Crude glycerine is usually used in the animal feed market or can be refined or purified for higher-value applications such as in pharmaceuticals, soaps, cosmetics, food and beverages. In fact there are probably over 1,500 different uses of glycerol, according to industry players. Glycerol is structurally analogous to sugars.
According to the US Department of Energy (DOE) in a 2004 study, glycerol is one of the top 12 building block chemicals from biomass. Glycerol is made from natural fats and oils (as we sometimes called it lipids) via the chemical process esterification/transesterification. Crude glycerin has minimum 85% glycerol, with low salts and many organics such as free fatty acids and distillates), according to ICIS.
Within biodiesel production, the purity of biodiesel (and consequently glycerin) depends on the feedstock used. Higher cost virgin vegetable oil feedstocks contain few impurities and are comparatively easy to process while lower cost and unrefined virgin vegetable oil feedstocks generally contain impurities that must be pretreated as part of the production process.
Posted by Frédéric Chivrac 
