The cost of innovative and sustainable future ship energy systems

The latest guidelines approved by the environmental protection committee of the international maritime organization (IMO) will require the shipping sector to reduce its greenhouse gas (GHG) emissions by 50% before 2050 and achieve a complete decarbonization by the end of the century. This will require a major change in the way ships are built and operated today. In this paper, we aim at understanding what types of ship energy systems and fuels will be preferable and what will be the costs to achieve the environmental goals set by IMO for shipping. To do this, we approach the question as an MILP problem, with increasingly stringent constraints on the total GHG emissions and with the objective of minimizing the total cost of ownership. We apply this analysis to three ship types (a containership, a tanker, and a passenger ferry) and we determine what type of choice for the ship’s energy systems will be the most optimal, for each ship type. The results show that the most cost-effective pathway towards the elimination of GHG emissions is composed of a first phase with LNG as fuel and with an increasing use of carbon capture and storage, while the full decarbonisation of the shipping sector will require switching to hydrogen as fuel. These results depend only marginally on the type of ship investigated and on the type of regulation enforced. While the costs required to achieve up to 75% GHG emission reduction are relatively similar to the baseline case (50-70% higher), moving towards a full decarbonisation will require a cost increase ranging between 280% and 340% higher than the business as usual