Prior to the Clean Air Act of 1990, environmental issues regulations were aimed at reducing emissions as they left the exhaust system. The catalytic converter has been the primary means of attacking air pollution in this way. After 1990, regulations for the first time undertook to alter the composition of the fuel itself. Reformulated gasoline applies to gasoline that is sold in the nine metropolitan areas designated by the EPA with the highest level of ozone in air pollution problems. About 48 million people reside in areas where ozone concentrations exceed federal standards.
Reformulation refers to the transformation of gasoline to make it cleaner with respect to emissions environmental. Beginning in 1995, specifications for reformulated gasoline included a 2 percent minimum oxygen content and a maximum content of various organic and inorganic pollutants. In addition, heavy metal additives in reducing gasoline are prohibited. A disadvantage of reformulated gasoline is that it contains 1 to 3 percent less energy per gallon than traditional gasoline.
Many reformulated gasolines use oxygenated compounds as additives. Clean Air regulations specify the need for oxygenated fuel in 39 metropolitan areas with high carbon monoxide concentrations. The regulations for oxygenated fuel are seasonal: during the winter season, gasoline must contain a minimum of 27 percent oxygen. The oxygen helps engines to burn the fuel more completely which, in turn, reduces monoxide emissions. The major additive to supply the additional oxygen to reformulate gasoline to satisfy these requirements is the methanol derivative, methyl tertiary butyl ether (MTBE). Currently, this additive is used in over 30 percent of U.S. gasoline.
MTBE was first used as a fuel additive in the 1940s and was a popular additive in Europe in the 1970s and 1980s. In the late 1970s, MTBE began replacing lead in this country to enhance octane number. In the late 1980s, California led the way in the United States for its use as an oxygenate for clean energy burning fuel. The consumption of MTBE in the United States increased rapidly between 1990 and 1995 with the passage of the Clean Air Act and, a few years later the implementation of the federal reformulated gasoline program. Currently, MTBE is produced at 50 U.S. plants located in 14 states. About 3.3 billion gallons of MTBE, requiring 1.3 billion gallons of methanol feedstock, are blended annually into reformulated gasoline.
In the late 1990s, MTBE came under serious attack on grounds of both efficacy and safety. A report by the National Research Council (1999) stated that the addition of oxygen additives in gasoline, including MTBE and ethanol, are far less important in controlling pollution than emission control equipment and technical improvement to vehicle engines and exhaust systems.
Moreover, MTBE has been found in groundwater, lakes and reservoirs used for drinking water, and it has been linked to possible serious disease. The probable occurrence of cancerous tumors in laboratory rats injected with MTBE alerted federal agencies as to its possible health hazards. In 1999, the EPA reversed itself, recommending the phasing out of MTBE as an additive to gasoline.
During the first half of 2000, MBTE production in the Unites States averaged 215,000 barrels per day. In the same six-month period, the average production offuel ethanol was 106,000 barrels per day. In light of the EPA's 1999 recommendation, ethanol will most likely replace MTBE as an effective oxygenate additive. In addition to its use as an oxygenate, ethanol enhances octane ratings and dilutes contaminants found in regular gasoline.