Environmental effects of coal
There are a number of adverse environmental effects of coal mining and burning.
These effects include:
* release of
carbon dioxideand methane, both of which are greenhouse gases causing climate changeand global warmingaccording to the IPCC. Coal is the largest contributor to the human-made increase of CO2 in the atmosphere. [http://www.columbia.edu/~jeh1/2007/IowaCoal_20071105.pdf]
* waste products including
uranium, thorium, and other radioactive and heavy metal contaminants
acid mine drainage(AMD)
* interference with
groundwaterand water tablelevels
* 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 the other uses.
Coal miningcauses a number of harmful effects. When coal surfaces are exposed, pyrite(iron sulfide), also known as "fool's gold", comes in contact with water and air and forms sulfuric acid. As water drains from the mine, the acid moves into the waterways, and as long as rain falls on the mine tailingsthe sulfuric acid production continues, whether the mine is still operating or not. This process is known as acid rock drainage (ARD) or acid mine drainage(AMD). If the coal is strip mined, the entire exposed seam leaches sulfuric acid, leaving the subsoil infertile on the surface and begins to pollute streams by acidifying and killing fish, plants, and aquatic animals who are sensitive to drastic pHshifts.
Coal mining produces
methane, a potent greenhouse gas. Methane is the naturally occurring product of the decay of organic matter as coal deposits are formed with increasing depths of burial, rising temperatures, and rising pressures over geological time. A portion of the methane produced is absorbed by the coal and later released from the coal seam and surrounding disturbed strata during the mining process. [http://www.coal.gov.uk/resources/cleanercoaltechnologies/CoalMineandbedmethane.cfm The Coal Authority ] ] Methane accounts for 9% of greenhouse gas emissions created through human activity. [ [http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html Greenhouse Gases, Climate Change, and Energy ] ]
According to the
Intergovernmental Panel on Climate Change, methane has a global warmingpotential 21 times greater than that of carbon dioxide on a 100 year time line. While burning coal in power plants is most harmful to air quality, due to the emission of dangerous gases, the process of mining can release pockets of hazardous gases. These gases may pose a threat to coal miners as well as a source of air pollution. This is due to the relaxation of pressure and fracturing of the strata during mining activity, which gives rise to serious safety concerns for the coal miners if not managed properly. The buildup of pressure in the strata can lead to explosions during or after the mining process if prevention methods, such as "methane draining", are not taken.
Strip mining severely alters the landscape, which damages environmental value in the surrounding land. [Hamilton, Michael S. "Mining Environmental Policy: Comparing Indonesia and the USA" (Burlington, VT: Ashgate, 2005).] Strip mining, or surface mining of coal completely eliminates existing vegetation, destroys the genetic soil profile, displaces or destroys wildlife and habitat, degrades air quality, alters current land uses, and to some extent permanently changes the general topography of the area mined. [U.S. Department of the Interior. 1979. "Permanent Regulatory Program Implementing Section 501(b) of the Surface Mining Control and Reclamation Act of 1977: Environmental Impact Statement". Washington, D.C.: U.S. Department of the Interior.] The community of micro organisms and nutrient cycling processes are upset by movement, storage, and redistribution of soil.
Generally, soil disturbance and associated compaction result in conditions conducive to erosion. Soil removal from the area to be surface mined alters or destroys many natural soil characteristics, and may reduce its productivity for agriculture or biodiversity. Soil structure may be disturbed by pulverization or aggregate breakdown.
Removal of vegetative cover and activities associated with construction of haul roads, stockpiling of topsoil, displacement of overburden and hauling of spoil and coal increase the quantity of dust around mining operations. Dust degrades air quality in the immediate area, can have adverse impacts on vegetative life, and may constitute a health and safety hazard for mine workers and nearby residents. The land surface, often hundreds of acres, is dedicated to mining activities until it can be reshaped and reclaimed. If mining is allowed, resident human populations must be resettled off the mine site, and economic activities such as agriculture or hunting and gathering food or medicinal plants are displaced, at least temporarily. What becomes of the land surface after mining is determined by the manner in which mining is conducted.
Surface mining can adversely impact the hydrology of a region. Deterioration of stream quality can result from acid mine drainage, toxic trace elements, high content of dissolved solids in mine drainage water, and increased sediment loads discharged to streams. Waste piles and coal storage piles can yield sediment to streams, and leached water from these piles can be acid and contain toxic trace elements. Surface waters may be rendered unfit for agriculture, human consumption, bathing, or other household uses. Controlling these impacts requires careful management of surface water flows into and out of mining operations.
