We need energy in different forms for all our daily activities. The conventional sources of energy include firewood, cattle dung cakes, minerals like coal, petroleum and natural gas, and electricity generated by flowing water or burning fuel.
The non-conventional sources of energy include solar energy, wind energy, tidal energy, geothermal energy, atomic energy and biogas. Firewood and cattle dung cakes are the primary sources of energy, meeting around 70% of the total energy requirement in our villages.
The intense heat and pressure over millions of years has turned prehistoric plant material buried under the earth into coal. The variety of coal depends on how long the plant material has been buried, at what depth and under how much pressure. Peat is a low carbon variety that has high moisture and provides low heat output. Lignite is a soft, low-grade variety of coal that has high moisture content and appears brownish in colour.
Bituminous coal is formed from plant material buried deep in the earth and subjected to very high temperature. Bituminous coal is the most important commercial variety of coal used in metallurgical applications like smelting of iron. The best and the most expensive variety of coal is called anthracite.
In India, coal is found as Gondwana deposits that are over 200 million years old, and tertiary deposits that are just about 55 million years old. The Gondwana deposits in India are found in the Damodar valley in West Bengal and Jharkhand and the Mahanadi, Godavari, Son and Wardha valleys. Tertiary deposits of coal are found in the north-eastern states of Assam, Meghalaya, Arunachal Pradesh and Nagaland.
Coal is bulky and expensive to transport in large quantities so, most power plants and heavy industries relying on coal are located near coal fields. Petroleum provides fuels like petrol and diesel, industrial lubricants and raw material for a number of industries including textiles, fertilisers and cosmetics.
Petroleum deposits are found in anticlines and fault traps in rock formations. Off-shore oil fields in Mumbai High account for 63% of the total petroleum production in India. This is followed by 18% of the production coming from Gujarat and 16% from Assam. Ankaleshwar in Gujarat, and Digboi, Naharkatiya and Moran-Hugrijan in Assam are other major oil fields in India. Assam is the oldest oil-producing state in India.
Natural gas is a mixture of gases, primarily methane, which is found trapped in rocks. Natural gas is used as auto fuel (CNG), to generate electricity and in the fertiliser industry. Large deposits of natural gas have been found in the Krishna-Godavari basin, Mumbai High, the Gulf of Cambay and the Andaman and Nicobar Islands.
The natural gas fields in Mumbai High and Bassein are linked to the power and fertiliser plants in western and northern India by the 1700-kilometre long Hazira-Vijaipur-Jagdishpur or HVJ Natural Gas Pipeline.