Difference Between Coal and Petroleum
Coal, one of humankind’s primary energy sources derived from vegetable matter. The original decaying vegetation has been subjected to pressure and heat over long periods of time, this alters its chemical and physical characteristics. Because the final product may have a variety of chemical compositions, coal is classified as a rock rather than as a mineral. Coal is further classified according to grade, or purity, defined as the percentage of carbon content; according to type, depending on variations in the original plant composition; and according to rank, depending on the degree of metamorphism. Of these three criteria, purity (grade) and degree of metamorphism (rank) are, in practice, most important.
Petroleum, a thick, flammable, and usually dark-colored liquid fuel found deep below the earth’s surface or occasionally in springs and pools at the surface. It is composed mainly of complex combinations of hydrogen and carbon called hydrocarbons, along with organic compounds containing sulfur, nitrogen, and oxygen in varying amounts.
Most geologists believe that petroleum was derived from plant and animal material deposited in enormous quantities in sedimentary beds millions of years ago. Both plant and animal marine life flourished on the ocean floor, and this organic matter was buried by layers of fragmentary rock deposited over it. The covering layers prevented complete oxidation and decomposition, while the increased pressure and heat caused a partial distillation of the organic matter, resulting in the formation of oil and gas. This theory is supported by the fact that petroleum is found in porous sedimentary-rock deposits. However, the source bed for the petroleum in any given pool is not known because the fluid oil or gas may have traveled for long distances through the porous parts of rock structures.
Petroleum deposits, many of which also contain natural gas, occur in many regions of the world. Petroleum as it is brought to the surface is called crude oil. The crude oil is transported from the field to a refinery, which converts the crude oil to many useful products, including gasoline, heating oils, and jet aircraft fuels.
Modern technological civilization depends largely on the energy stored in petroleum, natural gas, and coal. Petroleum products power motor vehicles, diesel locomotives, ships, and aircraft, provide fuel for electric power plants and for heating homes, and play an indispensable role in industry and military operations.