Urea: ‘Cow urine contains urea, a nitrogen-rich compound that, when broken down by enzymes in cow faeces, is converted into ammonia. Bacteria in the soil, in turn, convert that ammonia into nitrous oxide. Best known as a dental anaesthetic, the stuff is also a potent greenhouse gas. And agriculture is a big source of it. In the European Union, livestock farming accounts for around 70% of ammonia emissions,’ (How to toilet train your cow’, The Economist: 18th Sept 2021, p.70).