ORNL study shows benefits of mid-level ethanol blends

By Erin Voegele | August 05, 2016

Oak Ridge National Laboratory has published a study on mid-level ethanol blends that has determined high-octane fuels (HOF), specifically ethanol blends of E25 to E40, could offer significant benefits to the U.S., including improved vehicle fuel efficiency in vehicles designed to use increased octane.

According to the report improved efficiencies of 5 to 10 percent would offset lower energy density of the mid-level ethanol blends. As a result, E25-E40 would reach economic parity with E10 blends.

The report indicates that original equipment manufacturers (OEMs) of light-duty vehicles are pursuing a broad portfolio of technologies to reduce carbon dioxide emissions and improve fuel economy. Higher efficiency spark ignition engines are central to this effort. This includes technologies reliant on higher compression ratios and fuels with improved anti-knock properties, such as gasoline with significantly increased octane. The report notes that ethanol would be an ideal octane booster for lower-octane petroleum blendstocks. The researchers also state that mid-level ethanol blends of E25 to E40 “with a research octane number (RON) of about 100, appears to enable efficiency improvements in a suitably calibrated and designed engine/vehicle system that are sufficient to offset its lower energy density…This efficiency improvement would offset the tank mileage (range) loss typically seen for ethanol blends in conventional gasoline and flexible-fuel vehicles (FFVs). The prospects for such a fuel are additionally attractive because it can be used legally in over 18 million FFVs currently on the road. Thus the legacy FFV fleet can serve as a bridge by providing a market for the new fuel immediately, so that future vehicles will have improved efficiency as the new fuel becomes widespread. In this way, HOF can simultaneously help improve fuel economy while expanding the ethanol market in the United States via a growing market for an ethanol blend higher than E10.”

Within in its findings, the report states that analysis of the HOF market and primary stakeholders reveals that the automotive OEMs, consumers, fuel retailers, and ethanol producers all stand to benefit as HOF increases its market share. Possible limiting constraints to a significant HOF market penetration include regulatory uncertainty and insufficient retailing investment. HOF could also be limited by the rate of construction of additional biorefinery capacity and poor dedicated HOF vehicle penetration. However, feedstock availability was not found to be a factor limiting the growth of HOF.

Chris Bliley, director of regulatory affairs at Growth Energy, weighed in on the results of the study. “This report reinforces what consumers know today—more ethanol means more consumer savings at the pump and less pollutants in the air we breathe,” he said. “I am pleased that this report recognizes and confirms what we’ve said for a number of years—automakers can take advantage of ethanol’s high octane properties to achieve the administration’s ambitious climate goals. As the Environmental Protection Agency, the National Highway Traffic Safety Administration, and the California Air Resources Board undertake their mid-term review, they should appropriately recognize the ability of high-octane, mid-level ethanol blends to meet the future greenhouse gas and fuel economy standards.”

“The experimental and analytical results of this study considered together show that high octane fuels (HOF), specifically mid-level ethanol blends (E25-E40), could offer significant benefits for the United States,” Bliley continued. “These benefits include an improvement in vehicle fuel efficiency in vehicles designed and dedicated to use the increased octane…Furthermore, dedicated HOF vehicles would provide lower well-to-wheel GHG emissions from a combination of improved vehicle efficiency and increased use of ethanol.”

A full copy of the study can be downloaded from the ORNL website.