Atmospheric Environment, vol. 42, issue 19 (2008) pp. 4498-4516
The results of two recent vehicle emission studies are described in this paper, along with a statistical analysis of the changes in tailpipe emissions due to the use of ethanol that includes the results from these two studies in combination with results from other literature reports. The first study evaluates the effect of two low blend ethanol gasolines (E10, E20) on tailpipe and evaporative emissions from three multi-port fuel injection vehicles and one gasoline direct injection vehicle at two different test temperatures. The second study evaluates the differences in tailpipe emissions and fuel consumptions of paired flexible fuel and conventional gasoline vehicles operating on California RFG Phase 2 and/or E85 fuels at 20 ??C. The vehicles were tested over the four-phase FTP or UDDS and US06 driving cycles. Tailpipe emissions were characterized for criteria pollutants (CO, NOX, NMHC, NMOG), greenhouse gases (CO2, CH4, N2O), and a suite of unregulated emissions including important air toxics (benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein), and ozone reactivity. In the low blend ethanol study, evaporative emissions were quantified and characterized for NMHC. While contradicting, results can be seen among the various literature reports and with these two new studies, the statistical analyses of the aggregated data offers much clearer pictures of the changes in tailpipe emissions that may be expected using either low blend ethanol gasoline (E10) or E85. The results of the statistical analysis suggest that the use of E10 results in statistically significant decreases in CO emissions (-16%); statistically significant increases in emissions of NMHC (9%), NMOG (14%), acetaldehyde (108%), 1,3-butadiene (16%), and benzene (15%); and no statistically significant changes in NOX, CO2, CH4, N2O or formaldehyde emissions. The statistical analysis suggests that the use of E85 results in statistically significant decreases in emissions of NOX (-45%), NMHC (-48%), 1,3-butadiene (-77%), and benzene (-76%); statistically significant increases in emissions of formaldehyde (73%) and acetaldehyde (2540%), and no statistically significant change in CO, CO2, and NMOG emissions. Crown Copyright ?? 2008.
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