Since that time, there has been strong demand for ethanol as an oxygenate blended with gasoline. In the United States each year, more than 1.5 billion gallons are added to gasoline to increase octane and improve the emissions quality of gasoline. Fuel ethanol blends are successfully used in all types of vehicles and engines that require gasoline. Approval of ethanol blends is found in the owners' manuals under references to refueling or gasoline. The feedstock passes through hammer mills, which grind it into a fine meal.
Heat is appied to enable liquefaction.
The high temperatures reduce bacteria levels in the mash. Using a continuous process, the fermenting mash is allowed to flow, or cascade, through several fermenters until the mash is fully fermented and then leaves the final tank. In a batch fermentation process, the mash stays in one fermenter for about 48 hours before the distillation process is started. The mash is pumped to the continuous flow, multicolumn distillation system where the alcohol is removed from the solids and the water. The alcohol from the top of the column passes through a dehydration system where the remaining water is removed.