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.  

 Coal deposits come from many epochs, but the best and most abundant are from the forests in the warm, swampy river deltas of the Carboniferous period, some 320 million years ago.

Long before the dinosaurs reigned, there was a time ruled by forests of giant ferns, reeds, and mosses. The earth was a warmer, steamier place back then and plants thrived, growing taller than our tallest trees today.

As these plants died, they fell into the swampy waters to form rich layers of peat. These layers were typically sandwiched between layers of sediment like shale, deposited when waters temporarily retreated. During the Permian period, about 290 million years ago, the seas receded entirely, and many coastal plains turned to desert. Sedimentary rocks like sandstone were laid down over the shale and peat. Later, limestone was laid down when the waters returned.

In time, the weight of the upper layers pressed down on the lower layers, causing tremendous pressure and heat. This triggered chemical changes in the peat, forcing out oxygen and hydrogen and leaving behind rich deposits of carbon, called coal.

The deeper the coal, the more pressure was exerted on it. This caused different grades of coal—from hard, pure anthracite to softer lignite. Between these layers lay bituminous coal, which is used in today's electric utility power plants. Coal-based electricity provides 56% of America's electricity.

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.

 

Coal in Electricity Generation

Coal is the major fuel used for generating electricity worldwide - countries heavily dependent on coal for electricity include (2006e):

Poland	93%	Israel	71%*	Czech Rep	59%
S Africa	93%*	Kazakhstan	70%*	Greece	58%
Australia	80%	India	69%*	USA	50%
PR China	78%	Morocco	69%*	Germany	47%

 

A Brief History of Coal Use

Coal is the most plentiful fuel in the fossil family and it has the longest and, perhaps, the most varied history. Coal has been used for heating since the cave man. Archeologists have also found evidence that the Romans in England used it in the second and third centuries (100-200 AD).

In the 1700s, the English found that coal could produce a fuel that burned cleaner and hotter than wood charcoal. However, it was the overwhelming need for energy to run the new technologies invented during the Industrial Revolution that provided the real opportunity for coal to fill Its first role as a dominant worldwide supplier of energy.

In North American, the Hopi Indians during the 1300s in what is now the U.S. Southwest used coal for cooking, heating and to bake the pottery they made from clay. Coal was later rediscovered in the United States by explorers in 1673. However, commercial coal mines did not start operation until the 1740s in Virginia.

The Industrial Revolution played a major role in expanding the use of coal. A man named James Watt invented the steam engine which made it possible for machines to do work previously done by humans and animals. Mr. Watt used coal to make the steam to run his engine.

During the first half of the 1800s, the Industrial Revolution spread to the United States. Steamships and steam-powered railroads were becoming the chief forms of transportation, and they used coal to fuel their boilers.

In the second half of the 1800s, more uses for coal were found.

During the Civil War, weapons factories were beginning to use coal. By 1875, coke (which is made from coal) replaced charcoal as the primary fuel for iron blast furnaces to make steel.

The burning of coal to generate electricity is a relative newcomer in the long history of this fossil fuel. It was in the 1880s when coal was first used to generate electricity for homes and factories.

Long after homes were being lighted by electricity produced by coal, many of them continued to have furnaces for heating and some had stoves for cooking that were fueled by coal.

Coal is our most abundant fossil fuel. The United States has more coal than the rest of the world has oil. There is still enough coal underground in this country to provide energy for the next 200 to 300 years.

Coal miners use giant machines to remove coal from the ground. They use two methods: surface or underground mining. Many U.S. coal beds are very near the ground's surface, and about two-thirds of coal production comes from surface mines.  Modern mining methods allow us to easily reach most of our coal reserves. Due to growth in surface mining and improved mining technology, the amount of coal produced by one miner in one hour has more than tripled since 1978.

Surface mining is used to produce most of the coal in the U.S. because it is less expensive than underground mining. Surface mining can be used when the coal is buried less than 200 feet underground. In surface mining, giant machines remove the top-soil and layers of rock to expose large beds of coal. Once the mining is finished, the dirt and rock are returned to the pit, the topsoil is replaced, and the area is replanted.

Underground mining, sometimes called deep mining, is used when the coal is buried several hundred feet below the surface. Some underground mines are 1,000 feet deep. To remove coal in these underground mines, miners ride elevators down deep mine shafts where they run machines that dig out the coal.

• Annually produces about 35% of total U.S. coal production.

• Large underground mines and small surface mines.

• Coal mined in the Appalachian coal region is primarily used for steam generation for electricity, metal production, and for export.

Interior Coal Region: 

• Annually produces approximately 13% of total U.S. coal production.

• Mid-sized surface mines.

• Mid- to large-sized companies.

Western Coal Region: 

• Annually produces about 52% of total U.S. coal production.

• The State of Wyoming (number one coal state) accounts for over 30% of total U.S. coal production.

• Large surface mines.

• Largest coal mines in the world.

• Coal provides America’s railroads with more traffic and revenue than any other commodity.
• A typical train car holds between 115 and 117 tons of coal.
• Wyoming is the largest coal-producing state.
• Coal accounts for half of the electricity use in the U.S.
• Coal costs less than any other major fossil fuel source.
• The world’s largest producers and consumers of coal are China, Poland, Russia, India and the United States.
• Total world consumption of marketed energy is projected to increase by 57 percent from 2004 to 2030.
• Coal’s share of total world energy use climbed from 25 percent in 2003 to 26 percent in 2004 and is expected to increase to 28 percent by 2030.
• America has more than 250 billion tons of recoverable coal reserves, the equivalent of 800 billion barrels of oil, more than three times Saudi Arabia’s proven oil reserves.
• Texas is the largest coal-consuming state in the U.S. and is the largest consumer of electricity.
• According to an electric power industry journal, 23 of the 25 power plants in the U.S. that have the lowest operating costs (and therefore provide power to their consumers at the lowest prices) are powered by coal.
• Today, America’s coal-based generating fleet is 70% cleaner (based upon regulated emissions per unit of energy produced) thanks, in part, to $50 billion invested in new technologies.
• Since 1970, the use of coal to generate electricity in the U.S. has nearly tripled in response to growing electricity demand.
• U.S. electricity demand continues to increase even as energy efficiency gains are made. Despite the fact that we are continuing to become more energy efficient, the U.S. Energy Information Administration projects that electricity demand will grow by 41% by 2030.
• Using coal to generate electricity is less than a 1/3 of the cost of other fuels.
• Intermittent energy resources like wind and solar are used for meeting peak energy demand because they are not always available. That is different from coal, which is used to provide “baseload” power — the constant, steady supply of electricity we depend upon throughout the day.
• America has more than 200 years of available coal reserves.

credit: Energy Information Administration, U.S. Department of Energy, World Coal institute, OPEC, Shell Oil company,American Coalition for Clean Coal Electricity, American Coal Foundation