In this analysis we assess the life cycle greenhouse gas (GHG) emissions of four types of vehicles which might play a role in achieving future emission reductions: vehicles using compressed natural gas (CNG), battery electric vehicles (BEVs), mild hybrid CNG vehicles and range extended BEVs. Our analysis covers the manufacturing processes of these vehicles and their use as a city taxi in Singapore. We also consider upstream emissions from fuel and electricity production.
All necessary parameters are derived from an intensive literature review and the model for calculating the life cycle emissions is presented. The influence of data uncertainties is analyzed by parameter variations within different scenarios.
The calculation results are found to be quite robust: The BEV and the mild hybrid CNG vehicle similarly show very low GHG emissions within all scenarios whereas the pure CNG vehicle always ranks the worst.
In an additional scenario we also assessed the influence of an improved electricity generation with lower emissions in the future. In this the results of the BEV and the range extended BEV were significantly improved compared to the previous baseline calculations.
We conclude that the introduction of BEVs is an effective measure to reduce GHG emissions in the transport sector of the future. However, mild hybrid CNG vehicles seem to be a very practicable solution for mobility with less GHG emissions today and in the nearer future.