Coal energy 101
Coal is an organic energy source formed from decayed plant materials. When pressure and heat compact the material into a solid, the process is known as coalification. Because this process takes millions of years to form, coal is considered a non-renewable source of energy.
Coal currently produces 40 percent of the world’s electricity, and demand for coal is expected to continue growing by 37 percent through 2040, according to the International Energy Agency. (source)
Where is coal found?
Coal is found in “coal seams” or “coal beds.” These seams can be as thick as 30 meters and stretch 1,500 kilometers (source).
Coal can be found on every continent. The largest coal reserves are in the United States, Russia, China, Australia and India.
Types of coal
According to the U.S. Energy Information Administration, coal is classified into four main categories: anthracite, bituminous, sub-bituminous and lignite. The coalification process has an important influence on the coal’s physical and chemical properties and is referred to as rank. The longer the coalification process, the more carbon content will be contained per unit weight of coal.
Anthracite contains 86 to 97% carbon, and has the highest heating value of all types of coal. This type of coal is referred to as “hard coal.” Anthracite is sometimes used for household cooking and heating fuel.
Bituminous accounts for about 50% of the coal produced in the United States (source). It has a carbon content of between 77 and 87%, and is generally referred to as “soft coal.” Premium-grade bituminous coal is used to produce coke, a key ingredient in iron and steelmaking.
Sub-bituminous coal has a carbon content of 71 to 77%, and has a heating value between 8,300 and 12,000 British Thermal Units (BTUs) per pound.
Lignite holds the lowest rank among coal types, and is generally only used for the generation of electricity.
Uses of Coal
Coal is generally used to generate electricity by the power sector, and acts as the energy source in the steel, cement, paper and other industries (source).
In the developing world, coal is relied on heavily as a source of electricity (source). For those who lack access to modern energy services such as electricity and clean cooking fuels, coal often provides an essential fuel.
Coal and the environment
There are many impacts to the environment with regard to mining coal, with the degree of impact dependent on the type of method used to extract the coal. For example, surface mines requiring the use of explosions alter the environment, and the water draining from these areas may contain pollutants that harm aquatic wildlife. Laws have been put in place to ensure areas that are mined are reclaimed close to their original condition.
Coal mined through underground methods has less impact on the environment. The largest impact of underground mining may be methane gas that must be vented to make the mines a safe place to work (source).
Coal is one of the leading producers of carbon dioxide emissions, in comparison to other electricity generation fuel sources.
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