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Kenaf Core as an Enhancer of Bioremediation
A. Borazjani and Susan Diehl
The wood treatment industries have been in operation in the United States for more 100 years. Two of the more potent and most commonly used wood
preservatives are pentachlorophenol (PCP) and creosote. These preservatives are used to treat wood products such as crossties, utility poles, marine piles, and structural lumber.
Before federal and state laws regulated the use of these preservatives, misuse in the handling, accidental spillage, and improper disposal of creosote
and PCP led to large areas of contaminated soils and water. Industrial sites contaminated by past use of PCP and creosote are being cleaned up by nature's own bacteria and fungi.
Research by the Environmental Biotechnology Group of the Mississippi Forest
Products Laboratory (MFPL) is identifying microorganisms and methods of carrying out this process, which is called bioremediation. During this process, contaminants (such as PCP, creosote, and petroleum products) can be converted to harmless byproducts, such as carbon dioxide and water. Bioremediation is far less expensive when compared to other cleanup methods, and it does not require transport of hazardous wastes through cities and communities. The soil itself is not destroyed, and unlike incineration, bioremediation does not produce hazardous ashes. Bioremediation has been approved by the Environmental Protection Agency (EPA) as the cleanup method for more than 20 abandoned woodtreatment facilities.
One problem encountered when using bioremediation on contaminated soil is the
soil environment often does not encourage the bacteria and fungi to degrade the pollutants. Pollutants often absorb to soil particles in such a way that the microorganisms cannot come in contact with them. This makes the pollutants unavailable for breakdown. Other environmental factors that greatly influence breakdown rates include temperature, oxygen, nutrient availability, pH, moisture content, light intensity, and organic matter. Many of these environmental factors can be controlled by a process called landfarming. Landfarming is the treatment of contaminated soil using conventional soil management techniques such as tilling, irrigation, and fertilization to enhance microbial degradation ofpollutants.
Researchers at the MFPL have been looking at different ways to speed bioremediation of contaminated soil by altering the soil environment. One way
to alter the soil environment, and hopefully enhance pollutant breakdown, is through the addition of organic matter. Kenaf has been shown to have an excellent ability to absorb oil, equal to the
best synthetic organic products. Kenaf fines also contain many pores, which will not only absorb the oil, but also allow for less leakage or release of oil once absorbed, and will allow much
greater contact between the oil and the microorganisms. Kenaf is also biodegradable, high in protein, and contains very large numbers of natural microorganisms.
Preliminary studies at the MFPL have found that kenaf absorbed over 55% of
the oil from oilcontaminated soil. Removal of pollutants from soil particles by the kenaf should make the pollutants more available to the microorganisms, thus enhancing pollutant breakdown. In addition, the leaching potential of kenaf appears to be low, with only 0.02% of the oil leaching from contaminated kenaf. This means that once the pollutant is absorbed to the kenaf, only a very small amount will leach from the kenaf into the groundwater.
Microorganisms native to kenaf were able to biodegrade 55% of the oil from contaminated kenaf. Thus the kenaf itself may provide more microorganisms
to assist in the bioremediation. We believe that kenaf has a great potential as an effective enhancer of bioremediation of organic woodtreating wastes because of
its biodegradability, excellent sorbency, cost, size, and environmental friendliness. Because of these capabilities, researchers at the MFPL are exploring the use of kenaf to enhance microbial degradation of soil contaminated with PCP and creosote.
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A. Borazjani is an Assistant Professor and Susan Diehl is a Research Scientist I, Mississippi Forest Products Utilization Laboratory, Mississippi State University.
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