|Todd, Richard - Rick|
Submitted to: EPA Sponsored Workshop
Publication Type: Proceedings
Publication Acceptance Date: 5/13/2007
Publication Date: 7/31/2007
Citation: Todd, R.W., Cole, N.A., Clark, R.N. 2007. Ammonia emissions from open lot beef cattle feedyards on the Southern High Plains. In: Proceedings of the 16th Annual International Emission Inventory Conference, May 14-17, 2007. Raleigh, North Carolina. Available: http://www.epa.gov/ttn/chief/conference/ei16/session5/todd.pdf
Interpretive Summary: Ammonia is a nitrogen compound released to the atmosphere from concentrated animal feeding operations. Excess ammonia-nitrogen can overfertilize and degrade sensitive ecosystems. Ammonia is a precursor to minute atmospheric particles that can affect health and degrade air quality. Accurate estimation of ammonia emissions from cattle feedlots requires measurements of ammonia concentration and some kind of atmospheric dispersion model that incorporates the physical mechanism of how ammonia is removed and swept away from a feedyard into the atmosphere. Ammonia emission (loss to the atmosphere) for a commercial beef cattle feedyard on the Southern High Plains was quantified using an inverse dispersion model and measured profiles of ammonia concentration, wind speed, and air temperature collected on 39 days during five months over three years. Annually, for every head of beef produced in the feedyard, 19.3 kg of ammonia was lost to the atmosphere. For every metric ton of beef cattle produced in a year, 70.2 kg of ammonia was lost. Annual ammonia loss tends to be about 50% of the nitrogen fed to cattle. Summer emissions are about twice as great as in the winter. Ammonia emission is sensitive to crude protein content of cattle diets and increases as protein increases beyond cattle requirements. This research greatly expanded the database of ammonia emissions from beef cattle feedyards. However, longer term monitoring of ammonia emissons from feedyards is needed over a greater range of management practices, such as diets, manure harvesting, and sprinkler dust control. Inverse dispersion models show great utility and could be useful in a wide variety of monitoring and simulation applications.
Technical Abstract: Human activity has more than doubled the amount of reactive nitrogen that cycles through terrestrial ecosystems, with many negative impacts on ecosystem function and health and air quality. Concentrated animal feeding operations (CAFO) are major sources of ammonia emitted to the atmosphere. There is a considerable literature on ammonia emissions from poultry and swine CAFO, but few comprehensive studies have investigated large, open lot beef cattle feedyards. Ammonia emission rates and emission factors for a commercial beef cattle feedyard on the Southern High Plains were quantified using measured profiles of ammonia concentration, wind speed and air temperature, and an inverse dispersion model. Data were collected on 39 days during five months over three years. Mean summer emission rate was 7420 kg NH3 d-1, and winter emission rate was about half that, at 3330 kg NH3 d-1. Annual NH3-N emission rate was 4430 kg NH3-N d-1, which was 53% of the nitrogen (N) fed to cattle. Daily per capita NH3-N losses increased by 10-64% after the daily per capita N in feed rations increased by 15-26%. Annual emission factors for the pen area of the feedyard were 19.3 kg NH3 (head fed)-1, or 70.2 kg NH3 Mg-1 biomass produced. Annual emission factors for the retention pond of the feedyard were estimated to be 0.9 kg NH3 (head fed)-1, or 3.2 kg NH3 Mg-1 biomass produced.