Faculty and students associated with the multidisciplinary Biofuel Consortium at the University of Connecticut staged a technological first for academic biodiesel production: the continuous 16-hour operation of a pilot-scale reactor converting waste cooking oil to pure biodiesel. Following several short-run trials of the reactor, aimed at determining the conversion efficiency of the device (it was found to be functioning at a 99 percent conversion rate) the reactor began an uninterrupted overnight demonstration run. At the end of the trial, the team had produced 230 gallons of biodiesel that will be used in the University’s fleet vehicles.
Richard Parnas and Benjamin Wilhite, both faculty members in the Chemical Engineering Program, headed up the demonstration project. Dr. Parnas is director of the Chemical Engineering Program and the Storrs-based Biofuel Consortium. Dr. Wilhite just completed his second year at UConn and is a DuPont Young Professor. The prototype production system was constructed by undergraduate Matt Boucher, who will begin his graduate studies in chemical engineering in September. In addition to Mr. Boucher, Drs. Parnas and Wilhite, the demonstration team included chemical engineering students Katie Bower, Steven Unker, Cliff Weed, Si-Yu Li and visiting India Institute of Technology – Delhi student Rajdeep Das.
According to Dr. Wilhite, what differentiates the UConn demonstration from other university biodiesel projects is the reactor’s ability to operate continuously. “Other university biodiesel projects rely upon batch production, which limits the volume that can be effectively and economically produced,” said Dr. Wilhite. The reactor’s unique design features make it attractive to industry, said Dr. Parnas, who added that there is significant industrial interest in the new reactor technology. Several companies have approached UConn to request licensing rights to the reactor, for which Dr. Parnas filed a patent application in January 2007.
The Biofuel Consortium uses waste cooking oil as a feedstock in the reactor. By using waste vegetable oil, the team avoids the food-versus-energy debate currently surrounding corn based ethanol. However, spent cooking oil contains a variety of contaminants that must be removed before the oil can be used in the reactor. Gus Kellogg of Greenleaf Biofuels graciously donated 500 gallons of yellow grease, a commercial waste vegetable oil, for the demonstration. In the week preceding the continuous run, Mr. Boucher pretreated the waste cooking oil to neutralize and remove free fatty acids and contaminants that resulted from the oil’s earlier use in food production.
The UConn reactor incorporates reaction technology along with gravimetric separation to produce two liters per minute of usable biodiesel and a small amount – averaging 10 percent – of byproduct. The reactor is continuously fed a 4:1 (volumetric) mixture of waste vegetable oil and methanol with an overall flow rate of approximately two liters per minute. The reactor design is also easily scalable to much larger production rates.
A byproduct of the process is glycerol, which naturally separates from the biodiesel and is easily siphoned off. According to Dr. Wilhite, glycerol is used extensively in cosmetics and other personal care products, pharmaceuticals and commercial foods. Because the market is generally glutted, the team is investigating possible applications of glycerol as a feedstock for fuel cells or in polymers. Unreacted methanol, one of the two most important reactants, is dissolved mostly in the glycerol stream and is extremely costly to waste. To reduce the methanol loss, during the 16-hour run, Si-Yu Li used the glycerol in a 20 liter batch distillation unit to recover over 40% of the methanol removed in the glycerol stream.
Looking back on his more than 20-hour sojourn with the biofuel reactor, Mr. Boucher commented that “I learned that our reactor technology works extremely well, even when the equipment budget was quite low, and that despite several early equipment failures, hard work brings good things. We aren’t only making biodiesel in that lab, we are making a difference.”
The Biofuel Consortium emerged from a 2004 demonstration project in which a team transformed waste cooking oil into biodiesel for use in one of the University’s shuttle buses. By fall ’06, the Biofuel Consortium team was producing and supplying the University with approximately 50 gallons of biodiesel weekly, using waste oils collected only from the on-campus restaurant Chuck & Augie’s, and from the food court, both located in the Student Union.
In commercial applications, biodiesel is typically mixed with conventional diesel fuel, often at a ratio of 8:2 for the so-called “B20” fuel. When used in vehicles, biodiesel produces no sulfur dioxide, and significantly reduced hydrocarbons and particulate matter compared with conventional petroleum-based fuels.