Ammonia Released from Broiler houses Zifei Liu, Lingjuan Wang, David - PowerPoint PPT Presentation

A Review of Emission Models of Ammonia Released from Broiler houses Zifei Liu, Lingjuan Wang, David Beasley Department of Biological and Agricultural Engineering, North Carolina State University Biological & Agricultural Engineering 1

Ammonia as an air pollutant (Four major impacts) Health impact Soil acidification Eutrophication (Nitrification processes) (Excess N deposition) Aerosol formation (Fine particle precursor) 2

Ammonia emissions from animal production Air Emissions from Animal Feeding Operations: Current Knowledge, Future Needs, National Research Council (NRC) of The National Academies of Science, 2003 Human activities Consent agreements with USEPA, 2005 10% Cropping Activities 10% Animal Production 80% 3

Broiler house Ammonia emissions: the primary concern for Ammonia in broiler house: regulatory reporting affect bird performance under CERCLA NH 3 NH 3 Broiler litter 4

Estimation of Emission Rates form broiler houses Seasonal conditions Regional conditions Wide variations have been found House design Management practices Litter properties … Quantifying of ammonia emission rates from broiler houses: a complex process 5

Three major objectives of emission models 1. To calculate site-specific emissions, using the local design and operating parameters. 2. To quantify and evaluate the effectiveness of the various control strategies 3. To simulate seasonal and geographic variations in ammonia emission factors 6

Emission models Mechanistic models Empirical models Sub-models Process based models Mass balance models N-mass flow Inverse dispersion models models 7

Scientific basis of ammonia emissions from broiler litter 8

Mass transfer flux equation Emission flux = K m (C g, 0 – C g, ∞ ) K h Temperatur Air velocity C l, 0 e Temperature Surface roughness K d Air density Air viscosity pH Temperature Generation & Litter moisture diffusion of TAN in Litter N litter content Microbial & enzymatic activities 9

Factors that may affect ammonia emissions from broiler litter • Litter moisture content • Temperature • Litter nitrogen content • Humidity – Diet • Air exchange rate – litter age – Residence time – bird age – Air velocity • Litter type • pH • … 10

• Mechanistic models (Pinder et al., 2004) • Sub-models • Empirical models • Mass balance models • Inverse dispersion models • Process based models Emissions = A [TAN] H* r -1 • N-mass flow models A : the area of exposed manure [TAN] : concentration of TAN H* : effective Henry’s constant r : mass transfer resistance 11

• Mechanistic models (Zhang et al., 2006) • Sub-models • Empirical models • Mass balance models • Inverse dispersion models • Process based models Emission rates = Q (C house - C out ) • N-mass flow models Q : ventilation rate C house : concentration of NH 3 in house air C out : concentration of NH 3 in outside air 12

• Mechanistic models Ventilation sub-models • Sub-models • Empirical models (Hutchings et al., 2006; Zhang et • Mass balance models al., 2005; Koerkamp et al., 1998) • Inverse dispersion models • Process based models • Assume the aim of management is to • N-mass flow models maintain the indoor temperature at a target value suitable for the animal species. Outside temperature Thermal energy models Ventilation rate Sensible heat production of the animals 13

• Mechanistic models N-excretion sub-models • Sub-models • Empirical models (Zhang et al., 2006) • Mass balance models • Inverse dispersion models • • Process based models The ASAE Standard for animal manure • N-mass flow models production and characteristics were used as the basis for developing the manure and N excretion model. Type and growth stage of animals Feed factors N excretion Animal productivity of animals Animal management practices 14

• Mechanistic models • Sub-models (Carr et al.,1990 ) • Empirical models • Mass balance models • Inverse dispersion models • Process based models Air temperature • N-mass flow models RH Litter pH Litter moisture Ammonia content concentration Litter in house temperature Litter moisture content 15

• Mechanistic models • Sub-models • Empirical models (Gates et al., 2004; Wheeler et al., 2004) • Mass balance models • Inverse dispersion models • Process based models • N-mass flow models Emission rates Bird age 16

• Mechanistic models • Sub-models • Empirical models (NRC, 2003; Burns et al., 2003; • Mass balance models Keener and Zhao, 2006) • Inverse dispersion models • Process based models • N-mass flow models Flow diagram of nitrogen input and output of broiler house Finished bird Bird Used litter Input Output Litter Broiler house Leachate Feed Ammonia emission Water Other gases 17

• Mechanistic models • Sub-models • Empirical models (Siefert et al., 2004; Faulkner, et • Mass balance models al., 2006) • Inverse dispersion models • Process based models • N-mass flow models Dispersion plume models Downwind concentration Emission rates Inverse dispersion models 18

• Mechanistic models • Sub-models (Mukhtar et al. 2004; Zhang et al., • Empirical models 2005; Kohn et al., 1997). ) • Mass balance models Inverse Gaussian models • • Process based models take • Process based models emissions from AFO as a whole and consider each of the • N-mass flow models processes occurring on a typical farm, and calculates the resulting ammonia emissions from each. Housing NH 3 AFO Storage NH 3 NH 3 NH 3 Land application 19

• Mechanistic models • Sub-models • Empirical models (Mukhtar et al. 2004; Zhang et al., • Mass balance models 2005; Kohn et al., 1997). ) Inverse Gaussian models • • Process based models • • Certain sectors of the animal N-mass flow models enterprise are likely to be more important for some emissions than for others. Development of a process-based model would enable system analysis and simulation for determining critical control points for emissions 20

• Mechanistic models • Sub-models • (Reidy, et al. 2006) Empirical models • Mass balance models Inverse Gaussian models • • N-flow models have been widely • Process based models used in the national ammonia • N-mass flow models emission inventory calculations and manure policy analysis in Europe. NH 3 NH 3 NH 3 TAN TAN TAN Land application Storage Housing 21

• Mechanistic models • Sub-models • Empirical models • (Reidy, et al. 2006) Mass balance models Inverse Gaussian models • • Process based models • The N-mass flow model enables • N-mass flow models rapid and easy estimation of the consequences of upstream emission on downstream emissions. It has been adopted to calculate the interaction between abatement techniques at various stages of manure management. 22

Summary and future directions • Emission models increase the simplicity of emission estimation. Various emission models have been developed to fit different objectives for the estimation. • It would be important to improve temporal resolution as well as geographical resolution of ammonia emission models to meet the requirement of recent chemical transport modeling . 23

Summary and future directions • Models are being further developed, and extensive challenges exist. Characterization of management factors and litter conditions are not well documented and they have not been adequately incorporated into current mechanistic models. Much work remains to be done because of the number of variables in practice. Further evaluation of these variables is needed for enhanced understanding of the wide variation in ammonia emission rates. • Because of the high uncertainties of measuring emissions from farm, it would be valuable to expand research in well-controlled test facilities and evaluate model components individually or in designed combinations. 24

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