Chapter 07 · Materials & footprintsLife Cycle Assessment & Product Footprinting
Avoided burden / system expansion
Definition
In life cycle assessment, a method for handling multi-functionality (processes serving more than one function, such as recycling or energy recovery) by expanding the system boundary: the studied system is credited with the burdens of the alternative production it avoids. ISO 14044 ranks avoidance of allocation — by subdividing processes or by system expansion — above partitioning (physical or economic allocation) in its allocation hierarchy.
References
Allocation hierarchy (avoid by subdivision or system expansion first, then physical, then other relationships); recycling/reuse allocation; transparency and sensitivity requirements.
Overview
What it means
Under avoided burden, recycling aluminium, for example, is modelled as displacing primary aluminium production, so the recycled product carries a credit for the avoided mining and smelting. This makes results sensitive to assumptions about what exactly is substituted — the most contested choice in the method. The alternative is partitioning: splitting burdens between co-products by physical or economic relationships.
How it is used
Practitioners choose between system expansion (common in consequential LCA and policy analysis) and allocation (common in attributional product footprints) depending on the study's question. The choice can dominate results, so ISO requires transparency about the approach and sensitivity analysis where cut-off or allocation decisions could affect conclusions.
Why it matters
Allocation choices are where LCA results are most easily steered. Understanding avoided burden is essential for reading comparative claims — "recycled is better" figures often depend entirely on substitution assumptions.