Comparison of Pollutant Emissions from Common Platform Vehicles Operating on Alternative Fuels over a Range of Driving Cycles at Standard and Cold Ambient Temperatures 2016-01-2216

Alternative fuels and power trains are expected to play an important role in reducing emissions of greenhouse gases (GHGs) and other pollutants. In this study, five light-duty vans, operating on alternative fuels and propulsion systems, were tested on a chassis dynamometer for emissions and efficiency. The vehicles were powered with Tier 2 gasoline, low blend ethanol (E10), compressed natural gas (CNG), liquefied petroleum gas (LPG), and an electric battery. Four test cycles were used representing city driving and cold-start (FTP-75), aggressive high speed driving (US06), free flow highway driving (HWFCT), and a combination of urban, rural, and motorway driving (WHVC). Tests were performed at a temperature of 22°C, with select tests at -7°C and -18°C.

Exhaust emissions were measured and characterized including CO, NO_X, THC, PM and CO₂. On the FTP-75, WHVC, and US06 cycles additional exhaust emission characterization included N₂O, and CH₄. On the FTP-75, carbonyl compounds and volatile organic compounds (VOCs) were also characterized. Fuel and energy consumption, CO_2,e and NMOG emissions were calculated.

The emissions impact of alternative fuels varied with temperature and driving cycle. Compared to conventional gasoline, the use of alternative fuels generally resulted in reduced CO₂ equivalent emission rates: 12-14% reduction with the use of LPG fuel, 18-21% reduction with the use of CNG fuel, and 60-75% reduction with the use of battery electric propulsion (assuming the average Canadian mix for electricity generation). With E10 fuel, the reductions in tailpipe CO₂ equivalent emission rate were generally not statistically significant. Results for other regulated and unregulated emissions varied, and depended on driving cycle and temperature.