Mixed Integer Linear Programming for CO2 emissions minimization in a Waste Transfer Facility Location Problem

In this work, we solve a real-world facility location problem by means of a mixed integer linear programming model. The problem is faced by an Italian multi-utility company operating in the sector of waste management. The company works in several Italian regions to collect and treat the urban waste through a network of facilities. In this problem, a set of demand points is given with a predicted quantity of waste to be collected and a fixed number of visits required over a predetermined time horizon. The flow of different classes of recyclable waste must be optimized by deciding whether and where to open additional intermediate transfer facilities among a set of dedicated points. The aim is to minimize the CO2 emissions involved in the process, including emissions from the use of additional facilities and the transport of waste across the network. We provide a mathematical formulation for the problem, and use it to solve a real-world case study. An optimal solution is obtained with a significant reduction in CO2 emissions and a well-structured network, proving the efficacy of the model.