Coal is one of the prime sources of energy. It is the combustible fossil fuel which is responsible for majority of generation of electricity. Based on the huge accumulation of organic matter including mainly trees, plants, shrubs etc, which continued to be decayed over the period of millions of years, we can deduce that it is a very long process. The formation of coal that we are using today began around 300 million years ago. This gives us a rough picture of how is coal formed actually, over the period of time.

Genesis of coal is a continuous process. Basically, coal is the outcome of decayed plants which accumulate their energy from sun through the process of photosynthesis that helps in generating the plant tissues. Carbon is the major constituent in the plant material which gives coal most of the energy. Then coal beds are mostly found in those areas which were swampy millions of years ago. As the old plants and trees fell upon, then began to settle under these areas leading to the formation of layers of these rotten organic matters. Over the period of time, the subsequent lower layers got squeezed by the pressure and heat of upper layers. As a result, occurrences some physical changes lead to the dissipation of oxygen from the organic matter leaving behind most of the carbon which took the shape of coal and summarise that how is coal formed. The generation of coal was marked only in marshy areas because in those places only, most of the vegetations sunk down and aggregated. They were made to force deep down by the upper layer of dead trees and plants. These suitable conditions for the formation of coal were not prevailing in hilly or desert areas.

Furthermore, the coals can be categorised based on their energy content. How is coal formed is also defined by its carbon content. As of now, we have following 3 types of coal available:

• Lignite Coal
• Bituminous Coal
• Anthracite Coal

Lignite coal has the lowest carbon content. It has less energy and heat content. It's major use lies in producing synthetic natural gas and generating fertilizers. Next one in the category is Bituminous coal, which has the sufficient heating value. 80% of bituminous coal is used for the purpose of generating electricity and the major support behind textile and plastic industries. The last one is Anthracite coal. Having metallic looks and a deep black color, it has the highest content of carbon which burns for much longer duration and produce least soot, as the by product.