A transport company is considering switching its lorry fleet from diesel fuel to hydrogen fuel. Explain why burning hydrogen in an engine is considered more environmentally friendly than burning diesel fuel.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Diesel fuel is a hydrocarbon mixture derived from crude oil. Hydrogen can be produced from water using renewable energy and produces no carbon dioxide when it burns. However, if hydrogen is produced using fossil fuels, it still has an environmental impact.
Model answer (5 marks)
1. Burning diesel releases CO₂, a greenhouse gas that contributes to climate change.
2. The combustion of hydrogen gives only H₂O as a product, so no CO₂ is emitted.
3. Diesel combustion also produces CO and soot, which are toxic and harmful to health.
4. Hydrogen combustion does not form CO or particulates, so no toxic by‑products are released.
5. If the hydrogen is produced using renewable energy, the whole process uses no fossil fuels and adds no net CO₂ to the atmosphere, making it sustainable.
2. The combustion of hydrogen gives only H₂O as a product, so no CO₂ is emitted.
3. Diesel combustion also produces CO and soot, which are toxic and harmful to health.
4. Hydrogen combustion does not form CO or particulates, so no toxic by‑products are released.
5. If the hydrogen is produced using renewable energy, the whole process uses no fossil fuels and adds no net CO₂ to the atmosphere, making it sustainable.
Examiner tips
- Use the exact terms ‘CO₂’, ‘H₂O’, ‘CO’, ‘soot’, and ‘renewable energy’.
- Show the link between each point and the environmental benefit.
- Keep each point brief and to the point.
Common mistakes
- Confusing CO₂ with CO or soot; listing only CO₂ as the harmful product.
- Failing to mention that hydrogen combustion produces no CO or particulates.
Mark scheme (5 marks)
- Burning diesel produces carbon dioxide (a greenhouse gas), which contributes to climate change / global warming
- Burning hydrogen produces only water (as the only product of combustion)
- Burning diesel/hydrocarbons can also produce carbon monoxide, which is a toxic gas
- Hydrogen fuel does not produce carbon monoxide (or soot/particulates), so no toxic/harmful combustion products are released
- If hydrogen is made using renewable energy, the overall process does not deplete/use up fossil fuels and/or does not add net CO₂ to the atmosphere (sustainable / renewable source)
Related
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