Comparative environmental assessment of Athens urban buses—Diesel, CNG and biofuel powered

• A comparative environmental assessment of urban buses was performed for the city of Athens.
• CO2 emissions in 2009 reached 125,467 t (diesel buses) and 24,811 t (CNG buses).
• Biofuels will be key to lower transport emissions. Critical factors are identified.
• Specific policy recommendations are made for attaining a sustainable urban mobility.

Greenhouse gases (GHGs) emitted by road transport vehicles as a direct result of fossil fuel combustion and other environmental pollutants released throughout the life cycle of petroleum based fuels, encourage a shift towards alternative transport fuels. Within this frame, an environmental assessment was performed so as to evaluate the environmental implications of alternative fuels (natural gas and biofuels) penetration in the city buses of the city of Athens. The results are evaluated in terms of CO2, CO, HC, PM and NOx emissions. The findings show that CO2 emissions are significantly reduced in CNG buses compared to diesel powered buses. CO2 emissions can also be reduced by 7.85% in B10 blends and 78.45% in B100 blends, compared to diesel. The environmental assessment can be considered as a basis so as to investigate the viability of replacement of petroleum- based diesel with natural gas and biofuels in city transport buses. Concepts for sustainable bus transportation can be incorporated using the methodology defined in this study, in order to promote a sustainable transportation system and mitigate the climate change.