The Rich Earth Institute is currently undergoing field trials of using urine to fertilize. They pasteurize it first to eliminate micro organisms. Urine contains most of the Potassium, nitrogen, and phosphorus we eliminate from our bodies. The main downside is it also contains most of our unwanted chemical residues (ie drugs and their metabolized components). Part of what REI is looking into is what is the plant take up rate of these things, and is it a health risk.