A Spatially and Temporally Explicit Life Cycle Inventory of Air Pollutants from Gasoline and Ethanol in the United States

The environmental health impacts of transportation depend
in part
on where and when emissions occur during fuel production and combustion.
Here we describe spatially and temporally explicit life cycle inventories
(LCI) of air pollutants from gasoline, ethanol derived from corn grain,
and ethanol from corn stover. Previous modeling for the U.S. by Argonne
National Laboratory (GREET: Greenhouse Gases, Regulated Emissions,
and Energy Use in Transportation) suggested that life cycle emissions
are generally higher for ethanol from corn grain or corn stover than
for gasoline. Our results show that for ethanol, emissions are concentrated
in the Midwestern “Corn Belt”. We find that life cycle
emissions from ethanol exhibit different temporal patterns than from
gasoline, reflecting seasonal aspects of farming activities. Enhanced
chemical speciation beyond current GREET model capabilities is also
described. Life cycle fine particulate matter emissions are higher
for ethanol from corn grain than for ethanol from corn stover; for
black carbon, the reverse holds. Overall, our results add to existing
state-of-the-science transportation fuel LCI by providing spatial
and temporal disaggregation and enhanced chemical speciation, thereby
offering greater understanding of the impacts of transportation fuels
on human health and opening the door to advanced air dispersion modeling
of fuel life cycles.