Biodiesel is a renewable, alternative diesel fuel produced from vegetable oils, animal fats, or recycled restaurant grease. This non-toxic, biodegradable liquid fuel consists of mono-alkyl esters of long chain fatty acids (also known as fatty acid methyl esters, or FAMEs) and may be used alone or blended with petroleum-based diesel fuels. The most common process for producing biodiesel involves two steps:
  • Through the transesterification reaction, triglycerides (i.e. oils or fats) are chemically reacted with an alcohol, usually methanol, in the presence of a catalyst, like sodium or potassium hydroxide, yielding fatty acid methyl esters (FAMEs) and glycerin by-product.
  • The FAMEs and glycerin by-product are then separated and purified. Biodiesel is the name given to the FAME fraction retained for use as fuel. The glycerin fraction is sold for use in soaps and other products.
The resulting biodiesel contains no sulfur or fossil fuel aromatics. Biodiesel is almost 10% oxygen, making it an oxygenated fuel, which aids combustion in fuel-rich circumstances. Biodiesel can be used pure (B100 biodiesel = 100% biodiesel) or blended (for example, B20 biodiesel = 20% biodiesel and 80% petroleum diesel).

Sigma-Aldrich offers many high-quality products to assist biodiesel producers and testing facilities with several key areas in the process:
  • Manufacturing: The efficient and complete separation of FAMEs from the glycerin by-product results in purer material and less re-processing.
  • 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, B100 biodiesel must be tested for trace levels of contaminants that may cause problems in diesel engines.

  • ASTM D6584, Standard Test Method for Determination of Total Monoglyceride, Total Diglyceride, Total Triglyceride, and Free and Total Glycerin in B-100 Biodiesel Methyl Esters by Gas Chromatography.
  • ASTM D6751, Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels.
  • DIN EN 14103, Fat and Oil Derivates - Fatty Acid Methylesters (FAME) - Determination of Ester and Linolenic Acid Methyl Ester Contents.
  • DIN EN 14105, Fat and Oil Derivatives - Fatty Acid Methyl Esters (FAME) - Determination of Free and Total Glycerol and Mono-, Di-, Tri-glyceride Content.
  • DIN EN 14110, Fat and Oil Derivatives - Fatty Acid Methyl Esters (FAME) - Determination of Methanol Content.
  • DIN EN 14214, Automotive Fuels - Fatty Acid Methyl Esters (FAME) for Diesel Engines - Requirements and Test Methods.
  • ISO 12937, Petroleum Products - Determination of Water - Coulometric Karl Fischer Titration Method.