How do we judge the environmental impact of a product over its whole life, and why do we recycle materials?
Life cycle assessment (LCA) and its stages, the limitations of LCAs, and the advantages and disadvantages of recycling and reusing materials including metals.
A focused answer to OCR Gateway GCSE Chemistry A topic C6.1 on life cycle assessment and recycling, covering the four stages of an LCA, the limitations and value judgements involved, and the advantages and disadvantages of recycling and reusing materials including metals.
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What this dot point is asking
OCR wants you to describe what a life cycle assessment (LCA) is and its stages, recognise the limitations of LCAs (including the value judgements they involve), and explain the advantages and disadvantages of recycling and reusing materials, including metals. This is about judging the whole environmental impact of products and using resources sustainably.
Life cycle assessment
For example, comparing a plastic bag with a paper bag, an LCA looks at the crude oil or wood used, the energy to manufacture each, how many times each is used, and what happens when each is thrown away.
The limitations of LCAs
Because of these limitations, an LCA gives a useful comparison but should not be treated as a single, certain answer.
Recycling and reusing materials
The advantages of recycling and reusing:
- They conserve limited (finite) raw materials, such as metal ores and crude oil, so these resources last longer.
- They often use much less energy than extracting and processing new materials (recycling a metal usually uses far less energy than extracting it from its ore).
- They reduce the waste sent to landfill and the pollution and damage caused by mining, quarrying and manufacturing.
The disadvantages and limits:
- Recycling costs money and energy to collect, sort and process the used materials.
- Some products are made of mixtures of materials that are difficult and expensive to separate.
- Some materials can only be recycled a limited number of times before their quality falls.
So recycling is usually worthwhile, especially for metals, but it is not free, and the benefits must be weighed against the cost and energy of the recycling itself.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20194 marksA life cycle assessment (LCA) is carried out on a plastic bag and a paper bag. Describe the four main stages that an LCA considers, and explain why an LCA can be difficult to carry out fairly.Show worked answer →
A C6.1 structured question. Reward describing the four stages: (1) obtaining and processing the raw materials (extracting and refining the materials needed); (2) manufacturing the product (and packaging it); (3) using the product during its lifetime (including any energy or materials needed to use and maintain it); and (4) disposing of the product at the end of its life (reusing, recycling or sending to landfill, and the transport involved at each stage). Then explain the difficulty: assessing some impacts requires value judgements rather than measured data (for example how to compare the effect of using water against the effect of producing waste), so different people may reach different conclusions, and some data, especially about use and disposal, is hard to measure accurately. Markers credit the four stages (raw materials, manufacture, use, disposal) and the point that LCAs involve value judgements and uncertain data, so they are not fully objective. A common error is to list only two stages or to forget disposal.
OCR 20224 marksAluminium drinks cans are often recycled rather than made from newly extracted aluminium. Explain two advantages of recycling aluminium rather than extracting it from its ore.Show worked answer →
A C6.1 application question. Reward two advantages, explained: (1) recycling conserves the limited supply of aluminium ore (bauxite), so the finite raw material lasts longer; (2) recycling uses much less energy than extracting aluminium from its ore by electrolysis (which needs large amounts of electrical energy to decompose the molten oxide), so it saves energy and reduces the carbon dioxide emitted from generating that energy. Other valid points: it reduces the amount of waste sent to landfill, reduces the environmental damage of mining and quarrying, and is often cheaper. Markers credit two clear advantages with explanation, for example conserving the limited ore and saving the large amount of energy needed for electrolysis. A common error is to state advantages without explaining why (for example just "saves energy" without linking to the energy cost of electrolysis).
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