How do we assess the environmental impact of products and reduce the use of resources?
Life cycle assessments; the four stages and their environmental impacts; reducing, reusing and recycling; and the benefits of recycling metals and other materials.
A focused answer to AQA GCSE Chemistry 4.10.2, covering life cycle assessments and their four stages, the environmental impacts considered, and how reducing, reusing and recycling conserve resources and energy.
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What this dot point is asking
AQA wants you to describe a life cycle assessment and its stages, explain the environmental impacts it considers, evaluate why some parts are difficult to measure, and explain how reducing, reusing and recycling conserve resources and energy. The evaluation point, that LCAs involve value judgements and can be biased, is a common higher-mark requirement.
Life cycle assessment
The four stages
At each stage it considers the use of energy, water and natural resources and the production of waste and pollutants, including carbon dioxide and other greenhouse gases.
Limitations of LCAs
Some impacts, such as the effects of particular pollutants, are difficult to measure and rely on value judgements, so different people may reach different conclusions about which product is better. LCAs can therefore be biased, for example if a selective or incomplete version is used in advertising to make a product look greener than it is. A genuine LCA should consider all four stages fairly.
Reduce, reuse and recycle
Recycling metals saves a lot of energy and resources because it avoids extracting metal from its ore, which is energy-intensive (especially electrolysis for reactive metals such as aluminium). Metals are sorted, melted and recast; glass can be reshaped or crushed and remelted. Recycling reduces the use of finite resources and cuts the waste sent to landfill.
Why the order reduce, reuse, recycle matters
The three options are usually listed in order of how much they help the environment. Reducing the amount of material used in the first place is best, because it avoids the energy and resources of making and disposing of the material at all. Reusing comes next, because using the same item again avoids the energy of processing it into something new. Recycling is third, because although it conserves the raw material, it still uses energy to collect, sort, melt and reform the material; even so, recycling almost always uses far less energy than extracting and processing virgin material. Together these three approaches conserve finite resources, cut energy use and the associated carbon dioxide, and reduce the waste that would otherwise go to landfill.
Try this
Q1. State the four stages considered in a life cycle assessment. [2 marks]
- Cue. Raw materials, manufacturing, use, and disposal.
Q2. Explain why recycling metals saves energy. [2 marks]
- Cue. It avoids extracting the metal from its ore, which uses a lot of energy.
Q3. State one reason an LCA might be biased. [1 mark]
- Cue. Some impacts involve value judgements, or it may be used selectively in advertising.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20194 marksA life cycle assessment (LCA) is carried out to compare a plastic bag with a paper bag. Describe the four stages an LCA considers, and explain why some parts of an LCA are difficult to carry out objectively.Show worked answer →
A 4-mark Paper 2 question on LCAs.
Four stages (2 marks): extracting and processing the raw materials; manufacturing and packaging; using the product during its lifetime; disposal at the end of its life (including transport throughout). At each stage the use of energy, water and resources and the production of waste and pollutants is considered. Difficult to be objective (2 marks): some impacts, such as the effect of pollutants, are hard to measure and rely on value judgements, so different people may weigh them differently; LCAs can therefore be biased, for example if produced selectively to support advertising.
Markers reward the four stages and a clear explanation of why LCAs involve value judgements and possible bias.
AQA 20213 marksExplain how recycling aluminium drinks cans conserves resources and saves energy, and describe the difference between reusing and recycling a product.Show worked answer →
A 3-mark question on recycling and reuse.
Recycling aluminium (2 marks): it avoids extracting aluminium from its ore by electrolysis, which uses very large amounts of energy; it also conserves the finite ore (bauxite) and reduces waste sent to landfill. Reuse versus recycle (1 mark): reusing means using the same product again as it is (for example refilling a bottle), while recycling means processing the used material into a new product (melting the metal and recasting it).
Markers reward the avoided-extraction-energy point and a clear reuse-versus-recycle distinction.
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Sources & how we know this
- AQA GCSE Chemistry (8462) specification — AQA (2016)