Fossil Fuels: 3 Types, Formation, Advantages, Disadvantages

Fossil fuels are derived from the decomposition of plants and animals. These fuels, which are present in the Earth’s crust and include carbon and hydrogen, may be burnt to generate energy. Fossil fuels include coal, oil, and natural gas. The kind of fossil, the quantity of heat, and the amount of pressure determine the production of fossil fuels—either oil, natural gas, or coal—from these fossils. Fossil fuels have been powering economies for almost 150 years and now provide over 80% of the world’s energy.

Fossil Fuels 3 Types, Formation, Advantages, Disadvantages
Fossil Fuels 3 Types, Formation, Advantages, Disadvantages

Fossil fuels developed millions of years ago from the carbon-rich traces of animals and plants as they decayed and were crushed and heated underground. When fossil fuels are burnt, the carbon and other greenhouse gases that have been stored are released into the atmosphere. Excess greenhouse gas accumulation in the atmosphere has resulted in major changes to the Earth’s climate, a trend that will increase as more fossil fuels are used.

What are Fossil Fuels?

Fossil fuels are combustible geologic deposits of organic things such as dead plants and animals that have been buried beneath several thousand feet of sediment. Due to the intense heat and pressure inside the earth’s crust, these deposits decomposed over time and transformed to natural gas, coal, and petroleum. Carbon and hydrogen bonding are the primary components of fossil fuels. Coal, oil, and natural gas are the three forms of fossil fuels that may all be utilized to provide energy.

Coal is a substance that is typically found in sedimentary rock formations where layers of rock and dead plant and animal materials are stacked up. More than half of the weight of a lump of coal must come from ancient plants.

Oil was discovered as a solid substance between layers of sedimentary rock, such as shale. This substance is heated to create the thick oil that may be used to generate gasoline.

Natural gas is commonly discovered in pockets above oil reserves. It can also be found in non-oil-containing sedimentary rock strata. Methane is the primary component of natural gas.

Types of Fossil Fuels and Its Formation


Coal is a byproduct of fossilized wetlands, while some earlier coal deposits that existed prior to terrestrial plants are believed to be the result of algal deposits.

Coal is generated when plant material is buried, heated, and crushed for an extended length of time in oxygen-depleted circumstances. Millions of years ago, continents were scattered throughout the globe with varying temperatures, and swamp-like vegetation covered most of the land. Because of the low oxygen levels, the plant could not fully degrade when it perished. Instead, it generated peat (a brown organic material). After millions of years of tremendous pressure and temperature, the peat was buried and transformed into coal. The pressure was caused by sediment weight as well as continental collisions.

There are various sorts of coal, each with a distinct quality. The more the heat and pressure that coal is subjected to during formation, the higher its fuel value and the more valuable the coal. The overall progression of a swamp into the different phases of coal is as follows:

Swamp → Peat → Lignite → Subbituminous coal → Bituminous coal → Anthracitic coal → Graphite

  • Peat compacts to create solid rock through a process known as lithification, yielding lignite (brown coal, a low-quality type of coal).
  • With increased heat and pressure, lignite transforms into subbituminous coal and bituminous coal. Because they are composed of compacted sediments, lignite, subbituminous coal, and bituminous coal are classified as sedimentary rocks.
  • Bituminous coal is converted to anthracite, a high-grade coal that is the most valuable coal since it produces the greatest energy.
  • Anthracite is classified as a metamorphic rock because it has been compressed and altered to the point where it is denser than other types of coal and no longer includes sheet-like layers of sediments. With even greater heat and pressure, anthracite may be converted to graphite by removing all the components that evaporate easily and leaving only pure carbon.


Oil, or hydrocarbon as it is often known, is an organic substance composed of hydrogen and carbon in the widest sense. These reside in the earth’s subsoil as liquids known as (crude) oil or petroleum.

Because petroleum and natural gas are generated from old biomass, they are referred to as “fossil” fuels.

Heating ancient organic material resulted in the long-term creation of crude oil and natural gas via a complicated series of biochemical and geological processes of pressure and seclusion from air (anaerobic conditions). The organic material, which was typically combined with mud clay, became buried behind thick layers of silt, resulting in high pressure and heat conditions. This allowed organic matter to first transform into kerogen, and then, with more heat supplied over geological time, to liquid or gaseous hydrocarbons.

  • The marine creatures and plants died, and their remains were washed up on the beach.
  • The layers of sand and clay compressed them.
  • When they come into contact with high temperatures and pressure, they are converted into petroleum.
  • A refinery uses a number of operations to remove the petroleum from the crude oil. This is referred to as petroleum refining.

Natural Gas

Natural gas is a kind of fossil fuel. Natural gas, like coal and oil, is formed from plants, animals, and microbes that existed millions of years ago.

There are various hypotheses on how fossil fuels are created. The most widely accepted idea holds that they develop underground under extreme circumstances. Plants, animals, and microbes are progressively buried by layers of soil, silt, and, in certain cases, rock as they decay. Organic stuff gets squeezed over millions of years. As biological stuff penetrates deeper into the Earth’s crust, it faces increasing temperatures.

