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Crude glycerol or glycerin is one of the byproducts of biodiesel production. Crude glycerin is not suitable for most commercial applications due to high impurity levels and requires further refinement prior to marketing. After refinement, the purified glycerin may be used in the same applications as conventionally produced varieties including food and pharmaceutical products, cosmetics, and chemical formulations. Refining crude glycerin is expensive, however, and the economics of the process have forced biodiesel producers to seek commercially viable uses for the crude product such as composting, combustion, animal feed, and explosives.
The use of glycerin from biodiesel can be divided into two categories: refined products which meet commercial pure glycerin standards and those based on unrefined crude glycerin. The refinement of crude glycerin removes methanol, free fatty acids, calcium, magnesium, and sulfur and ensures minimum concentrations of glycerol, the active component in glycerin, of 80%. Pure glycerin refined from crude biodiesel byproducts is essentially the same as that produced by other means and may be employed in the similar applications. Crude glycerin, on the other hand, is either used as-is or partially refined.
Refined glycerin from biodiesel is used in a number of industries including food processing, pharmaceutical manufacture, and chemical formulation. The food industry utilizes glycerin as a sweetener, solvent, and thickener. It is also used as a humectant to keep foodstuff moist and as a filler in many low fat products. Pure glycerin from biodiesel is also included in many low glycemic index (GI) foods because it has around the same calorific or food energy value as table sugar but does not raise blood sugar levels.
The pharmaceutical industry uses refined glycerin from biodiesel in a number of medical and personal care products as a lubricant, humectant, and texture improving agent. These products include cough syrups, expectorants, toothpaste, skin care products, and shaving cream. Soap, hair care products, and personal lubricants also feature glycerin as an additive. Glycerin is also commonly used as a tablet holding agent in the formulation of solid dosage medication.
The chemical industry has several applications for purified glycerin from biodiesel. These applications include fuel additives such as glycerin acetate, a component in surface coatings, and as additives in artists paints. Glycerin is also found in paper manufacturing formulations, dyes, and inks and antifreeze agents.
Crude or partially refined glycerin is used in a number of industries which do not require high levels of purity. These include explosive production, aerobic composting, and a range of animal feed products. Biodiesel derived glycerin is also added to dust suppressant products and has been utilized as a base for combustion fuel pellets.