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EETD Scientists Aid Research Efforts Leading to MTBE Ban

In a recent action, California Governor Gray Davis banned the use of the gasoline-oxygenating additive MTBE (methyl tertiary-butyl ether) because it poses a serious threat to groundwater. Following this action, the U.S. EPA has also opposed the use of MTBE.

Instrumental in the governor's move was a report prepared by EETD and UC Berkeley researchers that examined the usefulness of fuel additives. Don Lucas and Bob Sawyer of the Advanced Energy Technologies Department, along with Cathy Koshland of the University of California at Berkeley and graduate student Pam Franklin performed research that contributed to the report the Governor and the California Air Resources Board used. On a national level, work by EETD scientist Nancy Brown and others were part of a National Research Council published report on oxygenated fuels; that report played a part in the EPA's decision to ban the additive. Bob Sawyer was also a member of the EPA Blue Ribbon Panel on MTBE and other oxygenates in gasoline.

In preparing data for the report to the Governor, Lucas and his colleagues examined claims that MTBE helps internal combustion engines burn gasoline more cleanly. (Refiners began adding MTBE or other additives—among them other ethers or ethanol—to gasoline several years ago to meet stringent air-quality standards and other requirements of the Clean Air Act.) Their research showed that while reformulated fuels reduced air emissions, the oxygenates were not needed. The researchers evaluated three types of reformulated gasoline: one without an added oxygenate, one with ethanol, and another with MTBE. The nonoxygenated fuel was the least costly to produce, while the fuel with the MTBE additive was judged to have the highest net annual cost primarily because of the associated costs of treating contaminated water supplies, higher fuel prices, and lower fuel efficiency.

Greater Dangers

The ineffectiveness of fuel additives is only half the story. Because MTBE is highly soluble, any leaks from underground fuel tanks or pipelines in the gasoline-distribution system pose a great threat to groundwater. Even in small amounts, MTBE renders drinking water unusable, since MTBE can be detected by humans at concentrations as low as 20 parts per billion. Leaks from underground storage tanks or surface spills can contaminate huge reservoirs of drinking water. Given the use of gasoline-burning motors in boats—especially older two-stroke models—drinking water from reservoirs that allow recreational boating is also susceptible.

Recommendations for the Future

Although Lucas agrees with the gradual phasing out of MTBE from gasoline, he is not quick to support replacing it with ethanol. "A lesson to be learned from the MTBE story is that the addition of any chemical compound to the environment in quantities that constitute a significant fraction of the total content of gasoline may have unexpected environmental consequences," he stated. He would like to see refiners given the flexibility to achieve air-quality objectives without wide-scale production of reformulated gasoline required to contain oxygenates. This would require a waiver from the federal government to allow nonoxygenated gasoline to be sold in all parts of California. "Promoting the accelerated removal of older, high-emitting vehicles to reduce air-pollutant emissions would be significantly more cost-effective than mandating the use of oxygenates in fuels," says Lucas. He also suggests implementing an aggressive program aimed at gross carbon monoxide polluters. "This, too," he states, "would be a cheaper and less risky option than using oxygenates." The UC report also emphasizes the need for underground storage cleanup funds and serious efforts to contain or remedy any known or suspected sites contaminated with MTBE.

— Ted Gartner with Don Lucas

For more information, contact:

  • Don Lucas
  • (510) 486-7002; fax (510) 486-7303

This work is supported by the U.S. Department of Energy, Basic Energy Sciences Division, and the State of California, funded under SB521.

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