This report explains the environmental impacts in coal mining industry. In the process of development coal mining pollutes the environment. But at the same time it also assures the energy to generate electricity which is indispensable for the development of any country.
We are focusing on the impact of air quality, mine fires, noise, water regime and land during the operations of coal mining. Opencast and underground mining both methods affects the environment, especially water resources.
The goal of coal mining is to economically remove coal from the ground. Coal is valued for its energy content, and since the 1880s is widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from iron ore and for cement production.
Coal is the most important fossil fuel around the world and vital for its energy security. In the process of development, coal mining is one of the major industries, which is contributing accidentally towards the pollution of the environment. The power sector is the bigger consumer followed by industrial sector (steel and cement manufacturing units). It also assures the energy supply which is important for any countries development. Coal is still remains essential in producing a diverse and balanced energy mix. It is a major fuel generating electricity worldwide. Coal is poised with different toxics which effect the environment and one of the key challenges coal industries is facing today.
Coal is less effective and energy efficient compared to other fossil fuels and pollutes more as well. The main concerns is to focus at the regional level to do with the environmental impacts on air, water, land, forest, climate and the costs of mitigating these. Even with these concerns coal will remain a future mainstay. The coal mining industry finds it difficult to meet current needs as a bridge to meet future goal through the enhancement of knowledge and technology. The challenge is to apply the right technology in the most efficient and environmentally friendly way .
Most of the mining operations carried out underground and opencast mines like drilling, blasting, extraction transportation and crushing. These operations damage the environment and ecology to an unacceptable extent. Sometimes rapid and unchecked activities results in air, water and noise pollution, land degradation, health hazards, loss of forest wealth and agriculture land, drying of wells, rehabilitation problems lending to large scale environmental deterioration . Environmental issues should observe and controlled by appropriate planning and study. A balance is required between mining and environment. In addition, due to excessive mining, chances of accidents increase which lead to misery and tragedy .
Impact of Mining on Air Quality
Air pollution happened in mines due to the runaway emissions of particulate matter and gases including methane, sulphur dioxide, oxides of nitrogen and carbon monoxide. Mining operations produce a lot of dust. The drilling, loading, transporting, blasting, hauling, and crushing mainly produce dust in major operations. They dust sources in mines can be categorized as primary sources that generate the dust and secondary sources, which disperse the dust and carry it from place to place called as fugitive dust .
Opencast mining has severe impact on air pollution as compared to underground mining. In underground mining men suffer from dust inside underground mine workings. But opencast mining create much more air quality deterioration in respect of dust and gaseous pollutants. It creates air pollution problem not only within the mining premises but also in surrounding residential area affecting abundant air quality.
High levels of suspended particulate matter increase respiratory diseases such as chronic bronchitis and asthma cases while gaseous emissions contribute towards global warming besides causing health hazards to the exposed population . The dust which is uncontrollable creates serious health hazards and also affects the productivity creating poor visibility, increased maintenance cost, breakdown of equipment and ultimately deteriorates the ambient air quality in and around the mining site. The dust can also pollute nearby surface waters and stunt crop growth by shading and clogging the pores of the plants . Besides polluting the environment, the generation of dust means the loss of fines, which act as road surface binders. The vehicular traffic on haul roads has been identified as the most important cause of fugitive dust emissions .
The increase in the earth's surface temperature due to the presence of certain gases in the atmosphere called greenhouse effect . These gases are building up by human activities by extracting various minerals from the earth. The combustion of coal produces CO2 like other fossil fuels, this gas affect the greenhouse effect which is linked to global warming.
The coal combustion produces gaseous emissions of nitrous oxides (NOx) and sulphur dioxide (SO2) that produces 'ground level ozone' and 'acid rain'. SO2 and NOx gases react in the atmosphere with oxygen, water and other chemicals to form acidic compounds. Ground level ozone (O3) is mainly responsible for smog that forms a brown haze over cities. Ground level ozone is formed when NOx gases react with other chemicals in the atmosphere and is enhanced by strong sunlight . Emissions of SO2 and NOx are termed trans-boundary air pollution because the environmental impacts from the production of these gases are not restricted by geographical boundaries .
Impact of Mining on Water regime
Mining activities not only use a lot of water but it also affect the hydrological regime in the region and can affect the water quality.
