Determinants of PM and GHG emissions from natural gas-fueled auto-rickshaws in Delhi

Auto-rickshaws are important for-hire transport in many Asian cities. A survey conducted in Delhi, India of natural gas-fueled auto-rickshaws to determine activity factors, fuel consumption and air emissions used an observational inspection for oil residue in the tailpipe and visible smoke at engine start-up to classify vehicles as low- or high-PM emitters; this method was calibrated using chassis-dynamometer PM measurements. Delhi auto-rickshaws were found to travel approximately 150 km daily. Auto-rickshaws with 2-stroke engines had about 20% higher fuel consumption and CO2 emissions, and a much higher likelihood of being categorized as high-PM emitters, than those with 4-stroke engines. Within the group of 4-stroke vehicles, age was a highly significant predictor with older model years having a higher likelihood of being high-PM emitters. The results suggest that the observational procedure for visible smoke and oil could be used to rapidly identify potential PM “super-emitters” for further testing.

Research highlights
► Natural gas auto-rickshaws with 2-stroke engines in Delhi, India have 20% higher fuel consumption than 4-strokes.
► 2-Stroke auto-rickshaws in Delhi are more likely to be identified as high-PM emitters, even when powered by compressed natural gas.
► 4-Stroke auto-rickshaws emit less PM and greenhouse gas emissions than 2-stroke auto-rickshaws.