Comparative emission analysis of gasoline and CNG from gasoline/CNG Bi-fuel vehicles

Tailpipe emission tests of gasoline/CNG bi-fuel vehicles were performed on a chassis dynamometer according to NEDC (New European Driving Cycle). The experimental results showed that when cars were fueled with CNG, CO and CO₂ emissions were reduced by 27.25% and 16.35% respectively and THC emissions were increased by 36.12% compared to those with gasoline. And NO_x emissions from CNG were 2.42 times of those from gasoline. In comparison, aldehyde and ketone emissions from CNG and gasoline were almost the same, in fact, aldehyde and ketone emissions from CNG were only 2.29% less than those from gasoline. Methanal was the main emission of aldehyde and ketone emissions. The VOCs and BTEX emissions from CNG were 42.02% and 42.54% less than those from gasoline, respectively.