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

Biofiltration is a proven method to reduce odor and gas emissions from swine buildings and manure storage units. Biofilter media selection and moisture content fluctuations significantly influence biofilter performance. The purpose of this study was to test corn cobs as an alternative biofilter media because wood chips may become less available in the future due to the spread of emerald ash borer disease. In addition, a naturally occurring adsorbent (diatomaceous shale) was tested as an additive to manage biofilter media moisture content. Five 1 m × 1 m × 1 m biofilter cells were built to treat pit fan exhaust air from a swine finishing barn. A semi-continuous sampling system was used to measure the biofilters' inlet and outlet gas concentrations. Results showed that all of the biofilters were effective, reducing H2S emissions on average by 7.3% to 50.1% and reducing NH3 emissions on average by 9.8% to 86.3%. The corn cobs were less dense and more porous than the wood chips and had lower pressure drop per unit depth. Adding 15% diatomaceous shale to the corn cobs helped manage media moisture and improved H₂S and NH₃ reduction efficiencies. However, after 16 months of media aging, high levels of N₂O generation were observed during two sampling days. The estimated media cost with 15% diatomaceous shale was 0.52 per m3 h^-1 (0.89 per cfm) of air treated. The corn cobs cost (100% corn cob biofilter) was 0.03 per m₃ h^-1 (0.05 per cfm) of air treated.