MULTI-ECHELON DYNAMIC CAPACITATED FACILITY LOCATION PROBLEM FOR THE RECOVERY OF WASTE


Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Industrial Engineering, Turkey

Approval Date: 2015

Student: İSTENÇ TARHAN

Supervisor: FATMA SEDEF MERAL

Abstract:

Waste Electrical and Electronic Equipment (WEEE) Directive became a European Union Law in February, 2003. Turkey introduced an akin regulation in May, 2013 to give original manufacturers of electrical and electronic equipment the responsibility of making provisions for the collection and recovery of wastes. Due to the lack of existing infrastructure for recovery, studies related to recovery networks are supposed to increase in Turkey following the relevant regulation. In this study, we formulate a mathematical model for the dynamic capacitated facility location problem with two-echelons consisting of collection, consolidation and disassembly centers. The proposed model determines the locations and opening times of the centers, expansion of capacities as well as the transportation of returns from collection centers to disassembly centers through consolidation centers. Since the proposed model is difficult to be solved in reasonable times, we develop a heuristic approach decomposing the original problem into subproblems by the rolling horizon approach and invoking Lagrangean relaxation and variable neighborhood search in each subproblem. After solving all subproblems deriving from the rolling horizon approach, the original problem with the reduced solution space is solved the solution of which is the final solution of the proposed heuristic. The proposed heuristic approach is tested on a set of problems that we generate. The computational results show that the commercial solvers can be time-consuming even for moderate size problems whereas the proposed heuristic can find solutions for large scale problems with a reasonable optimality gap in much less time than the commercial solvers.