Ethanol – public transport’s future?

Stockholm Public Transport (SL) has used ethanol buses (running on E95) since 1989. Our ethanol fleet today consists of approximately 250 ethanol buses and we plan to extend the fleet with some additional 120-130 buses in 2005 and 2006. Our main goal is to have 25 per cent of our 1,800 buses running on renewable fuels at the end of 2006. SL also has buses running on biogas and hydrogen.

Our long-term goal is to have a bus fleet comprised of 100% renewable fuel vehicles by 2030. SL has spent many years studying and testing the different options for meeting the future environmental demands on public transport (from all the varieties of renewable options to the different emission cleaning equipment available). Our conclusion at the moment is that biogas and ethanol are the most viable and economical ways to tackle both local and global emissions. Biogas however, is in very short supply and can only be used for a limited number of buses.

The main reasons for ethanol being our first choice for city traffic are the following:

• Ethanol buses are a standard solution today
• We can utilise existing and well-functioning technology that we have experience of for more than 15 years
• Ethanol is a liquid fuel which simplifies infrastructure issues as compared to e.g. gaseous fuels
• Excellent emission performance: both Greenhouse gases and PM and NOx
• The large volume potential of ethanol
• A reduced dependency on oil

Low local and global emissions

An emission test recently carried out by STT/Emtec and Professor Karl-Erik Egerbäck (‘A clean ethanol fuelled compression ignition bus engine; 2004’) shows that today’s ethanol engine (Scania 9 litre), if equipped with existing emission reducing equipment, will have local emissions (NOx and PM) significantly lower than the Euro 5 and EEV (Enhanced Environmentally Friendly Vehicle) standard. The renewable ethanol also reduces CO2 by 70-90%, which is a major bonus.

Infrastructure and the ethanol bus

Three depots in Stockholm have an ethanol infrastructure and more are under construction. The buses use a standard Scania 9 litre diesel engine (in-line 6-cylinder, 230 hp), with some minor adaptations. The ethanol buses have a performance and purchase price comparable with diesel buses. The bus model is relatively old – it was developed in the 1980s and is only available for sale until 2006. One of the objectives of the Ethanol Bus Buyers’ Consortium is to encourage more ethanol bus producers on the market, in an attempt to speed up the process of making the next generation of ethanol engines.

Economy

The economy of the ethanol bus is somewhat higher compared to a diesel bus – the maintenance cost is higher as ethanol is a dry fuel. The extra maintenance for ethanol buses costs approximately €6,000 per year and bus for SL. The full operating cost/km is dependent on the taxation of ethanol. Fuel ethanol is exempt from tax in Sweden, making the operating cost/km approximately only 2-3% higher compared to diesel. With the rapidly rising diesel price however, the break-even point for ethanol cost/km as compared to diesel cost/km is not very far away. A larger group of buyers would most likely reduce the costs for fuel and buses even further.

Ethanol Bus Buyers’ Consortium and the future

As discussed above, the main goal of the Consortium project is to establish a functioning market for ethanol buses – i.e. at least two suppliers of ethanol buses. The strategy is to carry out a bus demonstration project in interested cities in two stages.

The first is to create a demonstration with 5-20 ethanol buses. The demonstration would include a fuel station for E95 at the bus garage, training of the drivers as well as the maintenance personnel. The demonstration project will give the cities experience of the fuel, fuel station, the ethanol engine, of driving and the maintenance. The attitudes of passengers could also be evaluated.

In the next step an Ethanol Bus Buyers’ Consortium will be formed by the cities that are satisfied with the experiences from the demonstrations and an international procurement process of a large volume of next generation’s ethanol buses will be carried out.

The Consortium is a part of the BEST project, funded by the EU. The cities of Stockholm, the Biofuel region (a cluster of cities in the north of Sweden), Madrid, Rotterdam, La Spezia and Nanyang are participating in the project.