Coal mining

Coal mining

Overview



The goal of coal mining is to obtain coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 from the ground. Coal is valued for its energy content, and since the 1880s has been widely used to generate electricity. Steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 and cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

 industries use coal as a fuel for extraction of iron from iron ore and for cement production. In the United States, United Kingdom, and South Africa, a coal mine and its structures are a "colliery".
Discussion
Ask a question about 'Coal mining'
Start a new discussion about 'Coal mining'
Answer questions from other users
Full Discussion Forum
 
Unanswered Questions
Recent Discussions
Encyclopedia



The goal of coal mining is to obtain coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 from the ground. Coal is valued for its energy content, and since the 1880s has been widely used to generate electricity. Steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 and cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

 industries use coal as a fuel for extraction of iron from iron ore and for cement production. In the United States, United Kingdom, and South Africa, a coal mine and its structures are a "colliery". In Australia, "colliery" generally refers to an underground coal mine.

History


The Industrial Revolution
Industrial Revolution
The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...

, which began in Britain in the 18th century, and later spread to continental Europe and North America, was based on the availability of coal to power steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

s. International trade expanded exponentially when coal-fed steam engines were built for the railways and steamships. The new mines that grew up in the 19th century depended on men and children to work long hours in often dangerous working conditions. There were many coalfields, but the oldest were in Newcastle
Newcastle upon Tyne
Newcastle upon Tyne is a city and metropolitan borough of Tyne and Wear, in North East England. Historically a part of Northumberland, it is situated on the north bank of the River Tyne...

 and Durham
Durham
Durham is a city in north east England. It is within the County Durham local government district, and is the county town of the larger ceremonial county...

, South Wales
South Wales
South Wales is an area of Wales bordered by England and the Bristol Channel to the east and south, and Mid Wales and West Wales to the north and west. The most densely populated region in the south-west of the United Kingdom, it is home to around 2.1 million people and includes the capital city of...

, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 and the Midlands, such as those at Coalbrookdale
Coalbrookdale
Coalbrookdale is a village in the Ironbridge Gorge in Shropshire, England, containing a settlement of great significance in the history of iron ore smelting. This is where iron ore was first smelted by Abraham Darby using easily mined "coking coal". The coal was drawn from drift mines in the sides...

.

The oldest continuously worked deep-mine in the United Kingdom is Tower Colliery
Tower Colliery
Tower Colliery is the oldest continuously working deep-coal mine in the United Kingdom, and possibly the world, and the last mine of its kind to remain in the South Wales Valleys...

 in South Wales valleys
South Wales Valleys
The South Wales Valleys are a number of industrialised valleys in South Wales, stretching from eastern Carmarthenshire in the west to western Monmouthshire in the east and from the Heads of the Valleys in the north to the lower-lying, pastoral country of the Vale of Glamorgan and the coastal plain...

 in the heart of the South Wales coalfield
South Wales Coalfield
The South Wales Coalfield is a large region of south Wales that is rich with coal deposits, especially the South Wales Valleys.-The coalfield area:...

. This colliery was developed in 1805, and its miners bought it out at the end of the 20th century, to prevent it from being closed. Tower Colliery was finally closed on 25 January 2008, although production continues at the Aberpergwm
Aberpergwm
Aberpergwm is the site of a colliery in the Vale of Neath near Glynneath in south Wales.The drift mine was reopened in 1996 after being closed by British Coal in 1985. It is owned and worked by Energybuild, a private company now wholly owned by Walter Energy of the USA...

 drift mine owned by Walter Energy
Walter Energy
Walter Energy, Inc. , with its U.S. headquarters in Birmingham, Alabama and its Canadian & U.K. headquarters in Vancouver, British Columbia, is the world’s leading, publicly traded “pure play” metallurgical coal producer for the global steel industry. The Company also produces steam coal and...

 of the USA nearby.

Coal was mined in America in the early 18th century, and commercial mining started around 1730 in Midlothian, Virginia
Midlothian, Virginia
Midlothian is an unincorporated community in Chesterfield County, Virginia, United States. Founded over 300 years ago as a coal mining village, it is now a suburban community located in the Southside of Richmond well beyond the city limits of Richmond in the Richmond–Petersburg region.It was named...

.

Coal-cutting machines were invented in the 1880s. Before this invention, coal was mined from underground with a pick
Pickaxe
A pickaxe or pick is a hand tool with a hard head attached perpendicular to the handle.Some people make the distinction that a pickaxe has a head with a pointed end and a flat end, and a pick has both ends pointed, or only one end; but most people use the words to mean the same thing.The head is...

 and shovel. By 1912 surface mining
Surface mining
Surface mining , is a type of mining in which soil and rock overlying the mineral deposit are removed...

 was conducted with steam shovels designed for coal mining.

Methods of extraction


The most economical method of coal extraction from coal seams depends on the depth and quality of the seams, and the geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

 and environmental factors. Coal mining processes are differentiated by whether they operate on the surface or underground. Many coals extracted from both surface and underground mines require washing in a coal preparation plant
Coal preparation plant
A coal preparation plant is a facility that washes coal of soil and rock, preparing it for transport to market. A CPP may also be called a "coal handling and preparation plant" , "prep plant," "tipple," or "wash plant"....

