Explain why a life cycle assessment (LCA) is not a purely objective process.

AQA GCSE Chemistry (8462) — 4.10.1 Using the Earth's resources and obtaining potable water · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

A life cycle assessment is not purely objective because:
1. Numerical values for pollutant effects cannot be assigned unambiguously – different methods give different results.
2. The choice of impact categories and weighting involves value judgements.
3. LCAs can be abbreviated or selective, omitting stages or data.
4. Such selective LCAs are often used for marketing, presenting a product as greener than it really is.

Examiner tips

  • Use the four points in the order given; include the example of advertising misuse.
  • Show awareness that value judgements and data selection bias the results.
  • Keep each point concise and use exam‑style terminology.
  • Mention that LCAs can be incomplete or manipulated.

Common mistakes

  • Assuming LCAs are always comprehensive and unbiased.
  • Failing to mention the need for value judgements in weighting impacts.
  • Over‑expanding the answer with irrelevant detail.

Mark scheme (4 marks)

  1. Allocating numerical values to pollutant effects is not straightforward
  2. Value judgements are required (when assessing pollutant effects)
  3. Selective or abbreviated LCAs can be misused
  4. For example, selective LCAs can be used for advertising purposes (to make a product appear more environmentally friendly than it is)

Key terms in this question

life cycle assessment

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