Life cycle assessment (AQA GCSE Chemistry Combined Science): Revision Notes
Life cycle assessment
What is life cycle assessment?
A life cycle assessment (LCA) looks at how much a product harms the environment. It checks the whole life of a product - from getting the raw materials to throwing it away.
LCA helps us understand the total environmental impact of products. This means we can make better choices about what to buy and use.
LCA is essential for making informed decisions about sustainability because it prevents us from focusing on just one aspect of environmental impact while ignoring others.
What factors does LCA consider?
Scientists look at four main things when doing an LCA:
- Use of energy - How much electricity, gas or fuel is needed
- Use of raw materials - What natural resources are taken from the Earth
- Use of water - How much water is needed in all stages
- Production of waste - How much rubbish is made
These factors matter at every stage of the product's life.
All four factors are interconnected - for example, using more energy often means extracting more raw materials for fuel, which can also increase water usage and waste production.
The life cycle stages
Products go through six main stages:
- Raw material extraction - Getting materials from nature (like mining metals)
- Raw material processing - Turning raw materials into useful forms
- Manufacturing and packaging - Making the product and putting it in boxes/bags
- Transport - Moving products to shops and customers
- Use and operation - When people actually use the product
- Disposal after use - What happens when the product is thrown away
All these stages use energy and create waste.
Real example - comparing shopping bags
Worked Example: Government Shopping Bag Study
A government study compared different shopping bags. Here's what they found:
Energy use per 1000 bags:
- Single-use plastic bag: 22.1 MJ (lowest energy)
- Cotton bag: 39.6 MJ
- Plastic bag for life: 167.5 MJ (highest energy)
Waste produced per 1000 bags:
- Plastic bag for life: 170g (least waste)
- Cotton bag: 1800g (most waste)
- Single-use plastic bag: 420g
This shows why LCA is important - different factors give different answers!
Avoiding misleading claims
Companies sometimes make misleading claims about their products.
Common Misleading Claim Example:
"Cotton bags are better for the environment because they use less energy"
Why this claim is wrong:
- Cotton bags do use less energy than bags for life
- But cotton bags make 10 times more waste than plastic bags
- You need to look at all factors, not just one
Always check if environmental claims consider the whole life cycle.
Remember!
Key Points to Remember:
- Life cycle assessment checks environmental impact from start to finish
- Four key factors: energy, raw materials, water, and waste
- Products go through six stages from extraction to disposal
- Different factors can give different results - energy vs waste
- Watch out for misleading claims that only mention one factor