A conditional exchange is an Exchange that is only considered for a specified System model. This concept, developed by the ecoinvent database, addresses the challenge that different system modelling approaches require different representations of the same activity within LCA datasets.
The need for conditional exchanges arises from the distinct ways that attributional and consequential system models handle certain flows within a product system. Whilst ISO 14040 defines exchanges as causal, directional relationships between activities or between activities and the environment, it does not specify how these exchanges should be adapted when applying different system models to the same underlying activity data.
In practical terms, conditional exchanges allow database developers to maintain a single activity dataset configured for different modelling contexts. For example, an exchange representing the use of a by-product might be included in an attributional model but replaced with a substitution credit in a consequential model. Rather than maintaining separate datasets for each system model, conditional exchanges let the same dataset behave differently depending on the system model.
This is especially useful in large LCA databases, as it reduces data duplication whilst keeping the modelling logic consistent with the chosen system model's assumptions. When a user selects a system model for their analysis, only the exchanges relevant to that model are activated, whilst conditional exchanges tied to other system models are excluded from the calculation.
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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