Related Terms

• Activated carbon, activated charcoal, anthracite, batu bara (Indonesian), bituminous coal, black lung, carbon fiber, coal deposits, coal energy, coalification, coke, combustible, contour mining, drilling, electricity, extraction, fossil fuel, hydrocarbon, lignite, longwall mining, miners, mountaintop refining removal mining, nonrenewable, open-cast mining, open-cut mining, open-pit mining, organic rock, overburden, pneumoconiosis, pollution, room and pillar mining, Sago mine, sedimentary rock, strip mining, sub-bituminous coal, subsistence, surface mining, thermal coal, underground mining.

Background

• Coal mining is the extraction of coal from deposits found either near the surface of the earth or underground. Coal is a fossil fuel, a nonrenewable (available in limited quantities) fuel source. Coal consists of hydrogen, oxygen, carbon, sulfur, and other trace elements.

• A coal reserve is a deposit of coal that can be mined. Once a coal reserve is discovered, usually by a commercially owned mining corporation, a survey is made, and the area is explored by drilling holes into the coal deposit and analyzing the recovered coal for carbon and moisture content. Mining operations are expensive, and a coal mine is started if there are sufficient quantities of coal to warrant the expense.

• The formation of coal is called coalification. About 360-290 million years ago (during the carboniferous period), the remains of plants existed in peat bogs and swamps on the earth's surface. Over time, these bogs and swamps were buried under sediment by the movement of the earth's crust and exposed to extreme heat and pressure. These conditions caused the vegetation to fossilize and form solid, sedimentary rock (a type of rock formed by the combining of minerals and organic materials) known as coal.

• Coal is combustible, which means it can be ignited. The combustibility of different types of coal varies depending on the conditions that created them. For instance, brown coal is softer, and it contains more moisture and less carbon for use as an energy source. Hard coal is harder, shiny, and black. It contains less moisture and more carbon, making it a more efficient source of energy.

• Coal is found all over the world. Proved coal reserves are the quantities of coal that can be removed from deposits of coal using existing methods according to geological data. The largest concentrations of coal, at 238,308 million metric tons, are located in the United States, according to the energy company BP. This represents 28.9% of the world's coal reserves. Russia, China, and India also contain large reserves at 19%, 13.9%, and 7.1%, respectively.

• According to the Energy Information Administration (EIA), about 44% of coal produced in the United Stated is sub-bituminous and mined in Wyoming. Sub-bituminous coal is a relatively soft coal that contains about 35-45% carbon. Its heat value ranges from about 8,000 to 13,000 British thermal units (BTUs). Bituminous coal, which has a higher heat value and contains more carbon than sub-bituminous coal, accounts for about half of coal production in the United States and is mined mostly in Kentucky, West Virginia, and Pennsylvania. Lignite coal is produced by about 20 mines located mostly in Texas and North Dakota and accounts for seven percent of total coal production in the United States. Anthracite coal is found only in Pennsylvania and accounts for less than one percent of U.S. production.

• China is the largest coal producer at 1,414.5 million metric tons oil equivalent (Mtoe) in 2008, an increase of 10% from the previous year, according to BP. (Million metric tons oil equivalent (Mtoe) is a measurement of the amount of released energy when a million metric tons of crude oil is burned.) The United States was the second largest producer at 596.9Mtoe, and Australia was the third with 219.9Mtoe. Over the last 25 years, hard coal production has increased 97% globally, according to the World Coal Institute. Coal production increased 1.3% in the United States from 2007 to 2008. Production is growing fastest in Asia. Total world production increased 5.3% from 2007 to 2008.

• Coal mining produces coal that is used primarily as fuel to generate electricity. The burning of coal produces heat that turns water into steam. The steam is used to rotate turbines that are responsible for generating electricity. Electricity production accounts for 92% of coal usage in the United States, according to the EIA. According to the World Coal Institute, as an energy source, coal generates 41% of electricity globally. Other uses of coal heat include manufacturing cement and paper. Some of the compounds that can be separated from coal, such as methanol and ethylene, are used to fabricate plastics, tar, and other materials. At high temperatures, coal is changed into a solid carbon material called coke, which reaches extremely high temperatures and is used to smelt iron into steel.

• Most coal is consumed by the country that produces it. The largest consumer of coal was China, with 1,406.3Mtoe of coal consumed in 2008, according to BP. The United States was the second largest consumer in 2008 at 564Mtoe, and India the third largest at 231.4Mtoe. Fifteen percent of hard coal produced is sold globally or exported, according to the World Coal Institute. Total world consumption increased 3.1% from 2007 to 2008.

