Hydrogen transport: All in on Ammonia?

Why ammonia?

The chemical formula of ammonia (NH3) suggests it: In an ammonia molecule, there are three hydrogen atoms for every nitrogen atom. This means that large quantities of hydrogen can be transported in comparatively small volumes of ammonia. In addition, the gas can already be liquefied at >8 bar or <-33 °C - i.e., with significantly less energy input than is required for the liquefaction of pure hydrogen.

Ammonia has an advantage over newer substances such as LOHC in that it is one of the most produced chemicals in the world: 185 megatons (Mt) were produced worldwide in 2020, according to Hydrogen Europe. Fertilizer producers are the largest customer. So global trade in ammonia is already happening on a large scale; countless producers could ramp up their production if demand increases. 

And what is missing from "NH3"? That's right, "C." Unlike alkanols such as methanol, ammonia does not contain carbon and therefore does not run the risk of emitting additional greenhouse gases into the atmosphere. Nevertheless, its production is not environmentally friendly.

How fossil-free is ammonia?

In 1908, the Haber-Bosch process, which is still used today, was patented; it has been carried out on an industrial scale since BASF was founded in 1913. In the Haber-Bosch process, hydrogen is converted into ammonia with nitrogen from the ambient air at high heat and pressure. The process has been optimized over decades and is considered extremely energy-efficient. Nevertheless, it is a source of CO2, which is due to hydrogen of all things: Today, this is generally still gray, meaning it comes from the classic steam reforming of fossil fuels. 

In order to remedy this situation, many manufacturers have been using plants for the production of "green ammonia" for some years now. The term simply means that the hydrogen for ammonia synthesis was produced without CO2 emissions. In other words, ammonia can only be called fossil-free if it is made from green hydrogen. From this point of view, therefore, a market ramp-up of green hydrogen would also be a way of driving forward the decarbonization of ammonia production. 

Example 2: Ammonia reforming in the port of Antwerp

What do ammonia reformers look like today? Many plants are still at the project stage, with new ones being added regularly. By their very nature, they are usually located near major ports. In mid-March, the French gas company Air Liquide announced that it would build a pilot plant for reforming ammonia on an industrial scale in the port of Antwerp. This will involve the use of a new type of technology.

The so-called "ammonia cracker" – it would be the first plant of its kind in Belgium – is expected to emit less CO2 by using more efficient technology. The pilot plant, which combines the novel process with proprietary technologies, is expected to be operational as early as 2024. The Flemish government has pledged financial support for the project through VLAIO (Flemish Agency for Innovation and Entrepreneurship).

Conclusion

Ammonia has potential. As is often the case, however, the "ifs" must be considered: Next to high-pressure pipelines, it is arguably the most promising medium for hydrogen transport at present, if it is derived from green hydrogen, if transport is safe and environmentally sound, and if both synthesis and recovery are energy efficient.

The biggest advantage is probably that ammonia can be produced wherever green hydrogen is also produced in large quantities, for example in sun- and wind-rich, remote regions such as the deserts of North Africa. From here, it can then be transported comparatively easily by ship to Europe and elsewhere. If efficient cracking plants are then available in the ports, it can be quickly cracked again there so that the hydrogen can then be transported quickly and inexpensively - via a pipeline network that has yet to be built - to industrial consumers.

At the end of May, the Port of Rotterdam investigated how much ammonia could be converted there in perspective. The answer: 1 million tons – per year. The study concludes that ammonia is a "realistic and safe method for large-scale hydrogen transports", and that a central cracking plant on the port site is more efficient than several decentralized ones. 

The fact is: if the hydrogen boom also leads to an ammonia boom, companies would be well advised to look into the relevant technologies in a timely manner.

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