Ammonia emission factors for UK agriculture

Ammonia (NH3) emission inventories are required for modelling atmospheric NH3 transport and estimating downwind deposition. A recent inventory for UK agriculture, estimating emission as 197 kt NH3–N yr−1, was constructed using 1993 statistical and census data for the UK. This paper describes the derivation of the UK-based emission factors used in the calculation of that emission for a range of livestock classes, farm practices and fertiliser applications to agricultural land. Some emission factors have been updated where more recent information has become available. Some of the largest emission factors derived for each farming practice include 16.9 g NH3–N dairy cow−1 d−1 for grazing, 148.8 g NH3–N liveweight unit−1 yr−1 for housed broilers and 4.8 g NH3–N m−2 d−1 for storage of solid pig and poultry waste as manure heaps. Emissions for land spreading of all livestock waste were 59% of the total ammoniacal nitrogen (TAN) applied as a high dry matter content slurry and 76% of TAN applied as farm yard manure. An updated estimate of emission from UK agriculture, using updated emission factors together with 1997 statistical and census data, is presented, giving a total of 226 kt NH3–N per year.