A loop where solar is converted to fertiliser using similar process , probably generating hydrogen as a side effect with some mechanism to probably capture some carbon for economically useful use when it reaches say an LCOE of 0.01 $/kwh and done on mind boggling scale might actually be the holy grail solution to a lot of problems at the same time. Might need quite a few breakthroughs in the material science scheme of things though. There are good reasons why hydrogen has never really taken off by itself even with so much scale, innovation thrown at it so far. The best hope is China doing to hydrogen now what it did to solar in 2010s.