CHELSEA V. PREBLE, Rebecca Sugrue, Hannah Schlaerth, George Ban-Weiss, Thomas W. Kirchstetter, University of California, Berkeley
Abstract Number: 784 Working Group: Combustion
Abstract As on-road diesel fleets increasingly adopt diesel particle filters (DPFs) and selective catalytic reduction (SCR) emission control systems, off-road sources like marine vessels will become increasingly important contributors to total diesel PM and NOx emissions. Diesel-related pollution from commercial harbor craft—including ferries, tugboats, and fishing vessels—can negatively impact the air quality and health of near-shore communities. Current emission inventories and regulatory planning efforts assume engine certification emission rates for these commercial harbor craft. However, previous work with the on-road diesel truck fleet shows that a minority of in-use vehicles can emit at levels well above certification limits and dominate total fleet emissions. As such, there is a need to characterize the in-use emissions from these vessels so as to better inform PM, NOx, and greenhouse gas emissions reduction efforts in this sector.
Emissions from in-use commercial harbor craft operating in the San Francisco Bay are measured using the plume capture, carbon balance method. Measurements are made on-board multiple vessels in coordination with their operators. Sampled vessels include engines with and without DPF and SCR systems that meet EPA Tiers 2–4 emission standards. These measurements capture a variety of operating conditions, including steady cruise emissions and variable berthing emissions. Preliminary fuel-based black carbon (BC) and NOx emission factors (g emitted per kg of diesel consumed) are lower and higher, respectively, for diesel powered ferries than heavy-duty diesel trucks with comparable control technologies. Emission factors are related to vessel speed and acceleration via concurrently tracked GPS data; the carbon footprints of commuting by ferry versus by car are also compared.