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Cedarwood Oil: Making It More Aromatic, More Available

By Linda McGraw
June 17, 1999

PEORIA, Ill., June 17--When you can't see the forest for the trees, focus on the tree's valuable products.

That's the approach that scientists Fred Eller and Jerry King at the Agricultural Research Service have taken in developing an environmentally safe method to extract more and better quality cedarwood oil from juniper trees.

The extraction method, known as supercritical fluid extraction (SFE), already benefits consumers who drink decaffeinated coffee.

Cedarwood oil--used in cosmetics, perfumes, home odorants, and as an insect control agent--is usually extracted from sawdust and wood chips by steam distillation. But this extraction method produces low oil yields and often decomposes the oil, causing it to have an off-odor.

In lab tests, Eller obtained 30 percent more oil than the yield from conventional steam distillation without destroying the oil's aromatic components.

"Steam distillation doesn't penetrate deeply into chips, so it averages only a 50 percent yield of the oil from the wood," said Eller, a chemist at ARS' National Center for Agricultural Utilization Research in Peoria, Ill. The presence of oxygen and high temperatures in steam distillation also erodes oil quality.

But SFE, which uses carbon dioxide (CO2), works better "because it diffuses in and out of the wood more easily than steam, carrying the cedarwood oil with it. The CO2 is then easily removed from the extract when the mixture is depressurized. This leaves a more pure oil that's uncontaminated by solvent residue," Eller said.

Because SFE operates in an oxygen-free atmosphere, the oil's components aren't degraded, making the cedar aroma more similar to the original wood chips than the oil extracted by steam distillation. That's based on an odor analysis by Peoria researchers.

On Western rangelands, where cattle and wildlife subsist on forage grass, juniper trees and shrubs are unwelcome inhabitants. The reason: The trees crowd out forage grasses and deplete the soil of water and nutrients needed for other plants. In the Midwest and Southwest, farmers and cattle ranchers routinely remove junipers from fields and ranges at significant expense.

Eller and King envision someday being able to develop a mobile SFE unit that farmers could use to produce a value-added product. This could be an economic boost especially for Midwestern farmers, where more land is being invaded by junipers. Cedarwood oil is currently valued between $4.00 a pound (for Texas oil) and $7.00 (for Virginia oil).