Coal is the United States’, and world’s, leading source of electricity, and is second only to oil in total energy production. But as we continue to discuss coal’s importance and controversial nature, the Ink thought it was time to give our general readership a basic primer on what coal exactly is. Of course, most everyone has a basic understanding of it. Coal is a combustible carbon based material that formed some 290 to 390 million years ago. Prehistoric vegetation became trapped under layer after layer of sediment and was forced under the increasing pressure of these layers into coal.
But let’s go a little deeper into the explanation. Plants basically contain energy. They absorb solar energy through photosynthesis which allows them to grow and thrive. When they die, that material begins to decay, releasing their stored energy. But when trapped under the pressure of sediment layers which form on top of it, that material is not only compressed, the energy within it remains locked in place. After millions of years of compression, that material becomes “rock-like”. Most people’s perception of coal is the hard black rock that miners pull from under the earth. But did you know that a lot of coal can look much like dark dirt? Well now you do.
There are actually four major types of coal. The type we usually imagine as a hard, shiny, black rock is called Anthracite. It is the highest quality of coal found on the planet because it has the lowest moisture content, highest carbon content, and highest density (hardness) of the four types as it has had the most amount of time to harden under pressure. But anthracite is also the rarest of the types and is thus only responsible for .3% (3 tenths of a percent) of all energy produced in the United States.
The next type and next highest level of coal, is called Bituminous (pronounced either beh’-too mehnus or bī’- too mehnus). It is responsible for 54% of the total energy produced in the U.S. It also has that typical “rock like” look but is easier to break apart and thus contains more moisture and less carbon.
Sub-Bituminous is a type of coal which contains even more moisture and lower carbon content and density yet makes the foundation of coal operations in the Powder River Basin of Montana and Wyoming. Wyoming produces more coal than any other state in the U.S. – by far, mining nearly 40% of all coal in the country.
The lesser known and lowest value coal is Lignite. It is also referred to as brown coal due to its appearance. North Dakota’s lignite is the largest reserve of this type in the country making it the country’s tenth largest coal producing state.
By the way – charcoal is not coal at all. It is actually made from charred wood chips. Do not grill your hot dogs over sub-bituminous coal. (that’s a joke, OK?.... but don’t do it!)