Fossil fuel is a general term for buried combustible geologic deposits of organic materials, formed from decayed plants and animals that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the earth’s crust over hundreds of millions of years. Because of the immense time spans to create coal, oil and natural gas, they are classed as non-renewable sources of energy.
These are hydrocarbons; primarily coal, fuel oil or natural gas. All three were formed many hundreds of millions of years ago before the time of the dinosaurs, which is why we call them ‘fossil fuels’. The age they were formed is called the Carboniferous Period and it was part of the Palaeozoic Era. “Carboniferous” gets its name from carbon, the basic element in coal. These raw forms of energy take millions of years to make. By producing electricity from coal, and using oil for transport, we are using up the material that was made more than 300 million years ago before the time of the dinosaurs.
The Carboniferous Period occurred from about 360 to 286 million years ago. At the time, the land was covered with swamps filled with huge trees, ferns and other large leafy plants. The water and seas were filled with algae, the green stuff that forms on a stagnant pool of water. Algae are actually millions of very small plants. As the trees and plants died, they sank to the bottom of the swamps of oceans. They formed layers of a spongy material called peat. Over many hundreds of years, sand and clay and other minerals, which turned into a type of rock called sedimentary, covered the peat.
Layer upon layer piled on top of more rock, weighing heavier and heavier, pressing down on the peat. The peat was squeezed and squeezed until the water came out of it and it eventually, over millions of years, it turned into coal, oil or natural gas.
The utilisation of these carbon based fuels has enabled large-scale industrial development and largely supplanted water-driven mills, as well as the combustion of wood or peat for heat. When generating electricity, energy from the combustion of fossil fuels is often used to power a turbine. Older generators often used steam generated by the burning of the fuel to turn the turbine, but in newer power plants the gases produced by burning of the fuel turn a gas turbine directly.
With global modernisation in the 20th and 21st centuries, the thirst for energy from fossil fuels, especially gasoline derived from oil, is one of the causes of major regional and global conflicts. A global move toward the generation of renewable energy could assist in resolving some of these conflicts as well as meeting our increased global energy needs.
The burning of fossil fuels by humans is the largest source of emissions of carbon dioxide, which is one of the greenhouse gases causing radiative forcing and contributes to global warming. The rise in concentration of the greenhouse gas CO2 is trapping more solar heat and the average surface temperature of the Earth is rising in response. Currently these ancient fuels provide more than 85% of all the energy consumed globally, nearly two-thirds for electricity, and virtually all transportation fuels. Even the recent development of hydrogen fuel cells generally rely on fossil fuels to extract hydrogen to power hydrogen cars.
Unfortunately, it is likely that reliance on coal, oil and gas to power expanding global economies (particularly China and India) will actually increase over at least the next few decades even with aggressive development and deployment of new renewable and nuclear technologies.
