The environmental impact of the coal industry is widespread.[1] Legislation passed by the U.S. Congress in 1990 required the United States Environmental Protection Agency (EPA) to issue a plan to alleviate toxic pollution from coal-fired power plants. After delay and litigation, the EPA had a court-imposed deadline of March 16, 2011, to issue its report; however, the Obama administration has acknowledged that final regulations will not be issued until the end of 2011 at the earliest.[2]
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Coal mining causes 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; as long as rain falls on the mine tailings the 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; this leaves the subsoil infertile on the surface and begins to pollute streams by acidifying and killing fish, plants, and aquatic animals which are sensitive to drastic pH shifts.
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 pressure 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.[3] Methane accounts for 10.5 percent of greenhouse-gas emissions created through human activity.[4]
According to the Intergovernmental Panel on Climate Change, methane has a global warming potential 21 times greater than that of carbon dioxide over a 100-year timeline. 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.[3]
Wherever it occurs in the world strip mining severely alters the landscape, which reduces the value of the natural environment in the surrounding land.[5] 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.[6] The community of microorganisms 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 reduces its biodiversity and productivity for agriculture. Soil structure may be disturbed by pulverization or aggregate breakdown.
The removal of vegetative cover and activities associated with the construction of haul roads, stockpiling of topsoil, displacement of overburden and hauling of soil and coal increase the quantity of dust around mining operations. Dust degrades air quality in the immediate area, has an adverse impact on vegetative life, and constitutes health and safety hazards 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; economic activities, such as agriculture or hunting and gathering food and medicinal plants are interrupted (at least temporarily). What becomes of the land surface after mining is determined by the manner in which the mining is conducted.
Surface mining adversely impacts the hydrology of a region. Deterioration of stream quality results 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.[7]
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. Overall, it causes pollution in drinking water. Open-pit mining requires large amounts of water for coal preparation plants and dust suppression. To meet this requirement mines acquire (and remove) surface or groundwater supplies from nearby agricultural or domestic users, which reduces the productivity of these operations or halts them. These water resources (once separated from their original environment) are rarely returned after mining, creating a permanent degradation in agricultural productivity. Underground mining has a similar (but lesser) effect, due to a lower need for dust-suppression water; however, it still requires sufficient water for coal-washing.
Groundwater 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 direction within aquifers; contamination of usable aquifers below mining operations due to infiltration (percolation) of poor-quality mine water; and increased infiltration of precipitation on spoil piles. Where coal (or carbonaceous shale) is present, increased infiltration may result in:
This may contaminate both groundwater 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. Sulphuric acid is formed when minerals containing sulphide are oxidised through air contact; this causes acid rain. Leftover chemical deposits from explosives are toxic and increase the salt content of mine water, contaminating it.
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 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, reptiles, burrowing rodents and small mammals may be 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 would be the extinction of a resident endangered species.
Many wildlife species are highly dependent on vegetation growing in natural drainage areas. This vegetation provides essential food, nesting sites and cover from predators. Activity destroying this vegetation near ponds, reservoirs, marshes and wetlands reduces the quality and quantity of habitat essential for waterfowl, shorebirds and terrestrial species. The commonly-used head-of-hollow fill method for disposing of excess overburden is of particular significance to wildlife habitat. 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 habitat for a wide variety of species, some of which may be driven to extinction.
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, and some species can 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. The range of damage possible is wide.
Large mammals and other animals displaced from their home ranges may be forced to use adjacent areas, already stocked to their carrying capacity. This overcrowding results in degradation of remaining habitat, lowered carrying capacity, reduced reproductive success, increased inter- and intra-species competition, and potentially greater losses to wildlife populations than the number of originally-displaced animals.
Degradation of aquatic habitats is a major impact by surface mining, and may be apparent many miles from a mining site. Sediment contamination of surface water is common with surface mining. Sediment yields may increase a thousand times times their former level as a result of strip mining.[8]
Preferred food and cover plants can be established in these openings to benefit a 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 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.
Removal of soil and rock overburden covering the coal resource (if improperly done) causes burial and loss of topsoil, exposes parent material, and creates large infertile wastelands. Pit and spoil areas are not capable of providing food and cover for most species of wildlife. Without rehabilitation, these areas must undergo a weathering period (which may take a few years to 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; they 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 the original fauna.
Surface-mining operations and coal transportation facilities are dedicated to coal production for the life of a mine. Mining activities incorporating little or no planning to establish post-mining 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.
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 airflow is insufficient to dissipate heat; this more commonly occurs in stockpiles and waste piles, rarely in bedded coal 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, roadways and other valuable infrastructure. The best-known coal-seam fire may be the one which led to the permanent evacuation of Centralia, Pennsylvania, United States.[9]
The burning of coal leads to substantial fly ash sludge-storage ponds. These can give way, as one did at the Kingston Fossil Plant in December 2008.
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 the disruptive activities of blasting, ripping, and excavating coal. Stripping of overburden eliminates and destroys archeological and historic features, unless they are removed beforehand.
