Life cycle assessment — AQA GCSE Combined Science
Test yourself on Life cycle assessment with AQA GCSE practice questions.
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Life cycle assessment explained
A life cycle assessment (LCA) evaluates a product's environmental impact across four main stages: extracting and processing raw materials, manufacturing and packaging, use and operation during its lifetime, and disposal at the end of its useful life.
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Transport and distribution are considered at each of these stages. At every stage, energy use, resource depletion, waste, and pollution are assessed. For example, a plastic bottle requires crude oil extraction, whereas a glass bottle requires high-temperature melting but can be reused. LCAs are not simply about which material is 'best': the conclusion depends on the data and assumptions used. A fair comparison uses the same functional unit and states the boundaries of the assessment.
extracting and processing raw materials
Every product begins with raw materials taken from the Earth, and this stage of a life cycle assessment (LCA) covers getting them out and turning them into something usable. Extraction includes quarrying limestone, mining metal ores, drilling for crude oil and felling trees. Processing then refines these: crushing and heating limestone for cement, extracting metal from ore by reduction or electrolysis, and fractional distillation plus cracking for crude oil. Both steps use energy, often from burning fossil fuels, and can release pollutants, use water and disturb habitats. For example, making aluminium needs bauxite ore, and electrolysis of purified alumina consumes large amounts of electricity. In an LCA you weigh these impacts against the benefits of the finished material, and compare alternatives fairly by using the same functional unit, such as one kilogram of material.
manufacturing and packaging
After raw materials are extracted and processed, they are manufactured into a product and then packaged. Manufacturing covers shaping, joining, moulding, assembling and finishing, and it usually needs energy for heating, machinery and transport between factories. Packaging protects the product, keeps it clean, provides information and helps it sell, but it also uses materials such as paper, glass, plastic, steel and aluminium. Each packaging material has its own extraction, processing and disposal impacts. For example, glass bottles are heavy, so transporting them uses more fuel, but glass can be recycled many times; plastic film is light but often made from crude oil and may not be recycled. In a life cycle assessment you compare these impacts across the whole life cycle, using the same functional unit, such as one litre of drink delivered to a customer.
use and operation during its lifetime
A life cycle assessment (LCA) tracks a product from raw materials to disposal. The stage 'use and operation during its lifetime' covers everything that happens while the product is actually being used: the energy it consumes, any fuel or electricity it needs, replacement parts, servicing, and the emissions or waste produced during normal working life. For example, a washing machine uses electricity and water for every wash over perhaps ten years, and that ongoing energy use often contributes far more to its total environmental impact than making it did. Students should identify this stage within a full LCA, describe what happens during use, and compare products by asking which uses more energy or resources while operating.
disposal at the end of its useful life, including transport and distribution at each stage.
A life cycle assessment (LCA) covers every stage of a product's existence, and this statement focuses on two parts: disposal at the end of its useful life, and the transport and distribution that occurs at each stage. Disposal means deciding what happens when a product no longer works or is no longer wanted: it may be recycled, sent to landfill, incinerated or reused, and each route has different environmental costs. Transport and distribution must be counted at every stage, because moving raw materials to a factory, finished goods to shops and waste to a disposal site all burn fuel and release emissions. For example, a glass bottle made, filled, delivered and later recycled involves several journeys, and each one adds to its overall impact. Students should describe disposal options and explain why transport at each stage is included in a full LCA.
Use of water, resources, energy sources and production of some wastes can be fairly easily quantified. Allocating numerical values to pollutant effects is less straightforward and requires value judgements, so LCA is not a purely objective process.
A life cycle assessment (LCA) tracks a product from raw materials to disposal. Some inputs and outputs are measurable: the volume of water used, the mass of material extracted, the energy consumed and the mass of waste sent to landfill can all be metered or weighed, so they can be fairly easily quantified. Other impacts resist simple numbers. If a factory releases sulfur dioxide, how many 'harm units' equal one tonne of plastic waste? Deciding that one effect matters more than another is a value judgement, not a measurement. Two assessors can use identical data yet reach different conclusions because they weight pollution, habitat damage and resource depletion differently. LCA therefore combines objective measurements with subjective choices, so it is not a purely objective process.
