Investigating the Impacts of Retrofitted CNG Vehicles on Air Pollutant Emissions in Tehran

Document Type: Original Research Paper


1 Department of Environment and Energy, Science and Research Branch, Islamic Azad University, Tehran, Iran

2 Energy Systems Engineering, Sharif University of Technology, Tehran, Iran


The present study was conducted to investigate the impacts of retrofitted CNG vehicles on air
pollutant emissions in Tehran over a 20 years period using available statistical data, precise automobile tests, data analysis, and LEAP Software. The obtained results revealed an increase in air pollutant emissions
including CO (equal to 1030.77 thousand tons), NOx (equal to 1030.77 thousand tons), THC (269.02 thousand tons) and CO2 (equal to 38.43 thousand tons) resulting from utilizing retrofitted CNG vehicles within the studied period. Considering the obtained results, if the current trend of producing retrofitted CNG vehicles continues, a total cost of 435 million USD will impose on the environment, annually. According to the emission test results, by implementing retrofitted CNG vehicles policy, a higher emission rate of dual-fuel vehicles will be expected compared to their petrol-fueled counterparts. This is due to poor quality of the policy implementation such the use of substandard conversion kits and old technology of retrofit technologies.