Learn What Coal Is, How It's Formed and Where It's Found

What is Coal and How it Forms

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There are several types of coal. In the image above, you can see a large specimen of Anthracite on the left and two smaller samples of Cannel coal on the right. Photo: Bolton Museum, UK

Coal is a combustible, sedimentary, organic rock, which is composed mainly of carbon, hydrogen, and oxygen. It is formed from vegetation, which has been consolidated between other rock strata and altered by the combined effects of pressure and heat over millions of years to form coal seams.

Coal is a fossil fuel and is far more plentiful than oil or gas, with around 119 years of coal remaining worldwide.

"Coal is a fossil fuel and is the altered remains of prehistoric vegetation that originally accumulated in swamps and peat bogs" (World Coal Association).

"The energy we get from coal today comes from the energy that plants absorbed from the sun millions of years ago. All living plants store solar energy through a process known as photosynthesis. When plants die, this energy is usually released as the plants decay. Under conditions favourable to coal formation, the decaying process is interrupted, preventing the release of the stored solar energy. The energy is locked into the coal" (Source: World Coal Association website)

"It takes 10 metres of peat to form 1 metre of coal, and it may take 7,000 years to accumulate this much peat", reports the Bolton Museum on its website.

So what would you say: renewable or non-renewable?

Types of Coal

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Different Types of Coal and Their Respective Uses. Source: World Coal Institute

From Lignite to Anthracite, and from power generation to domestic use, the different types of coal depends on the organic maturity of plant remains. This maturity obviously happens during the geologic ages and produced different types of coal that offer different characteristics (color, hardness, oxygen, hydrogen and sulfur balance). These different types of coal are consequently used for different purposes.

Starting from the peat, the first output of the conversion process is the lignite (also known as "brown coal"). The continuing effects of temperature and pressure might transform lignite into sub-bituminous coals. Sub-bituminous coal might become harder and blacker, being then converted into bituminous coal (also known as "hard coal"); anthracite coal being is at the end of the evolution chain, containing the lowest rate of impurities.

Where is Coal Found?

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The biggest reserves are in the USA, Russia, China and India. Source: World Coal Institute

"Coal reserves are available in almost every country worldwide, with recoverable reserves in around 70 countries".(Source: World Coal Association)

  • Proven coal worldwide reserves: over 847 billion tons
  • This means 119 years, at current rates of production (proven oil and gas reserves are equivalent to around 46 and 63 years at current production levels)

How can coal reserves be extended?

  • Exploration through actual technology and process
  • Exploitation of presently inaccessible (for technical and/or safety reasons) but identified resources, thanks to technological progress
  • Optimization of coal use, increasing the energy ratio per ton of coal

Source: World Coal Association website