Selective or abbreviated LCAs can be devised to evaluate a product but these can be misused to reach pre-determined conclusions, eg in support of claims for advertising purposes.
A full life cycle assessment examines extraction, manufacture, transport, use and disposal, which takes time and data. A company may instead carry out a selective or abbreviated LCA: it studies only chosen stages, chosen materials or chosen impacts. This can be legitimate when time or data are limited, and it can still evaluate a product usefully. The danger is misuse. If a firm wants a pre-determined conclusion, it can choose boundaries that flatter its product, for example comparing only the use phase of a reusable bag while ignoring the energy used to make it, or reporting carbon dioxide but omitting water pollution. The resulting figure may be technically correct yet misleading. Advertisers can then present it as proof that a product is 'green'. A critical reader asks what was included, what was left out and who paid for the study.
Students should be able to carry out simple comparative LCAs for shopping bags made from plastic and paper.
A life cycle assessment (LCA) tracks a product through four stages: extracting raw materials, manufacturing, using it, and disposing of it. For shopping bags, compare a plastic bag (made from crude oil, a limited resource) with a paper bag (made from wood, a renewable resource if replanted). Judge each stage: extraction uses energy and can damage habitats; manufacture uses energy and water and may release pollutants; use depends on reuse — a plastic bag reused many times spreads its impact, while paper bags tear and may be replaced; disposal differs because plastic is durable and non-biodegradable but can be recycled, whereas paper is biodegradable and recyclable but may release methane in landfill. Weigh the stages to decide which bag has the smaller overall impact.
Your focus
- List and describe the stages of a life cycle assessment, including processing and packaging.
- Explain how transport and distribution are considered at each stage of an LCA.
- Use LCA data to compare products and justify a conclusion about environmental impact.
Show all 24 objectives
- Describe how raw materials are extracted from the Earth and processed into usable forms.
- Explain environmental and resource impacts arising from extraction and processing.
- Apply the idea of a functional unit when comparing the impacts of different materials.
- Describe the manufacturing and packaging stages of a product life cycle.
- Explain how packaging material choices affect environmental impact across the life cycle.
- Compare packaging options fairly using a stated functional unit.
- State what happens during the use and operation stage of a product's life cycle.
- Give examples of resources consumed and wastes produced while a product is used.
- Compare the use stage of two products in terms of their environmental impact.
- Describe ways in which products can be disposed of at the end of their useful life.
- Explain why transport and distribution are counted at each stage of a life cycle assessment.
- Compare the environmental impact of different disposal routes for a named product.
- State at least three inputs or outputs of a product life cycle that can be fairly easily quantified.
- Explain why allocating numerical values to pollutant effects requires value judgements.
- Conclude, with a product example, why an LCA is not a purely objective process.
- Describe what is meant by a selective or abbreviated LCA.
- Explain how the choice of stages or impacts can lead to a pre-determined conclusion.
- Evaluate an advertising claim by identifying what an abbreviated LCA has included and omitted.
- Carry out a simple comparative LCA for plastic and paper shopping bags, covering extraction, manufacture, use and disposal.
- Explain how reuse and disposal choices change the overall environmental impact of each bag.
- Reach and justify a conclusion that weighs evidence from all four LCA stages and states the assumptions made.
Life cycle assessment exam tips
Marking Points
- Names the stages: extracting and processing raw materials, manufacturing and packaging, use and operation, and disposal.
- Explains that transport and distribution are included at each stage of the life cycle.
- Assesses each stage for environmental impacts such as energy use, resource depletion, waste, and pollution.
- Applies the stages to a named product, such as a plastic or glass bottle, to show understanding.
- Recognises that the outcome depends on the data, assumptions, and boundaries used in the assessment.
- Identifies extraction as obtaining raw materials from the Earth, such as quarrying limestone, mining metal ores, drilling crude oil or harvesting timber.
- Describes processing as converting extracted material into a usable form, for example crushing and heating limestone, reducing metal ores or fractionally distilling crude oil.
- Recognises that extraction and processing need energy, commonly from burning fossil fuels, and so contribute to resource use and emissions.
- Links these stages to specific environmental effects such as habitat destruction, land use, water use, noise, dust or release of carbon dioxide and sulfur dioxide.
- Uses the idea of a functional unit, such as one kilogram of material, so that comparisons between products are fair.
