Biodiesel is produced through a process that combines organically-derived oils with alcohol (ethanol or methanol) in the presence of a catalyst to form ethyl or methyl ester. This process is a reaction of the oil with an alcohol to remove the glycerin, which is a by-product of biodiesel production.
The process uses heat and needs the use of a strong base catalyst, e.g. sodium hydroxide or potassium hydroxide. It also requires adding an alcohol, such as methanol. Both are highly toxic products that require careful handling. Washing the diesel is an essential part of the production process. Using dry washing with ion exchange resin requires no water, avoiding wastewater production.
The process leaves behind three products -- methyl esters (the chemical name for biodiesel), glycerin, and meal (canola, meal, soy meal etc). Glycerin can be used as a base product for soap; meal is used as a livestock feed. As the market for biodiesel expands, it will become necessary to develop new markets for the large amounts of glycerin and meal coproduced.