When Congress passed the Energy Independence and Security Act (EISA) and President George W. Bush signed the bill into law on December 19, 2007 (P.L. 110-140), many of its key provisions were crafted based on two very important assumptions that have not panned out:
• U.S. demand for fuel for automobiles and light trucks would continue to expand the way it had for many decades in the United States.
• New technologies would soon emerge that would allow biofuels to be produced from feedstocks other than corn starch and soybean oil, such as crop residue, on a cost-competitive basis, (referred to as ‘advanced and cellulosic biofuels’ in the legislation)
Data maintained by the Energy Information Agency (EIA) of the U.S. Department of Energy indicate that daily U.S. use of motor vehicle fuel rose steadily over time, increasing from 1.7 million barrels per day right after the end of World War II to 9.3 million barrels per day as of December 2007, the month the legislation was signed. Since that time, daily use has stagnated for the most part, although it fell precipitously, from 9.8 million per day in August 2019 to 7.2 million per day in May 2020 (a 26 percent decline) as COVID-related travel restrictions took hold. Consumption has climbed back somewhat in recent years, recorded at 8.9 million barrels per day as of June 2026.
On the advanced biofuels front, while U.S. biofuels manufacturers have reached and surpassed the annual 16-billion gallon requirement set in EISA by 2022, the vast majority of the fuel that is being deemed as qualifying for that mandate is biomass-based diesel, made from vegetable oil, animal fats, and recycled grease from restaurants and meatpacking. Producing ethanol from cellulosic materials, a technology which seemed so promising two decades ago, has never really materialized for the motor vehicle market. There is still some work underway to make this fuel available, but those efforts are focused on the market for sustainable aviation fuel (SAF) rather than fuel for motor vehicles.
The lack of growth in overall motor vehicle fuel usage over the last few decades has meant that U.S. ethanol demand has largely been constrained by what is known as the ethanol blend wall. In 1978, the Environmental Protection Agency (EPA), granted a permanent waiver of Clean Air Act provisions on automobile emissions to allow gasoline blenders to include up to 10 percent of ethanol in the fuel blend marketed for cars and light trucks in the United States.
For many years, the only vehicles using higher blends of ethanol than 10 percent (up to 85 percent) for their fuel were cars and trucks specifically designed for such use, known as flexible fuel vehicles, or FFV’s. It is estimated that as of 2022, there were nearly 21 million FFV’s in the United States, accounting for about seven percent of all cars and light duty trucks available to be driven by American consumers. However, not all FFV’s regularly use higher ethanol blends, either because their owners are unaware that their vehicle’s engines would accommodate such fuel, or because E-85 is not widely available in the region that they are living and driving in.
Within about a decade or so of the passage of EISA, U.S. supporters of ethanol began to strongly advocate to Congress and/or the EPA to raise the cap on ethanol content in gasoline from 10 percent to 15 percent. The primary opposition to that effort came from the U.S. petroleum industry and the U.S. automobile sector, the latter initially claiming that use of E-15 in standard (non-FFV) cars would damage the engines over the long-term.
After extensive studies, the EPA promulgated a rule in 2019 which allowed for year-round use of E-15, but that rule was overturned in 2021 by a federal appeals court. The U.S. Supreme Court declined to consider an appeal of this ruling in 2022, leaving the decision in place. Eight Midwest states were subsequently given permission by EPA to allow for year-round availability of E-15 on a regional basis starting in 2025. In March 2026, the EPA issued a nationwide waiver for use of E-15 during the summer months of that year.
Supporters of the ethanol industry have pushed Congress to address this matter on a nationwide basis over the last few years. In May 2026, the U.S. House of Representatives passed a piece of legislation, the Nationwide Consumer Fuel and Retailer Choice Act, which would have amended the Clean Air Act to allow year-round use of E-15 across the country, although it also included other provisions meant to address concerns raised by opponents of the ethanol industry, such as permanently exempting smaller refiners from having to meet their obligations under the Renewable Fuel Standard. In early August, the Senate Agriculture Committee approved a manager’s amendment to Chairman John Boozman’s (R, AR) draft farm bill that included year-round E-15 language, but the Committee failed to report out a farm bill that day due to disputes over unrelated nutrition program provisions.
The renewable fuel sector is also pursuing gains in use of their product in other transportation sectors in the U.S. economy, such as aviation and farm equipment, but the effort to capture year-round access to the car and light truck fuel market for E-15 remains a top priority.
