Service distance and ratio-based location-allocation models for siting recycling depots

Siting appropriate locations for placing recycling depots is essential for promoting an efficient recycling program. This study develops three optimization models to facilitate siting analysis for district-based, district open, and nondistrict situations. An enhanced model to improve drawbacks of locating recycling depots that mainly serve residents in adjacent districts using the district open model is also proposed. Three factors of service distance, local service ratio, and service ratios for different distance ranges are used to compare the effectiveness of alternatives obtained from different models. A case study involving 16 city districts is implemented to demonstrate the applicability of the proposed models. Findings show that the district-based alternatives have best overall service distance and service ratio, but with a poor local service ratio. The enhanced model obtains alternatives that achieve good local service ratio with acceptable service distance and service ratios for different distance ranges.