Statistical analysis of the emission characteristics of in-use CNG vehicles in Dhaka city

Abstract

Dhaka, the capital of Bangladesh, is the center of all administrative, economic and cultural activities. The city has now a population of more than 12 million in the area of 2,000 sq. km. According to Bangladesh Road Transport Authority (BRTA), there are around 4 lakh-motorized vehicles operating in Dhaka city. Vehicle emission in Dhaka city is Increasing day by day with the increase of motor vehicle thus polluting the environment. It has been recognized that motor vehicles play the leading role in the problem of urban air pollution. Road transportation has most adversely affected the air quality in Dhaka City. The existing fleet of 4 lakh molor vehicles in Dhaka contributes nearly 70% of the total air pollution load. To improve the air quality in Dhaka various measures viz. Improvement of engine technology, fuel quality, use of exhaust treatment devices, use of Compressed Natural Gas (CNG) etc. have been adopted in the recent years by the Government. The CNG vehicles have been assumed as non-polluting vehicles, hence no certification was required until recently for tail-pipe emissions, which otherwise is mandatory for all other vehicles. To understand how these inuse CNG vehicles compared against their petrol-driven counterparts, this study is undertaken in Dhaka city. The tailpipe CO and HC emission characteristics of CNG vehicles were analyzed and compared against the emiSSion characteristics of similar vehicle categories earlier using petrol as fuel. The emission levels were compared against the legislated tailpipe CO emission standards of 4.5% and 3% (by volume) for both the CNG three and four wheelers. The comparison has revealed notable reduction in CO and HC emissions from CNG driven vehicles, especially from three wheelers. In this regard, more research is necessary to find out the right way to reduce the vehicle emission to the minimum level. As Ihe number of CNG vehicles and CNG conversion workshops are increasing day-by-day, there is a pressing need to initiate the process of certification and generation of database for CNG driven vehicles, It will in one hand, provide the information regarding effectiveness of CNG as transport fuel on the other hand, it will help to improve the CNG technology continuously 10reduce vehicle emission,