Fatty acid methyl ester

Conventional biodiesel is mostly produced via transesterification process. Fatty acids, alcohol and catalysts are needed to produce fatty acid methyl ester (FAME). Any fatty acids from vegetable oils, waste oils, or animal fats can be used. The vegetable oil is mixed with methanol and a catalyst. Often used catalysts are sodium or potassium methanolat. The mixture is stirred for several hours at temperatures between 50 and 80°C. During this process the triglyceride reacts with the methanol. Glycerin (glycerol) is replaced by methanol, which forms together with the three fatty acids, methyl ester chains and a free glycerol molecule. The resulting products (raw biodiesel and glycerol) and by-products (methanol, water, and free fatty acids) have to be separated in several processing steps, e.g. distillation. Purified methanol can be re-used in the process. The raw biodiesel has to be purified in further processing steps to reach the desired product quality of biodiesel.

Also glycerol has to be purified before it can be further used in the food, cosmetic and oleochemical industrie.

The characteristics of fatty acid esters are similar to those of fossil diesel fuels, but they require a different set of additives to prevent oxidation processes and to improve the low temperature behaviour.  For sale, biodiesel is often blended (7%) with fossil diesel (B7) or offered as pure biodiesel (B100).