Development Of The ARS Air Scrubber: A Device For Reducing Ammonia, Dust and Odor Emissions From Animal Rearing Facilities.

Over half of the nitrogen (N) excreted by chickens is lost into the atmosphere as ammonia before the manure is removed from the barns.  This not only represents a huge waste of N (>300 million kg N/year in the US); it causes air and water pollution.  Large quantities of dust and volatile organic compounds (VOCs) are also emitted from both poultry and swine barns, contributing to air pollution and odor.  We developed and patented a scrubber for capturing ammonia and dust exhausted from animal feeding operations (AFOs). The objectives of this project were; (1) to re-design the scrubber to improve the ammonia removal efficacy, (2) conduct full-scale testing of the scrubber under controlled conditions at various ventilation rates, and (3) evaluate the cost, practicality and efficacy of various acids and water for scrubbing ammonia.  The efficiency of ammonia removal by the scrubber varied from 55-95%, depending on the air flow rate, type of acid used, and the internal scrubber configuration.  The relative efficiency of the scrubber for capturing NH₃ decreased as the ventilation rate increased from over 90% at flow rates of 3,000 cfm to around 55% at 9,500 cfm.  However, the mass of N captured by the scrubber tripled as flow rates increased from 3,000 to 9,500 cfm.  Similarly, there was a slight reduction in NH₃ removal efficiency as inflow NH₃ levels were increased from 10 ppm to 75 ppm, whereas the mass captured increased from 25 g N/hr to around 200 g N/hr.   This technology could potentially result in the capture of a large fraction of the N lost from AFOs, while simultaneously reducing emissions of bacteria, dust, and odors, which would improve the social, economic, and environmental sustainability of poultry and swine production.