AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Atmospheric Impacts of Black Carbon Emissions Reductions through the Strategic Use of Biodiesel
HONGLIANG ZHANG, Kento Magara-Gomez, Michael Olson, Tomoaki Okuda, Keeneth Walz, Michael Kleeman, James Schauer, University of California, Davis
Abstract Number: 382 Working Group: Aerosols, Clouds, and Climate
Abstract The use of biodiesel as a replacement for petroleum based diesel fuel has gained considerable interest in the past decade as a strategy for greenhouse gas emissions reductions, energy security, and economics. The use of biodiesel fuel also has the potential to reduce elemental carbon (EC) concentrations in the atmosphere due to the reduced emissions from conventional diesel engines that are not equipped with after-treatment devices. This study examines the impact of biodiesel blends on EC emissions from a commercial off-road diesel engine and simulates its atmospheric impacts. The reduction in black carbon emissions utilizing pure biodiesel, as compared to ultra-low sulfur commercial diesel (ULSD) fuel, was found to be 76% for the engines examined in this study. Reduced emissions for primary pollutants translate directly into reduced concentrations of these components in the atmosphere, but the effects on secondary particulate matter are more complex. Redistribution of secondary particulate matter to particles emitted from other sources can change the size distribution and therefore potential health effects of those components. Modification of meteorological variables can influence secondary particulate matter formation through non-linear processes. In the present study, simulations that adopted 75% biodiesel blended with ULSD by all non-road diesel engines produced a up to 50% reduction in predicted concentrations of EC, less than ±5% changes in nitrate and total PM2.5 mass concentrations in California. These changes in ground level concentrations did not lead to significant effects on radiative forcing at the top of the atmosphere since the adoption of biodiesel produced larger coatings of secondary particulate matter on atmospheric particles containing residual EC leading to enhanced absorption associated with those particles. The net effect was a minor change in atmospheric optical properties despite a large change in atmospheric EC concentrations. These results emphasize the importance of considering EC mixing state in climate research.