Ethanol

Ethanol is a renewable fuel. Made from biomass (i.e., a variety of plant materials), ethanol is used in 98% of U.S. gasoline. Typically, gasoline consists of E10 (10% ethanol, 90% blendstock for oxygenate blending (BOB)) (DOE, 2019). For additional background, see the Alternative Fuels Data Center's Ethanol Fuel Basics webpage.

Detailed information about ethanol is presented next. 

Emissions estimates use the Argonne National Laboratory's Research & Development Greenhouse gases, Regulated Emissions, and Energy use in Technologies (R&D GREET) model (Wang et al., 2023). The underlying source for a value in the table can be seen by placing your mouse cursor over that value. The data sources are also cited—with linked references—in the Key Assumptions section next.

Note: These results are highly context dependent and may not represent the optimal values for each fuel pathway. We recommend caution, and review of other sources, before making comparisons between the cases reported in the table above.

Key Assumptions

The data and estimates presented here are based on the following key assumptions:

• Fuel Price: The fuel price (e.g., Lowest Cost, Lowest Emissions) is associated with a single year. Because we do not provide a time-series trajectory, here we show fuel price at a frozen level for all years so we can offer a range of fuel price values. In the levelized cost of driving (LCOD) and emissions charts, this approach clearly distinguishes effects of fuels from those of vehicle technologies because fuels remain constant whereas vehicle technologies change over time.
• Plant Gate Blendstock Fuel Prices: The plant gate blendstock fuel prices shown here are meant to reflect minimum fuel selling prices (and do not include distribution costs or taxes).
• Starch Ethanol Current Market Fuel Price: The starch ethanol current market fuel price is from the 2022 transportation ethanol wholesale price in the Annual Energy Outlook 2023 (EIA, 2023). Prices are converted to dollars per gasoline gallon equivalent using the Lower Heating Values from the Research & Development Greenhouse gases, Regulated Emissions, and Energy use in Technologies (R&D GREET)  model (Wang et al., 2023). We do not provide plant metrics for starch ethanol because the price is based on current market values and not on modeled costs with specific plant design assumptions.
• Biochemical Ethanol Cost: Biochemical ethanol cost is based on a cradle-to-grave analysis (Elgowainy et al., 2016), with the dollar year updated. The biochemical plant in the cradle-to-grave study is based on a design case of 2,200 dry tons per year, but current scales for biochemical ethanol production are much smaller. Bioechemical ethanol plant characteristics are based on the process design of (Humbird et al., 2011), with updated costs.
• Thermochemical Ethanol Cost: The thermochemical ethanol cost is based on analysis from Dutta et al. (Dutta et al., 2011), with the dollar year updated, and is consistent with current design cases. The mature industry feedstock production cost for the future modeled, high volume (n^th) plant is calculated based on an assumed $61/ton feedstock cost, based on recent U.S. Department of Energy Bioenergy Technologies Office design cases. Production estimates for current thermochemical ethanol plants are not available. Thermochemical ethanol plant characteristics are based on the process design of (Dutta et al., 2011), with updated costs.
• Starch Ethanol Emissions: The emissions intensities for starch ethanol are based on (1) the default values from the R&D GREET model (Wang et al., 2023) and (2) (Lee et al., 2021). These estimates assume the following mix of plant types and energy use as an industry average: 89% dry milling (92% natural gas, 8% coal) and 11% wet milling plant (72.5% natural gas, 27.5% coal). Note the emissions intensity of starch ethanol might vary from the industry average based on plant types and production process assumptions; for example, the well-to-wheels CO2e emissions of corn starch ethanol may vary between 51,100 g/mmBtu and 117,000 g/mmBtu (California Air Resources Board, 2020), (US EPA, 2016), (Argonne National Laboratory, 2018).
• Biochemical Ethanol Emissions: The emissions for biochemical ethanol are based on R&D GREET model defaults as documented in 2021 (Wang et al., 2021), which updates the original process modeling from Humbird et al. (Humbird et al., 2011) and Tao et al. (Tao et al., 2014).
• Cellulosic Thermochemical Ethanol Emissions: Emissions intensities for cellulosic thermochemical ethanol are based on the R&D GREET model (Wang et al., 2023) and the indirect gasification pathway from Dunn et al. (Dunn et al., 2013), which assumes a southern pine feedstock and does not include land use change emissions, and (Dunn et al., 2018).
• Biogenic Carbon: The biogenic carbon in a biofuel such as ethanol is considered carbon-neutral in the R&D GREET model because the biogenic carbon is assumed to be sourced from the atmosphere during biomass growth. According to the R&D GREET model convention, the biogenic carbon credit is allocated to the well-to-tank phase of the biofuel life cycle, which often results in a negative well-to-tank CO2e emissions value after considering greenhouse gas emissions associated with all upstream activities (e.g., farming, land use change, feedstock transportation, and biomass conversion to biofuel).

The data downloads include additional details of assumptions and calculations for each metric.

To see additional information, place your mouse cursor over a value in the table.  

Definitions

For detailed definitions, see:

CO2e

NOx

SOx

PM

Fuel price

Scenarios

Well-to-tank emissions

Well-to-wheels emissions

References

The following references are specific to this page; for all references in this ATB, see References.