Removing Urine

[Ikea]

The urine and compost could be replaced in saltpetre with ammonia and nitric acid. The way saltpetre is made in real life is with ammonium nitrate and potash. The ammonia can be made by botany with nitrogen from beans and hydrogen from balloon melons. Nitric acid would need to have a botany unique way of farming, personally what Id suggest is making another nitric acid recipe, something like (1) Sulfuric acid + (1) Saltpetre -> (2) Nitric acid (This is yet again another irl way to make a chem). Then, add a plant that produces sulfuric acid. This should make farming saltpetre really interesting, because you need saltpetre to farm saltpetre if youre doing it through botany. This would also promote interdepartmental cooperation for saltpetre farming, ammonia and nitric acid would probably be easier to make through a chemdispenser.