HBS - Waste Vegetable Oil

Restaurants use many different oils for frying foods. These oils are subjected to very high temperatures as well as fats and water from various foods. The process of frying food changes the physical and chemical make-up of the oil increasing the acidity and water content. This effects the (Transesterification Process) making of biodiesel by requiring more catalyst and alcohol which in turn increases production costs. Other problems may arise from oils high in water or FFAs, such as poor fuel from incomplete reaction and the formation of emulsions from a water washing process. WVO with the least amount of water under 1% and low FFAs under 5% are desirable.

Places to look would be restaurants that fry low fat foods, vegetables, fish, chicken, and potato chips. Example: Oriental restaurants and shrimp boats etc. The types of WVO to look for are Canola, Soy, Sunflower, Peanut, and Corn Oil in this order from thin and thick. This becomes a concern in cold climates as biodiesel made from heavier oil has higher viscosity. Thinner oils will have better cold flow properties in colder environments. Biodiesel made from WVO will usually have a higher viscosity than biodiesel made from virgin oil due to the physical and chemical changes made to WVO in the frying process.

Non-hydrogenated or partially hydrogenated oils will be the most common type of oils used in restaurants. Some will use completely hydrogenated oil that is solid at room temperature and should be avoided. Non-hydrogenated oil will have better cold flow properties, but will not store as well without adding stabilizers. Partially hydrogenated oil has a higher cloud point but will not oxidize as fast. The difference between non-hydrogenated and partially hydrogenated oil is small and both are treated the same when making biodiesel.