Spatial service location-allocation analysis for siting recycling depots

Although recycling depots can promote recycling, their spatial distributions significantly affect efficiency. Despite the ability to locate depots throughout a region by minimizing total service distance, residents in sparsely populated areas may have to travel long distances to a depot. Although increasing the number of depots can reduce these distances, the associated costs increase. This study develops six optimization models based on the three objectives of minimizing maximal service distance, maximizing the service ratio, and minimizing the number of depots for district-based, district-open and nondistrict scenarios. Three factors, service distance, district equity, and service ratio, are used to assess the performance of models. A case study of 16 districts is utilized to demonstrate the application of the models. Minimizing the number of depots under the nondistrict scenario achieves a good service ratio with short service distance using fewer depots than other models. The proposed models will facilitate efforts to determine an appropriate spatial distribution of recycling depots.