Compost microorganisms not only convert organic material into humus, but they alsodegrade toxic chemicals into simpler, benign, organic molecules. These chemicals include gasoline, diesel fuel, jet fuel, oil, grease, wood preservatives, PCDs, coal gasification wastes, refinery wastes, insecticides, herbicides, TNT, and other explosives.
In one experiment in which compost piles were laced with insecticides and herbicides, the insecticide (carbofruan) was completely degraded, and the herbicide (triazane) was 98.6% degraded after 50 days of composting. Soil contaminated with diesel fuel and gasoline was composted, and after 70 days in the compost pile, the total petroleum hydrocarbons were reduced approximately 93%. Soil contaminated with Dicamba herbicide at a level of 3,000 parts per million showed no detectable levels of the toxic contaminant after only 50 days of composting. In the absence of composting, this biodegradation process normally takes years.
Compost seems to strongly bind metals and prevent their uptake by both plants and animals, thereby preventing transfer of metals from contaminated soil into the food chain. One researcher fed lead-contaminated soil to rats, some with compost added, and some without. The soil to which compost had been added produced no toxic effects, whereas the soil without compost did produce some toxic effects. Plants grown in lead contaminated soil with ten percent compost showed a reduction in lead uptake of 82.6%, compared to plants grown in soil with no compost.
Fungi in compost produce a substance that breaks down petroleum, thereby making it available as food for bacterica. One man who composted a batch of sawdust contaminated with diesel oil said, "We did tests on the compost, and we couldn't even find the oil!" The compost had apparently "eaten" it all. Fungi also produce enzymes that can be used to replace chlorine in the paper-making process. Researchers in Ireland have discovered that fungi gathered from compost heaps can provide a cheap and organic alternative to toxic chemicals.
Compost has been used in recent years to degrade other chemicals as well. For example, chlorophenol contaminated soil was composted with peat, sawdust, and other organic matter and after 25 months, the chlorophenol was reduced in concentration by 98.73%. Freon contamination was reduced by 84%, PCPs by up to 98%, and TCE by 89-99% in other compost trials. Some of this degradation is due to the efforts of fungi at lower (mesophilic) temperatures.
Some bacterica even have an appetite for uranium. Derek Lovely, a microbiologist, has been working with a strain of bacteria that normally lives 650 feet under the Earth's surface. The chemically altered uranium excreta becomes water insoluble as a result of the microbial digestion process, and can consequently be removed from the water it was contaminating.
An Austrian farmer claims that the microorganisms he introduces into his fields have prevented his crops from being contaminated by the radiation from Chernobyl, the ill-fated Russian nuclear power plant, which contaminated his neighbor's fields. Sigfried Lubke sprays his green manure crops with compost-type microorganisms just before plowing them under. This practice has produced a soil rich in humus and teeming with microscopic life. After the Chernobyl disaster, crops from fields in Lubke's farming area were banned from sale due to the high amounts of radioactive cesium contamination. However, when officials tested Lubke's crops, no trace of cesium could be found. The officials made repeated tests because they couldn't believe that one farm showed no radioactive contamination while the surrounding farms did. Lubke surmises that the humus just "ate up" the cesium.
Compost is also able to decontaminate soil polluted with TNT from munitions plants. The microorgamisms in the compost digest the hydrocarbons in TNT and convert them into carbon dioxide, water and simple organic molecules. The method of choice for eliminating contaminated soil has thus far been incineration. However, composting costs far less, and yields a material that is valuable (compost), as opposed to incineration, which yields an ash that must itself be disposed of as toxic waste. WHen the Umatilla Army Depot in Hermiston, Oregon, a Superfund site, composted 15,000 tons of contaminated soil instead of incinerating it, it saved approximately $2.6 million. ALthough the Umatilla soil was heavily contaminated with TNT and RDX (Royal Demolition Explosives), no explosives could be detected after composting and the soil was restored to "a better condition than before it was contaminated." Similar results have been obtained at Seymour Johnson Air Force Base in North Carolina, the Louisiana Army Ammunition Plant, the U.S. Naval Submarine Base in Bangor, Washington, Fort Riley in Kansas, and the Hawthorne Army Depot in Nevada.
The U.S. Army Corps of Engineers estimates that we would save hundreds of millions of dollars if composting, instead of incineration, were used to clean up the remaining U.S. munitions sites. The ability of compost to bioremediate toxic chemicals is particularly meaningful when one considers that in the U.S. there are currently 1.5 million underground storage tanks leaking a wide variety of materials into the soil, as well as 25,000 Department of Defense sites in need of remediation. In fact, it is estimated that the remediation costs for America's most polluted sites using standard technology may reach $750 billion, while in Europe the costs could reach $300 to $400 billion.
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