Sources of Used Oil Samples III
Used automotive lube oil sample was tested as the feedstock for the biomass production. Since the characteristics of automotive used oils may be very similar from batch to batch (need to be verified, of course), it could make the optimal pretreatment process much simpler to decide. Another good source of used oil is the used cooking oil. According to the market research, recycled used cooking oil mostly came from the frying basins of restaurants, fast food chain stores, and some deep-fat frying snack manufacturers. Used cooking oil is always collected and recycled in order to process to make soap, paint, feed, fertilizer, or fuel. Few studies have investigated the possibility of converting used sunflower oil to diesel fuels . Used cooking oil may be another good source for this biochemical process since it may contain good nutrients for bacteria strains, though it’s presence in solid state at room temperature may make people think that used cooking oil is not easily re-used. At high fermentation temperature, however, it should not be difficult to process. Vegetable oil (corn oil, olive oil…) consists mostly of unsaturated hydrocarbons, while vegetable shortening is consisted of mostly saturated hydrocarbons through hydrogenation process. Unsaturated hydrocarbons are very active during excess heating process and easily oxidized into toxic compounds (color-causing materials). The target undesirable compounds we should be careful about are amines, hindered phenols, etc., which not only reduce the useful life of the oil but also are responsible for human health problems (for example, acne formation). 59 It is claimed that fat or oil must be discarded when its polar fraction is more than 25%. The manager of the fast food store on campus kindly explained how to decide if the oil is unfit to use ⎯ by a color comparison method.It is a common practice for individual restaurant owners to filter oil used for deep-fat frying to remove food debris, which may accelerate the decomposition of the oil. Together with the adsorption of soluble impurities, it will extend the life of the oil and provide higherquality fried food. The number and variety of products in the frying process are great, but the nutritional and toxicological consequences of their consumption remain largely unknown. If we want to utilize used cooking oil as the feedstock of the biochemical process, then these toxic materials are also suggested to be removed prior to the fermentation stage to avoid any adverse effect. Since no research has been done on this area, further study is needed.