Japanese industrial and shipbuilding companies have announced a breakthrough in hydrogen propulsion. The project is led primarily by Japan Engine Corporation and Kawasaki Heavy Industries, and is being carried out under a program backed by the government agency NEDO (New Energy and Industrial Technology Development Organization), with participation from Mitsui O.S.K. Lines (MOL), MOL Drybulk, Onomichi Dockyard, and ClassNK.
What matters here is the scale. The tests were conducted on a full-size engine, which gives a much clearer picture of how this technology could work in real maritime operations. Until now, hydrogen had mostly been used in smaller systems or demonstration projects, not as the main propulsion unit for large vessels.
The new engine is based on a modified version of a conventional combustion design, adapted to burn hydrogen instead of fossil fuels. During testing, it achieved more than a 95% hydrogen share in the fuel mix at full load, while maintaining stable operation across all cylinders. That kind of performance could significantly reduce CO₂ emissions in shipping, a sector responsible for a meaningful share of global emissions.
The technology has faced several major hurdles. One of the biggest has been handling hydrogen safely – it is highly flammable and difficult to store. There have also been challenges around combustion efficiency and adapting existing engines to run on a new fuel without losing power or reliability.
Infrastructure remains an open issue. Transporting and bunkering hydrogen at scale in ports is still at an early stage, which limits near-term deployment. On top of that, the cost of producing “green hydrogen” is still high compared to conventional fuels.
Even so, these tests suggest the technology is moving beyond the experimental phase. Running a large marine engine under controlled conditions is a meaningful step forward and could help accelerate wider adoption.
A shift to hydrogen could bring clear benefits – lower emissions, the option to use renewable energy, and in some cases the ability to adapt existing engine designs rather than build entirely new systems from scratch.