Optimisation of the construction and demolition waste management facilities location in Cantabria (Spain) under economical and environmental criteria

Construction and demolition waste (C&DW) constitutes a priority waste stream due to the large amounts generated and its high potential for reuse and recycling. Specific legislation has been developed for this type of waste at European, national and regional level. In order to fulfill this new legislation, it is necessary to settle down a network of recycling facilities for C&DW (processing plants (PP) and/or transfer stations (TS)). The aim of this paper is to identify the locations and capacity of the transfer stations and processing plants and the corresponding distribution network by means of an optimization model that minimizes: (1) medium transportation distance and (2) total costs (installation, operation and landfill). The model is formulated as Mixed Integer Lineal Programming (MILP) problem where the binary variables represent the presence or not of management facilities at a location. General Algebraic Modeling System (GAMS) is used as a modeling system for the resolution of the mathematical programs. The model has been applied to a real-life case in Cantabria, a northern Spanish region. Two approaches have been considered: (a) the region as a whole area and (b) the region divided in five geographical areas. The results show that when the total costs are minimized, the number of facilities decreases, and when the medium transport distance is minimized, the number of facilities increases. The proposed final network includes location of three PP and two TS, each one of these facilities located in one of the five geographical areas defined. The optimal results also determine the municipality where each facility must be located, the capacity of them and the distribution network.