By Val Maloney

It is no secret that environmental issues are on everyone's mind and people in the wood industry are no exception. The Environmental Protection Agency (EPA) in the U.S. has introduced Maximum Achievable Control Technology (MACT) standards for the reduction of emissions and, according to industry insiders, legislation in Canada is also in the works. The question then lies with companies on just how they are going to meet these standards. One of the options is bio-oxidation which, simplified, is a technology based on microbes that can remove both water-soluble and non-water soluble emissions from the air when it is passed through the bio-oxidation system.

MACT rules have been in development by the EPA with input from APA-The Engineered Wood Association for quite some time, says Lisa Bailey, a research technologist with the APA in Tacoma, Washington. The rules fall under the Clean Air Act in section 112, and establish standards requiring the maximum degree of reduction in emissions of hazardous air pollutants. Set at 90 percent removal of hazardous air pollutants (HAPs), the number was arrived at by looking at the dose and toxicity of the emission and calculating the risk it posed to the nearest person, called "compliance based on risk." While MACT standards are now in place, industry and the EPA are currently working on what is being called MACT two, following a court decision in a lawsuit by the National Resource Defense Council who said the risk option was not legal.

Bio-oxidizers are one way for companies to comply with these rules and control emissions and Bio-Reaction Industries in Tualatin, Oregon manufactures these systems. Karl Mundorff, President and CEO, says the main reason the company began making the systems was "energy conservation and lowering the carbon footprint."

The first applications of bio-oxidation began in the 1960s and were largely on odor control and wastewater treatment plants, says Dr. Jim Boswell, senior scientist with Bio-Reaction Industries. In the 70s and 80s, European countries, especially Belgium, Germany and France, began using the technology on commercial and industrial applications. The technology started being used in the US during the late 1980s. Bio-Reaction installed its first unit, a 40,000 CFM multi-stage particleboard unit in Oregon, in 2001 and is currently installing 10 systems designed to meet MACT standards, says Boswell. 

Bio-Reaction Industries has modified its bio-oxidation units from the original design, explains Boswell. The microbe system consists of three stages, the bio-trickling filter, bio-matrix chamber and sump. The bio-trickling filter makes up one-third of the system's size and media. This stage houses cross-flow media that has an open design to promote uniform distribution of the air. The media also supports microbial growth. This first stage is where the simple compounds that are easy to break down, such as alcohol, are eaten by the bacteria. Like us, says Boswell "the bacteria prefer to eat things that are easy to digest and not that good for them, so it's best to get them out of the system in the first stage so the more complex things can be eaten in the second stage of the process."

The second stage known as the bio-matrix chamber makes up the other two-thirds of the system and is where more complex compounds such as terpene, pinene and benzene are consumed by the microbes. The time it takes for the microbes to destroy more than 90 percent of the compounds can be as little as eight seconds for water soluble compounds. On tougher compounds it can be 20-45 seconds for 75-85 percent destruction. This stage where tougher compounds are disposed of is made of Bio-Reaction Industries' patented structured biospheres. These spheres are filled with compost and provide a medium where the biological colonies can reside because of the mulch that has micronutrients to keep the microbes healthy.

The third part of the bio-oxidation system is the sump, which continuously re-circulates water throughout the system through the crossflow media that humidifies and removes water-soluble compounds.