. Technical and economic feasibility are evaluated based on: regional geologic conditions; overburden
Overburden
Overburden is the material that lies above an area of economic or scientific interest in mining and archaeology; most commonly the rock, soil, and ecosystem that lies above a coal seam or ore body. It is also known as 'waste' or 'spoil'...

 characteristics; coal seam continuity, thickness, structure, quality, and depth; strength of materials above and below the seam for roof and floor conditions; topography (especially altitude and slope); climate; land ownership as it affects the availability of land for mining and access; surface drainage patterns; ground water conditions; availability of labor and materials; coal purchaser requirements in terms of tonnage, quality, and destination; and capital investment requirements.

Surface mining and deep underground mining are the two basic methods of mining. The choice of mining method depends primarily on depth of burial, density of the overburden and thickness of the coal seam. Seams relatively close to the surface, at depths less than approximately 180 ft (50 m), are usually surface mined.

Coal that occurs at depths of 180 to 300 ft (50 to 100 m) are usually deep mined, but in some cases surface mining techniques can be used. For example, some western U.S. coal that occur at depths in excess of 200 ft (60 m) are mined by the open pit methods, due to thickness of the seam 60–90 feet (20–30 m). Coals occurring below 300 ft (100 m) are usually deep mined. Although there are open pit mining operations working on coal seams up to 1000–1500 feet (300–450 m) below ground level, for instance Tagebau Hambach
Tagebau Hambach
The Tagebau Hambach is a large strip mine in Niederzier and Elsdorf, North-Rhine Westphalia, Germany. It is operated by RWE and used for mining lignite. Begun in 1978, the mine currently has a size of 33.89 km² and is planned to eventually have a size of 85 km². It is the deepest open pit mine...

 in Germany.

Modern surface mining



When coal seams are near the surface, it may be economical to extract the coal using open cut (also referred to as open cast, open pit, or strip) mining methods. Open cast coal mining recovers a greater proportion of the coal deposit than underground methods, as more of the coal seams in the strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

 may be exploited. Large Open Cast mines can cover an area of many square kilometers and use very large pieces of equipment. This equipment can include the following: Draglines which operate by removing the overburden, power shovels, large trucks in which transport overburden and coal, bucket wheel excavators, and conveyors. In this mining method, explosives are first used in order to break through the surface, or overburden, of the mining area. The overburden is then removed by draglines or by shovel and truck. Once the coal seam is exposed, it is drilled, fractured and thoroughly mined in strips. The coal is then loaded on to large trucks or conveyors for transport to either the coal preparation plant or directly to where it will be used.

Most open cast mines in the United States extract bituminous coal
Bituminous coal
Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen. It is of higher quality than lignite coal but of poorer quality than Anthracite...

. In Australia and South Africa open cast mining is used for both thermal and metallurgical coals. In New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

 open casting for steam coal and anthracite is practiced. Surface mining accounts for around 80 percent of production in Australia, while in the US it is used for about 67 percent of production. Globally, about 40 percent of coal production involves surface mining.

Area mining


Strip mining exposes the coal by removing the overburden (the earth above the coal seam(s)) in long cuts or strips. The soil from the first strip is deposited in an area outside the planned mining area. Spoil from subsequent cuts is deposited as fill in the previous cut after coal has been removed. Usually, the process is to drill
Drilling rig
A drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...

 the strip of overburden next to the previously mined strip.

The drill holes are filled with explosives and blasted. The overburden is then removed using large earthmoving equipment such as draglines, shovel and trucks, excavator
Excavator
Excavators are heavy construction equipment consisting of a boom, stick, bucket and cab on a rotating platform . The house sits atop an undercarriage with tracks or wheels. A cable-operated excavator uses winches and steel ropes to accomplish the movements. They are a natural progression from the...

 and trucks, or bucket-wheels
Bucket-wheel excavator
Bucket-wheel excavators are heavy equipment used in surface mining and mechanical engineering/civil engineering. The primary function of BWEs is to act as a continuous digging machine in large-scale open pit mining operations...

 and conveyors. This overburden is put into the previously mined (and now empty) strip. When all the overburden is removed, the
underlying coal seam will be exposed (a 'block' of coal). This block of coal may be drilled and blasted (if hard) or otherwise loaded onto trucks or conveyors for transport to the coal preparation (or wash) plant. Once this strip is empty of coal, the process is repeated with a new strip being created next to it. This method is most suitable for areas with flat terrain.

Equipment to be used depends on geologic conditions. For example, to remove overburden that is loose or unconsolidated, a bucket wheel excavator might be the most productive. The life of some area mines may be more than 50 years.

