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.