Ethanol

Since the 1930s, ethanol has served as a gasoline volume extender and is today in use worldwide as both a primary automobile fuel and as a gasoline blendstock. As a component of the U.S. gasoline pool, ethanol competes with many other hydrocarbon based blendstocks and has historically been utilized primarily in the Corn Belt States of the Upper Midwest. However, due to recent changes in gasoline blending specifications and environmental concerns, gasoline blenders are now using ethanol in the production of finished gasoline nationwide.

Ethanol is beneficial to gasoline blenders in a number of different ways. This renewable gasoline blendstock can be used to extend finished gasoline volume, efficiently enhance finished fuel octane, improve gasoline combustion efficiency, and as a primary component of certain specialty fuel blends.

As a gasoline volume extender, ethanol simply provides additional non-hydrocarbon blendstock to increase the volume of finished gasoline production from the refining process. The addition of ethanol effectively increases the total volume of finished gasoline production from every barrel of oil refined. Increased U.S. gasoline demand in recent years has closed the gap between the available supply of gasoline from the nation's refineries and consumer demand. The tightening gasoline supply/demand balance coupled with the overall increase in hydrocarbon commodity prices has provided additional economic incentive for industry to extend finished gasoline volumes. This incentive has been amplified recently by the removal, in some areas mandatory in other areas voluntary, of methyl-tertiary-butyl ether (MTBE) from the U.S. gasoline pool.

Ethanol's physical characteristics also contribute significantly to finished gasoline octane. The total octane content of gasoline is a measure of the gasoline's combustion characteristics and is often associated with the "value" of the fuel blend. Premium grades of gasoline contain more octane than do regular gasoline grades. As an octane booster, ethanol competes with other refinery-produced, relatively high octane components such as alkylate, iso-octane, and reformate.

Ethanol is also classified as an "oxygenate" and enhances the clean-burning characteristics of finished gasoline. When blended into gasoline, oxygenates increase combustion efficiency, thereby lowering tailpipe emissions of smog-forming pollutants such as carbon monoxide (CO) and various nitrous oxides. Ethanol contains 34.7 weight percent oxygenate and, therefore, can significantly impact the combustion characteristics of finished gasoline, even when added in relatively small amounts.