• There is some evidence that coal energy may have been used as early as 4,000 B.C. in Wales. Coal was used as a source of energy in China around 1,000 B.C. and was used throughout China by the 14th Century. The Romans used coal in Britain in A. D. 400. Coal was mined by the Hopi Indians in the 12th Century. In the late 13th Century, coal mining began in northern England. Most early coal mining is believed to have been surface mining, with miners chiseling coal from deposits close to the surface of the earth. The Industrial Era (late 18th to early 19th Centuries) spurred widespread coal prospecting (discovery) and mining throughout Europe. The first European underground mines were makeshift and dangerous, with frequent roof collapses and flooding from underground water sources.

• Modern mining techniques began in the late 1800s, with the development of machinery to cut, dig, and haul coal deposits, thus requiring less human intervention. As power sources for this equipment became more efficient, so did mining operations. In the 1940s, continuous miners, or single pieces of equipment that could perform many mining tasks such as chiseling away rock and removing debris, were developed. The continued mechanization of mining has reduced the need for human labor.

• At the current rate of extraction of coal from deposits, the World Coal Institute estimates that the world's coal reserves may be depleted in 130 years. Strategies that involve using alternative fuel sources such as wind, water, and solar power may slow the depletion of fossil fuels. Developing new fuel sources such as fuels that are made from organic materials (biofuels) would also slow depletion.

• Coal mining has made a significant impact on the American economy and energy production, but it has also had major effects on the environment. Accessing underground coal sources releases methane, a greenhouse gas with 20 times the potency of carbon dioxide. Coal mining is responsible for 90% of methane emissions in the United States. Since global environmental commissions such as the U.S. Environmental Protection Agency (EPA) have identified greenhouse gasses as environmental hazards, measures have been taken to reduce methane emissions from coal mines. In 1994, the EPA launched the Coalbed Methane Outreach Program (CMOP) in an effort to reduce greenhouse gas emissions, expand profitable recovery of coal mine methane, and promote the use of clean energy sources, such as nuclear or hydroelectric power.

• The process of coal mining requires the use of highly acidic liquids to handle, wash, and eliminate the coal that is collected. Runoff from coal mines contains high concentrations of highly acidic substances that often come in contact with local bodies of water. Additionally, the runoff is evaporated and reintroduced to Earth's surface as acid rain. Acid rain has had a substantial effect on plant and animal life in exposed ecosystems, and it has caused the deterioration of large portions of the United States' infrastructure. The EPA has also taken measures to reduce the pollution of waters and acid rain by implementing the Clean Air Act (amendments) in 1990. This act allowed the EPA to fine companies for violating air pollution limits.

Technique

• General: Coal that has been subjected to higher pressures and temperatures for longer periods is harder and contains less moisture and more carbon. The heat content of coal is inversely proportional to its moisture content. When coal is purified or cleaned, which removes impurities and moisture, its heat content and market value (price on the open market) may increase. Coal is categorized in the United States based on the amount of heat or carbon it contains.

• Types of coal: The carbon content in different types of coal runs along a continuum. Coal is placed in different categories depending on the percentage of carbon it contains. From lowest to highest carbon or heat content, coal is rated as lignite, sub-bituminous, bituminous, and anthracite. Brown, soft, or low-rank coal with more moisture and lower carbon content, is categorized as lignite and sub-bituminous coal. Bituminous and anthracite coal are categorized as hard coal, which has higher carbon content and less moisture. Lignite, sub-bituminous, and bituminous coal is used primarily to generate electricity. Harder coal, typically anthracite, is used for industrial processes. In 2007, the coal consumed in the United States produced about 20 million Btu (British thermal unit, a measure of heat content) per short ton (equal to 2,000 pounds), according to the U.S. Energy Information Administration (EIA).

• Coal prospecting: Coal prospecting involves the discovery and analysis of coal deposits in a given area. Mapping is an important tool for collecting data on the types of rocks, geological formations, and human populations in the area. The volume and type of coal located in a deposit and at what depth is determined by drilling into the deposit and removing coal samples for chemical and physical analysis.

