Life-Cycle Assessment for Materials and Manufacturing
Functional units, system boundaries, inventories, allocation and interpretation explained for engineering use.
Start with the function
Life-cycle assessment compares systems that provide an equivalent function. The functional unit defines what is delivered, for how long and under what performance conditions.
Set the boundary
Cradle-to-gate, cradle-to-grave and circular boundaries include different stages. Boundary choices can change conclusions, so exclusions must be explicit.
Build the inventory
Material, energy, transport, yield, scrap, emissions and end-of-life flows form the life-cycle inventory. Primary data improves specificity, while databases fill gaps.
Interpret with caution
Results depend on electricity mix, allocation, recycling assumptions, geography and time. Sensitivity and uncertainty analysis reveal whether conclusions are robust.
Working rule
Use LCA to compare defined systems, not to attach a permanent environmental score to a material name.