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2. Lignite: eventually over time, with increasing pressures and temperatures, peat changes into
coal’s next stage, lignite.
It contains 60% to 70% of carbon. It is brown in colour and still contains a high amount of
water. Lignite has a higher heat content than peat. It is used in thermal power plants.
3. Bituminous: it is formed as more pressure is applied to lignite coal. The greater the force
applied the more water is expelled, which increases the amount of pure carbon present and
increases the heat content of the coal. It contains 70-86% of carbon. This is also used to
generate electricity.

4. Anthracite: it is considered the highest grade of coal. It has very light weight when compared
to other coals. It’s very hard and is dark brown in colour. It contains 86-92% of carbon and
produces large amount of heat. It can also be used for power generation.

Coal as a source of energy: Coal is mainly carbon. When heated in air, coal burns and produces
mainly carbon dioxide gas. A lot of heat energy is also produced.

Carbon + Oxygen Carbon dioxide + Heat

Uses of Coal:
 It is used as fuel in homes and industries.
 It is used at thermal power plants to generate electricity.
 It is used to make coal gas which is an important industrial fuel.
 It is used to make coke.

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