Carbon dioxide and methane emission rates from taxi vehicles in Thailand

Due to the expansion of urban areas have been increasing levels of greenhouse gas emissions from taxi and passenger cars that use natural gas for vehicles (NGV) and liquid petroleum gas (LPG) as alternative fuels . The objective of this study was to evaluate the CO2 and CH4 emission of NGV and LPG taxis with different times from their engine ages compared to those from passenger cars. The driving tests were conducted at three driving speed ranges in Bangkok, Thailand. No significant differences in the CO2 emission rates from taxis and passenger cars using either NGV or LPG (174.5-227.0 g/km) were found. However, NGV taxis emitted the highest CH4 at all driving speeds, with an average emission of 1.33 g/km, higher than that from the LPG taxis. Comparing between taxis and passenger cars, the NGV taxis emitted the highest of CO2 and CH4 (13.8 ton (CO2-eq)/y), followed by LPG taxis (12.5 ton (CO2-eq)/y). The results obtained in this study can be used to create a database that supports the decision-making on development projects and to control GHG emission in Thailand.