Energy from the Past
Fossil fuels are natural fuels formed from the remains of ancient living organisms. They are the world's dominant energy source but are non-renewable and have significant environmental impacts.
The three main types are:
1.Coal: A solid fuel formed primarily from the remains of land plants (trees, ferns) that were buried in swampy environments hundreds of millions of years ago. Intense heat and pressure over time transformed the plant matter into coal.
2.Petroleum (Crude Oil): A liquid fuel formed from the remains of marine microorganisms (plankton, algae) that were buried under ocean sediments. Heat and pressure transformed their organic matter into oil.
3.Natural Gas: A gaseous fuel, primarily composed of methane (CH₄). It is often found alongside petroleum deposits, as it is formed under similar conditions but at higher temperatures.
Combustion
Fossil fuels release their energy through combustion, which is a rapid reaction between a substance with an oxidant, usually oxygen, to produce heat and light.
For a hydrocarbon like methane, complete combustion produces only carbon dioxide and water:
CH₄ + 2O₂ → CO₂ + 2H₂O + Energy
If there is insufficient oxygen, incomplete combustion occurs, which can produce harmful byproducts like carbon monoxide (CO) and soot (pure carbon).
Environmental Impacts
The Greenhouse Effect: The combustion of all fossil fuels releases carbon dioxide (CO₂), a greenhouse gas. Greenhouse gases trap heat in the Earth's atmosphere, leading to a gradual increase in the planet's average temperature, known as global warming, which in turn drives climate change.
Acid Rain: The burning of coal, in particular, can release sulfur dioxide (SO₂) and nitrogen oxides (NOx) into the atmosphere. These gases react with water vapor to form sulfuric acid and nitric acid, which then fall back to Earth as acid rain. Acid rain can damage forests, acidify lakes and streams, and corrode buildings.