The Subsurface Fate of Ethanol, A Look at the Emerging Oxygenate Alternative to MTBE, LUSTLine Bulletin 36

In response to the widespread contamination caused by MTBE-blended reformulated gasoline (RFG), legislative initiatives in several states and at the federal level have phased out, or are trying to phase out, the use of MTBE as a gasoline oxygenate. Ethanol is currently the most likely gasoline oxygenate alternative to MTBE. This potential for increased use of ethanol has been most widely acknowledged by California. The California Executive Order requiring the phase-out of MTBE also required that an analysis of the fate, transport, and health risks associated with the use of ethanol as a gasoline oxygenate be conducted. It is clear that California and many other states now recognize the need to understand the environmental fate of gasoline oxygenates before any policy decisions are made regarding their widespread adoption. The material included in this article begins to summarize findings of the study completed for California. The full report is available at http://www-erd.llnl.gov/ethanol/. The primary physical and biological properties of ethanol that have implications for groundwater contamination are identified in this article. Future articles will focus on the uncertainties in our understanding and research required to make sound policy decisions. (For an overview on ethanol, see LUSTLine #32, June 1999, “With the Possible Phase-Out of MTBE, What Do We Know About Ethanol?” by Bruce Bauman.)