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Fuel Oxygenates And USTs

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This Web page provides underground storage tank (UST) stakeholders with information regarding the storage of methyl tertiary-butyl ether (MTBE) and other fuel oxygenates. Hypertext links to information created and maintained by other public and private organizations. Please be aware that EPA does not control or guarantee the accuracy, relevance, timeliness, or completeness of this outside information. Further, the inclusion of links to particular items in hypertext is not intended to reflect their importance, nor is it intended to endorse any views expressed or products or services offered by the author of the reference or the organization operating the server on which the reference is maintained.

Fuel oxygenates are a group of chemicals that raise the oxygen content of gasoline. The presence of oxygen optimizes oxidation during fuel combustion, resulting in a more complete burn and a reduction of harmful tailpipe emissions of partially oxidized gasoline components from motor vehicles. In 1990, the Clean Air Act (CAA) Amendments required the use of oxygenated gasoline in areas with elevated carbon monoxide levels and unhealthy levels of air pollution. Two nationwide oxygenated gasoline programs were developed in response to the CAA Amendments. The Winter Oxygenated Fuel Program requires use of gasoline containing 2.7 percent oxygen by weight during cold months in cities exceeding a carbon monoxide threshold. The Year-round Reformulated Gasoline Program requires the use of reformulated gasoline (RFG) throughout the year in cities with the highest ground-level ozone (smog) pollution. RFG contains a minimum of two percent oxygen by weight and is specially blended to contain fewer polluting compounds than conventional gasoline.

MTBE

This section provides published material about methyl-tertiary butyl ether (MTBE) and USTs. Documents in this section cover topics such as remediation, fate and transport, policy, and more.

MTBE is an effective fuel oxygenate that has been increasingly used in place of lead as an octane-enhancing fuel additive in motor gasoline. In order to fulfill the oxygenate requirements set by Congress in the 1990 CAA Amendments, higher concentrations of MTBE have been added to fuel to ensure a more efficient burn of gasoline while reducing emissions. Unlike ethanol, MTBE can be shipped through existing pipelines, and its volatility is lower, making it easier to meet emission standards. MTBE is highly water soluble and does not adhere well to soil particles, which increases the chances of ground water contamination if a leak into the environment occurs. Given the difficulty and high cost of MTBE ground water remediation, efforts to reduce or eliminate MTBE use as a fuel additive have been underway since 2000. Secondary containment and effective monitoring systems are essential to protecting against small volume and undetected releases from a UST.

Other Oxygenates

This section provides published material about fuel oxygenates and USTs. Documents in this section cover topics such as remediation, fate and transport, policy, and more.

Fuel oxygenates other than MTBE are also chemical compounds containing oxygen that are used to boost the octane level in gasoline while reducing air pollution associated with automobile tailpipe emissions. Some of the primary fuel oxygenates are tertiary-amyl methyl ether (TAME), diisopropyl ether (DIPE), ethyl tertiary-butyl ether (ETBE), tertiary-amyl alcohol (TAA), tertiary-butyl alcohol (TBA), methanol, n-butanol, and ethanol. Some reformulated gasoline blends can be highly corrosive to metals, particularly methanol blends, and incompatibility of the stored substance with polymeric tanks can lead to increased tank permeability and leaks. Special precautions are required to ensure compatibility between a reformulated gasoline blend or fuel oxygenate and a UST.

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