3.1 - Coal

Coal is a fossil fuel that forms from the remains of plants over millions of years. It is a non-renewable source of energy, which is primarily used as fuel in industries and power generation. Coal is mainly composed of carbon, along with various other elements such as hydrogen, sulfur, oxygen, and nitrogen. The process by which coal forms is called carbonization.

The formation of coal occurs in stages, beginning with the accumulation of plant material in swampy areas. Over time, heat and pressure transform the plant material into peat, which eventually becomes coal. The stages of coal formation are as follows:

• Peat: Peat is an early stage in the coal formation process. It is formed from the partial decomposition of plant material in waterlogged environments.
• Lignite: Lignite is the first stage of coal that has undergone compression and heating. It is a soft, brownish-black coal.
• Bituminous Coal: Bituminous coal is a denser and harder form of coal, used widely for power generation and industrial processes.
• Anthracite: Anthracite is the highest grade of coal, having the highest carbon content and energy density. It is hard, black, and shiny in appearance.

The carbon content of coal increases as it progresses through these stages. In general, the higher the carbon content, the more energy the coal can produce when burned.

Coal is commonly used for generating electricity in power plants, where it is burned to produce heat, which in turn converts water into steam. This steam drives turbines connected to generators, producing electricity. Apart from electricity generation, coal is also used in industries such as steel production, cement manufacturing, and as a source of various chemicals.

One of the key chemical reactions that occurs when coal is burned is the combustion reaction, which can be represented by the following equation:

$\text{C} + \text{O}_2 \rightarrow \text{CO}_2 + \text{heat}$

This reaction shows that coal (carbon) reacts with oxygen to form carbon dioxide and release energy in the form of heat.

Although coal is an important energy source, it has several environmental drawbacks. Burning coal releases harmful gases such as carbon dioxide (CO$_2$), sulfur dioxide (SO$_2$), and nitrogen oxides (NO$_x$), which contribute to air pollution and climate change. The mining of coal also results in land degradation and destruction of ecosystems.

In India, coal is the primary source of energy for electricity generation, and the country has one of the largest coal reserves in the world. The major coal-producing regions in India include Jharkhand, Odisha, Chhattisgarh, and West Bengal.

Despite the environmental issues associated with coal, it remains a vital part of the global energy mix due to its availability, energy density, and cost-effectiveness. However, there is a global shift towards cleaner energy sources like solar, wind, and hydropower to reduce dependence on coal.