Fossil fuels.
Extraction of oil

Thermal Power Plant Cercs. Catalonia

Treatment of fossil fuels

Thermal energy and combustion.
Effects of thermodynamics

Fossil Fuels

Fossil Fuels

Fossil fuels are often referred to as a type of negative, polluting, environmentally damaging energy.

Currently, fossil fuels are the most widely used energy source in the world. It is used to generate electrical energy but above all it is also used to generate mechanical energy (cars, heat engines, etc.).

What are fossil fuels?

Fossil fuels are those fuels that come from a process of partial decomposition of organic matter.

Fossil fuels originate from a transformation process of millions of years of plants and vegetables (cases of oil, coal and natural gas).

These are primary energy sources since they can be obtained directly without transformation.

Formation of fossil fuels

Fossil fuels are formed by a process of partial decomposition of organic matter. It is a transformation process of millions of years due to the pressure and temperature that several layers of sediment exert on organic matter.

They originated naturally due to a fossilization process in environmental anoxia (lack of oxygen): organic matter has not been degraded by microorganisms (which can not live), but remains in the form of more complex, solid organic molecules ( coal), liquid (oil) or gas (natural gas). The energy of these molecules is what is released in using them as fuel.

This process of millions of years is the one that turns fossil fuels into a non-renewable source of energy, since it is consumed much faster than it is not generated.

Importance of fossil fuels

Fossil fuels have a high calorific value that makes them a very important source of useful energy to generate thermal energy.

The use of fossil fuels has allowed the great economic and demographic growth linked to the industrial revolution of the 19th century. At present they are fundamental for our economy. In 2007, the combustion of coal, oil and natural gas accounted for 86.4% of the world's primary energy.

Consequences of the use of fossil fuels

Fossil fuels are highly unpopular for environmental groups. Its combustion generates a lot of gases. These gases become one of the main sources of atmospheric pollution because they contribute to increasing the greenhouse effect and, consequently, to global warming.

Today, the use of fossil fuels is an important problem of sustainability, both for environmental and economic reasons (the planet's resources are limited and will one day be exhausted).

Types of fossil fuels

Three main types of fossil fuels are distinguished: they are petroleum (liquid), coal (solid) and natural gas (gas).


Oil is a mineral oil, constituted by hydrocarbons, contained in large pockets in the upper strata of the earth's crust.

This fossil fuel, once refined, gives a large number of products used as a source of energy, especially in the automotive and thermal engines. These products include gasoline, diesel, fuel, etc. They can also be used as raw material for the petrochemical industry.


Man working with a mountain of coal

Coal or coal is a black sedimentary rock, very rich in carbon and with varying amounts of other elements, mainly hydrogen, sulfur, oxygen and nitrogen.

Most of the coal was formed during the Carboniferous period (from 359 to 299 million years ago).

Natural gas

Natural gas is a source of fossil energy, as are coal or oil. It is constituted by a mixture of hydrocarbons, molecules formed by carbon and hydrogen atoms. Its calorific value varies greatly according to its composition, but the highest are between 8,500 and 10,200 kilocalories per cubic meter of gas.

This is the cleanest fossil energy in terms of waste and atmospheric emissions, and the most efficient fuel for obtaining electricity in thermal power plants, with a total efficiency of 50.7% compared to 25.7% of fuel , 26.1% of the uranium (nuclear power plant) and 26.8% of the coal.

Natural gas can be used directly without having to previously transform it into electricity. This feature allows it to have a much higher efficiency of 91.2%. Its storage is cheaper and easier than coal and petroleum products.

It began to be used from the 1960s as the preferred fuel, except in transportation, where oil continues to predominate. In addition, it is also used as a raw material for many chemical products.

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Last review: November 15, 2016