Some would argue urine is not a waste product- more 'left over nutrients. But sorry, I was more pointing out the use of body fluids such as Some cultures do ingest urine for to treat disease- It was off topic so didn't go into details at the time- didn't mean to offend
I'd bet Bear Grylls would agree with you on that he's been known to drink his urine from time to time - properly filtered through his t-shirt too