Reuse-efficiency model for evaluating circularity of end-of-life products

Reusing end-of-life products is an effective approach to reduce environmental waste. It is crucial to evaluate the number of products that will be reused quantitatively when the durability of circular products and the collection rate of end-of-life products are improved to enhance the circulation of reusable products. Likewise, it is necessary to evaluate how multiple reuse cycles affect the circularity of reusable products in the product design stage. This study develops a reuse-efficiency model to evaluate the extent of reuse of end-of-life products quantitatively. Circular products are characterised by 'relative deterioration' and 'absolute deterioration', and the time to each type of deterioration follows an independent probability distribution. The reuse-efficiency model is developed based on the harmonic mean of three reuse-efficiency factors generated by the relative and absolute deteriorations. The effects of the product's durability, collection rate and recycling rate of end -of-life products, and maximum number of reuse cycles on the reuse efficiency are investigated. Furthermore, the optimal durability of a product, optimal collection rate of end-of-life products, and maximum number of reuse cycles are obtained by maximising the reuse efficiency per unit cost, which considers the costs of durability extension and collection of end-of-life products. The insights obtained from this study encourage the redistribution and reuse of products and are expected to establish an improved circular economy.