This is a good regression to practices that were abandoned once the Haber Bosch process was discovered. Unfortunately, we've also started medicating ourselves more heavily in the intervening years. A urine reclamation system will need to remove hormonal pharmaceuticals from medicated persons' urine or else using it will wreak havoc on the local ecology [1].

[1] - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4213589/

This is a pretty neat idea.

I could see football stadiums making a killing on selling nitrogen, phosphorus and potassium to local farms.