Ethanol fuels may be good for the environment, but not for the pipelines that transport and store them, new research indicates.
Microbiologically Influenced Corrosion (MIC), already a significant problem for pipelines, tanks and other fuel transportation infrastructure, could prove even more challenging in ethanol and ethanol blend environments, according to research by a team at the Colorado School of Mines.
MIC is believed responsible for up to 20% of all corrosion costs and costs the United States billions of dollars each year, the team says.
Lab studies of Fuel Grade Ethanol (FGE) infrastructure have shown the presence of “viable, cultivatable microbes,” including some that can survive even extended exposure to FGE and Ethanol Fuel Blend (EFB) environments, the researchers say.
These spores “may have the capacity to influence corrosion in high ethanol environments, particularly if the steel has manganese as an alloying addition,” the team reported in “Microbiological and Electrochemical Evaluation of Corrosion and Microbiologically Influenced Corrosion of Steel in Ethanol Fuel Environments,” a paper presented earlier this year at NACE International’s Corrosion 2010 Conference and Expo.
Degrading Metals, Polymers
Introducing alternative fuels into systems designed for petroleum and gas service has led to “new material compatibility issues,” the paper reports. Challenges “have become evident, including the degradation of both metals and polymers.”
Because water is highly soluble in ethanol, pipeline transport “may not only result in sub-octane fuel but also leave behind residual quantities of ethanol, water and organic solutions in the lines,” the team reports. Those compounds, in turn, can then feed more microbial communities, leading to yet more decay.
“The bacteria found in (certain) microbial communities are likely utilizing vaporized ethanol fumes as their primary carbon source, and in combination with moisture and humidity, along with tank metals that can serve as electron donors in the presence of oxygen, thrive in these unique environments,” the team said.
MIC is more likely during periods of stagnation or during system upsets, the paper says. The rate of corrosion was found to increase as water was added to pure ethanol, the researchers found.
The researchers also reported the presence of black film on the external surfaces of aboveground storage tanks (ASTs) containing ethanol at different fueling stations. After removal with pressure washing with water or a bleach solution, the film returned within weeks or months, they said.
Adjacent ASTs containing fuels without ethanol were generally free of the films, unless they were downwind of ethanol tanks.
“In some instances, the film was reported to extend over an area reaching considerable distances downwind,” the paper said.
Corrosion causing microbes may survive even harsh conditions and thrive anew when the conditions improve, the team reported.