Procedure for Making Biodiesel Fuel

Obtaining Ingredients

Biodiesel fuel is diesel fuel made from sources other than petroleum. Most biodiesel is made from corn, soybean and animal fat oil. Commercially, farmers grow crops and extract the oils to produce biodiesel. Individuals who make their own fuel commonly purchase vegetable oil or obtain waste vegetable oil (WVO) from others who discard it, such as restaurants. The oil is mixed with alcohol and lye, which helps convert the mixture into burnable fuel.

Mixing

The mixing process for making biodiesel fuel involves preparing the vegetable oil in its own HDPE container, or tank. The alcohol, commonly methanol, is also carefully measured according to the amount of desired fuel, usually 200 mL per liter of oil. Lye, a mixture of sodium and potassium hydroxide, is added (about 3.5 g per liter) to convert the oil and alcohol mixture into a single, burnable liquid. For biodiesel sold to the public, the mixing takes place in tanker trucks or at pumps before the fuel is loaded for transport. Mixing oil, alcohol and lye at home is done by pouring each ingredient into a single high-density polyethylene (HDPE) container where it's stirred and allowed to settle.

Settling and Cleaning

After vegetable oil, alcohol and lye have been combined, the mixture must settle for 24 hours or longer. When settling, the fuel goes through a series of reactions, where the methanol and oil separate from the lye (see image). This indicates that the fuel is ready to be "cleaned" or "washed." Cleaning is done by diluting with water and stirring until the mixture is clear. When clear, the fuel is ready for use in diesel engines.