Reaearch On The Two-echelon Location-routing Problem For Biomass Logistics Systems

In recent years,biomass resources have been fully utilised as an important renewable energy source that can help achieve sustainable development,and have attracted considerable attention from researchers and industries.However,owing to seasonal variations,spatial dispersion,low density and other biomass resource characteristics,inefficient biomass logistics systems will hinder the development of biomass utilisation during the transportation process.Therefore,research on the optimization of biomass logistics systems is of great significance.In the biomass logistics systems,biomass resources require two transportation processes from the source of materials,through the collection facilities,and then to the biorefinery.If the primary and secondary deliveries are not integrated as a whole,low efficiency and higher logistics cost are the results.Therefore,this paper combines two important strategic decision problems in the biomass logistics system: facility location problem and vehicle routing problem,and studies a two-echelon biomass resource location-routing problem.The two-echelon biomass resource location-routing problem aims to minimize the total cost,which consists of the construction cost of collection facilities,the variable cost of collecting biomass,and the two-echelon unit transportation cost.Considering the certainty of the supply of biomass resources,a mixed integer programming model for the two-echelon biomass resource location-routing problem is established to determine the best locations and numbers for biomass collection facilities and two-echelon vehicle routes,to optimize the performance of the entire system with limited resources.Since the problem is NP-hard,a hybrid heuristic algorithm that embeds variable neighborhood search algorithm into the tabu search algorithm framework is developed.The exact solution algorithm by CPLEX and the hybrid heuristic algorithm are used to solve the model respectively and the effectiveness of the method is verified by a set of comprehensive calculation examples.Comparing the solution results of the hybrid heuristic algorithm proposed in this paper with the solution of the exact algorithm.The calculation results show that the algorithm effectively improves the calculation efficiency for large-scale calculation examples,and is more competitive in practical applications.