Project Details

The U.S. Department of Energy (DOE) Bioenergy Technologies Office sponsored a scoping study to assess the potential of high-octane fuel (HOF) to assess its potential to reduce energy consumption and greenhouse gas (GHG) emissions, and to understand barriers to its successful market introduction. The goal was to provide information about the benefits of bringing this new fuel to the market, barriers to its adoption, and strategies for market introduction.

The project, which began in late FY 2013 and culminated in early FY 2016, used the combined expertise of Argonne National Laboratory, National Renewable Energy Laboratory, and Oak Ridge National Laboratory.

Task Description

The HOF project consisted of the following integrated tasks:

• Efficiency Gains of HOF in Dedicated Vehicles: Quantify the fuel economy benefits of HOF at the vehicle level. Significant efficiency improvements are possible through a combination of improved engine thermal efficiency and improved system efficiency from downspeeding and downsizing
• Description of Properties for Engine Knock Resistance: Develop a description of fuel knocking resistance that considers octane numbers and heat of vaporization; including the development of methods of measuring the heat of vaporization of ethanol-gasoline blends.
• Effects of HOF on Legacy FFVs: Determine the effects of high-octane gasoline blends, such as blends of gasoline with 25%–40% ethanol (E25–E40) on legacy FFVs. Demonstrating a performance benefit in legacy FFVs would help in marketing ethanol blends for the legacy FFV fleet, which could bolster development of the infrastructure for fueling future vehicles specifically designed for this fuel.
• Analysis of Energy and GHG Emissions and Modeling of Refinery Impacts: Conduct petroleum refinery simulations for various ethanol blending levels and HOF market shares. Evaluate the “well-to-wheels” energy and GHG effects of HOF use, accounting for vehicle efficiency gains, refinery operation changes, and the blending effects of ethanol.
• Market Analysis: Identify and assess the economic, logistical, behavioral, and regulatory barriers to introducing HOF to the market and ways to address these barriers during a transition period. Stakeholders were engaged to help identify barriers and ways to overcome them and to estimate their potential impact on dedicated HOF vehicle sales and ethanol use.
• Infrastructure Assessment: Work with stakeholders to assess the compatibility of mid-level ethanol blends with the existing storage and fueling infrastructure.
• Evaluation of Cost Reduction Potential of HOF Blendstocks: Evaluate the potential to use natural gasoline as a low-cost blendstock for HOF.

Pertinent Findings and Outcomes

• E25 and E40 would achieve volumetric fuel economy parity with today’s E10 with a 5 and 10% improvement in vehicle efficiency, respectively (i.e., fuel economy would be the same using HOF as today’s vehicle using E10, and so every gallon of ethanol used in HOF would displace a full gallon of gasoline.)
• Fuel efficiency gains of up to 10% over E10 were demonstrated in vehicles with turbocharged, direct-injected engines. Operating engines in more efficient but more knock-prone conditions—through downspeeding, downsizing, and increasing the compression ratio—improves efficiency with HOF. The exact fuel economy benefit will vary depending on ultimate engine/vehicle design and driving conditions.
• Measurements of heat of vaporization of ethanol blended with a range of gasoline blendstocks, including natural gasoline; show that there is little difference between the hydrocarbon components and that the major factors affecting ethanol blend heat of vaporization are ethanol content and temperature. Research is ongoing under other DOE programs to understand how octane number and heat of vaporization interact for fuel knock resistance.
• Most legacy FFVs offer a performance benefit (i.e., improved acceleration) using HOF with no engine modifications required. This finding is a potential marketing pathway for introducing high octane mid-level blends, because they are legal to use in today’s FFV fleet. For “normal driving,” fuel economy using HOF was proportional to the energy density of the fuel.
• The efficiency gain of HOF overwhelmingly overtakes the potential increase in refinery GHG emissions for HOF production, resulting in net GHG reductions by HOF.
• Modeling further suggests that even under very aggressive market penetration assumptions, the availability of ethanol feedstocks does not limit the growth of the market. Fuel retailers’ willingness to invest in HOF equipment does limit market penetration in many scenarios. In scenarios where the latter is not a limiting factor, the construction rate of biorefineries (and technology advancement for second-generation ethanol) tends to be a limiting factor in early years, and HOF vehicle adoption tends to be the limiting factor in later years.
• Modeling further suggests that even under very aggressive market penetration assumptions, the availability of ethanol feedstocks does not limit the growth of the market. Fuel retailers’ willingness to invest in HOF equipment does limit market penetration in many scenarios. In scenarios where the latter is not a limiting factor, the construction rate of biorefineries (and technology advancement for second-generation ethanol) tends to be a limiting factor in early years, and HOF vehicle adoption tends to be the limiting factor in later years.
• The use of E25–E40 for producing HOF allows for greater market penetration of HOF than is available through E10 HOF.
• Producing HOF with E10, E25 or E40 in petroleum refineries causes minimal impact on overall refinery efficiency. However, if HOF market penetration is significant, petroleum refineries will find it hard to meet the high demand for HOFs without the use of higher-ethanol blends (e.g., E25 and E40).
• Based on our model analysis, optimized HOF vehicles can achieve a substantial market share (43 to 79% of vehicle stock by 2035) and can consume significant quantities of ethanol (up to 30 billion gallons per year). The extent of market success for the vehicles and fuel varies widely depending on the scenario and underlying assumptions.
• Although the retail fueling station infrastructure is not inherently compatible with mid-level ethanol blends today, materials and equipment are available that are compatible with 25–40% ethanol blends. The cost of dispensing equipment is substantially less for E25.
• Nearly all fuel terminals store ethanol and while there are no technical issues for storing more ethanol there are considerations including tank availability—nearly all are in use and a considerable amount are leased through long term contract to terminal customers. There could be space constraints for additional tanks and ethanol unloading facilities and the regulatory process for these additions are lengthy.
• An empirical model was developed to estimate fuel properties using natural gasoline as a blendstock.
• Natural gasoline is a potential low-cost hydrocarbon blendstock for FFV fuels and HOF, if blended with sufficient ethanol.