Aluminium is one of the most widely used metals in the world, found in products ranging from aircraft bodies to food packaging. Despite being the most abundant metal in the Earth's crust, aluminium was once more valuable than gold. Explain why aluminium is expensive to produce and describe the environmental considerations associated with obtaining aluminium.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Aluminium is the most abundant metal in the Earth's crust, yet it is classified as an expensive metal to produce. It is extracted from bauxite ore by electrolysis rather than by reduction with carbon.
Model answer (5 marks)
Aluminium cannot be extracted by reduction with carbon because it is more reactive than carbon, so the high‑temperature reduction would produce CO and CO₂ instead of aluminium.
Instead, aluminium is produced by the Hall–Héroult electrolytic process, which requires large, continuous amounts of electrical energy; this energy cost dominates the overall production cost.
The ore, bauxite, is mined by open‑pit methods that destroy habitats, reduce biodiversity and leave large scars on the landscape.
The electricity used in the electrolytic cell is often supplied by fossil‑fuel power stations, which emit CO₂ and contribute to climate change.
Recycling aluminium, however, uses only about 5 % of the energy required for primary production, reducing the need for mining and conserving finite ore reserves.
Instead, aluminium is produced by the Hall–Héroult electrolytic process, which requires large, continuous amounts of electrical energy; this energy cost dominates the overall production cost.
The ore, bauxite, is mined by open‑pit methods that destroy habitats, reduce biodiversity and leave large scars on the landscape.
The electricity used in the electrolytic cell is often supplied by fossil‑fuel power stations, which emit CO₂ and contribute to climate change.
Recycling aluminium, however, uses only about 5 % of the energy required for primary production, reducing the need for mining and conserving finite ore reserves.
Examiner tips
- Mention the Hall–Héroult process and its energy demand; link to CO₂ emissions; note the recycling advantage; keep each point brief and use exam terminology.
Common mistakes
- Claiming aluminium can be reduced with carbon; confusing aluminium with aluminium oxide; omitting the recycling benefit.
Mark scheme (5 marks)
- Aluminium cannot be extracted by reduction with carbon / coke because aluminium is more reactive than carbon
- Electrolysis requires large / continuous amounts of electrical energy, making it expensive
- Mining bauxite / aluminium ore destroys habitats / causes loss of biodiversity / scars the landscape
- Generating electricity for electrolysis often involves burning fossil fuels, releasing carbon dioxide / contributing to climate change / global warming
- Recycling aluminium uses much less energy than extracting it from ore / reduces need for mining / conserves finite ore reserves
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