Current greenhouse gas emissions (GHG) from maritime transport represent around 3% of global anthropogenic GHG emissions. These emissions will have to be cut at least in half by 2050 compared to 2008 as adopted by IMO´s initial GHG-strategy to be consistent with the Paris Agreement goals. Basically, the required GHG emissions reduction can be achieved through: Design and other technical improvement of ships; Operational Improvement; Fuels with zero or lower GHG footprint; or a combination of these. Fuels with zero or lower GHG footprints are often perceived to be the most promising measure. The motivation for this study has therefore been to investigate these alternative fuels with focus on their feasibility, energy utilization and cost in addition to their GHG reduction potential. The results indicate: First, that fuels with zero or very low GHG emissions will be costly; Second, that these fuels might double or triple the maritime sector's energy consumption in a Well-to-Wake context; Third, if large amounts of renewable electricity becomes available at very low prices, synthetic E-fuels such as E-diesel and E-LNG which can be blended with conventional fuels and used on conventional vessels, will be more commercially attractive than hydrogen and ammonia.