Carbonating cow manure
Taking the fizzy drink approach to cow manure - in other words adding Carbon Dioxide - could be the next step taken by the livestock industry to reduce the burden of E.coli infection within the food chain

This is the implication of research carried out in the US, which confirms that the harmless ingredient found in soft drinks and some toothpastes suppresses the growth of this potentially lethal bacterium in slurry.

"We know that dairy cows and other cattle harbour E. coli and other disease-causing bacteria, and these pathogens can persist in manure for long periods of time," said United States Agricultural Research Service microbiologist James B. Russell.

"But in lab studies, adding sodium carbonate kills many of these harmful microbes."

Russell's team had been looking for a practical and inexpensive method for treating dairy cattle manure to decrease E. coli and other potential pathogens.

"Bacteria can be killed by chlorination, but chlorinating manure is not practical," said Russell.

"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 faeces - breaks down urinary urea, some carbon dioxide is trapped as carbonate and this alone can kill E. coli. However, dairy cows don't make enough urine to kill the entire population of the bug.

The research team made its carbonation discovery by mixing manure and urine. When the ratio was 1-to-1, virtually all of the bacteria were killed. However, dairy cows typically excrete 2.2 times as much faeces as urine, and E. coli persisted at that ratio.

"If cow manure samples are spiked with sodium carbonate in the laboratory, E. coli populations do not persist," said Russell.

"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 £6 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. This compares with an original count of between 100,000 to 100,000,000 counts per gram.