Disturbance to hydrologic regime
The deep and large opencast mines have greater impact on the hydrologic regime in the region. With deforestation over the mine leasehold and changes brought about in the watershed characteristics, water flow in many streams in mining regions, is known to have dwindled and some perennial streams have turned into seasonal streams and others have receded . The most important impact in large and deep opencast mine is on the ground water regime of the region. The water seeping into the mine and collected in the mine sump is partly used up in the mine and the excess amount is discharged into the surface drainage system . The water used up in the mine for spraying on haul roads, conveyors, at loading and unloading points, bunkers etc. are lost by evaporation. A deep mine is likely to have longer haul roads requiring more spraying water. The water used for green belts and plantation areas are also lost by evapo-transpiration . A part of the water discharged into the surface drainage system seeps into the ground and partially replenishes the loss of ground water caused by mine seepage but the proportion is generally very low.
Many countries face the problem of over exploitation of ground water resources results in alarming lowering of water table . The major focus is taken to estimating the water need and the mines for future to apply constraints on water use and discharge.
The opportunity to re-use the water for drinking or agriculture purposes from surface and underground mines. Women in particular should be protected from potentially diminished water supplies. Mining companies should be a partner with the community in integrated water management. If mining diminishes the local water supply, then that water needs to be replaced .
To reduce the impact on the surface water bodies and surface drainage system, the surface layout for the underground and opencast should be planned and well managed. Underground and opencast mines should be planned with provisions for the development of underground and surface water bodies so that in the post mining period water in sufficient quantity is available for various uses . In both the opencast and underground mines water is pumped out of the mines. This water should be planned for treatment so that the requirement for domestic and industrial uses can be met.
Acid Mine Drainage
Acidic water damages the water severely and produces water pollution problems. Acid Mine Drainage (AMD) refers to distinctive types of waste bodies that originate from the weathering and leaching of sulphide minerals present in coal and associated strata . Environmental effects of AMD include contamination of drinking water and disrupted growth and reproduction of aquatic plants and animals. Effects of AMD related to water pollution include the killing of fish and loss of aquatic life and corrosion of mining equipments and structures such as barges, bridges and concrete materials .
AMD is the most persistent pollution problems in mines of North Eastern Coalfield. Generally, water quality characteristics of acidic mine water reflect high acidity and high hardness along with high iron and sulphate contents . Various toxic trace/ heavy metals become soluble in acidic water and may be presenting significant to concentration levels depending upon their availability in the source material . Fortunately the considerable majority of coal mining areas are safe and only in a few localized areas problem of AMD exists. AMD cripples the economy of mines due to compliance of stringent environmental standards and involves huge cost burden in its management .
Augmentation of pumped out mine water from coal/Lignite mines
The mining industry has to discharge millions of litres of water every day to the adjacent watercourses and thereby may cause water pollution in and around the mining areas . This water, otherwise a valuable water resource because of acceptable quality, becomes contaminated with various domestic and industrial trade effluents and subsequently is just wasted while putting on an extra cost burden on the underground mines . Further costs are incurred on abstraction of water from adjoining surface water bodies containing this water and additional costs are required for the treatment to meet the water quality objective criteria . It is emphasized here to augments and protects this precious ground water availability of nearly acceptable quality to meet various water demands particularly drinking water of already affected mining population . Augmentation of pumped out mine water from coal/Lignite mines for various water supplies particularly for potable purpose should be the prime goal of the concerned mining authority in the already drought prone thickly populated mining areas .
Heavy Metal Pollution
The heavy metals are important component of pollutants which not only cause phytotoxicity but also enter into food chain causing hazardous impacts on human health and animals. Human biology is full of instances where heavy metals toxicity has led to mass death . Heavy metal pollution is quite prevalent in acidic mine water situations. Mining and Milling operations, together with grinding, concentrating ores and disposal of tailings, provide obvious sources of contamination in the surface environment, along with mine and mill waste water. As a result, elevated levels of heavy metals can be found in and around metalliferous mines due to discharge and dispersion of mine wastes into nearby agricultural soils, food crops and stream systems . Eventually, they may pose a potential health risk to residents in the vicinity of mining areas. The extent and degree of heavy metal contamination around the mines vary depending upon geochemical characteristics and mineralization of tailings.
