The current path the marine industry is following, the goals of the Paris Agreement to reduce emissions, will not be met. The marine industry is mainly sailing on HFO and emits 2.2% of the global greenhouse gasses (GHG) by doing so, as well as 18-30% of NOx, 5-8% SOx and 11% particulate matter (PM). The IMO has even predicted that the emissions of GHG will increase between 50 and 250% if the shipping industry continues on this path. In order to reduce emissions, the International Maritime Organization (IMO) has implemented ambitious goals for the next decades. However, the current policy measures sparks low ambition to meet this IMO GHG strategy. To be able to meet this goals, four options with different potential of reducing emissions are available, viz. efficient ship hull designs (20%), energy efficient engines (10-15%), more efficient propulsion (5-20%), clean technologies such as fuel cells and the use of alternative fuels (100%). Since the alternative fuel option has the largest potential in reducing emissions, a number of researched have looked into possible options for alternative fuel, such as LNG, LPG, methanol, biofuel, hydrogen and ammonia. This thesis looks into the potential of ammonia as an alternative fuel in the marine sector by 2030 by looking into the critical success factor for the fuel. This research takes all the aspects of the marine industry into account and researches the mutual interaction and relation between the aspects. The main aspects are the power generation options, the fuel availability including the port logistics, price of the fuel, operations (OPEX), impact on the vessel (CAPEX) and legislation and rules. These aspects have a number of inter-dependencies. The barrier related to the power generation option is the lack of availability of an engine that can run on ammonia. This engine needs to comply with legislation, which is not implemented yet. The barrier related to the fuel itself is the availability of the fuel in both volume and location. The production capacity is not yet at a level to fuel a significant part of the marine sector. The barrier related to the port are the logistics of the supplier and storage and handling of ammonia. Ammonia is a toxic substance and requires safety measures. These rules have not been implemented either. Closely related to the availability of the fuel is the price of the fuel. This is dependent on the demand of ammonia, which is currently zero for the marine sector. For the operational aspect is the lower energy density compared to conventional fuel an important barrier. For the same energy output, a greater volume of fuel is needed. This requires either extra stop overs during the voyage or a larger fuel tank, which could lead to loss of cargo space. The larger fuel tank has an impact on the design of the vessel, as well as the different storage and handling of ammonia compared to conventional fuels. Together with the legislation, this is an important barrier for the CAPEX of the vessel. This is a very important decision factor for the ship owner. Finally, most important barriers is the legislation. This aspect has the largest influence on all the other aspect and can promote other aspects to invest in ammonia and take steps in implementation. The regulation for sailing on ammonia are not yet in place. The IMO is responsible for the IGC and IGF code that regulate fluids as cargo and as fuel. The IMO has not started working on implementing ammonia as a fuel yet, since the demand of the fuel is currently low. This is however due to the regulations not yet being in place. Ship owners are reluctant to switch to another fuel when the risk of implementing the rules incorrectly are too large. The design requirements are not yet clear and it would be too costly to refit a vessel to the correct requirements for the early adaptors. Another aspect the regulations have large impact on are the engine options. Ammonia has a narrow flammability and is more difficult to ignite compared to conventional fuels. The design of the engine needs to comply with the regulations for safe ignition.