Biofuel

Summary: A fuel produced from renewable biological sources, such as plants or animal waste. Tags: igcse chemistry definition organic-chem environmental-chem Created: 2026-07-14 Last Updated: 2026-07-14

Biofuel is a fuel produced from renewable biological materials — including plants, algae, and animal waste — rather than from finite geological reserves of fossil fuels. The three main types studied at IGCSE are: bioethanol, produced by yeast fermentation of sugars from crops such as sugarcane or corn (C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂); biodiesel, manufactured from vegetable oils or animal fats through a transesterification reaction with methanol; and biogas, a mixture of mainly methane and carbon dioxide generated by the anaerobic bacterial digestion of organic waste. Biofuels are often described as carbon-neutral in principle because the carbon dioxide released when they are burned was recently absorbed from the atmosphere by photosynthesis during the growth of the source plants, creating a short-term carbon cycle rather than releasing carbon sequestered underground for millions of years. However, this picture is complicated by the fossil fuel energy often used in growing, harvesting, transporting, and processing biofuel crops, as well as by the ethical concern that land used for biofuel crops may compete with land needed for food production. For IGCSE exams, students should be able to discuss both the advantages (renewable, carbon-neutral, reduces dependence on fossil fuels, uses waste materials in the case of biogas) and the disadvantages (competition with food crops, deforestation for plantations, energy-intensive processing) of biofuels.

Key term — IGCSE Chemistry (0620/0971) glossary.