Comparison of cost and environmental impact of diesel- and CNG-fuelled EEV buses

CE Delft was commissioned by MAN Bus & Truck BV to undertake a comparative analysis of the costs and emissions of MAN-manufactured diesel- and gas-fuelled city buses, both satisfying the EEV emission standard. The analysis was extended to include biodiesel and biogas as fuels, too. Both buses are based on the same vehicle platform (the MAN ‘Lion’s City’), so that any differences in cost and environmental impact are due entirely to the type of fuel used.

The general conclusion is that while the MAN-manufactured EEV-approved city buses running on diesel and gas do not differ significantly in their overall capital and operating costs, the gas-powered buses have a clear environmental edge, particularly in terms of NOx emissions. Fuelling the buses with 100% biodiesel and biogas, respectively, leads to comparable per-kilometre costs (‘total cost of ownership’), but in the case of biogas there is a far greater reduction in WTW greenhouse gas emissions than for biodiesel. These greater WTW greenhouse gas reductions translate to significantly lower external environmental costs for biogas compared with biodiesel.