A life-cycle analysis (LCA) measures environmental inputs, outputs, and potential impacts across a product's life cycle. In IB Design Technology HL C3.2, key impact categories include global warming potential, ecotoxicity, and resource depletion.
How the impacts are measured
An LCA establishes a functional unit so alternatives can be compared fairly, such as one reusable bottle used for five years. It then defines a system boundary covering relevant stages: raw-material extraction, processing, manufacturing, distribution, use, and end-of-life disposal or recovery.
The material and energy inputs and the emissions and waste outputs form the life-cycle inventory. These data are then classified into environmental impact categories.
| Impact category | What it measures | Typical evidence or unit |
|---|---|---|
| Global warming potential | The contribution of greenhouse-gas emissions to climate change over a specified period. Different gases are converted according to their warming effect relative to carbon dioxide. | Kilograms of carbon-dioxide equivalent, often written as kg CO₂-eq |
| Ecotoxicity | The potential harm caused by toxic substances released into terrestrial, freshwater, or marine ecosystems. It considers factors such as chemical persistence, concentration, and effects on organisms. | Toxic releases and their calculated ecosystem impact potential |
| Resource depletion | The reduction of finite natural resources caused by extracting and consuming fossil fuels, minerals, metals, or other scarce materials. | Quantity used, scarcity, and remaining availability of the resource |
For example, aluminium production may have high global warming potential because it requires substantial electrical energy. Mining its ore contributes to resource depletion, while contaminated mine drainage may increase ecotoxicity.
A common misconception is that an LCA gives one completely objective environmental score. Results depend on the functional unit, system boundary, data quality, assumptions, and weighting of impact categories.
Exam technique
For an IB response, identify each impact category, explain what it measures, and connect it to a specific life-cycle stage. When asked to evaluate, also discuss trade-offs and limitations: a design may reduce resource depletion through recycling while still having high global warming potential during manufacture.