Frequently Asked Questions About Coal

What is Coal?
How Was Coal Formed?
What Are the Four Major Categories of Coal?
Where Is Coal Found?
How Plentiful Is Coal?
How Is Coal Mined?
What Is Land Reclamation?
What Is Coal Used For?
Why Is Coal Used to Generate Electricity?
How Is Coal Transported?
 

Note for teachers: Have students learn all about coal by exploring this page and answering the questions on this Coal Worksheet, created by Corey Soumis, Chemistry & Natural Resources teacher at Calumet High School in Calumet, Michigan.
 
What Is Coal?
Coal is a burnable carbonaceous rock that contains large amounts of carbon. Coal is also a fossil fuel—a substance that contains the remains of plants and animals and that can be burned to release energy. Coal contains elements such as hydrogen, oxygen, and nitrogen; has various amounts of minerals; and is itself considered to be a mineral of organic origin.
 
How Was Coal Formed?
Scientists believe that during the Carboniferous Period (280 to 345 million years ago) large amounts of plant life and other organic matter grew in the swampy areas and lagoons that covered much of the earth. As the plants and other life forms died, they drifted down to the bottom of the swamps, slowly decomposed, and formed peat—a soggy, spongelike material. The peat became buried and compressed under the earth’s surfaces over a long period of time. Over millions of years and through the forces of heat and pressure, the compressed peat became coal. The greater the heat and pressure, the harder the coal was that formed.
 
Learn more about the formation of coal and get your classroom involved with our ACF Lesson Plans: Coal Formation (grades K-6) and How Was Coal Formed? (grades 5-8).

What Are the Four Major Categories of Coal?
Coal is classified into four categories, or ranks, based on how it responded to increasing heat and pressure over long periods of time and how much carbon it contains:

Lignite (soft): This type of coal contains a lot of moisture and ash and breaks apart easily. Of the four types, lignite has the lowest carbon content and heating value. Also called brown coal, lignite is used mainly at electricity-generating plants.

 

Subbituminous (medium-soft): This dull black coal has less moisture than lignite. Subbituminous is generally used to produce steam for electricity generation. Reserves of subbituminous coal are found mostly in western states and Alaska.

 

 

Bituminous (medium-hard): This type of coal, which contains very little moisture, has high heat value. It is used to generate electricity and to produce coke, a coal residue used in the steel industry. Bituminous coal is the most plentiful type in the United States.

 

Anthracite (hard): This type of coal has the highest carbon content and the lowest moisture and ash content. Anthracite burns slowly and makes a good heating fuel for homes. The United States has about 7.3 billion tons of anthracite, most of which can be found in Pennsylvania.

 

Where Is Coal Found?
Proven coal deposits exist on every continent, including Antarctica. The United States has the world’s largest supply of recoverable reserves, or about 24 percent. Coal is found in 38 states, and nearly one-eighth of the country lies over coal beds. Top coal-mining states include Montana, Wyoming, Illinois, West Virginia, Kentucky, Pennsylvania, Ohio, Colorado, Texas, and New Mexico.

See a map of coal reserves in the United States

How Plentiful Is Coal?
Coal supplies in the United States are far more plentiful than domestic oil or natural gas; they account for more than 90 percent of the country’s fossil fuel reserves and more than 60 percent of the world’s fuel reserves. The United States has about 260 billion tons of recoverable coal, which could last us about 235 years if we continue using coal at the same rate as we use it today. In addition, the United States has more than 25 percent of the world’s estimated coal reserves. To meet energy and metallurgical needs, the United States mines over a billion tons a year of coal. The rest of the world mines another 4 billion tons per year.
 
