Ammonia is the energy carrier of choice for many proposed gigawatt-scale, export-oriented green hydrogen projects around the globe.

Stay ahead on hydrogen with our free newsletter
Keep up with the latest developments in the international hydrogen industry with the free Accelerate Hydrogen newsletter. Sign up now for an unbiased, clear-sighted view of the fast-growing hydrogen sector.

But while the chemical’s relatively mature infrastructure for overseas transport has been raised as a point in its favour, there may be a coming shortage of vessels able to carry NH3 over the required distances.

The International Energy Agency reportedly estimates that around 175 ammonia tankers with capacity of over 80,000 cubic metres (capable of carrying around 48,320 tonnes of NH3) will be required year-round by 2030 in order to transport clean ammonia from production hubs to demand centres, compared to 40 such tankers of this size operating today.

Energy cargo tracking company Vortexa tells Hydrogen Insight that over the last two years, 114 unique vessels had loaded ammonia with a combined liquid capacity of around 3.12 million cubic metres (capable of carrying around 1.9 million tonnes of NH3).

Vortexa tracks that the total deadweight tonnage of these ships, which includes the weight of everything on the ship as well as cargo, was approximately 2.52 million tonnes.

For scale, Neom — the largest export-oriented project to reach financial close to date — plans to export 1.2 million tonnes of green ammonia. This would imply that more than half of the vessels that carried ammonia over the past two years would have to be contracted to this single project.

A report published by Hydrogen Europe titled Clean Ammonia in the Future Energy System is optimistic that existing ships could be used to transport the chemical.

There are around 200 LPG tankers currently in operation, with a typical storage capacity of up to 40,000 tonnes, that could carry ammonia at full refrigeration. And a further 1,200 LPG tankers and more than 600 LNG vessels could also be retrofitted to transport NH3, the report suggests.

However, even if very large gas carriers (VLGCs) are repurposed to carry ammonia, competition for these vessels to carry other types of liquefied gas will almost certainly continue in the short term due to high demand for fossil gas in Europe and Asia.

And while VLGCs generally take around two or three years to build, expanding the fleet depends on shipbuilding capacity — which is already 40% lower than it was a decade ago. Research by Clarksons published at the beginning of the year indicates that only 131 shipyards are currently active.

Is it safe to transport longer distances?

Ammonia is generally carried at shorter distances than those between some proposed megaprojects and their target markets.

Vortexa calculates that the average distance a vessel transporting ammonia travelled was 2,955 nautical miles.

Some megaprojects’ distances from expected import markets are very close to this average.

The port of Noukachott in Mauritania — where multiple 10GW projects have been announced — is 2,780 nautical miles away from the port of Rotterdam.

Meanwhile the port of Hawkesbury in Nova Scotia in Canada — near to where Everwind Fuels is developing a green ammonia project capable of producing 200,000 tonnes in its first phase, with offtake already secured from Germany’s Uniper and E.ON — is a little over 3,000 nautical miles from Hamburg.

Germany and the Netherlands have also courted potential imports from Western Australia, but the ports of Dampier and Hedland are both more than 10,000 nautical miles away from potential import centres.

Green ammonia projects in the Middle East and North Africa would have to transport their volumes a less dramatic distance of around 4,000 nautical miles to European markets, with similar distances between Australia and ports in Japan and South Korea.

However, transporting "clean" ammonia over extremely long distances has already been demonstrated on a few vessels with no reported accidents.

Saudi Aramco first delivered a 25,000-tonne shipment of low-carbon ammonia, made in Jubail, to Ulsan in South Korea — a route of around 14,000km with just under 7,500 nautical miles between ports — in December 2022.

And a second 25,000-tonne shipment was shipped approximately 15,000km, or a little over 8,000 nautical miles between ports, to Japan in April this year.

The maritime industry is confident that increasing the amount of time spent at sea is unlikely to increase the risk of a serious incident.

“The International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) specifies strict requirements on the design of ships and on the materials that can be used to construct these ships in order to minimize the risk of ammonia leakages,” Sunil Krishnakumar, senior technical manager at trade association the International Chamber of Shipping tells Hydrogen Insight.

“Increasing the amount of time a ship spends at sea should not increase the risk of ammonia leakages as the IGC Code provides the necessary protection in all cases. Containment systems are designed for significant overpressures and any releases of ammonia as boil-off are controlled using technologies such as gas combustion units.”

The IGC Code also identifies ammonia as a toxic product, which prohibits its use as a fuel, which means that it would have to be revised if ambitions to use NH3 directly to power ship engines are to be realised.

As a results, some experts have warned that using ammonia as a maritime fuel in tandem with exporting large volumes, could increase the risk of accidents.