• Types of coal mining: Coal mining is the extraction of coal from deposits. There are several methods for coal extraction that generally fall into two categories: surface (open-cast/open-cut) and underground (deep) mining. The mining method used depends, for example, on where the coal is located, what type of coal it is, and how much coal the deposit contains. In a deposit that extends from the surface to deep underground, it may first be surface mined, and then underground mines are established. The most common form of mining globally is underground or deep mining. Sixty percent of the coal produced globally is mined underground. Most coal (about 60% according to EIA) in the United States, though, is mined on the surface. Anthracite mines are usually located underground, whereas lignite mines are usually found at the surface.

• Surface mining: Surface mining is the mining of coal deposits that are found near the surface of the Earth. It is also called open-cast or open-cut mining. Surface mining usually extracts 90% or more of coal in a deposit, according to the World Coal Institute. The first step in surface mining is the removal of vegetation to expose the rock and soil covering the coal deposit, which is also called overburden. Then, explosives or large pieces of equipment are used to expose the coal and penetrate the overburden. These blast holes can range from 25 to 100 centimeters. This overburden is then removed and transferred. The exposed coal is drilled, mined, and usually processed on-site.

• Processing coal removes any impurities, such as dirt or sulfur, which decrease the value and energy efficiency of the coal. The coal is then transported. After an area is mined, the overburden is returned to the mining pit along with topsoil to replant the land, which may then be used for agriculture or recreation.

• Strip mining: Strip mining, also called contour or area mining, is a type of surface mining wherein the overburden is removed from the coal deposit in roughly rectangular strips that vary in size depending on the size of the mining operation. The overburden is either placed in an area that has already been mined or transported to another, unmined area. Strips are usually dug in sequence, adjacent, and parallel to one another. On flat terrain, this type of mining is usually called area mining. On hilly terrain, contour mining removes overburden horizontally along the hillside. Some overburden is placed in front of the strips to create a bench or wall around or in front of the strip so as to prevent debris from falling down the hill.

• Open-pit mining is a type of strip mining used when harder rock or more overburden is present. In open-pit mining, drilling and blasting removes the overburden, which initially may be transported off-site until several mining pits have been excavated at the mine site. Contour strip mining varies slightly. Auger mining is another type of strip mining wherein holes are drilled into the coal deposit as much as 100 meters deep.

• Mountaintop removal mining: Mountaintop removal mining is a type of surface mining used when coal deposits are located within a mountain or range of mountains. The forests and vegetation covering the deposit are removed and then the overburden is blasted or cut away, often removing the top or side of a mountain. It is then transported to a nearby valley or stream and deposited for storage.

• Draglines: Draglines are a type of equipment used during surface mining to remove overburden from an exposed coal deposit. Draglines use a bucket, in some cases as large as a two-car garage, to scoop up and remove rock and soil from a strip. The largest draglines are over 2,000 metric tons, may carry nearly 17 million pounds of material, and reach depths of 64 meters. Draglines represent only one piece of equipment typically used in surface mining. Trucks, bulldozers, excavators, and loaders are also frequently used in surface mining and may carry as much as 250 tons of materials. Although draglines are capable of removing several tons of material at once unlike smaller pieces of equipment, older models may be prone to breakdowns and are difficult to operate.

• Underground mining: Underground mining operations can be found at depths of 1,000 feet below the earth's surface. Early underground mining was often makeshift and dangerous. Shafts were dug deep into the ground. Horses or windmills were used to lift buckets of coal out of the mine. Water often seeped into mine, and so drainage tunnels were dug horizontally from the main well or buckets of water were lifted to the top. The steam engine improved both drainage and coal recovering by speeding up the removal process. Currently, there are two major types of underground coal mining operations: room and pillar mining and longwall mining.

• Room and pillar mining: Room and pillar mining uses the existing coal deposit to create structures to support mining operations. Pillars of coal are left intact to provide support and integrity for the roofs of holes or rooms that are created within the coal deposit. At depths greater than 400 meters, greater pressure on the mine ceiling requires larger pillars, which may decrease the amount of coal recovered from the mine. Either separate machines and crews of miners can perform the tasks of drilling, blasting, and removing coal, or it may be done by one machine. The pillars may be left intact or broken down and the coal they contain recovered. The extraction of pillars is a delicate process. Removing a pillar places added stress on other pillars, which can collapse. Room and pillar mining is the most basic and one of the oldest forms of underground mining.

