Maine also opted out of RFG before the program went into effect in More information is provided below. A proposed rule to remove the above "opt-out" areas from the requirements of the reformulated gasoline program was published June 14, On July 1, this stay was extended until the Agency took final action]. The final rule, published July 8, [61 FR ], formally removed these areas from the list of RFG covered areas and provided states with general opt-out procedures.
Skip to main content. Gasoline Standards. Contact Us. Reformulated Gasoline. The nine RFG covered areas required by 42 U. RFG covered areas based on being reclassified as Severe ozone nonattainment areas under 42 U. RFG covered areas based on being classified ozone nonattainment areas at the time that the state requested to opt into RFG under 42 U.
Clair Missouri Franklin, Jefferson, St. Charles, St. Louis St. In the Northern Virginia area, EPA guidance does not require states to estimate the benefits from specific control programs for the types of clean air plans needed in that area. These requirements mandate that control programs must remain in place after air quality improves so that air quality does not back-slide into unhealthy ranges.
States have the option of supplying substitute programs, which must have similar environmental benefit. Due to the emission reductions associated with RFG, finding and implementing equivalent beneficial programs that are cost-effective would be difficult. Maintaining current control programs is even more important in light of the fact that in EPA promulgated a more stringent ozone standard of 0.
Air quality in Hampton Roads and Richmond-Petersburg currently complies with this health-based standard. However, air quality in Northern Virginia is above this standard. As industrial facilities reduce emissions, emissions from on-road and non-road engines are becoming increasingly important to maintaining and improving air quality. In , Congress passed the Energy Independence and Security Act, which requires increased use of renewable fuels like ethanol in transportation fuels.
Within this regulatory context, fuel composition has typically been defined by specifications set as a range of properties, each having a maximum or minimum or both stipulated.
Fuel volatility and distillation are related to the composition of vapors in the gasoline tank and in the fuel delivery system. They are critical to the proper operation of the engine. For example, a sufficiently high "front end volatility" is required for cold starting a vehicle and is generally higher in the winter than in the summer. Those temperatures are represented by T 10 , T 50 , and T Octane number is a measure of the tendency of a fuel to detonate during combustion in a standardized variable-compression-ratio "knock"-test engine in which the compression ratio 1 is increased until knock is de-.
The test results for a fuel are scaled to an octane number of zero for n -heptane and for isooctane 2,2,4-trimethylpentane. The sets of measurement conditions generally applied for determining each octane-rating component are summarized in Table With the phasing out of tetraethyl lead from motor gasoline, changes in composition were necessary to maintain the octane number of the unleaded gasoline so that the current and future fleets of passenger cars could operate properly.
This was accomplished by increasing the content of high-octane hydrocarbons such as alkylated aromatics, olefins, and branched paraffins. Oxygenated compounds e. The major components of gasoline are hydrocarbons, whose elemental make-up includes only carbon and hydrogen. For a variety of reasons, including a desire to minimize motor-vehicle pollutant emissions, a small amount of chemically-combined oxygen is sometimes incorporated into the fuel by adding an oxygenated organic compound to the blend.
The amount of oxygen in a fuel is usually expressed in terms of the percent of oxygen in the fuel by weight i. Note that because ethanol contains more oxygen on a per-gram basis than. Because the octane numbers for both ethanol and MTBE. Except where mandated by law, however, oxygenate producers compete with conventional refining processes for producing high-octane hydrocarbons that can be added to gasoline.
These conventional processes include the following:. Studies indicate that fuel RVP increases as ethanol is initially added.
In general, those processes can be more economical than those that produce oxygenates; and thus, oxygenates were not initially the additive of choice for enhancing octane number in fuels, as discussed later in this chapter. However, in addition to enhancing octane number, oxygenates in gasoline can provide air-quality benefits.
For example, as discussed in Chapter 4 , use of oxygenates can lower emissions of CO during open-loop operation such as warm up in modern vehicles i. There is also some indication that oxygenates can lower the mass and reactivity of VOC exhaust emissions in some cases see Chapters 6 and 7.
The presence of oxygenates in reformulated gasoline has been mandated by law and regulation, and this provides the incentive for using oxygenates to boost octane number instead of using components produced by conventional processes.
All things being equal, the choice of which specific oxygenate to use would be dictated by economic factors; that is, which oxygenate can produce the desired gasoline characteristics e.
