Reliability and Environmental Sustainability Relationships: A Stochastic Analysis of Product Lifespan and Global Warming Potential

This paper introduces the so-called Sustainability-Usage Ratio (SUR), relating the Global Warming Potential (GWP) of a product to the duration of its use and it introduces an approach for evaluating the SUR.To this end, two principal methods are presented: one based on the arithmetic mean usage and another integrating over the product's GWP curve and its usage distribution to derive a mean SUR value.By accounting for reliability data, user behavior, and potential early discarding, more sophisticated assessment of environmental sustainability is enabled.The paper illustrates these concepts with an example comparing two electric kettles, which differ in their lifetime distributions and GWP contributions from manufacturing and disposal.Results highlight that the arithmetic meanbased method can overly reward products with long nominal lifespans, particularly when user preferences or premature failures reduce actual usage.In contrast, integrating the failure distribution produces a more conservative yet realistic estimation of overall sustainability performance.These findings underscore the importance of selecting an appropriate metric based on the decision context.The framework presented here aids stakeholders -from product designers to consumers -in making more informed choices about product sustainability, while also providing insights into optimizing product design and usage strategies to reduce greenhouse gas emissions.