Urine can be distilled to produce pure water.
Having seen the recommendations against the classic solar still due to its relative ineffectiveness, I have always wondered if introducing wet materials into the still would make it worthwhile. If you soaked some rags w/ urine, or chopped up some moist vegetation, would that make the solar still produce enough water to justify using it?
In Steven Callahan's book
"Adrift" he describes using 2 inflatable solar stills in which black cloth was soaked w/ seawater to generate the moisture. IIRC these stills were instrumental in his survival.