Abstract
According to directives 2003/30/EC and 2009/28/EC of the European Parliament and the Council, Member States should promote the use of biofuel. Consequently, since 2011 all fuels on the market used for transport purpose must contain a fraction of 5.75% renewable energy sources. Ethanol in gasoline is a promising solution to reach this objective. In addition to decrease the dependence on fossil fuel, ethanol contributes to reducing air pollutant emissions during combustion (carbon monoxide and total hydrocarbons), and has a positive effect on greenhouse gas emissions. These considerations rely on numerous emission studies performed in standard conditions (20–30 °C), however, very few emission data are available for cold ambient temperatures, as they prevail in winter times in e.g., Northern Europe. This paper presents a chassis dynamometer study examining the effect of ethanol (E75–E85) versus gasoline (E5) at standard and low ambient temperatures (22 °C and −7 °C, respectively). Emissions of modern passenger cars complying with the latest European standards (Euro4 and Euro5a) were recorded over the New European Driving Cycle (NEDC) and the Common Artemis Driving Cycle (CADC). Unregulated compounds such as methane, ammonia, and small chain hydrocarbons were monitored by an online Fourier Transformed Infra-Red spectrometer. In addition, a number of ozone precursors (carbonyls and volatile organic hydrocarbons) were collected and analyzed offline by liquid and gas chromatography in order to evaluate the ozone formation potential (OFP) of the exhaust. Results showed higher unregulated emissions at −7 °C than at 22 °C, regardless of the ethanol content in the fuel blend. More carbonyls were associated with oxygenated fuel, and acetaldehyde emissions were found particularly enhanced at −7 °C with E75. In addition, elevated methane emission was measured at low ambient temperature when ethanol fuel was used. Moreover, the OFP of the exhaust gas at −7 °C increased with the amount of ethanol in gasoline when the cold start excess emissions were included. However, regardless of the ambient temperature, the ammonia and toluene emissions associated to E75–E85 were lower than with E5.