• Longwall mining: Longwall mining extracts sections of overburden from an area, which may be an area as large as 300 meters by 3,000 meters. Coal is removed in slices from the face or section of the coal deposit that is being mined. Each slice may be as large as 1.2 meters. A longwall mining system consists of a large piece of equipment that spans the coal face. It holds up the roof of the face while cutting, drilling, blasting, and removing coal. When the system completes mining in the area, the roof may be allowed to fall. The mined area may also be filled with materials to maintain ceiling stability. Backfilling, as it is called, fills the mined area with sand or coal processing waste. The mining system then moves on to the next face. Longwall mining can recover more coal than other types of mining (as much as 75%), although the costs for equipment and its installation may exceed room and pillar mining. Longwall mining also produces a large quantity of dust and methane, and proper ventilation is required, according to the EIA. Shortwall mining is similar to longwall mining except the cleared area is usually no more than 100 meters wide.

• Additional equipment: Underground mining requires extensive additional equipment and operations to provide support and safety. Lighting, drainage, ventilation, communication, and other operations are important components of underground mining. Portals, or small areas located throughout the underground mine, may house these operations. Facilities on the surface also provide wash areas, offices, coal processing plants, warehouses, and parking lots. Large haulage systems carry coal out of a working mine to a processing plant. Ventilation is particularly important, as underground oxygen levels are insufficient, and dangerous gases can accumulate during mining. Ventilation removes these gases and pumps in oxygen.

Theory/Evidence

• Coal deposits: Coal is found all over the world. Unlike oil and natural gas reserves, most coal is found in the United States and Russia, not the Middle East. The United States has the largest concentration of coal deposits, with coal mined in 27 states. The most coal is mined in Wyoming, West Virginia, Kentucky, Pennsylvania, and Texas, in that order, according to the U.S. Energy Information Administration (EIA). Most coal deposits are found in three areas of the United States: the Appalachian, Interior, and Western Coal Regions.

• Appalachian Coal Region: The Appalachian Coal Region includes the states of Kentucky, Virginia, West Virginia, and Tennessee. West Virginia produces more coal than any other state in this region. This region accounts for more than one-third of U.S. coal production and is characterized by smaller surface mining operations and large underground mines. From 2006 to 2007, coal production in this region decreased by about three percent, according to EIA.

• Interior Coal Region: The Interior Coal Region includes the states of Illinois, Indiana, and Texas. Texas is the highest coal-producing state in this region. Texas produces one-third of the coal for the Interior Coal Region, although production dropped slightly (by about three percent) for the entire region from 2006 to 2007. Mining operations in this area are run by large or medium-sized corporations. The region is characterized by medium-sized surface mines (produces between about 30,000 and 50,000 short tons). The coal is mostly mid- and high-sulfur bituminous.

• Western Coal Region: The Western Coal Region includes the states of Nebraska, North Dakota, Montana, Colorado, and Utah. This region accounts for more than half of U.S. coal production. Some of the largest mining operations in the world are found in this region, which is characterized by large surface mines. Mining in this region increased slightly from 2006 to 2007. Wyoming is the highest coal-producing state in the region, accounting for 73% of coal produced by the region. Wyoming's coal production is expected to continue to increase, due to the low sulfur content of its coal, which is attractive to power plants seeking to decrease their sulfur emissions. This is in spite of the fact that the coal produced by Wyoming has a lower heat content and may cost more to transport.

• Coal mining: Surface mining accounts for two-thirds of the coal mining in the United States, because it is less expensive than underground mining, and many coal deposits in the United States are found less than 200 feet beneath the surface, according to the EIA. Surface mining may be a relatively efficient process, extracting 90% or more of coal, according to the World Coal Institute. Since 1978, advances in mining technology and operations have increased efficiency such that one miner produces three times more coal per hour, according to the EIA.

• Good mining practices: Guidelines for improving miners' health and safety and reducing mining operations' impact on the environment have been developed by the International Council on Mining and Metals (ICMM), the United Nations Conference of Trade and Development (UNCTAD), the United Nations Environment Programme (UNEP), and the UK Department for International Development (DFID) in a joint effort known as Good Practice. Occupational safety is ensured with comprehensive emergency response plans, employee training, and communication. Working and traveling areas are well lit and ventilated. Hazardous areas are clearly marked, and workers are provided with personal protective equipment (PPE). The health of employees is checked regularly.

