Variability in the Primary Emissions and Secondary Gas and Particle Formation from Vehicles Using Bioethanol Mixtures

Bioethanol for use in vehicles is becoming a substantial part of global energy infrastructure because it is renewable and some emissions are reduced. CO emissions and total hydrocarbons (THC) are reduced, but there is still controversy regarding emissions of NOx, aldehydes, and ethanol. The amount of emissions depends on the ethanol content, but it also may depend on the engine quality and ethanol origin. Thus, a photochemical chamber was used to study secondary gas and aerosol formation from two flex-fueled vehicles using different ethanol blends in gasoline. One vehicle and the fuel used were made in the United States, and the others were made in Brazil. Primary emissions of THC, CO, CO2, and nonmethane hydrocarbons from both vehicles decreased as the amount of ethanol in gasoline increased. NOxemissions in the US and Brazilian cars decreased with ethanol content. However, emissions of THC, CO, and NOxfrom the Brazilian car were markedly higher than those from the US car, showing high variability between vehicle technologies. Results indicate that using higher ethanol blends may have a positive impact on air quality.