Fossil Fuels Coal Petroleum

Fossil fuels are formed from the decomposed remains of plants and animals that died over a million years ago. The fossil remains slowly got transformed into fuels after being trapped under intense heat and pressure for many millions of years. The three primary fossil fuels are coal, petroleum, natural gas. Among these three, coal and oil are used widely to serve a wide array of purposes. This includes transportation fuel, electricity generation, heating buildings and houses, steel and paper production, and so on. These two fuels coal and petrol have been discussed in detail below.

Coal 

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Coal is a black or brownish sedimentary rock with a high carbon content that is typically used as fuel. It was formed millions of years ago during the Carboniferous Period of the late Paleozoic Era, which lasted from 360 million years to 290 million years. 

The Earth’s surface during this era was covered in shallow seas that periodically flooded the dense forest areas resulting in the creation of swampy wetlands. Over time, due to tectonic activity, plants and vegetation from these swampy areas and peat bogs slowly got buried under Earth’s surface. 

The peat bogs face extreme heat and pressure while being buried and get transformed into peat and then finally into anthracite coal. This process wherein the vegetation material slowly changes to form coal is known as coalification. 

Based on the degree of coalification that it underwent, coal can be classified into several groups which are as follows. 

1. Anthracite 

This is the best quality coal that is available on the surface of Earth. It is of a dark black colour which signifies the fact that it is high in carbon content, which is nearly 95%. Aside from that, this coal type is hard, low in moisture content. 

Anthracite is also the oldest coal type found on Earth’s surface since it was formed around 350 million years ago, which is why it has an energy density of approximately 33 MJ/Kg and reaches a high temperature very quickly on being ignited. Another interesting feature of anthracite coal is that while burning it produces very less smoke as compared to other types of coal and petrol.

2. Bituminous 

Next to anthracite, bituminous is the second-best quality of coal found on Earth with a carbon content that ranges from 76 – 86%. This coal type formed around 300 million years ago and has a low moisture content and energy density at 27 MJ/Kg. These features make it ideal for usage in the production of steel, cement, electricity. 

3. Sub-bituminous 

This coal type is usually either dark brown or grey-black. This coal type is the most used and has the properties of lignite coal as well as bituminous coal. It formed around 251 million years ago and has a carbon content of 70-76% and an energy density of 18-23 MJ/Kg. 

4. Lignite

Lignite, which is brownish, is the lowest quality coal available. Since it is only 60 million years old, it is also low in carbon content, around 65% - 70%. Lignite coal is also high in moisture content with an energy density of 18 MJ/Kg. 

Apart from coalification, other factors significantly affect the quality of coal. These are as follows. 

1. Duration of the coal formation in the deposit

2. Temperature and pressure in the depths

3. The depth of coal deposit

4. Type of vegetation from which the coal was first formed

Coal and petrol are extracted from the Earth’s surface either via surface mining or through underground mining. After it has been extracted, it can be directly used for several purposes such as fuel, generating electricity, production of steel, and manufacturing a variety of synthetic products.

Petroleum

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Petroleum is a type of fossil fuel that is found on Earth’s surface in liquid, solid, and even in a gaseous state. However, in a gaseous state, petroleum is known as natural gas and as bitumen in solid form.

While coal was formed from the dead remains of vegetation and peats, petroleum was formed from the fossilized remains of ancient marine organisms that underwent heat and pressure for a million years. 

The dead remains of ancient marine organisms including plants, algae, plankton sank down to the seabed where they were got buried deep under the Earth’s mantle at very high temperature. Without the presence of any oxygen, the dead remains got transformed into a waxy substance called kerogen. 

Eventually, as more time passed, this kerogen was converted into hydrocarbons like coal and petrol through a process called catagenesis. 

Petroleum is usually jet black in colour. However, it can also be reddish, yellowish, tan, or even greenish in colour. This variation in colour is due to the difference in chemical composition. 

Like coal, natural gas and petroleum is an indispensable part of 21st-century life. This fuel is utilized in almost every aspect of life.

1. As a source of energy – transportation fuel such as gasoline, petrol, diesel, liquefied petroleum gas, jet fuel, marine, etc. are derived from petroleum

2. Generation of electricity

3. Machine lubricants

4. Pharmaceutical products

5. Petroleum by-products used in the chemical industry as raw materials

6. Domestic use such as kerosene, vaseline, waxes, etc.

Coal and petrol reservoirs are distributed unevenly all over the world. For instance, Middle Eastern countries like Iraq, Kuwait, Iran hold around 23% of the world’s petroleum reserves, followed by Saudi Arabia, which accounts for 16% of the reserve. On the other hand, in the western hemisphere, Venezuela is the largest oil exporter accounting for around 298 billion barrels of oil reserves.