A determining product is a Product output of an Activity for which a change in demand will directly affect the production volume of that activity. This concept in Life Cycle Assessment establishes the causal relationship between market demand and production decisions, making it important for consequential modelling approaches.
The defining characteristic of a determining product is its market-driven influence on activity levels. When demand for a determining product increases, the activity that produces it will typically scale up production accordingly. Conversely, when demand decreases, production volumes decline. This responsiveness distinguishes determining products from by-products, which are produced as secondary outputs whose quantities are largely determined by the production levels of other products from the same activity.
The ecoinvent database uses the term "reference product" as a synonym for determining product. Whilst both terms describe the same concept, "determining product" more clearly emphasises the causal relationship between demand and production volume, making the term especially useful in consequential LCA modelling where understanding marginal changes and market responses matters.
Understanding which products are determining products versus by-products matters for system modelling decisions, especially when handling multi-output activities and applying system expansion. This distinction affects how substitution effects are modelled in the life cycle.
As Chief Operating Officer, Iris leads our organisational development and oversees day-to-day operations. Before joining 2-0, she worked in the biotechnology sector. As an LCA consultant, Iris has devoted her expertise primarily to the domains of sustainable agriculture and food production. She is dedicated to teaching LCA and is responsible for our educational efforts. Iris holds an M.Sc. in Biology – Biotechnology from the University of Copenhagen.
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Glossary terms are clearer once you have seen them applied. Our guide to what LCA is and how it works walks through the complete methodology: goal and scope, inventory modelling, impact assessment, and interpretation.
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