Coal knowledge

Coal has dominated the world energy scenario since the Eighteenth century, up to 1970 and in 2024 it accounts for approximately 28% of the primary consumption of energy (Source: Eni World Energy Review 2025). The greatest limit of coal is that it is the most polluting source of energy and it negatively affects the state of the climate. When compared to natural gas, production of one kilowatt-hour of electricity from coal generates more than twice the amount of nitrogen oxide, eight times the amount of heavy metals, ten times the amount of fine dust, and it also produces a large amount of sulphur oxides.

Coal is a fossil fuel just like oil and natural gas. Unlike them, coal is a solid fuel and as such it is the most exploited solid fuel for the production of electric energy in the world.

Their different state is explained by the different origin of such three fuels. Whereas oil and natural gas come from the rests of microscopic organisms living in water (plankton, seashells, coral, etc.) deposited at the bottom of ancient seas, coal formed from the rests of plants of the past, the structure and form of which, albeit modified, can still be identified by means of a microscope.

Carbon is the main component of coal after the other basic components of the original living matter (hydrogen, oxygen and nitrogen) progressively decayed during chemical and physical processes transforming it. The combustion of coal frees the energy of the sun stored in plants thanks to the photosynthesis millions of years ago: therefore it is an invaluable container of “fossil” solar energy.

Where is it

The favourable environment for the formation of coal includes the vast coastal, lagoon or swampy plains where in the past the hot and humid climate developed a rich vegetation. The low sinking of the soil led the vegetal organisms to be quickly buried by sand and clay carried by rivers.

What is for

Coal is a widely used energy source and it is the main fuel source for the production of electric energy. In electric energy plants the coal is burnt to heat water until it turns into steam that, under pressure, turns a turbine, which is connected to a generator. The mechanic energy of rotation is then transformed into electric energy.

A bit of history

The age of coal starts towards the mid 1600s, stimulated by the need for finding an alternative energy source to wood. Up to then, wood had been the most commonly used energy source, and also a good building material; however, the excessive exploitation of woods led many European countries to progressively destroy their forests, and wood started to be rare.