There is probably not a single person in the United States that is not dependent to some extent on coal. Coal is at work each time you turn on a switch that allows electricity to power up your lights, microwave, stereo, TV, computer and all those other electircal appliances and gadgets you have lying around the house.

And where does the rest of our electricity come from?

• Nuclear plants provide about 24%
• Oil fired plants 10%
• Hydroelectric dams 8%
• Alternative energy sources (wind, solar etc.) 2%

COAL is a fossil fuel. It is derived from plant material that was buried millions of years ago in a four step process:

1. Lush vegetation grew in warm swampy areas that covered much of the United States (and the world) about 300 million years ago. The plants and trees absorbed the rays of the sun - used in photosynthesis - which was stored in the leaves and tissues.

2. As the vegetation died, it fell into the swamps. As the amount of material accumulated in the presence of the water, it began to form a spongy, brown material which we know as peat or peat moss.

3. Over time, geologic forces buried the peat bogs - sometimes hundreds of feet deep - where they were compacted by the pressure of the soil and rock on top of them.

4. Coal was gradually formed from the buried peat. The greater the pressure under which the coal was formed, the harder the coal that was produced.

There are four major types of coal. From the softest to the hardest they are:

• Lignite coal - The softest of the four types of coal. It is a brownish black in color, very crumbly and primarily used for the generation of electricity. Because of its color, it is often referred to as "brown coal." Lignite is the result of millions of tons of plants and trees that decayed in a swampy atmosphere about 50-70 million years ago. The material on top of the lignite deposits in North Dakota and Montana - called overburden - was deposited by runoff from the west as the Rocky Mountains formed. The heating content of lignite is approximately 4,000-8,000 Btu's per pound. The carbon content of lignite is 25%-35% and it has a very high water content - about 35 percent. For more information about lignite, visit the Lignite Energy Council website.

This illustration shows the profile (or cross-section) of a coal mine. Note the overburden.
(Courtesy of Black Hills Corp. Wyodak Mine)

• Sub-bituminous coal - This is a medium soft coal that contains much less moisture than lignite and is not nearly as crumbly. Like lignite, its primary use is in the generation of electricity. The carbon content of sub-bituminous coal runs from 35%-45% and its heat value generally ranges from 8,000-13,000 Btu's per pound. It is produced primarily along the east side of the Rocky Mountains from eastern Montana to the four corners area where the states of Arizona, Colorado, New Mexico and Utah join.

• Bituminous coal contains even less moisture than the sub-bituminous type. The carbon content of bituminous coal is generally from 45%-85%. Its heat value ranges from 10,500-15,000 Btu's per pound - greater than either lignite or the sub-bituminous types. In addition to being used for electrical generation, it is also used in making coke or coking coal, an essential ingredient in making steel. Most production of bituminous coal is from the east coast to the midwest states and in Alaska.

• Anthracite coal - discovered in 1769 - is the hardest of the four types. It averages 85%-95% carbon content and has the highest heating value of the four types of coal. It is not uncommon to find anthracite that produces well in excess of 15,000 Btu's per pound. To put that in perspective, that is roughly one and one-half times as much heat as the same volume of oil and four times as much as seasoned hard-maple firewood. Anthracite makes excellent home heating fuel because it burns cleanly, does not produce volatile gases and does not deteriorate. It can be stored on the ground for long periods of time without creating environmental problems. Anthracite is mined in only a few areas, mostly in the eastern Pennsylvania region. It is used extensively in municipal water purification and treatment plants and for home heating.

(Information courtesy of the USGS)

Coal is mined in 32 states. The three major U.S. coal producing regions are Appalachia (West Virginia, Pennsylvania, Virginia, Eastern Kentucky, and Ohio), the Illinois Basin (Illinois, Indiana and Western Kentucky) and the Powder River Basin (Wyoming and Montana). Lignite coal is produced primarily in western North Dakota and in eastern Montana.

• Appalachian mines produce primarily bituminous coal from both surface and underground mines. Appalachian coal tends to be high in energy content and low in sulphur.

• Illinois Basin mines also produce primarily bituminous coal but are generally underground operations, yielding coal that is high in energy content but also high in sulfur.

• Powder River Basin coal is of the sub-bituminous type and generally mined from the surface. Basin coal, while often lower in energy content, is known for its particularly low sulfur content.

The way the layers or seams of coal occur and the has much to do with how it is mined and its ultimate cost to consumers. For example, in Illinois Basin mines, 50 feet of overburden must often be removed to reach a 5-10 foot seam of coal. At the other end of the spectrum, in the Powder River Basin, you may only have to remove 5 feet of overburden to get to a 50 foot thick seam - substantially lowering the cost of mining.

The seams of coal are clearly visible in this photo taken at a Colorado mine.
(Courtesy of Kenncott Colowyo Mine)

Since acid rain is such an important environmental issue, the sulfur content of coal is VERY important. A major cause of acid rain is said to be sulfur dioxide emissions. When sulfur dioxide is mixed with water, a chemical reaction takes place and sulfuric acid is formed. Government regulations set the emission standards that must be met by every company that burns coal.

Ironically, one of the ways to reduce those emissions (and thus reduce acid rain) is for power plants to install scrubbers on their stacks. Another mineral - limestone - is used in the scrubbers to help remove the sulfur before it finds its way into the atmosphere.

Nearly 950 million tons of coal are produced annually in the United States. The top ten coal producing states by rank and tonnage produced are:

If we continue mining coal at current rates, the US has between 500 and 1,000 years of coal reserves remaining. Put another way, it means that, at a minimum, and IF we choose to do so, we have enough coal reserves to produce electricity at current consumption rates for a period equal to that time between the time Columbus first set foot in the New World and today.

The following table shows the ten states with the largest reserves of coal. It also shows the total figure for all the reserves in the remaining 40 states.

The days of mining coal with picks, shovels and pit ponies are gone forever. Todays miner is a different breed. His pick and shovel have been replaced by instrument panels on huge trucks, front-end loaders and draglines or by a computer console.

This picture shows a dragline at work at the far end of the mine. To put the size of the
equipment in perspective, the tires on the loader in the foreground are taller than a man!
(Courtesy of Peabody Lee Ranch Mine)

The mines where this equipment is used do not look much like the images of old, either. In today's underground mine, the walls are white, covered with a coating of lime that prevents coal dust. Constant fresh air flows steadily through the mine, moved by huge ventilation fans on the surface. Personal protective equipment including hard-hats, steel-toed boots, hearing protection, air purifying systems and high intensity lamps are standard issue for the modern miner.

Mining is a temporary use of the land. When mining of an area has been completed, the mining company is required by federal and state law to return the land and water to as good, or better, condition as before mining. Since 1974, more than two million acres of land - an area larger than the state of Delaware - have been reclaimed for other uses ranging from recreation to housing development.

The next time you flip a switch to get that electrical power you need, remember that there are miles and miles of wires and lines that connect your home to a power plant you may never see. And chances are, at least 56% of the time, that power plant will be burning coal. To see how all that electricity is produced, take the online tour of a coal-fired power plant at the Lignite Energy Councils website.

If you still need additional information about coal, the best site I know of is the Virtual Coal Library compiled by the Australians. It is well organized, easy to navigate and contains worldwide information and links.