Use of soy-derived fuel for environmental impact reduction in marine engine applications

Diesel-fueled marine engines can contribute to both air and water pollution , particularly when cooling water is contacted with products of combustion in the exhaust system. Soy-derived compression ignition fuel offers a route to reducing these emissions and their effects, A 1972 Westerbeke marine di esel engine was mounted on a dynamometer and the exhaust was arranged so th at sampling was possible both with ("wet" also termed "scrubbing") and with out ("dry") water contact in the exhaust stream. Emissions testing was cond ucted using the steady state ISO E4 marine duty cycle. The engine was teste d with 0, 10, 20, 50, and 100% methyl soy-ester blends with #2 off-road die sel. The pure alternative fuel offered a 45% reduction in particulate matte r for both dry? and wet tests, with carbon monoxide decreasing and oxides o f nitrogen increasing slightly. Particulate matter (PM) reduction is signif icant in the water phase since it was noted that 40% of the PM entered the water phase upon wet testing. Fuel composition did not have a profound infl uence on the production of acetaldehyde, acetone, and fomaldehyde in the ex haust. However, it was evident that wet testing, where the water contacted the cooling water produced substantially lower formaldehyde and acetone, bu t substantially higher acetaldehyde than dry testing, where the exhaust was separated from the cooling water. Dry testing of marine diesel engines may therefore not truthfully reflect oxygenates produced in real use.