Contour mining


The contour mining method consists of removing overburden from the seam in a pattern following the contours along a ridge or around a hillside. This method is most commonly used in areas with rolling to steep terrain. It was once common to deposit the spoil on the downslope side of the bench thus created, but this method of spoil disposal consumed much additional land and created severe landslide and erosion problems. To alleviate these problems, a variety of methods were devised to use freshly cut overburden to refill mined-out areas. These haul-back or lateral movement methods generally consist of an initial cut with the spoil deposited downslope or at some other site and spoil from the second cut refilling the first. A ridge of undisturbed natural material 15 to 20 ft (5–6 m) wide is often intentionally left at the outer edge of the mined area. This barrier adds stability to the reclaimed slope by preventing spoil from slumping or sliding downhill.

The limitations on contour strip mining are both economic and technical. When the operation reaches a predetermined stripping ratio (tons of overburden/tons of coal), it is not profitable to continue. Depending on the equipment available, it may not be technically feasible to exceed a certain height of highwall. At this point, it is possible to produce more coal with the augering method in which spiral drills bore tunnels into a highwall laterally from the bench to extract coal without removing the overburden.

Mountaintop removal mining



Mountaintop coal mining is a surface mining practice involving removal of mountaintops to expose coal seams, and disposing of associated mining overburden in adjacent "valley fills." Valley fills occur in steep terrain where there are limited disposal alternatives.

Mountaintop removal
Mountaintop removal
Mountaintop removal mining is a form of surface mining that requires the removal of the summit or summit ridge of a mountain in order to permit easier access to the coal seams...

 combines area and contour strip mining methods. In areas with rolling or steep terrain with a coal seam occurring near the top of a ridge or hill, the entire top is removed in a series of parallel cuts. Overburden is
deposited in nearby valleys and hollows. This method usually leaves ridge and hill tops as flattened plateaus. The process is highly controversial for the drastic changes in topography, the practice of
creating head-of-hollow-fills, or filling in valleys with mining debris, and for covering streams and disrupting ecosystems.

Spoil is placed at the head of a narrow, steep-sided valley or hollow. In preparation for filling this area, vegetation and soil are removed and a rock drain constructed down the middle of the area to be filled, where a natural drainage course previously existed. When the fill is completed, this underdrain will form a continuous water runoff system from the upper end of the valley to the lower end of the fill. Typical head-of-hollow fills are graded and terraced to create permanently stable slopes.

Room and pillar mining


Room and pillar mining consists of coal deposits that are mined by cutting a network of rooms into the coal seam. Pillars of coal are left behind in order to keep up the roof. The pillars can make up to forty percent of the total coal in the seam, however where there was space to leave head and floor coal there is evidence from recent open cast excavations that 18th century operators used a variety of room and pillar techniques to remove 92 percent of the in situ coal. However, this can be extracted at a later stage (see Retreat Mining).

Underground mining




Most coal seams are too deep underground for opencast mining and require underground mining, a method that currently accounts for about 60 percent of world coal production. In deep mining, the room and pillar or bord and pillar
Room and pillar
Room and pillar is a mining system in which the mined material is extracted across a horizontal plane while leaving "pillars" of untouched material to support the roof overburden leaving open areas or "rooms" underground...

 method progresses along the seam, while pillars and timber are left standing to support the mine roof. Once room and pillar mines have been developed to a stopping point (limited by geology, ventilation, or economics), a supplementary version of room and pillar mining, termed second mining or retreat mining
Retreat mining
Retreat mining is a term used to reference the final phase of an underground mining technique known as room and pillar mining. This involves excavating a room or chamber while leaving behind pillars of material for support. This excavation is carried out in a pattern advancing away from the...

, is commonly started. Miners remove the coal in the pillars, thereby recovering as much coal from the coal seam as possible. A work area involved in pillar extraction is called a pillar section.

Modern pillar sections use remote-controlled equipment, including large hydraulic mobile roof-supports, which can prevent cave-ins until the miners and their equipment have left a work area. The mobile roof supports are similar to a large dining-room table, but with hydraulic jacks for legs. After the large pillars of coal have been mined away, the mobile roof support's legs shorten and it is withdrawn to a safe area. The mine roof typically collapses once the mobile roof supports leave an area.

There are five principal methods of underground mining:
  • Longwall mining
    Longwall mining
    Longwall mining is a form of underground coal mining where a long wall of coal is mined in a single slice . The longwall panel is typically 3–4 km long and 250–400 m wide....

     accounts for about 50 percent of underground production. The longwall shearer has a face of 1000 feet (304.8 m) or more. It is a sophisticated machine with a rotating drum that moves mechanically back and forth across a wide coal seam. The loosened coal falls on to a pan line that takes the coal to the conveyor belt for removal from the work area. Longwall systems have their own hydraulic roof supports which advance with the machine as mining progresses. As the longwall mining equipment moves forward, overlying rock that is no longer supported by coal is allowed to fall behind the operation in a controlled manner. The supports make possible high levels of production and safety. Sensors detect how much coal remains in the seam while robotic controls enhance efficiency. Longwall systems allow a 60-to-100 percent coal recovery rate when surrounding geology allows their use. Once the coal is removed, usually 75 percent of the section, the roof is allowed to collapse in a safe manner.

