Biofiltration for odour control from swine housing in Manitoba

Abstract

Biofiltration is an odour removal technology in which an odorous air stream is passed through a moist, porous medium prior to emission into the atmosphere. Odorous compounds are removed in the filter medium through absorption and bio-oxidation. Four experimental biofilter units were retrofitted to a 2000-hog, 4 room feeder facility in southern Manitoba. The biofilters were designed to eliminate odour from the barn emissions during the winter while minimizing cost. The biofilter bed temperature remained in a temperature range suitable for odour removal, even during very ambient temperatures below -20C. Odour removal efficiency from September to February averaged between 69 and 87%. Ammonia and hydrogen sulfide levels were reduced by 56 to 100%. Different air distribution and biofilter media combinations resulted in little difference in odour reduction. This project demonstrates that biofiltration is a viable odour emission reduction technique for mechanically ventilated swine housing in the cold Canadian climate. Additionally, two experimental biofilters were constructed to determine whether the biofilter media material contributed a residual odour to the outlet air from the biofilters. Six different blends of compost and bulking agents were used at two different retention times and were found to have low residual odour levels. Outlet odour levels at or below ambient farmyard odour levels were found for all varieties of compost blended in a 50%/50% mixture (by mass) with woodchips, as well as for a 50/50 mixture of hemp hurds and compost. Outlet odour levels did not differ significantly for odorous and non-odorous air biofilters, indicating that it was not the processes associated with biofiltration that caused the residual odours.