Using hydrogen for steel and fertilizer production are the only feasible use cases for it over the next 100 years at least, if your goal is maximum GHG reduction.

lolnope.

Nuclear. Every day, all day, conventional nuclear power is so much better than trying to invent a hydrogen infrastructure. An expensive infrastructure if it's going to perform those incredibly important base load purposes like smelting, chemical feedstock production (fertilizers) and concrete production that could be handled by existing infrastructure and nuclear power. I'm not even advocating for small modular reactors (which I think are nifty but ultimately unnecessary).

Hydrogen as energy storage and transport requires cryogenic everything, people don't realize how expensive and sensitive it is. Ben Rich talks about the Skunkworks program to produce Hydrogen in meaningful quantities for the Suntan program in Skunk Works, and the prospect of large scale hydrogen production (and use on active airfields) terrified people.

https://en.wikipedia.org/wiki/Lockheed_CL-400_Suntan

Basically, it can be done, but the risks are large without a highly trained workforce and rigid compliance to safety regimes.

Now imagine that but even more widespread :|