Coal
Coal is a combustible black or dark brown silt-like sedimentary rock composed of carbon and assorted other elements, formed over millions of years by the gradual decomposition and compaction of organic matter. Coal is primarily used as a source of energy, providing fuel for various industrial activities, electricity generation, and, in some cases, residential heating. Coal comes in a variety of different forms, ranging from anthracite to bituminous coal to sub-bituminous coal.
Anthracite is the highest grade of coal and is the hardest and most valuable in terms of energy per unit of mass, due to its high carbon content. It is typically found in eastern parts of North America and is most often used to generate power. Bituminous coal is the intermediate grade of coal and is softer but still strong. It is typically found across North America and can be used for power generation and residential heating. Sub-bituminous coal is the lowest grade of coal, is softer still than bituminous coal, and has a lower carbon content. It is typically found in the western parts of the United States, and is primarily used for power generation.
In addition to its use as a source of energy, coal has a number of other applications. Coking coal, or metallurgical coal, is a lower grade of coal that is heated in ovens to create coke, which is primarily used in steel production. Coal tar is also produced in the process and can be used in asphalt and roofing materials. Coal can also be refined into a number of liquid fuels, including petrol and diesel.
The extraction of coal has a major environmental impact, due to the presence of carbon dioxide, nitrous oxide, and sulfur dioxide in the exhaust from burning it. Coal combustion also produces particulate matter, which can have serious implications for human health, particularly in regards to respiratory problems. The waste material resulting from coal extraction and burning is referred to as coal ash, which can contain a number of toxic substances, including heavy metals, such as arsenic and lead.
The worlds total coal reserves are estimated to be around 1 trillion tons, with the United States possessing the largest known coal reserves. Coal currently accounts for a third of global energy consumption and is the most abundant fossil fuel in use. Many nations, including the United States, rely heavily on coal as an energy source, and its use is expected to continue to increase in the years to come.
