Wärtsilä is pioneering the adoption of hydrogen and ammonia as viable engine fuels and has launched advanced testing in Wärtsilä’s fuel-flexible combustion engines. Since hydrogen and ammonia do not contain carbon, their combustion releases no carbon dioxide emissions. Full-scale engine tests have been recently carried out in Wärtsilä’s engine laboratory in Vaasa, Finland, to assess the optimum engine parameters for running on these fuels. The test results have been encouraging, with one test engine performing very well when running on a fuel with 70 per cent ammonia content at a typical marine load range. Tests were also completed successfully on another engine in pure hydrogen operation. Testing will continue throughout the coming years with the aim of defining the most feasible internal combustion engine-based solutions for power plant and marine applications, thereby enabling the transition to a decarbonised future with green fuels.