It needs to be clean, undilute urine. I have never tried to make urine powder but if you do it right it should work. I would be scared I wouldn't do it right and it would take too long to evaporate and would break down before evaporating or if I tried to add some heat iwould add too much heat. Note how much volume it starts at so yo know how much to add back. the advantage of this over freezing it is the ability to store it at room temperature for an extended period of time. Evaporating it isn't going to clean it though.