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It would require approximately 13 billion gallons of sustainable aviation fuel (SAF) to meet the goal of supplying 50% of the United States annual domestic aviation fuel needs

Summary​

The goals of biofuels have changed over the past three decades. Biofuels were initially promoted in the United States to achieve energy independence by reducing reliance on imported oil, though their public messaging later emphasized sustainability. First-generation corn ethanol has failed to meet sustainability goals despite reducing oil imports. Biofuels are projected to remain crucial for decarbonizing hard-to-abate sectors like aviation, where sustainable aviation fuels (SAF) are considered the most viable short-term solution. The analysis sets a goal to supply 50% of US domestic aviation fuel using ethanol-based SAF without food crops. To meet this, 13 billion gallons of SAF would be required annually based on 2019 consumption levels.

When discussing biofuels and evaluating their sustainability and viability as an energy carrier, it is important to define a clear goal for their usage. In the 2000s, when biofuels were heavily boosted in the United States through subsidies, tax incentives, and research funding, the goal of the biofuels at the time was not focused on sustainability or CO₂ reduction, but rather, to achieve a higher degree of energy independence by reducing reliance on foreign imported oil. Whether sincere or an example of 'greenwashing', much of the public messaging around biofuels transformed into these areas of sustainability where corn-derived ethanol became known as a 'renewable' fuel that could replace fossil fuels in the transportation sector, a notion that still persists to this day. Due to the large body of evidence that challenges the sustainability credentials of corn bioethanol, it is reasonable to state that biofuels have not achieved their sustainability goals while being successful in reducing reliance on foreign imported oil.

Due to significant concerns regarding indirect land use change (ILUC), changes to soil organic carbon (SOC), among other factors, the argument for large-scale usage of biofuels in transportation has fallen out of favour with the rapid rise of electric vehicles and renewable electricity generation. However, this does not mean that biofuels cannot make an impact in decarbonizing or reducing CO₂ emissions in a number of sectors that are considered hard to abate. In fact, modelling conducted by organizations such as the International Energy Agency (IEA) on pathways towards net zero emissions still heavily relies on biofuels to achieve their goals. While widespread electrification of all sectors is most desirable, biofuels are still required to provide the energy needs of the steel industry (10%), cement production (30%), general transportation (15%), and most notably aviation (45%) 1 2.

Decarbonizing aviation​

The aviation industry is considered one of the primary sectors where biofuels can make a significant impact in decarbonizing through the usage of drop-in sustainable aviation fuel (SAF). There are a number of options available for decarbonizing the aviation sector including biofuels, synthetic fuels (E-jet), electrification, and hydrogen. In theory, electrification (hybrid or full electric) or clean-burning hydrogen would be the most desirable options due to their ability to operate with near zero carbon emissions. However, electrification is limited by the low energy density of batteries with respect to their weight, and hydrogen runs into the same issues but with poor energy density with respect to its volume, requiring heavy cryogenic storage tanks 3. Additionally, neither hydrogen nor electrification are considered 'drop-in' replacements, meaning that their adoption would require comprehensive changes to the way that the aviation industry operates, which could only occur over a longer time scale 3. Because of this, sustainable aviation fuels such as biofuels and E-jet fuels are considered the most viable option for decarbonization in the short to mid term.

Currently, a number of sustainable aviation fuels have been approved by the United States for a maximum 50% blending, including Alcohol-to-Jet Synthetic Paraffinic Kerosene (ATJ-SPK), Fischer-Tropsch Synthetic Paraffinic Kerosene (FT-SPK), and Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosene (HEFA-SPK) 4.

Biofuel goals​

Given that a variety of sustainable aviation fuels have been approved for 50% blending, the goal of this analysis will be defined as the following:

"Supply 50% of the United States domestic aviation fuel needs utilizing ethanol-based sustainable aviation fuel (SAF) without the use of food crops."

How much sustainable aviation fuel is needed?​

In 2019, the average daily consumption of jet fuel in the United States was 1.7 million barrels per day 5. This value is greater than the value in the years following, with the 2023 consumption being at 1.65 million barrels a day, indicating that aviation levels still have not returned to pre-pandemic levels, while also indicating that the US commercial fleet is becoming more efficient 6 7. Choosing the 2019 value as it better matches predictions that the aviation industry will continue to grow even as fuel efficiencies increase 8, the total annual aviation fuel consumption can be estimated as follows:

Aviation fuel consumption [barrels/day]×42=Aviation fuel consumption [gallons/day]1,700,000×42=71,400,000 [gallons/day]\begin{align*} \mathrm{\text{Aviation fuel consumption [barrels/day]} \times 42} & = \mathrm{\text{Aviation fuel consumption [gallons/day]}} \\ \mathrm{1,700,000 \times 42} & = 71,400,000 \space \text{[gallons/day]} \end{align*}

For annual consumption:

Aviation fuel consumption [gallons/day]×365=Aviation fuel consumption [gallons/year]71,400,000×365=26,061,000,000 [gallons/year]\begin{align*} \mathrm{\text{Aviation fuel consumption [gallons/day]} \times 365} & = \mathrm{\text{Aviation fuel consumption [gallons/year]}} \\ \mathrm{71,400,000 \times 365} & = 26,061,000,000 \space \text{[gallons/year]} \end{align*}

