This is an interesting paper. I had read about recycling cow urine in dairies[1] and I wonder if the yeast would be able to make hydroxypatite out of it. At the time I came across this paper I was looking at people creating financial incentives to produce ammonia (and ammonium nitrate) at scale for farming. We import a bunch of it[2] and making it locally would be a win/win.
[1] https://www.sciencedirect.com/science/article/abs/pii/B97801...
[2] https://wits.worldbank.org/trade/comtrade/en/country/USA/yea...