Fossil Fuel

“Fossil fuels are the fuels formed by natural processes such as decomposition of dead and buried organisms. “

Table of Contents

What are Fossil Fuels?

Fossil fuels are buried flammable geologic deposits of organic substances such as dead plants and animals that got deposited under several thousand feet of silt. These deposits decayed with the passage of time and got converted to natural gas, coal and petroleum due to the extreme heat and pressure inside the earth’s crust. They are also known as non-renewable sources of energy as it takes a very long time for it to replenish.

Types, Formation and Uses of Fossil Fuels

Fossil fuels are of the following types:

  • Coal

  • Petroleum

  • Natural gas


  • It is a hard, black coloured substance made up of carbon, hydrogen, nitrogen, oxygen and sulphur.

  • The major types of coal are- anthracite, bituminous and lignite.

  • Anthracite has a higher carbon concentration and is the hardest type of coal.

  • Lignite has a high concentration of oxygen and hydrogen but a low concentration of carbon.

  • Bituminous is a moderate form of coal.

  • Coal is processed industrially to obtain derivatives like coke, coal tar and coal gas.

Formation of Coal

  • The process of formation of coal is known as coalification.

  • The dense forest present in the low-lying wetland got buried in the earth, millions of years ago.

  • Soil kept depositing over them and they got compressed.

  • As they went deeper and deeper, they faced high temperature and pressure.

  • As a result, the substances slowly got converted into coal.

Uses of Coal

  • Coal was used to produce steam in the railway engines initially.

  • It is used to cook food.

  • It is used to generate electricity in thermal plants.

  • It is used in industries as fuel.


  • It is a clear, oily liquid, usually green or black in colour.

  • It has a very strange smell and is a mixture of petroleum gas, diesel, paraffin wax, petrol, lubricating oil, etc.

  • It is also termed as “Black Gold” because of its wide range of uses in many industries.

Formation of Petroleum

  • The sea animals and plants died and their bodies settled at the bottom of the sea.

  • They got compressed by the layers of sand and clay.

  • Their encounter with high temperature and pressure converts them into petroleum.

  • The petroleum is separated from the crude oil by a series of processes in a refinery. This is known as petroleum refining.

Uses of Petroleum

  • It is used to power internal combustion engines in the form of petrol.

  • It is used in roofing, road pavements and as a water repellent.

  • It is used in manufacturing detergents, plastics, fibres, polyethene, etc.

Natural gas

  • It is a clean and non-toxic fossil fuel.

  • It is colourless and odourless and can be easily transferred through pipelines.

  • It is stored as compressed natural gas (CNG) under high pressure.

  • It is a less polluting and less expensive fossil fuel.

  • Methane is the most important natural gas.

Formation of Natural Gas

  • The phytoplankton and zooplankton sink to the bottom of the ocean and mix with organic materials to form an organic-rich mud.

  • The mud buried under more sediments and lithifies to form an organic shale. This prevents its exposure to oxygen. This is done to protect the organic materials from being decomposed by bacteria.

  • The increasing pressure and temperature transform the shale into a waxy material known as the kerogen.

  • At temperatures between 90-160°C kerogen is transformed into natural gas.

Uses of Natural gas

  • Compressed Natural Gas is used for generating power.

  • It is used as fuels in automobiles.

  • It can be used at homes for cooking.

  • It is used as a starting material in chemicals and fertilizers.

Are Fossil Fuels Renewable?

Fossil fuels are a non-renewable source of energy. Most of the energy used by us is obtained by the burning of fossil fuels. These fossil fuels are used up at a faster rate. They cannot be regrown at a scale compared to their consumption. With the increased demand for the production of various energies, fossil fuel energy is declining. It is difficult to replace them. That is why they are known as a non-renewable source of energy.

Advantages and Disadvantages of Fossil Fuels


  • Fossil fuels can generate a large amount of electricity at a single location.

  • They can be found very easily.

  • They are cost-effective.

  • Transportation of oil and gas can be done easily through pipelines.

  • They have become safer over time.

  • Despite being a finite resource, it is available in plenty.


  • Fossil fuels emit carbon dioxide when burnt which is a major greenhouse gas and the primary source of pollution. This has contributed to global warming.

  • They are a non-renewable resource, i.e., once used they cannot be replaced.

  • Combustion of fossil fuels makes the environment more acidic. This has led to unpredictable and negative changes in the environment.

  • Harvesting of fossil fuels also causes fatal diseases among the people. For eg., the coal miners often suffer from Black Lung Disease. The natural gas drillers are constantly exposed to chemicals and silica which is dangerous for their health.

These are the natural sources of energy and have extensive applications in industrial as well as domestic purposes.

For more information on Fossil Fuels or any related topics, please register at BYJU’S Biology.

Related Links

Coal and Petroleum
Flora and Fauna


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  1. This is nice, my child learned lots of this website, he said that he enjoyed it.

  2. It would have been good if assisted with diagrams for better understanding of beginners.