Blends of petroleum-based gasoline with 10% ethanol, commonly referred to as E10, account for more than 95% of the fuel consumed in motor vehicles with gasoline engines. Ethanol-blended fuels are one pathway to compliance with elements of the federal renewable fuel standard (RFS). The total volume of ethanol blended into motor fuels used in the United States has continued to increase since 2010, albeit at a declining rate of growth. Meanwhile, the use of ethanol-free gasoline (E0) by fuel consumers has declined.
EIA tracks fuel components through data it collects from refiners, importers, large blending terminals, and ethanol producers. U.S. refiners produce large volumes of blendstocks for oxygenate blending (BOB) that are referred to as RBOB or CBOB depending on whether they are formulated to be blended with ethanol to make reformulated or conventional gasoline, respectively. Another distinct gasoline blendstock known as CARBOB is used to produce California reformulated gasoline; EIA reports aggregate CARBOB with all other RBOBs.
With nearly all U.S. gasoline now being sold as E10, the only way to increase ethanol use in the motor vehicle fleet is to adopt fuel blends containing a higher volume of ethanol, such as E15 and E85. However, not all gasoline-powered vehicles can use these fuels. The U.S. Environmental Protection Agency (EPA) has issued a partial waiver allowing the use of E15 in model year 2001 and newer vehicles. Fuels marketed as E85, which contain between 51% and 83% ethanol by volume, can only be used in flex fuel vehicles. Recent EIA congressional testimony on the RFS program estimates that flex fuel vehicles make up about 7% (16.3 million) of the current on-road fleet of light-duty vehicles in the United States.
Notwithstanding the partial waiver and the significant number of flex-fuel vehicles now in use, sales of E15 and E85 remain very limited because of a variety of economic, environmental, and distribution system challenges. EIA data cannot directly measure E15 and E85 use, in part because these fuels can be blended at the point of sale. However, in the final rule for the RFS program for calendar years 2014, 2015, and 2016 that was issued in November 2015, EPA estimated use of 320 million gallons of E15 and 200 million gallons of E85 in 2016. Combined, these values would represent only 0.4% of the total 142 billion gallons of fuel use by vehicles and other equipment with gasoline-burning engines expected during 2016, according to EIA's latest Short-Term Energy Outlook.
There are also volumes of gasoline containing no ethanol, often referred to as E0, in the market. EIA surveys show U.S. E0 refinery and blender production of 894,000 barrels per day (b/d) and 71,000 b/d of E0 imports in 2015. U.S. Census Bureau data show exports of 476,000 b/d of finished motor gasoline in 2015. Census data do not specify the ethanol content of exported gasoline, but EIA assumes the finished gasoline exports are E0. EIA data also indicate that an average of 6,000 b/d of E0 were withdrawn from stocks held at refineries and terminals or were in pipelines during 2015.
Domestic disposition of E0, calculated as domestic production plus inventory withdrawals plus net trade (imports minus exports), was 494,000 b/d (7.6 billion gallons) in 2015. However, actual use of E0 in vehicles, boats, and other equipment with gasoline-burning engines was likely below that level because some volumes of E0 that enter the domestic market may have been blended with ethanol at smaller terminals that are out of scope for EIA reporting or blended at the point of retail sale.
EIA data on ethanol supply and disposition can be used in conjunction with the E0 domestic disposition data to develop an estimate of E0 use in vehicles and other equipment with gasoline-burning engines. EIA develops fuel ethanol balances that account for production, imports, exports, stock change, and blending in the United States. As noted above, nearly all fuel ethanol is blended with a BOB to produce E10. But not all ethanol use is captured in EIA's blending data. In 2015, ethanol supply within the United States exceeded identified uses by 17,000 b/d (254 million gallons).
EIA believes that the excess of ethanol supply over identified disposition most likely reflects a combination of errors in the data and ethanol blended into gasoline at facilities that are not covered by EIA's surveys. Given that EIA survey data do not show significant BOB volumes that are not already being blended with ethanol, the bulk of this blending activity likely involves blending of ethanol with E10 to produce fuels with higher ethanol content or blending with E0. If all of the ethanol supply in excess of identified disposition were being blended with E0 to produce E10, this activity would absorb 152,000 b/d of E0. Subtracting this amount of E0 from the calculated value for domestic disposition of 494,000 b/d derived from production, inventory, and trade data would imply a remaining supply of 343,000 b/d (5.3 billion gallons) of unblended E0 to final consumers in the United States in 2015.