Mitigation of multiple air emissions from swine buildings using corn cob biofilters

Biofilter media selection and moisture content fluctuations significantly influence biofilter performance. Media with significant amounts of small particles have higher static pressure drops which lowers airflow through the biofilter. Inadequate moisture can reduce biological activity and decrease filter efficiency. Too much moisture (following a watering or rainfall event) can plug media pores, restrict airflow through the media, produce anaerobic pockets and generate nitrous oxide (N₂O). In this study, a naturally occurring adsorbent (diatomaceous shale) was tested to manage media moisture content. Also, corn cobs were tested as an alternative biofilter media because wood chips are expected to be less available in near future due to emerging emerald ash borer disease. Five 1 m x 1 m x 1 m biofilter cells were built to treat air from pit fan exhausts of a swine finishing barn. One biofilter cell was filled with wood chips and one was filled with corn cobs. Three other biofilters were filled with corn cobs mixed with 5, 10 and 15% (by volume) diatomaceous shale, respectively. Results showed that all of the biofilters were effective reducing H₂S and NH₃ emissions without generating N₂O. The corn cobs were less dense and more porous than the wood chips and had lower pressure drop values. Adding 15% diatomaceous shale to the cobs helped manage media moisture and improved H₂S and NH₃ reduction efficiencies.