The principal production method for ethanol used in gasoline is fermentation of carbohydrates from grain mostly corn :. Ethanol is also produced in petrochemical facilities through ethane-ethene synthesis:. MTBE, on the other hand, is produced in a two-step process, with petrochemical synthesis employed to manufacture methanol from natural gas:.
This multistep process makes use of readily available inexpensive feedstock and enables MTBE to be produced at a cost that is generally less than that of producing ethanol by grain fermentation.
However, in the United States, tax subsidies have made ethanol production via fermentation competitive with MTBE production. Because the committee was not asked to address this aspect of the RFG issue, the economic implications of using MTBE versus ethanol as an oxygenated additive are not discussed in this report.
A discussion of the potential air-quality benefits of the two oxygenates is presented in Chapter 7. Sulfur combined chemically in the organic components of the fuel is a trace impurity of gasoline. Reductions in gasoline sulfur content can substantially improve catalytic-converter performance AQIRP , as well as lower sulfur dioxide SO 2 emissions.
Sulfur's effect in impairing the function of a catalytic converter by poisoning the catalyst is believed to be reversible. Removal of sulfur to a low weight-percent of gasoline i. The first federally mandated gasoline reformulation in recent history was the staged removal of the octane-enhancing additive tetraethyl lead from all motor gasolines.
In general, the function of the oxidizing exhaust catalyst of a vehicle is impaired when the vehicle is operated with leaded gasolines. In anticipation of the introduction of catalysts to the light-duty motor-vehicle fleet in , the U.
A subsequent EPA rule restricted the lead content of any gasoline to a maximum 0. Up to , trace amounts of lead up to 0. Because lead had been in gasoline for many years to enhance combustion performance Coy increasing its octane rating or antiknock index , a comparably effective substitute additive was desired. Initially, lower paraffins, such as butane, offered the combination of octane enhancement and cost-effectiveness that refiners sought because they boosted the rating sufficiently at relatively low concentrations.
However, butane in particular evaporated readily, having an RVP of about 58 psi and also volatilized other reactive hydrocarbons in the gasoline. The result was an industry-average gasoline with an RVP as much as 2 to 3 psi higher during the ozone season than that of the EPA certification test gasoline. Through about , discrepant volatility was not an issue because excursions of the 1-hr ambient ozone concentration standard of 0. However, the summer of witnessed some of the worst ozone excursions on record see Chapters 4 and 6.
These excursions were widespread and often of long duration because of unusually protracted hot and sunny conditions and air stagnation over much of the nation. The ozone excursions led to speculation that evaporation of the then-common high-volatility summer gasoline, in use and in bulk storage, was a major contributor to the mass of VOC emissions giving rise to these ozone episodes. A seminal compendium of peer-reviewed research results, at that time, identified reduction of gasoline volatility as the most effective means then available to reduce anthropogenic VOC emissions attributable to mobile-source activity NAPAP The air-regulatory structure created under the National Environmental Protection Act Public Law of and the Clean Air Act CAA Amendments of had sought to substantially reduce transportation's contribution to the ozone problem through an almost exclusive programmatic focus on motor-vehicle manufacturers Chapter 4.
The core of this structure was a set of increasingly stringent per-vehicle emissions standards shown in Tables and called the Federal Motor Vehicle Control Program. Beginning in , the structure ex-. Following initiatives taken by individual states, such as Colorado, EPA promulgated a rule that set upper RVP limits for gasoline sold during the ozone season throughout the nation EPA The limits were determined, in part by meteorology, but largely by average summer temperatures.
These limits were subsequently redefined and made more stringent for and later years EPA This initial foray by the federal government into using fuel properties to aid in ozone mitigation efforts was then substantially expanded by the passage of the Clean Air Act Amendments of , which mandated the federal RFG program.
The key aspects of this program are discussed later in this chapter. Various regions of California exceed the air-quality standards for ozone several times per year, and the Los Angeles area is generally recognized as having the most severe ozone pollution problems in the nation. Perhaps, for this reason, California has often led the nation in the promulgation of new and creative approaches to ozone-pollution mitigation, and regulation of gasoline is no exception.
Requirements for fuel modifications in California have existed since when RVP limits were mandated. Through the s, requirements were also promulgated for quantities of lead, sulfur, and manganese-phosphorous in gasoline and sulfur in diesel fuels.
