Biodiesel a Fuel Option for Army Workboats

A three-year study to evaluate the feasibility of using biodiesel fuel in U.S. Army Corps of Engineers (USACE) floating plant operations has concluded that the use of such fuels does not negatively affect engine performance and can reduce production of selected environmentally sensitive emissions.

A range of biodiesel blends—B5, B10, B15, B20 and B100—derived variously from soybeans and algal oils were tested in place of ultra-low-sulfur diesel (ULSD) on 14 vessels, including a dustpan dredge, a hopper dredge, four towboats, three debris-removal vessels, three crane barges, a tug and a crew boat. Monitoring consisted of both crew observation and installation of instrumentation onboard vessels to gauge fuel use, engine power and emission levels at preselected levels of engine loading.

U.S. Army Engineer District St. Louis (MVS) towboat Grand Tower. Image credit: USACE.

Use of biodiesel was associated with a reduction in soot and overall cleaner appearance of the insides of the engines. None of the vessel operators had issues related to engine power or efficiency, and there were no negative effects on routine vessel operations. No noticeable performance impacts were observed switching between diesel fuel and biodiesel.

Emissions testing for CO2, CO, NOx and PM2.5 was conducted on two USACE debris-removal vessels at 25%, 50%, 75% and 100% engine loads with three different fuels: B100, ULSD and Solazyme. Tests showed both CO and PM2.5 emissions for B100 were significantly less than they were for ULSD or Solazyme, while CO2 emissions were approximately the same for all three fuels. Solazyme, with its higher cetane number, had the lowest NOx emissions.

Emissions factors as defined in ISO 8178 (ISO 1996) were calculated from the emissions measurements. B100 was found to be lower than the EPA Tier 2 standards for all three regulated emissions (CO, NOx, PM2.5). ULSD and Solazyme were lower than the Tier 2 standards for CO and NOx but higher than the Tier 2 standard for PM2.5.

Fuel consumption was also measured during the emissions testing. While it was expected that the approximately 10% lower energy content of a gallon of B100 in comparison to a gallon of ULSD would mean a 10% increase in fuel consumption of B100 at the load points, measurements did not show this to be the case. For one of the vessels, the B100 fuel consumption was measured to be an average of approximately 2% higher than ULSD, while for the other vessel the average B100 consumption was approximately 1% lower.

All of the USACE districts that participated in the study plan to continue their use of biodiesel fuel.