Life Cycle Assessment and Recycling

Every product we use — a plastic bottle, a paper bag, a car — has an environmental cost, but that cost is not only the pollution made when the product is thrown away. It includes the energy and resources used to dig up the raw materials, to manufacture and transport the product, and to run it during its life. A life cycle assessment (LCA) is a careful way of adding up all of these impacts across a product's whole life, so that two products can be compared fairly. This lesson, part of Topic C6 of OCR Gateway Science A, explains the four stages of an LCA, how to interpret and compare them, why parts of an LCA are a matter of judgement, and how recycling reduces environmental impact.

By the end of this lesson you should be able to describe the four stages of a life cycle assessment, interpret and compare LCAs of different products, explain why an LCA is not wholly objective and can be biased, and explain the benefits of recycling and reuse.

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What a Life Cycle Assessment Is

A life cycle assessment (LCA) works out the environmental impact of a product across its whole life — from obtaining the raw materials, through manufacturing and use, to disposal at the end. The point is to capture all of the impacts, not just the obvious ones, so that sensible decisions can be made about which product or material is better for the environment.

An LCA considers, at every stage, the use of:

• resources (raw materials and land);
• energy;
• water;

and the release of waste and pollutants (including greenhouse gases) into the air, water and land. Crucially, transport is included at every stage, because moving materials and products around uses energy and produces pollution.

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The Four Stages of an LCA

An LCA is usually broken down into four stages, which together cover the product's whole life:

flowchart LR
  A["1. Raw materials\nextracting & processing"] --> B["2. Manufacturing\n& packaging"]
  B --> C["3. Using\nthe product"]
  C --> D["4. Disposal\nlandfill / recycling"]
  A -.transport.-> B
  B -.transport.-> C
  C -.transport.-> D

Stage	What is assessed
1. Raw materials	Extracting and processing the raw materials — mining, quarrying, growing crops; the energy, water and resources used, and the pollution and land damage caused
2. Manufacturing & packaging	Making the product and its packaging — energy and water used, waste and pollutants produced
3. Using the product	The impact while the product is in use — for example fuel burned by a car, or detergent and energy used by a washing machine; how long it lasts
4. Disposal	What happens at the end of life — landfill, incineration or recycling; the pollutants released and whether materials can be recovered

Transport between and within these stages is added in throughout, because every journey uses energy and releases pollution.

Exam Tip: Learn the four stages in order: raw materials → manufacture (and packaging) → use → disposal, with transport at every stage. A frequent mistake is to think an LCA looks only at manufacturing — it covers the whole life.

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Worked Example — Reading an LCA

LCAs are often shown as a table comparing two products. Here is a simplified (illustrative) comparison of a single-use plastic bag and a paper bag:

Impact	Plastic bag	Paper bag
Raw materials	Crude oil (finite)	Trees (can be replanted)
Energy to manufacture	Lower	Higher
Water used in manufacture	Lower	Higher
Waste at disposal	Slow to break down; can harm wildlife	Breaks down more easily
Reuse possible?	Can be reused several times	Tears easily; fewer reuses

Use the table to decide which bag has the higher impact at the manufacturing stage, and explain why a simple "plastic is worse" conclusion may be too quick.

Step 1 — read the manufacturing row: the paper bag uses more energy and water to manufacture than the plastic bag, so at that stage the paper bag has the higher impact.

Step 2 — look across the whole life: the plastic bag is made from finite crude oil and is slow to break down at disposal, which counts against it, but it can be reused several times, which spreads its impact. The paper bag uses more energy and water to make, but breaks down more easily.

Step 3 — conclude: which bag is "better" depends on how many times each is used and on how the impacts are weighted — there is no single obvious winner, which is why a careful LCA is needed rather than a snap judgement.

Answer: the paper bag has the higher impact at the manufacturing stage (more energy and water); but a fair comparison must weigh all stages, including raw materials, reuse and disposal, before deciding overall.

Exam Tip: When you interpret an LCA, name the stage with the highest impact and use the figures in the table to justify it. If asked which product is "better overall", note that it depends on weighting all the stages — don't just pick one row.

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Why an LCA Is Not Wholly Objective

You might expect an LCA to give one clear, objective number, but it does not. While some parts can be measured (such as the energy used or the mass of carbon dioxide released), the effect of some pollutants is a matter of judgement — deciding how "bad" a particular pollutant is, or how to compare water pollution against air pollution, involves a value judgement that is subjective.

Because parts of an LCA rely on judgement, an LCA is not completely objective, and this opens the door to bias. An LCA can be made selective — choosing which impacts to include or emphasise — to make a product look more environmentally friendly than it really is. This is a particular risk when an LCA (or a shortened version of one) is used in advertising: a company may present a selective LCA to support a marketing claim, so the results should be treated with care.

Exam Tip: Two marks examiners look for here: (1) the effect of some pollutants is a value judgement, so an LCA is not wholly objective; and (2) LCAs can be made selective or biased, especially in advertising, so their conclusions are not always reliable.

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Recycling and Reuse

At the disposal stage, the most sustainable options are to reuse or recycle materials rather than send them to landfill. Reusing means using a product again for the same or a different purpose without reprocessing it (for example, refilling a glass bottle). Recycling means processing a used material so that it can be made into a new product (for example, melting down metal or glass, or reprocessing some plastics).

The benefits of recycling are that it:

• conserves finite resources (such as metal ores and crude oil), making them last longer;
• saves energy — making a product from recycled material usually uses less energy than making it from raw materials;
• reduces waste sent to landfill;
• reduces quarrying and mining, and so reduces the landscape damage they cause.

Recycling does have an energy cost of its own — used materials must be collected, sorted and reprocessed — but for most materials this is still far less than the energy needed to extract and process the raw materials from scratch. Reusing is usually even better than recycling, because it needs little or no reprocessing.