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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Livestock Nutrient Management Research » Research » Publications at this Location » Publication #214842
Title: Flux-gradient estimates of ammonia emissions from beef cattle feedyard pens

Author
item Todd, Richard
item Cole, Noel
item HARPER, LOWRY - UNIVERSITY OF GEORGIA
item FLESCH, THOMAS - UNIVERSITY OF ALBERTA

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2007
Publication Date: 9/16/2007
Citation: Todd, R.W., Cole, N.A., Harper, L.A., Flesch, T.K. 2007. Flux-gradient estimates of ammonia emissions from beef cattle feedyard pens. In: Proceedings of the ASABE International Symposium on Air Quality and Waste Management for Agriculture, September 16-19, 2007, Broomfield, Colorado. 2007 CD-ROM.

Interpretive Summary: Concentrated animal feeding operations are major sources of ammonia emitted into the atmosphere, but few studies have investigated emissions from large, open lot beef cattle feedyards. We used the flux-gradient method to estimate ammonia emissions during six field campaigns in three seasons. Profiles of ammonia concentration, wind speed, and air temperature were measured on towers located within feedyard pens. Mean daily ammonia loss in summer was about twice that in winter. Springtime losses were highly variable and were attributed to greater ammonium concentration in manure and high wind speeds. Nitrogen emitted as ammonia averaged 3930 and 2150 kg/d in summer and winter, respectively, which was 45% and 27% of the nitrogen fed to cattle. Mean annual emission of nitrogen as ammonia was 36% of fed N, and an annual emission factor for feedyard pens based on total yearly per head production was 11.0 kg NH3-N/head/yr. Ammonia emissions increased after crude protein in cattle rations was increased from 13.5% to 14.5%. Ammonia emissions estimated using the flux-gradient method were 22% to 36% less than those derived from an inverse dispersion model. Uncertainty in parameters used to calculate ammonia loss and violation of assumptions of the method could have contributed to the lower flux estimates of the flux-gradient method. Optimizing fed N through practices such as phase feeding could help minimize ammonia emissions. Longer term, continuous monitoring of ammonia emissions is needed to better define annual variability, emission rates and factors, and facilitate development of process models.

Technical Abstract: Concentrated animal feeding operations are major sources of ammonia emitted to the atmosphere. There is a considerable amount of literature on ammonia emissions from poultry and swine, but few studies have investigated large, open lot beef cattle feedyards. We used the flux-gradient method to estimate ammonia emissions during six field campaigns in three seasons. Profiles of ammonia concentration (acid gas washing or chemiluminescence), wind speed and air temperature were measured on towers located within feedyard pens. Mean daily ammonia flux in summer averaged 72 ug/m^2/s, and in winter, 39 ug/m^2/s. Springtime fluxes were highly variable and averaged 79 ug/m^2/s; high springtime fluxes were attributed to greater ammonium concentration in manure and high wind speeds. Ammonia-N emisson rate averaged 3930 and 2150 kg/d in summer and winter, respectively, which was 45% and 27% of fed N. Assuming that the mean of summer and winter emission rates represented a mean annual emission, ammonia-N loss was 36% of fed N, and an annual emission factor for feedyard pens based on total yearly per head production was 11.0 kg NH3-N/head/yr. Ammonia emissions increased after N in cattle rations was increased from 13.5% to 14.5%. Ammonia emissions estimated using the flux-gradient method were 22 to 36% less than those derived from an inverse dispersion model. Uncertainty in the Schmidt number and possible violation of the assumption of homogeneous flow could have contributed to the lower flux estimates of the flux-gradient method. Optimizing fed N through practices such as phase feeding could help minimize ammonia emissions. Longer term, continuous monitoring of ammonia emissions is needed to better define annual variability, emission rates and factors, and facilitate development of process models.