Comparisons of air quality impacts of fleet electrification and increased use of biofuels

The air quality impacts of the partial electrification of the transportation fleet and the use of biofuels (E85) were modeled for the Austin Metropolitan Statistical Area, based on a 2030 vision of regional development. Changes in ozone precursor emissions and predicted ozone, carbon monoxide and aldehyde concentrations were estimated for multiple electrification and biofuel scenarios. Maximum changes in hourly ozone concentration from the use of plug-in hybrid electric vehicles (PHEVs) for 17% of the vehicle miles traveled ranged from -8.5 to 2.2 ppb, relative to a base case with no electrification and minimal biofuel use, depending on time of day and location. Differences in daily maximum 1 h ozone concentration ranged from -2.3 to 0.004 ppb. Replacement of all gasoline fuels with E85 had a smaller effect than PHEVs on maximum daily ozone concentrations. Maximum ozone changes for this scenario ranged from -2.1 to 2.8 ppb and the difference in daily maximum 1 h ozone concentrations ranged from -1.53 to 0 ppb relative to the base case. The smaller improvements in maximum ozone concentrations associated with extensive (100%) use of biofuels, compared to a smaller (17%) penetration of PHEVs, suggests that higher levels of PHEV penetration may lead to even greater improvements; however, the higher penetration would require expansion of the electrical grid capacity. The air quality impacts of the PHEVs would then depend on the emissions associated with the added generation.