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Most people know the general facts about coal. It is commonly known that it takes a long time for coal to form and it comes from fossils. Other common knowledge is that it is a source of energy, the U.S. can mine it on American soil, and we don’t have to import it. There is a lot more to coal than that. Coal is non-renewable, that means that once it is used, it is gone. It takes millions of years for the energy that plants store to become coal. This is how coal is formed:

Swampy plants grow abundantly and then die The dead plants are trapped under layers of dirt and water The energy from the plants is also trapped Heat and pressure with layers of earth turn the plants into coal

The process of removing coal from the ground is referred to as mining. Coal mining is done one of two ways. One way is surface mining and the other is underground mining. Surface mining is the most common. For layers of coal that are less than 200 feet underground, surface mining is the best choice. It is less costly than underground mining. Surface mining is the removal of the top layer of dirt and rocks to reach the coal layer. It is done with large machinery. The coal beds are mined and then the dirt and rock are replaced. Topsoil is returned and the area can be replanted. When mining is done on surface mines the area can be used for crops, wildlife habitats, recreation, or to build on. Two-thirds of the coal that is used in the U.S. comes from surface mines. Some coal beds are deeper than 200 feet; these coal beds are mined using underground mining. This method is also known as deep mining. These mines can be as deep as 1,000 feet. Miners use elevators to get to the coal bed. The coal is removed with machines from the mineshafts that are dug into the ground. When mining is done, the land can be reclaimed. The coal that is removed from mines is divided into four main types also know as ranks. The types of coal are lignite, subbituminous, bituminous, and anthracite. The amount and types of carbon that the coal contains as well as the energy that it is capable of producing are used to classify coal. These differences are caused by differences in pressure and heat acting on the plants as they sunk deeper. Usually a higher-ranking coal contains more heat producing energy. LIGNITE COAL Lignite is the lowest rank of coal with the lowest energy content.  Lignite coal deposits are young beds that were not exposed to extreme heat and pressure.  The high moisture content makes lignite coal crumble. In the United States, about seven percent of U.S. coal is coal that comes from approximately 20 lignite mines in the United States. Texas and North Dakota are the states that have the most lignite coal. Power plants that generate electricity use Lignite coal.

SUBBITUMINOUS COAL

Subbituminous coal has a higher heating value than lignite coal. This coal typically contains 35-45 percent carbon (lignite coal contains 25-35 percent) and in the U.S. it is at least 100 million years old. Subbituminous coal makes up about 44 percent of the coal produced in the U.S. The state that is the leading source of subbituminous coal is Wyoming. BITUMINOUS COAL Bituminous coal contains 45-86 percent carbon, and has two to three times the heating value of lignite. This type of coal is formed under high heat and pressure. Bituminous coal in the United States is 100 to 300 million years old. The most abundant type of coal found in the United States is bituminous coal and it makes up about half of coal that is produced in the U.S. It is an important fuel and raw material for the steel and iron industries.  Bituminous coal is used to generate electricity. That states that produce the most bituminous coal is West Virginia, Kentucky, and Pennsylvania. ANTHRACITE COAL Anthracite coal is very rare in the United States, it contains 86-97 percent carbon, and has a heating value slightly lower than bituminous coal.  Less than one-half of a percent of the coal mined in the U.S. is anthracite coal. All the anthracite mines in the United States are located in northeastern Pennsylvania. Not only is coal an important fuel option for the United States, it is something that the U.S. can export to other countries. There is some coal that is imported from other countries for use by electric power producers along U.S. coastlines. As the dependency on other countries for fuel reduces, it is expected that the importation of coal be reduced as more coal is mined in the U.S. and other energy options are explored.