Sustainable Hybrid Manufacturing and Refurbishing Systems with Substitution

This study considers the planning decisions in a production facility that receives returned products as a contribution to sustainability through the reduction in waste from used products. It involves three processes: the refurbishing and disassembly of returned items and the manufacturing of new items. The process is driven by the demands of new items and collected secondhand items. In this study, we consider a downward substitution, in which new items could be used to meet the demand for secondhand items. The objective is to determine the best production planning schedule to satisfy all demands while minimizing the total costs of production and inventory. We propose and analyze different configurations distinguished by their level of integration and whether they allow substitution. Integration is mainly achieved through the sharing of the inventory of returns between the refurbishing line and the disassembly line, which responsible for feeding the manufacturing process with "as good as new" parts. The best configuration is identified based on the total cost and environmental impact. Four heuristics based on combining relax-and-fix and fix-and-optimize approaches are proposed. Numerical experiments have shown that the heuristics are very efficient, achieving gaps of less than 1% from the optimum in short CPU times for most instances. Numerical experiments have also shown that integration through the sharing of returns inventories leads to considerable cost and environmental benefits.