Extraction of coal by surface mining disrupts virtually all aesthetic elements of the landscape. Alteration of landforms 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). Residents of local communities often 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 the needed labor; there is migration to the area, because jobs are available at a mine. Unless adequate 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 not eliminated entirely) by the use of best mining practices, either voluntarily or to comply with government regulatory programs. Financial incentives to minimize costs of production may minimize the use of best mining practices in the absence of effective regulation. Destruction of the land surface is an environmental price humans pay to utilize coal resources. The scale of disturbance, its duration, and the quality of reclamation are largely determined by management of the operation during mining.
Mountaintop removal to remove coal is a large-scale negative change to the environment. Tops are removed from mountains or hills to expose thick coal seams underneath. The soil and rock removed is deposited in nearby valleys, hollows and depressions, resulting in blocked (and contaminated) waterways. In some parts of the world, remediation is delayed for decades.
One of the legacies of coal mining is the low-coal-content, waste-forming spoil tip. In addition, all forms of mining are likely to generate areas where coal is stacked and where the coal has significant sulfur content. Such coal heaps generate highly acidic, metal-laden drainage when exposed to rainfall. These liquids can cause severe environmental damage to receiving watercourses.[10] Coal mining releases approximately 20 toxic-release chemicals.
Mine collapses (or mine subsidences) have the potential to produce major effects above ground, which are especially devastating in developed areas. German underground coal-mining (especially in North Rhine-Westphalia) has damaged thousands of houses, and the coal-mining industries have set aside large sums in funding for future subsidence damages as part of their insurance and state-subsidy schemes. In a particularly spectacular case in the German Saar region (another historical coal-mining area), a suspected mine collapse in 2008 created an earthquake measuring 4.0 on the Richter magnitude scale, causing some damage to houses. Previously, smaller earthquakes had become increasingly common and coal mining was temporarily suspended in the area.[11]
The combustion of coal, like any other fossil fuel, is an exothermic reaction between the fuel source and (usually) oxygen. Coal is made primarily of carbon, but also contains sulfur, oxygen, hydrogen, and nitrogen. During combustion, the reaction between coal and the air produces oxides of carbon, including carbon dioxide (CO2 (an important greenhouse gas)), oxides of sulfur (mainly sulfur dioxide) (SO2), and various oxides of nitrogen (NOx). Because of the hydrogenous and nitrogenous components of coal, hydrides and nitrides of carbon and sulfur are also produced during the combustion of coal in air. These include hydrogen cyanide (HCN), sulfur nitrate (SNO3) and other toxic substances. Coal is the largest contributor to the human-made increase of CO2 in the atmosphere.[12] Further, acid rain may occur when sulfur dioxide produced by the combustion of coal reacts with oxygen to form sulfur trioxide (SO3); this reacts with water molecules in the atmosphere to form sulfuric acid. The sulfuric acid (H2SO4) returns to earth as acid rain. Flue-gas desulfurization scrubbing systems, which use lime to remove sulfur dioxide, can reduce the likelihood of acid rain.
However, another form of acid rain is due to carbon dioxide emissions of a coal plant. When released into the atmosphere, the carbon dioxide molecules react with water molecules, to slowly 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 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, selenium and radium), which are dangerous if released into the environment. Coal also contains low levels of uranium, thorium, and other naturally-occurring radioactive isotopes whose release into the environment may lead to radioactive contamination.[13][14] While these substances are trace impurities, enough coal is burned that significant amounts of these substances are released.[13]
The radioactive trace impurities mentioned above expose plant operators to radiation levels above background levels but below that experienced by nuclear power plant workers. John Gofman, M.D., Ph.D, (Professor Emeritus of Medical Physics at the University of California, Berkeley, and the co-discoverer of uranium-233) compared the radiation dose per megawatt-year from operation of a nuclear generating unit to the radiation dose from operation of a coal-fired unit and found that the dose from natural nucleides associated with nuclear power would be 35-81 times higher than the dose from coal.[15] When comparing the radiation impact of coal and nuclear plants on the surrounding environment, however, coal-plant wastes are more radioactive than the waste generated by nuclear plants producing the same amount of energy. Plant-emitted radiation carried by coal-derived fly ash delivers 100 times more radiation to the surrounding environment than does the normal operation of a similarly-productive nuclear plant.[16]
Mercury emissions from coal burning are concentrated as they work their way up the food chain and are converted into methylmercury, a toxic compound[17] which harms people who consume freshwater fish. In New York State winds bring mercury from the coal-fired power plants of the Midwest, contaminating the waters of the Catskill Mountains. The mercury is consumed by worms, who are eaten by fish, who are eaten by birds (including bald eagles). As of 2008, mercury levels in bald eagles in the Catskills had reached new heights.[18] Ocean fish account for the majority of human exposure to methylmercury; the sources of ocean fish methylmercury are not well understood.[19] Coal-fired power plants shorten nearly 24,000 lives a year in the United States (2,800 from lung cancer).[20]
In 2008 James E. Hansen and eight other scientists published "Target Atmospheric CO2: Where Should Humanity Aim?",[21] calling for the complete phase-out of coal power by 2030.
