Biofilters may be the key to protecting Mississippi's air quality and wood industry as each new decade brings stricter regulations to protect the environment. Susan Diehl, associate professor with the Forest Products Laboratory at Mississippi State University, said the 1990 Clean Air Act focused on air emissions from dry kilns and wood presses. The Environmental Protection Agency has mandated use of multimillion dollar incineration units on kilns for all new companies and those not in compliance with air quality standards. Most lumber is dried in a kiln, and the cost of drying has gone up tremendously because of the environmental concerns. Incineration units heat the gases from the kiln to a level that will destroy all contaminants.
Units are expensive to obtain and maintain.
Without incineration units or biofilters, the venting gases contribute to poorer overall air quality. The goal of a biofiltration system is to provide equally good or better methods for cleaning air after drying wood. Any type of combustion will create some of the same gases that cause air pollution, such as carbon monoxide, nitrous oxides and sulfur oxides. In the Forest Products Lab biofilter, water and microorganisms are added to the principle ingredient, shredded bark, which provides solid support for the growth of microorganisms that break down gases. Steam and gases that come from the wood during the kiln's drying process are forced through the filter to clean the air.