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Carbonating Cow Manure, The Latest Strategy in Fighting E. coli and other Microbes
By Hank Becker
February 9, 2000
WASHINGTON, February 9, 2000--A harmless ingredient found in soft drinks and some toothpastes suppresses the growth of Escherichia coli in cow manure, U.S. Department of Agriculture and Cornell University scientists reported today.
"Some cattle harbor E. coli O157:H7 and other disease-causing bacteria, and these pathogens can persist in manure for long periods of time," said Agricultural Research Service microbiologist James B. Russell. "But in lab studies, adding sodium carbonate kills many of these harmful microbes." ARS is the chief research agency of USDA.
Russell works at the ARS U.S. Plant, Soil and Nutrition Laboratory in Ithaca, N.Y., and is affiliated with the Nutrient Conservation and Metabolism Laboratory at Beltsville, Md. Russell collaborated with postdoctoral fellows Francisco Diez-Gonzalez and Graeme Jarvis, and with undergraduate student David Adamovich in Cornell's Department of Microbiology on the research.
Russell's team had been looking for a practical and inexpensive method for treating dairy cattle manure to decrease E. coli O157:H7 and other potential pathogens.
"Bacteria can be killed by chlorination, but chlorinating manure is not practical," Russell said. "Laboratory tests indicated that E. coli was resistant to alkaline pH and ammonia, but it was very sensitive to carbonate if the pH was alkaline."
Carbonate can be derived from urine. "When urease--an enzyme in feces-- breaks down urinary urea, some carbon dioxide is trapped as carbonate. Urinary carbonate alone can kill E. coli, but cows don't make enough urine to kill all the E. coli," Russell said. The ARS-Cornell team made its discovery by mixing manure and urine. When the ratio was 1-to-1, virtually all of the E. coli were killed. However, dairy cows typically excrete 2.2 times as much feces as urine, and E. coli persisted at that ratio.
"If cow manure samples are spiked with sodium carbonate in the laboratory, E. coli do not persist," Russell said. Some sodium hydroxide is also added to make sure that the pH is at least 8.5, but "the estimated cost of this treatment would be only $10 per dairy cow per year," he said.
Russell indicated that "after only 5 days, the E. coli count was less than 10 cells per gram." Because the manure samples originally had from 100,000 to 100,000,000 counts per gram, "carbonate appears to be an extremely effective antibacterial agent," Russell added.
Cattle manure is often stored outdoors in large tanks or ponds prior to spreading on fields, but "a threefold dilution with water did not diminish the effectiveness of carbonate treatment," Russell said.
While this process looks very promising in the laboratory, "pilot and farm-scale testing will be needed before the technology can be recommended to the livestock industry," he added.
Laboratory experiments also indicated that carbonate killed other bacterial pathogens such as Salmonella typhimurium, Streptococcus pyogenes, Klebsiella pneumoniae, and Staphylococcus aureus. This research is reported in volume 34, issue 7 of Environmental Science and Technology.
Scientific contact: James B. Russell, U.S. Plant, Soil and Nutrition Laboratory, Ithaca, NY; phone (607) 255-4508, fax (607) 255-3904, firstname.lastname@example.org.