General Topics
Bus Powered by Cooking Oil

Yale Shuttle Bus Powered by Cooking Oil

In an experiment that connects Yale’s dining halls to its shuttle service, the University is powering one of its shuttle buses with recycled cooking oil.  The cooking oil, which is used in fryolators in the University’s dining facilities, is recycled and then processed into biodiesel fuel.  The University had been testing the bus with a blend of 50% bio-diesel for the past month and during Yale’s commencement, it ran on 100% biodiesel fuel for the first time.

Associate Vice President for Administration Janet Lindner explains: “The experiment with 100% biodiesel complements Yale’s use of alternative fuels in the rest of its shuttle fleet. The University has converted all of its shuttle buses to bio-diesel, in a blend with ultra-low sulfur diesel, as part of its commitment to a greener campus and cleaner air.”  While the rest of the buses use a blend of bio-diesel, the experiment on May 22 was the first use of 100% biodiesel on campus. According to Lindner, the University “has been making use of alternative fuel vehicles, such as hybrids, within its fleet and in May we began using alternative fuel in all Yale shuttle buses. These efforts will help promote a healthier environment for the New Haven community.”

The cooking-oil project originated when Yale professor David Johnson was approached by a student who wanted to power his automobile with vegetable oil. Working together, they applied a catalyst to remove the glycerin in the cooking oil and separate out the biofuel. “By removing the glycerin from vegetable oil, we essentially reduce its flashpoint from 600 degrees to 300 degrees, which allows us to use it as heating oil,” explains Professor Johnson. “Any car, truck or bus will run on it, with minimal modifications.”

Because the oil is a natural byproduct of plants growing in the United States, there’s no negative affect on the atmosphere, said Johnson. “The plants pull carbon dioxide out of the air; burning the fuel puts it back into the air, thus the effect is neutral,” said Johnson. “Whereas with fossil fuel, which was trapped hundreds of years ago, there are no plants to pull the carbon dioxide out of the air, so burning those fuels raises CO2 levels, which in turn leads to global warming.”

The use of biodiesel made in the U.S. can also help reduce our dependence on foreign oil supplies. It’s a win-win situation, explained Johnson: farmers get money for their crops, the crops protect the environment by pulling more CO2 out of the air and eventually we may be able to grow enough crops to reduce our need for foreign oil. “If we put our heads together, we can put a dent in it,” said Johnson.

The fuel is made in laboratories on the Yale campus. Used oil is collected by Yale Recycling and delivered to Kline Geology Laboratory, where Professor Johnson works with students in his class to turn the waste oil into biodiesel.

Donald Relihan, director of Support Services at Yale, said, “The ultra-low sulfur diesel (ULSD) combined with a biodiesel runs much cleaner than conventional diesel fuel. The sulfur content of ULSD is reduced from approximately 500 ppm to 15 ppm and can reduce particulate-matter air pollution (PM) by up to 14 percent. When combined with a 20 percent biodiesel (B20), PM is further reduced 10–15 percent.”

Relihan added, “B20 is currently the most common form of biodiesel, derived from soybean oil, and requires no vehicle, equipment or infrastructure modifications to use. In preparation for the switch, the Yale buses were recently retrofitted with oxygenating catalytic converters and specialized filters that capture crankcase emissions.”

“The conversion has been painless and transparent,” reports Ed Bebyn, manager of Parking & Transit. “We're happy to be out in the forefront with environmentally friendly fuels and vehicles.”

All of these changes are part of the University’s effort to support a greener, more sustainable community. Use of ULSD B20 will help reduce the negative impact of diesel air emissions on campus. In addition, B20, when combined with ULSD, helps engines run more smoothly and last longer.