Ethanol Likely Causing Storage Tank Corrosion: Regulators

An uptick of ethanol in petroleum may be triggering new corrosion problems in underground storage tanks, a group of environment regulators said Oct. 27.

States face challenges in diagnosing and addressing new corrosion trends, Mahesh Albuquerque, a Colorado Department oil and public safety official, and other state representatives said at an Association of State and Territorial Solid Waste Management Officials summit.

The ethanol in petroleum may be incompatible with the tank fiberglass and steel construction materials, those representatives said. Water may cause corrosion as well, they said.

There are more than 560,000 underground tanks containing petroleum and other hazardous substances nationwide, the Environmental Protection Agency estimates. Any tank and connected piping with at least 10 percent subterranean combined volume is defined as “underground,” according to agency regulators.

EPA officials, along with the private sector, are still developing solutions to new corrosion trends, an agency official said.

Ethanol Focus

Statutory and regulatory changes, including the EPA’s Renewable Fuel Standard program, have ramped up ethanol concentrations in petroleum over the past decade, causing a decrease in sulfur-related corrosion safeguards, the regulators said.

Nearly all U.S. petroleum-based diesel now must qualify as “ultra-low sulfur,” meaning it contains sulfur at 15 parts per million or less.

"[Sulfur] acts as a natural anti-oxidant, and when you diminish that you allow oxidation to take place a little more rapidly. Oxidation on metal is rust,” Albuquerque said. “That may explain what we’ve seen in tanks.”

The EPA official, Ryan Haerer with the tank Release Prevention Division, echoed that tentative linkage but cautioned that other factors are likely at play. A prime factor is water infiltration, he said.

“Basically if your fuel is not clean and not dry, there is a closer chance of having issues,” Haerer said. “But it certainly seems feasible that biofuels could be a component feeding microbial corrosion.”

Corrosion-Induced Leaks

Still, corrosion prevalence is undebatable, he said, adding that recent findings suggest more than 80 percent of underground storage tanks are moderately or severely corroding.

Corrosion is likely causing common fuel leaks, and owners often aren’t aware, Haerer said.

An EPA trust fund dedicated to leaking tanks facilitates, enforces and pays for leak cleanups, while also providing money for inspection and other release prevention efforts. The fund is financed by a 0.1 percent tax on each gallon of motor fuel sold nationwide. ExxonMobil Corp., Chevron Corp. and Texaco Inc., among a range of other fuel suppliers, pay the tax.

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