A Brief Introduction of Fossil Fuels Coal and 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.
Duration of the coal formation in the deposit
Temperature and pressure in the depths
The depth of coal deposit
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.
As a source of energy – transportation fuel such as gasoline, petrol, diesel, liquefied petroleum gas, jet fuel, marine, etc. are derived from petroleum
Generation of electricity
Machine lubricants
Pharmaceutical products
Petroleum by-products used in the chemical industry as raw materials
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.
FAQs on Fossil Fuels Coal Petroleum
1. What are fossil fuels and why are they named that?
Fossil fuels are natural substances formed from the buried, decomposed remains of ancient plants and animals that lived millions of years ago. They are named 'fossil' fuels because they originate from the fossilised remains of these dead organisms, which were subjected to intense heat and pressure deep within the Earth's crust.
2. What are the three main types of fossil fuels?
The three primary types of fossil fuels are:
- Coal: A solid, black or brownish-black sedimentary rock primarily composed of carbon. It is formed from ancient terrestrial plant matter.
- Petroleum (Crude Oil): A liquid mixture of hydrocarbons found in underground reservoirs. It is formed from the remains of ancient marine microorganisms like algae and zooplankton.
- Natural Gas: A gaseous mixture, primarily methane, often found alongside petroleum deposits. It is the cleanest burning of all fossil fuels.
3. How is coal formed in the Earth's crust?
Coal is formed through a process called carbonisation. Millions of years ago, dense forests in low-lying wetland areas died and were buried under layers of sediment. Over time, intense heat and pressure from the overlying rock layers compressed this organic matter, driving out water and other substances, and gradually transforming it into carbon-rich coal.
4. What are the different useful products obtained from the refining of petroleum?
Petroleum is separated into various useful products through a process called fractional distillation. Some of the most important products include:
- LPG (Liquefied Petroleum Gas): Used as a fuel for homes and industry.
- Petrol (Gasoline): Used as fuel for light motor vehicles.
- Kerosene: Used as fuel for stoves, lamps, and jet aircraft.
- Diesel: Used as fuel for heavy motor vehicles and electric generators.
- Lubricating Oil: Used for lubrication of machinery.
- Paraffin Wax: Used for making candles, ointments, and waxed paper.
- Bitumen: Used for road surfacing and paints.
5. What is the environmental impact of burning fossil fuels like coal and petroleum?
Burning fossil fuels releases several harmful substances into the atmosphere. The primary impact is the release of large amounts of carbon dioxide (CO₂), a major greenhouse gas that traps heat and contributes to global warming. They also release pollutants like sulphur dioxide and nitrogen oxides, which can lead to acid rain and respiratory problems.
6. Why is petroleum often referred to as 'black gold'?
Petroleum is called 'black gold' due to its immense economic value and importance to modern society. The 'black' refers to the dark, viscous appearance of crude oil when it is extracted from the ground. The 'gold' refers to its high value, as it is the source of fuels that power transportation and industry, and the raw material for countless products like plastics, chemicals, and medicines, making it a cornerstone of the global economy.
7. How do coal, petroleum, and natural gas differ in their formation and physical state?
While all are fossil fuels, they differ significantly. Coal is a solid fuel formed primarily from the remains of terrestrial plants like trees and ferns in swampy environments. In contrast, petroleum (liquid) and natural gas (gas) are typically formed from the remains of tiny marine organisms, such as algae and plankton, that settled on the ocean floor and were buried under sediment.
8. If fossil fuels come from organic matter, why can't we create more of them to solve the energy crisis?
The formation of fossil fuels is a process that takes millions of years under very specific geological conditions of extreme heat and pressure. These conditions cannot be replicated on a human timescale or artificially on a large scale. Because we consume them far faster than they are naturally created, they are classified as non-renewable resources.
9. What is the difference between coke, coal tar, and coal gas?
These are all products obtained from the processing of coal. Coke is a tough, porous, and almost pure form of carbon left behind after heating coal in the absence of air; it is mainly used in steel manufacturing. Coal Tar is a thick, black liquid produced during the same process, which is a source for manufacturing paints, dyes, and explosives. Coal Gas is the flammable gas produced, which is used as a fuel in industries.
10. Besides fuel, what are some everyday applications of petroleum products?
Petroleum is a versatile raw material used far beyond just fuel. Many everyday items are derived from petrochemicals, including:
- Plastics: Used in bottles, containers, toys, and electronics.
- Synthetic Fabrics: Materials like polyester and nylon for clothing.
- Detergents and Soaps: Many cleaning agents have petroleum-based ingredients.
- Asphalt: Used to pave roads and roofs.
- Cosmetics and Pharmaceuticals: Used in making lotions, creams, and various medicines.
