Maritime fleet composition under future greenhouse gas emission restrictions and uncertain fuel prices

This paper studies the maritime fleet composition problem with uncertain future fuel and carbon prices under the restriction of complying with future greenhouse gas (GHG) emission restrictions. We propose a two-stage stochastic programming model that can be adapted to two different variants of this problem. The first variant considers the Maritime Fleet Renewal Problem where there is an existing initial fleet to be renewed through scrapping and acquisitions, as well as retrofitting of ships in the current fleet. The second variant considers the Maritime Fleet Size and Mix Problem, where also the initial fleet must be determined. When applying the model to a fleet of Supramax bulk carriers as a case study, we find that LNG- and methanol-based power systems are favorable initial choices. Two different scenario sets, with 50% and 90% reduction restrictions by 2045, are investigated. Depending on the ambition level, retrofits towards ammonia can be cost-effective.