Allocation is the act of setting aside or distributing resources, responsibilities, or flows for a specific purpose. In its general sense, the term describes any systematic process of assigning or apportioning elements according to defined criteria or objectives.
Within the context of life cycle assessment, allocation is often used as technical jargon to refer specifically to co-product allocation. Co-product allocation involves partitioning 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 becomes necessary when a single process produces multiple products simultaneously, and practitioners need to determine how to distribute the environmental burdens and benefits amongst these co-products.
The allocation challenge arises because many industrial processes inherently generate multiple valuable outputs, such as refineries producing various petroleum products or livestock systems yielding meat, milk, and hides. Determining how to fairly and accurately assign environmental impacts to each co-product remains one of the methodologically challenging aspects of LCA practice, leading to ongoing discussions about appropriate allocation methods and, where possible, the preference for avoiding allocation through system expansion approaches.
