A LIFE CYCLE ASSESSMENT (LCA) evaluates the TOTAL ENVIRONMENTAL IMPACT of a product through ALL stages of its life — from raw material extraction to disposal.
Also called a 'cradle-to-grave' assessment.
The FOUR STAGES assessed:
1. EXTRACTING AND PROCESSING RAW MATERIALS — mining, farming, quarrying.
2. MANUFACTURING AND PACKAGING — energy and materials used in production.
3. USE — energy, water and other resources used during the product's lifetime.
LCAs assess the ENVIRONMENTAL COSTS at each stage:
Energy consumption.
Water use.
Greenhouse gas emissions (carbon footprint).
Waste produced.
Pollution to air, water and land.
Resource depletion.
Using LCA to Compare Products
LCAs allow comparison of ALTERNATIVES — e.g. plastic bags vs paper bags vs cotton tote bags.
EXAMPLE — Carrier bags:
PLASTIC BAG: uses petroleum (non-renewable), manufactured quickly, lightweight (low transport emissions), lasts for years if reused, takes ~450 years to degrade in landfill.
PAPER BAG: uses trees (renewable if sustainably managed), more energy to manufacture, heavier (more transport emissions), biodegrades quickly.
COTTON TOTE: very high energy and water use to grow cotton and manufacture, must be reused MANY times to offset its higher manufacturing impact — but durable.
The LCA shows that 'eco-friendly' is complex:
Paper bags are NOT always better than plastic if manufacturing emissions are included.
Cotton bags need to be reused hundreds of times to have lower impact than plastic.
SUBJECTIVITY IN LCAs:
Not all impacts are easy to quantify (e.g. harm to wildlife from plastic litter).
Different LCAs can reach different conclusions depending on which factors are weighted.
Some factors are difficult to compare (e.g. CO₂ vs water use vs land use).
Limitations and Uses of LCAs
LIMITATIONS:
COMPLEXITY — gathering data for all stages is difficult and time-consuming.
SUBJECTIVITY — different analysts may weight factors differently.
VARIABLE DATA — energy sources differ by country (renewable vs coal), changing outcomes.
NOT ALL IMPACTS QUANTIFIABLE — e.g. harm to ecosystems, aesthetic impacts.
POSSIBLE BIAS — companies may commission LCAs that present their products favourably.
USES:
HELP CONSUMERS choose more sustainable products.
GUIDE MANUFACTURERS to redesign products for lower environmental impact.
INFORM POLICY — governments use LCAs to set regulations (e.g. minimum recycled content).
IDENTIFY 'HOT SPOTS' — stages with the highest environmental impact → target improvements.
GREEN CHEMISTRY uses LCA principles — designing reactions and products with:
Lower energy consumption.
Fewer toxic by-products.
Renewable feedstocks.
Higher atom economy (less waste).
⚠️ Common Mistake
LCAs can be SUBJECTIVE — they depend on which factors are included and how they are weighted. A company-funded LCA might not include all negative impacts. Always consider who has commissioned the LCA and whether all stages and impacts are genuinely included. An LCA showing a product is 'green' in one respect might not account for harms in another.
📌 Key Note
LCA: evaluates environmental impact across all life stages — raw materials, manufacturing, use, disposal. Assesses energy, water, emissions, waste at each stage. Used to compare products — but results can be subjective. Cradle-to-grave analysis. Cotton bags need many reuses to offset high manufacturing impact.
🎯 Matching Activity — LCA Stages
Match each stage of an LCA to what it includes. — drag the symbols on the right to match the component names on the left.
Extracting raw materials
Drop here
Manufacturing
Drop here
Use phase
Drop here
Disposal
Drop here
Mining, quarrying or farming — energy and land use to obtain starting materials
Energy and water consumed during the product's working lifetime
Whether the product goes to landfill, is recycled, incinerated or composted
Energy and resources used to make and package the product
⭐ Higher Tier Only
Carry out comparative LCA analysis. Identify and evaluate relative environmental impacts at each stage. Recognise subjectivity — different analysts, different weightings. Understand how LCA informs green chemistry and drives product redesign. Evaluate limitations of LCAs.
🎯 Test Yourself
Question 1 of 2
1. A cotton tote bag has a higher environmental impact at the manufacturing stage than a plastic bag. How many uses would the cotton bag need to have a lower overall LCA impact?
2. Why might two different LCAs of the same product reach different conclusions?
⭐ How Well Do You Understand This Topic?
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