How Is Coal Mined?
There are two basic ways to mine coal:

  1. Surface mining is used when coal is found close to the surface or on hillsides. It involves removing the topsoil and subsoil and setting them aside. Machines such as draglines, wheel excavators, and large shovels remove the earth and rock and uncover the coal. This removed material is called overburden. After the coal is removed and loaded into trucks, the area is refilled with the overburden, covered with the soils that were removed, and reseeded. To the extent possible, the area is restored to its original condition or improved.
  2. Underground mining is used to extract coal that is deep beneath the surface or in seams exposed on hillsides. It involves drilling two openings called shaftsinto the coal bed—one to transport miners and equipment, and the other to bring coal to the surface. Next, the coal is broken into manageable sizes and mined by
    • conventional mining, or using explosives to break up a coal seam;
    • continuous mining, or using machines with large, rotating cutters that break into the coal and arms that scoop the coal onto a built-in conveyor; or
    • longwall mining, or using cutting machines that work along walls of coal up to 1,000 feet long to cut coal and drop it onto a conveyor belt.

    Take a look at this video on how underground coal mining works.

    The top 15 coal producing states in 2010 were Wyoming, West Virginia, Kentucky, Pennsylvania, Montana, Texas, Indiana, Illinois, North Dakota, Ohio, Colorado, Virginia, New Mexico, Alabama, and Utah.

What Is Land Reclamation?
Land reclamation is the process of protecting, restoring, and possibly even improving the land before, during, and after surface mining. As coal is removed from one section of a surface mine, the land at another part is returned, regraded, and replanted. In the end, this means that the land is preserved, nature has been protected, water and soil are conserved, and the land can be turned into productive farmland, forests, and lakes.
 
Reclaimed land has been successfully used for wildlife preserves, golf courses, recreational parks, commercial development sites, pastures, and farmlands. Since the mid-1970s, more than 2 million acres of mined lands owned by coal producers have been reclaimed. In addition, 100,000 acres of abandoned sites that were mined earlier in the 20th century have been reclaimed using funds paid by today’s coal producers.
 
What Is Coal Used For?
Coal is primarily used to generate electricity. In fact, nine out of every ten tons of coal mined in the United States today is used to generate electricity, and about 56 percent of the electricity used in this country is coal-generated electricity.
 
In addition, manufacturing plants and industries use coal to make chemicals, cement, paper, ceramics, and metal products, to name a few. Coal’s methanol and ethylene are used to make products such as plastics, medicines, fertilizers, and tar.
 
Certain industries consume large amounts of coal. For example, concrete and paper companies burn coal, and the steel industry uses coke and coal by-products to make steel for bridges, buildings, and automobiles. Coal is still used in the iron and steel industry, but the domestic use of coke, a substance made by heating coal to very high temperatures, has decreased because of changes in blast-furnace and steel-making technologies as well as shifts in steel demand.
 
About 9 percent of U.S.-mined coal is also exported to more than 35 countries, including those in Western Europe, Canada, and Japan.  In 2011, 107 million tons of coal were exported from the United States and almost 40,000 people worked in the industries that support the export of coal (think barges, crane operators, port workers, financial experts, railroad engineers, etc.)  The top ports from which most coal is exported are in Virginia, Louisiana, Maryland, Alabama and Washington.  To learn more about coal exports click here.
 
Why Is Coal Used to Generate Electricity?
Coal is used to generate electricity because it is a reliable and low-cost energy source produced in compliance with our nation’s environmental laws. In the United States, 23 of the 25 electricity-generation power plants with the lowest operating costs are using coal.
 
Inexpensive electricity, such as that generated by coal, means lower operating costs for businesses and for homeowners, which helps to boost the economy, moderate inflation, and increase coal’s competitiveness in the marketplace.
 
See a chart of states where using coal to provide electricity leads to lower electricity costs

How Is Coal Transported?
Trains, barges, trucks, and conveyors transport coal. Nearly 60 percent of all coal is transported by railroad. Barges are used to move coal along the nation’s 25,000 miles of waterways, and trucks and conveyors move smaller amounts of coal over shorter distances.
 
There is even a coal slurry pipeline connecting a mine in Arizona with a power plant in Nevada. With this method, coal is ground to a powder, mixed with water to form a slurry, and pumped through a pipeline.

 

Return to Coal Energy Facts