Ethanol fuel, also known as ethyl alcohol or grain alcohol, is a renewable fuel primarily made from various plant materials collectively known as "biomass". The most common source of ethanol fuel is corn, making it a domestically produced alternative fuel in the United States. Here is a step-by-step process of how ethanol fuel is made:
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Biomass Feedstock: Ethanol production begins with the growth, collection, and transportation of biomass feedstocks, such as corn, sorghum, barley, sugar cane, or sugar beets.
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Milling or Crushing: In the case of corn, the biomass is either dry-milled or wet-milled. Dry-milling involves grinding the corn into flour, while wet-milling primarily produces corn sweeteners, along with ethanol and other co-products.
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Fermentation: The milled or crushed biomass is then mixed with water and enzymes to convert the starches or sugars into a fermentable form. Yeast is added to the mixture, which ferments the sugars and converts them into ethanol and carbon dioxide.
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Distillation: After fermentation, the mixture is distilled to separate the ethanol from the water and other impurities. This process typically involves multiple distillation steps to achieve the desired ethanol concentration.
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Dehydration: The ethanol produced through distillation is not suitable for use as a fuel because it contains a significant amount of water. Dehydration processes, such as molecular sieves or azeotropic distillation, are used to remove the remaining water and produce anhydrous ethanol.
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Denaturing: To prevent the use of ethanol fuel for drinking purposes, denaturants are added to make it undrinkable. Common denaturants include gasoline, natural gas, or other chemicals.
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Blending: Ethanol fuel is typically blended with gasoline to produce a more environmentally friendly fuel. The most common blend in the United States is E10, which contains 10% ethanol and 90% gasoline. Other blends, such as E15 (approved for use in model year 2001 and newer light-duty vehicles) and E85 (flex fuel, can be used in flexible fuel vehicles), are also available.
