I've read that back in Medieval times they would use lant (old urine) in baking and as a cleaning solution. It contains urea (check out your shampoo bottle lable) and ammonia.
Just another one of my 10,000 reasons why I'm glad I didn't live back then.
I forget the specifics, but I remember my Latin teacher telling the class how the ancient Romans used to collect urine in vats to make ammonia for cleaning their wool togas.