Coal and petroleum have organic origin, being decomposed plant and animal matter buried deep inside the earth. Coal is mined like any other mineral.The chief coal producing countries in the world are China, U.S.A., U.S.S.R., U.K., Germany, Poland, Australia and India. In India, coal is mainly mined in Bihar, West Bengal, Madhya Pradesh and to some extent in Andhra Pradesh.
Petroleum occurs deep inside the Earth at depth ranging from a few hundred to few thousand meters. The name petroleum has been given to the crude oil because it occurs under the Earth's crust entrapped in rocks (petra = rocks oleum = oil). Crude oil (petroleum) is pumped out of Earth by drilling oil wells. Petroleum is obtained by drilling a hole through the crust till it reaches the oil reserve. The oil gushes out of its own due to high pressure of the gas over its surface. However, when the pressure falls, it is pumped out with the help of pumps. Large quantity of natural gas is generally associated with petroleum. Petroleum is often referred to as liquid gold, due to its importance in transportation, commerce and industry. Prosperity of any country depends upon its petroleum reserves.The chief petroleum producing countries are, U.S.A., U.S.S.R., Saudi Arabia, Kuwait, Iraq, Iran, Libya, Nigeria, Algeria, Venezuela China and Mexico.
Composition of coal and petroleum
Coal is mainly composed of carbon. Coal, is classified into different varieties depending upon its carbon content. Common varieties of coal are,Variety of coal: Peat Lignite Bituminous AnthraciteCarbon content:10-15% 40% 60-70% 80-90%
Coal also contains arenes or aromatic hydrocarbons like benzene, toluene, xylene, naphthalene and anthracene. It also has some organic compounds of sulphur and nitrogen.Crude oil (or petroleum) is a dark brown viscous liquid sometimes having a greenish tinge. Crude oil is a mixture of about 150 different organic compounds. Crude oil is largely made up of aliphatic hydrocarbons, with much lesser amounts of aromatic compounds and organic compounds of sulphur and nitrogen.
Formation of coal and petroleum in nature
It is believed that coal in nature was formed from the remains of the trees buried inside the earth some 500 million years ago. Due to the bacterial and chemical action on the wood, it got converted into peat. Then, as a result of high temperature and high pressure inside the earth peat got transformed into coal.