The U.S. military is touting biofuels as a way to sever itself from diesel and other fossil fuels. While the high cost of biofuel purchases is a major roadblock to the Navy’s “Green Fleet” plans, as Scribe documented on Monday, some observers have noted a more fundamental — and troubling — problem. Biofuels may actually damage military equipment.

Secretary of the Navy Ray Mabus plans to use a 50-50 blend of conventional fuels and biofuels for his “Great Green Fleet,” a Carrier Strike Group composed of a destroyer, tanker and an aircraft carrier that are fueled by alternative energy sources. Mabus plans to have half the Navy fleet on alternative fuels by 2020.

While congressional leaders, including Rep. Mike Conaway (R-TX), have balked at the high costs of biofuels at almost $27 per gallon for 450,000 gallons, other observers note the other problem: potential damage that biofuels could do to the machinery it powers.

Rice University professor Pedro Alvarez examined the unintended consequences that might result from large-scale production and use of bioenergy in the United States, particularly ethanol, in a January 2010 study that he co-authored. The study concluded that there needs to be greater knowledge about the long-term effects of bioenergy before large-scale implementation.

“The overall effect of using biofuels to power maritime vessels,” Alvarez told Scribe, “is high potential for corrosion on their tanks” due to high levels of bacteria in those fuels.

Jason S. Lee, an engineer at the U.S. Naval Research Laboratory, also warned of the potential for corrosion. “Susceptibility of biodiesel to … biodegradation and its propensity to stimulate biocorrosion suggest caution when integrating this alternate fuel with the existing infrastructure,” he found in a 2010 study conducted by the University of Oklahoma and the U.S. Naval Research Laboratory on the impact of biodiesel on metal.

“The blending of biodiesel with traditional diesel resulted in the first known demonstration of localized corrosion of aluminum in the fuel layer itself,” he later told Corr Defense.

2010 study from Fuels, Engines, and Emissions Research Center at the Oakridge National Laboratory in Tennessee raised the same concern. “Dissolved water in biofuels can … contribute to corrosion and stress corrosion cracking. Stress corrosion cracking of mild steel may be of particular concern with ethanol,” the study found.

The Navy did not return multiple requests for comment on the potentially corrosive nature of biofuels on military equipment.

But congressional leaders are concerned.  Rep. Randy Forbes (R-VA), a member of the Armed Services Committee, insists that potential side effects have not been adequately studied. “We have not examined those studies, but like anything else we do, our biggest concern is that we do the analysis before we make huge moves in either direction,” Forbes told Scribe.

The House and Senate Armed Services Committees have approved provisions addressing the cost of biofuels in the 2013 Defense Authorization bill currently making its way through Congress. Conaway authored a provision in the bill prohibiting the Defense Department from buying alternative fuels if the cost outweighs the price of petroleum fuels. It states members’ concern about “fluctuating fuel prices, and the resulting shortfalls and impacts on the operation and maintenance accounts.”

But Forbes noted that the Navy seems less concerned than other branches of the military – particularly the Air Force – with assessing possible unintended consequences of biofuels. “I think the Air Force’s suggestions have been a better approach,” he noted, “which is continuing to do research and development to see if they are going to have any impact on any of the engines.”

“The frustrating thing we’ve had with the Navy at this particular point in time is that they have set these goals that are arbitrary goals,” Forbes added. “They try to establish markets that are artificial markets, but every time we ask them for the analysis to justify, they haven’t given the analysis.”

“If someone comes up with a biofuel mix that works, and it tests and it works OK, then we’re going to buy it. But, we’re not going to artificially push that,” said Forbes.

Melanie Wilcox is a member of the Young Leaders Program at The Heritage Foundation.