Waste Cooking Oil Biodiesel Use in Two Off-Road Diesel Engines

Abstract

This study examines the composition and combustion performance of biodiesel produced from waste cooking oil. Six fuel batches produced from waste oil used in dining-hall fryers were examined to determine their physical and chemical properties, including their elemental and fatty acid methyl ester composition. Oleic and linoleic methyl esters accounted for more than 70% of the fuel composition, while the oxygen content averaged 10.2% by weight. Exhaust emissions were monitored for 5–100% biodiesel blends using two off-road engines: a 2007 Yanmar diesel generator and a 1993 John Deere front mower. Increasing biodiesel content resulted in reduced emissions of partial combustion products from the diesel generator but a rise in NO_x, with the greatest changes occurring between 5 and 20% biodiesel content. For the riding mower, biodiesel content up to 50% had little effect on emissions, while NO_x and total hydrocarbon emissions decreased with 100% biodiesel. The difference in NO_x emissions is attributed to the two different fuel injection control designs used in the two engines. These results indicate that the effects of biodiesel use on nonroad engine exhaust emissions may be substantially lower in older engines optimized for performance over emissions control.