The Scientific Basis for Estimating Air Emissions from Animal Feeding Operations Interim Report (2002) / Chapter Skim
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3. Models for Estimating Emissions
3. Models for Estimating Emissions
Pages 54-65
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From page 54... ...
mitigation technologies and management practices in addition to those identified in the EPA draft report. EPA MODEL FARM CONSTRUCT Are the emission estimation approaches described in the EPA/OAR summary document, Air Emissions from Animal Feeding Operations, appropriate?
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From page 55... ...
providing accurate estimates of the relationship between the dependent and independent variables in the model farm construct; and · having estimates of the relationship between dependent and independent variables that clearly distinguish among the kinds of AFOs being modeled. A critical data requirement for estimating the appropriate emission factors is a statistically representative survey of emissions from the class of AFOs over several iterations of the time period to be represented.
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From page 56... ...
In particular, additional factors not included in the EPA model that affect emissions include animal feeding and management; animal productivity; housing, including ventilation rate and confinement area; use of abatement strategies such as sprinklers to decrease dust; and physical characteristics of the site such as soil type and whether the facility is roofed. In addition, emissions are likely to differ for different climatic (long-term)
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From page 57... ...
cannot be supported for estimating either the annual amounts or the temporal distributions of air emissions on an individual farm, subregional, or regional basis because the way in which it characterizes feeding operations is inadequate. INDUSTRY CHARACTERIZATION How should industry characteristics and emission mitigation techniques be characterized?
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From page 58... ...
Rather than discuss possible improvements in estimating air emissions using the EPA approach and the use of possible emissions mitigation techniques based on the EPA estimates at this time, these issues are being left to the final report. Mitigation of air emissions based on best management practices, including those under comprehensive nutrient management plans (CNMPs)
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From page 59... ...
There is little research, and even less agreement, as to what proportion of nitrogen is lost from various types of manure storage as NH3 or N2 (Harper et al., 2000~. Nonetheless, much of the variation in emissions from AFOs, such as that from feeding and animal management, can be accounted for by predicting the effect on manure nitrogen production (Kohn et al., 1997~.
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From page 60... ...
When considering long-term atmospheric emissions, an aggregated model on an annual time step may be adequate. If emission rates are needed to categorize farms that may potentially emit enough pollutants to warrant extra regulation, tabular values representing typical animal, crop, feed, and manure management might be adequate, and predictions for different situations could be calculated and reported in tables for rapid referral.
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From page 61... ...
It would also highlight fruitful research areas, and identify knowledge gaps that need to be filled in order to improve understanding of farm processes. Finding 8: A process-based model farm approach that incorporates "mass balance" constraints for some of the emitted substances of concern, in conjunction with estimated emission factors for other substances, may be a useful alternative to the model farm construct defined by EPA (2001a)
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From page 62... ...
(2000) showed that increasing milk production of dairy cows by administering growth hormone, increasing photoperiod using artificial lighting, and milking three times daily instead of two can decrease manure nitrogen by 16 percent for a given amount of milk produced.
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From page 63... ...
A preliminary list of manure handling and treatment technologies that have been identified and have relevance to air emissions includes: storage covers, anaerobic digestion, aeration, solid-liquid separation, comporting, and chemical treatment for pH control (Melvin, personal communication, 2002~. The potential air quality impacts of these manure treatment technologies will be analyzed in the committee's final report based on the published information, with recommendations for further research and development.
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From page 64... ...
ambient temperature anaerobic digester, energy recovery, greenhouse vegetable production; thermophilic (high-temperature) anaerobic digester energy recovery; solids separation-constructed wetlands; sequencing batch reactor; · upflow biofiltration; · solids separation, nitrif~cation-denitrif~cation, soluble phosphorus removal, solids processing; · belt manure removal and gasification to thermally convert dry manure to a combustible gas stream for liquid fuel recovery; · ultrasonic plasma resonator; .
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From page 65... ...
EPA has been actively seeking ARS research in several agricultural air quality topic areas. ARS research in agricultural air quality is organized into five categories: particulate emissions, ammonia and ammonium emissions, malodorous compounds, ozone impacts, and pesticides and other synthetic organic chemicals.
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