Lower NOx but higher particle and black carbon emissions from renewable diesel compared to ultra low sulfur diesel in at-sea operations of a research vessel

Gas and particle emissions from R/V Robert Gordon Sproul were measured for ultra low sulfur diesel ( ULSD) and hydrogenation derived renewable diesel ( HDRD) during dedicated aerosol measurement cruises in 2014 ( 29 September-3 October) and 2015 ( 4-7 and 26-28 September). CO, CO2, and NOx were measured directly from the starboard stack from the 2-stroke, small bore, high speed engine, while number and mass size distributions for both particles and black carbon ( BC) were measured by intercepting the ship plume. Measurements at constant engine speeds ( 1600 rpm, 1300 rpm, 1000 rpm, and 700 rpm) had emission factors of CO ( EFCO) and NOx(EFNOx) that were lower by 20% and 13%, respectively, for HDRD compared to ULSD at 700 rpm. However, at 1600 rpm, EFCO and EFNOx were within one standard deviation for both ULSD ( EFCO: 4.0 +/- 0.1 g [kg-fuel](-1); EFNOx : 51 +/- 0.8 g [kg-fuel](-1)) and HDRD ( EFCO: 3.9 +/- 0.2 g [kg-fuel](-1); EFNOx : 51 +/- 2 g [kg-fuel](-1)). HDRD emission factors of particle number and mass concentrations were higher than ULSD by 46% to 107% and 36% to 150%, respectively, at 1600, 1300, and 1000 rpm, but the differences were smaller than the cycle-to-cycle variability at 700 rpm. BC mass emission factors were nearly 200% larger for 700, 1000, and 1300 rpm for HDRD compared to ULSD, but the mass differences were smaller than cycle-to-cycle variability at 1600 rpm. BC mass size distributions showed that the peak diameter of the BC mass mode for ULSD ( similar to 120 nm) is about 20 nm larger than for HDRD ( similar to 100 nm), even though the particle mass and number size distributions are quite similar.