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Compressed natural gas (CNG) and liquefied petroleum gas (LPG) are included in the group of promoted transport fuel alternatives in Europe. Most studies on emissions factors are based on old technology CNG and LPG fueled vehicles. Furthermore, there are not many data at low ambient temperatures, on-road driving, or unregulated pollutants, such as ammonia (NH3). In this study we measured the emissions of one Euro 6b CNG light commercial vehicle, one Euro 6b and one Euro 6d-Temp bi-fuel LPG passenger car, one Euro 6d-Temp bi-fuel CNG passenger car, and four Euro 6d-Temp CNG passenger cars. Tests included on-road testing and worldwide harmonized light vehicles test cycles (WLTC) in the laboratory with cold and hot engine, at 23 °C and −7 °C. The results showed 10–23% CO2 savings in gas modality compared to gasoline, lower CO and particle number emissions, and relatively similar total and non-methane hydrocarbons and NOx emissions. The ammonia emissions were high for all vehicles and fuels; higher than gasoline and diesel vehicles. The results also showed that, following the introduction of the real-driving emissions regulation, even though not applicable to the examined vehicles, Euro 6d-Temp vehicles had lower emissions compared to the Euro 6b vehicles.

European regulation 2016/427 (the first package of the so-called Real-Driving Emissions (RDE) regulation) introduced on-road testing with Portable Emissions Measurement Systems (PEMS) to complement the chassis dynamometer laboratory (Type I) test for the type approval of light-duty vehicles in the European Union since September 2017. The Not-To-Exceed (NTE) limit for a pollutant is the Type I test limit multiplied by a conformity factor that includes a margin for the additional measurement uncertainty of PEMS relative to standard laboratory equipment. The variability of measured results related to RDE trip design, vehicle operating conditions, and data evaluation remain outside of the uncertainty margin. The margins have to be reviewed annually (recital 10 of regulation 2016/646). This paper lays out the framework used for the first review of the NOx margin, which is also applicable to future margin reviews. Based on experimental data received from the stakeholders of the RDE technical working group in 2017, two NOx margin scenarios of 0.24–0.43 were calculated, accounting for different assumptions of possible zero drift behaviour of the PEMS during the tests. The reduced uncertainty margin compared to the one foreseen for 2020 (0.5) reflects the technical improvement of PEMS over the past few years., Graphical abstract fx1, Highlights • Portable Emissions Measurement Systems (PEMS) are used to measure Real-Driving Emissions (RDE) of vehicles. • The uncertainty of PEMS was evaluated based on experimental data and technical requirements prescribed in the European regulation. • The 2017 uncertainty estimation was 43%.

The Horizon 2020 prize for the “Engine Retrofit for Clean Air” aims at reducing the pollution in cities by spurring the development of retrofit technology for diesel engines. A Euro 5 passenger car was retrofitted with an under-floor SCR (Selective Catalytic Reduction) for NOx catalyst in combination with a solid ammonia based dosing system as the NOx reductant. The vehicle was tested both on the road and on the chassis dynamometer under various test cycles and ambient temperatures. The NOx emissions were reduced by 350–1100 mg/km (60–85%) in the laboratory depending on the test cycle and engine conditions (cold or hot start), except at type approval conditions. The reduction for cold start urban cycles was

Nitrogen oxides (NOx) emissions from diesel vehicles are a serious environmental concern. Prior to the introduction of on-road tests at type approval, vehicle on-road NOx emissions were found many times higher than the applicable limits. Retrofitting an existing vehicle is a short/mid-term solution. We evaluated a NOx reduction retrofit system installed on a Euro 6b diesel passenger car both in the laboratory and on the road. The retrofit consisted of an under-floor SCR (selective catalytic reduction) for NOx catalyst in combination with a solid ammonia-based dosing system as the NOx reductant. The retrofit reduced NOx emissions from 25% (50 mg/km) to 82% (725 mg/km) both in the laboratory and on the road. The minimum reduction was achieved at cold start cycles and the maximum at hot start cycles. The retrofit had small effect on CO2 (fuel consumption). No ammonia emissions were detected and the N2O increase was negligible at cold start cycles, but up to 18 mg/km at hot start cycles. The results showed that the retrofit technology could be beneficial even for high emitting Euro 6b diesel vehicles.

