An Assessment of Alternative Fuels for Ocean-Going Deep-Sea Vessels: A Case Study in IMO Maritime 2050 GHG Emission Reduction Targets

The International Maritime Organization (IMO) committed at the 2015 Paris Climate Summit to reducing greenhouse gas (GHG) emissions from shipping. Many studies and classification society outlooks agree that meaningful decarbonisation of deep-sea shipping will require a shift to low- or zero-carbon fuels. This research systematically evaluates three leading alternative fuels—hydrogen, ammonia, and methanol—regarded as capable of helping the sector meet the IMO’s 2050 targets. Each fuel was assessed using technical, environmental, economic, and social criteria through a hybrid multi-criteria decision analysis (MCDA) approach combining the analytical hierarchy process (AHP) and TOPSIS (Technique for Order Preference by Similarity to Ideal Solution). Criteria weights were derived from an online survey of 57 maritime experts, while secondary data from existing literature informed the TOPSIS analysis. AHP results show that environmental performance is the most important factor in fuel selection, followed by technical, economic, and social considerations. The combined AHP and TOPSIS results show that ammonia is the most suitable alternative fuel to reach IMO 2050 goals. This study’s findings provide a structured and evidence-based comparison of the main deep-sea alternative fuels and offer practical guidance for maritime decision-makers seeking to identify the most suitable option for decarbonising their fleets in line with global GHG reduction goals for 2050 and beyond.