Greenhouse gas and ammonia emissions from an open-freestall dairy in Southern Idaho

Authors: Leytem, April; Dungan, Robert - Rob; Bjorneberg, David - Dave; Koehn, Anita

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2012
Publication Date: 1/20/2013
Citation: Leytem, A.B., Dungan, R.S., Bjorneberg, D.L., Koehn, A.C. 2013. Greenhouse gas and ammonia emissions from an open-freestall dairy in Southern Idaho. Journal of Environmental Quality. 42:10-20.

Interpretive Summary: Concentrated animal feeding operations (CAFOs) emit trace gases such as ammonia (NH3), methane (CH4) and nitrous oxide (N2O) to the atmosphere. While NH3 is a precursor to fine particulate matter that can affect livestock and human health and air quality, CH4 and N2O are potent greenhouse gases. The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates that reflect the range of animal production facilities and climatic conditions that exist in the U.S.. Therefore, the objective of this study was to determine the emission rates of NH3, CH4 and N2O over the course of one year from two source areas (open-freestall barns and wastewater ponds) on a large open-freestall dairy located in southern Idaho to determine both diurnal and seasonal trends in emissions. There were strong diurnal trends in the emission of NH3 and CH4 at all locations studied, while there were only diurnal trends in N2O emissions at the wastewater ponds. Emissions tended to be lower in the late evening and early morning and then increase throughout the day as temperature, wind speed, and animal activity increase. There was some seasonal variation in NH3 and CH4, particularly at the wastewater ponds. In fact there was a linear increase in emissions with increasing temperature at the wastewater ponds for both NH3 and CH4. However, N2O emissions from the wastewater ponds tended to be greatest in spring. Ammonia emissions from the open-freestall area tend to be greatest in summer and fall when temperatures are greater, and then decrease with decreasing temperatures in spring and winter. There did not seem to be much of a seasonal effect for the emissions of CH4, or N2O from the open-freestall area. Average emissions per cow per day from the open-freestall source area were 0.10 kg NH3 and 0.47 kg CH4. Average emissions from the wastewater ponds (emissions per square meter per day) were 7.8 g NH3 and 22 g CH4. The combined emissions on a per cow per day basis from the open-freestall and wastewater pond areas averaged 0.22 kg NH3 and 0.85 kg CH4. The wastewater ponds were the greatest source of total farm NH3 emissions from spring through fall, contributing 64% of total emissions. The emissions of CH4 were approximately equal from the two source areas from spring through fall. During the winter months, due to decreasing temperatures and freezing of the pond surfaces, the open-freestall source area constituted the greatest source area of both NH3 and CH4 emissions. Data from this study can be used to develop trace gas emissions factors from open-freestall dairies in southern Idaho and potentially other open-freestall production systems in similar climatic regions.

Technical Abstract: Concentrated dairy operations emit trace gases such as ammonia (NH3), methane (CH4), and nitrous oxide (N2O) to the atmosphere. The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates. The objective of this study was to determine the emission rates of NH3, CH4, and N2O from the open-freestall and wastewater pond source areas on a commercial dairy located in southern Idaho. Gas concentrations and wind statistics were measured each month and used with an inverse dispersion model to calculate emission rates. Average emissions per cow per day from the open-freestall source area were 0.10 kg NH3 and 0.47 kg CH4. Average emissions from the wastewater ponds (g m-2 d-1) were 7.8 g NH3 and 22 g CH4. The combined emissions on a per cow per day basis from the open-freestall and wastewater pond areas averaged 0.22 kg NH3 and 0.85 kg CH4. The wastewater ponds were the greatest source of total farm NH3 emissions from spring through fall, contributing 64% of total emissions. The emissions of CH4 were approximately equal from the two source areas from spring through fall. During the winter months, due to decreasing temperatures and freezing of the pond surfaces, the open-freestall source area constituted the greatest source area of both NH3 and CH4 emissions. Data from this study can be used to develop trace gas emissions factors from open-freestall dairies in southern Idaho and potentially other open-freestall production systems in similar climatic regions.