A while back, I wrote about ammonia; and one of the critical chemical precursor is hydrogen. Historically, the focus of ammonia was about getting the nitrogen in a form usable and useful for making fertilisers. The fact is that nitrogen is plentiful in the atmosphere but it needs to be extracted.
The Haber-Bosch process allows for this atmospheric nitrogen to be extracted using hydrogen, producing ammonia or ammonium salts. These chemicals are then more easily transformed into fertilisers. The hydrogen part of the equation had never been considered a challenge so to speak. While it was rare on its own and not the most stable of gases, it was abundant in fossil fuels combined with carbon dioxide. So practically all the ammonia in the world is produced using hydrogen extracted from fossil fuel.
Extraction can be through steam methane reforming of natural gas (grey hydrogen); or gasification of coal (brown hydrogen). All of these processes emits carbon dioxide. In fact quite a bit of them. Not a problem when you’re producing a small amount of ammonia and primarily targeting agriculture rather than using ammonia as a source of fuel. But a big problem when you’re trying to get away from carbon as an energy vector.
So there’s low-carbon based hydrogen. They come from largely electrolysis of water using renewable electricity (green hydrogen). And if you capture the carbon dioxide from those traditional pathways mentioned above, then you get blue hydrogen. These color codes and names are from McKinsey and a shorthand to describe the carbon intensity of the hydrogen production. Useful for layman, not so much for the people in the industry since the actual carbon intensity is not exactly clear.
Nevertheless, it is interesting that because we are now increasingly looking at hydrogen as an energy vector, ammonia becomes a fuel again. It is being explored for a variety of energy applications: as a maritime fuel being combusted in ship engines, as a co-fired fuel with coal in the coal power plants, as well as a co-fired fuel with natural gas in a gas turbine. All of these allows the coal or gas power plants to continue running with lower levels of carbon emissions and allows them to be utilised through their economic life, and continue servicing the loans rather than becoming stranded assets.
So hydrogen seems really important in the low carbon economy. Yet it is not taking off. Stay tuned to understand the bottlenecks and challenges.