Contents lists available at ScienceDirect Transportation Research Part D journal homepage: www.elsevier.com/locate/trd Real-world gaseous and particle emissions of a Bi-fuel gasoline/ CNG Euro 6 passenger car A. Dimaratos, Z. Toumasatos, G. Triantafyllopoulos, A. Kontses, Z. Samaras ⁎ Laboratory of Applied Thermodynamics, Department of Mechanical Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece ARTICLE INFO Keywords: Real Driving Emissions (RDE) Portable Emissions Measurement System (PEMS) Euro 6 emission limits Compressed Natural Gas (CNG) ABSTRACT The objective of the present study is the assessment of the environmental impact of a bivalent (bi- fuel) vehicle, running either on gasoline or compressed natural gas (CNG). To that aim, a Euro 6 passenger car was tested under various real-world driving conditions. In order to cover the full range of conventional powertrains currently in the market, the tests were also repeated on a Euro 6 diesel passenger car. Both cars were driven in two routes, the first complying with the reg- ulation limits and the second going beyond them. Carbon monoxide (CO), nitrogen oxides (NO x ) and particle number (PN) emissions were recorded using a Portable Emissions Measurement System (PEMS). Apart from the aggregated emission levels, in g/km, the exact emission location along the route was also assessed. Natural gas proved beneficial for CO and PN emissions, the level of which always remained below the respective legislation limits. On the other hand, under the dynamic driving conditions with gasoline, the relevant limits were exceeded. Cold start, occurring at the beginning of the urban part, and motorway driving were identified as major contributors to total emissions, especially in gasoline mode. However, the application of natural gas was associated with a penalty in NO x emissions, which were significantly increased as compared to gasoline. Local peaks within the urban part were identified in CNG mode. In any case, the diesel vehicle was by far the highest NO x emitter. 1. Introduction For many years already, natural gas is used as energy source in household applications, mainly for heating, as well as in electricity production. Over the last decade, it is also considered a fuel in the transport sector, owing to its availability around the globe and its lower price compared to gasoline and diesel. On 2017, the worldwide available reserves were 193.5 trillion cubic meters (tcm), while the global consumption reached 3.67 tcm (BP, 2018). The major component of natural gas is methane (CH 4 ), usually found in concentrations above 85%, while the remaining part contains ethane (up to ~10%), propane (up to ~4%) and butane (up to ~1%); nitrogen (N 2 ) and carbon dioxide (CO 2 ) may be also detected (Karavalakis et al., 2016; Chen et al., 2019). However, its actual https://doi.org/10.1016/j.trd.2020.102307 Abbreviations: CF, Conformity Factor; CI, Compression Ignition; CNG, Compressed Natural Gas; CO, Carbon Monoxide; CO 2 , Carbon Dioxide; DPF, Diesel Particulate Filter; EEA, European Environmental Agency; EGR, Exhaust Gas Recirculation; FAME, Fatty Acid Methyl Ester; GDI, Gasoline Direct Injection; GHG, Greenhouse Gas; GPF, Gasoline Particulate Filter; LHV, Lower Heating Value; LNT, Lean NO x Trap; NO x , Nitrogen Oxides; NO 2 , Nitrogen Dioxide; NTE, Not-To-Exceed; OBD, On-Board Diagnostics; OEM, Original Equipment Manufacturer; PEMS, Portable Emissions Measurement System; PFI, Port Fuel Injection; RDE, Real Driving Emissions; RPA, Relative Positive Acceleration; SI, Spark Ignition; SPN, Solid Particle Number; TA, Type Approval; TWC, Three Way Catalyst ⁎ Corresponding author at: 3is Septemvriou str., Thessaloniki, PO Box 458, GR 54124, Greece. E-mail address: zisis@auth.gr (Z. Samaras). Transportation Research Part D 82 (2020) 102307 Available online 10 April 2020 1361-9209/ © 2020 Elsevier Ltd. All rights reserved. T