Research on mitigating the effects of animal feeding operations (AFOs) on air quality in the US has made great strides in recent years. Development of cost-effective air emission mitigation and assessing the effectiveness of these technologies is urgently needed to improve our environmental performance and to help producers address increasing regulatory pressures. Scrubbers have been shown to be a powerful tool in reducing ammonia (NH3), dust and odor emissions. An affordable two-stage acid scrubber was developed by USDA ARS for treating exhaust air and can easily be installed onto the exhaust fans of existing poultry facilities. A field project was conducted to evaluate the efficiency of the acid scrubber under field conditions on three broiler farms, two located in Delaware (DE) and one located in Pennsylvania (PA).
The two-stage scrubbers were installed on the minimum fans of three farms that were using different practices and settings. One farm used 36” minimum fans and reused existing litter throughout the project while an organic farm used a 36” minimum fan, but used new bedding materials for every flock. The third scrubber was installed on a research farm with a 24” minimum fan and used litter. Sodium bisulfate was used as the acid agent. Ammonia concentration and airflow rate through each fan were continuously measured. Scrubber liquid samples were analyzed to calculate the efficiency of each scrubber. Acid, water and electricity consumption of each scrubber were recorded over multiple flocks and seasons.
The mean NH3 capturing efficiencies of the three scrubbers for the three sites were 31.3, 34.3 and 11.0 %, respectively. The low efficiency (11%) of one scrubber was due to high NH3 emission rate and inadequate acid solution in the scrubber (the solution at this site was checked and replaced weekly whereas the solution at the other two sites were checked daily). For every kg NH3 captured, the average water, sodium bisulfate and electricity consumption at the three sites were 0.23 m3, 15.10 kg and 43.74 kWh, respectively.
Based on the field experiences of running the three scrubbers, several recommendations are suggested: 1) increase fan run time to compensate for air flow loss due to high pressure drop, 2) add insulation on drain valves, 3) heat fresh water line and add a heater in pump boxes, 4) clean dust scrubber at least twice per flock for houses with used litter, 5) replace acid solution more frequently toward end of the flock for best performance, 6) add a storage tank for spent liquid if the growers do not have crops or pasture to apply to, and 7) add an automatic acid dosing system to reduce labor requirement and improve scrubber performance.
Hong Li, Assistant Professor, University of Delaware
Chen Zhang, Philip Moore, Michael Buser, Cathleen J. Hapeman, Paul Patterson, Gregory Martin, Jerry Martin
Zhang, Chen, Hong Li , Philip A Moore , Michael Buser, Cathleen J. Hapeman, Paul Patterson, Gregory Martin. 2016. ASABE Annual International Conference. Paper number 2461008; Orkando,Florida, July 17 - July 20.
This study was partially supported by funds from USDA-NRCS Conservation Innovation Grant Program (Award No. NRCS 69-3A75-12-244), University of Delaware, Penn State University, Oklahoma State University, University of Maryland, and USDA-ARS. The cooperation and assistance of the collaborating producer is also acknowledged.
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