  • Continuous mining utilizes a Continuous Miner Machine with a large rotating steel drum equipped with tungsten carbide teeth that scrape coal from the seam. Operating in a “room and pillar” (also known as “bord and pillar”) system—where the mine is divided into a series of 20-to-30 foot (5–10 m) “rooms” or work areas cut into the coalbed—it can mine as much as five tons of coal a minute, more than a non-mechanised mine of the 1920s would produce in an entire day. Continuous miners account for about 45 percent of underground coal production. Conveyors
    Conveyor system
    A conveyor system is a common piece of mechanical handling equipment that moves materials from one location to another. Conveyors are especially useful in applications involving the transportation of heavy or bulky materials...

     transport the removed coal from the seam. Remote-controlled continuous miners are used to work in a variety of difficult seams and conditions, and robotic versions controlled by computers are becoming increasingly common. Continuous mining is truly a misnomer, as room and pillar coal mining is very cyclical. In the US, one can generally cut 20 ft or 6 meters (or a bit more with MSHA
    Mine Safety and Health Administration
    The Mine Safety and Health Administration is an agency of the United States Department of Labor which administers the provisions of the Federal Mine Safety and Health Act of 1977 to enforce compliance with mandatory safety and health standards as a means to eliminate fatal accidents, to reduce...

     permission) (12 meters or roughly 40ft in South Africa before the Continuous Miner goes out and the roof is supported by the Roof Bolter), after which, the face has to be serviced, before it can be advanced again. During servicing, the "continuous" miner moves to another face. Some continuous miners can bolt and dust the face (two major components of servicing) while cutting coal, while a trained crew may be able to advance ventilation, to truly earn the "continuous" label. However, very few mines are able to achieve it. Most continuous mining machines in use in the US lack the ability to bolt and dust. This may partly be because incorporation of bolting makes the machines wider, and therefore, less maneuverable.
  • Blast mining or conventional mining, is an older practice that uses explosives such as dynamite
    Dynamite
    Dynamite is an explosive material based on nitroglycerin, initially using diatomaceous earth , or another absorbent substance such as powdered shells, clay, sawdust, or wood pulp. Dynamites using organic materials such as sawdust are less stable and such use has been generally discontinued...

     to break up the coal seam, after which the coal is gathered and loaded on to shuttle cars or conveyors for removal to a central loading area. This process consists of a series of operations that begins with “cutting” the coalbed so it will break easily when blasted with explosives. This type of mining accounts for less than 5 percent of total underground production in the US today.
  • Shortwall mining, a method currently accounting for less than 1 percent of deep coal production, involves the use of a continuous mining machine with movable roof supports, similar to longwall. The continuous miner shears coal panels 150 to 200 feet (40 to 60 m) wide and more than a half-mile (1 km) long, having regard to factors such as geological strata.
  • Retreat mining
    Retreat mining
    Retreat mining is a term used to reference the final phase of an underground mining technique known as room and pillar mining. This involves excavating a room or chamber while leaving behind pillars of material for support. This excavation is carried out in a pattern advancing away from the...

     is a method in which the pillars or coal ribs used to hold up the mine roof are extracted; allowing the mine roof to collapse as the mining works back towards the entrance. This is one of the most dangerous forms of mining, owing to imperfect predictability of when the ceiling will collapse and possibly crush or trap workers in the mine.

Production



Coal is mined commercially in over 50 countries. Over 7,036 Mt/yr of hard coal is currently produced, a substantial increase over the past 25 years. In 2006, the world production of brown coal and lignite
Lignite
Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...

 was slightly over 1,000 Mt, with Germany the world’s largest brown coal producer at 194.4 Mt, and China second at 100.6 Mt.

Coal production has grown fastest in Asia, while Europe has declined. The top coal mining nations (figures in brackets are 2009 estimate of total coal production in millions of tons) are:
  • China
    People's Republic of China
    China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

     (3,050 Mt)
  • US
    United States
    The United States of America is a federal constitutional republic comprising fifty states and a federal district...

     (973 Mt)
  • India
    India
    India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

     (557 Mt)
  • Australia
    Australia
    Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

     (409 Mt)
  • South Africa
    South Africa
    The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

     (250 Mt)
  • Russia
    Russia
    Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

     (298 Mt)
  • Indonesia
    Indonesia
    Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

     (252 Mt)
  • Poland
    Poland
    Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

     (135 Mt)
  • Kazakhstan
    Kazakhstan
    Kazakhstan , officially the Republic of Kazakhstan, is a transcontinental country in Central Asia and Eastern Europe. Ranked as the ninth largest country in the world, it is also the world's largest landlocked country; its territory of is greater than Western Europe...

     (101 Mt)
  • Colombia
    Colombia
    Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

     (72 Mt)


Most coal production is used in the country of origin, with around 16 percent of hard coal production being exported.

Global coal production is expected to reach 7,000 Mt/yr in 2030 (Update required, world coal production is already past 7,000 Mt/yr and by 2030 will probably be closer to 13,000 Mt/yr), with China accounting for most of this increase. Steam coal production is projected to reach around 5,200 Mt/yr; coking coal 620 Mt/yr; and brown coal 1,200 Mt/yr.

