Unlikely Causes of Acid Rain, Part 94: Ammonia

From The Metro: Cows and sheep release 37 per cent of the world's methane, which is 23 times as warming as CO2....  Yup, that would appear to be true. Livestock also produce more than two-thirds of the world's ammonia, one of the main causes of acid rain... Jeez, I don't remember much from my O-Level chemistry, but that doesn't sound quite right to me.  Let's check at Wiki: Ammonia is moderately basic, a 1.0 M aqueous solution has a pH of 11.6...   Righty-ho.