A full Hydrogen economy is crazy, but a lot more hydrogen makes a lot of sense.
How else do you store solar and wind power?
You had might as well run it through electrolyzers and make H2 and O2.
You can control NOx by using EGR. I have seen demos on a heat treatment furnace that used O2, H2, and CO2 in the combustion.
The water was condensed and the CO2 was recirculated.
And then there are fuel cells. When you don't have to make them light weight or crash resistant they are a lot less cost.
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P.E. Metallurgy, consulting work welcomed