Title: Ammonia emissions from cattle-feeding operations. Part 2: abatement. Authors
Submitted to: Experiment Station Bulletins
Publication Type: Experiment Station
Publication Acceptance Date: August 15, 2011
Publication Date: December 15, 2011
Citation: Sakirkin, S., Todd, R.W., Cole, N.A., Avermann, B.W. 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. Interpretive Summary: Appreciably quantities of ammonia can be produced by animal feeding operations (AFO). Decreasing these losses can improve air quality and save valuable nitrogen (N) that can be used to fertilize crops. Ammonia abatement measures can be implemented at two different stages of livestock production. First stage measures are applied before the animal excretes the N. These include dietary strategies to reduce the amount of N excreted in livestock manure. In the second, or post-excretion, stage management strategies are implemented to reduce the amount of ammonia transferred to the environment from the manure. This paper summarizes first stage and second stage methods that may potentially be used by beef cattle feedlots to reduce ammonia emissions. Presently, most of these methodologies are not economically viable. The most feasible methods currently available involve manipulating diets so that N excretion is decreased but animal performance is improved or not adversely affected. Use of growth promoting regimens may not directly affect ammonia emissions but can decrease ammonia losses per unit of production. Covering stored manure and incorporating manure when it is land-applied can significantly reduce ammonia losses.
Technical Abstract: Ammonia abatement measures can be implemented at two different stages of livestock production. First stage measures are applied in the pre-excretion phase. These include nutrition-based strategies to reduce the amount of nitrogen (N) excreted in livestock manure. In the second, or post-excretion stage, management strategies are implemented to reduce the amount of ammonia transferred to the environment from the manure. One means of reducing ammonia emissions from concentrated animal feeding operations (CAFOs) is to reduce the amount of N excreted by the animals, especially the quantity excreted as urea in urine. In some cases, it is possible to manipulate diets to reduce total N, and urinary N excretion while continuing to meet the nutritional requirements and performance expectations of the animals. Observations amongst researchers over the past decade indicate that annual ammonia losses from beef cattle feedyards average approximately 50% of the N consumed by cattle: summer emission rates are about twice those in winter. Modifications of diet composition can effectively reduce ammonia emissions by 20 to 50% with only small effects on animal performance. Some of the dietary constituents that can be manipulated include concentrations of crude protein, degradable intake protein, fat, and fiber, and use of growth promoting feed additives and implants. However, the large size of many CAFOs presents economic and logistic challenges to modifying diets or feeding practices. Modifications to equipment, diets, or management practices may impose increased cost, labor, and time. Phase feeding involves adjusting nutrient intake over time to match the changing needs of the animal. If protein is progressively diminished through the feeding period, in balance with the animals' nutritional requirements, potentially less N is excreted and less ammonia may be emitted. Manipulation of dietary fiber may also affect ammonia emissions from feedyards by altering microbial processes on the pen surface. Post-excretion ammonia abatement strategies such as improved manure management can reduce the rate of N volatilization and ammonia emissions. Based on laboratory studies, a number of compounds can potentially be applied to feedlot pen surfaces to reduce ammonia emissions from feedyard surfaces; among them are zeolites (a microporous, aluminosilicate mineral), fats, and urease inhibitors.Unfortunately none of these are economically viable at the present time. Frequent pen cleaning may help to capture N in the manure by decreasing losses to the atmosphere. Covering stored manure to reduce its exposure to elements such as sun, wind, and rain is effective at reducing ammonia emissions. Immediate incorporation or injection into the soil has been shown to significantly reduce ammonia losses when manure is applied to farmland.