Coal reserves are available in almost every country worldwide, with recoverable reserves in around 70 countries. At current production levels, proven coal reserves are estimated to last 147
years. However, production levels are by no means level, and are in fact increasing and some estimates are that peak coal
Peak coal
Peak coal is the point in time at which the maximum global coal production rate is reached, after which, according to the theory, the rate of production will enter to a terminal decline. Coal is a fossil fuel formed from plant matter over the course of millions of years...

 could arrive in many countries such as China and America by around 2030. Coal reserves are usually stated as either (1) "Resources" ("measured" + "indicated" + "inferred" = "resources", and then, a smaller number, often only 10-20% of "resources," (2) "Run of Mine" (ROM
Rom
ROM, Rom, or rom is an abbreviation and name that may refer to:-In computers and mathematics:* Read-only memory, a type of storage media which is used in computers and other electronic devices....

) reserves, and finally (3) "marketable reserves", which may be only 60% of ROM reserves. The standards for reserves are set by stock exchanges, in consultation with industry associations. For example in ASEAN countries reserves standards follow the Australasian Joint Ore Reserves Committee (JORC) Code used by the Australian Securities Exchange (ASX
ASX
ASX may refer to:* Australian Securities Exchange, the primary stock exchange of Australia* Advanced Stream Redirector, a computer file format listing Windows Media files * Armstrong Siddeley ASX, a British experimental turbojet* John F...

).

Modern mining


Technological advancements have made coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 mining today more productive than it has ever been. To keep up with technology and to extract coal as efficiently as possible modern mining personnel must be highly skilled and well trained in the use of complex, state-of-the-art instruments and equipment. Many jobs require four-year university degrees. Computer knowledge has also become greatly valued within the industry as most of the machines and safety monitors are computerized.

The use of sophisticated sensing equipment to monitor air quality is common and has replaced the use of small animals such as canaries, often referred to as "miner's canaries".

In the United States, the increase in technology has significantly decreased the mining workforce from 335,000 coal miners working at 7,200 mines fifty years ago to 104,824 miners working in fewer than 2,000 mines today.

Dangers to miners



Historically, coal mining has been a very dangerous activity and the list of historical coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 mining disasters is a long one. In the US alone, more than 100,000 coal miners were killed in accidents over the past century, with more than 3,200 dying in 1907 alone. Open cut hazards are principally mine wall failures and vehicle collisions; underground mining hazards include suffocation, gas poisoning, roof collapse and gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

 explosions.

Firedamp
Firedamp
Firedamp is a flammable gas found in coal mines. It is the name given to a number of flammable gases, especially methane. It is particularly commonly found in areas where the coal is bituminous...

 explosions can trigger the much more dangerous coal dust
Coal dust
Coal dust is a fine powdered form of coal, which is created by the crushing, grinding, or pulverizing of coal. Because of the brittle nature of coal, coal dust can be created during mining, transportation, or by mechanically handling coal.-Explosions:...

 explosions, which can engulf an entire pit. Most of these risks can be greatly reduced in modern mines, and multiple fatality incidents are now rare in some parts of the developed world. Modern mining in the US results in approximately 30 deaths per year due to mine accidents.

However, in lesser developed countries and some developing countries, many miners continue to die annually, either through direct accidents in coal mines or through adverse health consequences from working under poor conditions. China
Coal power in China
The People's Republic of China is the largest consumer of coal in the world, and is about to become the largest user of coal-derived electricity, generating 1.95 trillion kilowatt-hours per year, or 68.7% of its electricity from coal as of 2006...

, in particular, has the highest number of coal mining related deaths in the world, with official statistics claiming that 6,027 deaths occurred in 2004. To compare, 28 deaths were reported in the US in the same year. Coal production in China is twice that in the US, while the number of coal miners is around 50 times that of the US, making deaths in coal mines in China 4 times as common per worker (108 times as common per unit output) as in the US.

In 2006, fatal work injuries among miners in the US doubled from the previous year, totaling 47. These figures can in part be attributed to the Sago Mine disaster
Sago Mine disaster
The Sago Mine disaster was a coal mine explosion on January 2, 2006, in the Sago Mine in Sago, in Upshur County, West Virginia, USA, near the county seat of Buckhannon. The blast and collapse trapped 13 miners for nearly two days; one miner survived...

 of January 2006. The 2007 mine accident in Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

's Crandall Canyon Mine
Crandall Canyon Mine
The Crandall Canyon Mine, formerly Genwal Mine, was an underground bituminous coal mine in northwestern Emery County, Utah.The mine made headline news when six miners were trapped by a collapse in August 2007. Ten days later, three rescue workers were killed by a subsequent collapse...

, where nine miners were killed and six entombed, speaks to the increase in occupational risks faced by US miners. More recently, the Upper Big Branch Mine disaster
Upper Big Branch Mine disaster
The Upper Big Branch Mine disaster occurred on April 5, 2010 about underground in Raleigh County, West Virginia at Massey Energy's Upper Big Branch coal mine located in Montcoal . Twenty-nine out of thirty-one miners at the site were killed. The explosion occurred at 3:27 pm...

 in West Virginia killed 29 miners in April 2010.

