Right, there's NO putrefaction going on. The uric acid is changing to ammonia.
I haven't boiled urine yet, but my memory is that one should boil urine that is already aged to concentrate it more. Not many sources talk about boiling urine actually. It's not part of most people's protocols. It may have its purpose, but I don't know what it is.
When we drink fresh urine, the uric acid changes also into a scant amount of ammonia, which is part of its anti-pathogenic effect in the body. But the liver changes most of it into glutathione, which helps the liver stay on top of detox, and reduces autoimmune problems etc.