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Why Study Ammonia Emitted from Feedlots?
Ammonia volatilization is a major component of the nitrogen balance of a feedyard, and the effects of ammonia loss range from the economic (loss of manure fertilizer value) to the environmental (air quality degradation, overfertilization of ecosystems). Although not yet regulated, ammonia emissions from cattle are required to be reported under the Emergency Planning and Community Right to Know Act. Emission factors are used to estimate ammonia emissions for purposes of reporting and national inventories, but current emission factors are based on limited data. Our objective was to definitively quantify ammonia emissions and emission factors from commercial feedyards on the southern High Plains of Texas.
A typical feedyard on the High Plains of Texas. In the foreground, cattle in corrals with a stocking density of about 150 sq. ft./animal. In the background on the left, the runoff water retention pond, and center, a mound of stockpiled manure.
What Did We Do?
Ammonia emissions were quantified at three commercial feedyards in the Texas Panhandle from 2002 to 2008 using micrometeorological methods. Seasonal, intensive measurement campaigns were conducted from 2002 to 2005 at one feedyard, and ammonia emissions were near-continously monitored from 2007-2008 at two more feedyards. Meteorological and cattle management data were also collected.
What Have We Learned?
Ammonia emissions followed a distinct annual pattern. Emissions during summer were about twice those during winter, while spring and autumn emissions were intermediate. Annualized ammonia emissions ranged from 0.20 to 0.37 lb NH3/animal/day, and averaged 0.26 lb NH3/animal/day over all studies. Ammonia loss as a fraction of nitrogen fed to cattle averaged 41% during winter and 69% during summer; on an annual basis, 54% of fed nitrogen was lost as ammonia. Greatest emissions were observed when crude protein in cattle rations exceeded the nutrient requirements of beef cattle. Mean monthly ammonia emissions were strongly correlated with mean monthly temperature, and the relationship can be used to predict ammonia emissions from southern High Plains feedyards. Cattle feeders that meet recommended crude protein in rations can expect to lose half of fed N as ammonia. We recommend an annual emission factor of 88 lb/head for beef cattle feedyards based on one-time capacity, or 39 lb/head fed, based on a 150-d feeding period.
The annual pattern of ammonia emission rates (ER) followed seasonal temperatures, but also was sensitive to dietary crude protein (CP). Adding distillers grains to rations from March, 2008 to October, 2008 increased crude protein at Feedyard A to as high as 19%. Ammonia emissions greatly increased compared with the previous year and compared with Feedyard E.
Next steps involve using the extensive database from this research to adapt and refine process-based models of ammonia emissions. These models, based on the actual physical and chemical processes that control ammonia loss, will be more generally applicable than emission factors to a wider range of feedyards.
On an annual basis, ammonia emission averaged 0.26 lb per animal per day across the three feedyards and six years of study. Increased ammonia emission at Feedyard A in 2008 was due to high dietary crude protein when distillers grains were added to rations. Using these data and other estimates of ammonia loss from retention ponds and stockpiles, we recommend, for beef cattle fed a diet that meets protein requirements, an annual emission factor of 88 lb/head based on one-time capacity, or 39 lb/head fed, based on a 150-d feeding period.
Richard W. Todd, Research Soil Scientist, USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas, firstname.lastname@example.org
Richard W. Todd, Research Soil Scientist; N. Andy Cole, Research Leader and Research Animal Scientist (Nutrition); and Heidi M. Waldrip, Research Soil Scientist: USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas.
Cole, N.A., R.N. Clark, R.W. Todd, C.R. Richardson, A. Gueye, L.W. Greene, and K. McBride. 2005. Influence of dietary crude protein concentration and source on potential ammonia emissions from beef cattle manure. J. Anim. Sci. 83:722 731.
Cole, N.A., A.M. Mason, R.W. Todd, M. Rhoades, and D.B. Parker. 2009. Chemical composition of pen surface layers of beef cattle feedayrds. Prof. Anim. Sci. 25:541-552.
Flesch, T.K., J.D. Wilson, L.A. Harper, R.W. Todd, and N.A. Cole. 2007. Determining ammonia emissions from a cattle feedlot with an inverse dispersion technique. Agric. For. Meteorol. 144:139-155.
Hristov, A. N., M. Hanigan, A. Cole, R. Todd, T. A. McAllister, P. M. Ndegwa, A. Rotz. 2011. Ammonia emissions from dairy farms and beef feedlots: A review. Can. J. Anim. Sci. 91:1-35.
Preece, S.L., N.A. Cole, R.W. Todd, and B.W. Auvermann. 2012. Ammonia emissions from cattle-feeding operation. Texas A&M AgriLife Extension Bulletin E-632 12/12.
Rhoades, M.B., D.B. Parker, N.A. Cole, R.W. Todd, E.A. Caraway, B.W. Auvermann, D.R. Topliff, and G.L. Schuster. 2010. Continuous ammonia emission measurements from a commercial beef feedyard in Texas. Trans. ASABE 53:1823-1831.
Sakirkin, S.L., N.A. Cole, R.W. Todd, and B.W. Auvermann. 2011. Ammonia emissions from cattle-feeding operations. Part 1: issues and emissions. Texas Agricultural Experiment Station Bulletin, Air Quality Education in Animal Agriculture, Issues: Ammonia, December, 2011. p. 1-11.
Sakirkin, S., R.W. Todd, N.A. Cole, and B.W. Avermann. 2011. Ammonia emissions from cattle-feeding operations. Part 2: abatement. Texas Agricultural Experiment Station Bulletin, Air Quality Education in Animal Agriculture, Issues: Abatement, December, 2011. p. 1-11.
Todd, R.W., N.A. Cole, and R.N. Clark. 2006. Reducing crude protein in beef cattle diet reduces ammonia emissions from artificial feedyard surfaces. J. Environ. Qual. 35:404-411.
Todd, R.W., N.A. Cole, M.B. Rhoades, D.B. Parker, and K.D. Casey. 2011. Daily, monthly, seasonal and annual ammonia emissions from southern High Plains cattle feedyards. J. Environ. Qual. 40:1-6.
Todd, R.W., N.A. Cole, H.M. Waldrip, and R.M. Aiken. 2013. Arrhenius equation for modeling feedyard ammonia emissions using temperature and diet crude protein. J. Environ. Qual. 2013. (accepted for publication).
Research was supported by CSREES Grant #TS2006-06009 under the direction of Dr. John Sweeten, Resident Director, Texas A&M University AgriLife Research and Extension Center, Amarillo, TX. Larry Fulton, Research Technician, USDA-ARS-CPRL, provided invaluable technical and logistical support and expertise.
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