Ethanol

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

Detailed information about the ethanol production pathways is presented below.

Ethanol

Key Assumptions

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

• 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.
• The plant gate blendstock fuel prices shown here are meant to reflect minimum fuel selling prices (and do not include distribution costs or taxes).
• The starch ethanol current market fuel price is from the 2018 transportation ethanol wholesale price in Annual Energy Outlook 2019 (EIA, 2019), which reports a $1.53/gal wholesale price. The price is converted from dollars per gallon to dollars per gasoline gallon equivalent using the lower heating values of gasoline (112,194 Btu/gal) and ethanol (76,330 Btu/gal) from the GREET model (Argonne National Laboratory, 2018). 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.
• The emissions intensities for starch ethanol are based on the default values from GREET 2018 (Argonne National Laboratory, 2018), which assumes 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 may 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 51,100-117,000 g/mmBtu (California Air Resources Board, 2020); (US EPA, 2016); (Argonne National Laboratory, 2018).
• Biochemical ethanol fuel production estimates are based on the cradle to grave analysis (Elgowainy et al., 2016). 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. The Mature Industry Feedstock Production Cost for Current plants is calculated based on an assumed $100/ton feedstock cost, and for the future modeled, high volume (n^th) plant is calculated based on an assumed $71/ton feedstock cost. The cradle to grave analysis only estimated CO₂e emissions, so other air emissions estimates are not presented.
• The thermochemical ethanol fuel production estimates, which are based on analysis from Dutta et al. (Dutta et al., 2011), are 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 Office of Energy Bioenergy Technologies Office design cases. Production estimates for current thermochemical ethanol plants are not available.
• Emissions intensities for cellulosic thermochemical ethanol are from the indirect gasification pathway from Dunn et al. (Dunn et al., 2013). Dutta el al. (Dunn et al., 2013) assumes a southern pine feedstock and does include land-use change emissions.
• The biogenic carbon in a biofuel such as ethanol is considered carbon-neutral in the GREET model, as the biogenic carbon is assumed to be sourced from the atmosphere during biomass growth. Per a 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 detail on assumptions and calculations for each metric.

Definitions

For detailed definitions, see:

CO₂e emissions

Coproducts sales revenue

Fixed capital investment

Fixed operating cost

Fuel price

Mature industry feedstock production cost

NO_X emissions

Other (non-feedstock) variable operating cost

PM emissions

Power sales revenue

Scenarios

SO_X emissions

Throughput capacity

Total product yield

Units

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.