Product Lifetime in Life Cycle Assessment of Circular Strategies

Övrigt konferensbidrag, 2024

Lifetime extension through, e.g., repair or reuse, is one of the key strategies of circular economy and is expected to reduce society´s environmental impacts by delaying product replacement. Environmental benefits and limitations of lifetime extension have been commonly assessed with life cycle assessment (LCA) showing that product lifetime significantly influences LCA results. However, no guidance is provided to LCA practitioners on how to model product lifetime. Thus, this study provides an overview of available modelling approaches through a literature review of LCAs of lifetime extension and compares the advantages and limitations of the identified approaches on the case of remanufactured mattresses.

The review focused on LCA studies having a specific interest in product lifetime and identified three modelling steps: definition, modelling, and sensitivity analysis. The most common approach defines the product lifetime as a service lifetime (i.e., ending with the end of use not necessarily corresponding to the product´s breakage) expressed in years with partitioning (i.e., distinction between initial and additional lifetime with the extension strategy), and model it as a single value with testing different values for sensitivity analysis. Two other modelling approaches were identified: using no fixed value (i.e., a parameter) or using a distribution over a population sample.

LCA results with these modelling approaches provide different insights. Modelling with a single value allows a clear analysis of life cycle stage contributions while modelling with no fixed value emphasises the evolution of the environmental impacts as a function of lifetime and the threshold for remanufacturing to be beneficial. Modelling with a distribution provides information on the average and spread of environmental impacts, allowing the identification of user groups for which lifetime extension is environmentally arguable or not.

This study thus shows that product lifetime modelling in LCA is complex and adapting lifetime modelling to the goal of the LCA is essential for meaningful assessments of lifetime extension. The findings guide LCA practitioners in making informed methodological choices for meaningful and robust assessments of the environmental performance of lifetime extension.