Production of high quality biodiesel from waste feedstocks

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Waste oils obtained from frying and rendering activities are promising sources of lipids for the production of biodiesel. However, in order to upgrade these wastes to high quality fuels, significant technological challenges must be overcome. Issues of feedstock contamination and variability must be addressed in processing waste lipids to provide a consistent product that can be added to diesel fuel. There is also an urgent need for an inherently reliable processing technology that can achieve the new tighter North American biodiesel standards. Consultation with Canadian biodiesel producers has revealed that new standards on biodiesel purity are imposing greater constraints on the processing of waste feedstocks. A biodiesel membrane reactor recently developed at the University of Ottawa offers an inherently reliable processing technology to meet these challenges. The novel feature of this continuous membrane reactor is its ability to simultaneously transform lipid feedstock into biodiesel and separate the reaction products from the feedstock. Early tests point to the ability of the membrane reactor to retain soaps during the base esterification of oils containing high free fatty acids. The reactor has been tested with food-grade canola oil, but remains largely untested using waste oils such as yellow grease (used frying oils). We propose to determine the critical flux of the membranes used in the membrane reactor. Using various grades of yellow grease feedstock, we will produce biodiesel meeting the new standards. The project aims at developing technology to reduce mono and divalent salts in biodiesel produced from waste oils using diafiltration and various ion-exchange resins. The effect of membrane pore size on free fatty acids and soap retention in the membrane reactor, the coking properties and the distillation temperatures of the biodiesel produced will be determined.