Sunday, February 19, 2012
Exhibit Hall A-B1 (VCC West Building)
The current U.S. Renewable Fuel Standard - Phase 2 requires increasing amounts of biofuel production through 2022. We use life cycle assessment, air dispersion modeling, and health risk assessment to estimate air pollution related health impacts associated with the production and use of an additional 7.5 billion gallons per year (bgy) of corn grain ethanol and 5 bgy of corn stover cellulosic ethanol. We consider three potential increases in ethanol volumes associated with moving from the Renewable Fuel Standard – Phase 1 (RFS1) to Phase 2 (RFS2): (i) a 5 bgy increase in cellulosic (corn stover-derived) ethanol, (ii) a 7.5 bgy increase in corn-derived ethanol, and (iii) a combination of the two (5 bgy of cellulosic ethanol plus 7.5 bgy of corn ethanol). We use the GREET life cycle model to estimate the changes in pollutant emissions relevant to ozone and particulate matter (PM) chemistry including volatile organic compounds, NOx, SO2, NH3, and PM. We then allocate these emissions changes over space and time. We use the CAMx reactive photochemical grid model to estimate the resulting changes in ozone and PM2.5 concentrations, relative to a non-RFS scenario (i.e., relative to consuming an energy-equivalent amount of gasoline), for the entire United States. We then estimate health impacts using linear dosage response functions. Our analysis of pollutant concentration changes in August indicate decreases below the baseline in ozone over the Midwest for the ethanol scenarios associated with increased NOx emissions and the non-linear nature of ozone formation chemistry. We have also found increases in PM2.5 concentrations associated with ethanol use over the Midwest resulting primarily from fertilizer use and ethanol feedstock processing. We find population-weighted PM2.5 concentration increases that are approximately 35% higher for RFS than for non-RFS scenarios. However, concentration impacts vary in space and time; in addition, predicted concentrations exhibit greater spatial variability for RFS than for non-RFS scenarios. Health risk assessment findings suggest that the RFS2 scenarios will yield up to 260 more deaths annually due to PM2.5 and ozone relative to an energy equivalent amount of gasoline. We have found that the air quality changes associated with both ethanol and gasoline production and use are highly spatially dependent. Our findings also suggest that ethanol will have higher health costs from air pollution than using an energy equivalent amount of gasoline.