Non-renewable sources of energy and types of fossil fuels

Non-renewable sources of energy are those that cannot be replenished within a short period of time. There are various types of conventional sources like coal, petroleum and natural gas. The article gives a complete detail of advantages and disadvantages of non-renewable sources of energy such as coal and petroleum.

Non-conventional sources of energy


Firewood or fuel wood is an energy source for a number of people in our country. Fuel wood is mostly obtained from twigs and branches of trees that have dried and fallen down. However, many people often cuts trees and then the wood obtained is called firewood or fuel wood. Firewood is more common in the rural areas where people do not access to any other source of energy.

Advantages of firewood

  • Firewood is very cheap as compared to other non-conventional sources of energy as well as renewable sources of energy. Since, the people of rural areas are mostly poor and often economical, they prefer this source of energy which is firewood or fuel wood.

  • Firewood is easily available in the rural areas as they have an ample areas covered with forests and vegetation. The other sources of energy are not easily available.

  • The rural people fell that the food and chapatis cooked on the fire of fuel wood is very healthy rather than the one cooked on LPG cylinder. This is generally a myth rather than a scientific fact.

  • Unlike the other sources of energy, firewood can be regenerated. Tress could be planted and we would get a plenty of firewood.

    Disadvantages of firewood

  • A large volume of firewood is to be burnt in order to get a relatively small amount of energy. So, one has to collect a large amount of fuel wood in order to get this small amount of energy. This creates a collection ans storage problem.

  • Fuel wood is mostly used for cooking and cannot be used for running huge machines and generating electricity.

  • Burning of firewood releases a huge amount of smoke. In many households, when fuel wood is used for cooking people, the women develops respiratory problems.

  • Fuel wood releases carbon dioxide. Carbon dioxide is a greenhouse gas and causes global warming.

  • The demand for firewood will harm trees and deforestation takes place to fulfill the demand for fuel wood. In fact, many sanctuaries and national parks are still under threat due to the demand for fuel wood.


    Coal is a non-renewable source of energy. Coal is a readily combustible black or brownish black rock. Coal was the first fossil fuel to be seriously used. It triggered the entire industrial revolution in Europe. It is the largest source for generation of electricity world wide, as well as largest source of carbon dioxide emissions, which contribute to climatic change and global warming. Our country has rich supplies of coal but not of petroleum.

    Process of formation of coal

    Coal is called a fossil fuels as it was formed from the remains of vegetations that grew as long a 400 million years ago. It is often referred to as " buried sunshine" as the plants which formed coal captured energy from the sun through photosynthesis to create the compounds that make up the plant tissue. The most important element in the plant material which gives a lot of energy is carbon. Most of our coal was formed around 300 million years ago, when much of the earth was covered by swampy areas. As plants and tress died, their remains sank to the bottom of the swampy areas, accumulating layer upon layer and eventually forming a soggy, dense material called peat. Over the long periods of time, the makeup of the earth's surface changed, and seas and great rivers caused deposits of clay, sand and other material to accumulate, burying the peat. The pressure caused by the weight squeezed water from the peat. In the presence of heat and pressure, coal was formed. The whole process is called carbonization.

    Types of coal

    There are five different categories of coal based on the period and area of formation. The quality of coal and its capacity to yield energy is judged form the percentage of carbon in the coal. More the carbon, better the coal is. There are five different types of coal:

  • Anthracite: It is the best among all the varieties of coal. It contains about 90 to 95% carbon. It burns with a bluish flame and does not emits any smoke. It is also the most expensive coal and is mostly used for industrial purpose as a raw material and not as a source of energy. It has a very low sulfur and moisture content. It represents the last stage in the formation of coal.

  • Bituminous: It represents the last second stage in th formation of coal. It contains as much as 80 to 85% carbon. it is also a good variety of coal and is mostly found in India in Jammu and Kashmir region. It is used for domestic purposes such as cooking. It has alternative strips of dark and light bands.

  • Lignite: It is also called brown coal as it is somewhat brown in color. It contains 5o to 60% carbon content and produces a lot of smoke. It is used as a source of energy in blast furnaces and also for the production of electricity. India thrives in such as variety of coal.

  • Peat: It represents the first stage in the formation of coal and is the lowest grade of coal available. It contains less than 40% carbon and has very high moisture and sulfur content. It emits a lot of smoke and yields very less amount of energy due to low calorific value.

    Disadvantages of coal

    There are various demerits of coal. Some of them are:
  • Coal has a very less calorific value. Hence, a large amount of cola is required to produce very less amount of energy.

  • Coal is non-renewable which means that one it is exhausted, it shall take another millions of years for its formation.

  • Coal emits carbon dioxide, nitrous oxides, sulfur dioxide etc. They are all greenhouse gases that cause global warming.

  • Coal also leaves fly ash that act as suspended particulate matter (SPM) and when inhaled, caused respiratory problems.


    Petroleum is derived from two words- petra meaning " rock" and oleum meaning " oil". It consists of hydrocarbons mixed with oxygen, sulfur, nitrogen and other elements in varying proportion. From crude petroleum, various products are made by fractional distillation and other processes. For example, fuel oil, petrol, kerosene, diesel and lubricating oil. Petroleum products and chemicals are used in large quantities in the manufacture of detergents, artificial fibers, plastics, insecticides, fertilizers, pharmaceuticals, toiletries and synthetic rubber.

    Process of formation of petroleum

    Petroleum was formed from the remains of marine plant and animal life that existed millions of years ago. Some of these remains remained deposited under the sea where they were decomposed anaerobically by bacteria. The bacteria changed the fats into the sediments of the body into fatty acids which were then changed into an asphaltic material called kerogen. This was then converted over millions of years ago into petroleum by the combined action of heat and pressure. Petroleum generally occurs trapped between two impermeable layers of rock. Impermeable layers are non-porous.

    Natural gas

    Natural gas is a gaseous fossil fuel. It consists primarily of methane. Other gases included are ethane, propane, butane and pentane. Methane is a molecule that is made up of one carbon atom anf four hydrogen atoms. Natural gas is a fossil fuel like oil and coal.
    It remained associated with coal and petroleum deposits. Natural gas has many applications. Compressed natural gas(CNG) is a cleaner alternative to other automobile such as petrol and diesel. Natural gas is a vital component of the world's energy supply. It is one of the cleanest, safest and most useful of all energy sources.
    Similarly, Liquified natural gas(LNG) is natural gas that has been liquified under pressure and then stored in containers. It is mostly used in cylinders for cooking purposes. As it is odorless, a foul smelling gas called "methyl mercaptane" is added to detect its leakage.

    Advantages of CNG

    Following are the merits of CNG gas:
  • Very easy on the engine, giving longer service life and lower maintenance costs.

  • Reduces th demand for petroleum.

  • educe exhaust emission pollution.

  • Improves fuel consumption and engine efficiency.

  • Dry gaseous fuel does not dilute the lubricating oil and thus saves on oil filters and oil chargers.

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