On left, raw trap grease with most of the free water removed; center, grease after filtering but before final dewatering; right, biodiesel fuel. Image courtesy Philadelphia Fry-o-Diesel, LLC.

Turning Grease into Fuel

By Laura McGinnis
September 28, 2006

New work from the Agricultural Research Service (ARS) could someday help the nation’s cars run like greased lightning, powered by biodiesel made from restaurant grease.

Mike Haas, a chemist at the ARS Eastern Regional Research Center in Wyndmoor, Pa., is working with the Philadelphia Fry-o-Diesel company (PFOD) to demonstrate that trap grease-- the grease that restaurants and food companies collect from their drains--can be converted into a clean-burning, renewable fuel source. In May, the Philadelphia Federal Executive Board awarded Haas a gold medal for his contributions to the project.

Trap grease is currently unmarketable. According to PFOD, restaurants in southeastern Pennsylvania and New Jersey collect more than 2 million gallons of trap grease every month that must be removed at a cost of about 5 cents per gallon. Illegal disposal and sloppy collection can lead to clogged sewers and polluted water.

PFOD enlisted Haas to help demonstrate trap grease’s potential as a marketable biodiesel feedstock. Haas and ARS biologist Karen Scott helped characterize trap grease samples, advised the company on operation design, and analyzed the products of trial runs as they explored and improved the reaction chemistry needed to produce biodiesel.

How does it work? The scientists remove water and solids from the trap grease, then process the feedstock to produce biodiesel. Initial small-scale operations have successfully produced fatty acid methyl esters from trap grease. The esters will be tested to determine whether they meet accepted biodiesel standards.

One challenge right now is economic. Removing impurities from trap grease is expensive, but as the cost of petroleum-based diesel rises, it’s becoming increasingly competitive.

If successful, this research could solve many problems. Giving trap grease a new purpose would reduce waste and create a new market. Illegal disposal would decrease, leading to improved water quality, and cleaner-burning diesel fuels would improve air quality.

ARS is the U.S. Department of Agriculture’s chief scientific research agency.