Cost and Life Cycle Emissions of Ethanol Produced with an Oxyfuel Boiler and Carbon Capture and Storage

Abstract

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.

Should Transportation Be Transitioned to Ethanol with Carbon Capture and Pipelines or Electricity? A Case Study

“…Usually, purified CO 2 is compressed, often from 1 bar (atmospheric pressure) to 150 bar, for pipe transport. This requires ∼110 kWh/tonne-CO 2 -compressed . In Summit’s proposal, however, the CO 2 will be compressed to only above 74.5 bar, but the temperature will also be raised to above 31.1 °C to enter a supercritical state, which is a very dense form of CO 2 that is neither liquid nor gas.…”

Carbon farming: a circular framework to augment CO2 sinks and to combat climate change

“…The circular carbon economy (CCE) is a regenerative idea that depends on designing closed-loop systems and reusing materials and resources to reduce emissions, rely on renewable energy, and eliminate waste. 172 The core tenet of CE is “reduce, reuse, and recycle,” which changes the conventional linear open paradigm of “resources/products/waste” into a cyclical one of “resources/products/wastes/resources”. 50,173 Circular farming encompasses two distinct cycles, namely the biological and the technical cycles.…”

“…, polyethylene), biocarbon (biochar), and meticulously purified biogenic CO 2 with subsequent geological sequestration. 56,57,172 Over the past 5 to 10 years, the landscape of carbon-negative technologies in development has rapidly expanded and been streamlined into seven primary categories: bioenergy with carbon capture and storage (BECCS) (0.5–5 GtCO 2 ), afforestation and reforestation (0.5–3.6 GtCO 2 ), direct air carbon capture and storage (DACCS) (0.5–5 Gt CO 2 ), enhanced weathering (2 to 4 GtCO 2 ), biochar (0.5 to 2 GtCO 2 ), and soil carbon sequestration (<5 Gt CO 2 ). 176 These technological avenues yield a cumulative annual CO 2 removal of 9–24.6 Gt CO 2 , aligning with the targets established by the IPCC and the estimated cost ranges from $5 – $300 per tCO 2 .…”

Oxyfuel Combustion Makes Carbon Capture More Efficient

“…According to international reports, CCUS could play an important role in reducing CO 2 emissions. 10,11 Implementation of this process may vary according to several technological parameters, such as the flue gas flow rate, thermodynamic properties, CO 2 composition, and the origin of flue gas. 12,13 There are three main options available for the mitigation of greenhouse gas emissions: oxyfuel combustion 14,15 where the fossil fuel is combusted with oxygen instead of air; air combustion 16,17 where the combustion process happens in the presence of air; and precombustion 18,19 where carbon removal occurs prior to combustion.…”

“…Energy intensification is a more efficient tool for emission reduction in different industries; however, there are inevitable carbon emissions that should be treated by other approaches such as Carbon Capture Utilization and/or Storage (CCUS). According to international reports, CCUS could play an important role in reducing CO 2 emissions. , Implementation of this process may vary according to several technological parameters, such as the flue gas flow rate, thermodynamic properties, CO 2 composition, and the origin of flue gas. , …”