LCA Fundamentals: Life-Cycle Logic and Decision Context
What this domain tests
LCA Fundamentals checks whether you can frame a study as a life-cycle assessment rather than a single-site audit. Expect questions on the four-phase framework, attributional versus consequential modelling, the meaning of potential impacts, and the limits of comparability.
Core rules and concepts
- LCA compiles inputs and outputs and evaluates potential environmental impacts across a product system's life cycle.
- The four phases are goal and scope, inventory, impact assessment, and interpretation; they are iterative, not a fixed waterfall.
- Attributional LCA describes burdens linked to a product system. Consequential LCA models changes caused by a decision, often using marginal suppliers and substitution.
- LCIA results are potential impacts under stated assumptions, not measured harm or compliance values.
- Comparability requires equivalent function, boundary, data quality, and impact method.
Worked example
A study compares paper and plastic grocery bags. The initial functional unit is "one bag". This is weak because bags carry different loads and have different reuse rates. Revise it to "carry 10 kg of groceries for one shopping trip, using the number of bags actually needed". If paper bags hold more but require more material per bag, the reference flows change, and the result may reverse. The reasoning is functional equivalence first, then inventory scaling, not a per-bag headline number.
Traps that cost marks
- Comparing products per kilogram or per unit instead of per delivered function.
- Treating a cradle-to-gate inventory as a full life-cycle result.
- Calling an LCIA score an actual environmental risk.
- Mixing attributional and consequential assumptions within one comparison.
- Claiming a product has zero impact because it is natural or recyclable.