What is coal?

9 February 2015

Most people know coal as a fossil fuel which is used to produce around 40 percent of the world's electricity.1 It’s a flammable black or brown sedimentary rock, and is made mostly of organic carbon.

However, there are actually two main types of coal: ‘thermal’ coal, which is mostly used for power generation, and ‘metallurgical’ coal, which is mostly used for steel production. Thermal coal is more abundant, has lower carbon content and is higher in moisture than metallurgical coal.

As well as generating power, coal is also commonly used in cement manufacturing and as a component of thousands of other products.2

Both types of coal are formed in a similar manner; from decomposed vegetation that was compressed beneath layers of sand, sediment and rock at high temperatures over millions of years.

It’s typically found as layers (coal beds) or veins (coal seams) and in Australia, coal is mined above and below the ground.


Australia’s coal deposits are believed to be 140 - 225 million years old.3


How does coal make electricity?

Simply put, coal-fired electricity generation is a five-step process:

  1. Thermal coal (either black or brown) that has been pulverised to a fine powder is burned
  2. The resulting heat is used to turn water into steam
  3. The steam at very high pressure is then used to spin a turbine, connected to an electrical generator
  4. The spinning turbine causes large magnets to turn within copper wire coils; this is called the generator
  5. The moving magnets cause electrons in the wires to move from one place to another, creating an electrical current and producing electricity.

 

In Australia, the electricity is transported along transmission and distribution power lines, through a sophisticated, connected grid, to your home or workplace.

You can find out more about the grid here.

Read more about coal in Australia.

  1. World Coal Association 2013, Coal statistics
  2. Geoscience Australia 2012, Coal fact sheet, Australian atlas of minerals resources, mines and processing centres, Commonwealth of Australia, Canberra.
  3. Geoscience Australia 2012, Coal fact sheet, Australian atlas of minerals resources, mines and processing centres, Commonwealth of Australia, Canberra.
     

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