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. Ultimately, that cost will be passed on to the consumer in the price of lumber," Diehl said.
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. It could be better because of the absence of secondary by-products," Diehl said. "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.
Diehl said biofilters are designed for contaminants in the air, not the soil or water. Volatile organic compounds are emitted from the wood in the drying process. Unlike the gases produced in the incineration process, biofiltration only produces naturally occurring gases such as carbon dioxide, similar to the gases produced from a composting process.
"Biofiltration has been used in other industries where they have been more successful than in the forest products industry," Diehl said. "MSU's Forest and Wildlife Research Center is conducting research specifically for forest products conditions. We are trying to develop the best conditions for the microorganisms to grow and degrade the contaminants in the airstream."
Diehl's research receives funding from the U.S. Department of Agriculture and state allocations. In 1999, the forestry industry was the second largest agricultural industry in Mississippi with a farm gate value of $1.3 billion. Poultry was No. 1 with a value of $1.49 billion.