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 below.

Emissions estimates use the Argonne National Laboratory's GREET model (Wang et al., 2022). 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 hyperlinked linked references—in the Key Assumptions section below.

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 and emissions charts, this approach clearly distinguishes effects of fuels from those of vehicle technologies, because fuels remain constant while 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 2020 transportation ethanol wholesale price in Annual Energy Outlook 2021 (EIA, 2021), which reports a $1.39/gal wholesale price. Prices are converted to dollars per gasoline gallon equivalent using the Lower Heating Values from the GREET  model (Wang et al., 2021). 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. 
• 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.
• Starch Ethanol Emissions: The emissions intensities for starch ethanol are based on (1) the default values from the GREET model (Wang et al., 2022) 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 that 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 the GREET  model (Wang et al., 2022). 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 GREET model (Wang et al., 2022) 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.
• Biogenic Carbon: The biogenic carbon in a biofuel such as ethanol is considered to be carbon-neutral in the GREET model, as the biogenic carbon is assumed to be sourced from the atmosphere during biomass growth. Per the 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 taking into account 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.