- Places extraction and processing as the first stages of a life cycle assessment, before manufacture, transport, use and disposal.
- Evaluates trade-offs, for example a material that is energy-intensive to process but light and long-lasting in use.
- Describes manufacturing as converting processed materials into a finished product through shaping, moulding, joining, assembling or finishing.
- Recognises that manufacturing uses energy, often from fossil fuels, and can release pollutants, use water and produce waste.
- Explains the functions of packaging, such as protection, hygiene, containment, information and marketing.
- Identifies packaging materials such as paper, card, glass, plastic, steel and aluminium, and links each to its own extraction, processing and disposal impacts.
- Compares packaging options, for example glass being heavy to transport but widely recyclable, against plastic being light but often fossil-fuel based.
- Places manufacturing and packaging between raw material processing and distribution, use and disposal in the life cycle.
- Uses a functional unit, such as one litre of drink delivered, so that packaging comparisons are fair.
- Identifies the use and operation stage as the period when the product is being used for its intended purpose, between manufacture and disposal.
- Describes the inputs consumed during use, such as electricity, fuel, water or replacement parts.
- Describes the outputs produced during use, such as emissions, waste heat or waste water.
- Explains that impacts during use depend on how long the product lasts and how often it is used.
- Compares two products by the resources used and pollution produced during their working lives.
- Links the use stage to the wider LCA by noting it must be weighed against manufacture and disposal.
- Describes disposal options at end of life, such as recycling, landfill, incineration or reuse.
- Explains that different disposal routes have different environmental impacts, for example landfill versus recycling.
- States that transport and distribution occur at each stage of the life cycle, not only at the end.
- Gives examples of transport stages, such as raw materials to factory, product to shop and waste to disposal site.
- Explains that transporting materials and products uses fuel and produces emissions.
- Links transport and disposal together as parts of a complete LCA rather than separate afterthoughts.
- Identifies quantifiable inputs such as water volume, raw material mass and energy in joules or kilowatt-hours.
- Identifies quantifiable outputs such as mass of waste, volume of effluent or mass of gas emitted.
- Explains that pollutant effects are difficult to express in a common numerical unit because impacts differ in type and severity.
- Explains that comparing or weighting different effects requires a value judgement about which impact matters most.
- Concludes that an LCA mixes measured data with subjective decisions, so it is not purely objective.
- Uses a product example, such as a plastic bottle or cotton T-shirt, to show where measurement stops and judgement begins.
- Defines a selective or abbreviated LCA as one that covers only some stages, materials or impact categories.
- Explains a legitimate reason for abbreviating, such as limited time, cost or missing data.
- Explains how choice of boundaries or impact categories can steer an LCA towards a pre-determined conclusion.
- Gives a specific example, such as comparing only the use phase of two products while ignoring manufacture or disposal.
- Explains how such a result can support advertising claims that present the product as environmentally friendly.
- Suggests a check, such as asking which stages and impacts were included and who commissioned the study.
- Identifies the four LCA stages: raw material extraction, manufacture, use and disposal, and applies each stage to both bag types.
- Compares raw materials: plastic bags use crude oil, a finite resource, while paper bags use wood, which can be renewable if forests are managed sustainably.
- Compares manufacture and use: both need energy and water, but reuse of a plastic bag many times can lower its impact per use, while paper bags may need replacing more often.
- Compares disposal: plastic is durable and non-biodegradable but recyclable, whereas paper is biodegradable and recyclable but can produce methane if buried in landfill.
- Reaches a justified comparative conclusion that weighs the stages rather than judging on one stage alone, and recognises that the answer depends on assumptions such as number of reuses.
Examiner Tips
- 💡Structure your answer around the specific stages listed in the specification so no part is omitted.
- 💡Remember to explicitly mention transport and distribution as a factor across all stages.
- 💡Use a named product and give a specific example at each stage, such as crude oil extraction for plastic.
- 💡Name a specific material and its extraction method, then state one processing step, to show understanding rather than generalising.
- 💡When comparing materials, state the functional unit you are using so the comparison is valid.
- 💡Use comparative language such as 'more energy-intensive than' and support it with a reason, rather than just listing impacts.
- 💡Give one benefit and one drawback of a named packaging material to show balanced evaluation.
