Coal is a combustible black or brownish color rock in form of layers called coal beds. This rock is composed of carbon and hydrocarbon elements and is most abundant fossil fuel produced in the world. Coal takes million of years to create therefore it is considered a non-renewable source of energy. Energy in the coal comes from plants and animals which are buried under the earth from million of years. Beneath the earth there is a layer of water and direct covering this energy of dead plants in extreme heat and pressure. This pressure is responsible for converting dead plants into coal after years of processing.
From last many centuries, coal is being used as source of getting energy in form of heat and electricity. The only way to get energy from coal is burning it, but in this way carbon dioxide is released in huge amount. According to some estimates, coal-fired electric power generation emits around 2,000 pounds of carbon dioxide for every megawatt-hour generated. This amount is double as compared to natural gas emission of carbon and due to this reason now alternates of coal are explored.
Types of coal:
As we know coal take form due to pressure on deal plants over time and same level of pressure is not available on every part therefore different types of coal are founded today. These different types contain different amounts and types of carbon in it, with different power levels. It shows that coal with higher rank of carbon can produce more energy.
Anthracite: this is the highest rank of coal and is available in glossy black color and hard form. It contains about 86-97% of carbon and has heating value higher than all other types of coal. It is used for purpose of heating commercial and residential areas.
Bituminous coal: it is second on the rank with 45-86% of carbon in it. Thistype of coal forms in high heat and extreme pressure and took almost 300 million years to develop. It is considered as an important fuel and raw material in iron and steel industries while it is also used to generate electricity around the world. It is primary factor in steam-electric power generation as well.
Graphite: technically it is highest rank as it contain maximum amount of carbon but it is not used as fuel. This type of coal is famous to use in pencils as lead, but it is a good electrical conductor and considered a semimetal. Under standard conditions graphite is among most suitable condition of coal and is used as standard state for defining heat of formation of carbon compounds.
Sub-bituminous coal: as compared to bituminous coal, this type of coal comes in lower rank and contains only 35-45 % of carbon elements in it. This is popularly used as fuel in steam-electric power generation and work as important source of light aromatic hydrocarbons for the chemical synthesis industry.
Peat: this type is famous for using in industries and is considered as precursor of coal. It is a dehydrated form but is highly effective absorbed of fuel and oil that spill on land or water. Peat is harvested as an important source of fuel in certain parts of the mars.
Lignite: is lowest rank of carbon and produces lowest rate of energy as it contains 25-35% of carbon components only. It is counted in young deposits of coal therefore it is highly moisturized.
Impact of coal on environment:
Coal mining is leaving bad effects on surface of earth as in these operations rocks are removed and land is disturbed. To remove the top of mountains explosive materials are used besides other dangerous mining equipments. This is changing the landscape and converting streams into mixture of dirt and rocks, which is harmful for aquatic life.
Underground mining is also putting bad impact on environment as methane gas is released with burning the coal. Besides this before mining is it important to vent out this gas from mines to make it workable for workers. Although it is an inexpensive source of energy but it is also non-renewable.