The use of selective catalytic reduction systems (SCR) to abate NOx vehicular emissions brings new concerns on the emissions of the byproducts NH 3 and N 2 O. Therefore, NH 3 and N 2 O on-road emissions from a Euro V truck equipped with a SCR were measured in real time using a QCL-IR. Results bring to light possibility to perform this kind of real time measurements for other pollutants besides, hydrocarbons, NOx, CO and CO 2 . The capability to measure NH 3 and N 2 O in a second-by-second basis will allow applying the currently agreed regulatory emissions evaluation for gaseous compounds. Average N 2 O emission factors calculated applying the current PEMS-based data analysis to all available windows from the tests ranged from 0.063 g/kWh to 0.139 g/kWh. Average NH 3 concentrations ranged from 0.9 ppm to 5.7 ppm. Although calculated average N 2 O and NH 3 emissions were within current limits, NOx emissions were substantially higher than Euro V limits under the studied conditions.

The Horizon 2020 prize for the “Engine Retrofit for Clean Air” aims at reducing the pollution in cities by spurring the development of retrofit technology for diesel engines. A Euro 5 passenger car was retrofitted with an under-floor SCR (Selective Catalytic Reduction) for NOx catalyst in combination with a solid ammonia based dosing system as the NOx reductant. The vehicle was tested both on the road and on the chassis dynamometer under various test cycles and ambient temperatures. The NOx emissions were reduced by 350–1100 mg/km (60–85%) in the laboratory depending on the test cycle and engine conditions (cold or hot start), except at type approval conditions. The reduction for cold start urban cycles was, Graphical abstract fx1, Highlights • Many studies report diesel vehicles emitting more than 4 times the type approval NOx in real driving conditions. • One solution is retrofitting them, but there is no legislative background for passenger cars. • The Horizon 2020 prize for the “Engine Retrofit for Clean Air” aims at reducing the pollution in cities. • A Euro 5 retrofitted vehicle showed significant reductions over test cycles, but small at the cold start phases. • In some high speed conditions NH3 and N2O were measured.

This paper presents the World-wide harmonized Light duty Test Cycle (WLTC), developed under the Working Party on Pollution and Energy (GRPE) and sponsored by the European Union (with Switzerland) and Japan. India, Korea and USA have also actively contributed. The objective was to design the harmonized driving cycle from “real world” driving data in different regions around the world, combined with suitable weighting factors. To this aim, driving data and traffic statistics of light duty vehicles use were collected and analyzed as basic elements to develop the harmonized cycle. The regional driving data and weighting factors were then combined in order to develop a unified database representing the worldwide light duty vehicle driving behavior. From the unified database, short trips were selected and combined to develop a driving cycle as representative as possible of the unified database. Approximately 765,000 km of data were collected, covering a wide range of vehicle categories, road types and driving conditions. The resulting WLTC is an ensemble of three driving cycles adapted to three vehicle categories with different power-to-mass ratio (PMR). It has been designed as a harmonized cycle for the certification of light duty vehicles around the world and, together with the new harmonized test procedures (WLTP), will serve to check the compliance of vehicle pollutant emissions with respect to the applicable emissions limits and to establish the reference vehicle fuel consumption and CO2 performance.

Portable emissions measurement systems (PEMS) for gaseous pollutants were firstly introduced in the United States regulation to check the in-use compliance of heavy-duty engines, avoiding the high costs of removing the engine and testing it on a dynamometer in the laboratory. In Europe, the in-service conformity of heavy-duty engines has been checked with PEMS for gaseous pollutants since 2014. To strengthen emissions regulations with a view to minimise the differences between on-road and laboratory emission levels in some cases, PEMS testing, including solid particle number (SPN), was introduced for the type-approval of light-duty vehicles in Europe in 2017 and for in-service conformity in 2019. SPN-PEMS for heavy-duty engines will be introduced in 2021. This paper gives an overview of the studies for SPN-PEMS from early 2013 with the first prototypes until the latest testing and improvements in 2019. The first prototype diffusion charger (DC) based systems had high differences from the reference laboratory systems at the first light-duty vehicles campaign. Tightening of the technical requirements and improvements from the instrument manufacturers resulted in differences of around 50%. Similar differences were found in an inter-laboratory comparison exercise with the best performing DC- and CPC- (condensation particle counter) based system. The heavy-duty evaluation phase at a single lab and later at various European laboratories revealed higher differences due to the small size of the urea generated particles and their high charge at elevated temperatures. This issue, along with robustness at low ambient temperatures, was addressed by the instrument manufacturers bringing the measurement uncertainty to the 50% levels. This measurement uncertainty needs to be considered at the on-road emission results measured with PEMS.

