Coal

Coal is a combustible black or brownish-black sedimentary rock composed mostly of carbon and hydrocarbons.

Coal is a nonrenewable energy source because it takes millions of years to create. The energy in coal comes from the energy stored by plants that lived hundreds of millions of years ago, when the earth was partly covered with swampy forests. For millions of years, a layer of dead plants at the bottom of the swamps was covered by layers of water and dirt, trapping the energy of the dead plants. The heat and pressure from the top layers helped the plant remains turn into what we today call coal.

Coal has to be mined, or dug out of the ground. In surface mining, giant machines remove the top-soil and layers of rock to expose large beds of coal. Once the mining is finished, the dirt and rock are returned to the pit, the topsoil is replaced, and the area is replanted. Underground mining, sometimes called deep mining, is used when the coal is buried several hundred feet below the surface. To remove coal in these underground mines, miners ride elevators down deep mine shafts where they run machines that dig out the coal.

Coal is then transported to where it is needed, but the cost of shipping it can be more than the cost of mining it.

Coal is first crushed to a fine dust, and then burned to produce energy.

ADVANTAGES

Very large amounts of electricity can be generated in one place using coal, fairly cheaply. The price of coal has stayed fairly stable (whereas the price of oil has risen sharply), meaning it is still economical to use. There is still quite a lot of it left in the ground, so it won't run out quite as fast as oil will. Technology today is meaning that coal is burned far more cleanly than it was in the past.

DISADVANTAGES

Burning coal produces even more carbon dioxide than burning oil or gas, thus adding to the greenhouse effect, and it produces sulphur dioxide, an acidic gas that contributes to the formation of acid rain. (Acid rain contaminates drinking water, damages plants and water life, and even eats away buildings).

Mining coal can be difficult and dangerous. Strip mining destroys large areas of the landscape. Coal-fired power stations need huge amounts of fuel, which means train-loads of coal almost constantly. In order to cope with changing demands for power, the station needs reserves. This means covering a large area of countryside next to the power station with piles of coal.

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