Biofuel reduces local emissions efficiently
The three-year biofuel trial conducted on Helsinki region bus services has been completed. According to the results obtained, the impacts of biofuel on local emissions are significant. Particle emissions decreased on average by 30%, while nitrogen oxide emissions were cut by 10%. Also the after treatment of exhaust gases went without problems. The impacts of the fuel were examined both at VTT's (Finnish Technical Research Centre for Finland) laboratory and with an extensive field test. The project participants included HSL, Neste Oil, Proventia, which specializes in exhaust gas purification, and bus operators operating in the Helsinki region. The project is part of the BioRefine research program of the Finnish Funding Agency for Technology and Innovation (TEKES).
The biofuel used in the trial is NExBTL diesel developed by Neste Oil. The fuel is produced from renewable raw materials such as vegetable oils and waste animal fat from the food industry. NExBTL diesel can be used either as such or mixed with regular diesel. The fuel is suitable for all types of bus fleet regardless of their age.
Because the use of the fuel does not require new technology it can be used also in old buses that usually run during peak hours and whose emission levels are higher than those of new buses. The trial proved that NExBTL fuel provides excellent performance also in severe winter conditions. The properties of the fuel also support the functioning of different exhaust gas after treatment techniques. “At the moment biofuels and retrofitting buses with catalysts are practically the only feasible ways of reducing emissions from old buses," says Research Professor Nils-Olof Nylynd from VTT.
The biofuel produced from renewable raw materials also improves greenhouse gas balance. Greenhouse gas emissions over the life cycle of the fuel are 50% lower than those of a fossil diesel fuel.
Exceptionally extensive field testing
The trial conducted in the Helsinki region is the largest field test of a biofuel produced from renewable raw materials worldwide. The trial included around 300 buses, which is just over one fifth of the buses used on bus services procured by HSL. The buses included in the trial were driven a total of over 50 million kilometres. In the first stage of the project the buses included in the trial were run on a 30 percent blend of biofuel and from 2008 onwards a 100 percent biofuel was used in some of the buses. The greatest impacts on emissions are achieved with a 100 percent biofuel. In addition to particle and nitrogen oxide emissions also noxious polycyclic aromatic hydrocarbon (PAH) emissions decreased.
One of the key aims of the project was to support the Helsinki Metropolitan Area Climate Strategy, which includes the target of reducing traffic-related greenhouse gas emissions by one fifth by 2030. HSL promotes the introduction of biofuels and after treatment devices through its principles for the competitive tendering of bus services. Fuel choices and after treatment devices provide a faster means of affecting local and greenhouse gas emissions than fleet renewal.