Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2015
Publication Date: 7/1/2015
Citation: Bonifacio, H.F., Rotz, C.A., Leytem, A.B., Waldrip, H., Todd, R.W. 2015. Process-based modeling of ammonia and nitrous oxide emissions from open lot beef and dairy facilities. Transactions of the ASABE. 58:827-846.
Interpretive Summary: Gaseous emissions from animal feeding operations have become an air quality concern due to their potential adverse effects on both human health and the environment. USDA's Integrated Farming Systems Model was expanded to predict ammonia and nitrous oxide emissions from open lot beef feedyards and dairies. The revised model appropriately predicted the trend of measured ammonia emissions under varying weather conditions for two Texas beef cattle feedyards and three Idaho open lot dairies. This revised farm model provides a useful tool for assessing potential environmental impacts of beef and dairy open lot facilities along with other performance and economic aspects of the farm and feeding facility.
Technical Abstract: Air emissions, such as ammonia (NH3) and nitrous oxide (N2O), vary considerably among beef and dairy open lot operations as influenced by the climate and manure pack conditions. Because of the challenges with direct measurement, process-based modeling is a recommended approach for estimating air emissions from animal feeding operations, such as open lots. The Integrated Farm System Model (IFSM), a whole-farm simulation model for crop, dairy and beef operations, was previously used (version 4.0) to simulate NH3 emissions from open lots and performed well in representing emissions for two beef cattle feedyards in Texas. The previous model was found to perform poorly though in predicting NH3 emissions measured at two open lot dairies in Idaho, so further work was done to better represent the effects of climate on lot and manure pack conditions and to better integrate models for nitrification and denitrification processes. The revised model (version 4.1) appropriately predicted NH3 emissions for the two Texas beef cattle feedyards, with model predictions having 59% to 81% agreement with measured daily emissions of each lot. Simulated NH3 emissions for the Idaho open lot dairies improved considerably with 56% to 74% agreement between predicted and measured daily NH3 emissions. For an Idaho dairy with a freestall barn and open lot, the revised model simulated NH3 emissions with 92% agreement between predicted and measured values. Based on measurements obtained at two of the Idaho dairies, IFSM also predicted daily N2O emissions with good agreement (64% to 80%) to those measured. Hence, IFSM can be used to estimate open lot emissions of NH3 and N2O along with other aspects of performance, environmental impact and economics of cattle feeding operations in different climatic regions. The model provides a tool for evaluating management strategies to mitigate emissions and improve the sustainability of beef and dairy production systems.