Flood events can cause severe damage to improperly constructed or located coal haul roads, housing, coal crushing and washing plant facilities, waste and coal storage piles, settling basin dams, surface water diversion structures, and the mine itself. Besides the danger to life and property, large amounts of sediment and poor quality water may have detrimental effects many miles downstream from a mine site after a flood.
Ground water supplies may be adversely affected by surface mining. These impacts include drainage of usable water from shallow aquifers; lowering of water levels in adjacent areas and changes in flow directions within aquifers; contamination of usable aquifers below mining operations due to infiltration or percolation of poor quality mine water; and increased infiltration of precipitation on spoil piles. Where coal or carbonaceous shales are present, increased infiltration may result in increased runoff of poor quality water and erosion from spoil piles; recharge of poor quality water to shallow groundwater aquifers; or poor quality water flow to nearby streams. This may contaminate both ground water and nearby streams for long periods. Lakes formed in abandoned surface mining operations are more likely to be acid if there is coal or carbonaceous shale present in spoil piles, especially if these materials are near the surface and contain pyrites.
Surface mining of coal causes direct and indirect damage to wildlife. The impact on wildlife stems primarily from disturbing, removing, and redistributing the land surface. Some impacts are short-term and confined to the mine site; others may have far reaching, long term effects. The most direct effect on wildlife is destruction or displacement of species in areas of excavation and spoil piling. Mobile wildlife species like game animals, birds, and predators leave these areas. More sedentary animals like invertebrates, many reptiles, burrowing rodents and small mammals may be directly destroyed.
If streams, lakes, ponds or marshes are filled or drained, fish, aquatic invertebrates, and amphibians are destroyed. Food supplies for predators are reduced by destruction of these land and water species. Animal populations displaced or destroyed can eventually be replaced from populations in surrounding ranges, provided the habitat is eventually restored. An exception could be extinction of a resident endangered species.
Many wildlife species are highly dependent on vegetation growing in natural drainages. This vegetation provides essential food, nesting sites and cover for escape from predators. Any activity that destroys this vegetation near ponds, reservoirs, marshes, and wetlands reduces the quality and quantity of habitat essential for waterfowl, shore birds, and many terrestrial species. The commonly used head of hollow fill method for disposing of excess overburden is of particular significance to wildlife habitat in some locations. Narrow, steep sided, V shaped hollows near ridge tops are frequently inhabited by rare or endangered animal and plant species. Extensive placement of spoil in these narrow valleys eliminates important habitat for a wide variety of species, some of which may be rendered extinct.
Broad and long lasting impacts on wildlife are caused by habitat impairment. The habitat requirements of many animal species do not permit them to adjust to changes created by land disturbance. These changes reduce living space. The degree to which a species or an individual animal tolerates human competition for space varies. Some species tolerate very little disturbance. In instances where a particularly critical habitat is restricted, such as a lake, pond, or primary breeding area, a species could be eliminated.
Large mammals and other animals displaced from their home ranges may be forced to use adjacent areas already stocked to carrying capacity. This overcrowding usually results in degradation of remaining habitat, lowered carrying capacity, reduced reproductive success, increased interspecies and intraspecies competition, and potentially greater losses to wildlife populations than the number of originally displaced animals.
Removal of soil and rock overburden covering the coal resource, if improperly done, causes burial and loss of top soil, exposes parent material, and creates vast infertile wastelands. Pit and spoil areas are not capable of providing food and cover for most species of wildlife. Without rehabilitation, these areas must go through a weathering period, which may take a few years or many decades, before vegetation is established and they become suitable habitat. With rehabilitation, impacts on some species are less severe. Humans cannot immediately restore natural biotic communities. We can, however, assist nature through reclamation of land and rehabilitation efforts geared to wildlife needs. Rehabilitation not geared to the needs of wildlife species, or improper management of other land uses after reclamation, can preclude reestablishment of many members of the original fauna.
Degradation of aquatic habitats has often been a major impact from surface mining and may be apparent to some degree many miles from a mining site. Sediment contamination of surface water is common with surface mining. Sediment yields may increase 1000 times over their former level as a direct result of strip mining. In some circumstances, especially those involving disturbance of unconsolidated soils, approximately one acre foot of sediment may be produced annually for every 80 acres of disturbed land. [U.S. Department of the Interior. 1979. "Permanent Regulatory Program Implementing Section 501(b) of the Surface Mining Control and Reclamation Act of 1977: Environmental Impact Statement". Washington, D.C.: U.S. Department of the Interior.]
