Air quality impacts of achieving U.S. renewable fuel mandates

KRISTINA WAGSTROM, Christopher Tessum, Jason Hill, Julian Marshall

University of Minnesota Twin Cities

     Abstract Number: 25
     Last modified: March 21, 2011

Abstract
The current US Renewable Fuel Standard (RFS2) requires increasing amounts of biofuel production through 2022. We use lifecycle assessment, air dispersion modeling, and health risk assessment to estimate air pollution and related health impacts of an additional 7.5 billion gallons of corn grain ethanol and 5 billion gallons of corn stover cellulosic ethanol.

Specifically, we considered three potential increases in ethanol volumes associated with moving from the Renewable Fuel Standard – Phase 1 (RFS1) to Phase 2 (RFS2): (i) a 5 billion gallon increase in cellulosic (corn stover-derived) ethanol, (ii) a 7.5 billion gallon increase in corn-derived ethanol, and (iii) a combination of the two (5 billion gallons of cellulosic ethanol plus 7.5 billion of corn ethanol). We use the CAMx reactive photochemical grid model to estimate the resulting changes in ozone and PM$_(2.5) concentrations, relative to a non-RFS scenario (i.e., relative to consuming an energy-equivalent amount of gasoline), for the entire United States using 2005 as a base year.

Preliminary results for February and August indicate that population-weighted PM$_(2.5) concentration increases are up to 189% higher for RFS than for the non-RFS scenario and nitrate PM$_(2.5) is 15%-150% higher. However, concentration impacts vary in space and time; in addition, predicted concentrations exhibit greater spatial variability for RFS than for the non-RFS scenario. Health risk assessment preliminary findings suggest that the RFS2 scenarios will annually yield up to 112 more deaths due to PM2.5, relative to an energy equivalent amount of gasoline.