In order to demonstrate the performance of a retrofitted selective catalytic reduction (SCR) system while also addressing the issues associated with greater use of biodiesel, a 2005 International 9200i tractor owned by the City of Santa Monica was retrofitted with a titania-vanadia-tungsten catalyst and a urea dosing system supplied by Extengine Systems, Inc. This tractor was operated under normal service conditions within the City of Santa Monica refuse collection and transportation fleet. An on-board emissions measurement system supplied by Engine, Fuel, and Emissions Engineering, Inc. was installed on the vehicle; it measured the emissions and fuel use of the vehicle while it operated on ultra-low-sulfur diesel (ULSD), 20% biodiesel (B20), and 99% biodiesel (B99) on consecutive days. The vehicle, with a similar aftertreatment system, was then tested at the California Air Resources Board (CARB) Los Angeles Heavy-Duty Emissions Lab and tested on the Urban Dynamometer Driving Schedule (UDDS) to again assess the effects of ULSD, B20, and B99 on the performance of the urea-SCR aftertreatment system.
Results from this testing showed that oxides of nitrogen (NOx) emissions increased by 6%–12% when the blend was increased from ULSD to B20, by 16%–35% when the blend was increased from ULSD to B99, and by 26%–27% when it was increased from B20 to B99. Particulate matter (PM) emissions decreased by 37%–50% when the blend was increased from ULSD to B20, by 71%–79% when it was increased from ULSD to B99, and by 60%–63% when it was increased from B20 to B99. The SCR system reduced NOx emissions by 64%–87% and its performance was not affected by the use of biodiesel