Bioethanol is a renewable, alternative fuel traditionally produced by the yeast fermentation of sugar. When used as an oxygenated additive in gasoline to yield a cleaner-burning fuel, blends typically range from E10 (10% ethanol and 90% gasoline) to E25 (25% ethanol and 75% gasoline). It is also used in ′flex-fuel′ vehicles that can operate with higher ethanol percentages. In the USA, an E85 blend (85% ethanol and 15% gasoline) is used. In Brazil, where ethanol is made from sugar-cane, over half of their cars can operate on E100. Typically, commercial production of fuel ethanol involves:
  • The breakdown of a starch (from corn, sugarcane, etc.) into simple sugars.
  • The fermentation of the sugars into ethanol using yeast.
  • The recovery of the ethanol, termed bioethanol, which is retained for use as a fuel. The by-product mass is sold for use as animal feed.
Many areas of the process are important to ensure a quality end product. However, none are more critical than the ethanol-producing step of fermentation. Residual sugars left unfermented not only lower ethanol concentrations, they also damage automotive engine components. Consequently, fuel ethanol producers continually monitor their process for purity levels, as well as for the presence of several contaminants.

Sigma-Aldrich offers many high-quality products to assist bioethanol producers and testing facilities with several key areas in the process:
  • Determining Purity: Necessary to be able to gauge the overall quality of the process and final product.
  • Testing for Contamination: Before being used or blended, E100 bioethanol must be tested for trace levels of contaminants that may cause problems in automotive engines.

  • ASTM D4806, Standard Specification for Denatured Fuel Ethanol for Blending with Gasolines for Use as Automotive Spark-Ignition Engine Fuel.
  • ASTM D5501, Standard Test Method for Determination of Ethanol Content of Denatured Fuel Ethanol by Gas Chromatography.