Air Emissions from Animal Feeding Operations Current Knowledge, Future Needs (2003) / Chapter Skim
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3. Air Emissions
3. Air Emissions
Pages 50-73
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The focus of this report is on air emissions from animal feeding operations (AFOs)
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51 ca ca v v^ E~ v o a~ c)
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Gaseous NH3 is removed primarily by dry deposition, while aerosol NH4+ is removed primarily by wet deposition. As an aerosol, NH4+ contributes directly to PM2.5 (particulate matter having an aerodynamic equivalent diameter of 2.5,um or less)
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in the atmosphere is often referred to as NOy. The residence time of NOy is of the order of days in the lower atmosphere, with the principal removal mechanism involving wet and dry deposition of HNO3 and aerosol NO3-.
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Volatile Organic Compounds Volatile organic compounds (VOCs) vaporize easily at room temperature and include fatty acids, nitrogen heterocycles, sulfides, amines, alcohols, aliphatic aldehydes, ethers, p-cresol, mercaptans, hydrocarbons, and halocarbons.
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From page 55... ...
AFOs can contribute directly to primary PM through several mechanisms, including animal activity, animal housing fans, and air entrainment of mineral and organic material from soil, manure, and water droplets generated by highpressure liquid sprays, and they can contribute indirectly to secondary PM by emissions of NH3, NO, and H2S, which are converted to aerosols through reactions in the atmosphere. Particles produced by gas-to-particle conversion generally are small and fall into the PM2.5 size range.
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Others define OU as a unitless odor concentration, which is numerically equivalent to the numerical factor by which an air sample must be diluted until the odor reaches the ODT. Other Substances During the course of this study, the committee was informed through its scientific sessions and public forums of other potential substances (e.g., bioaerosols, pesticides, and carbon disulfide emitted through the air from AFOs)
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Hourly, Daily, and Seasonal Changes Changes in emissions from individual AFOs due to hourly, daily, and seasonal variations are discussed here because measurements to characterize emissions have usually been conducted for short periods of time. Failure to account for short-term cycles in an experimental design could result in significant systematic errors in a derived annual emission factor.
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CEmission fluxes are in kilograms of nitrogen as NH3 per hectare per day. Half of the lagoon was covered and half was uncovered; the lower numbers were measured from the covered half.
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, averaging does not compensate for the systematic bias that may be present as a result of the failure of an experimental design to account adequately for such events. Animal Life Stage Reference has already been made to changes in feed formulations that occur during the life cycles of most animals produced at AFOs and their subsequent effects on the amount and composition of fecal matter and urine excreted (NRC, 1994, 1998a, 2000, 2001a)
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The actual feed formulation is changed four times during the growth cycle of the hog to account for changes in nitrogen required for maintenance and growth. Sharp decreases in the relative amount of nitrogen excreted per day when the formulation changes are not simply an artifact of the model, but reflect periods of adjustment by the animal to the changes in feed composition.
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Feeding a total mixed ration increased milk production by 6.6 percent with no significant change in NUE. Use of bovine somatotropin resulted in a significant increase in both milk production and NUE, thereby decreasing the amount of nitrogen excreted per unit of production.
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a Total mixed ration 6.6b -1.4 DHIA members 10.7b 4.4 BSTe l4.lb 6.9b 3x milkingf 9 gb 5.3 Extended photoperiod 11.3b 4.3 Seasonal calving -15.1b -1.4 Cover crops 0.4 2.1 Nitrogen nutrient management plan -0.7 0.0 MUN testing" 6.9b 2.5 Complete feedh -6.3b -5.6b aPercent change from using versus not using the management practice.
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, ionophores do serve to increase the efficiency of feed utilization. DISPERSION OF AIR EMISSIONSMETEOROLOGICAL CONSIDERATIONS Temporal Dynamics An atmospheric substance can be characterized by its lifetime (also called its residence time)
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calculations, where given emission rates are used to estimate downwind concentration fields, and inverse calculations, where measured concentration fields are used to estimate emission rates. In either of these approaches, the tools must account for the characteristics of the surface and their effects on the flow field, and the effects of regional meteorology.
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The complexities of the various kinds of air emissions and the temporal and spatial scales of their distribution make direct emission measurements at the individual AFO level generally impractical and cost prohibitive other than in a research setting. Relatively straightforward methods for measuring emission rates by measuring airflow rates and the concentrations of emitted substances are often not available.
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This may not be the case within the boundary of the AFO and especially in enclosed animal housing. Most of the concern with possible health effects of air emissions from AFOs focuses on ammonia, hydrogen sulfide, and particulate matter.
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Hydrogen Sulfide Hydrogen sulfide is a colorless gas with a strong and generally objectionable rotten egg odor, detectable at concentrations down to 0.5 parts per billion (ppb)
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The NOAEL for exposures up to 90 days seemed to be 80 ppm for most systemic end points in rats and mice, and 8.5 ppm in pigs. Particulate Matter Particles are highly complex in terms of size, physical properties, and composition, and there may be important synergistic effects with gases in the air.
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Following deposition to terrestrial ecosystems, that same nitrogen atom can increase soil acidity, decrease biodiversity, and increase or decrease ecosystem productiv
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70 Q cn xl x ~ , .
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FINDING 2. Air emissions from animal feeding operations are of varying concern at different spatial scales, as shown in Table 3-7.
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, the aim is to control ambient concentrations at the farm boundary and/or nearest occupied dwelling. Standards applicable to the farm boundary and/or nearest occupied dwelling must be developed.
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The effects of temporal and spatial factors are described along with the complexities of modeling the flow of emissions over complex terrain as they affect field measurements. Potential impacts of these air emissions on human health and the environment are described and put in the context of expected rates and concentrations of emissions from animal feeding operations.
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