The primary use of coal is as a source of energy. Nations around the world use coal to produce electricity. Steel manufacturers also use coal to create a fuel called coke. Coal is formed from plants that were buried in the earth millions of years ago.
Coal is an important energy resource, but is not renewable. It is an exhaustible resource, which means that the supply is finite. Another significant problem with coal as a fuel is that it pollutes the atmosphere. Using coal produces large amounts of greenhouse gases. The fuel from coal is burned at power plants to heat water. The heated water creates steam that powers a large turbine. The turbine then produces electricity.
Experts divide coal into four main classifications. These are lignite, subbituminous, bituminous and anthracite. These four types of coal have various levels of energy content. Anthracite coal has the highest energy content and is therefore the most valuable of the four groups. Bituminous coal is the most common type of coal in the United States. Over half of the coal reserves in the country contain bituminous coal. Anthracite coal is much less common, with less that 2 percent of the coal reserves in the nation being of this variety.