• Coal miners: Historically, coal mining operations were carried out by coal miners. Miners extracted coal both on the surface and underground with rudimentary tools, such as shovels, hammers, and chisels. The development of continuous miners and other pieces of equipment increased the need for a smaller, more skilled labor force. Some mining positions may require a vocational degree. According to the U.S. Bureau of Labor Statistics, job opportunities are available for coal miners, though employment is expected to decline in the future. From 1985 to 2000, the number of employed coal miners decreased by 55%, according to the Sierra Club. In 2006, the number of employed coal miners was 79,000, and their hourly earnings in 2006 averaged $22.08.

• Safety: Following the death of 362 miners in a mining accident in 1907 in West Virginia, the U.S. Congress created the Bureau of Mines to improve mine safety. In 1968, an explosion at a mine in Farmington, West Virginia, killed 78 miners, prompting the passage of the Federal Coal Mine Health and Safety Acts of 1969 and 1977. These acts expanded the federal government's control over mine operations and strengthened enforcement. Although technological, occupational, and legislative improvements have made coal mining a safer profession, miners may still suffer many ailments as a result of their work. Toxic fumes, dust, fires, mine collapses, oxygen deprivation, thermal stress (extreme hot or cold temperatures), and other workplace hazards have contributed to the increased risk of injury and death at coal mines. According to the U.S. Mine Safety and Health Administration (MSHA), the injury rate (number of injuries per 200,000 miners) decreased from 6.03 (2002) to 3.8 (2008), although fatalities have remained about the same. Citations and orders issued by MSHA to mine operators were at an all-time high in 2008 at 107,441.

• Sago mine explosion: Underground coal mining is particularly dangerous. A mine collapse or explosion may cause severe injury and death. As recently as 2006, an explosion at the Sago mine in West Virginia killed 12 miners and injured one. According to the MSHA, the Sago mine's injury rate in 2005 was significantly above the national average. MSHA took 2,008 enforcement actions against the mine operator in 2005, many of which involved severe negligence. Specific areas of the mine were shut down 18 times during 2005 due to violations of health and safety regulations. The MSHA concluded that lightning caused an explosion at an abandoned part of the mine. The explosion broke seals that protected working areas of the mine and a fire spread. The United Mine Workers of America (UMWA) reached a different conclusion, which was that the explosion was caused by friction of the roof supports. These structures ignited the methane gas-filled atmosphere.

• MINER Act of 2006: Following three serious accidents at coal mines in 2006, the U.S. Congress passed the MINER Act of 2006. The MINER Act focuses on preventing accidents and injuries at coal mines, improving escape for trapped miners, and improving rescue and response to mine accidents. Additional funding was also provided for technological improvements in communication, oxygen supply, and miner tracking

• Coal recovery: Many factors affect the amount of coal recovered during mining operations. Typically, more coal is recovered during surface mining than underground mining. Recovery from underground mines can be less than 40%, according to the EIA. Some coal is not mined to create support structures for mining operations. Also, certain underground conditions may affect mining operations. The rock may contain faults or folds that make it difficult to recover the coal within these geological features.

• Coal use: Coal energy powers many industries, but most coal is used to generate electricity. According to the EIA, 92% of U.S. coal use is for electricity generation. Half of the electricity generated in the United States is fueled by coal. Almost all the coal used to generate electricity in the United States is mined in the United States. According to the EIA, ten 100-watt light bulbs are powered for one hour by one pound of coal. Texas was the largest coal consumer in 2007. There were 617 coal-fired power plants in the United States in 2007. Coal energy and coal by-products are also used in industry to produce plastics, fertilizer, steel, concrete, and paper.

• Coal waste: Coal mining produces several types of waste that contribute to water, air, and land pollution. Coal dust, disposed overburden, water waste, methane gas, subsistence (sinking soil), and acidified water are all forms of coal waste.

• Solid waste: Rock, soil, and vegetation, called overburden, are removed from areas during mining. The resulting waste may be deposited in streams, valleys, or nearby pits. Underground mining may cause instability and sinking of the surface soil, which is called subsistence. Coal dust is particulates of minerals, metals, and other materials that are released during mining operations and may reduce air quality.

• Water waste: When rainwater or water used for coal extracting or processing mixes with minerals and heavy metals exposed during mining, it becomes acidic. This acidic solution may seep into the ground or contaminate water, affecting water quality and the surrounding ecosystem. Abandoned underground mines may become filled with pools of acidic water.

• Gaseous waste: Large amounts of methane gas are released from rocks during the mining of coal deposits, particularly those located underground. Methane is a greenhouse gas 20 times more potent than carbon dioxide, according to the Sierra Club.

