Ammonia emissions from dairy lagoons in the western U.S.

Ammonia (NH3) emissions from dairy liquid storage systems can be a source of reactive nitrogen (N) released to the environment with a potential to adversely affect sensitive ecosystems and human health. However, there has been little on-farm research conducted to estimate these emissions and determine the factors that may affect these emissions. Six lagoons in south-central Idaho were monitored for one year, with NH3 emissions estimated by inverse dispersion modeling. Lagoon characteristics thought to contribute to NH3 emissions were also monitored over this time period. Average daily emissions from the lagoons ranged from 5.7 to 45 kg NH3 /ha or 5.7 to 96 kg NH3. There was a general trend for greater emissions during the summer, when temperatures were greater, in addition high wind events and agitation of the lagoons created temporary increases in NH3 emissions irrespective of temperature. Lagoon physicochemical characteristics such as total Kjeldahl nitrogen (TKN) and total ammoniacal nitrogen (TAN) were highly correlated with emission. Ammonia emission prediction models were developed using TKN, TAN, wind speed, air temperature and pH as independent variables. An on farm N balance suggests that lagoon NH3-N losses represented 9% of total N lost from the facility, 65% of the total lagoon N and 5% of dairy herd N intake. A process based model estimated similar values for N excretion and NH3-N loss from the lagoon. On-farm work is necessary to better refine both process based models and emission factor estimates in order to more accurately account for NH3 emissions from lagoons on dairies in the western US