The Environmental and Energy Study Institute (EESI) and the Governors' Biofuels Coalition held a briefing examining the current state and potential future of the transportation fuel supply. While combustion engines are more efficient and cleaner than ever, the transportation sector is still responsible for 27 percent of greenhouse gas (GHG) emissions as well as half of all toxic emissions in the United States. Researchers from Argonne National Laboratory (ANL), the National Renewable Energy Lab (NREL), and Oak Ridge National Lab (ORNL) are conducting coordinated studies to address the opportunities and challenges to deploying a high octane mid-level ethanol blend to the passenger vehicle fleet. They found such fuels, which blend between 25 to 40 percent ethanol and 60 to 75 percent conventional gasoline (instead of the current 10 to 90 percent ratio), could lead to greater fuel efficiencies and lower overall GHG emissions.

The Energy Information Administration predicts the internal combustion engine will be the dominant engine for the next several decades, making both fuel and engine efficiency a critical piece in reducing the GHG intensity of the transportation sector. Research is finding that higher octane fuels can help enable the greater engine efficiencies necessary to lower GHG emissions and improve fuel economy.

Today, there are two primary sources of octane: gasoline aromatics, a petroleum refinery product, and ethanol. Ethanol is a renewable fuel sourced from corn as well as other agricultural feedstocks and organic wastes. In 2014, the United States produced 14.4 billion gallons of ethanol, making up approximately 10 percent of retail gasoline by volume. Research from the National Labs finds a mid-level ethanol blend not only increases the octane rating of fuel, it may also enable fuel efficiency improvement of 5  to 10 percent, lower the cost of gasoline, and reduce life-cycle GHG emissions.

While mid-level ethanol blends do require some changes to the current gasoline infrastructure, many find the challenges have been overstated. These fuels are immediately compatible with the 17 million flex-fuel vehicles on the road today, and many gas station tanks and infrastructure are already compatible with a mid-level ethanol blend. Going forward, high octane, mid-level ethanol blends will allow for even greater engine efficiencies and advanced engine designs.

Automakers are currently working to economically meet Corporate Average Fleet Emissions (CAFE) standards that save fuel and reduce emissions. Mid-level ethanol blends, by providing a better, higher octane fuel formulation for today's and tomorrow’s gasoline vehicles, may help meet multiple policy objectives beyond 2025.



