Bio-Ethanol in public transport: an integrated approach to evaluate the impact of climate change policies in urban areas

Mitigation measures to reduce greenhouse gas emissions may have adverse effects in the air quality of the urban environment. The use of bioethanol fuelled vehicles is increasing worldwide and may create new undesired pollution effects. Different measurement campaigns were performed in the Biebus project to contribute to the understanding of the consequences associated with the use of bioethanol blended fuel (E95). Ambient screening measurements of NO2, O3, acetic acid, formaldehyde and acetaldehyde were performed at different urban locations, exposed and not exposed to the circulation of bioethanol buses. In addition, volatile organic compounds were measured at the exhaust pipe of a bioethanol fuelled bus, both under idling conditions (carbonyls; DNPH cartridge) and under on-road driving conditions applying online monitoring (PTR-TOF). Higher ambient acetaldehyde values were measured at locations exposed to bioethanol fuelled buses than at locations not exposed, and very high acetaldehyde, formaldehyde and acetic acid levels were measured from the exhaust pipe during driving conditions, and modelled at close distance to the bioethanol bus. Human exposure to high concentration of acetaldehyde and formaldehyde is expected, and it may involve a significantly increased chance in developing cancer. The high concentration of acetic acid will involve odour annoyance and significant material degradation or corrosion. Additionally, emission and air dispersion modelling of acetaldehyde in the city of Oslo and associated with the circulation of bioethanol vehicles was carried out. Two scenarios of bioethanol implementation, both realistic and hypothetical, have been considered under winter conditions; 1) realistic baseline scenario, which corresponds to the current situation where one bus line is running with bioethanol (E95; 95% ethanol - 5% petrol) among petrol and diesel vehicles; and 2) a hypothetical scenario characterized by a full implementation of high-blend bioethanol (i.e. E85) as fuel for transportation, and thus an entire bioethanol fleet. The results indicate that a full implementation of bioethanol will have an impact on urban air quality due to direct emissions of acetaldehyde. Acetaldehyde emissions are estimated to increase by 233% and concentration levels increase up to 650% with regard to the baseline.

The implementation of climate change policies as mitigation measures against greenhouse gas (GHG) emissions may create complex changes in the atmosphere. Particular sectors such as transport have been affected by abatement actions, and the measures have i ncluded moving from fossil based energy to increased use of bio-fuels. This, however, may create new environmental challenges. While the GHG emissions will be reduced, emissions of other compounds may increase. An example is the use of bio-ethanol for tra nsportation which is increasing worldwide. However, further research in needed as high emissions of harmful organic compounds such as acetaldehyde and formaldehyde have been suggested in several studies. Oslo constitutes an interesting case-study to evalu ate the effects of emissions from vehicles running on alternative fuels as several buses are currently running with bio-ethanol. The strong smell of acetic acid has already been noted as a negative side effect, and indicates possible implications of bio-f uel combustion on urban air quality. In order to add light and contribute to the understanding of emissions from bio-ethanol, an innovative measurement campaign will be carried out in Oslo as case-study and specific organic and inorganic compounds will be measured. In addition, the improvement of the current air dispersion modelling tools and the development of new innovative modelling techniques will be performed in the BieBus project. As well as concentrations, the dispersion models will be adapted to p rovide estimates of odour annoyance levels associated with the bio-ethanol combustion. BieBus project will evaluate the implementation of an integrated assessment tool for the evaluation of alternative fuels in transport via air pollution measurements, di spersion modelling and cost analysis. The use of a model framework will be assessed as a strategic tool and the limitations will be evaluated, as will the opportunities for enhancing the model.