Environmental and economic benefits of CNG conversion on three-wheelers in a developing city, Khulna, Bangladesh

Motorized vehicles have emerged as significant contributors to air pollution in cities around the world, particularly in developing countries where they constitute the primary source of pollution. To address this issue and improve air quality, the substitution of petroleum and diesel consumption with Compressed Natural Gas (CNG) has gained attention. For the first time, this study investigated the environmental and economic impacts of CNG conversion on three-wheelers. The top-down approach was employed to estimate pollutant emissions (CO₂, CO, SO₂, CH₄, NO₂, NMVOC, and PM₁₀) from the three-wheelers in Khulna City. For assessing the economic impacts, pollutant emission costs were estimated using the damage cost approach; vehicle operation and trip generation costs were also estimated. Findings reveal that CNG conversion leads to reduced vehicle operation costs and increased average daily travel length. Consequently, daily CO₂ emissions in Khulna City decreased by 32.27 tons, SO₂ by 45.87 kg, NMVOC by 20.12 kg, and PM₁₀ by 166.02 kg during 2019–2022 period. However, there was an increase in CO emissions of 3.69 tons/day, CH₄ of 370.62 kg/day, and NO₂ of 197.20 kg/day. This also contributed to the decline in pollutant emission costs by BDT 1.12 million per day (USD 4.8 million/year). The noise pollution inventory analysis shows the diesel-powered vehicle is the noisiest among three-wheelers. This comprehensive study directly contributes to the present interest in adopting CNG-fueled vehicles in both developed and developing nations. The study facilitates an integrated assessment of co-benefits by reducing air pollution and climate change strategies at the same time.