Greenhouse gas emissions from heavy-duty vehicles

Abstract

This paper summarizes greenhouse gas (GHG) emissions measurements obtained during several recent studies conducted by Environment Canada, Emissions Research and Measurement Division (ERMD). A variety of heavy-duty vehicles and engines operating on a range of different fuels including diesel, biodiesel, compressed natural gas (CNG), hythane (20% hydrogen, 80% CNG), and liquefied natural gas (LNG), and with different advanced aftertreatment technologies were studied by chassis dynamometer testing, engine dynamometer testing or on-road testing. Distance-based emission rates of CO 2, CH 4, and N 2O are reported. Fuel consumption calculated by carbon balance from measured emissions is also reported. The measurement results show, for heavy-duty diesel vehicles without aftertreatment, that while CO 2 emissions dominate, CH 4 emissions account for between 0% and 0.11% and N 2O emissions account for between 0.16% and 0.27% of the CO 2-equivalent GHG emissions. Both of the aftertreatment technologies (diesel oxidation catalyst and active regeneration diesel particle filter) studied increased N 2O emissions compared to engine out emissions while CH 4 emissions remain essentially unchanged. No effect on tailpipe GHG emissions was found with the use of up to 20% biodiesel when the engine was equipped with an oxidation catalyst. Biodiesel use did show some reductions in tailpipe GHG emissions as compared to ULSD without aftertreatment and with the use of a diesel particle filter. Natural gas and hythane also offer decreased GHG emissions (10–20%) at the tailpipe when compared with diesel. Emission factors (g L −1 fuel) for CH 4 and N 2O are suggested for heavy-duty vehicles fueled with diesel-based fuels and natural gas. These emission factors are substantially lower than those recommended for use by IPCC methodologies for developing national inventories.