Water Pollution from seepage, waste dumps and mine benches
Major water pollution problem occurs due to erosion of mine benches, overburden and reject dumps and failing dams . The soil particles are carried away during the heavy rains due to deforestation and baring of ground. The blasted material in overburden and mine benches contain fine particles, which are also carried away by the rainwater . Many chemicals also enter the water streams in dissolved state. These sediment-carrying effluents are responsible for siltation of agricultural fields and chocking of streams and rivers on the downstream. Surface and ground water pollution, is a common feature of mining and associated processing activities . Runoff from dumps and exposed mine surface carries fine sediments in suspension, which is deposited on downstream valleys and agricultural fields.
Impact of Coal Mine Fire
Most of the coal mines are affected by fires which leads the steady destruction of energy resource. The reason for mine fires presumably involves the phenomenon of spontaneous heating through two interrelated processes viz., the oxygen coal interaction or oxidative process and the thermal process . If the fire remains uncontrolled, it can spread further through the pathways and crack in the strata. Mine fires give hike to several environmental problems besides economic losses and safety hazards. Apart from direct losses due to burning of coal, the other associated hazards encountered are :
Difficult geo-mining conditions
Sterilization of coal
Hindrance to production
Damage structure and adjacent properties
The adverse impacts of mine fires are observed on all the four basic components of the environment viz. Air, water, land and population. Mine fires pollute the atmosphere to a greater extent and have a bad impact on air. The effects are severe on air once the fire becomes surface fires. The pollutants released from mine fires mainly comprise of gases like carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), sulphur dioxide (SO2), saturated and unsaturated hydrocarbons, hydrogen sulphides (H2S) and other photosensitive oxidants apart from particulate matter . Un-burnt hydrocarbons in presence of NOx and other oxidants produce eye irritation.
Impact of Mining on Land
The type of mining operation used for extracting coal, mining constantly results in enormous land disturbance- e.g. large scale excavation, creation of derelict land, removal of top soil, dumping of solid wastes, cutting of roads, etc . The mining industry is not eager to re-handle the overburden material for economic reasons but you can see in few cases they planned to re-handle the material to fill the empty space created at the end of mining, and probably this practice will become more common and spread in future.
Opencast mining has bigger impact on land compared to underground mining. With new and improved technology, opencast coal mining is used commonly because it is cost effectiveness and productivity in large-scale land disturbance. Underground mining has considerably less impact than opencast mining on land . The surface settling impose several damages to engineering structures such as bridges, highways, buildings and drainage besides interfering with ground water regime.
Impact of Mining on ecology
The mining results the significant area of land devalued and existing ecosystem are replaced by unwanted wastes. The extraction process of mineral drastically alters the biological and physical nature of the mining area. Commonly practiced strip-mining to recover coal reserves, causes extensive soil damage, destroys vegetation and destroy and alter microbial community. In the process of removing desired mineral material, the original vegetation is inevitably destroyed and soil is lost or buried by waste . We are usually confronted with a complete absence of soil, in either a pedagogical or a biological sense, and what is left is just a skeleton full of limiting factors. Strip-mining can cause compaction, changes in soil texture, loss of soil structure and reduced water infiltration. In addition, steep-sided soil piles are prone to erosion .
The landscapes that emerge are devoid of supportive and nutritive capacity for biomass development. Several microbial processes such as nitrogen and carbon cycling, humidification and soil aggregation are practically non-functional posing scientific challenges in the restoration of rhizosphere productivity and fertility . The devalued land does not posses suitable surface soil to provide bedding layer for anchorage of plant and to support the biomass. Also the plant growth is not supported due to presence of toxic materials gradual increase in such landscapes due to intensive mining activity endangers not only the agro forestry productivity but also the aquatic eco-systems .
Impact of Noise and Vibrations from Mining
The mining activities produce enormous noise and vibration which establish a disturbance in the source. The blasting of hundred of tones of explosive is identified as prostrate noise in the mining area. In pit crushing system with mobile crusher and large capacity materials handling plants are being installed to facilitate speedy handling of large quantities . All these activities are major sources of noise & vibrations in and around the mining complexes.
The major implication of noise is the potential hearing loss of human ear. The noise also produces other health effects, influence to work performance and makes communications more difficult. The wildlife in the forests and other areas surrounding are also affected by noise. The wildlife is more sensitive to noise and vibration as compared to human beings.
Select all potentially noisy construction equipment and then consider the sound power level of the equipment and comply with the need to limit the noise in the mining area. If the operations have the potential to beak the specified noise limits or barrier then effective measures needs to be taken to ensure the sound power level is within the limits either by using different equipments which has less noise and while constructing the plant noise attenuation materials should be used to reduce the effective noise.