Researchers from the National Institute of Standards and Technology discovered that bacteria found in ethanol hasten the deterioration and cracking of pipeline steels.
Ethanol is a biofuel that is commonly used as a fuel additive because of its oxygen content and octane rating. Moreover, modified engines used ethanol solely as fuel.
Recently there have been proposals that existing gas pipelines and other infrastructure could be used to transport ethanol and increase its deployment. However, N.I.S.T. researchers exposed common pipeline steel to ethanol and found that ethanol and the bacteria found within can have a corrosive effect.
"Substantial increases in crack growth rates were caused by the microbes. These are important data for pipeline engineers who want to safely and reliably transport ethanol fuel in repurposed oil and gas pipelines," N.I.S.T. postdoctoral researcher Jeffrey Sowards said.
The corrosive bacterium, Acetobacter aceti, is known to occur in alcoholic environments – such as ethanol – and can convert that alcohol into acetic acid. It is used safely in the fermentation industry with no known adverse health effects to humans, animals or plants.
However, the researchers found that, when A. aceti feeds on ethanol the acid produced can boost fatigue crack growth rates in pipeline by at least 25 times the level occurring in air alone.
The team of researchers used a new biofuels test facility to assess fatigue-related cracks in two common pipeline steels dipped in ethanol mixtures, including a simulated fuel-grade ethanol and an ethanol-water solution with the bacteria.
Tow pipeline steels X52 and X70, which are alloys of different metals, were used in the experiment. The researchers found out that simulated fuel-grade ethanol significantly increased the crack growth under typical stress intensity levels on normal operating conditions. The cracking is related to corrosion.
The researchers caution that further study is needed to ensure that ethanol can be safely integrated into existing fuel transport infrastructure.
Tests were also conducted that suggest that a glutaralhyde, a biocide used in oil and gas operations, helped in controlling the growth of bacteria during passage of ethanol in the pipeline.
The findings of the study were presented at the Department of Defense Corrosion Conference 2011 happening this week.
By. K.D. Mariano