A British clean-shipping project has tested an integrated system designed to make hydrogen from seawater, store it at room conditions, and feed it into a heavy-duty combustion engine. The idea could help ferries, fishing boats, tugboats, and other working vessels cut direct carbon dioxide emissions, especially on routes where batteries are difficult to use.
Is the seawater really replacing diesel? Not by itself. Renewable electricity provides the energy, and the latest UK research record marks the funded project as closed without listing published performance results, so the technology remains a demonstrator rather than a proven commercial replacement.
Turning seawater into engine power
The project is called GH2DEM, short for Clean Maritime Propulsion via Direct Seawater Electrolysis and Ambient Hydrogen Storage. Genuine H2 developed seawater-compatible electrodes that are intended to produce hydrogen without first sending the water through a separate desalination plant.
The gas is then stored in what the team describes as a molecular nano-film at normal temperature and pressure. Brunel University of London’s heavy-duty hydrogen engine burns it for propulsion, creating an end-to-end chain from renewable power and seawater to usable mechanical energy.
Professor Xinyan Wang summed up the concept with a simple line: “Water will be turned into power,” he said, although the electricity doing the splitting remains the system’s true energy source.
Why the shipping industry cares
Shipping accounted for 2.89% of global human-caused carbon dioxide emissions in 2018, according to the International Maritime Organization. The IMO’s 2023 strategy also calls for zero or near-zero fuels and energy sources to provide at least 5% of international shipping’s energy by 2030, while striving for 10%.
That is why vessel operators are looking beyond conventional diesel. Battery-electric systems work well on some short routes, but weight, charging time, range, and limited space can make them harder to use on fishing vessels and workboats with long or demanding duty cycles.
Storage may be the bigger breakthrough
Making hydrogen is only half the problem. Ships must also carry enough of it without giving up too much deck or cargo space, and conventional systems often rely on bulky high-pressure tanks or cooling hydrogen to around -418°F.
GH2DEM’s proposed answer is a thin solid-state storage material that holds hydrogen at room temperature and pressure. In practical terms, that could simplify ship design and lower some handling risks, but only if the material can store enough fuel, release it quickly, and survive repeated cycles at sea.
The public UKRI and Brunel pages do not list capacity by weight or volume, cycle life, refueling time, or a comparison with a diesel tank of the same size. Those are not small details–they decide whether a clever storage concept can become useful equipment.
The public trial has ended
UK Research and Innovation lists the project’s funded period as August 2025 through March 2026 and now labels its status “Closed.” At mid-July 2026 exchange rates, the record shows about $1.45 million in public funding and roughly $1.92 million in combined project costs.
That label means the funded period has ended, not that the technology has necessarily succeeded or failed. Brunel’s October 2025 announcement said land testing would continue until March 2026, while the UKRI record currently lists no publications or final performance report.
The public material does not provide the hydrogen production rate, total system efficiency, continuous engine runtime, corrosion results, or an at-sea test date. A working engine on a university test stand is encouraging, but shipowners buy around fuel cost, maintenance hours, usable range, safety approval, and reliability in rough, salty conditions.
Cleaner exhaust still needs careful wording
Burning hydrogen does not produce carbon dioxide from the fuel because hydrogen contains no carbon. Still, a hydrogen combustion engine can form nitrogen oxides when high flame temperatures cause nitrogen and oxygen in the air to react, although lean combustion and emissions controls can reduce the problem.
The climate result also depends heavily on the electricity source. When renewable power runs the electrolyzer, the system can avoid much of the fossil carbon associated with diesel, but electricity from a carbon-heavy grid would weaken that advantage.
Direct seawater electrolysis has its own chemical headaches, too. Peer-reviewed research shows that chloride and other salts can corrode electrodes, trigger competing chlorine reactions, and reduce long-term efficiency, which makes durability testing especially important for a shipboard system.
Smaller vessels are the likely first market
Despite some sweeping headlines, the official project material focuses mainly on ferries, trawlers, tugboats, fishing fleets, and harbor service vessels. These are practical early targets because many follow predictable routes, return to familiar ports, and have demanding power needs that can expose the limits of batteries.
Onboard hydrogen production could also reduce dependence on a new network of hydrogen filling stations. But the vessel would still need a substantial supply of clean electricity, whether produced onboard, delivered in port, or stored in another form, so the system does not create free fuel from the ocean.
For operators, the business case comes down to one everyday question: does the full system deliver more useful range and lower lifetime cost than batteries, methanol, ammonia, or renewable diesel on the same route?
What needs to happen next
The next credible milestone is a verified marine trial that publishes energy use, hydrogen output, storage density, engine efficiency, nitrogen oxide emissions, and maintenance data. Regulators and classification societies would also need evidence that the production and storage hardware can withstand vibration, salt spray, leaks, collisions, and long operating cycles.
If GH2DEM meets those tests, seawater-derived hydrogen could become a useful option for parts of the maritime market. For now, it is better understood as a promising British engineering package, not proof that ships can simply pump in seawater and sail away without diesel.
The official project record was published on UK Research and Innovation’s Gateway to Research.
