Glycerin Refinery Background

Glycerin (also called glycerol and glycerine) is a colorless, odorless, viscous, water-soluble liquid with slightly sweet taste. It is a three carbon alcohol which serves as the backbone of the triglyceride molecule. Glycerin is non-toxic and can be used topically in cosmetics or consumed in food products and pharmaceuticals. Glycerin is made synthetically using petroleum as a feedstock. It is derived naturally using two methods:

• Soap and fatty acid production (hydrolysis)
• Biodiesel production (transesterification)

Transesterification of fats and oils processing can yield crude glycerin as a byproduct at a rate of 10% per unit of biodiesel (methyl ester). Methanol, which is mixed with fats or oils in the transesterification process, is present in the glycerin residue. When excess methanol is removed from the glycerin, the substance is called “crude glycerin”. The content of crude glycerin varies widely, but it is generally 85% glycerin (range: 40%-90%), 10% water (range 8% to 50%), 4% salt (range 0% to 10%), less than 0.5% methanol, and around 0.5% free fatty acids. There are three basic grades of refined glycerin, differentiated by purity and potential end-uses. Glycerin is generally sold as 99.5% pure and 99.7% pure. The three grades of refined glycerin are:

• Technical grade – used as a building block in chemicals, not used for food or drug formulation
• United States Pharmacopeia (USP) – glycerin from animal fat or plant oil sources, suitable for food products, pharmaceuticals
• Kosher – glycerin from plant oil sources, suitable for use in kosher foods

The properties of glycerin create a versatile product that can be put towards many end-uses. In fact, there are over 1,500 end-uses for the chemical. In most products, however, it is only used in very small portions. There are only a few end-uses which require a significant amount of glycerin in their formulation.