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What is Coal? - Facts, Types, Formation & Uses

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  • 0:00 Some Facts on Coal
  • 0:55 Types of Coal
  • 2:55 Formation of Coal
  • 4:10 Uses of Coal
  • 5:25 Lesson Summary
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Lesson Transcript
Instructor: Kimberly Schulte

Kimberly has taught at the university level for over 17 years.

Did you know that each person uses 3.7 tons of coal annually? Did you also know that coal, as a fossil fuel, comes from a source that was once alive? Learn about coal, its current uses, and possible future.

Some Facts on Coal

Whether you realize it or not, coal is a big part of your daily life. In the past, coal has been used to heat homes, to cook with, and even to draw with. But what is coal?

Coal is the most abundant fossil fuel found on the planet. Fossil fuels are energy sources that formed millions of years ago and are considered nonrenewable resources. They also include oil and natural gas. Coal is a fossil fuel that was formed from once-living plants of various types.

Coal and humankind have a long, intertwined history. The fossil fuel was even being used by cavemen, though its first extensive use was by the Roman Empire. Today, coal accounts for 94% of the United States' fossil fuel energy reserve. It's found in 38 U.S. states and it's the number one energy resource used to generate electricity globally.

Types of Coal

The four types of coal are peat, lignite, bituminous, and anthracite. Peat is often not listed as a type of coal since the use of it as an energy source is limited today. However, it's still a type of coal and can be used as an energy source.

Peat is the first step in coal formation. Peat is composed of over 60% organic matter; typically, ferns and vegetation found in swamps or bogs. As a result of the high water content of this environment, peat contains a lot of water, which limits its heat content or the amount of energy it contains. It's a very soft brown coal.

Eventually over time, with increasing pressures and temperatures, peat is 'cooked' into coal's next stage, lignite. Lignite is a soft brown coal that still contains a high amount of water. Lignite has a higher heat content than peat but is still not the most desired form of coal. However, lignite makes up almost half of our known coal reserves.

Bituminous coal is formed as more pressure is applied to lignite coal. The greater the pressure applied, the more water is expelled, which increases the amount of pure carbon present and increases the heat content of the coal. Bituminous coal is often classified as sub-bituminous or bituminous. The difference is that sub-bituminous is the transition stage from lignite to bituminous coal. Bituminous coal is widely used in the United States and across Europe.

Anthracite coal is a metamorphic rock and is considered the highest grade coal. It's hard and dark black in color. It has a very light weight when compared to other forms of coal, as there is very little water present in anthracite. As a result, anthracite has the highest heat content. Anthracite is formed when bituminous coal is subjected to great pressures, such as those associated with the folding of rock during the creation of mountain ranges.

Formation of Coal

As mentioned earlier, coal is formed from ancient swamps and bogs. The vegetation found in these areas eventually become buried beneath sediment and rock called overburden. As more and more overburden is added, the buried vegetation becomes compressed. The temperature and pressure are also increasing as a result of the overburden. Under these conditions, the buried vegetation is kept free of oxygen by the presence of mud and acidic water. Slowly over time, the buried vegetation is 'cooked' to coal. The process of turning dead carbon-rich vegetation to coal is called carbonization.

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