• Coal exports: Only 4% of coal produced in the United States is sold on the international market. More than half of this is used by the steel industry. Most coal exports are used by Canada, Brazil, the Netherlands, and Italy. In the past, coal has not been transported large distances because coal is bulky, very heavy, and can be found in mines around the world. U.S. coal exports have decreased over the last 10 years. Australia is the largest coal exporter, exporting 244Mt (megatonnes, equaling 1 gigagram), according to the World Coal Institute.

• Coal imports: U.S. coal imports are growing. Most of these imports are used by electric power facilities located on the coastlines of the United States. Many states bordering the Atlantic Ocean and the Gulf of Mexico import coal by sea because it is less expensive than transporting it by railroad or other methods of transportation from coal mines in other parts of the United States. Coal is imported from Colombia, Venezuela, and Indonesia. Colombia accounts for 74% of U.S. coal imports, according to the EIA. Although many countries mine coal, they may still import certain types of coal that have fewer impurities or higher heat content.

Health Impact/Safety

• General: The extraction and processing of coal from surface and underground deposits produces waste products that may contribute to air, water, and land pollution. Coal mining also poses many potential occupational hazards.

• The U.S. Department of Labor's Mine Safety and Health Administration (MSHA) enforces the Federal Mine Safety and Health Act to ensure the safety of miners. According to the National Mining Association, injuries related to coal mining dropped by two-thirds from 1990 to 2006.

• Occupational hazards:

• General: Coal mining operations may expose miners to many hazards, and it is considered one of the most dangerous jobs. Between January and June 9, 2009, seven fatalities were reported at coal mines in the United States, according to the MSHA. Between 1996 and June 2009, 438 fatalities occurred at coal mining operations in the United States. The most fatalities occurred in West Virginia (130) and the second most in Kentucky (117). The total number of fatalities that occurred at coal mines in the United States between 1900 and 2008 was 104,656. Some studies show that larger coal mines and mines wherein workers perform less diverse tasks are safer.

• Hazardous substances and explosives: Miners may use or be exposed to toxic or explosive materials or fumes during the extraction of coal. Diesel fumes from mining equipment are a potential carcinogen (cancer-causing agent) and may cause asthma, headaches, nausea, and irritation of the eyes and nose. Underground miners are exposed to 100 times more concentrated diesel fumes than what is typical for the average person. Electrical accidents may cause electrical shock, trauma, auditory damage, cuts, abrasions, and burns. The fourth leading cause of mining deaths (coal and other types of mining) is electrical accident. Blasting and other explosions may cause trauma, dismemberment, poisoning from toxic fumes, burns, and death. Loud noises, particularly in underground mines, may damage auditory cells and cause hearing loss. Noise may prevent miners from hearing alarms or other emergency signals. Fire is also a potential hazard due to the presence of methane gas, which is combustible. Inadequate lighting may cause injury or fatality.

• Dust: Coal dust is an invisible dust that, when inhaled, may lead to serious or even fatal respiratory disease. Coal workers' pneumoconiosis (CWP), also called black lung disease, is a respiratory disease caused by inhaling significant quantities of coal dust that damages the lung tissue. The U.S. Centers for Disease Control and Prevention (CDC) found that one out of 13 coal miners who worked in mining for 25 years or more suffered from black lung disease. Symptoms of black lung include shortness of breath, coughing, and scarring of lung tissue. The severity of black lung depends on the amount of exposure. Black lung claims about 1,000 lives per year, according to a 2006 congressional report, and 16,000 workers were completely disabled by black lung in 2002. Some miners may develop symptoms after less than 10 years of work experience. Studies suggest that CWP may lead to progressive massive fibrosis, a serious respiratory disorder that causes lesions in the lungs. If mining dust contains high concentrations of silica, miners may develop silicosis, another type of pneumoconiosis that progresses more rapidly. Some studies show that some coal miners also suffer from emphysema, another respiratory disorder.

• Physical hazards: Falling from great heights, slipping, injury from the use of dangerous equipment, and ground or ceiling instability causing collapse and burial are potential physical hazards faced by miners. During mining operations, miners may be exposed to harsh weather conditions or high or low temperatures that may be detrimental to health. Everyday practices in mining may contribute to musculoskeletal disorders, such as low back pain and disorders, osteoarthritis, knee pain, and spinal disk degeneration. Some studies show that miners are more affected by these disorders than those in other jobs. Low-back problems cause more lost work time in the coal industry than any other injury.

