Fossil Fuels: Types, Carbon Dioxide Emissions, and Environmental Trade-offs
Fossil fuels
Fossil fuels are ancient energy sources formed over millions of years from the remains of plants and animals exposed to heat and pressure beneath Earth's surface
They are categorized into three main types:
Coal
Coal
Coal is a solid fossil fuel primarily composed of carbon, along with smaller amounts of hydrogen, sulfur, oxygen, and nitrogen.
- It forms from the compacted remains of ancient vegetation in swampy environments.
- Coal is classified based on its carbon content and energy density into four types: lignite, sub-bituminous, bituminous, and anthracite.
- Anthracite, the highest-grade coal, has the greatest carbon content and energy output.
- Primary Use: Generating electricity in power plants.
- Combustion Products: Carbon dioxide (CO₂), sulfur dioxide (SO₂), and particulate matter.
Crude Oil
Crude oil
Crude oil, or petroleum, is a liquid mixture of hydrocarbons formed from marine organisms.
Extracted from underground reservoirs, it is refined into products such as gasoline, diesel, and jet fuel.
- Primary Use: Transportation fuels, heating, and as a raw material for petrochemicals.
- Combustion Products: CO₂, nitrogen oxides (NOₓ), and unburned hydrocarbons.
Natural Gas
Natural gas
Natural gas is a gaseous fossil fuel composed mainly of methane (CH₄), with smaller amounts of ethane, propane, and other hydrocarbons.
It is often found alongside crude oil deposits and is considered a cleaner-burning fuel.
- Primary Use: Heating, electricity generation, and as a cleaner alternative to gasoline in vehicles.
- Combustion Products: CO₂ and water vapor (H₂O).
Natural gas produces less CO₂ per unit of energy compared to coal or oil, making it the "cleanest" fossil fuel in terms of emissions.
Carbon Dioxide Emissions and Their Environmental Impact
Burning fossil fuels releases the stored energy within their chemical bonds, but it also produces CO₂, a greenhouse gas that traps heat within Earth’s atmosphere.
CO₂ Emissions per Unit of Fuel
- The carbon content of a fuel determines the amount of CO₂ released during combustion.
- Below is a comparison of CO₂ emissions for coal, crude oil, and natural gas:
- Coal: The highest emitter of CO₂ due to its high carbon-to-hydrogen ratio.
- Crude Oil: Emits less CO₂ than coal but more than natural gas.
- Natural Gas: Emits the least CO₂ because methane has a higher hydrogen-to-carbon ratio.
For example, burning 1 tonne of coal (24 GJ of energy) releases approximately 2.26 tonnes of CO₂, while burning 1 tonne of natural gas (55 GJ of energy) releases only 1.23 tonnes of CO₂.
