Anthracite and bituminous coal are two types of coal that are critical to the economy of the United States. Anthracite coal is used in a variety of manufacturing processes, but its primary use is in the formation of steel. Bituminous coal, on the other hand, is the type of coal most commonly used in America to produce electricity. The chemical make-up and creation process is what makes these types of coal so distinct from each other.
In general, anthracite is harder than bituminous coal. This is because it contains more carbon. In fact, both types of coal started out as the same thick deposits of soaked woody and organic material that collected in swamps about 280 to 330 million years ago. As time passed, this material turned into peat deposits that were buried by dirt and silt. Over millions of years this material was buried thousands of feet under the ground.
Some of the peat that was buried will be exposed to high temperatures. These high temperatures will cause some of the easily vaporized compounds in the peat to evaporate, leaving behind a material with a high percentage of carbon. This material is what makes up bituminous coal.
Anthracite coal is formed in a similar manner, but it starts as peat that is buried several more miles underground, typically under thick sheets of rock. Because it is buried further underground, the peat is exposed to even higher temperatures than bituminous coal. This means that even great amounts of extraneous materials are evaporated from the peat, leaving coal with an even higher percentage of carbon.
In fact, whether coal is considered to be anthracite or bituminous is determined only by its carbon content. By definition, bituminous coal contains less than 86 percent fixed carbon while anthracite contains 86 percent or more fixed carbon.
Because of the difference in their relative levels of carbon, each of these types of coal is used very differently. Bituminous coal is mostly burned in order to generate electricity. It can also be used to produce heat for some industrial purposes. In the past, bituminous coal has been used to make coke, a component necessary for the production of steel. Modern manufacturing processes have greatly reduced the demand for this particular use of bituminous coal, however.
Anthracite is rarer than bituminous coal, and it makes up a much smaller segment of the U.S. coal market. While anthracite can be used to generate electricity, it is mostly used as a heat source. While it has historically been used for home heating, this use has fallen in popularity in recent years.
