Strategic Optimization of Waste Management Networks

We consider the problem of optimally allocating the flows of waste to a network of plants and disposal sites. More precisely we are given a set of sources, where wastes of different types are collected and a set of intermediate treatment plants (e.g., separation, composting, incineration, modal transfer) and of disposal sites, each able to handle a given subset of waste types and with known treatment capacity and fixed and variable costs. Plants may be existing or potential ones. For each link connecting sources or plants we also know the unit transportation cost for each waste type. The problem requires the determination of a min-cost set of plants to be used and the corresponding allocation of flows to links and plants that allows for the transfer of all the waste from sources to disposal sites. Several additional constraints may arise as those connected with the energy production at plants. In addition the problem can be extended so as to consider complex multi-period scenarios in which the evolution of an existing network is properly modelled. In this talk we describe the application of optimization methods based on integer programming models to the real-world case of waste flow allocation at HERA spa.