Coal is a hard rock which can be burned as a solid fossil fuel. It is mostly carbon but also contains hydrogen, sulphur, oxygen and nitrogen. It is a sedimentary rock formed from peat, by the pressure of rocks laid down later on top. The harder forms of coal, such as anthracite, are metamorphic rocks, which means they were changed by very high temperature and pressure.
Peat, and therefore coal, is formed from the remains of plants which lived millions of years ago in tropical wetlands, such as those of the late Carboniferous period (the Pennsylvanian). Also wood heated in an airless space can make charcoal, which is like coal.
Coal can be burned for energy or heat. About two-thirds of the coal mined today is burned in power stations to make electricity. But few new coal-fired (coal burning) power stations are being built. This is because burning coal gives off pollution, like dirty air, and a lot of carbon dioxide which makes global warming. Natural gas power stations can start up more quickly than coal. Also other ways of making electricity like hydroelectricity, wind power and solar power are often cheaper nowadays. New coal power plants are still popular in some parts of the world, such as China.
Coal can be roasted (heated very hot in a place where there is no oxygen) to produce coke. Coke can be used in smelting to reduce metals from their ores. Coalis anonrenewable energy source.and coal is an important fuel and petroleum also an important fuel
Coal was the most important fuel of the Industrial Revolution. Coal was an important part of rail freight in the UK in the 20th century, forming the greater part of several companies' freight volume. In the UK early in the 21st century most coal fired power stations were closed to reduce greenhouse gas emissions.
Different kinds of coal and how they formEdit
Under suitable conditions, plant material is transformed step by step into
- Peat is not yet coal.
- Lignite (brown coal) is the dirtiest coal, is about 60%-70% carbon, and is used as fuel for electric power generation. Jet is a compact form of lignite that is sometimes polished and has long been used as an ornamental stone.
- Sub-bituminous coal is used as fuel for steam-electric power generation. Also, it is a source of light aromatic hydrocarbons for the chemical synthesis industry.
- Bituminous coal is a dense rock, black but sometimes dark brown. It is a relatively soft coal that breaks and burns readily and quickly. It used as fuel in power stations, and for heat and power applications in manufacturing; and to make coke.
- Steam coal was once widely used as a fuel for steam locomotives. In this specialized use it is sometimes known as sea-coal in the U.S. Small steam coal (dry small steam nuts or DSSN) was used as a fuel for domestic water heating.
- Anthracite is a harder, glossy, black coal. It is longer burning, and used mainly for residential and commercial space heating.
- Graphite is no longer coal: it is difficult to burn and is not so commonly used as fuel: it is mostly used in pencils and, when powdered, as a lubricant.
Diamond is commonly believed to be the highest grade, but this is not true. Diamond is carbon but is not formed from coal.
Deaths and Illness from PollutionEdit
Because of coal every year over 800,000 people die early and millions of people get ill. Coal miners often get black lung disease from exposure to coal dust.
Coal, when burnt, gives off almost a third more carbon dioxide per unit of energy than oil, and 80% more than natural gas. Almost half of the carbon dioxide from people is because of burning coal so it is the biggest single cause of global warming. Coal contributes to acid rain and smog, especially when burned without scrubbers. Burning coal releases toxic chemicals, which contribute to diseases such as cancer and asthma. Coal mining, especially mountaintop removal mining, can damage large areas of land and destroy natural habitats. Higher grades of coal burn more cleanly than lower grades, although they still pollute more than other fuels.
Peak coal means the year in which most coal is mined or burned. Many countries have already passed their peak coal years, for example Germany in 1985 and the United States in 2008. Now those countries are mining and burning less coal. But China still mines a lot of coal and is helping a few countries, like Pakistan, mine more coal and build more coal-fired power stations. So the peak coal year for the world may have passed but economists are not sure yet.
- Coal provides about a quarter of the world's energy needs
- Coal-fired power stations produce 37% of the world's electricity.
- Almost 70% of world steel production depends on burning coal.
Since 1983 the world's top coal producer has been China, which produces about 4 billions tonnes each year, followed in order by India, United States, Australia, Indonesia and Russia with less than a billion tonnes each. The largest exporter by far is Australia and the largest importers are China, India and Japan.
- Funk and Wagnalls, quoted in "sea-coal". Oxford English Dictionary. 2nd ed, Oxford University Press. 1989.