The California Clean Air Act of imposed additional requirements on mobile sources to 1 achieve maximum emissions reductions of VOCs and NO x by the earliest practicable date; 2 achieve feasible reductions in particulate mass PM , CO, and toxic-air contaminants; and 3 adopt the most effective control measures on all classes of motor vehicles and their fuels.
A key principle first manifested in the concept of an RFG program is the concept that a vehicle and its fuel are an integrated system for which emissions controls should be fashioned to derive the optimum benefit from each of the system's components. The purpose of AQIRP was to develop data on potential improvements in vehicular emissions and air quality that could be realized through the use of RFG, various alternative fuels, and the development of automotive technology Burns et all.
AQIRP sought to identify those fuels and formulations that could be most effective in reducing ozone precursors without compromising driveability or substantially increasing the cost per gasoline or diesel equivalent range of driving. The program was motivated in part by the perception that the crafting of gasoline should be completely rethought, such that the entire range of its potentially health-harmful constituents, including sulfur, aromatics, and reactive olefins, should be subject to limits.
The California program precedes the federal program by about 3 to 4 years. Both the federal and California programs are to be implemented in two phases.
To avoid confusion, Arabic numerals are used in this report to identify Phases 1 and 2 of the California program, and Roman numerals are used to identify Phases I and II of the federal program.
The general characteristics of the two programs are outlined. Three U. The tables are not intended to provide a comprehensive presentation of the programs' requirements. Because CO pollution is typically most severe in the winter months, the oxygenated fuels program generally seeks to regulate fuel composition during those months.
By contrast, the RFG programs tend to prescribe content and volatility of gasoline sold during the summer ozone season. In general terms, the federal concept of RFG, as of January 1, , is gasoline blended such that, on average, the exhaust and evaporative emissions of VOCs and air toxics chiefly benzene, 1,3-butadiene, polycyclic organic matter POM , formaldehyde, and acetaldehyde resulting from RFG use in motor vehicles are significantly and consistently lower than such emissions resulting from use of conventional gasolines.
In a legal context, a gasoline is reformulated if the EPA administrator has certified that it meets all specifications of the CAA. Section of the CAA codifies the redefinition of gasoline to be sold in areas failing to achieve ambient air-quality standards for air pollutants linked to emissions of CO, nonmethane hydrocarbons NMHCs , and NO x. As described in Chapter 2 , all three are precursors for tropospheric ozone formation.
CO and nitrogen dioxide NO 2 are also subject to ambient-concentration standards because of their direct impact on human health. As indicated in Table Part 1 , nine metropolitan areas are specified for application of the federal RFG program. Before passage of the CAA Amendments of that codified these requirements, EPA had already concluded that those areas would require an arsenal of new weapons to combat their ozone problems, and that changes in the composition of motor fuels would play a key role.
Subsection k 10 D officially defined those areas as the "covered areas" for use of. The periods in which oxygenates were required depended on location, but all were in the range of October 1 through February In addition, the subsection allowed for participation of any other nonattainment areas wishing to opt in to the gasoline content regulations.
Table lists these so-called RFG voluntary opt-in areas as of May 1, The intent of Congress in formulating the federal RFG program was to ensure the participation of oxygen and oxygenate constituents in the modified-gasoline composition. The addition of oxygen at a minimum of 2. For oxygen, the section requires a minimum of 2. Such gasolines were also prohibited from containing heavy metals and from excluding detergent additives.
Subsection k 7 also provides for a determination of credits for refining gasolines certified to a greater stringency i. In developing regulations to implement the requirements of the CAA Amendments of , specific per-gallon emissions-reduction targets for RFGs were set for each of two VOC-control regions: those generally in the northern tier of states, with summer baseline gasolines in the 9. Such a distinction reflects the.
The covered areas outside California that fall into the southern tier include only the Houston-Galveston-Brazoria, Texas area, and the recent opt-in areas of Dallas-Ft. Worth, Texas; and the Richmond and Tidewater metro areas of Virginia. As described below, these targets are to be computed using the so-called "Complex Model. Phase 1 requirements, effective January 1, , required: 1 an RVP limit of 7. As indicated in Table Part 1 , California Phase 2 RFG was required to limit specific fuel properties: RVP to reduce evaporative VOCs; sulfur content to avoid catalyst poisoning and thereby reduce VOCs, NO x , CO, and toxic emissions; aromatics content to reduce the atmospheric loading of mono- and polycyclic hydrocarbons linked to ozone formation; olefins to reduce VOC emissions reactivity; and benzene content to decrease emissions of this regulated toxic substance.
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