Carrying hydrogen to the finish line: comparing ammonia and LOHC

How do we realize the full potential of the symbiotic relationship that exists between the hydrogen economy and the energy transition?

In order for hydrogen to be the energy transition accelerant it is poised to be, hydrogen will need to go far – literally. Currently, the efficacy of scaling hydrogen beyond medium distance mobility faces immense logistical and practical challenges. To address this, we must turn to hydrogen derivatives as carriers. 

The Need for Carriers 

Why is there a need for hydrogen carriers such as ammonia and methanol? Hydrogen (compressed or liquid) has a lower volumetric energy density than its derivatives, leaving it comparatively volatile and more complex to store and transport. So, in the absence of affordable, efficient, and transportable containment methods for hydrogen, using its derivatives as carriers is an effective and stable alternative. For the purpose of stability and scale, derivatives are the essential carriers where hydrogen can be hooked, carried and then (where needed) cracked efficiently and safely. 

As energy carriers the two main candidates currently are LOHCs (Liquified Organic Hydrogen Carriers) and ammonia. LOHCs require hydrogenation and the de-hydrogenation steps of the organic carrier (and the carrier should not be used as direct fuel). In case of ammonia being cracked (dehydrogenated) back to hydrogen, of course the same applies, but unlike LOHCs, ammonia is composed of Nitrogen, an abundant carrier molecule that composes 78% of the air. Put another way, this is essentially free carrier storage in our atmosphere. 

The potential of direct ammonia usage

A not so hidden cost of using ammonia as a hydrogen carrier is the additional step needed to convert or “crack” it back into hydrogen. While this additional step can and will certainly be applied in specific use cases, it naturally presents the opportunity to explore the potential for direct uses of ammonia as it is. 

Direct use of ammonia to generate power is currently explored in Japan. Co-combustion of ammonia in coal-based power plants is being demonstrated, which as such is not a sufficient long-term zero emission solution, but a step to expand the already existing ammonia infrastructure (for de-NOx purposes) at these power plants. The Japanese technology roadmap is demonstrating the ammonia burners and ammonia CCGT turbines, and it will be a matter of time to make these technologies commercially available for Peaker Power plants in e.g. Europe as well, when power demand is higher than renewable electricity can accommodate. Ammonia burners could in the future also be applied to generate high temperature heat for furnaces and kilns in cement, brick and glass industry.

Infrastructure for “port”-able hydrogen

Where LOHC’s might use part of the existing logistic and storage infrastructure, there still would be a need for double transport and storage, given the leftover de-hydrogenated product. For ammonia, the existing storage terminals need to be scaled. For both carriers, the downstream hydrogen infrastructure needs to be developed. For smaller industrial hydrogen users this will be a case-by-case evaluation, though when thinking about larger (bio-)refinery and industrial sites the local hydrogen grid might require an upgrade.

When thinking of the European hydrogen backbone, cracking ammonia into hydrogen might be the only option at scale to fill this infrastructure, since low-carbon cracked ammonia has an economic benefit over scarce locally produced renewable hydrogen.

This is perhaps why the Port of Rotterdam and some German ports are exploring the feasibility of large-scale ammonia crackers (land or floating), as a next step to new ammonia import terminal capacity coming on stream in these locations, as well as hydrogen pipeline construction and political approval. This would follow the ongoing engineering in Korea for a large-scale ammonia cracking expected to come on stream in 2027 — such as Approtium’s landmark project in Ulsan that is using Topsoe’s ammonia cracking technology, H2RETAKE™.

Final thoughts 

To say that scaling a hydrogen economy will require effective hydrogen carriers is not to ignore the simple fact that in the world of molecules, as it is in the world of electrons, the best application is also the most direct one. Evaluating the above with this in mind, when we have reached the molecules, the direct use of these molecules is the most efficient. This also holds for hydrogen. Hydrogen will find its place through compressed hydrogen, when volumes and transport distance can be accommodated. This will likely apply to trucking, ferries and local green hydrogen integrated with industry.

But the effective scaling of the hydrogen economy will nonetheless require its effective transport and storage. To me it is clear: the hydrogen economy will not happen without ammonia. Both molecules go hand-in-hand. Large scale production and transport of hydrogen is only possible when ammonia comes into the picture given it's suitability for energy-dense storage and transport.