• Environmental hazards:

• General: Coal mining poses many threats to the environment, including air, water, land, and noise pollution.

• Methane and carbon dioxide gas: Coal mining releases methane gas into the atmosphere. This phenomenon is called coalbed mine methane (CMM). According to the U.S. Environmental Protection Agency (EPA), CMM contributes to climate change, as it is a powerful greenhouse gas. Methane may be directly released into the atmosphere at surface mining operations. CMM is pumped out of underground mines after it is diluted with air through ventilation systems. Ventilation air methane (VAM) and accounts for half or more of CMM emissions in the United States and globally. CMM may also leak out of abandoned mines through cracks or open pipes. Piles of coal may also emit CMM. According to the EPA, 400 abandoned mines emit CMM. China contributed the most CMM emissions globally in 2000 (40%), while the U.S. contributed 14% of CMM emissions. Coal mining operations also produced 53.8TgCO2 equivalents (equivalent emissions of carbon dioxide) in 2003, which was down from 81.9TgCO2 equivalents in 1990.

• Dust: Coal dust may pose a similar threat to the surrounding human and animal populations as it does for coal miners. Coal dust is invisible and may contain minerals, metals, and other materials that may cause respiratory ailments.

• Acid mines: According to the EPA, abandoned mine lands (AMLs) may be detrimental to the environment and human health. When abandoned mines fill with water, the water may become acidified, or have a lower pH. This acidic water may drain into streams or other bodies of water, compromising quality. This is referred to as acid mine drainage (AMD). Acidic water dissolves metals such as mercury and copper. These metals may then leach into water supplies. Changes in pH and the presence of metals may cause dramatic changes in the surrounding ecosystem, including damaging soil, plant, and animal life. This can also impair drinking water quality and negatively affect human health. According to the Sierra Club, 3,000 miles of streams in Pennsylvania have been polluted by AMD.

• Coal water waste: Water is used during coal extraction and processing to prevent dust accumulation. This water waste may contain sediment, minerals, or metals that may contaminate ground or surface water supplies.

• Overburden: Rock, soil, and vegetation removed prior to coal extraction (called overburden) may be dumped in streams or in other areas, disrupting local ecosystems. Nearly 1,200 streams in the United States have been contaminated by overburden from mountaintop removal mining (a type of surface mining) operations, according to the Sierra Club.

• Land clearing: Vegetation and topsoil are often removed in surface and underground mining. This practice may disrupt ecosystems and promote soil erosion and flooding. The extent of damage depends on the operation. Mountaintop removal mining, which removes a large portion of forest for coal extraction, may damage 1.4 million acres of land in the Appalachian region of the United States by 2020.

• Subsistence: Underground mining creates holes underground that if not properly filled can create unstable areas. This land may sink, damaging property, ecosystems, or agriculture.

Future Research or Applications

• Coalreserves: More coal deposits exist in the United States than other fossil fuel reserves, such as oil and natural gas. The U.S. demonstrated reserve base (DRB), which is the amount of coal that has been surveyed and is potentially mineable, was 489 billion short tons (one short ton equals 2,000 pounds) in 2007. The U.S. Department of Energy (DOE) continues to improve the tracking of U.S. coal reserves, working with data collected by the U.S. Geological Survey, and it strives to create a more accurate depiction of potential coal reserves. At the current rate of extraction of coal from deposits, the world's coal reserves will be depleted in 132 years, according to the U.S. Energy Information Administration (EIA).

• Access to reserves: EIA estimates that only 50% of the U.S. coal DRB may be potentially mined. Restricted access to coal reserves may be due to environmental regulations, land use issues, and property rights. The amount of coal that potentially may be recovered in the United States is estimated at 263 billion short tons. Existing coal mines have reserves totaling approximately 18.6 billion short tons.

• Future coal production: The world's demand for energy will increase 60% by 2030, according to the International Energy Agency (IEA). Developing countries will account for two-thirds of the demand and half of the total energy consumption. Coal is found throughout the world and is inexpensive to mine compared to other fuel sources. Coal is also considered a more secure fuel source, as its price is not as volatile as other fossil fuels, according to the World Energy Council. Some agencies such as the World Coal Institute advocate the continuation of mining operations to encourage access to coal energy, particularly for developing countries

• Coal mining technology: Advances in technology can greatly improve the health and safety of coal miners, particularly those working underground. A self contained self-rescuer (SCSR) is a breathing apparatus worn by miners, so that in an event of an emergency or when breathing conditions are poor, the miners may be provided several hours of respiratory support. SCSRs usually provide oxygen and filter out smoke or toxic gases. Depending on the activity level of the miner when it is used, an SCSR may provide respiratory support for more or less than an hour. Most national and international agencies strongly suggest or require that miners wear SCSRs while working.

