NIR Helps Turn Vegetable Oil into High-Quality Biofuel

By Linda McGraw

June 15, 1999

PEORIA, Ill., June 15 -- To help speed the development of biodiesel fuels made with vegetable oils, scientists at USDA's Agricultural Research Service here have adapted a sophisticated tool known as near-infrared spectroscopy, or NIR.

Baby-boomers remember the lines at gas stations when the oil embargo of the 1970s hit. Despite the oil shortage, America's farm tractors continued to roll because of USDA research that turned vegetable oils into alternative fuels.

The trend will continue in the 21st century, when motorists will see more public vehicles -- buses, trains, trucks, and government-owned maintenance equipment -- running on biodiesel fuels made from soybean oil. By the year 2001, the Federal Energy Policy Act requires that 75 percent of all new state and federal vehicles be filled with alternative fuels.

Until now, the standard for measuring biodiesel quality has been a complex analytical method called gas chromatography, or simply GC.

"But GC is a complex piece of laboratory equipment, requiring technical expertise and at least an hour to perform," said Gerhard H. Knothe, an ARS chemist in Peoria, Ill. Another drawback of GC is it requires chemical reagents and solvents that need special handling and costly disposal.

Knothe has developed a safer and faster way to check the quality of biodiesel fuel by using NIR. Much of the pioneering work on biodiesel fuels began where Knothe works, at ARS' National Center for Agricultural Utilization Research.

"NIR is a nifty tool also used for determining fatty acid composition in vegetable oils and oil content in seeds," said Knothe. Another plus: No special training is needed to perform the NIR test.

The researchers are developing the method for more effective production monitoring and fuel quality control, improvements needed by the biodiesel producers. Biodiesel producers need to know early if the chemical reactions that occur during biodiesel fuel production are successful.

Using NIR, Knothe can measure the conversion of vegetable oil to biodiesel fuel in less than a minute.

NIR coupled with a fiber-optic probe uses light rather than chemicals to perform the analysis. Checking the biodiesel fuel quality is important because potential contaminants in the fuel could lead to engine deposits. "Our test will help biodiesel fuel producers determine if their products meet the quality standards of the American Society for Testing and Materials," Knothe said.

Dr Gerhard Knothe is willing to help users implement NIR testing for biodiesel. E-mail:

NIR Helps Turn Vegetable Oil into High-Quality Biofuel -- ARS News Release, June 15, 1999

Rapid Monitoring of Transesterification and Assessing Biodiesel Fuel Quality by Near-infrared Spectroscopy Using a Fiber-Optic Probe, by Gerhard Knothe, JAOCS 76, 795-800 (July 1999)

Monitoring a Progressing Transesterification Reaction by Fiber-Optic Near Infrared Spectroscopy with Correlation to 1H Nuclear Magnetic Resonance Spectroscopy, by Gerhard Knothe, JAOCS 77, 489-493 (May 2000)

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