Chronic lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

 diseases, such as pneumoconiosis
Pneumoconiosis
Pneumoconiosis is an occupational lung disease and a restrictive lung disease caused by the inhalation of dust, often in mines.-Types:Depending upon the type of dust, the disease is given different names:...

 (black lung) were once common in miners, leading to reduced life expectancy
Life expectancy
Life expectancy is the expected number of years of life remaining at a given age. It is denoted by ex, which means the average number of subsequent years of life for someone now aged x, according to a particular mortality experience...

. In some mining countries black lung is still common, with 4,000 new cases of black lung every year in the US (4 percent of workers annually) and 10,000 new cases every year in China (0.2 percent of workers). Rates may be higher than reported in some regions.

Build-ups of a hazardous gas are known as damps, possibly from the German word "Dampf" which means steam or vapor:
  • Black damp: a mixture of carbon dioxide
    Carbon dioxide
    Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

     and nitrogen
    Nitrogen
    Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

     in a mine can cause suffocation, and is formed as a result of corrosion in enclosed spaces so removing oxygen
    Oxygen
    Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

     from the atmosphere.
  • After damp
    Afterdamp
    Afterdamp is the toxic mixture of gases left in a mine following an explosion caused by firedamp, which itself can initiate a much larger explosion of coal dust. It consists of carbon dioxide, carbon monoxide and nitrogen. Hydrogen sulfide, another highly toxic gas, may also be present...

    : similar to black damp, after damp consists of carbon monoxide
    Carbon monoxide
    Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

    , carbon dioxide
    Carbon dioxide
    Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

     and nitrogen and forms after a mine explosion.
  • Fire damp
    Firedamp
    Firedamp is a flammable gas found in coal mines. It is the name given to a number of flammable gases, especially methane. It is particularly commonly found in areas where the coal is bituminous...

    : consists of mostly methane
    Methane
    Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

    , a highly flammable gas that explodes between 5% and 15% - at 25% it causes asphyxiation.
  • Stink damp
    Hydrogen sulfide
    Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

    : so named for the rotten egg smell of the hydrogen sulphide gas, stink damp can explode and is also very toxic.
  • White damp
    Carbon monoxide
    Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

    : air containing carbon monoxide which is toxic, even at low concentrations

Safer times in modern mining


Improvements in mining methods (e.g. longwall mining), hazardous gas monitoring (such as safety-lamps or more modern electronic gas monitors), gas drainage, electrical equipment
Electrical Equipment in Hazardous Areas
In electrical engineering, a hazardous location is defined as a place where concentrations of flammable gases, vapors, or dusts occur. Electrical equipment that must be installed in such locations is especially designed and tested to ensure it does not initiate an explosion, due to arcing contacts...

, and ventilation have reduced many of the risks of rock falls, explosions, and unhealthy air quality. Statistical analyses performed by the US Department of Labor’s Mine Safety and Health Administration
Mine Safety and Health Administration
The Mine Safety and Health Administration is an agency of the United States Department of Labor which administers the provisions of the Federal Mine Safety and Health Act of 1977 to enforce compliance with mandatory safety and health standards as a means to eliminate fatal accidents, to reduce...

 (MSHA) show that between 1990 and 2004, the industry cut the rate of injuries by more than half and fatalities by two-thirds. However, according to the Bureau of Labor Statistics
Bureau of Labor Statistics
The Bureau of Labor Statistics is a unit of the United States Department of Labor. It is the principal fact-finding agency for the U.S. government in the broad field of labor economics and statistics. The BLS is a governmental statistical agency that collects, processes, analyzes, and...

, mining remains the second most dangerous occupation in America.

New braces called Atlas Cribs contain a mix of hardwoods and a main lateral element that make these braces stronger than other braces used in the past. The new cribbing system takes up 41 percent less area than existing ones and may be up to 50 percent more efficient in terms of airflow.

Environmental impacts



Coal mining can result in a number of adverse effects on the environment. 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, This often results in a scarred landscape with no scenic value. Rehabilitation or reclamation mitigates some of these concerns and is required by Federal Law, specifically the Surface Mining Control and Reclamation Act of 1977
Surface Mining Control and Reclamation Act of 1977
The Surface Mining Control and Reclamation Act of 1977 is the primary federal law that regulates the environmental effects of coal mining in the United States....

.

Mine tailing dumps produce acid mine drainage
Acid mine drainage
Acid mine drainage , or acid rock drainage , refers to the outflow of acidic water from metal mines or coal mines. However, other areas where the earth has been disturbed may also contribute acid rock drainage to the environment...

 which can seep into waterways and aquifers, with consequences on ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

 and human health. If underground mine tunnels collapse, this can cause subsidence of land surfaces. During actual mining operations, methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

, a known greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...

, may be released into the air. And by the movement, storage, and redistribution of soil, the community of microorganisms and nutrient cycling processes can be disrupted.

