A life cycle assessment weighs a product's impact from cradle to grave
Definition
Environmental impact
A change to the environment caused by a product, process or activity, such as resource depletion, pollution or waste production.
Definition
Raw material
A natural material used to make a product, such as crude oil for plastic or wood for paper.
- A life cycle assessment (LCA) works out the environmental impact of a product across its whole life.
- It follows the product from the raw materials it is made from through to its disposal.
- This lets you compare two products fairly instead of judging only the finished item.
Key Idea
- An LCA looks at the whole life of a product, not just how it is used.
- It considers the resources, energy, water and waste involved at every stage.
The four stages of a life cycle assessment
- Extracting and processing the raw materials, which can use large amounts of energy and cause pollution.
- Manufacturing and packaging the product.
- Using the product during its lifetime, including any energy, water or materials it needs to run.
- Disposing of the product at the end of its life, for example in landfill or by recycling.
- Transport and distribution are included at each stage, because moving materials and products also has an impact.
Example
- Making a plastic bag uses crude oil, while making a paper bag uses trees and a lot of water.
- A fair comparison follows both bags through all four stages, not just how many times each is used.
Some impacts can be measured, others need a judgement
Definition
Objective
Based on evidence and measurements rather than personal opinions or preferences.
Definition
Value judgement
A decision based partly on what a person or organisation considers more important, rather than on measurement alone.
Definition
Pollutant
A substance released into the environment that can cause harm.
- The use of water, resources and energy, and the amount of waste produced, can be given fairly reliable numbers.
- The effect of a pollutant is much harder to put a number on.
- Deciding how serious each pollutant is requires a value judgement, not just a measurement.
- Because of this, an LCA is not a fully objective process.
Common Mistake
- Do not treat every figure in an LCA as a hard fact.
- The parts that rely on value judgements, such as how harmful a pollutant is, can differ between people.
Comparing two products fairly
- A comparative LCA puts two products side by side across the same four stages.
- Use the quantified data, such as energy used or waste produced, to support each comparison.
- State clearly which parts of the comparison rest on value judgements rather than measurement.
Exam technique
- When you compare products, compare the same stages for each and back up the comparison with figures from the data.
- Say which impacts are measured and which depend on a value judgement, so your answer shows the LCA is not fully objective.
Selective assessments can mislead
- A selective or abbreviated LCA leaves out some stages of the product's life.
- This can be misused to make a product look greener than it really is, for example in advertising.
- Always check that an assessment covers every stage before you trust its conclusion.
Self review
- What are the four main stages considered in a life cycle assessment?
- Why is transport included in an LCA?
- Which parts of an LCA can be given reliable numbers, and which need value judgements?
- Why is an LCA not a fully objective process?
- How could a selective LCA be misused in advertising?
