On-Farm Testing of a Zeolite Filter to Capture Ammonia and Odors from a Dairy Manure Flushing System

Abstract

Highlights A zeolite filter achieved 92% reduction in ammonia emissions from a dairy flushed manure pit. The reduction in odor concentration was 45% at a minimum filter residence time of 0.9 seconds. The on-farm filter and air collection structure over a manure pit demonstrated the applicability of the project. Abstract. The concentration of large numbers of animals in relatively small areas, high production output per animal unit, and concentration of animal excretions and air emissions are some of the characteristics of modern animal agriculture. Ammonia (NH3) and odors are among the most noticeable as well as locally and regionally problematic emissions generated by concentrated animal feeding operation (CAFO) dairy production systems. Zeolites are defined as aluminosilicates with open three-dimensional framework structures composed of corner-sharing TO4 tetrahedra, where T is Al or Si. Zeolites are able to lose or gain water reversibly and to exchange and retain cations, including NH3 and ammonium. This study demonstrated the design and performance of a zeolite filter treating the airstream from a flushed manure pit installed on-farm at a commercial dairy. Clinoptilolite zeolite mined in Idaho was used as the filter medium. The capacity of the filter to reduce NH3 emissions was tested at three, six, and 59 days of filter operation. Reduction of odor emissions was tested at six days of operation. NH3 emissions were reduced by 92% (p < 0.001) at three days of operation and by 42% (p = 0.13) at 59 days of operation. The ammonia concentration in the pre-treatment airstream from a dairy manure collection pit was relatively high at 5.287 ±0.04 mg NH3-N m-3 (p < 0.001). The odor concentration reduction was 45% (p = 0.001) at six days of operation with the minimum empty bed residence time of 0.9 s. Total trial running time was 59 days. The roof-like pit cover structure used for air collection and the zeolite filter were proven to be capable of operating in the harsh on-farm environment and to be adaptable to changing operating conditions within the dairy. Keywords: Air filtration, Ammonia, Clinoptilolite, Dairy, Manure, Odor, Zeolite