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Swedish experiences from low emission city buses : Impact on health and environment Ahlvik, Peter JE

By: Ahlvik, Peter JEPublication details: Stockholm Ecotraffic ERD3, [2001?]Description: 39 sSubject(s): Sweden | Bus | Emission control | Alternative energy | Diesel engine | Fuel | Variability | Impact study | Emission | Health | Test | Particle | 15 | 93Online resources: Publikation/Publication Abstract: Several field trials on city buses running on alternative fuels have been conducted in Sweden during the last decade. Reformulated diesel fuel and after treatment devices are measures that have been taken on diesel fuelled buses to reduce the emissions. The primary scope of this paper was to compare the impact on environment and health from various fuels and technology for low emission buses. By using available emission test data, emission factors (regulated and unregulated) have been established for each option. In the comparison between buses and cars, corrections have been made for climate, deterioration and driving pattern. The impact from the emission components on health and environment has been calculated using weighting factors for each compound. Acidification, eutrophication, ozone forming potential, cancer risk, greenhouse gases and several other effects have been evaluated. The analysis showed considerable improvement for the diesel buses by reformulating the diesel fuel and by fitting after treatment devices. Particulate emissions and its effects are probably the most severe emission component from the diesel engines. Particulate filters are the only commercially available solution to that problem today. The NOX emissions can be reduced by about 50 per cent by using an EGR system. Some of the alternative fuelled buses had a positive impact regarding several of the effects investigated, e.g. acidification and local NO2 emissions. In other cases (e.g. ozone forming potential), the difference between the best options was small. The cancer risk index is largely dependent on the unit risk factors, which are not fully developed yet, but the overall result in this case did not vary much between the risk factors evaluated. Clean diesel fuel with a particulate trap and CNG/biogas were the options with the lowest cancer risk index. The impact on the greenhouse gas emissions was the most significant advantage for the biofuels. The comparison between gasoline fuelled cars and buses showed an environmental and health advantage for the buses in all aspects but NOX emissions and acidification. The significant impact of cold starts on cars was the major cause of the outcome of this comparison. It is expected that future development on engines and after treatment devices will diminish the advantage of the alternative fuels in city buses regarding many of the effects. On the contrary, the impact on greenhouse gases from some biofuel options will be more pronounced in the future.
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Several field trials on city buses running on alternative fuels have been conducted in Sweden during the last decade. Reformulated diesel fuel and after treatment devices are measures that have been taken on diesel fuelled buses to reduce the emissions. The primary scope of this paper was to compare the impact on environment and health from various fuels and technology for low emission buses. By using available emission test data, emission factors (regulated and unregulated) have been established for each option. In the comparison between buses and cars, corrections have been made for climate, deterioration and driving pattern. The impact from the emission components on health and environment has been calculated using weighting factors for each compound. Acidification, eutrophication, ozone forming potential, cancer risk, greenhouse gases and several other effects have been evaluated. The analysis showed considerable improvement for the diesel buses by reformulating the diesel fuel and by fitting after treatment devices. Particulate emissions and its effects are probably the most severe emission component from the diesel engines. Particulate filters are the only commercially available solution to that problem today. The NOX emissions can be reduced by about 50 per cent by using an EGR system. Some of the alternative fuelled buses had a positive impact regarding several of the effects investigated, e.g. acidification and local NO2 emissions. In other cases (e.g. ozone forming potential), the difference between the best options was small. The cancer risk index is largely dependent on the unit risk factors, which are not fully developed yet, but the overall result in this case did not vary much between the risk factors evaluated. Clean diesel fuel with a particulate trap and CNG/biogas were the options with the lowest cancer risk index. The impact on the greenhouse gas emissions was the most significant advantage for the biofuels. The comparison between gasoline fuelled cars and buses showed an environmental and health advantage for the buses in all aspects but NOX emissions and acidification. The significant impact of cold starts on cars was the major cause of the outcome of this comparison. It is expected that future development on engines and after treatment devices will diminish the advantage of the alternative fuels in city buses regarding many of the effects. On the contrary, the impact on greenhouse gases from some biofuel options will be more pronounced in the future.

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