The Scientific Basis for Estimating Air Emissions from Animal Feeding Operations Interim Report (2002) / Chapter Skim
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1. Introduction
1. Introduction
Pages 7-22
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From page 7... ...
, other federal and state agencies, the animal feeding industry, and the general public an initial assessment of the methods and quality of data used in estimating air emissions from animal feeding operations (AFOs as defined by EPA; see Appendix B)
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. Are the emission estimation approaches described in the EPA report Air Emissions from Animal Feeding Operations (EPA, 2001a)
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Effects on air emissions of nutrient management practices currently recommended to protect water quality are generally unknown. In addition to potential conflicts between air quality and regulations aimed at improving water quality, state regulations based on inadequate air emissions information may lead to inappropriate actions.
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Finding 1: Proposed EPA regulations aimed at improving water quality may affect rates and distributions of air emissions from animal feeding operations. Regulations developed by the EPA's Office of Air and Radiation for AFOs will be influenced in part by existing National Ambient Air Quality Standards (NAAQS; EPA, 2002~.
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From page 11... ...
and to address the difficulty in characterizing AFOs as emissions sources by developing the concept of model farms. By judicious selection of criteria, emission factors obtained from the scientific literature for components of those model farms may allow for calculation of the desired estimate of annual mass emissions from a single AFO.
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From page 12... ...
Changes in NH3 emissions due to changes in ambient temperature could conceivably be accounted for through the generation of regression models relating temperature, pH, and dissolved ammonium ion concentration. Similar examples could be given for other types of manure management systems; it is reasonable to assume that individual processing steps within a given manure management system could be characterized by single emission factors that when combined, would lead to a viable estimate of emissions for each type of model farm.
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has not identified all of the factors necessary to characterize emissions from individual AFOs. Finding 4: Characterizing feeding operations in terms of their components (e.g., model farms)
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EMISSIONS FROM ANIMAL FEEDING OPERATIONS Ammonia The nitrogen in animal manure can be converted to ammonia by a combination of mineralization, hydrolysis, and volatilization (Oenema et al., 2001~. On a global scale, animal farming systems emit to the atmosphere ~20 Tg N/yr as NH3 (Galloway and Cowling, 2002)
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Anthropogenic activities account for most of the NO released into the atmosphere, with combustion of fossil fuels representing the largest source (van Aardenne et al., 2001~. Nitrification in aerobic soils appears to be the dominant pathway for agricultural NO release, with only minor emissions directly from livestock or manure.
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TABLE 1-1. Current Hydrogen Sulfide Standards in Various States State Standard (ppb)
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Once emitted, N2O is globally distributed because of its long residence time (~100 years) and contributes to both tropospheric warming and stratospheric ozone depletion.
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PM10 is commonly defined as airborne particles with aerodynamic diameters less than 10 ,um. This definition is not precise, however, and the 10 ,um diameter refers to the 50 percent cut diameter in a Federal Reference Method PM10 sampler (Federal Register, 1997)
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Key variables affecting the emissions of PM10 include the amount of mechanical and animal activity on the dirt or manure surface, the water content of the surface, and the fraction of the surface material in the size range. For PM2.5, key variables affecting the emissions include the net release of precursors such as NO and NH3.
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Though research is under way to relate olfactory response to individual odorous gases, odor measurement using human panels appears to be the method of choice now and for some time to come. Since odor can be caused by hundreds of compounds and is subjective in human response, estimates of national or global odor inventories are meaningless.
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TABLE 1-3. Typical Lifetimes in the Planetary Boundary Layer for Pollutants Emitted from Animal Feeding Operations Species Lifetime NH3 NOX H2S N2O CH4 PM VOCs Odora .
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Relatively straightforward methods for measuring emission rates by measuring airflow rates and the concentrations of emitted substances are often not available. Flow rates and pollutant concentrations may be available for some types of confined animal housing but usually not for emissions from soils.
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