The Heterogeneous Vehicle Routing Problem with Multiple Time Windows for the E-Waste Collection Problem

Waste from electrical and electronic equipment (WEEE) or e-waste describes end-of-life electronic products that are discarded. Due to their toxic and negative impacts to humans' health, many publications have been proposed to handle, however, studies related to e-waste collection and transportation to waste disposal sites are not widely studied so far. This study proposes a mixed integer linear programming (MILP) model to solve the e-waste collecting problem by formulating it as the heterogeneous vehicle routing problem with multiple time windows (HVRPMTW). The model is validated with newly developed benchmark instances that are solved by commercial software, CPLEX. The model is also adopted for solving a real case study in the context of Singapore. The results show that the proposed mathematical model is a good start for formulating and solving the problem with reasonable problem sizes. From a managerial perspective, this offers significant practical improvements.