Decarbonization of
transportation fuels represents one of the most
vexing challenges for climate change mitigation. Biofuels derived
from corn starch have offered modest life cycle greenhouse gas (GHG)
emissions reductions over fossil fuels. Here we show that capture
and storage of CO2 emissions from corn ethanol fermentation
achieves ∼58% reduction in the GHG intensity (CI) of ethanol
at a levelized cost of 52 $/tCO2e abated. The integration
of an oxyfuel boiler enables further CO2 capture at modest
cost. This system yields a 75% reduction in CI to 15 gCO2e/MJ at a minimum ethanol selling price (MESP) of $2.24/gallon ($0.59/L),
a $0.31/gallon ($0.08/L) increase relative to the baseline no intervention
case. The levelized cost of carbon abatement is 84 $/tCO2e. Sensitivity analysis reveals that carbon-neutral or even carbon-negative
ethanol can be achieved when oxyfuel carbon capture is stacked with
low-CI alternatives to grid power and fossil natural gas. Conservatively,
fermentation and oxyfuel CCS can reduce the CI of conventional ethanol
by a net 44–50 gCO2/MJ. Full implementation of interventions
explored in the sensitivity analysis would reduce CI by net 79–85
gCO2/MJ. Integrated oxyfuel and fermentation CCS is shown
to be cost-effective under existing U.S. policy, offering near-term
abatement opportunities.