Improving the Efficiency of Urban Waste Collection Using Optimization: a Case Study

With increasing population, urbanization and industrialization, municipal solid waste management has become a key challenge for rapidly growing cities. A significant portion of solid waste management cost is associated with waste collection and transportation. This study aimed at routing and assignment of waste collection tractors to road segments so as to minimize the waste collection and transportation cost in the Kurunegala municipal council area of Sri Lanka. We constructed the waste collection network using the data obtained from the municipal council, online sources and published surveys and then formulated the corresponding waste collection problem as a capacitated arc routing problem (CARP) using binary integer programming (BIP) methods. The optimization model was developed using the PuLP modelling language in SolverStudio. We applied the model to a selected portion of the council area consisting of 5 wards currently served by 31 weekly waste collection trips which start and end at the dumping site. The optimal tractor assignment and routing policy shows potential to reduce the number of weekly trips by 19% and the weekly travelling distance of the tractors by 36%. The optimal routes tend to be cyclic routes without frequent turns and repeated travel on the same road segment. The optimal policy not only reduces the collection and transport cost, but also improves the tractor capacity utilization, assures equitable service for all residents and reduces the total time spent on waste collection, disruptions to traffic and carbon emissions.