This paper discusses the development and validation of passenger car emission factors, using real world operation data. In total, six passenger cars of different technologies were studied. The tested vehicles were operated under various driving conditions and over two different routes in the region of Lombardia, Italy. These routes were specifically defined in order to provide a range of driving conditions, including urban, rural and highway driving. Tailpipe emissions and exhaust gas flows were measured on-board the vehicle, using a portable emissions measurement system (PEMS). In addition, all vehicles were tested over the European type-approval driving cycle (NEDC) with the same PEMS equipment. The testing of gasoline vehicles showed that emissions are well below the emission standards and do not raise any concern. However, the testing of diesel vehicles both under real-world driving conditions and over the NEDC brought to the surface important concerns regarding the actual NOx emissions of modern diesel vehicles, since they seem to comply with the corresponding emission standard over the type-approval cycle, but they constantly exceed the specified limit when tested under real-world driving conditions. Results from real-world operation revealed that there is a significant deviation from the NOx emission standard limit (especially for the newly introduced Euro 5 technology). These observations raise concerns regarding the actual NOx emissions of modern vehicles and their impact on urban air-quality. The emission factors originally measured on the road are also compared to the corresponding COPERT average speed emission factors. In general, emissions of CO2, THC and CO correlate fairly well with COPERT, for all vehicles. In the case of NOx emissions, emission levels of the two tested Euro 5 diesel passenger cars are consistently higher in urban, rural, and highway driving compared to the corresponding COPERT emission factor. Thus, leading to the conclusion that more experimental data are necessary, especially for post-Euro 4 compliant diesel vehicles of different engine capacities particularly when it comes to NOx emissions from diesel vehicles.

Vehicles are tested in controlled and relatively narrow laboratory conditions to determine their official emission values and reference fuel consumption. However, on the road, ambient and driving conditions can vary over a wide range, sometimes causing emissions to be higher than those measured in the laboratory. For this reason, the European Commission has developed a complementary Real-Driving Emissions (RDE) test procedure using the Portable Emissions Measurement Systems (PEMS) to verify gaseous pollutant and particle number emissions during a wide range of normal operating conditions on the road. This paper presents the newly-adopted RDE test procedure, differentiating six steps: 1) vehicle selection, 2) vehicle preparation, 3) trip design, 4) trip execution, 5) trip verification, and 6) calculation of emissions. Of these steps, vehicle preparation and trip execution are described in greater detail. Examples of trip verification and the calculations of emissions are given.

Type approval is granted in the European Union to light-duty vehicles if these comply with emission limits during standardized emissions testing in the laboratory. Although applicable emission limits have become more stringent in past years, light-duty vehicles remain an important source of urban nitrogen oxides and carbon monoxide emissions. The persisting air quality problems suggest that standard emissions testing in the laboratory may not accurately capture the on-road emissions of light-duty vehicles. To address this hypothesis, we present the first comprehensive on-road emissions test of light-duty vehicles based on state-of-the-art Portable Emission Measurement Systems (PEMS). We find that nitrogen oxides emissions of gasoline vehicles as well as carbon monoxide and total hydrocarbon emissions of both diesel and gasoline vehicles generally stay below the respective emission limits. By contrast,However, Average nitrogen oxides emissions of diesel vehicles (0.93 ± 0.39 grams per kilometer [g/km]), including modern Euro 5 diesel vehicles (0.62 ± 0.19 g/km), exceed emission limits by 320 ± 90%. On-road carbon dioxide emissions surpass laboratory emission levels by 21 ± 9% and exceed the fleet-average emission target for passenger cars by 32 ± 20%. These findings suggest that the current emissions testing fails to accurately capture the on-road emissions of light-duty vehicles. Our research provides the empirical foundation for establishing a complementary emission test procedure for light-duty vehicles in Europe. This procedure that will be implemented together with more stringent Euro 6 emission limits in 2014. Both provisions should improve urban air quality and reinforce innovation and competitiveness of the automotive industry., JRC.F.9-Sustainable Transport (Ispra)

