Systematic approach to evaluating trade-offs among fuel options: the lessons of MTBE.

The fuel additive methyl tertiary butyl ether (MTBE) has been used in an effort to improve air quality in the United States, but other undesirable effects, particularly the contamination of water resources, were eventually judged to outweigh any air quality benefits it may have offered. The experience with MTBE offers many lessons, including the need to evaluate potential positive and negative environmental impacts associated with fuel choices using a comprehensive approach that combines a product life-cycle perspective with the risk assessment paradigm. Such an approach, referred to as "comprehensive environmental assessment" (CEA), is illustrated here by highlighting some of the issues that might be considered in evaluating reformulated gasoline (RFG) produced with MTBE, ethanol, or no oxygenate.