Ammonia and nitrous oxide emission factors for excreta deposited by livestock and land‐applied manure

Manure application to land and deposition of urine and dung by grazing animals are major sources of ammonia (NH3) and nitrous oxide (N2O) emissions. Using data on NH3and N2O emissions following land‐applied manures and excreta deposited during grazing, emission factors (EFs) disaggregated by climate zone were developed, and the effects of mitigation strategies were evaluated. The NH3data represent emissions from cattle and swine manures in temperate wet climates, and the N2O data include cattle, sheep, and swine manure emissions in temperate wet/dry and tropical wet/dry climates. The NH3EFs for broadcast cattle solid manure and slurry were 0.03 and 0.24 kg NH3–N kg–1total N (TN), respectively, whereas the NH3EF of broadcast swine slurry was 0.29. Emissions from both cattle and swine slurry were reduced between 46 and 62% with low‐emissions application methods. Land application of cattle and swine manure in wet climates had EFs of 0.005 and 0.011 kg N2O–N kg–1TN, respectively, whereas in dry climates the EF for cattle manure was 0.0031. The N2O EFs for cattle urine and dung in wet climates were 0.0095 and 0.002 kg N2O–N kg–1TN, respectively, which were three times greater than for dry climates. The N2O EFs for sheep urine and dung in wet climates were 0.0043 and 0.0005, respectively. The use of nitrification inhibitors reduced emissions in swine manure, cattle urine/dung, and sheep urine by 45–63%. These enhanced EFs can improve national inventories; however, more data from poorly represented regions (e.g., Asia, Africa, South America) are needed.