Improving Efficiency and Sustainability of the Tramp Shipping Industry: Operational, Strategical, and Tactical Mathematical Programming Models

This PhD thesis examines operational, strategical, and tactical mathematical programming models to improve the efficiency and sustainability of the international shipping industry, specifically of the tramp shipping segment. Indeed, the shipping industry is responsible for nearly 3% of the anthropogenic emission, and its increasingly releasing more greenhouse gasses into the atmosphere. To reverse this tendency, explicit countermeasures are necessary. Nevertheless, the process of introducing regulations to limit the emission proceeds with sporadic and sometimes inadequate advancements.

The slow and uncertain development of international regulations is reflected on the international shipping industry, which considers a spontaneous selfdriven transition too risky to take any initiative. Consequently, at the moment (year 2025), the shipping industry has not started its sustainable transition except for minor improvements. Conversely, the shipping industry is alarmed by the costs that transitioning will imply, and therefore reduce the industry profits. Furthermore, the returns reduction may negatively impact the shipping capacity to attract external investors.

To mitigate the uncertainty and estimate the transition costs, we investigate the initiatives that shipping companies can adopt in the short, medium, and long-term through mathematical programming models and efficient solution methods. One scope of the mathematical models is to support shipping operators decisions to improve the daily operations and wisely select how to reduce their environmental impact. At the same time, the same mathematical models can be used by international regulators to assess the proposals effect in terms of costs for shipping operators and achievable emission reduction.

The analysis of the short and medium-term initiatives is conducted by modeling operational and tactical aspects. The achievable emissions reduction is studied through an emission-aware routing model, where the model discovers different trade-offs between profitability and sustainability. This creates the possibility for operators to choose the preferred balance. In addition, the model is studied in presence of technological updates of the vessels such as the installation of sails propulsion or the retrofit to liquefied natural gas.

The analysis of the medium to long term measures is conducted by modeling strategical, tactical, and operational aspects. The emission reduction have been studied in presence of different emission reduction schemes, such as a carbon levy, explicit constraints on the allowed emission, and an emission trading system. The modeled shipping operator complies with the emission reduction schemes by using different fuels, retrofitting the fleet, and improving the operations.

The experimental studies contained in this thesis demonstrates that it is possible to substantially reduce the emission of the shipping industry with low cost, and with potentially increased profit, for the shipping operators. Large emission reduction can be achieved at moderate cost. Nevertheless, reaching the carbon neutrality of shipping will require a higher cost. However, the timely and progressive transition mitigates the cost.