Application of Gas-Permeable Membranes for Mitigation of Ammonia Gas from Animal Manure
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Excessive ammonia (NH3) emissions from animal feeding operations are reported as a source of environmental pollution. Moreover, NH3 emissions result in the loss of nitrogen (N) as a plant nutrient, and so its mitigation and capture is beneficial to the environment. In laboratory study, acrylic chambers were filled with liquid dairy manure (LM) at a constant depth as a source of total ammoniacal nitrogen (TAN). Four chamber sizes (one size per experiment) labeled 1X, 2X, 4X and 8X were used to vary the surface area of LM while the depth of LM was kept constant in all chambers. Identical tubular gas-permeable membrane (GPM) systems were used in each chamber and allowed NH3 diffusion from LM into the GPM system and produced an ammonium sulfate ((NH4)2SO4) by-product (ASB). A concentrated H2SO4 (pH=0.36) was circulated through the GPM systems of the chambers. The 4X chamber resulted in the best NH3 mitigation and recovered the most concentrated ASB, but its final pH was 0.67 and not applicable as a plant nutrient. The H2SO4 solution was diluted to pH 2, 3, 4, and 5 and circulated in the 4X chamber. Results showed that NH3 was recovered by diluted acids but the pH 2 experiment produced more concentrated ASB. The NH3 flux and its mass transfer coefficient were calculated and the values showed that NH3 diffusion occurred during the entire period of the experiments due to NH3 gas partial pressure gradient and the solution circulation flow rate. For increasing the ASB concentration, the circulation flow rate of the diluted acidic solution was increased and its pH was controlled between 2 and 6. The overall flow rate was increased from 5.6 to 36 and from 40 to 280 mL min-1 in the lab-scale and field-scale experiments, respectively, that enhanced the overall ASB concentration up to 50%. Finally, the recovered ASB from diluted acid experiments was used in greenhouse wheat seed cultivation tests and compared to inorganic (NH4)2SO4. The ASB treatments increased wheat germination, biomass, dry mass, biomass per plant and dry mass per plant, especially when the soil pH was adjusted between 5.6 and 6.
Samani Majd, Amir M (2015). Application of Gas-Permeable Membranes for Mitigation of Ammonia Gas from Animal Manure. Doctoral dissertation, Texas A & M University. Available electronically from