French industrial gases giant Air Liquide says it will build an industrial-scale ammonia cracking pilot plant at the port of Antwerp in Belgium to convert imported NH3 into hydrogen and nitrogen.

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Ammonia is widely expected to be the preferred molecule for importing large amounts of green hydrogen into Europe, as it easier to store and transport than compressed or liquefied H2 and also contains more energy by volume.

“A global supply chain infrastructure is already in place for [ammonia’s] production, transportation and utilization at large scale to serve various industries,” the company says in a press release.

“This allows regions with abundant renewable energy to export ammonia to end users across the globe, where it can be converted back to hydrogen to contribute to the decarbonization of industry and mobility.

The notion of converting imported ammonia back to hydrogen is controversial. Multiple studies have shown that the increased cost and efficiency losses from the energy-intensive process to “crack” NH3 into its constituent parts — which requires a catalyst and high-temperature heat — would inevitably result in very expensive hydrogen. In fact, 15% of the energy contained in ammonia would be required for the cracking process.

This has led to arguments that it would better to use imported ammonia as ammonia, ideally replacing grey NH3 made from unabated natural gas.

“It is economically more efficient to ship hydrogen as ammonia. There is however a cost penalty at the destination in converting ammonia back to hydrogen,” said an international shipping study published by the Tyndall Centre for Climate Change Research at the UK’s University of Manchester.

“Therefore, the best export markets for green hydrogen producers are likely to be those with direct uses of ammonia, such as in fertiliser manufacture — avoiding the need for reconversion.”

The Antwerp pilot project — which is planned to be operational in 2024, and has been promised financial backing from the Flemish government — will use a new “highly efficient” process invented by Air Liquide — “next-generation reactor tubes heat-integration technology”.

“This technology allows for the highest possible ammonia to hydrogen conversion yield and zero direct CO2 emissions,” the company says.

“With this cracking technology, Air Liquide will further contribute to the development of hydrogen as a key enabler of the energy transition.”

Several other companies have already announced plans to build ammonia crackers at European ports, alongside new NH3 import terminals.

Air Products announced a plan in November to build a large-scale green ammonia import terminal at the German port of Hamburg by 2026, and crack the NH3 back into hydrogen and nitrogen.

And both German utility Uniper and UK oil giant BP separately plan to build green ammonia import terminals at the port of Wilhelmshaven, 125km west of Hamburg.