Ammonia as fertilizer is the only ammonia economy that makes sense; hydrogen economy doesn't make much sense either. Methane economy is the optional long-term

Ammonia as fertilizer is the only ammonia economy that makes sense; hydrogen economy doesn't make much sense either. Methane economy is the optional long-term solution for chemical energy sources, just CO2(atm) + H2 (water) -> CH4. Ammonia combustion generates NOx smog, and ammonia is pretty toxic to store and transport as a gas. For fertilizer it's stored as (NH4)(NO3) or similar. Hydrogen production has a few major use cases, but replacing natural gas is not one of them. Iron reduction, nitrogen reduction, carbon reduction, in industrial settings, is about it.