Research on sustainability performance has considerably enriched operations management literature in recent years. However, work with quantitative models is still scarce. This paper thus contributes to revisit classical inventory models by taking sustainability concerns into account. We believe that reducing all aspects of sustainable development to a single objective is not desirable. We thus reformulate the classical economic order quantity model as a multiobjective problem. We propose to refer to this model as the sustainable order quantity model. Then, a multi-echelon extension of the sustainable order quantity model is studied. For both models, the set of efficient solutions (Pareto optimal solutions) is analytically characterized. These results are used to provide some insights about the effectiveness of different regulatory policies to control carbon emissions. We also propose an interactive procedure that allows the decision maker to quickly identify his / her best option among these solutions. The proposed interactive procedure is a new combination of multi-criteria decision analysis techniques.

Abstract:Intermodal transportation is often presented as an efficient solution for reducing carbon emissions without compromising economic growth. In this article, we present a new intermodal network design model in which both the terminal location and the allocation between direct truck transportation and intermodal transportation are optimized. This model allows for studying the dynamics of intermodal transportation solutions in the context of hinterland networks from a cost, carbon emissions and modal shift perspective. We show that maximizing the modal shift is harmful for both cost and carbon emissions and that there is a carbon optimal level of modal shift. We also show that even if transportation cost and carbon emissions share the same structure, these two objectives lead to different solutions and that the terminal is located closer to the port when optimizing cost and further away when optimizing carbon emissions. The model also allows for studying the tradeoff between distance and volume, the impact of using aggregated models for estimating train transportation cost and carbon emissions as well as the potential policy measures that enable aligning cost and carbon emissions.

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D espite the many advantages of containerization for goods transportation, the management of empty containers is a major disadvantage, driving costly repositioning operations. We investigate the potential for consignees to manage an inventory of empty containers at their location so as to enable direct reuse of these containers by consignors located in the surroundings. One difficulty is that the detention fees imposed by shipping companies under merchant haulage are nonlinear. Moreover, cleaning and related activities might be necessary if the consignee keeps some empties. These difficulties incentivize consignees to immediately return containers to the sea terminal. Contrary to this practice, we show that managing containers via time-based threshold policies can save costs. Without cleaning costs, we prove that a time-based policy with a timeout return time is optimal. We next develop a policy improvement approach to include the cleaning costs in the analysis. This results in a two-thresholds time-based policy where the two time thresholds control the admission into and rejection out of the inventory. We next analyze the impact of this proactive management on the level of direct container reuse. This practice enables a high level of direct reuse. It also reduces container repositioning costs. Yet, the incentive to implement our policy varies a lot from one setting to another. In particular, low cleaning costs or high repositioning costs lead to significant costs improvement when implementing our policy. Finally, we further explore if the incentive could be made stronger by modifying the structure and/or purpose of the detention costs.

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