Environmental assessment of lifetime extension strategies

Doctoral thesis, 2025

Extending product lifetimes through strategies such as reuse, repair, or remanufacturing has been suggested as a means for delaying product replacement and thus improving products' environmental performance. To identify effective lifetime extension strategies, companies or policymakers seek guidance from the assessment of environmental impact of products with, for example, circular economy (CE) indicators or life cycle assessment (LCA). The additional product lifetime duration is the reason for the improved environmental performance with lifetime extension and, therefore, a key variable in this assessment. However, little guidance exists on how to assess lifetime extension strategies. Against this background, this research aims to develop knowledge of environmental systems analysis methodology for assessing product lifetime extension. This knowledge is used to identify methodological considerations for practitioners to select suitable assessment methods and LCA methodology for product lifetime that fit their specific assessment goal.

Applying CE indicators and LCA to case studies of lifetime extension reveals that LCA provides information on the environmental impacts while CE indicators detail variations in resource use. Thus, the choice between CE indicators and LCA depends on the type of impact a practitioner aims to evaluate. Moreover, no CE indicator accounts for resource use in the use phase, although it is key in the resource use of lifetime extension for some products. Therefore, the choice of method requires practitioners to ensure sufficient coverage of the parts of the product system for the changes from lifetime extension to be accounted for.

A review of existing LCAs of lifetime extension identifies differences in LCA methodology related to product lifetime in terms of 1) the lifetime definition (e.g., whether it includes the entire technical lifetime), 2) the lifetime integration in equations with three approaches using either a single value, a no-fixed value or a distribution, and 3) the lifetime sensitivity analysis. When testing the identified approaches on cases, the results answer different typical questions. For example, using a no-fixed value informs on the range of validity of the conclusions, while using a distribution informs on the spread and average environmental impacts in a population. It emphasises the importance of selecting a lifetime modelling methodology that aligns with the assessment goal.

Given the critical role of product lifetime in the environmental performance of lifetime extension, along with the often insufficient reporting practices and limited consideration in assessment methodology discussions, this research serves as a foundational step towards guidance to practitioners and further methodological developments.