Fuel and Technology Alternatives for Buses
(VTT Technology) … So far, conventional diesel buses and conventional diesel fuel have dominated the market, with some contribution from natural gas buses. Now we are in a situation in which the technology options are increasing rapidly. This goes for vehicle technology as well as fuels. Advanced diesel vehicles producing very low emissions are entering the market, and hybrids are becoming commercially available. On the fuel side, various biofuels are offered as blending components or to be used as such. Natural gas and biogas can still deliver emission benefits over diesel. Additive treated ethanol is available for captive fleets such as city buses, and DME has progressed into the field testing phase. The diversification in technology increases the challenges in decision making.
In 2009–2011, a comprehensive project on urban buses was carried out in cooperation between IEA’s Implementing Agreements on Alternative Motor Fuels (AMF) and Bioenergy, with input from additional IEA Implementing Agreements. The objective of the project
was to generate unbiased and solid data for use by policy- and decision-makers responsible for public transport using buses. Within AMF, this was the largest collaborative project so far.
The project comprised four major parts: well-to-tank (WTT) assessment of alternative fuel pathways, assessment of bus end-use (tank-to-wheel, TTW) performance, combining WTT and TTW data into well-to-wheel (WTW) data and cost assessment, including indirect
as well as direct costs.
Experts at Argonne National Laboratory, Natural Resources Canada and VTT worked on the WTT part. In the WTT assessment, the total emissions of different fuels were assessed from the raw material production until the distribution of the final product. Argonne
National Laboratory calculated the WTT emissions of 5 fossil fuels and 13 biofuels by using the GREET model. Natural Resources Canada calculated the WTT emissions of 6 fossil fuels and 12 biofuels with the GHGenius model. VTT reported the WTT emissions of 4 fossil fuels and 19 biofuels according to the RED methodology, published in the Renewable Energy Directive (2009/28/EC) of the European Union (EU). The fuel chains studied are presented in Table 2.1. In co-operation, the institutes also made a comparison of the different calculation models and methodologies used for the WTT assessment, to better understand their differences and similarities. All these methods are based on life cycle assessment (LCA) approach, which is a commonly used tool for environmental impact assessment of different products. The framework of LCA is presented in two ISO standards, ISO 14040 and ISO 14044. READ MORE