Fossil fuels refer to a group of fuels that originate from organic waste. The dictionary definition states that it is "Any preserved evidence of life from a past geological age." It is a common misconception that fossil fuels emerged during the era of the dinosaurs, the Mesozoic era - these fuels were formed millions of years before the dinosaurs.
We can divide fossil fuels into three categories: coal, oil and natural gas. They are also known as hydrocarbons due to their high percentage of hydrogen and carbon, for example, various forms of coal have chemical formulae such as C137H97O9NS and C240H90O4NS.
Origin of Oil and Natural Gas
Oil, also known as ‘crude oil' or just ‘crude' occurs naturally along with gas in varying proportions to each other. The story of the creation of oil and natural gas is interesting. About 300 million years ago, no highly-evolved animal species were living on the earth. Along with primitive life forms, there existed different forms of plants as well. The surface of the earth was covered with swamps and bogs where these plants grew.
In the sea, tiny creatures called ‘diatoms' existed which had the capacity of converting sunlight into stored energy as the way plants do. When they died, they sank to the bottom of the ocean and got buried in the layers of sand and rock. Over a period, the rock exerted pressure on the diatoms, and this process also resulted in the generation of heat, and the decomposed matter of these creatures got converted into oil.
Over a period of millions of years, the oil that got formed remained buried underground due to the formation of multiple layers of soil and rock above them that accumulated in the seas and on land in areas where the sea dried up. In some places, the oil found its way upwards to the earth's crust and seeped out to the surface forming ‘seeps' which led to the first discovery of oil. Rock formations known as ‘caprocks’ kept the remaining oil beneath the surface.
Due to the cooking process of the decomposed diatoms, some of the material got cooked for a longer period, which resulted in the vaporization of a portion of the oil to form natural gas. Natural gas is primarily composed of methane (CH4) and burns completely with no ash formation, so it is the preferred, pollution-free form of fossil fuel. A major issue about natural gas, however, is the sulfur content. Sulfur present in natural gas can lead to the formation of noxious gases like sulfur dioxide (SO2) and sulfur trioxide (SO3). There is a lot of research going on to reduce the sulfur content in natural gas.
Creation of Coal
The story of coal is similar to that of oil and natural gas but with some differences. During the Mesozoic era, the primitive plants and trees that existed finally died and fell into the oceans and swamps. Ultimately, the oceans dried up in several places and this flora got covered in layers and layers of sand, soil and rock in the millions of years that followed. As the layers got added onto the decomposed matter, a spongy substance known as peat got formed. Due to the extremely high pressure exerted on the peat layer by the earth, the result was the formation of coal. Today peat occurs in several regions of the world where they use it as a source of fuel.
Types of Coal
There are four broad categories of coal, anthracite, bituminous, sub-bituminous, and lignite.
- Lignite: Most of the world's coal reserves is made up of lignite. It is soft with a brownish-black color and is considered to be the lowest level of the family. You can see some traces of the original wood in lignite. It can be found abundantly on the western banks of the Mississippi River in the United States.
- Subbituminous: Subbituminous coal is a purer form of coal, dull black and provides comparatively more energy on burning than lignite. It occurs in Montana, Wyoming and a few other states in the US.
- Bituminous: Also known as ‘soft coal,' bituminous coal, provide more energy and is sometimes called "soft coal." It gets its name from the high tar content that it contains, also known as ‘bitumen.' It is mined east of the Mississippi River and in the regions of Ohio and Illinois and the Appalachian mountain range from Kentucky to Pennsylvania in the United States.
- Anthracite: This is a highly dense form of coal, shiny-black, almost metallic in appearance. It is known for generating the highest amount of energy on burning. It does not occur in abundance in the United States and is only present in Pennsylvania. The countries which have the largest reserves of anthracite are Russia, China, and Ukraine.
The Future of Fossil Fuels
Although a primary source of energy throughout the world, burning fossil fuels is blamed for damaging the ozone layer and creating global warming, resulting in the ‘greenhouse effect.' We also have to consider that there is only a fixed quantity of fossil fuels available in the world. The ever-increasing demand for energy has resulted in rapid consumption, but they will not last forever. On the depletion of fossil fuels, they cannot be replaced.
All this has led to a lot of research in alternative energy sources, such as wind power, solar power and even energy from ocean waves. Today solar energy usage has become highly-developed and is used extensively for powering devices in outer space. Several major automobile manufacturers like Tesla, BMW, and Mercedes-Benz, have produced electric cars to reduce the use of fossil fuels.
The story of fossil fuels is indeed an interesting one. However, it is not a never-ending story. Although it has taken millions of years to create them, at the rate that we are consuming them throughout the world, they may not last for more than another hundred years or so. With such an incredible history, the least that we could do is to make a concerted attempt to preserve the rich heritage that we have. Every little bit counts!