25 September 2012: The International Energy Agency’s (IEA) Implementing Agreement on Bioenergy (IEA Bioenergy) has published a new report, titled “Fuel and Technology Alternatives for Buses: Overall Energy Efficiency and Emission Performance,” which assesses the emissions reductions potential and fuel efficiency of various fuels for urban buses, and finds that replacing fossil fuels with efficient biofuels is most effective in reducing greenhouse gas (GHG) emission.

The project, running from 2009 to 2011, was carried out in cooperation with IEA’s Implementing Agreements on Alternative Motor Fuels and Bioenergy. The project contained four main parts: a well-to-tank (WTT) assessment of alternative fuel pathways, in which the total emissions of different fuels from raw material production to distribution were assessed; an assessment of bus end-use (tank-to-wheel, TTW) performance, in which emission and fuel consumption data were generated; a well-to-wheel (WTW) assessment, which combined WTT and TTW data; and a cost assessment of both direct and indirect costs.

The study finds, inter alia, that the most effective way to reduce regulated emissions is by replacing old vehicles with new ones, and that switching from fossil fuels to efficient biofuels is most effective for reducing GHG emissions. The study further finds that the impacts of the region of biofuel production, the raw material used and the technology choices made are crucial to the GHG impacts, and that hybridization or light-weighting (reducing weight) can reduce fuel consumption by 20–30%, but that otherwise improvements in fuel efficiency have not been significant. [Publication: Fuel and Technology Alternatives for Buses- Overall Energy Efficiency and Emission Performance]