“Back in the days” they used to use stale urine as detergent. Apparently it works a treat.
Stale urine is just homemade ammonia.
Of course. It contains ammonia ... lots of it. Ammonia is basic, and as such cleans away fats and oils very nicely. In fact, if you recall your HS chemistry properly, you'll recall that reacting a base with a fat yields soap. Which, of course, dissolves right nicely in water.