Title: Ammonia emissions and emission factors: a summary of investigations at beef cattle feedyards on the southern high plains Authors
Submitted to: Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 10, 2013
Publication Date: April 1, 2013
Citation: Todd, R.W., Cole, N.A., Waldrip, H. 2013. Ammonia emissions and emission factors: a summary of investigations at beef cattle feedyards on the southern high plains. 2013 Livestock and Poultry Environmental Learning Center Conference Waste to Worth. 1:86. Interpretive Summary: Ammonia lost to the atmosphere from cattle feedyards is an important part of the nutrient balance of feedyards. Ammonia is important because its loss reduces the fertilizer value of manure, and it can decrease air quality or the health of ecosystems. We summarize six years of research at three commercial feedyards on the Texas High Plains where we measured ammonia loss. Average ammonia loss ranged from 0.20 to 0.37 pounds for every head of cattle each day. The average ammonia loss was 0.26 lb. per head per day. Temperature influences ammonia loss. Twice as much ammonia is lost in the summer as in the winter. The amount of crude protein in cattle diets also influences ammonia loss. If you feed too much crude protein, ammonia loss can increase as much as 50%. Even when cattle feeders do a good job of feeding the right amount of crude protein, ammonia loss is still about half of the protein nitrogen fed to cattle. For purposes of regulatory reporting or for ammonia inventories, we recommend that stakeholders use an annual emission factor of 88 lb. per head per year, based on the average number of animals in a feedyard.
Technical Abstract: 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). Seven years of research at the USDA-ARS Conservation and Production Research Laboratory have greatly increased our understanding of ammonia emissions from southern High Plains beef cattle feedyards. We summarize results of our ammonia investigations and report emission rates, discuss major factors that influence emissions, and recommend a whole-farm emission factor. Ammonia emissions were quantified at three commercial feedyards in the Texas Panhandle from 2002 to 2008 using micrometeorological methods. 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/head/day, and averaged 0.26 lb NH3/head/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 NRC (2000) nutrient requirements of beef cattle. Mean monthly ammonia emissions were strongly correlated with mean monthly temperature, and the relationship could be used to predict ammonia emissions from southern High Plains feedyards. Cattle feeders that meet recommended crude protein in rations can expect to lose 50% 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.