Dynamic multi-period recycling collection routing with uncertain meterial quality / Daniel Cuellar-Usaquén, Marlin W. Ulmer, Oliver Antons, Julia C. Arlinghaus

Abstract

We consider a problem of collecting and processing waste material. At a production facility, every period, a known amount of inventory is required for production (e.g., paper). Instead of new material, the facility relies on collected and processed waste material (e.g., paper waste). This material is collected from regional waste collection locations. The amount of waste material per location is uncertain, as is the quality of the collected waste, i.e., the resulting inventory when processing the material. If the inventory at the end of a period is insufficient, costly new material has to be bought. Each period, decisions are made about how much waste material to collect from which location and how to route the collection vehicles accordingly. Ideally, inventory is built to hedge against quality uncertainty and to ensure efficient routing operations in future periods. We propose a stochastic lookahead method that samples a set of scenarios and solves a simplified twostage stochastic program in every period. We show the value of our method for two case studies, one based on real-world data from Sachsen-Anhalt, Germany, and one from the literature with data from the United Kingdom. We further conduct a detailed analysis of our method and the problem characteristics.