An Integrated Location-Routing Framework for Multi-Type Urban Waste Collection and Recycling System

Urban waste collection and recycling systems face increasing operational and environmental challenges due to population growth, heterogeneous waste streams, traffic congestion, and the need for efficient resource recovery. This paper introduces the Sustainable Waste Integrated Facility and Transportation (SWIFT) approach for the design of multi-type urban waste collection and recycling systems. In the proposed system, waste generated at distributed collection points is collected by waste-type-specific vehicles and transported to intermediate consolidation facilities, where it is aggregated before being transferred to treatment plants using larger vehicles. The problem consists of jointly determining the locations of consolidation facilities and treatment plants, together with the associated two-echelon collection and transportation routes for multiple waste streams under a limited investment budget. To address this problem, an integrated location-routing optimization model is developed that simultaneously captures facility-location decisions, waste collection operations, transfer activities, and repeated unloading operations induced by vehicle-capacity limitations. The objective is to minimize the total system cost, including transportation, routing, and handling costs, while satisfying infrastructure investment constraints. Computational experiments based on realistic urban scenarios derived from the city of Medell\'in, Colombia, demonstrate the benefits of coordinated infrastructure and transportation planning. The results show that strategically located consolidation facilities can improve collection efficiency, enhance vehicle utilization, reduce transportation effort, and support more sustainable urban recycling operations.