Life Cycle Assessments
What Is a Life Cycle Assessment (LCA)?
A life cycle assessment is a method used to evaluate the environmental impact of a product at every stage of its life — from obtaining the raw materials to its final disposal. It is sometimes described as a "cradle-to-grave" analysis.
The Four Stages of a Life Cycle Assessment
1. Extracting and Processing Raw Materials
This stage covers:
- Mining ores or drilling for oil (energy use, habitat destruction)
- Processing raw materials (e.g. smelting metal ores, refining crude oil)
- Environmental impacts include: use of finite resources, energy consumption, release of CO₂ and pollutants, water use, land degradation
2. Manufacturing and Packaging
This stage includes:
- Making the product in a factory (energy use, waste generation)
- Packaging — materials used and their environmental cost
- Transport of materials to the factory
- Impacts: energy use, CO₂ emissions, waste produced, water and chemical use
3. Using the Product
During use, the product may:
- Require energy (e.g. electrical appliances, cars)
- Need maintenance or replacement parts
- Release substances into the environment (e.g. exhaust fumes from cars)
- Some products have minimal impact during use (e.g. a ceramic mug)
4. Disposal at End of Life
Options include:
- Landfill — takes up space, may leach chemicals, non-biodegradable plastics persist
- Incineration — releases CO₂ and potentially toxic gases, but can generate energy
- Recycling — saves raw materials and energy, but collection and processing have their own costs
- Composting — for biodegradable materials only
Example: Paper vs Plastic Bags
| Stage | Paper bag | Plastic bag |
|---|---|---|
| Raw materials | Trees (renewable, but forestry uses land/water/energy) | Crude oil (finite resource) |
| Manufacturing | High energy and water use; chemical pulping produces waste | Less energy to manufacture; lighter |
| Use | Tears easily; single use | Stronger; can be reused multiple times |
| Disposal | Biodegradable; recyclable; compostable | Not biodegradable; recyclable; persistent litter |
Neither option is clearly "better" overall — each has advantages and disadvantages at different stages.
Example: Ceramic vs Polystyrene Cup
A ceramic mug has a higher environmental impact in manufacturing (high-temperature kiln, mining clay) but lasts for years.
A polystyrene cup is cheap and lightweight to produce but is single-use and not easily recycled.
Over many uses, the ceramic mug has a lower overall impact per use because its manufacturing impact is spread over thousands of drinks.
Limitations of Life Cycle Assessments
LCAs have some important limitations:
- Quantifying some impacts is difficult — how do you measure the exact impact of habitat loss or visual pollution in numbers?
- Subjective judgments are involved — different assessors may weigh factors differently
- Data quality varies — getting accurate data for every stage is difficult, especially across complex supply chains
- Boundary choices — what to include and exclude can affect results
- Can be biased — companies may commission LCAs that present their product favourably (selective data or boundaries)
- Different LCAs of the same product can reach different conclusions depending on assumptions made
Because of these issues, LCAs are useful tools but should not be taken as definitive proof that one product is better than another.
Selective and Simplified LCAs
Companies sometimes produce simplified LCAs that only cover part of the life cycle or only some environmental impacts. These can be misleading if used in marketing to make a product appear more environmentally friendly than it actually is (greenwashing).
A full LCA is more reliable but is expensive, time-consuming and complex to carry out.
Carbon Footprint
A carbon footprint is a simplified form of LCA that measures only the greenhouse gas emissions (mainly CO₂ and CH₄) associated with a product or activity over its life cycle.
It is easier to calculate than a full LCA but gives an incomplete picture of environmental impact because it ignores other factors like water use, toxicity and resource depletion.
Using LCAs to Make Decisions
LCAs help consumers, businesses and governments make more informed choices:
- Choosing materials with lower environmental impact
- Redesigning products to use less material or energy
- Selecting better disposal or recycling methods
- Comparing alternative products or processes
- Setting environmental policy and regulations
Exam Tips
- Know the four stages of an LCA: raw materials, manufacturing, use, disposal
- Be able to compare two products using LCA thinking (e.g. plastic vs paper, ceramic vs polystyrene)
- Understand that LCAs involve subjective judgments and can be biased — this is a frequent exam point
- Questions may ask you to evaluate claims made using LCAs — look for missing stages, selective data, or unfair comparisons
- A carbon footprint is a simplified LCA that only covers greenhouse gas emissions