  • Representative Tammy Duckworth (D-IL), emphasized the importance of developing and using biofuels by saying that “as a veteran and a member of the House Armed Services Committee, I see renewable homegrown fuel as not only critical for our environment and economy … but also as a national security imperative.”
  • During her service in Iraq, Rep. Duckworth saw firsthand the “painful price our country pays because of our dependence on foreign oil.” Military fuel convoys are particularly vulnerable to enemy attacks, resulting in a significant share of U.S. casualties [one out of eight during the war in Iraq, according to the Army]. She suggested biofuels could be produced on military bases, using food and organic wastes, in order to lessen the risk to troops.
  • Rep. Duckworth also stressed the economic benefits of biofuels, stating that the production of biofuels in the United States leads to less foreign oil imports, greater investments in innovation, and the support of 852,000 jobs at home.
  • Dr. Robert McCormick, Principal Engineer, Fuels Performance Group, National Renewable Energy Lab (NREL), explained why octane is an important component of fuel. Engine knock is more likely to occur when lower octane number fuels are used. Knock occurs when unburned fuel and air in the engine meet prematurely, resulting in reduced efficiency and potential damage to the engine. Today, drivers rarely experience knock because of the ability of modern cars to control engine operating conditions. But these knock-preventing controls reduce fuel economy. Using higher octane fuels would make higher efficiencies possible.
  • To maximize engine efficiency and reduce greenhouse gas (GHG) emissions, several engineering strategies are available: increasing compression ratios, downsizing or downspeeding, turbocharging, and direct injection. Higher octane fuels make implementing most of these strategies much easier.
  • Ethanol, a biofuel, is already being used to boost the octane value of gasoline. Ethanol currently constitutes about 10 percent of U.S. fuel, and higher ethanol blends, such as 25-40 percent ethanol, would result in higher octane fuels.
  • Challenges to the introduction of higher amounts of biofuels into the transportation fuel supply include Clean Air Act requirements, infrastructure, storage and engine compatibility; fuel quality standards compliance; and market development and investment coordination. Additionally, it is a "chicken or egg" scenario in that fuels must already be available in the marketplace in order to produce/market compatible engines and vice versa.
  • The majority of existing fuel storage tanks are compatible with any ethanol blend, though a portion of tanks owned by small business fuel retailers will require inspection to determine their compatibility and may require fuel dispenser retrofits for high octane fuels.
  • Brian West, Deputy Director, Fuels, Engines, and Emissions Research Center, Oak Ridge National Lab (ORNL), found that using E30 fuel [30 percent ethanol, 70 percent gasoline] doubles the available torque compared to regular, 100 percent gasoline. Going forward, engine and fuel co-optimization can enable downspeeding and downsizing of the engine, which leads to better fuel economy and maximized efficiency.
  • The energy density of ethanol is two-thirds that of gasoline, but with blends of E25 to E40, the efficiency gains provided by the octane boost can offset the energy density losses and lead to the equivalent fuel economy of gasoline with fewer GHG emissions. Every gallon of ethanol used in this way can displace a full gallon of gas.
  • Flex Fuel vehicles (FFVs) are designed to use any blend of gasoline, from E0 to E85. There are over 17 million FFVs on the road today in the United States; however, these vehicles consume on average only about 13 gallons of E85 a year. And, since FFVs are not optimized for high ethanol blends, their fuel economy is lower for E85 fuel. Nevertheless, because of lower costs for E85, running costs are often less and FFVs running on an E30 blend experienced significant acceleration improvement.
  • In a conventional engine, an E15 blend (compared to E0), did not see a loss in fuel economy.
  • Caley Johnson, Transportation Market Analyst, National Renewable Energy Lab (NREL), explained that NREL completed a High Octane Fuel (HOF) Market Assessment to assess the feasibility, economics, and logistics of adopting HOF by drivers, vehicle makers, fuel retailers, and fuel producers.
  • The primary benefit to drivers is a potential fuel savings of 8 cents per gallon for E25 fuel and 16 cents for E40 fuel. These fuels are also historically more resistant to price volatility than today’s standard E10. Other benefits include national energy security, reduced GHG emissions, and better torque performance, from which vehicle manufacturers also benefit.
  • The preliminary results for the most aggressive biofuel introduction rates show a potential consumption of up to 30 billion gallons of ethanol in 2035 in the form of 75 billion gallons of E40, which could represent 60 percent of the fuel sold in 2035.
  • Several market factors limit commercialization of these fuels, including the need for fuel retailers to invest in compatible equipment, the construction rate of new biofuels refineries, and new vehicle adoption. Feedstock availability and fuel cost are not limiting factors in any of the scenarios considered by the analysis.
  • Dr. Michael Wang, Senior Scientist, Energy Systems, Argonne National Laboratory, gave an overview of his “Well-to-Wheels (WTW) Analysis of High Octane Fuels,” which accounts for the GHG emissions throughout the lifecycle production and distribution of fuel, as well as the fuel’s impact over the vehicle's operational lifetime. The study assumes a five percent efficiency gain for vehicles using high octane fuels.
  • The analysis demonstrates that the difference in petroleum refinery efficiency is very small when comparing the production of E10, E25, and E40 fuel. Similarly, Dr. Wang reports a small change in domestic and gasoline export refining efficiencies, though there is up to a four percent decline in export gasoline refining efficiency when producing high ethanol fuels.
  • Additionally, the emissions assessment shows small reductions in GHG emissions from refineries producing E10, E25, and E40 compared to the conventional fuel base case. There are incremental reductions in GHG emissions from E10 to E25 and from E25 to E40, illustrating the lower carbon characteristics of each successive increase in ethanol. When combined with the predicted efficiency gain for HOF vehicles, the reductions in well-to-wheel GHG emissions for E10, E25, and E40 are even more significant.
  • All in all, the well-to-wheels analysis indicates high octane corn ethanol blends emit 9 to 18 percent fewer greenhouse gas emissions than conventional gasoline, and high octane cellulosic ethanol blends cut emissions by 17 to 31 percent.