• Coal mine methane: Coal mine methane (CMM) is the methane gas released during coal mining operations, and it is also a greenhouse gas. CMM emissions are projected to grow by 20% between 2000 and 2020, according to the World Energy Council. Some mining operations (in China, Ukraine, and Poland, for example) recover CMM and use it as an energy source, either for heat or power production. As of 2005, CMM projects generated 300MWe (megawatts of electrical output) of power at active and abandoned mining sites globally. Expanding CMM projects may, according to the World Energy Council, reduce greenhouse gas emissions and power requirements at mining operations. This may help countries reach the goals set by the Kyoto Protocol, an international agreement signed by many countries to reduce greenhouse gas emissions, including methane gas.

• Coal and sulfur: To reduce the amount of sulfur released into the atmosphere when coal is burned to generate electricity or for other purposes, coal mining operations have developed technologies to remove most of the sulfur from coal when it is mined or to only mine coal that contains low-levels of sulfur. Wyoming's coal production is expected to continue to increase, due to the low sulfur content of its coal.

• Mine safety: The United Mine Workers of America (UMWA) has made several recommendations to improve the safety and occupational health of mine workers. These recommendations include following the regulations originally outlined in the Federal Coal Mine Health and Safety Acts of 1969 and 1977. These acts established guidelines for the type and strength of seals that contain explosions and toxic fumes, for mine rescue teams that are readily available in the event of an emergency, for the installation of shelters to protect trapped miners until they are rescued, and for more advanced methods of communication. The UMWA also recommends technological improvements including more advanced SCSRs and tracking devices. More hazardous practices such as second mining (mining below an area that has already been mined, creating very high, potentially unstable ceilings) should not be approved by mine operators or state and federal agencies, UMWA says.

• Future of coal mining: In the past decade, international collaborations and global summits have identified major offenders to the environment. Restrictions have been made to greenhouse gas emissions, which has limited the amount of coal mining in many nations. However, coal is still the largest source of energy in most countries, and many of these countries are reluctant to change their means of energy production. Environmental protection agencies have urged the development and advancement of clean energy production, such as hydrogen energy. Hydrogen energy systems, though in the initial stages of development, are a promising means of yielding amounts of energy large enough to fuel automobiles and boats. Hydrogen energy involves the release of energy from hydrogen atoms when it is combined with oxygen. By combining free hydrogen (produced from the electrolysis of water by non-carbon-containing sources) with oxygen, carbon dioxide emissions can be avoided.

Author Information

• This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

1. Centers for Disease Control and Prevention (CDC). Underground coal mining disasters and fatalities--United States, 1900-2006. MMWR Morb Mortal Wkly Rep. 2009 Jan 2;57(51):1379-83. View Abstract

2. Cohen RA, Patel A, Green FH. Lung disease caused by exposure to coal mine and silica dust. Semin Respir Crit Care Med. 2008 Dec;29(6):651-61. View Abstract

3. Good Practice: Sustainable Development in the Mining and Metals Sector. www.goodpracticemining.org

4. International Energy Agency (IEA). www.iea.org

5. Kuempel ED, Wheeler MW, Smith RJ, et al. Contributions of dust exposure and cigarette smoking to emphysema severity in coal miners in the United States. Am J Respir Crit Care Med. 2009 Aug 1;180(3):257-64. View Abstract

6. Natural Standard: The Authority on Integrative Medicine. www.naturalstandard.com

7. Page K. Blood on the coal: the effect of organizational size and differentiation on coal mine accidents. J Safety Res. 2009;40(2):85-95. View Abstract

8. Sierra Club. www.sierraclub.org

9. United Mine Workers of America (UMWA). www.umwa.org

10. U.S. Department of Labor Mine Safety and Health Administration (MSHA). www.msha.gov

11. U.S. Energy Information Administration (EIA). www.eia.doe.gov

12. U.S. Environmental Protection Agency (EPA). www.epa.gov

13. World Coal Institute. www.worldcoal.org

14. World Energy Council. www.worldenergy.org