Medical student supersizes fuel savingsFourth-year medical student Randy Holton really isn’t interested in good cholesterol, bad cholesterol, saturated fat or trans fat. But he does prefer used fat, the kind he drains from restaurant friers.He even arranged for a couple of restaurant managers to leave five-gallon jugs of used frier grease at their back doors for him to pick up on his way home. It’s a good arrangement—they need to get rid of it, and he needs to use it. In his car. For fuel. For free. Think about that the next time you fill your SUV’s gas tank at prices approaching $2 a gallon. “Restaurants have to discard huge amounts of frier grease, and I’ve found a way to fuel my car with it,” Holton said. Of course, nothing’s absolutely free. There is some work involved, but not much. Holton bought a car with a diesel engine, a 1982 Mercedes. It’s a clean car and it looks good. The engine’s in great shape (diesels have a reputation for near-immortality). But the car’s so out of style, few people want it. Price: $1,000. Then there’s the equipment the car needs to run on frier grease: a separate fuel tank, gauge, and fuel line; a valve and switch to change from diesel to vegetable oil; a last-step filter on the fuel line to keep particles out of the engine; a heat exchanger to warm the vegetable oil in the tank; and hoses to run coolant in and out of the heat exchanger. And there are a few 55-gallon drums at home, a sock filter, and an electric pump. The cost for that setup? “Probably another $1,000,” Holton said, adding that the equipment needed to convert to veggie oil can be purchased from http://www.greasel.com. On the other hand, Holton has yet to empty his diesel tank of its first fill-up back in early July. “I’m no purist,” Holton said. “I do run diesel.” Holton starts and runs the car on diesel until the engine is warm enough to send hot coolant to the heat exchanger in the vegetable oil tank (about five minutes) and then he flips a switch on his dashboard. At about 180 to 190 degrees, the vegetable oil attains the consistency of diesel, he said. “When I switch to vegetable oil, the engine smooths out and runs more quietly,” he said. His exhaust? “Carbon dioxide and water vapor.” Holton explained that Rudolf Diesel’s engines were originally designed to run on peanut oil, a product that no doubt was more plenteous than gasoline refined from crude oil in the late 1800s. Later, the engine was fueled by the gasoline-refining process's oily byproduct, now called diesel oil. “All I’m doing is using my diesel engine the way it was designed to run,” Holton said. The engine’s unique design—the reason it outlasts the conventional gasoline-powered engine—is its high-compression cylinder and fuel injection system that eliminates the need for spark plugs or electronic ignition. Air is compressed in the cylinder to at least a 14:1 ratio, sometimes as high as 25:1, making the air so hot it ignites the fuel-air spray as it is injected into the cylinder. At that high compressed-air temperature, vegetable oil ignites as readily as diesel oil. “And with vegetable oil, there’s no coking around the injectors,” Holton said. Also, Holton gets about 27 miles per gallon with vegetable oil, compared with 25 mpg on diesel oil. “And I see no difference in performance. I’ve never lacked for acceleration.” Before Holton’s discarded vegetable oil can be used for fuel, he has to filter out food particles left from the frying process. He pumps the oil through a sock filter that filters down to .5 microns and into a 55-gallon drum from which he fills his fuel tank. “In one Saturday afternoon, I can filter up to 200 gallons for use later.” Holton gives new meaning to self-serve. “Those gas station-convenience stores never did look too safe to me. I’d certainly never visit one late at night.” Why should he, when he can fill up in his own driveway?
Friday, April 30, 2004
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