Gevo’s renewable isobutanol enables the blending of high performance finished fuels which benefit end consumers, as well as participants across the fuel blending value chain. Isobutanol possesses a range of properties which makes it an ideal blendstock for gasoline. Some of these properties include:
Gevo’s isobutanol meets ASTM 7862 specification that covers isobutanol blends with gasoline.
High Energy Content
Isobutanol has approximately 30 percent more energy content than ethanol. Higher energy content typically translates into greater fuel economy (more mileage per gallon). In addition, as isobutanol has more energy than ethanol, isobutanol generates 1.3x more renewable identification numbers (RINs) on a volumetric basis, as compared to ethanol (per the 2007 Energy Independence and Security Act).
Octane is the measure of the ignition quality of a gasoline. The higher the octane number, the more compression the fuel can withstand before igniting. High performance gasoline engines require higher compression ratios, and thus require fuels with high octane ratings to prevent engine pinging and knocking. Isobutanol has an octane level of 102, which enables blenders to produce finished fuels with very high octane ratings.
Low Water Solubility
Because gasoline may come in contact with water, it is important that any blendstocks remain in the hydrocarbon phase and not migrate into the water. Ethanol, a highly polar material, can separate from the gasoline phase into the water phase, degrading the gasoline’s octane, especially in a moist or humid environment. Isobutanol is less polar than ethanol, and tends to act like a hydrocarbon with very limited amounts moving from the gasoline phase to the water phase. As a result, there is no dilution of the gasoline’s octane value, and operational issues related to water content are reduced or eliminated. This also enables greater compatibility with gasoline engines of all types, as well as existing refining/blending infrastructure.
Volatility is the property of a liquid fuel that defines its evaporative characteristics. The Environmental Protection Agency has established rules to reduce gasoline emissions of volatile organic compounds that are a major contributor to ground-level ozone. A key tool used by state regulatory agencies for reducing ozone precursors in the air is through reduced volatility of gasoline as measured by Reid Vapor Pressure (or RVP). Isobutanol’s RVP is very low, making it a highly valuable additive to finished gasoline. Ethanol’s RVP blend value is high, requiring the refining/blending industry to use more valuable components of oil to accommodate this high-RVP material.