Pure hydrogen will not be used as a clean fuel for intercontinental shipping due to its relatively poor energy density by volume, according to maritime standards firm DNV.

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In fact, pure H2 will barely play any role in the shipping industry’s 2050 fuel mix, losing out to biofuels, fossil fuels and hydrogen derivatives in all 24 of the scenarios modelled by DNV in its latest Maritime Forecast to 2050 report.

The most likely use of pure hydrogen as a maritime fuel will be in short-sea shipping, where vessels stay close to shore and do not travel long distances, said the Norwegian company.

But the use of liquid and compressed hydrogen will be so insignificant on a global level that DNV left it out of the report's fuel mix modelling illustration (see chart below) — another example of the growing consensus around pure H2’s unsuitability as a shipping fuel.

Liquid hydrogen requires cryogenic temperatures of below minus 253°C, making it difficult to handle and store at sea.

And compressed and liquid hydrogen have poor volumetric energy density of 1.2kWh and 2.4kWh per litre, respectively, meaning that huge storage tanks would be required to ship and burn it over long distances, in a setting where space is at a premium.

24 possible outcomes

In 24 scenarios that modelled clean fuel take-up against a variety of different variables — including the availability of carbon, the commercialisation of carbon capture and storage (CCS) technology, fossil fuel prices, sector decarbonisation ambition and access to renewable energy — DNV found that either fossil or drop-in fuels accounted for almost all of the fuel mix by 2050, ruling out widespread electrification of the global fleet, or other ship technologies such as sails or wave power.

Half of the 24 scenarios projected full decarbonisation, with the other half looking at the outcomes in the less ambitious International Maritime Organisation (IMO) Greenhouse Gas Strategy, which aims to cut greenhouse gas emissions in global shipping by 50% compared to 2008 levels by 2050.

DNV's 24 scenarios for the maritime energy mix in 2050. Photo: DNV

In a full decarbonisation scenario, biofuels, synthetic fuels made with biomass such as bio-marine gas oil (bio-MGO), bio-LNG and bio-methanol, took a sizeable share of the fuel mix across the board of variables.

But green hydrogen-derived fuels (labelled “electro-fuels” by DNV) such as ammonia, methanol, e-LNG or e-MGO make a contribution in scenarios where biomass or CCS availability is limited, or where renewable electricity is abundant and cheap.

And blue ammonia would win hands-down against e-fuels if CCS became widely available, the report said.

Only e-MGO, biofuels and green ammonia would make any headway under the IMO’s current Greenhouse Gas Strategy, DNV found, and only then if fossil-fuel prices remained high.

But all novel alternative fuels would have to contend with heightened safety considerations and nascent regulation, especially hydrogen, which has a high flammability rate, and ammonia and methanol which are both highly toxic.

And although DNV estimates that vessels powered by pure hydrogen and ammonia could be on the water within eight years — and currently there are three H2 vessels on order — “the lack of design guidance is complicating the building process for everyone involved”.