Fuels

Understanding Fuels

  • Fuels are substances that can be burned to release energy.
  • They usually consist of carbon and hydrogen atoms in the form of hydrocarbons, though they can also contain oxygen, nitrogen, and sulphur elements.
  • The energy released can be used to generate heat, produce electricity or move vehicles.

Classification of Fuels

  • Primary fuels are those that can be used directly. For example, wood, coal, natural gas and oil.
  • Secondary fuels are those derived from primary fuels like electricity and hydrogen gas.
  • Fossil fuels include coal, gas, and oil, and they are non-renewable, meaning they take millions of years to form and cannot be replaced once they are used.
  • Biofuels are made from biomass materials and are considered renewable as new crops can be grown in a short period.

Combustion of Fuels

  • Combustion is a chemical reaction between a fuel and an oxidant, typically the oxygen in air, which is exothermic so it releases heat.
  • In complete combustion, the fuel is fully oxidised, releasing maximum energy and producing carbon dioxide and water vapour.
  • Incomplete combustion occurs when the supply of oxygen is limited, producing carbon monoxide or soot (carbon) and water, and less energy is released.

Fuels and The Environment

  • Burning of fossil fuels releases carbon dioxide, a greenhouse gas which contributes to global warming.
  • Other emission products like sulphur dioxide and nitrogen oxides can cause acid rain, damaging buildings and affecting ecosystems.
  • Modern fuels are designed to burn more cleanly, producing fewer emissions and reducing environmental impact.

Alternative and Future Fuels

  • Hydrogen can be used as a clean fuel, producing only water when it burns, but it is difficult to store and transport.
  • Electricity generated renewably can be used to power electric vehicles, though range and charging times are currently limiting factors.
  • Biofuels, including ethanol and biodiesel, provide a renewable and potentially carbon-neutral source of energy but their production requires significant land use.