Life Cycle Assessments

Every product we use has an environmental impact — from the moment raw materials are extracted from the Earth, through manufacturing and use, to the product's eventual disposal. A life cycle assessment (LCA) is a tool that quantifies this impact at every stage. This lesson covers LCAs as required by the AQA GCSE Chemistry specification.

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What Is a Life Cycle Assessment?

A life cycle assessment (LCA) is a systematic analysis of the environmental impact of a product throughout its entire life — from raw material extraction to disposal. It is sometimes called a "cradle-to-grave" analysis.

An LCA examines four key stages:

graph LR
    A["1. Raw Material<br>Extraction"] --> B["2. Manufacturing<br>and Processing"]
    B --> C["3. Use and<br>Operation"]
    C --> D["4. Disposal at<br>End of Life"]
    style A fill:#ffcc80,stroke:#e65100
    style B fill:#fff59d,stroke:#f57f17
    style C fill:#a5d6a7,stroke:#2e7d32
    style D fill:#ef9a9a,stroke:#c62828

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The Four Stages of an LCA

Stage 1: Raw Material Extraction

This stage considers the environmental impact of obtaining the raw materials needed to make the product.

Factor	What Is Assessed
Mining and quarrying	Energy used, habitat destruction, landscape damage
Growing crops	Land use, water use, fertiliser and pesticide use
Extracting crude oil	Energy used, risk of oil spills, pollution
Transportation of raw materials	Fuel used, CO2 emissions

Stage 2: Manufacturing and Processing

This stage considers the impact of turning raw materials into the finished product.

Factor	What Is Assessed
Energy consumption	How much energy is needed; what is the energy source?
Water use	Large amounts of water may be needed for cooling or as a solvent
Waste produced	Solid waste, liquid effluent, gaseous emissions
Pollutants released	CO2, SO2, toxic chemicals, particulates

Stage 3: Use and Operation

This stage considers the environmental impact during the product's useful life.

Factor	What Is Assessed
Energy required during use	A car burns fuel; an appliance uses electricity
Resources consumed	Water, fuel, replacement parts
Emissions during use	Exhaust gases, heat, noise
Maintenance requirements	Chemicals needed for cleaning, repainting, etc.

Stage 4: Disposal at End of Life

This stage considers what happens when the product is no longer useful.

Factor	What Is Assessed
Landfill	Space required, potential leaching of toxic chemicals, methane production
Incineration	Energy released (can be used), but CO2 and toxic gases produced
Recycling	Energy saved compared to making new materials, but energy still needed for collection and reprocessing
Biodegradation	Some materials break down naturally; others (e.g. most plastics) persist for centuries

Exam Tip: You must know all four stages and be able to give specific examples of environmental impacts at each stage. Simply naming the stages without explaining what is assessed will not score full marks.

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Example LCA: Comparing Paper Bags and Plastic Bags

LCA Stage	Paper Bag	Plastic Bag
Raw materials	Trees (renewable, but forests may be cleared); water and energy for pulping	Crude oil (finite, non-renewable); energy for extraction and cracking
Manufacturing	Large amounts of water and energy; chemical treatments produce waste	Less energy than paper; fewer chemicals used in production
Use	Can tear when wet; may need more bags per shop	Lightweight, strong, waterproof; can be reused multiple times
Disposal	Biodegradable; can be recycled or composted	Most are not biodegradable; can persist in the environment for hundreds of years; can harm wildlife

This example shows why LCAs are valuable — neither option is clearly "better" overall. Each has advantages and disadvantages at different stages.

Exam Tip: AQA loves to test your ability to evaluate by comparing two products using an LCA framework. Always discuss all four stages and give a balanced conclusion. Avoid one-sided answers.

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Limitations of Life Cycle Assessments

While LCAs are useful, they have significant limitations:

Limitation	Explanation
Difficult to quantify all impacts	Some environmental impacts (e.g. loss of biodiversity, visual pollution) are hard to measure numerically
Subjective judgements	Deciding how to weight different impacts involves value judgements, not just science
Data availability	Companies may not have accurate data for every stage of the life cycle
Bias	LCAs can be manipulated to favour a particular product or conclusion, especially when conducted by the manufacturer
Boundary decisions	Deciding what to include and exclude from the assessment affects the result
Complexity	A full LCA requires specialist expertise and can be very time-consuming

Exam Tip: The AQA specification explicitly states that LCAs have limitations because the allocation of numerical values to some effects is subjective and may be biased by the person or organisation conducting the assessment. This is a key evaluation point that frequently appears in exam questions.

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Selective and Simplified LCAs

Because full LCAs are complex and expensive, many organisations use simplified LCAs that focus on a few key indicators:

Indicator	What It Measures
Carbon footprint	Total greenhouse gas emissions (measured in CO2 equivalents)
Water footprint	Total volume of fresh water used
Energy consumption	Total energy used across all stages

These simplified assessments are easier to conduct but give an incomplete picture of environmental impact.

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Using LCAs to Make Decisions

LCAs can help individuals, companies and governments make more sustainable choices:

Decision Maker	How LCAs Help
Consumers	Choose products with lower environmental impact (e.g. products with "carbon neutral" labels)
Companies	Identify which stage of production causes the most environmental damage and target improvements
Governments	Set environmental standards and regulations; compare policy options

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Summary