Marshall, Minn. — Gathering buckets of greasy, grimy waste oils from restaurants is no glamorous task, but Rose Patzer does it for science. And economics: her slimy collection is helping reduce the cost of biodiesel fuel.

During the past year, Patzer, a process chemist at AURI’s fats and oils lab in Marshall, has retrieved waste greases from local eateries, converted them to methyl esters, and blended them with soy methyl esters to achieve a reduced-cost biodiesel fuel blend.

Costs less, works in the cold

Biodiesel, generally made from renewable soybean oil, is an alternative fuel with huge potential. Generally blended with petroleum diesel, biodiesel has been shown to reduce emissions and increase fuel lubricity, which means less wear and tear on engines. It also represents a potentially massive market for soy oil.

But cost remains a barrier to large-scale market entry. To give biodiesel a boost, Patzer is blending methyl esters from both recycled grease and soybean oil to cut production costs.

“Biodiesel made from recycled grease costs about seven and a half cents a pound,” Patzer says. “Soybean oil will convert more readily than recycled grease and has a lower gel point. Mixing the two gives us a blend that has the properties we want at a lower cost.”

“The goal of this project is to come up with a cheaper biodiesel that handles the cold,” says Ken Bickel of the University of Minnesota Center for Diesel Research. Bickel is conducting lab tests on the waste grease blend in a Caterpillar 3116 engine.

A workable mix for engine testing turns out to be a “B20” blend containing 10 percent yellow grease methyl esters (yellow grease is waste grease that has been cleaned), 10 percent soy methyl esters and 80 percent petroleum diesel.

Bickel will run three tests at the diesel research center using straight diesel and three with the B20 blend. He’ll measure carbon monoxide, hydrocarbon and particulate emmissions. And he’ll observe any changes in engine power resulting from the alternative fuel.

On the road again

After engine tests are complete, road tests will begin. Hennepin County previously participated in a road study using biodiesel in several highway maintenance vehicles to evaluate the fuel’s power, storage and handling qualities in cold weather. Bickel says the study will continue utilizing the waste grease blended fuel.

Many eyes will be scrutinizing the test results. The recycled grease project was funded by the Legislative Commission on Minnesota Resources and represents collaboration with AURI, the Minnesota Soybean Research and Promotion Council, the Center for Diesel Research and the Minnesota Department of Agriculture.

“With the cost of petroleum diesel going up and the utilization of waste grease esters bringing the price of biodiesel down, the cost margin is getting a lot more narrow for B20,” Patzer says. “Now is a good time to push for market entry.”