Covadonga Astorga

In this manuscript, we evaluated different emission scenarios for light-duty road transport to evaluate their impact on air quality in the EU, with a focus on a number of cities by means of the EMEP (European Monitoring and Evaluation Programme) modelling system. In addition to the reference case scenario, where exhaust emission factors from COPERT (Computer Programme to calculate Emissions from Road Transport) corresponding to the existing fleet were used, we also tested future potential scenarios considering: (a) all passenger cars and light commercial vehicles meet the EURO 6 emissions standard and EDGAR (Emission Database for Global Atmospheric research) EURO 6 emission factors; (b) all passenger cars and light commercial vehicles meet the EURO 6 emissions standard and real-world emission factors derived from actual Euro 6d-TEMP/6d vehicles. Results show how the replacement of old vehicles by newer ones with better emission control technologies can help improve air quality in the EU in terms of reductions in NO₂ and PM_2.5 concentrations. However, reduced NO_x emissions in cities (as foreseen in the two scenarios analysed) will cause tropospheric O₃ to increase.

The transport sector is an important source of air pollution. Seasonal studies have shown that, in some urban areas, pollution episodes often take place during the cold season. This study investigates how sub-zero ambient temperatures (between −8 °C and −1 °C) and high altitudes (from 1300 to 2000 m above sea level) impact the on-road emissions of NOx, CO, PN and CO₂ from three Euro 6d-TEMP certified vehicles—one diesel, one gasoline and one plug-in hybrid gasoline–electric vehicle (PHEV). In comparison to tests performed at moderate altitude and ambient temperatures, CO, NOx and PN emissions increased under sub-zero temperature, high-altitude conditions for all three vehicles tested. In particular, cold-start emissions from all tested vehicles substantially increase as temperature decreased. Nevertheless, the emissions of NOx and PN met the Euro 6d-TEMP on-road emission requirements of the Real Driving Emissions (RDE) test procedure. CO emissions from the diesel and the gasoline vehicles were low. The PHEV had consistently low NOx emissions (ranging from 4 to 33 mg km⁻¹), but emissions of CO (1010–1849 mg km⁻¹) and PN (3.5 × 10¹¹ to 1.0 × 10¹² # per km) were high in some cases. Our results add to the body of evidence indicating that, following the introduction of the RDE in the EU, more efficient emission control technologies are being used to reduce the emissions of NOx and PN—the pollutants covered by this test procedure—particularly NOx from diesel vehicles. However, the emissions of PN from the two gasoline vehicles were high (>1 × 10¹² # per km) under certain experimental conditions. This result is a reason for concern, because PN emissions from vehicles using the fuel injection technology (PFI, port fuel injection) investigated in this study are not limited by the current Euro 6 regulation. This underlines the need for technology- and fuel-neutral approaches to vehicle emission standards, whereby all vehicles must comply with the same emission limits for the same pollutants regardless of the technologies or fuels employed.

Background: Road transport is an important contributor to the European Union’s total greenhouse gas emissions. This study aims at summarizing methane (CH₄) and nitrous oxide (N₂O) exhaust emissions from L-category, light-duty and heavy-duty vehicles in the European Union. The assessment is based on measurements carried out in the Vehicle Emission Laboratory of the Joint Research Centre between 2009 and 2019. The exhaust chemical composition from a fleet of 38 L-category vehicles Euro 1 to Euro 4 (2- and 3-wheelers, small quadricycles such as quads and minicars), 63 light-duty vehicles from Euro 5b to Euro 6d-TEMP (passenger cars, including hybrid vehicles), and 27 light commercial and heavy-duty vehicles from pre-Euro I to Euro VI (including lorries, buses and garbage trucks) was analyzed by Fourier-transform infrared spectroscopy. Results: CH₄ emission factors monitored were from 1 to 234 mg/km for L-category vehicles (mean: 39 mg/km), from 0.1 to 40 mg/km for light-duty vehicles (mean: 7 mg/km), and from non-detectable to 320 mg/km for heavy-duty vehicles (mean: 19 mg/km). N₂O emission factors monitored were from non-detectable to 5 mg/km for L-category vehicles (mean: 1 mg/km), from non-detectable to 40 mg/km for light-duty vehicles (mean: 7 mg/km), and from non-detectable to 118 mg/km for heavy-duty vehicles (mean: 19 mg/km). According to the 100-year Global Warming Potential of these greenhouse gases, these emissions corresponded to a range from negligible up to 9 g/km of CO₂-equivalent for CH₄ and from negligible up to 32 g/km of CO₂-equivalent for N₂O. Conclusions: The higher contributors of CH₄ were the two-stroke mopeds included in the L-category vehicles, while the higher emissions of N₂O were found in the modern (Euro 5–6 or Euro V–VI) diesel light- and heavy-duty vehicles. Among them, vehicles complying with Euro 6 and Euro VI standard were associated to higher N₂O emissions compared to those associated to Euro 5 and pre-Euro IV standards, which could be attributed to the introduction of the after-treatment systems designed to fulfill more stringent NOx standards. These updated emission factors and unique on its kind database represent a source of information for legislators and modelers to better assess the greenhouse gas emission reduction in the EU transport sector.

