Increasingly stringent emissions regulations and corporate renewability targets motivate the use of alternative fuels in ocean shipping. Marine diesel engines are an ideal starting point for renewable ammonia fueling due to steady-state engine operation, high pollutant emissions from heavy fuel oil, and the remoteness of open ocean operation. Prior research has demonstrated reduced fossil fuel consumption and CO2 emissions using ammonia-diesel dual fuel with thermo-chemical recuperation (TCR) in a diesel engine for off-highway vehicles. Power output and stability were unaffected by ammonia substitution, and unburned ammonia concentration in the engine exhaust was suitable for selective catalytic reduction (SCR) of nitrogen oxides. These benefits, plus additional pollutant emissions reduction compared to fuel oil combustion, are achievable for large ship-board diesel engines. This project will translate small-scale combined TCR/SCR reactor research to the marine engine scale through modeling and techno-economic analysis. Available data from prior research activities will be used to validate a thermochemical reactor model. Engine modeling will predict combustion and emissions behavior of large marine engine systems. Finally, life-cycle cost and benefits of the TCR system will be assessed based using a techno-economic analysis with data provided by commercial entities ranging from engine manufacturers to ocean logistics companies. This project will produce the prerequisite data for a pilot construction/demonstration of a marine-scale TCR/SCR reactor fueled with renewable ammonia.