Environmental and cost trade-offs uncertainty in ecodesign: a new approach to communicate life cycle impacts

Ecodesign involves significant uncertainty, especially at early design stages, when information is scarce, and multiple assessment criteria must be considered simultaneously. Such uncertainty can lead to misleading conclusions when comparing potential ecodesign alternatives. Stochastic Multi-Attribute Analysis (SMAA) can help address this challenge by propagating uncertainty in Life Cycle Impact Assessment (LCIA) indicators and other criteria through Monte Carlo simulation, providing a robust decision-support framework. This article proposes an ecodesign decision-support approach to communicate trade-offs between environmental and cost dimensions under uncertainty. The environmental weight threshold quantifies the minimum weight that must be assigned to the environmental dimension for a given ecodesign alternative to be preferred over a business-as-usual situation. The proposed decision-support approach is applied to an ecodesign case study of a nutraceutical bottle made of high-density polyethylene (HDPE). The results show that a future bottle made of 30 % recycled polymer from post-hospital waste is the ecodesign alternative with the largest potential to replace the current HDPE bottle. The additive aggregation model and PROMETHEE multicriteria methods are compared, showing that the environmental weight threshold is method-agnostic. The case study also demonstrates that the proposed approach avoids the sensitivity of SMAA's traditional rank acceptability index regarding hierarchical vs. non-hierarchical weighting, and can support choices concerning the development of more competitive products with lower environmental impacts.