Modeling the Impacts of Diesel, Biodiesel and Diesel Ethanol Fuel Blends on Atmospheric Ozone and Carbonyl Concentrations

Lílian Lefol Nani Guarieiro (1), Linsey C. Marr (2), Antonio H. Miguel (4), JAILSON B DE ANDRADE (1,3).

(1) Universidade Federal da Bahia, Instituto de Química, 40170290, Salvador-BA, Brazil. (2) Virginia Tech, Department of Civil and Environmental Engineering, Blacksburg, VA, United States. (3) Centro Interdisciplinar de Energia e Ambiente – CIEnAm, Universidade Federal da Bahia, Canela, 40110-040, Salvador-BA, Brazil (4) Nanochemistry Laboratory, UCLA Institute of the Environment, Los Angeles, California (Currently at the Organic Analysis Section, Haagen-Smit Laboratory, California EPA - Air Resources Board, El Monte, California, USA)

     Abstract Number: 484
     Last modified: January 27, 2010

Abstract
Before adopting alternative fuels that offer the promise of more sustainable development, we must evaluate their potential impacts on human health, and climate change. Biofuels may help reduce our dependence on fossil fuels, while also lowering the emissions of certain primary and secondary air pollutants. Currently, studies regarding the impact of biofuels on air quality, human health and climate change are scarce at best. Primary and secondary carbonyl compounds are of particular interest because some are air toxics and may participate in initiation steps in atmospheric photochemical reactions that lead to the formation of other toxic compounds. So, this study examined the impact that the use of biofuels in diesel engines might have on ozone and other air toxics (formaldehyde, acetaldehyde and acrolein). The maximum incremental reactivity (MIR) scale and box modeling were used to predict ozone and aldehyde concentrations along Avenida Brasil, a major road located in the city of Rio de Janeiro, Brazil. Emission inventories were developed for fourteen different fuels used in diesel engines including: pure diesel, diesel with different percentages of biodiesel from residual oil (B2, B5, B10, B20, B50 and B75), pure biodiesel from residual oil, diesel/anhydrous ethanol– 90/10%, diesel/anhydrous ethanol /soybean biodiesel – 80/15/5%, diesel/ethanol ethanol /castor biodiesel – 80/15/5%, diesel/anhydrous ethanol/residual biodiesel – 80/15/5%, diesel/anhydrous ethanol/soybean oil – 90/7/3%, and diesel/anhydrous ethanol/castor oil – 90/7/3%. These fuel/blends were used as input to the MIR and OZIPR (with SAPRC07 chemistry) models. Although predicted ozone concentrations were slightly higher with biofuels compared to petroleum diesel, they did not exceed 60 ppbv. Thus, the use of these fuels are promising in terms of ozone formation because the resulting changes in ambient concentrations of ozone are not expected to result in exceedances of the national ambient air quality standard (80 ppbv at 25 °C). For aldehydes, the use of biofuels was associated with a small increase --until 30% using diesel/anhydrous ethanol/residual biodiesel – 80/15/5%-- in their predicted concentrations, except for acrolein. Biofuels have the potential to reduce ambient concentrations of certain pollutants but may also result in small increases in others, notably acrolein, one of the most toxic carbonyls.