Characterizing emission rates of regulated and unregulated pollutants from two ultra-low NOx CNG heavy-duty vehicles

Exceedances of Secondary Aerosol Formation from In-Use Natural Gas Heavy-Duty Vehicles Compared to Diesel Heavy-Duty Vehicles

“…Previous studies have shown that primary aerosol mass emissions for CNG vehicles are typically sourced from the pyrolysis or incomplete combustion of engine lubricating oil, which can find a pathway into the combustion chamber through insufficient sealing of the piston rings and intake valves. ,,− For CNG1 and CNG2, the nature of the primary aerosol composition indicates lightly oxidized or partially combusted lubricant oil fragments that escaped the TWC, while for the other CNG vehicles, the nature of the primary aerosol composition was likely due to heavily combusted lubricant oil, as discussed in a later section. The contribution of lubricant oil POA emitted from diesel and gasoline vehicles has also been reported elsewhere. , For example, Sonntag et al showed that the contribution of lubricant oil to PM was over 25% across a fleet of 99 vehicles.…”

“…On-road heavy-duty (diesel) vehicles are a major emission source of nitrogen oxides (NOx), particulate matter (PM), and volatile organic compounds (VOCs) that contribute to urban atmospheric pollution. − Recent advances in engine technology and aftertreatment controls driven by strict policies to tighten emission certification standards have led to a steady reduction of these pollutants. , Further measures to reduce tailpipe emissions from heavy-duty vehicles include the use of biomass-derived low-carbon fuels, such as hydrogenated vegetable oils (HVO), and the widespread use of natural gas vehicles. − HVO is a highly paraffinic diesel-like fuel, free of sulfur, and aromatic compounds that has been shown to provide solid reductions in NOx, PM, and other harmful pollutants . On the other hand, stoichiometric compressed natural gas (CNG) engines, especially those certified to 0.02 g/bhp-hr of NOx emissions, have been shown to achieve significant NOx reductions with additional reductions in PM and VOC emissions compared to current technology heavy-duty diesel vehicles. ,, These advances for on-road heavy-duty vehicles are particularly important in California, where major regions including the South Coast Air Basin are in nonattainment for PM and ozone.…”

“…10 On the other hand, stoichiometric compressed natural gas (CNG) engines, especially those certified to 0.02 g/ bhp-hr of NOx emissions, have been shown to achieve significant NOx reductions with additional reductions in PM and VOC emissions compared to current technology heavyduty diesel vehicles. 8,11,12 These advances for on-road heavy-duty vehicles are particularly important in California, where major regions including the South Coast Air Basin are in nonattainment for PM and ozone.…”

Environmental impact assessment and normalization of different expressway sub-projects during construction

“…Among the three stages, the contribution of material transportation to OF-H accounted for a large proportion (21.86%) during road construction (including subgrade and roadway construction). This may be owing to the large amount of NO x emissions by heavy road vehicles during material transportation (Zhu et al, 2020). Except for the 68.58% contribution to OF-H in road construction, material production was the primary contributor to the other environmental impact categories (contributing 78.63%-97.65% to the LCA).…”

Energy sustainability in the transport sector using synthetic fuels in series hybrid trucks with RCCI dual-fuel engine

“…Alternative fuels, as synthetic fuels derived from green energy sources, have the potential to reduce the Well-to-Wheel CO 2 emissions due to the low Well-to-Tank (WTT) emissions associated to their production processes [23]. These fuels offer an additional degree of CO 2 reduction since they combine the use of this emission as raw material, together with renewable energy, to obtain a wide range of molecules that can be burn in conventional internal combustion engines [24].…”