[philipkglass]

If you can beat the HB and Ostwald processes, I say go for it.

You wouldn't try to beat those processes. You'd run them as usual but with hydrogen from water electrolysis instead of from steam-reformed fossil resources. Of course both levelized cost of renewable electricity and cost of running electrolyzers at low duty cycle need to decline significantly more before that could compete with the current status quo of cheap natural gas and no CO2 emission taxes.

Renewable ammonia made this way still seems more plausible for near-future commercialization than making liquid hydrocarbon fuels from renewable electricity and atmospheric CO2. Which is admittedly faint praise. The advantage that might eventually be significant is that it's easier to ship ammonia or simple derivatives of it from some remote but renewable-energy-resource-rich place, like windy islands, than to build electricity transmission lines.

[yuhong]

This reminds of the idea of a true urea/diesel hybrid (instead of just using urea as DEF). Of course, the diesel would have to be used first.