Biofiltration has been adapted for use on livestock farms and can reduce odour and hydrogen sulfide emissions by as much as 95% and ammonia emissions by up to 80%. Biofilters are simply a bed of organic material, typically a mixture of compost and wood chips, which are about 10-18 inches deep. As air passes through the biofilter, the microbes on the organic material convert odorous gases to carbon dioxide and water. The effectiveness of this system depends on the time the air spends in and the moisture content of the biofilter. A typical biofilter require 50-85 square feet per 1000 cubic feet/minute (cfm) of airflow. Construction costs range from $100-150. 1000 cfm. Operation and management costs are around $3.00/1000 cfm/ year.
Biofilters can be used in mechanically ventilated building, where an exhaust fan must be attached to an air duct to bring air into the biofilter. They can also be used in naturally ventilated buildings. In these, air that is exhausted through the pit fans passes through the biofilter but air that does not go through the pit fans does not reach the system. This means that in cold weather, when pit fans are being used, biofilters are 95% effective but in warm weather, other ventilation systems are used and therefore the biofilter does very little. A final area in which biofilters can be used is in covered manure storage. If it is covered with an impermeable layer then a ventilation system is put into place and a biofilter can clean up this vented air.