Coal

Coal is a black or brownish-black sedimentary rock that is primarily composed of carbon, along with various other elements including sulfur, hydrogen, nitrogen, and oxygen. It is formed from the remains of ancient plants that lived and died millions of years ago, and has been used as a fuel source for thousands of years.

Coal is mined from the earth's surface or from underground mines and is used to generate electricity, heat homes and buildings, and to produce steel. It is considered to be a relatively cheap and plentiful source of energy, although it is also a major source of greenhouse gas emissions and air pollution.

There are four main types of coal: anthracite, bituminous, sub-bituminous, and lignite, which are classified based on their carbon content and energy content. The higher the carbon content, the higher the energy content and the higher the quality of the coal.

Coal is a non-renewable energy source, meaning that it takes millions of years to form and that once it is extracted, it cannot be replenished. Due to its impact on the environment, many countries are working to reduce their dependence on coal and to transition to cleaner and more sustainable sources of energy such as wind, solar, and hydropower.