Coal consists mainly of carbon (C) and hydrogen (H).
These two atoms form a strong chemical bond, which can be broken by adding energy in the form of heat. Carbon and hydrogen bind to oxygen during combustion.
This process releases more energy than is necessary to break the bond between C and H. Due to the surplus of energy, the combustion becomes self-reinforcing.© Shutterstock
Cheaper than oil
In addition to carbon and hydrogen, coal often also contains sulfur. Because of that sulfur, coal is the most polluting fuel that exists.
The quality of a fuel is determined by the energy in gigajoules (GJ) that a ton produces. Although a tonne of coal produces less energy than oil, for example, the fuel is easier and cheaper to extract.
Coal loses from oil
You get almost twice as much energy from oil and natural gas, but coal is much cheaper to extract.
Coal: 27 GJ / ton.
Fuel oil: 43 GJ / ton.
Natural gas: 48 GJ / ton.
Beech wood: 15 GJ / ton.
Sawdust: 15.2 GJ / ton.
Flax seeds: 25 GJ / ton.
Straw: 14.4 GJ / ton.