Emission inventories are used to quantify sources and identify trends in the emissions of air pollutants. They use vehicle-specific emission factors that are typically determined in the laboratory, through remote-sensing, vehicle chasing experiments and, more recently, on-board measurements with Portable Emission Measurement Systems (PEMS). Although PEMS is widely applied to measure gaseous pollutants, their application to Solid Particle Number (SPN) emissions is new. In this paper, we discuss the current status of determining SPN emission factors both on the chassis dynamometer in the laboratory and on the road using PEMS-SPN. First, we determine through dedicated tests in the laboratory the influence of the measurement equipment, ambient temperature, driving style, and cycle characteristics, and the extra mass of the PEMS equipment on the SPN emissions of vehicles. Afterward, we present the SPN emissions under type-approval conditions as well as on the road of two heavy-duty diesel vehicles equipped with Diesel Particulate Filter (DPF; one of them Euro VI), two light-duty diesel vehicles equipped with DPF, one light-duty vehicle equipped with a Port Fuel Injection engine (PFI), and seven Gasoline Direct Injection (GDI) passenger cars (two of them Euro 6). We find that cold-start and strong accelerations tend to substantially increase SPN emissions. The two heavy-duty vehicles showed on-road emissions around 2 × 1013 p/km (Euro V truck) and 6 × 1010 p/km (Euro VI truck), respectively. One of the DPF-equipped light-duty vehicles showed emissions of 8 × 1011 p/km, while the other one had one order of magnitude lower emissions. The PFI car had SPN emissions slightly higher than 1 × 1012 p/km. The on-road emissions of GDI passenger cars spanned approximately from 8 × 1011 p/km to 8 × 1012 p/km. For the cars not equipped with a DPF, the on-road SPN emissions remained within a factor of two of the laboratory results. This factor was on average around 0.8 for the Euro 6 and 1.6 for the Euro 5 GDIs. The DPF equipped vehicles showed a difference of almost one order of magnitude between laboratory and on-road tests due to the different DPF fill state and passive regeneration during the tests. The findings of this study can (i) help improving the inventories on SPN emissions and (ii) assist policy makers in designing effective test procedures for measuring the SPN emissions of vehicles under real-world driving conditions.

The performance of three Portable Emission Measurement Systems (PEMS) for Particulate Matter (PM) was assessed in our laboratory against reference instrumentation in engine dynamometer testing of five Heavy Duty Engines (HDEs) of different aftertreatment technologies. The candidate systems were designed around the minimum requirements of allowing a gravimetric determination of the total emitted PM mass and incorporating a real time particle sensor. All PEMS-PM systems were found to reproduce within ±30% the gravimetric PM results determined with reference measurement systems under non-regenerative operating conditions, at emission levels lying at and above the Euro VI limit of 10mg/kWh. The use of prolonged sampling times envisaged in In Service Conformity (ISC) testing (>120min) was found to be beneficial, as it reduced the limit of detection of the PEMS-PM instrumentation to 1-3mg/kWh (120min) from 3 to 9mg/kWh (30min). The real time aerosol instrumentation exhibited a much higher sensitivity, being capable of quantifying emission levels below the EURO VI particle number limit of 6×1011#/kWh. Some modifications were required though in two particle sensors that were based on diffusion charging, in order to avoid a disproportional increase in their responses in the presence of homogeneously nucleated particles. Passive regeneration of the particulate filter resulted in excessive emission of volatile PM but also large discrepancies between the PEMS-PM and reference systems. The accurate quantification of absolute emission levels of non-volatile PM from the real time sensors can assist in the identification of such excessive volatile PM fractions, to avoid properly working DPF systems to fail an ISC test., JRC.F.8-Sustainable Transport

