This is a really interesting idea and the unit economics are great. However when I researched this (or rather Gemini 2.5 Pro researched this) the problem appears that Haber-Bosch produces ammonia, whereas Birkeland-Eyde produces nitrate, which then needs to be converted in nitric acid. Getting from nitric acid to ammonium nitrate (which dominates the fertiliser market) needs ammonia from somewhere, which destroys the economics.
However calcium nitrate, potassium nitrate production via B-E looks really interesting.
However calcium nitrate, potassium nitrate production via B-E looks really interesting.