However, alkaline catalysis has the disadvantage of high sensitivity to both water and free fatty acids present in the oils.
[2] The major steps required to synthesize biodiesel are as follows: Common feedstock used in biodiesel production include: Lignocellulose generates byproducts that act as enzyme inhibitors, such as acetic acid, furfural, formic acid, vanillin, and these chemical inhibitors affect cell growth.
[4] Recycled oil is processed to remove impurities from cooking, storage, and handling, such as dirt, charred food, and water.
[better source needed][5] Water is removed because its presence during base-catalyzed transesterification results in the saponification (hydrolysis) of the triglycerides, producing soap instead of biodiesel.
Base-catalyzed transesterification reacts lipids (fats and oils) with alcohol (typically methanol or ethanol) to produce biodiesel and an impure coproduct, glycerol.
Products of the reaction include not only biodiesel, but also the byproducts soap, glycerol, excess alcohol, and trace amounts of water.
An alternative, catalyst-free method for transesterification uses supercritical methanol at high temperatures and pressures in a continuous process.
[citation needed] Use of an ultrasonic reactor for biodiesel production can drastically reduce reaction time and temperatures, and energy input.
The use of lipases makes the reaction less sensitive to high free fatty-acid content, which is a problem with the standard biodiesel process.
[11] Lipids have been drawing considerable attention as a substrate for biodiesel production owing to its sustainability, non-toxicity and energy efficient properties.