The nitrogen dioxide (NO2) pollution in urban areas of Europe can be partially attributed to the increasing market penetration of diesel cars that show higher distance-specific nitrogen oxides (NOx) emissions than gasoline cars. The on-road NOx emissions of diesel cars, furthermore, appear to exceed substantially applicable emissions standards. This observation raises concerns that the introduction of more stringent Euro 6 emissions standards in 2014 may not adequately reduce the distance-specific on-road NOx emissions of new diesel cars. We address the existing concerns by analyzing the gaseous emissions of one novel Euro 6 diesel car and six Euro 4-5 diesel cars with Portable Emissions Measurement Systems (PEMS). We find that the average on-road NOx emissions of the Euro 6 car (0.21 ± 0.09 gram per kilometer [g/km]) are considerably lower than those of the Euro 4 cars (0.76 ± 0.12 g/km) and the Euro 5 cars (0.71 ± 0.30 g/km). The selective catalytic reduction (SCR) system of the Euro 6 diesel car is suitable to limit NOx emissions during real-world on-road driving. Still, all tested cars, including the Euro 6 diesel car, exceed their NOx emissions standards on the road by 260 ±130%. This finding suggests that the current type-approval procedure does not adequately capture the on-road NOx emissions of diesel cars. By introducing a complementary emissions test procedure that covers a wide range of normal operating conditions, the European legislative authorities can address this problem and ensure that Euro 6 will indeed deliver an adequate reduction in the NOx emissions of new diesel cars., JRC.F.8-Sustainable Transport

The origins of mires and the initiation of peat inception during the last 12 000 years has been widely interpreted in terms of macroclimatic change or land-use changes associated with human activities. One objective of our palaeoenvironnemental studies in the eastern Massif Central in France was to accurately date basal peat layers at a great number of sites. These radiocarbon dates of peat inception must then be confronted with palaeocological and archaeological data. Although radiocarbon dating is currently used to date peat initiation, various difficulties can be encountered when attempting to identify and sample the oldest basal layers in a mire, and these problems are rarely addressed. This paper proposes a methodology based on detailed investigation by means of stratigraphical, sedimentological and micromorphological analyses. Five mires were studied: 3 bogs, and 2 fens. As a main result we illustrated the great importance of micromorphological analysis. We also show that many radiocarbon dates are required to obtain accurate age estimations of the chronology of peat inception, precise enough to be confronted with other palaeoenvironmental data. L’apparition des tourbières au cours des 12000 dernières années est révélatrice de changements environnementaux importants, tant d’origine climatique que d’origine anthropique. Aussi, est-il fondamental, dans le but d’une reconstitution paléoenvironnementale, de pouvoir caler chronologiquement le démarrage de la turfigenèse sur un grand nombre de sites. La répartition dans le temps des dates obtenues peut ensuite être confrontée aux données géomorphologiques, paléoécologiques et archéologiques locales et régionales pour tenter de retracer l’évolution des paysages et des sociétés humaines qui les ont façonnés. Néanmoins, si la datation par le radiocarbone est l’outil le plus adapté au travail de calage chronologique des couches basales des tourbières, l’entreprise est complexe et pose un certain nombre de problèmes méthodologiques très rarement abordés dans la bibliographie. Une première difficulté est d’identifier le faciès qui, sur la stratigraphie, matérialise le démarrage de la turfigenèse. Il convient ensuite de déterminer le ou les secteurs de la tourbière où la tourbe a commencé à s’accumuler. Cet article propose une méthode d’échantillonnage des couches basales de tourbe fondée sur un travail minutieux de restitution des stratigraphies couplé à des analyses sédimentologiques et à des examens micromorphologiques. Cinq sites pilotes ont été retenus: trois tourbières bombées et deux tourbières basses. Parmi les résultats notables de l’étude, on insistera sur l’apport de l’analyse micromorphologique. Par ailleurs, le grand nombre de datations par le radiocarbone qui ont été réalisées a permis d’apprécier la précision que l’on est en droit d’attendre d’un tel travail de calage chronologique, une information déterminante avant d’entreprendre la confrontation avec les autres données paléoenvironnementales.