The Biden administration is expected to release preliminary models for its sustainable aviation fuel (SAF) subsidy program in the coming weeks. Key for the ethanol industry is whether the corn-based fuel will qualify for the highest SAF subsidies. If ethanol is left behind, SAF suppliers will be mostly dependent on oilseed crops which could create a whole new problem – a massive increase in land use.
According to a new report from UC-Davis researchers, meeting the administration’s SAF goals would require the use of between eight and 11 million acres of corn or 35 and 50 million acres of soybeans, depending on how rapidly crop yields increase over the next six years.
Under the current goals set by the Biden administration, the US aims to increase SAF production from 16 million gallons today to three billion gallons by 2030. Technically, waste products like used cooking oil can be used to create SAF. However, the potential to scale production using these kinds of feedstock is uncertain as supplies are extremely limited and often unreliable.
That means in order to scale production to the US’s target level, SAF producers need to rely on agricultural feedstocks like soybeans and corn. However, the researchers warn that a rapid expansion of SAFs could reignite the food-versus-fuel debate and create similar changes in land use for conservation and crop production as the original RFS policies.
Since the creation of the RFS in the mid-2000s, the researchers say areas planted to corn and soybeans have increased by roughly 10 million acres each. Before passage of the RFS, the ethanol industry required corn from only four million acres of land to meet its demand for feedstock versus 27 million acres in 2022. That is down from a peak of 34 million acres in 2012, which has since declined due to a combination of stagnating ethanol demand and higher corn yields.
The use of soybeans for fuel was close to zero until the passage of the 2005 RFS. Biomass-based diesel consumption required about 10 million acres of soybeans and other crops until 2016, when California revised its implementation of the state’s Low Carbon Fuel Standard. Biomass-based fuels now account for over 50% of diesel consumption in California. As a result, soybean acres for fuel use have already more than doubled, to about 21 million acres.
Corn and soybeans are already the most widely grown crops in the US, accounting for close to a combined 179 million acres in 2023/24. The researchers claim that producing three billion gallons of SAF using only soybean oil would require 41 million acres of soybeans, almost half the area planted to the crop in 2022. That’s based on the yield trend from the past 20 years. Under a high-yield scenario, the acreage requirement falls to around 35 million, while as much as 50 million acres (about 60% of planted area in 2022) could be required if yields fall below trend.
Soybean oil, however, is a primary vegetable oil directly consumed by humans. Humans consume around half of current US soybean oil production. Meaning soybean oil used for biofuels directly competes with US food demand. Three billion gallons of SAF would require roughly 24 billion pounds of vegetable oil, which was 84% of the total US soybean oil supply in 2022.
Using trend corn yields, roughly nine million acres of corn are needed to produce three billion gallons of SAF, which is roughly 11 percent of the area planted to corn in 2022. Additionally, corn is used primarily as livestock feed or for ethanol, with less than 10% being used for human consumption in the United States. Meaning that using corn for SAF production would largely compete with livestock feed.
To look at it another way, a bushel of soybeans produces approximately 10.7 pounds of vegetable oil, and 8 pounds of vegetable oil are required for each gallon of SAF. In the trend-yield scenario, 72 gallons of SAF can be produced from an acre of soybeans. A bushel of corn can produce 2.85 gallons of ethanol given today’s production technology, and a gallon of SAF requires around 1.7 gallons of ethanol. Therefore, a single acre of corn can produce 330 gallons of SAF in the trend-yield scenario.
Even in the researchers’ low-yield scenario, corn production would generate 268 gallons of SAF per acre. That is more than three times the SAF obtained from an acre of soybeans under the high-yield scenario for that crop.
The researchers note that expanding cropland to produce biofuel generates carbon emissions that can offset much or all of their greenhouse gas benefits relative to fossil fuels. Therefore, if reducing land-use impacts is a primary goal for policymakers, the researchers conclude that corn ethanol is a better option than soybean oil for SAF production. The full report is available HERE.
