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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131593399,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   K. Koirala, P M Ndegwa, H S Joo, C Frear, C O Stockle, J H Harrison
Keywords:   Ammonia dissociation mass transfer ammonia adsorption particle size distribution

Abstract. The goal of this study was to determine the effects of suspended solids (SS) adsorption properties and concentration on the mechanisms governing ammonia volatilization from liquid dairy manure. Pertinent properties that influence ammonia adsorption on SS, including particle size distribution (PSD) and volatile solids (VS) of manure from three dairy operations with different feed rations were evaluated. The main parameters governing ammonia volatilization from liquid manure, namely the dissociation constant (Kd), the fraction of un-ionized ammonia (β), and overall mass transfer coefficient (KoL) of ammonia for the three manures were determined experimentally in a laboratory convective emission chamber. The Kd and β values for the three manures were not significantly different (p-values >0.05); suggesting that SS ammonia adsorption did not significantly affect the Kd of ammonium in liquid dairy manure. Both β and Kd, however, decreased linearly (R2 = 0.89 and 0.88, respectively) with increasing SS concentrations in the manure, which implies that SS impedes ammonia volatilization, and conversely that SS removal via solids-liquid separation would exacerbate ammonia loss from liquid dairy manure. Data also indicated no significant effect (p > 0.05) of the SS adsorption properties on the KoL for liquid dairy manure. The KoL, however, also decreased linearly (R2 = 0.96) with increasing SS concentration in the manure. Overall these findings reveal that increasing SS concentration hinders ammonia volatilization process from liquid dairy manure, while the observed differences in the SS ammonia adsorption properties did not significantly affect this process.

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