An assessment of regulated emissions and CO2 emissions from a European light-duty CNG-fueled vehicle in the context of Euro 6 emissions regulations

Natural gas is one of the most promising alternative fuels to meet the upcoming stringent Euro 6 emissions regulations in the European Union, as well as the planned reductions in CO2 emissions. For spark-ignition engines, bi-fuel fuelling equipment is widely available and engine conversion technology for European automobiles is well established, thereby facilitating usage of natural gas in its compressed form (CNG). In light of the promising characteristics and increasing usage of natural gas as a vehicular fuel, this study investigates emissions from a passenger car featuring a spark-ignition engine capable of running on both CNG and standard gasoline. Results from emissions testing of the vehicle on a chassis dynamometer are presented and discussed in the context of the Euro 6 emissions requirements. The test vehicle featured a multipoint gas injection system and was an unmodified, commercially available European vehicle meeting the Euro 5 standard. The results indicated that when fueled with CNG, such a vehicle can comfortably meet Euro 6 emissions limits, with certain differences observed in the emissions according to the fuel type used. Furthermore, when running on CNG the vehicle was observed to emit considerably less carbon dioxide than when fueled with gasoline, with the reduction closely agreeing with the results of other studies.