There are two ways to remove coal from the ground—surface and underground mining. Surface mining is used when a coal seam is relatively close to the surface, usually within 200 feet. The first step in surface mining is to remove and store the soil and rock covering the coal, called the overburden. Workers use a variety of equipment—draglines, power shovels, bulldozers, and front-end loaders—to expose the coal seam for mining.
After surface mining, workers replace the overburden, grade it, cover it with topsoil, and fertilize and seed the area. This land reclamation is required by law and helps restore the biological balance of the area and prevent erosion. The land can then be used for croplands, wildlife habitats, recreation, or as sites for commercial development.
Although only about a third of the nation’s coal can be extracted by surface mining, more than two-thirds of all coal in the U.S. is mined using this method today. Why? Surface mining is typically much less expensive than underground mining. With new technologies, productivity has more than tripled since 1973.
Underground (or deep) mining is used when the coal seam is buried several hundred feet below the surface. In underground mining, workers and machinery go down a vertical shaft or a slanted tunnel called a slope to remove the coal. Mine shafts may sink as deep as 1,000 feet.
One method of underground mining is called room-and-pillar mining. With this method, much of the coal must be left behind to support the mine’s roofs and walls. Sometimes as much as half the coal is left behind in large column formations to keep the mine from collapsing.
A more efficient and safer underground mining method, called longwall mining, uses a specially shielded machine that allows a mined-out area to collapse in a controlled manner. This method is called longwall mining because huge blocks of coal up to several hundred feet wide can be removed.
Processing and Transporting Coal
After coal comes out of the ground, it typically goes on a conveyor belt to a preparation plant that is located at the mining site.
The plant cleans and processes coal to remove dirt, rock, ash, sulfur, and other impurities, increasing the heating value of the coal.
After the coal is mined and processed, it is ready to go to market. It is very important to consider transportation when comparing coal with other energy sources because sometimes transporting the coal can cost more than mining it.
Underground pipelines can easily move petroleum and natural gas to market. But that’s not so for coal. Huge trains transport most coal (almost 60 percent) for at least part of its journey to market.
It is cheaper to transport coal on river barges, but this option is not always available. Coal can also be moved by trucks and conveyors if the coal mine is close by. Ideally, coal-fired power plants are built near coal mines to minimize transportation costs.
After surface mining, workers replace the overburden, grade it, cover it with topsoil, and fertilize and seed the area. This land reclamation is required by law and helps restore the biological balance of the area and prevent erosion. The land can then be used for croplands, wildlife habitats, recreation, or as sites for commercial development.
Although only about a third of the nation’s coal can be extracted by surface mining, more than two-thirds of all coal in the U.S. is mined using this method today. Why? Surface mining is typically much less expensive than underground mining. With new technologies, productivity has more than tripled since 1973.
Underground (or deep) mining is used when the coal seam is buried several hundred feet below the surface. In underground mining, workers and machinery go down a vertical shaft or a slanted tunnel called a slope to remove the coal. Mine shafts may sink as deep as 1,000 feet.
One method of underground mining is called room-and-pillar mining. With this method, much of the coal must be left behind to support the mine’s roofs and walls. Sometimes as much as half the coal is left behind in large column formations to keep the mine from collapsing.
A more efficient and safer underground mining method, called longwall mining, uses a specially shielded machine that allows a mined-out area to collapse in a controlled manner. This method is called longwall mining because huge blocks of coal up to several hundred feet wide can be removed.
Processing and Transporting Coal
After coal comes out of the ground, it typically goes on a conveyor belt to a preparation plant that is located at the mining site.
The plant cleans and processes coal to remove dirt, rock, ash, sulfur, and other impurities, increasing the heating value of the coal.
After the coal is mined and processed, it is ready to go to market. It is very important to consider transportation when comparing coal with other energy sources because sometimes transporting the coal can cost more than mining it.
Underground pipelines can easily move petroleum and natural gas to market. But that’s not so for coal. Huge trains transport most coal (almost 60 percent) for at least part of its journey to market.
It is cheaper to transport coal on river barges, but this option is not always available. Coal can also be moved by trucks and conveyors if the coal mine is close by. Ideally, coal-fired power plants are built near coal mines to minimize transportation costs.
SURFACE MINING
DEEP MINING