An Acid Spray Scrubber for Recovery of Ammonia Emissions from a Deep-Pit Swine Facility

Abstract. Ammonia (NH₃) emissions from animal facilities represent a significant health and environmental concern. Acid spray scrubbers are promising for the recovery of NH₃ emissions from animal facilities due to their low pressure drop and additional benefit of fertilizer production through NH₃ absorption by the dilute acid scrubbing solution. A spray scrubber for deep-pit swine finishing facilities was developed based on an optimized spray scrubber module with a round geometry and a diameter of 35.56 cm. A hollow-cone AAP01 nozzle with a larger orifice diameter of 200 μm was used to spray 1% (w/v) sulfuric acid solution into the scrubber. The use of this nozzle required three stages of spray, which reduced NH₃ by 82% to 99% for inlet NH₃ concentrations of 30 and 20 ppm_v, respectively. The scrubber was evaluated in four seasons at a commercial swine-finishing barn with deep-pit manure storage in Raymond, Ohio. An average NH₃ removal efficiency of 88% was observed. The seasonal evaluations showed the lowest NH₃ concentration (5.4 ppm_v) occurred during spring when mixed natural ventilation and pit fan ventilation were used, while the highest NH₃ concentration (25.4 ppm_v) was observed during winter when minimal ventilation was used. It was observed that inlet NH₃ concentrations negatively affected the scrubber efficiency. Water and acid consumption rates were considerably low for all seasons, with an average of 2.5 and 0.17 L d^-1, respectively. Energy consumption, mainly by the pump, averaged 0.56 kWh per day. A preliminary economic analysis estimated a five-year break-even period for operation of spray scrubbers at six pit exhaust fans, assuming minimal maintenance, low depreciation, and no significant additional energy cost for the ventilation fans.