For the past several years, the Department of Energy (DOE) has been quietly researching the benefits of ethanol-based High Octane Fuels (HOF), such as E25, E30 and E40. Now, some of DOE’s findings are ready for prime time.
In a recent paper, (“Summary of High-Octane, Mid-Level Ethanol Blends Study”), scientists from DOE’s Oak Ridge, Argonne and the National Renewable Energy Laboratories reviewed the exciting results of their HOF research to date. DOE’s work on HOFs has been comprehensive, and includes topics ranging from marketplace barriers to HOF adoption to fuel efficiency and GHG benefits to economic considerations. Overall, the research found that development of ethanol-based HOFs and co-optimized spark ignition engines would be beneficial to the economy and environment of the United States.
As the U.S. Environmental Protection Agency (EPA) is currently evaluating the feasibility and cost of future vehicle fuel economy and GHG emission standards, this report makes a strong case that HOFs should play a central role in fueling our future automobiles.
Key points from the DOE report are summarized below.
Knock Resistance of Ethanol-Gasoline Blends
The study confirmed that Mid-Level Ethanol Blends (MLEB) such as E25 or E30 are beneficial to high efficiency vehicles in several ways. (Vehicles with small, boosted, direct injection engines built with high compression ratios.)
First, ethanol can be used to produce high octane fuels: adding 15% more ethanol to an E10 blend with 87 octane can produce an E25 HOF that is suitable for use in a high efficiency engine.
Second, ethanol has a high heat of vaporization compared to petroleum fuels, which provides further knock resistance that is not measured in the traditional octane tests. A MLEB HOF inherently provides more knock resistance than an E0 fuel of the same octane, and automakers can calibrate their vehicles to take advantage of this additional knock resistance.
Third, and very importantly, an E25 HOF reduces greenhouse gas emissions by 4%, and an E40 HOF reduce greenhouse gases by 9% over an E10 HOF fuel.
Effect of HOF in Legacy Vehicles
Existing FFV vehicles were tested with E30 HOF, and a significant improvement in vehicle performance was noted.
Additional experiments were conducted with a non-FFV 2014 Ford Fiesta equipped with a small, turbocharged direct-injection engine. The vehicle underwent fuel economy testing with an E0 90.7 octane fuel, and an E15 splash blended with that same fuel, resulting in a 97.8 octane fuel. The fuel efficiency was higher for the E15 fuel, significantly exceeding the fuel economy expected based on the fuel energy content. In the highest speed and load test, the engine had a 4.6% improvement in thermal efficiency when using E15, resulting in a nearly equivalent volumetric fuel economy to the E0. This vehicle would see even greater fuel economy improvements with an ethanol-based HOF in the range of 100 octane! The bottom line is that ethanol-based HOFs can achieve the same or better fuel economy in optimized engines as an E0 or E10 fuel in conventional engines.
The DOE also examined market forces encouraging and opposing the introduction of ethanol-based HOFs.
Specifically, the agency found that regulatory acceptance and support of HOF is necessary to foster broad adoption. RFS2 levels should increase in a predictable fashion so that expected ethanol volumes and RIN prices are understood in the marketplace. Further, fuel economy and greenhouse gas regulations should properly incentivize the production and co-optimization of new cleaner fuels and vehicles.
The success of the HOF is also dependent on the acceptance of the HOF by key stakeholder groups. The groups identified in the study are fuel producers, distributors, retailers, automakers and consumers. The DOE studies show that HOF will be cost competitive with other fuels in the marketplace, especially as cellulosic ethanol production from corn stover reaches broad commercial scale. The study further suggested that incentive and grant programs to upgrade infrastructure will be needed, and should be provided through state and local governments.
The DOE laboratories concluded that ethanol-based HOF will be beneficial to American consumers. HOFs will allow substantial increases in vehicle fuel economy and substantial decreases in greenhouse gas emissions, while requiring only modest upgrades to existing fuel infrastructure. Multiple stakeholders stand to benefit from the development of the HOF and the high efficiency vehicles.