Section 1 of 6Four stages of an LCA
1Raw materials
- Raw materials Extracting and processing resources uses energy, uses up finite ores or crude oil and may damage habitats through mining or deforestation.
2Manufacture
- Manufacture Factories take up land, use energy (often from fossil fuels), and produce waste and pollution.
3Use
- Use Impact depends on the product: a wooden desk has little, a petrol car causes air pollution.
4Disposal
- Disposal Waste fills landfill sites, while recycling or reusing reduces the impact.
Section 2 of 6Measuring an LCA
Easy to quantify
- Easy to quantify The energy used, water consumed, mass of waste and carbon dioxide emitted can all be measured.
Hard to quantify
- Hard to quantify The effect of pollutants on wildlife and people is difficult to turn into a number, so value judgements are made.
Bias
- Bias Different people may weight the same effects differently, so an LCA is not fully objective.
Section 3 of 6Example: shopping bags
| Stage | Plastic (poly(ethene)) bag | Paper bag |
|---|---|---|
| Raw materials | Crude oil: finite, needs energy to process | Trees or recycled paper |
| Manufacture | Fractional distillation, cracking and polymerisation; little waste | Pulping uses much energy and chemicals; makes waste |
| Use | Strong and can be reused many times | Weaker, usually used once |
| Disposal | Can be recycled but is not biodegradable | Biodegrades and can be recycled |
Section 4 of 6Using LCAs sensibly
Evaluating a product
Compromise
- Compromise No product has zero impact, so decisions balance environmental cost against price and performance.
Abbreviated LCAs
- Abbreviated LCAs Short versions may leave out stages and be used in advertising to highlight only the benefits.
Depends on use
- Depends on use A plastic bag reused many times may beat paper, but a plastic bag used once may not.
Draw a conclusion
- Draw a conclusion Use the data, state which option has the lower impact and justify it, mentioning limitations.
Section 5 of 6Key terms
| Term | Meaning |
|---|---|
| Life cycle assessment (LCA) | An analysis of the environmental impact of a product at every stage of its life. |
| Biodegradable | Able to be broken down naturally by microorganisms. |
| Finite resource | A resource that will run out because it cannot be replaced quickly. |
| Landfill | A site where waste is buried. |
| Value judgement | An opinion about how serious an effect is, which may differ between people. |
Section 6 of 6Exam technique
1
Forgetting the use stagefor items such as cars and kettles, most of the impact can occur during use.
2
Presenting an LCA as completely objective. Some stages rely on value judgements.
3
Concluding from one number only. Evaluate all four stages and the way the product is used.
4
Writing that paper is always better because it biodegrades. Making it can use more energy and water.