On-road emissions of CO, CO2 and NOX from four wheeler and emission estimates for Delhi

This study presents the emission factor of gaseous pollutants (CO, CO₂, and NO_X) from on-road tailpipe measurement of 14 passenger cars of different types of fuel and vintage. The trolley equipped with stainless steel duct, vane probe velocity meter, flue gas analyzer, Nondispersive infra red (NDIR) CO₂ analyzer, temperature, and relative humidity (RH) sensors was connected to the vehicle using a towing system. Lower CO and higher NO_X emissions were observed from new diesel cars (post 2010) compared to old cars (post 2005), which implied that new technological advancement in diesel fueled passenger cars to reduce CO emission is a successful venture, however, the use of turbo charger in diesel cars to achieve high temperature combustion might have resulted in increased NO_X emissions. Based on the measured emission factors (g/kg), and fuel consumption (kg), the average and 95% confidence interval (CI) bound estimates of CO, CO₂, and NO_X from four wheeler (4W) in Delhi for the year 2012 were 15.7 (1.4–37.1) , 6234 (386–12,252) , and 30.4 (0.0–103) Gg/year, respectively. The contribution of diesel, gasoline and compressed natural gas (CNG) to total CO, CO₂ and NO_X emissions were 7:84:9, 50:48:2 and 58:41:1 respectively. The present work indicated that the age and the maintenance of vehicle both are important factors in emission assessment therefore, more systematic repetitive measurements covering wide range of vehicles of different age groups, engine capacity, and maintenance level is needed for refining the emission factors with CI.