Bacteria and fungi living on the media surface eat or oxidize odorous gas before it enters the atmosphere. This works kind of like an air filter. Biofilters need the correct moisture content and food source to stay alive. Biofilters can reduce odor emissions by about 90 percent if managed properly. Add to that the cost to control rodents, which tend to nest in the media, and additional fan-operating costs in the summer.
Windbreak walls are less expensive and perhaps an easier way to control swine odors.
These walls, located 10 to 15 feet beyond the pit fans, create a dead airspace between the facility and the wall where dust settles. The wall causes odorous air to be pushed so far upward that it isn't a nuisance. These walls can easily be assembled using a tarp attached to framework. The walls should be easily reconstructed if knocked down by a windstorm. Windbreak walls are a moderately effective, low-cost odor control technology.