The term “glycerol” is only applicable to the pure chemical compound 1,2,3 propanotrial, while the term “glycerin” normally applies to purified commercial products with contents of higher than 95% glycerol. They differ slightly in glycerol content and other characteristics such as smell, color, and traces of impurities [41]. Many grades of glycerin are commercially available. They are obtained after removing salts, methanol, and free fatty acids. Methanol is generally recovered by heating and reused in the biodiesel production process. In most commercial applications the quality of glycerin must be improved until it has an acceptable purity that is completely different from those obtained in biodiesel facilities