The transport sector is one of the main sources air pollutants. Different exhaust after-treatment systems have been implemented over the years to control the emissions of criteria pollutants. However, while reducing the emissions of the target compounds these systems can lead to the emissions of other pollutants and/or greenhouse gases such as NH₃ or N₂O. Following the implementation of the Real Driving Emissions (RDE) test procedure in the EU, vehicles have been equipped with more complex after-treatment configurations. The impact that these technologies may have on the emissions of non-regulated pollutants during real-world driving have not been evaluated until now. In the current study we present the on-road emissions of a series of non-regulated pollutants, including NH₃, N₂O, CH₄ and HCHO, measured with a portable FTIR from a series of Euro 6d, Euro 6c and Euro 6d-TEMP, gasoline diesel and compressed natural gas (CNG) vehicles during real-world testing. The obtained results show that it is possible to measure N₂O, NH₃, CH₄ and HCHO during on-road operation. The results also highlight the importance of the measurement of the emissions of these pollutants during real-world driving, as the emissions of NH₃ (a particulate matter precursor) and those of N₂O and CH₄ (green-house gases) can be high from some vehicle technologies. NH₃ emissions were up to 49 mg/km for gasoline passenger cars, up to 69 mg/km for the CNG light-commercial vehicle and up to 17 mg/km a diesel passenger car equipped with a selective catalytic reduction system (SCR). On the other hand, N₂O and CH₄ emissions accounted for up to 9.8 g CO₂ eqv/km for a diesel passenger car equipped with a combination of diesel oxidation catalysts (DOC), lean NO_x traps (LNT), SCR and possibly an ammonia slip catalyst ASC.

Tailpipe emissions of a pool of 13 Euro 6b light-duty vehicles (eight diesel and five gasoline-powered) were measured over an extensive experimental campaign that included laboratory (chassis dynamometer), and on-road tests (using a portable emissions measurement system). The New European Driving Cycle (NEDC) and the Worldwide harmonised Light-duty vehicles Test Cycle (WLTC) were driven in the laboratory following standard and extended testing procedures (such as low temperatures, use of auxiliaries, modified speed trace). On-road tests were conducted in real traffic conditions, within and outside the boundary conditions of the regulated European Real-Driving Emissions (RDE) test. Nitrogen oxides (NO_X), particle number (PN), carbon monoxide (CO), total hydrocarbons (HC), and carbon dioxide (CO₂) emission factors were developed considering the whole cycles, their sub-cycles, and the first 300 s of each test to assess the cold start effect. Despite complying with the NEDC type approval NO_X limit, diesel vehicles emitted, on average, over the WLTC and the RDE 2.1 and 6.7 times more than the standard limit, respectively. Diesel vehicles equipped with only a Lean NO_X trap (LNT) averaged six and two times more emissions over the WLTC and the RDE, respectively, than diesel vehicles equipped with a selective catalytic reduction (SCR) catalyst. Gasoline vehicles with direct injection (GDI) emitted eight times more NO_X than those with port fuel injection (PFI) on RDE tests. Large NO_X emissions on the urban section were also recorded for GDIs (122 mg/km). Diesel particle filters were mounted on all diesel vehicles, resulting in low particle number emission (~10¹⁰ #/km) over all testing conditions including low temperature and high dynamicity. GDIs (~10¹² #/km) and PFIs (~10¹¹ #/km) had PN emissions that were, on average, two and one order of magnitude higher than for diesel vehicles, respectively, with significant contribution from the cold start. PFIs yielded high CO emission factors under high load operation reaching on average 2.2 g/km and 3.8 g/km on WLTC extra-high and RDE motorway, respectively. The average on-road CO₂ emissions were ~33% and 41% higher than the declared CO₂ emissions at type-approval for diesel and gasoline vehicles, respectively. The use of auxiliaries (AC and lights on) over the NEDC led to an increase of ~20% of CO₂ emissions for both diesel and gasoline vehicles. Results for NO_X, CO and CO₂ were used to derive average on-road emission factors that are in good agreement with the emission factors proposed by the EMEP/EEA guidebook.

Plug-in hybrid electrical vehicles (PHEVs) are generally considered to be a cleaner alternative to conventional passenger cars. However, there is still very limited information available regarding criteria pollutant emissions from these vehicles. This paper shows, for the first time, the emissions of criteria pollutants, unregulated pollutants, and CO₂ and also electric range from two very different PHEVs, one Euro 6 parallel plug-in hybrid and one range-extended battery electric vehicle (BEVx), applying the new world harmonized light-duty test procedure at ambient temperatures equal to 23 and −7 °C. The impact of using a cabin air heating system on vehicle electric range and emissions at cold temperature has also been studied. Cold ambient temperatures and, to a larger extent, the use of heating systems have been shown to lead to a pronounced negative impact on emissions and shorter electric ranges. Results also show that modern PHEVs can emit similar, or even higher, levels of pollutants (e.g., particle number) as Euro 6 conventional gasoline and diesel vehicles.