A bi-objective model for the used oil location-routing problem

A staggering amount of used oils (e.g., 1.4 billion gallons in the U.S.) are generated annually as part of our industrial lifestyle. These are harmful to the population and environment in the vicinity of the transport routes as well as the storage, treatment and disposal facilities. In this paper, we provide an analytical framework to simultaneously answer the following questions: Where should the used oil storage, treatment and disposal facilities be located? What are the most appropriate capacity levels for these facilities? Which routes should be used among the different echelons of facilities in the used oil collection network? Focusing on the hazardous ingredients of used oils that are airborne on release, we propose an environmental risk measure by incorporating the Gaussian plume model in the box model. We present a bi-objective model for the location-routing problem so as to minimize the total environmental risk and the total cost. We use a modified weighted goal programming approach, which proved to be computationally efficient through a wide range of tests. The application of the proposed analytical framework in Chongqing of Southwest China provided interesting managerial insights.