A biofilter uses moist organic materials to absorb and then biologically degrade odorous compounds. The materials that have been used for biofilter construction include compost, soil, peat, chipped brush and bark and their depth typically ranges from 1 to 1.5 meters. They have been shown to be effective at treating essentially all of the odors associated with composting, including ammonia and a wide range of volatile organic compounds. In many cases biofiltration is both the least expensive and most effective treatment option in controlling odor.