Ethanol by-product raising concerns
Jul 15, 2009 10:06 AM, By Jim Langcuster, Auburn University
The problem is that these antibiotics not only linger following distillation, but also appear to be passed along to cattle in the distiller's grain.
Sometimes technology produces unintended consequences. That appears to be the case with an ethanol by-product, known as distiller's grain, which is fed to cattle as a corn replacement.
Here's the rub: Several studies indicate that distiller's grain contains yet another by-product of the distillation process associated with ethanol production: Antibiotics.
Why are antibiotics used in the distillation of ethanol in the first place? The distillation process requires a combination of enzymes and yeast to convert corn into ethanol. Sometimes, though, bacterial organisms present during distillation can out-compete yeast in the breakdown of this sugar.
"This is what you don't want," says James Hairston, the Alabama Cooperative Extension System water quality coordinator. "The acid produced by bacteria wipes out the yeast."
What you end up with is lactic acid rather than a high level of ethanol."
Instead of fuel, you end up with corn mash.
The easiest way to address this problem is to introduce antibiotics to kill the bacteria, Hairston says.
The problem is that these antibiotics not only linger following distillation, but also appear to be passed along to cattle in the distiller's grain.
Hairston says there already is a concern about the use of antibiotics in feed associated with concentrated animal feeding operations.
He and other water-resource experts — not to mention many in the nation's medical establishment — fear that minute traces of antibiotics in animal waste can wash into water resources and ultimately affect the quality of drinking water and possibly even our health.
Indeed, a growing number of medical authorities fear that minute traces of antibiotics in drinking water promote the growth of antibiotic-resistant bacteria, the most serious of which are potentially deadly antibiotic-resistant bacteria known as Methicillin-resistant Staphylococcus aureus (MRSA).
Water treatment facilities are currently not equipped to remove these antibiotic traces from drinking water, Hairston says.
Medical researchers are currently unsure of the extent to which these small traces of antibiotics in drinking water may contribute to the growing problem associated with antibiotic resistance.
Until now, the U.S. Food and Drug Administration has adopted a laissez faire attitude regarding the use of antibiotics in ethanol distillation.
But this may change. Samples of distiller's grain requested from 60 ethanol plants revealed the presence of four types of antibiotics: penicillin, virginiamycin, erythromycin and tylosin.
A decision by the FDA to curtail the use of antibiotics in distiller's grain could have far-reaching effects on the ethanol industry, which, because of the slump in demand for ethanol fuel, increasingly depends on its sale of this product to the livestock industry.
Currently, an estimated third of corn in distillation ends up as distiller's grain.
Likewise, distiller's grain has become a mainstay of the cattle industry.
"Distillers grain is considered a high-quality corn substitute — anybody in the livestock industry will agree," Hairston says. " And it's largely the reason why ethanol processors have managed to survive since the slump," Hairston says.
Over the next few weeks, the FDA intends to inspect more samples of distiller's grain. A report on its findings is projected for release later this summer.
If the agency cracks down on antibiotic use, Hairston says the ethanol industry may have a tough time developing a substitute.
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