Motor oil of the future may come from veggies

Vegetable oil similar to the stuff you use to cook your food may one day fill your car’s engine. Researchers at the U.S. Department of Agriculture have developed a chemically modified version of the edible oil that shows promise as a cleaner, renewable alternative to petroleum-based motor oil, while enhancing its protective properties.

Veggie motor oil could eventually be produced cheaper than petroleum-based oil and may help reduce this country’s dependence on foreign oil, the researchers say. Their work was described today at the 225th national meeting of the American Chemical Society, the world’s largest scientific society.

“Vegetable oil is going to have a huge impact on the future by making the world a cleaner, greener place. Our new version is a significant step in that direction,” says Atanu Adhvaryu, Ph.D., a chemist with the USDA’s National Center for Agricultural Utilization Research in Peoria, Ill., and a lead researcher on the project.

The new oil could provide a number of performance-enhancing benefits to car engines. In addition to preventing engines from overheating, it offers improved protection from corrosion, better lubrication and improved dispersion of sludge (insoluble byproducts of oil oxidation), which can clog oil filters and lead to engine damage.

The oil could be available to consumers within five years, Adhvaryu says.

Besides car engines, veggie oil and its derivatives also have a wide-range of industrial applications, including hydraulic fluids, lubricants for heavy machinery and functional fluids for processing metals.

Vegetable-based oils have been increasingly used in automotive and industrial applications, mostly as additives to enhance properties of petroleum-based oils. However, they have been limited in application due to their instability at both low and high temperatures. The other drawback has been their cost: Right now, the cost of developing vegetable oil derivatives is much higher than that of petroleum-based oils.

Adhvaryu and his associates have developed a simple, cost-effective method for enhancing the temperature stability of vegetable oil, while retaining its basic chemistry. They chose soybean oil as their starter material, which is available in surplus quantities.

Like other vegetable oils, the soybean oil molecule consists of a triglyceride molecule. The fatty acid chains of the molecule are highly unsaturated, consisting of multiple double bonds, which contribute to the molecule’s instability at high temperatures.

Using a newly developed technique, the researchers figured out a way to chemically alter the fatty acid chains in order to reduce the amount of double bonding, creating a more stable molecule. They then added new functional groups to make it even more stable.

The researchers are now working on making chemical modifications to the fatty acid portions of the molecule to make it more stable at low temperatures as well. The resulting product is a vegetable oil molecule that is more stable at both hot and cold temperatures, a key requirement for using it as stand-alone engine oil, industrial fluid and specialty grease. While vegetable oil is a good lubricant in its native form, this property is significantly improved by chemical modification of the oil structure, Adhvaryu says.

The same chemical modification methods developed to improve the temperature-stability of soybean oil can be used for practically any type of vegetable oil, including corn, canola, sunflower and safflower oils, he adds.

Disposing of vegetable oil is easier on the environment because it is so biodegradable, the researcher says. It produces small organic molecules, carbon dioxide and water. The breakdown of petroleum-based oil, on the other hand, produces carbon monoxide — thought to contribute to global warming — and unburned hydrocarbons, which are toxic to the environment and harmful to humans.

On a comparative basis, the biodegradability of vegetable oil is generally 90 to 98 percent, compared with 20 to 40 percent for petroleum-based oil, says Adhvaryu. In case of a maritime oil spill or industrial accident, vegetable oil would remain in the environment for a shorter time, he says.

And while petroleum-based oils are limited, non-renewable resources, vegetable-based oil can be developed as needed from renewable plant sources.

Although promising, vegetable oil does have its limitations. It will likely never replace gasoline entirely, which is a petroleum-oil derivative, because vegetable oil is not as flammable by nature, Adhvaryu says.

And unlike the vegetable oil you buy at the supermarket, the new stuff is not edible, he adds.

The USDA provided funding for this study.

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The paper on this research, AGRO 14, will be presented at 10:30 a.m., Monday, March 24, at the Hampton Inn-Convention Center, Riverside I, during the “General Papers” symposium.

Atanu Adhvaryu, Ph.D., is an associate research scientist with the USDA’s National Center for Agricultural Utilization Research in Peoria, Ill., and a research associate with the Department of Chemical Engineering at Penn State University in State College, Penn