The overall aim of the Ammonia2-4 project is to demonstrate at full scale two types of dual fuel marine engines running on ammonia as main fuel: (i) a four-stroke and (ii) a two-stroke engine. The proposed four-stroke innovation is a newbuild 10MW engine to be demonstrated in lab conditions closely mimicking real-life operations in ambient conditions. The proposed two-stroke innovation is a medium-pressure ammonia fuel injection platform that can be retrofitted onto any two-stroke marine engine available in the market today. It will be demonstrated in the project at two stages: a lab demonstration followed by retrofitting onto a container vessel of the alpha customer MSC. Both engine innovations are expected to result in at least 80% less GHG emissions (including nitrous oxide emissions), NOx emissions below IMO Tier III regulations and a negligible ammonia slip below 10ppm. By demonstrating both engine types at full scale the project partners are aiming for commercial exploitation of the project results towards more than 90% of the maritime intercontinental transport in terms of gross tonnage, including retrofits and newbuilds to enter the fleet within the next ten years. It is expected that both Ammonia2-4 innovations will lead to an annual reduction of CO2 emitted by deep sea vessels calling at EU ports by 2.3 million tons, and reduce the emissions of harmful pollutants such as SOx by 15 tons annually.