  • The organic matter’s carbon bonds are broken down as a result of the combination of compression and high temperature. Thermogenic methane—natural gas—is produced as a result of this molecular breakdown. Methane, the most prevalent organic substance on the planet, is composed of carbon and hydrogen (CH4).
  • Natural gas resources are frequently discovered alongside oil deposits. Natural gas resources near the Earth’s surface are typically dwarfed by neighboring oil deposits. Deeper deposits, generated at greater temperatures and pressures, contain more natural gas than oil. Pure natural gas can be found in the deepest reserves.
  • Natural gas, on the other hand, does not have to be created far underground. It can also be produced by methanogens, which are microscopic bacteria. Methanogens may be found in the intestines of animals (including humans) as well as in low-oxygen places near the Earth’s surface. Landfills, for example, contain decaying debris that methanogens degrade into a kind of methane known as biogenic methane. Methanogenesis is the process by which methanogens produce natural gas (methane).
  • Although the vast majority of biogenic methane escapes into the atmosphere, new methods are being developed to capture and recover this potential energy source.
  • Thermogenic methane, which forms deep under the Earth’s surface, may potentially escape into the atmosphere. Some of the gas can ascend through permeable substances, such as porous rock, and evaporate into the atmosphere.
  • Most thermogenic methane that rises to the surface, however, hits geological strata that are too impermeable to allow it to escape. Sedimentary basins are the name given to these geological formations.
  • Most thermogenic methane that rises to the surface, however, hits geological strata that are too impermeable to allow it to escape. Sedimentary basins are the name given to these geological formations.
  • Natural gas reserves are trapped in sedimentary basins.

Advantages of Fossil Fuels

  • Fossil fuels are widely available and very affordable to utilize

Fossil fuels are generally inexpensive, easy to obtain, and create. There was a plentiful supply at first. Furthermore, because fossil fuels have powered our society for the past 250 years, the infrastructure to transport them cheaply already exists.

  • Reliability and Applications

At the moment, fossil fuels are dependable. There are various mining sites and large oil and gas resources, and mining and extraction research is growing quickly, as seen by blasting. In the twentieth century, the primary fuels for producing power were oil, coal, and natural gas, while liquid fuels such as gasoline, petroleum diesel, and kerosene became the driving force behind vehicles, tractors, trains, and aircraft.

  • More convenient to store and travel

Transporting fossil fuels is quite simple. Typically, they are carried by international gas pipeline networks or tankers. Renewable energy sources cannot be efficiently stored. On the other hand, fossil fuels can be kept indefinitely. It is advantageous since we may plan for times when we will require them, such as during the winter.

Disadvantages of Fossil Fuels

  • Fossil fuels are nonrenewable energy sources.

A gallon of oil is gone forever when it is burned. Similarly, these fossil fuels are finite and will ultimately deplete. According to calculations, we have around 100 years of coal use remaining, 50 years of fuel oil, and 50 years of natural gas energy supplies. As a result, this is a major concern for us, our children, and future generations.

  • Fossil fuels harm the environment.

One of the biggest downsides of fossil fuels is their contribution to greenhouse gasses. Coal is the most damaging to the environment because it produces far more toxic combustion products than other fossil fuels. Natural gas, on the other hand, is the most environmentally beneficial fossil fuel since it burns cleaner. It indicates that if we burn natural gas under ideal combustion conditions, there will be very few to no hazardous chemicals.

However, the fundamental truth is that fossil fuels are most likely the primary contributors to global warming, which is a massive fossil fuel disadvantage because it is one of the most serious risks to civilization.

  • The carbon dioxide generated by the combustion of fossil fuels considerably contributes to global warming.

The environmental issues generated by the extraction and burning of fossil fuels are more significant. In a 2018 research, UN climate change scientists warned that if emissions from fossil fuel use are not drastically reduced, the globe faces potentially catastrophic warming.

According to published data coal, oil, and gas accounted for around 84% of global primary energy in 2019. We must drastically reduce this fraction in the next decades by replacing them with low-carbon energy sources. When low-carbon energy sources such as renewables and nuclear energy become more widely available, the world should transition swiftly away from fossil fuels.

  • They can be harmful if used irresponsibly

It is critical to recognize that fossil fuels are not the most harmful energy sources. When compared to nuclear energy, it is evident that nuclear power is far more harmful.

However, if used irresponsibly, they may cause an accident. Natural gas, for example, is a highly flammable energy source, which is both a benefit and a problem. Natural gas is the most often utilized energy source in the EU due to its flammability. However, it is a flammable substance that can cause an explosion. This is the most serious drawback of natural gas.

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Jyoti Bashyal

Jyoti Bashyal, a graduate of the Central Department of Chemistry, is an avid explorer of the molecular realm. Fueled by her fascination with chemical reactions and natural compounds, she navigates her field's complexities with precision and passion. Outside the lab, Jyoti is dedicated to making science accessible to all. She aspires to deepen audiences' understanding of the wonders of various scientific subjects and their impact on the world by sharing them with a wide range of readers through her writing.

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