A research vessel has successfully run on hydrotreated renewable diesel fuel (HRD) for 100% of the time, over the period of one year.
The fuel of the Robert Gordon Sproul was switched to biofuel as part of a project to demonstrate the use HRD on a long-term basis, supported by a grant from the US Department of Transportation in 2014 to the Scripps Institution of Oceanography.
Over the testing period, September 2014-December 2015, the vessel used hydrogenation-derived renewable diesel (HDRD), which was purchased from Neste Oil Corporation under the product name NEXBTL Renewable Diesel.
The ship covered 14,400 nautical miles over 89 operational days at sea, with 52,500 gallons of 100% renewable diesel oil used. No engine modifications were required for the use of the biofuel as fuel. Immediate results have showed decreases in nitrogen oxides (NOx) and CO2 emissions, but also increases in particulate matter.
In order to verify the performance and to compare the emissions and engine performance from either source, the ship’s two tanks held the biofuel and diesel separately. The extensive data collection of carbon monoxide, NOx, organic and black carbon, and engine performance confirmed the test period results.
These tests confirmed that NOx emissions could be reduced by about 13% using biofuel, particularly when the ship is running at lower speeds. However, the use of biofuel also led to increases in particle emissions, especially when the engine was running at higher speeds. Black carbon was also slightly exacerbated when using biofuel.
The postdoctoral scholars carrying out the research, Raghu Betha and Derek Price, both with the Climate, Atmospheric Science and Physical Oceanography (CASPO) division at Scripps, gave their views on the research. Betha suggested that the benefit of having a decrease in CO2 emissions could outweigh the negative of higher particle emissions, since CO2 is a bigger problem for climate. Furthermore, other biofuels previously tested have shown an increase in NOx, whereas this time NOx was decreased.
Price examined the organic chemistry of the particles from the different fuel sources and their characteristics in the atmosphere, determining that both biofuel and diesel plumes were quite similar and composed of long carbon chains of alkanes. In the atmosphere these emissions change in their composition into a more oxygenated form due to aging and photochemical reactions.
The study on the biofuel emissions has been submitted to the journal Aerosol Science and Technology. As the biofuel has proven its success, the research team is hopeful that an academic research ship will facilitate future use of renewable fuels.
Image: The R/V Robert Gordon Sproul, courtesy of the Scripps Institution of Oceanography
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