- 💡State the functional unit explicitly when comparing two packaging options.
- 💡Link each impact to a stage of the life cycle so your answer stays structured and easy to credit.
- 💡Name the stage explicitly and then give one input and one output of use to show you understand what it covers.
- 💡Use a familiar product such as a car, phone or kettle and state one resource it consumes while working.
- 💡When asked to compare, refer to both products and give a reason based on lifetime energy or resource use.
- 💡When describing disposal, give at least two routes and say how their impacts differ.
- 💡Mention transport at more than one stage to show you understand it applies throughout the life cycle.
- 💡Use a short chain such as raw material to factory to shop to home to disposal site to structure your answer.
- 💡Use the phrase 'value judgement' explicitly when explaining why pollutant effects are hard to score.
- 💡Give one measured quantity and one judged quantity in the same answer to show the contrast.
- 💡Link your conclusion back to the word 'objective' rather than just saying LCA is 'unfair' or 'biased'.
- 💡Name the stage or impact that has been omitted when you criticise an example.
- 💡Use the phrase 'pre-determined conclusion' to show you understand the intention behind the misuse.
- 💡Balance your answer by giving one fair use and one unfair use of an abbreviated LCA.
- 💡Structure your answer stage by stage (extraction, manufacture, use, disposal) so every clause of the comparison is covered.
- 💡Use comparative connectives such as whereas, however and therefore to make the weighing of stages explicit.
- 💡Finish with a clear conclusion that names the assumptions, for example how many times each bag is reused, rather than declaring one bag universally better.
Common Mistakes
- Omitting processing and packaging: correction — ensure you state 'extracting and processing raw materials' and 'manufacturing and packaging'.
- Treating transport as a single separate stage: correction — transport and distribution must be considered at each stage of the life cycle.
- Treating an LCA as only about disposal or recycling: correction — all stages must be considered, from raw materials to end of life.
- Treating extraction and processing as the same stage: extraction removes material from nature, while processing changes it chemically or physically into a usable substance.
- Assuming all raw materials are renewable: metal ores and fossil fuels are finite, whereas timber can be regrown if managed sustainably.
- Ignoring the energy and pollution from processing and focusing only on the digging or drilling, which understates the impact of this stage.
- Thinking packaging is always wasteful: packaging can reduce food waste and damage, which may lower overall impact.
- Comparing packaging by mass alone: a light plastic wrapper and a heavy glass bottle must be compared per functional unit, not per gram.
- Forgetting that manufacturing energy and transport between factories are part of this stage, not separate from it.
- Treating the use stage as only the moment of purchase or first switch-on; correct this by describing the whole working life, including servicing and consumables.
- Assuming manufacture always causes the greatest impact; correct this by comparing stages, since a long-lived appliance may use more energy in operation than in production.
- Confusing use with disposal; correct this by keeping operation (energy in, emissions out) separate from end-of-life processing.
- Thinking disposal only means throwing items in the bin; correct this by naming recycling, reuse and incineration as alternatives with different impacts.
- Forgetting transport between stages and counting only delivery to the customer; correct this by listing journeys at every stage, including waste collection.
- Assuming recycling has no environmental cost; correct this by noting collection and reprocessing still need transport and energy.
- Claiming an LCA is completely objective because it uses data: correct this by stating that the data are objective but the weighting of pollutant effects is subjective.
- Treating all pollution as one identical category: correct this by noting that effects such as global warming, acid rain and habitat loss are different in kind and cannot simply be added.
- Assuming every LCA must cover every stage: correct this by explaining that an LCA can be selective or abbreviated, which is the focus of the next statement.
- Saying an abbreviated LCA is always wrong: correct this by stating it can be a valid evaluation when its limits are made clear.
- Confusing a selective LCA with a dishonest one: correct this by separating the method from the misuse of the method.
- Assuming a published figure must be complete: correct this by checking which stages and impacts the figure actually covers.
- Judging paper as always better because it is biodegradable; correction: biodegradability is only one disposal factor, and growing and processing wood also uses energy, water and land.
- Ignoring the use stage and comparing only manufacture; correction: how many times a bag is reused strongly changes its impact per shopping trip.
- Treating an LCA as a single score with no uncertainty; correction: LCAs involve estimates and value judgements, so state the assumptions behind your comparison.