The effects of sediment on aquatic wildlife vary with the species and amount of contamination. High sediment loads can kill fish directly, bury spawning beds, reduce light transmission, alter temperature gradients, fill in pools, spread stream flows over wider, shallower areas, and reduce production of aquatic organisms used as food by other species. These changes destroy the habitat of some valued species and may enhance habitat for less desirable species. Existing conditions are already marginal for some freshwater fish in the United States. Sedimentation of these waters can result in their elimination. The heaviest sediment pollution of a drainage normally comes within five to 25 years after mining. In some areas, unrevegetated spoil piles continue to erode even 50 to 65 years after mining. [U.S. Department of the Interior. 1979. "Permanent Regulatory Program Implementing Section 501(b) of the Surface Mining Control and Reclamation Act of 1977: Environmental Impact Statement". Washington, D.C.: U.S. Department of the Interior.]
The presence of acid forming materials exposed as a result of surface mining can affect wildlife by eliminating habitat and by causing direct destruction of some species. Lesser concentrations can suppress productivity, growth rate, and reproduction of many aquatic species. Acids, dilute concentrations of heavy metals, and high alkalinity can cause severe wildlife damage in some areas. The duration of acidic waste pollution can be long term. Estimates of the time required to leach exposed acidic materials in the Eastern United States range from 800 to 3000 years. [U.S. Department of the Interior. 1979. "Permanent Regulatory Program Implementing Section 501(b) of the Surface Mining Control and Reclamation Act of 1977: Environmental Impact Statement". Washington, D.C.: U.S. Department of the Interior.]
In some situations, surface mining may have beneficial impacts on some wildlife. Where large, continuous tracts of forest, bush land, sagebrush, or grasslands are broken up during mining, increased edges and openings are created. Preferred food and cover plants can be established in these openings to benefit a wide variety of wildlife. Under certain conditions, creation of small lakes in the mined area may also be beneficial. These lakes and ponds may become important water sources for a variety of wildlife inhabiting adjacent areas. Many lakes formed in mine pits are initially of poor quality as aquatic habitat after mining, due to lack of structure, aquatic vegetation, and food species. They may require habitat enhancement and management to be of significant wildlife value.
Surface mining operations and coal transportation facilities are fully dedicated to coal production for the life of a mine. Mining activities incorporating little or no planning to establish postmining land use objectives usually result in reclamation of disturbed lands to a land use condition not equal to the original use. Existing land uses such as livestock grazing, crop and timber production are temporarily eliminated from the mining area. High value, intensive land use areas like urban and transportation systems are not usually affected by mining operations. If mineral values are sufficient, these improvements may be removed to an adjacent area.
Surface mining operations have produced cliff-like highwalls as high as 200 feet in the United States. Such highwalls may be created at the end of a surface mining operation where stripping becomes uneconomic, or where a mine reaches the boundary of a current lease or mineral ownership. These highwalls are hazards to people, wildlife, and domestic livestock. They may impede normal wildlife migration routes. Steep slopes also merit special attention because of the significance of impacts associated with them when mined. While impacts from contour mining on steep slopes are of the same type as all mining, the severity of these impacts increase as the degree of slope increases. This is due to increased difficulties in dealing with problems of erosion and land stability on steeper slopes.
Fires sometimes occur in coal beds underground. When coal beds are exposed, the fire risk is increased. Weathered coal can also increase ground temperatures if it is left on the surface. Almost all fires in solid coal are ignited by surface fires caused by people or lightning. Spontaneous combustion is caused when coal oxidizes and air flow is insufficient to dissipate heat, but this occurs only in stockpiles and waste piles, not in bedded coals underground. Where coal fires occur, there is attendant air pollution from emission of smoke and noxious fumes into the atmosphere. Coal seam fires may burn underground for decades, threatening destruction of forests, homes, schools, churches, roadways and other valuable infrastructure. Spontaneous combustion is common in coal stockpiles and refuse piles at mine sites.
Adverse impacts on geological features of human interest may occur in a surface mine area. Geomorphic and geophysical features and outstanding scenic resources may be sacrificed by indiscriminate mining. Paleontological, cultural, and other historic values may be endangered due to disruptive activities of blasting, ripping, and excavating coal. Stripping of overburden eliminates and destroys all archeological and historic features unless they are removed beforehand.
