A review by Jens Jakob Sigurdarson, Simon Svane & Henrik Karring. In agriculture, the formation of ammonia from urea occurs primarily in livestock buildings, manure slurry tanks, and when inorganic urea-based fertilizers are applied to fields. It has been estimated that 80.6% (39 Teragram (Tg) NH3–N) of global NH3 emissions in 2005 came from the agricultural sector with 34.1% of the emissions arising from manure management. Total anthropogenic ammonia emissions increased to 65 Tg NH3–N per year by 2008. In contrast total reactive nitrogen contributions from human sources were around 220 Tg N per year in 2010, which is roughly equal to the total reactive nitrogen fixed by biological sources.
A previous study has shown that the hydrolysis of urea in animal manure slurry is complete within approximately 20 h after the urine and feces are mixed, and, therefore most of the urine-derived urea is normally converted into ammonia before the manure slurry is applied to the fields!!! In most cases, ammonia will pollute air, while crops will not be able to use it.. .