MTBEs Role in Reformulated Gasoline
Today, many of Americas drivers use a cleaner-burning gasoline designed to cost-effectively reduce harmful motor fuel emissions and improve the air we breathe. Introduced in 1995, Reformulated Gasoline (RFG) is used today in the most polluted urban areas in 17 states and the District of Columbia. RFG usage accounts for about 32 percent of the total U.S. gasoline market (i.e. 2.5 million barrels/day).
To achieve clean air, Congress required that RFG contain oxygen, feature no toxic heavy metals such as lead, and reduce harmful toxics such as benzene. As implemented by EPA, the RFG program incorporated additional air pollution reduction standards including caps on nitrogen oxide (NOx) emissions, and overall smog and air toxic reduction requirements that effectively required refiners to limit the use of aromatic compounds and reduce sulfur in gasoline. These fuel composition changes were relatively easy to implement, imposed a modest regulatory burden, and yielded the most significant pollution reduction at the lowest cost. Most importantly, they accomplished the environmental objectives without jeopardizing the nations gasoline supply. That conclusion is still valid today.
By requiring RFG to contain a minimum 2.0 percent oxygen by weight, Congress recognized that oxygenated compounds such as Methyl Tertiary-Butyl Ether (MTBE) enable refiners to reduce air pollution while maintaining octane levels and fuel performance and extending the use of a barrel of oil. In RFG, oxygenates allow for more complete fuel combustion, reduce carbon monoxide emissions during the winter months, smog-forming volatile organic compounds (VOCs) in the summertime, and toxic air emissions year-round. Despite other oxygen choices, refiners have overwhelming turned to MTBE to satisfy the RFG oxygen content requirements.
MTBE is not a new gasoline additive limited only to RFG. It was first used in gasoline in the late-1970s as an octane enhancer to replace lead. MTBEs use in gasoline requires no vehicle or fuel infrastructure changes. Today, estimates show that MTBE is blended to some degree in approximately 30 to 50 percent of all gasoline sold in the U.S., including RFG. In total, MTBE currently makes up about four volume percent of all gasoline sold throughout the U.S., and in certain areas constitutes more than 10 percent of total gasoline volume. This represents the equivalent gasoline production of approximately five average-sized U.S. refineries. With U.S. crude refining capability currently at maximum capacity, MTBEs added volumes are vital to our ability to maintain adequate gasoline supplies and reasonable prices at the pump.
By every measure, clean-burning RFG blended with MTBE has exceeded all pollution reduction goals, substantially and cost-effectively improving the nations air quality. RFG has cut smog-forming pollutant emissions by over 17 percent, the equivalent of removing 64,000 tons of harmful pollution from the air we breathe or taking 10 million vehicles off our roads. RFG has reduced emissions of benzene, a known human carcinogen, by some 43 percent, while reducing total toxic air emissions by about 22 percent. Cleaner-burning MTBE accounts for a large part of the overall emission reductions from RFG. In 1998, the Northeast States for Coordinated Air Use Management found that RFG with MTBE substantially reduced the relative cancer risk associated with gasoline vapors and automobile exhaust compared to conventional gasoline, concluding that todays RFG reduces cancer risk by 20 percent over conventional gasoline. More recently, the California Bay Area Air Quality Management District (BAAQMD) concluded that a substantial reduction in cancer risk in the region is directly attributable to MTBE.
MTBE is a high quality product now used world-wide as an important blending stream for increasing gasoline octane and making cleaner-burning gasoline. MTBE improves air quality leading to better public health, while maintaining vehicle performance at competitive gasoline pricing for consumers.