Extraction of coal by surface mining disrupts virtually all esthetic elements of the landscape, in some cases only temporarily. Alteration of land forms often imposes unfamiliar and discontinuous configurations. New linear patterns appear as material is extracted and waste piles are developed. Different colors and textures are exposed as vegetative cover is removed and overburden dumped to the side. Dust, vibration, and diesel exhaust odors are created, affecting sight, sound, and smell. Some members of local communities may find such impacts disturbing or unpleasant.
Due to intensive mechanization, surface mines may require fewer workers than underground mines with equivalent production. The influence on human populations from surface mining is therefore not generally as significant as with underground mines. In low population areas, however, local populations cannot provide needed labor so there is migration to the area because new jobs are available at a mine. Unless adequate advance planning is done by government and mine operators, new populations may cause overcrowded schools, hospitals and demands on public services that cannot easily be met. Some social instability may be created in nearby communities by surface coal mining.
Many impacts can be minimized but may not be eliminated entirely by use of best mining practices either voluntarily or to comply with government regulatory programs. Financial incentives to minimize costs of production may minimize use of best mining practices in the absence of effective regulation. Some temporary destruction of the land surface is an environmental price we pay for utilization of coal resources. The scale of disturbance, its duration, and the quality of reclamation are largely determined by management of the operation during mining.
Mountaintop removalto remove coal is a large-scale negative change to the environment. Tops are removed from mountains or hills to expose thick coal seams underneath, and the soil and rock removed is deposited in nearby valleys, hollows and depressions, resulting in blocked and sometimes contaminated waterways. In some areas of the world, remediation is often delayed for decades.
One of the legacies of coal mining is the low coal content waste forming
slag heaps. In addition, all forms of mining are likely to generate areas where coal is stacked and where the coal has significant sulfurcontent, such coal heaps generate highly acidic, metal-laden drainage when exposed to rainfall. These liquors can cause severe environmental damage to receiving water-courses. [ [http://www.worldcoal.org/pages/content/index.asp?PageID=126 World Coal Institute - Environmental Impacts of Coal Mining ] ] Coal mining releases approximately twenty toxic release chemicals, of which 85% is said to be managed on site.Fact|date=October 2007
Mining operations in the United States must, under federal and state law, meet standards for protecting surface and ground waters from contamination, including AMD. To mitigate these problems, water is continuously monitored at coal mines. The five principal technologies used to control water flow at mine sites are:
*groundwater pumping systems,
*subsurface drainage systems,
In the case of AMD, contaminated water is generally pumped to a treatment facility that neutralizes the contaminants.
Mine collapses, or mine subsidences, have a potential for major effects aboveground, which are especially devastating in built-up areas. German underground coal-mining, especially in
North Rhine-Westphalia, has damaged thousands of houses, and the coal mining industries have set aside many millions in funding for future subsidence damages as part of their insurance and state subsidy schemes.Fact|date=February 2008
In a particularly spectacular case in the German
Saarregion, another historical coal mining area, a suspected mine collapse in 2008 created an earthquake of force 4.0 on the Richter magnitude scale, causing some limited damage to houses. Previous smaller earthquakes had been increasingly common. Coal mining was temporarily suspended in the area. [" [http://www.reuters.com/article/environmentNews/idUSL2465800820080224 Mining sets off earthquake in west Germany] " - " Reuters", Sunday 24 February]
Combustionof coal, like any other fossil fuel, occurs due to an exothermic reaction between the components of the fuel source and the components of the air surrounding it. Coal is made primarily of carbon, but also contains sulfur, oxygen and hydrogen. The reaction between coal and the air surrounding it produces oxides of carbon, usually carbon dioxide (CO2 - an important greenhouse gas) in a complete combustion, along with oxides of sulfur, mainly sulfur dioxide(SO2), and various oxides of nitrogen (NOx). Because of the hydrogen and nitrogen components of air, hydrides and nitrides of carbon and sulfur are also produced during the combustion of coal in air. These could include hydrogen cyanide(HCN), sulfur nitrate(SNO3) and many other toxic substances.
Further, acid rain may occur when the sulfur dioxide produced in the combustion of coal, reacts with oxygen to form
sulfur trioxide(SO3), which then reacts with water molecules in the atmosphere to form sulfuric acid(see Acid anhydridefor more information). The sulfuric acid (H2SO4) is returned to the Earth as acid rain. Flue gas desulfurizationscrubbing systems, which use limeto remove the sulfur dioxide can reduce or eliminate the likelihood of acid rain.
