Optimization of Construction and Demolition Waste Management: Application to the Lisbon Metropolitan Area

Abstract

This work presents a mixed integer linear programming (MILP) model of a construction and demolition waste (CDW) recycling network that includes a methodology for environmental impact assessment (Eco-indicator 99). Applied to a geographical area, this generic formulation can be used for feasibility studies and sensitivity analyses of the input parameters, while simultaneously defining the optimal network design, i.e., the location and capacity of the installed facilities and material flows. Furthermore, by using the ε-constraint methodology, the Pareto Front is drawn, allowing the decision maker to choose the solutions presenting the best tradeoff between economic and environmental goals.

The model was applied to a Lisbon Metropolitan Area case study, which required extensive data collection and estimation. Different instances of the problem were generated, by varying conditions and model parameters (sensitivity analysis), and the MILP model solved. Solutions comprise a small number of high capacity recycling plants, when cost minimization is at stake, while when preference is given to the minimization of environmental impacts solutions comprise several geographically dispersed recycling plants of low capacity.