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 diesel engine was mounted on a dynamometer and 
the exhaust was arranged so that sampling was possible both with (“wet” also termed “scrubbing”) and without (“dry”) 
water contact in the exhaust stream. Emissions testing was conducted using the steady state ISO E4 marine duty cycle. 
The engine was tested with 0, 10, 20, 50, and 100% methyl soy-ester blends with #2 off-road diesel. The pure alternative 
fuel offered a 45% reduction in particulate matter for both dry and wet tests, with carbon monoxide decreasing and oxides 
of nitrogen increasing slightly. Particulate matter (PM) reduction is significant 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 influence on the 
production of acetaldehyde, acetone, and formaldehyde in the exhaust. However, it was evident that wet testing, where the 
water contacted the cooling water, produced substantially lower formaldehyde and acetone, but 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.