Glycerin

I know that glycerin is listed as an allowed nonorganically produced agricultural ingredient for food processing, but I have also seen it in products used as crop inputs for organic agriculture—does glycerin have a nonsynthetic form?

By Sam Schaefer-Joel

Glycerin, also known as glycerol, is a small molecule with a large variety of uses. Its viscosity, polarity, solubility, and hygroscopic (water absorbing) properties give it a wide range of applications in agriculture, food processing, medicine, microbiology and industrial manufacturing.

Glycerin does not naturally occur in a free form; rather, it is chemically bound to three fatty acids as the backbone of a triglyceride molecule. Triglycerides are the primary constituents of plant and animal oils. OMRI considers glycerin derived either from animal or vegetable fats and oils to be agricultural and allowed at §205.606(i). OMRI determines the agricultural/nonagricultural status of a material using NOP Guidance 5033-2: Decision Tree for Classification of Agricultural and Nonagricultural Materials for Organic Livestock Production or Handling.

Glycerin is commonly created as a by-product of soap and biodiesel manufacture. During these processes, the bond between the fatty acids and the glycerin backbone is broken, usually by the addition of a strong alkaline base such as sodium or potassium hydroxide. When glycerin is produced through such a reaction, it is considered to be synthetic and is not allowed for use as a crop input in organic agriculture (with the exception of use as an inert ingredient in a formulated pesticide). However, there are several alternative methods to produce glycerin that have been determined to be nonsynthetic by OMRI.

Nonsynthetic glycerin may be produced through fermentation of a carbohydrate substrate by yeast. This process was developed by the German biochemist Carl Neuberg during World War I when a British naval blockade prevented the importation of vegetable oils. Glycerin (made from these oils) is essential to produce nitroglycerin which is used to make a variety of explosives and propellants. Neuberg discovered a technique to block the yeast’s metabolic process that ferments sugars from a carbohydrate substrate into ethanol. This technique consequently forces the yeast to produce glycerin by an alternative metabolic process. This method of production is probably the least common in modern times, as growing biodiesel production has increased the amount of cheap glycerin by-products in the marketplace.

Glycerin may also be produced by steam hydrolysis. During steam hydrolysis, water and oils are mixed under high temperature and pressure in an industrial pressure cooker. These conditions allow the water molecules to break the bonds between the fatty acids and the glycerin backbone. Because this process uses physical methods instead of the addition of synthetic chemicals, OMRI has determined this process to be nonsynthetic. Additionally, there is precedent for allowing steam hydrolysis in the production of common soil amendments such as feather meal and bone meal. 

This article was originally published in the Winter 2013 edition of the OMRI Materials Review newsletter. It was revised and updated in April 2025 by Colleen Al-Samarrie.