However, another form of acid rain is due to the carbon dioxide emissions of a coal plant. When released into the atmosphere, the carbon dioxide molecules react with water molecules, to produce
carbonic acid(H2CO3). This, in turn, returns to the earth as a corrosive substance. This cannot be prevented as easily as sulfur dioxide emissions.
coal-fired power plants represents one of the two largest sources of carbon dioxide emissions, which are the main cause of global warming. Coal mining and abandoned mines also emit methane, another cause of global warming. Since the carbon content of coal is higher than oil, burning coal is a serious threat to the stability of the global climate, as this carbon forms CO2 when burned. Many other pollutants are present in coal power station emissions, as solid coal is more difficult to clean than oil, which is refined before use. A study commissioned by environmental groups claims that coal power plant emissions are responsible for tens of thousands of premature deaths annually in the United States alone.Fact|date=July 2008 Modern power plants utilize a variety of techniques to limit the harmfulness of their waste products and improve the efficiency of burning, though these techniques are not subject to standard testing or regulation in the U.S. and are not widely implemented in some countries, as they add to the capital cost of the power plant.Fact|date=July 2008 To eliminate CO2 emissions from coal plants, carbon capture and storagehas been proposed but has yet to be commercially used.
Coal and coal waste products, including
fly ash, bottom ash, and boiler slag, contain many heavy metals, including arsenic, lead, mercury, nickel, vanadium, beryllium, cadmium, barium, chromium, copper, molybdenum, zinc, seleniumand radium, which are dangerous if released into the environment. Coal also contains low levels of uranium, thorium, and other naturally-occurring radioactive isotopeswhose release into the environment may lead to radioactive contamination. [cite web | title=Coal Combustion | url=http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html | accessmonthday= September 9 | accessyear= 2005 ] [cite web | title=Radioactive Elements in Coal and Fly Ash, USGS Factsheet 163-97 | url=http://greenwood.cr.usgs.gov/energy/factshts/163-97/FS-163-97.html | accessmonthday= September 9 | accessyear= 2005 ] While these substances are trace impurities, enough coal is burned that significant amounts of these substances are released, resulting in more radioactive wastethan nuclear power plants. [cite web | title=Coal Combustion: Nuclear Resource or Danger | url=http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html | accessmonthday=October 16 | accessyear=2006] Mercury emissions from coal burning are concentrated as they work their way up the food chain and converted into methylmercury, a toxic compound [cite web |url=http://pubs.usgs.gov/fs/fs-016-03/ |title= Mercury in stream ecosystems—new studies initiated by the U.S. Geological Survey |author= Brigham ME, Krabbenhoft DP, Hamilton PA |date=2003 |accessdate=2008-01-31 |publisher= U.S. Geological Survey] that harms people who consume freshwater fish. [cite web |url=http://www.smithsonianmag.com/specialsections/ecocenter/mercury.html |title= Mystery at sea |work=Smithsonian.com |author= Jaffe E |date=2007 |accessdate=2008-01-31] Ocean fish account for the majority of human exposure to methylmercury; the sources of ocean fish methylmercury are not well understood. [cite web |url=http://www.smithsonianmag.com/specialsections/ecocenter/mercury.html |title= Mystery at sea |work=Smithsonian.com |author= Jaffe E |date=2007 |accessdate=2008-01-31]
Coal provides most of China's current power, both for residential electricity and industry. China is hoping to move to nuclear power as it is cleaner and can deliver large amounts of power with a small amount of input fuel.
By the late 1930s, it was estimated that American coal mines produced about 2.3 million tons of sulfuric acid annually. In the Ohio River Basin, where twelve hundred operating coal mines drained an estimated annual 1.4 million tonnes of sulfuric acid into the waters in the 1960s and thousands of abandoned coal mines leached acid as well. In Pennsylvania alone, mine drainage had blighted 2,000 stream miles by 1967.
In response to negative land effects of coal mining and the abundance of abandoned mines in the USA, the federal government enacted the
Surface Mining Control and Reclamation Act of 1977, which requires reclamationplans for future coal mining sites. Reclamation plans must be approved and permitted by federal or state authorities before mining begins. [U.S. Department of the Interior. 1979. "Permanent Regulatory Program Implementing Section 501(b) of the Surface Mining Control and Reclamation Act of 1977: Environmental Impact Statement". Washington, D.C.: U.S. Department of the Interior.] As of 2003, over 2 million acres (8,000 km²) of previously mined lands have been reclaimed in the United States.
List of environmental issues
* [http://www.worldcoal.org/pages/content/index.asp?PageID=126 World Coal Institute - Environmental Impacts of Coal Mining]
* [http://www.msnbc.msn.com/id/5174391/ MSNBC report on coal pollution health effects in the United States]
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