In 2008 Pushker Kharecha and James E. Hansen published a peer-reviewed scientific study analyzing the effect of a coal phase-out on atmospheric CO2 levels.Their baseline mitigation scenario was a phaseout of global coal emissions by 2050. The authors describe their scenario:
The second scenario, labeled Coal Phase-out, is meant to approximate a situation in which developed countries freeze their CO2 emissions from coal by 2012 and a decade later developing countries similarly halt increases in coal emissions. Between 2025 and 2050 it is assumed that both developed and developing countries will linearly phase out emissions of CO2 from coal usage. Thus in Coal Phase-out we have global CO2 emissions from coal increasing 2% per year until 2012, 1% per year growth of coal emissions between 2013 and 2022, flat coal emissions for 2023–2025, and finally a linear decrease to zero CO2 emissions from coal in 2050. These rates refer to emissions to the atmosphere and do not constrain consumption of coal, provided the CO2 is captured and sequestered. Oil and gas emissions are assumed to be the same as in the BAU [Business as Usual] scenario.[22]
Kharecha and Hansen also consider three other mitigation scenarios, all with the same coal phase-out schedule but each making different assumptions about the size of oil and gas reserves and the speed at which they are depleted. Under the Business as Usual scenario, atmospheric CO2 peaks at 563 parts per million (ppm) in the year 2100. Under the four coal phase-out scenarios, atmospheric CO2 peaks at 422–446 ppm between 2045 and 2060 and declines thereafter. The key implications of the study are:
In the Greenpeace and EREC's Energy (R)evolution scenario,[23] the world could eliminate all fossil-fuel use by 2090 [24][25][26]
Information regarding pollution from coal-fired power stations is available from the publicly-accessible National Pollutant Inventory database overseen by the Australian government.
Coal provides most of China's power as of 2011, both for residential electricity and industry. China hopes to convert to nuclear power, since 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, 1,200 operating coal mines drained an estimated annual 1.4 million tonnes of sulfuric acid into the drainage basin during the 1960s; 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 US the federal government enacted the Surface Mining Control and Reclamation Act of 1977, which requires reclamation plans for future coal mining sites. These plans must be approved by federal or state authorities before mining begins.[6] As of 2003, over 2 million acres (8,000 km2) of previously-mined lands have been reclaimed in the United States.
Emissions from coal-fired power plants represents one of the two largest sources of carbon dioxide emissions (the primary 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 global climate stability; this carbon forms CO2 when burned. Many other pollutants are present in coal-power-station emissions; solid coal is more difficult to clean than oil, which is refined before use. A study by the Clean Air Task Force claims that coal-power-plant emissions are responsible over 13,000 premature deaths annually in the United States alone.[27] Modern power plants utilize a variety of techniques to limit the harm of their waste products and improve the efficiency of burning; however, these techniques are not subject to standardized 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. To eliminate CO2 emissions from coal plants, carbon capture and storage has been proposed but as of 2011 has not been commercially used.
The effects of sediment on aquatic wildlife vary with the species and the amount of contamination. High sediment levels can kill fish directly, bury spawning beds, reduce light transmission, alter temperature gradients, fill in pools, spread streamflows over wider, shallower areas, and reduce production of aquatic organisms used as food by other species. These changes destroy the habitat of valued species, and may enhance habitat for less-desirable species. Existing conditions are already marginal for some freshwater fish in the United States, and the sedimentation of their habitat may result in their extinction. The heaviest sediment pollution of a drainage normally comes within 5 to 25 years after mining. In some areas, unvegetated spoil piles continue to erode even 50 to 65 years after mining.[6]
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 damage to wildlife in some areas. The duration of acidic-waste pollution can be long; estimates of the time required to leach exposed acidic materials in the Eastern United States range from 800 to 3,000 years.[6]
Surface-mining operations have produced cliff-like highwalls as high as 200 feet (61 m) in the United States. Such highwalls may be created at the end of a surface-mining operation when 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, and may block wildlife-migration routes. Steep slopes also merit special attention because of the significance of impacts associated with them when mined. While the impact from contour mining on steep slopes are of the same type as all mining, the severity of these impacts increases with the degree of slope. This is due to increased difficulty in dealing with erosion and land stability on steeper slopes.
Mining operations in the United States must (under federal and state law) meet standards for protecting surface and groundwater from contamination (including acid mine drainage, or AMD). To mitigate these problems, water is monitored at coal mines. The five principal technologies used to control water flow at mine sites are:
In the case of AMD, contaminated water is generally pumped to a treatment facility which neutralizes its contaminants.
The Environmental Protection Agency classified the 44 sites as potential hazards to communities (which means the waste sites could cause death and significant property damage if an event such as a storm, a terrorist attack or a structural failure caused a spill). They estimate that about 300 dry landfills and wet storage ponds are used around the country to store ash from coal-fired power plants. The storage facilities hold the noncombustible ingredients of coal and the ash trapped by equipment designed to reduce air pollution.[28]
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