Using the maximum 50% blending limit, we can estimate the total annual US sustainable aviation fuel requirement to meet the stated goal:

Aviation fuel consumption [gallons/year]2=Sustainable aviation fuel consumption [gallons/year]26,061,000,0002=13,030,500,000 [gallons/year]\begin{align*} \mathrm{\frac{\text{Aviation fuel consumption [gallons/year]}}{2}} & = \mathrm{\text{Sustainable aviation fuel consumption [gallons/year]}} \\ \mathrm{\frac{26,061,000,000}{2}} & = 13,030,500,000 \space \text{[gallons/year]} \end{align*}

Therefore, using 50% blending, to meet the 2019 annual jet fuel consumption levels of 26,061,000,000 gallons (98,645,513,010 L), 13,030,500,000 gallons (49,322,756,505 L) of sustainable aviation fuel would be required each year.

Why alcohol-based sustainable aviation fuels​

Even though Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosene (HEFA-SPK) are the only sustainable aviation fuels that are currently used commercially and are the most cost competitive, limitations to supply and environmental considerations in sourcing vegetable fats for feedstock mean that HEFA will not be viable to scale up sustainably 4. When selecting between Alcohol-to-Jet Synthetic Paraffinic Kerosene (ATJ-SPK) paired with the biochemical conversion of biomass into ethanol, and Fischer-Tropsch Synthetic Paraffinic Kerosene (FT-SPK) paired with the thermochemical gasification of biomass, the main consideration for choosing between them comes down to cost vs. complexity. The production of ethanol from lignocellulosic feedstocks is a complicated process requiring biomass cultivation and collection, pretreatment, enzymatic breakdown, and fermentation. Each of these steps can be costly and drawn out, but the complexity of each individual process is generally considered low. In comparison, the Fischer-Tropsch process contains far fewer steps, is agnostic to the types of feedstocks used, and performs better with respect to greenhouse gas emissions 4. However, due to the high temperatures required in the gasification reactors to produce syngas and the precise control of oxygen, waste buildup, and temperature levels needed to remain optimal, gasification reactor design and construction become significantly more complex 4. Because of these complications, many gasification plants (not including those that use fossil fuels as feedstock) have struggled to remain operational due to equipment failures, with the last remaining waste-to-energy facility run by Fulcrum Bioenergy closing in 2024 after encountering numerous production issues 9. Whereas second generation alcohol production resulted in successfully operating plants that ran for a number of years, yet they were limited by their cost competitiveness with 1st generation alcohol production.

This is not a denouncement of the Fischer-Tropsch process or a strong endorsement of alcohol-to-jet, but rather a recognition that the alcohol-to-jet process is showing the most promise in the short term. As previously mentioned, this analysis will ignore hydroprocessed esters and fatty acid derived aviation fuels due to their feedstock limitation

Sources​

Footnotes​

  1. Groppi, D., Pastore, L. M., Nastasi, B., Prina, M. G., Garcia, D. A., & de Santoli, L. (2025). Energy modelling challenges for the full decarbonisation of hard-to-abate sectors. Renewable and Sustainable Energy Reviews, 209, 115103. https://doi.org/10.1016/j.rser.2024.115103 ↩

  2. International Energy Agency. (2022). World energy outlook 2022. IEA. https://www.iea.org/reports/world-energy-outlook-2022 ↩

  3. Detsios, N., Theodoraki, S., Maragoudaki, L., Atsonios, K., Grammelis, P., & Orfanoudakis, N. G. (2023). Recent advances on alternative aviation fuels/pathways: A critical review. Energies, 16(4), 1904. https://doi.org/10.3390/en16041904 ↩ ↩2

  4. U.S. Department of Energy. (n.d.). Sustainable aviation fuel. Alternative Fuels Data Center. https://afdc.energy.gov/fuels/sustainable-aviation-fuel ↩ ↩2 ↩3 ↩4

  5. U.S. Energy Information Administration. (2022, December 5). Less U.S. jet fuel consumption on average in 2022 than in 2019. Today in Energy. https://www.eia.gov/todayinenergy/detail.php?id=54879 ↩

  6. U.S. Energy Information Administration. (2024, July 8). U.S. jet fuel consumption in 2023 remained below the pre-pandemic high. Today in Energy. https://www.eia.gov/todayinenergy/detail.php?id=62443# ↩

  7. U.S. Energy Information Administration. (2025, August 26). U.S. jet fuel consumption growth slows after air travel recovers from pandemic slowdown. Today in Energy. https://www.eia.gov/todayinenergy/detail.php?id=66004 ↩

  8. International Renewable Energy Agency. (2024). Decarbonising hard-to-abate sectors with renewables: Perspectives for the G7. International Renewable Energy Agency. https://www.irena.org ↩

  9. Ethanol Producer Magazine. (2024, September 16). Fulcrum BioEnergy files for bankruptcy. https://ethanolproducer.com/articles/fulcrum-bioenergy-files-for-bankruptcy ↩