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Diesel prescriptions: eat some veggies....

Diesel prescriptions: Eat some veggies ...

U.S. diesel engines consume about 30 billion gallons of fuel each year, driving everything from tractors and trains to long-distance trucks, industrial processes and power plants. Currently, a petroleum distillate fuels them. But as domestic petroleum stocks dwindle, interest is building in potential alternatives that might sever the diesel's dependence on oil. Among some promising candidates are alcohol-modified "vegetable oils."

Engineers at the University of Illinois in Urbana-Champaign have been working with oils from corn, peanuts, castor, cottonseed, crambe, linseed, soybeans, rapeseed, sunflowers, sesame and safflower. To date, their most promising cocktail is a microemulsion of ethanol, soybean oil and a touch of detergent. The concoction can accept up to 40 percent alcohol and perform well, says mechanical engineer Lester Savage. And by "cracking" the soybean oil--heating it until it begins to break down -- then adding a little anhydrous ammonia, the researchers can essentially "build in" the detergent needed to stabilize the microemulsion. At this point, Savage says, all it takes is some still-grade (150-proof) ethanol to make a fuel. This raises the possibility that many farmers could become energy-self-sufficient.

A second approach is to mix an alcohol--ethanol, propanol or methanol--with an oil and dessicant to form an ester. At Illinois, Carroll E. Goering has successfully run tractor field tests with 2,000 gallons of soybean-oil ester. Its main drawback is cost. Unlike the microemulsion fuel--which researchers say might be developed for $1.60 per gallon, or a little less than twice the current cost of diesel fuel--the ester fuels might cost $3 to $4 per gallon. However, in a pinch--such as another Arab oil embargo--it offers a fallback.

Austrian researchers are exploring a related option that might prove more cost-effective while eliminating a troublesome waste. Martin Mittelbach and Peter Tritthart at Karl Franzens University's Institute for Organic Chemistry in Graz created a methyl ester from 441 pounds of used vegetable oils collected from restaurants and households. The oil varied from liquid to solid and "was heavily polluted with pieces of food and cooking residues," they write in the July JOURNAL OF THE AMERICAN OIL CHEMISTS' SOCIETY.

Without attempting to purify the oil, the researchers added methanol and potassium hydroxide, then stirred. They separated a glycerol layer that formed--containing most of the impurities--and then washed with water the resulting ester layer. An organic layer was dried and filtered out.

This fuel offered about 10 percent less power than regular diesel fuel, but burned cleaner (except for a slight increase in nitrogen oxide emissions). Most notable were its lower smoke emissions--generally less than half those emitted when diesel oil was burned. The frying-oil ester was also used in a 50-50 mix with standard diesel oil and burned in a Volkswagen Rabbit diesel. "No changes in operation whatsoever could be observed," they say. However, they note, "a faint smell of burnt fat was detected."
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Title Annotation:research on alternative fuels
Publication:Science News
Date:Aug 20, 1988
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