Conference Agenda

Liner shipping networks are essential to today’s global supply chains, featuring cyclical, periodic services operated by container ships. This cyclical structure makes scheduling easier for both carriers and shippers. However, combining cyclical scheduling with fixed port time slots often leads to inefficient operations. We propose to relax the cyclical assumption and make these networks more flexible by allowing vessels to switch between routes seamlessly, improving efficiency without disrupting container flow. To shippers, the network still appears cyclical and periodic, while carriers can manage a more streamlined network. This change creates an optimization challenge that combines vessel routing and cargo allocation, resulting in complex problem scenarios. We tackle this problem using a metaheuristic approach and show with real-world data that such network flexibility can significantly lower costs compared to traditional fixed schedules.

In this paper, we study the problem of locating hydrogen fueling stations for zero-emission aquaculture vessels in Norway in the area of Lofoten and Vesterålen. We model the problem as location-routing problem considering both the location of hydrogen fueling stations and the routing of aquaculture vessels. The objective is to minimize the total costs while satisfying customers demand. The costs consist of investment costs in fueling stations and fuel costs related to the energy usage of the aquaculture vessels. We formulate the problem as an open route model with energy constraints considering vessels with limited range. A route is defined from an open fueling station to an open fueling station and each vessel can serve at most one route. Therefore, we include a post-processing matheuristic to determine the number of vessels needed to meet the demand. We further conduct a sensitivity analysis on a vessel range. The computational results show that a longer range does not necessarily lead to a lower number of opened fueling stations or a lower number of deployed vessels. However, it leads to structurally different solutions with lower fuel costs and hence lower total costs.

Next to the reduction of greenhouse gas emissions, there is already a necessity to remove released CO2 from the atmosphere to limit global warming. The so-called Negative Emission Technologies (NET) are using chemical and biological processes to remove atmospheric CO2 and store it in different mediums. One promising NET is Ocean Alkalinity Enhancement (OAE), which enables the ocean to absorb more atmospheric CO2 by increasing the oceans’ alkalinity. Thereby, alkaline minerals like limestone are dissolved in seawater to reinforce the natural chemical process of CO2 absorption. While OAE has already garnered significant attention, with studies exploring its feasibility, social and political acceptance, environmental impacts, risks, and costs, there remains the optimization of an OAE’s supply chain. In this talk, we present an optimization model for an OAE supply chain with the objective of minimizing the net present value of corresponding investments and operation costs. The model includes decisions on the extraction site of limestone, the production of the slaked lime at plants, as well as the required transportation and the final discharge of the material at sea using a fleet of ships. A lower limit for CO2 uptake is employed to regulate the emissions from energy and fuels for production and transportation. We present results from a Norwegian case study, examining the cost per sequestered ton of CO2. This approach demonstrates the potential for the future deployment of NET.