Coal mining by country


Top 10 hard and brown coal producers in 2010 (2009) were (Mt): China 3,162 (2,971), United States 997 (985), India
Energy in India
Energy in India describes energy and electricity production, consumption and import in India. Energy policy of India describes the politics of India related to energy. Electricity sector in India is the main article of electricity in India....

  571 (561), Australia
Energy in Australia
Energy in Australia describes energy and electricity production, consumption and export in Australia. Energy policy of Australia describes the politics of Australia related to energy....

 420 (399), Indonesia
Energy in Indonesia
Energy in Indonesia describes energy and electricity production, consumption and import in Indonesia. In 2009 Indonesia produced oil, coal, natural gas and palm oil, utilized also as energy raw material in 2010. Renewable energy potential in Indonesia is high: solar, wind, hydro and geothermal...

 336 (301), Russia 324 (297), South Africa
Energy in South Africa
Energy in South Africa describes energy and electricity production, consumption and export in South Africa.South Africa was 6. top hard coal producer in 2009. Hard coal production was 1,620 TWh in 2009 and total energy production 1,995 TWh in 2008. The environmenatal concerns of old abandoned coal...

 255 (247), Kazakhstan
Energy in Kazakhstan
Energy in Kazakhstan describes energy and electricity production, consumption and import in Kazakhstan. Energy policy of Kazakhstan describes the politics of Kazakhstan related to energy.Kazakhstan is net energy exporter...

 111 (101), Poland
Energy in Poland
Energy in Poland describes energy and electricity production, consumption and import in Poland.In 2009, Poland was world's 9th largest hard coal producer...

 134 (135) and Colombia 74 (73).

Australia



Coal is mined in every state of Australia as well as the Northern Territory. It is mostly used to generate electricity, and 75 percent of annual coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 production is exported, mostly to eastern Asia. Coal provides about 85 percent of Australia's electricity production. In 2007, 428 million short tons of coal was mined in Australia.

India



Coal accounts for approximately 60 percent of all commercial electricity generation.

China


The People's Republic of China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

 is by far the largest producer of coal in the world, producing over 2.8 billion tons of coal in 2007, or approximately 39.8 percent of all coal produced in the world during that year. For comparison, the second largest producer, the United States, produced more than 1.1 billion tons in 2007. An estimated 5 million people work in China's coal-mining industry. As many as 20,000 miners die in accidents each year. Most Chinese mines are deep underground and do not produce the surface disruption typical of strip mines. Although there is some evidence of reclamation
Mine reclamation
Mine reclamation is the process of creating useful landscapes that meet a variety of goals, typically creating productive ecosystems from mined land...

 of mined land for use as parks, China does not require extensive reclamation and is creating significant acreages of abandoned mined land which is unsuitable for agriculture or other human uses, and inhospitable to indigenous wildlife. Chinese underground mines often experience severe surface subsidence
Subsidence
Subsidence is the motion of a surface as it shifts downward relative to a datum such as sea-level. The opposite of subsidence is uplift, which results in an increase in elevation...

 (6–12 meters), negatively impacting farmland because it no longer drains well. China uses some subsidence areas for aquaculture
Aquaculture in China
China, with one-fifth of the world's population, accounts for two-thirds of the worlds reported aquaculture production.Aquaculture is the farming of fish and other aquatic life in enclosures, such as ponds, lakes and tanks, or cages in rivers and coastal waters...

 ponds but has more than they need for that purpose. Reclamation of subsided ground is a significant problem in China. Because most Chinese coal is for domestic consumption and is burned with little or no air pollution
Air pollution
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....

 control equipment, it contributes greatly to visible smoke and severe air pollution in industrial areas using coal for fuel.

Colombia



Some of the world's largest coal reserves are located in South America, and an opencast mine at Cerrejón
Cerrejón
Cerrejón is a coal mine located in the Guajira department in the north of Colombia. It is the largest mining operation in Colombia and among the largest open-pit coal mines in the world. The legal entity managing the Cerrejón operation is known as Carbones del Cerrejón Ltd...

 in Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

 is one of the world's largest open pit mines. Output of the mine in 2004 was 24.9 million tons (compared to total global hard coal production of 4,600 million tons). Cerrejón contributed about half of Colombia's coal exports of 52 million tons that year, with Colombia ranked sixth among major coal exporting nations. The company planned to expand production to 32 million tons by 2008. The company has its own 150 km standard-gauge railroad, connecting the mine to its coal-loading terminal at Puerto Bolívar on the Caribbean coast. There are two 120-car unit trains, each carrying 12,000 tons of coal per trip. The round-trip time for each train, including loading and unloading, is about 12 hours. The coal facilities at the port are capable of loading 4,800 tons per hour on to vessels of up to 175,000 tons of dead weight. The mine, railroad and port
operate 24 hours per day. Cerrejón directly employs 4,600 workers, with a further 3,800 employed by contractors. The reserves at Cerrejón are low-sulfur, low-ash, bituminous coal. The coal is mostly used for electric power generation, with some also used in steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 manufacture. The surface mineable reserves for the current contract are 330 million tons. However, total proven reserves to a depth of 300 metres are 3,000 million tons.

