Partitioning is the process of dividing the input or output flows of a process or Product system between the product system under study and one or more other product systems. This term is used synonymously with Co-product allocation in Life Cycle Assessment.
According to ISO 14040, partitioning involves distributing the environmental burdens and resource consumption of an Activity that produces multiple Co-products amongst those co-products. The result of the partitioning procedure is as many partitioned systems as there are co-products in the original system. Importantly, the sum of all the partitioned systems equals the system before partitioning, ensuring mass and energy balance is maintained.
Partitioning becomes necessary when an activity generates multiple product outputs and the analyst needs to assign environmental impacts and resource use to each specific product. Various partitioning criteria can be applied, including physical relationships such as mass or energy content, economic value such as market prices or revenues, or other relationships that reflect the underlying physical connections between the co-products and their environmental burdens.
The choice of partitioning approach can significantly influence LCA results, particularly when co-products have substantially different economic values or physical properties. ISO 14044 provides a hierarchy for addressing multi-functionality, recommending subdivision or system expansion first, and partitioning only when these approaches cannot be applied. When partitioning is necessary, the standard recommends that allocation should reflect underlying physical relationships between products and their associated burdens.
Alternative approaches to partitioning include system expansion, which avoids the need for partitioning by expanding the system boundary to include the displaced products and their associated environmental burdens.
