carbon tax and a requirement of carbon sequestration for all coal power plants.

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Source : Wikipedia