Recent actions taken by the US Environmental Protection Agency-as well as those taken by certain state governments-have thrust the debate over the use of methyl tertiary butyl ether as a gasoline additive back into the public spotlight yet again. Suffice it to say, the fate of the oxygenate's role in the US gasoline pool weighs heavily in the balance.
For some, only through banning the compound's use outright would a solution be reached to prevent future groundwater contamination from leaking gasoline storage tanks. Others would contend that the banning of MTBE is premature, and that there exist technologies to rid the contaminant from the affected soil and water.
Current events
Certain current events have kept the topic of MTBE fresh in the public's mind.
In June, EPA denied an April 1999 request by California Gov. Gray Davis to waive the federal 2.0 wt % oxygen content requirement for reformulated gasoline. The request for a waiver came because the state had decided to ban the use of MTBE as an oxygenate beginning in 2003 and remained concerned about the supply and price of the only widely available commercial oxygenate substitute, ethanol (OGJ, June 18, 2001, p. 28).
EPA Administrator Christie Whitman said the ruling was based on the conclusion that there was "significant uncertainty over the change in emissions that would result from a waiver." Whitman went on to say that EPA considers the need for clean air and clean water equally important and that the benefit of one should not be pursued at the expense of the other.
A month later, Illinois joined a small, yet significantly rising, number of states pushing to ban MTBE's use, manufacture, and sale as a gasoline additive. Through the signing of the MTBE Elimination Act, Illinois Gov. George H. Ryan vowed to "protect Illinois's groundwater and provide a financial boost to the state's farmers."
MTBE vs. ethanol
MTBE was first added to gasoline as a way of curbing carbon monoxide emissions while increasing fuel octane. The additive, which some believe to be a possible carcinogen, later was detected in numerous groundwater sources in some parts of the US. Over time, these various contamination discoveries served to fuel a movement aimed at halting the additive's use and replacing it with an alternative oxygenate. Enter ethanol.
Proponents of corn-derived ethanol tout numerous benefits over MTBE. Meanwhile, its skeptics maintain that the benefits of mixing gasoline with ethanol, however numerous, are potentially outweighed by some noteworthy drawbacks. Because ethanol already blended into gasoline has an affinity for water, it cannot be shipped via conventional products pipelines. The fuel must be shipped via trucks to refineries to be used as a blendstock, which creates concerns over fungibility.
In California, for instance, state officials carry justifiable concerns about supplying enough ethanol to meet yet-unforeseen demand.
Meanwhile, ethanol's price volatility remains another source of angst. There are concerns about its viability without the 54¢/gal tax credit it enjoys.
MTBE remediation
Perhaps MTBE's shining light of hope may come from those striving to use something from nature to purify something from industry.
Standing tall-and all but waving the flag in the middle of the crowd-among those in the "banning MTBE is premature" camp are specialists who have perfected the use of microbes to treat sites contaminated by MTBE.
US Microbics Inc. unit Sub-Surface Waste Management Inc. (SSWM) of Carlsbad, Calif., recently launched a program to supply carbon filtration service firms with microbial blends, which serve to eliminate MTBE in carbon-treatment systems. In turn, retail service stations will use these carbon-treatment systems to perform groundwater cleanup programs.
SSWM said that, according to statistics from the American Petroleum Institute, of the roughly 180,000 active retail service stations in the US, 73% had reported releases of gasoline containing MTBE.
"MTBE has seen national attention due to its potential ban or phase-out in many states caused by inadvertent releases of petroleum products and the lack of a suitable technology to reduce MTBE contamination to regulatory levels," said Robert Brehm, US Microbics CEO.
"The technology was successful in treating MTBE, benzene, toluene, xylene, ethylbenzene, and gasoline with concentrations over 10,000 ppb," SSWM said.
"We believe these excellent results are directly applicable to the cleanup of MTBE-contaminated soil and groundwater using aboveground tank treatment or an engineered subsurface injection-recovery system to deliver our proprietary mi- crobes to treat contaminated zones," it said.
Ethanol proponents like to tout their fuel as a "natural," renewable resource. Can't the same be said about microbes?