South Africa



South Africa is one of the ten largest coal producing and the fourth largest coal exporting country in the world.

United States


The American share of world coal production remained steady at about 20 percent from 1980 to 2005, at about 1 billion short tons per year. In 2008 then-President
President of the United States
The President of the United States of America is the head of state and head of government of the United States. The president leads the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces....

 George W. Bush
George W. Bush
George Walker Bush is an American politician who served as the 43rd President of the United States, from 2001 to 2009. Before that, he was the 46th Governor of Texas, having served from 1995 to 2000....

 stated that coal was the most reliable source of electricity. However, in 2011 President Barack Obama
Barack Obama
Barack Hussein Obama II is the 44th and current President of the United States. He is the first African American to hold the office. Obama previously served as a United States Senator from Illinois, from January 2005 until he resigned following his victory in the 2008 presidential election.Born in...

 said that the US should rely more on "clean" sources of energy that emit lower or no carbon dioxide
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...

 pollution.

Ukraine


More than 90 percent of Ukraine’s coal production comes from the Donets Basin
Donets Basin
Donbas or Donbass , full rarely-used name Donets Basin , is a historical, economic and cultural region of eastern Ukraine. Originally a coal mining area, it has become a heavily industrialised territory suffering from urban decay and industrial pollution.-Geography:Donbas covers three...

. The country's coal industry employs about 500,000 people. Ukrainian coal mines are among the most dangerous in the world, and accidents are common. Furthermore, the country is plagued with extremely dangerous illegal mines.

See also


  • Acid mine drainage
    Acid mine drainage
    Acid mine drainage , or acid rock drainage , refers to the outflow of acidic water from metal mines or coal mines. However, other areas where the earth has been disturbed may also contribute acid rock drainage to the environment...

  • Black lung disease
  • George Bretz (photographer)
    George Bretz (photographer)
    George M. Bretz was an American photographer who is best known for his photographs of the Northeastern Pennsylvania Coal Region and its coal miners....

    , famous 19th century photographs of coal mines & miners.
  • Child labour
  • Coal Measures
    Coal Measures
    The Coal Measures is a lithostratigraphical term for the coal-bearing part of the Upper Carboniferous System. It represents the remains of fluvio-deltaic sediment, and consists mainly of clastic rocks interstratified with the beds of coal...

  • Coal preparation plant
    Coal preparation plant
    A coal preparation plant is a facility that washes coal of soil and rock, preparing it for transport to market. A CPP may also be called a "coal handling and preparation plant" , "prep plant," "tipple," or "wash plant"....

  • Coal slurry impoundment
  • Coal train
  • Coal-mining region
    Coal-mining region
    Coal mining regions are significant resource extraction industries in many parts of the world. They provide a large amount of the fossil fuel energy in the world economy....

  • Hurrying
    Hurrying
    A hurrier, also sometimes called a coal drawer or coal thruster, was a child or woman employed by a collier to transport the coal that they had mined. Women would normally get the children to help them because of the difficulty of carrying the coal...

  • List of books about coal mining
  • Mine fire
    Mine fire
    A coal seam fire or mine fire is the underground smouldering of a coal deposit, often in a coal mine. Such fires have economic, social and ecological impacts...

  • Mining accident
    Mining accident
    A mining accident is an accident that occurs during the process of mining minerals.Thousands of miners die from mining accidents each year, especially in the processes of coal mining and hard rock mining...

  • Peak coal
    Peak coal
    Peak coal is the point in time at which the maximum global coal production rate is reached, after which, according to the theory, the rate of production will enter to a terminal decline. Coal is a fossil fuel formed from plant matter over the course of millions of years...

  • Problems in coal mining
    Problems in coal mining
    Coal mining cannot be done everywhere with coal, due to certain geological restrictions.-Faulting:If the coal seam reaches a fault, the seam may be significantly displaced, depending on the type of fault and its offset. Machinery trying to mine the coal may not be able to reach the displaced seam,...

  • World Coal Institute
    World Coal Institute
    The World Coal Institute changed its name to World Coal Association in November 2010.The World Coal Association is a non-profit, non-governmental association, funded by coal enterprises and stakeholders....


Further reading


  • Daniel Burns. The modern practice of coal mining (1907)
  • Chirons, Nicholas P. Coal Age Handbook of Coal Surface Mining (ISBN 0-07-011458-7)
  • Hamilton, Michael S. Mining Environmental Policy: Comparing Indonesia and the USA (Burlington, VT: Ashgate, 2005). (ISBN 0-7546-4493-6).
  • Hayes, Geoffrey. Coal Mining (2004), 32 pp
  • Hughes. Herbert W, A Text-Book of Mining: For the use of colliery managers and others (London, many editions 1892-1917), the standard British textbook for its era.
  • Charles V. Nielsen and George F. Richardson. 1982 Keystone Coal Industry Manual (1982)
  • Saleem H. Ali. "Minding our Minerals, 2006."
  • A.K. Srivastava. Coal Mining Industry in India (1998) (ISBN 81-7100-076-2)
  • James Tonge. The principles and practice of coal mining (1906)


External links