Sustainable aviation fuel from corn stover.
If you watch futuristic movies made in the 1980s or ‘90s, there’s often the theme of hazardous fuels being obsolete thanks to technological advances. For example, at the end of the 1985 movie “Back to the Future,” Doc Brown uses trash from a nearby dumpster to fuel his DeLorean time machine instead of plutonium.
Obviously, movies like that are fiction, but the idea of using trash as fuel is moving closer to the realm of reality. Southwest Airlines, the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL), and D3MAX have teamed up to convert corn stover, a waste feedstock, into sustainable aviation fuel (SAF). And they’re closer to proving commercial viability than you might think.
Trash into Sustainable Aviation Fuel
In 2021, the DOE, the U.S. Department of Transportation (DOT), and the U.S. Department of Agriculture (USDA) launched the Sustainable Aviation Fuel Grand Challenge. The challenge’s goal is to develop a commercially viable SAF that reduces greenhouse gas emissions by 50 percent compared to conventional fuel and to have this SAF meet 100 percent of aviation fuel demand by 2050.
As part of the challenge, the DOE awarded D3MAX almost $500,000 to design a pilot-scale (pre-commercial production) plant to validate technology for turning corn stover into ethanol for SAF production. D3MAX then used that grant to form SAFFiRE Renewables.
SAFFiRE is a planned 10-ton-per-day pilot plant project that combines NREL’s deacetylation and mechanical refining process (DMR) with D3MAX’s commercial sugar production and ethanol fermentation technology. Hypothetically, that will help solve the problem of economically breaking down corn stover to sugars because DMR operates under low temperatures, is less expensive, and doesn’t produce toxic byproducts.
Once broken down, the stover becomes sugar and is convertible to fuel, according to NREL. Additionally, NREL scientists have already proven this process in a lab, so the goal of the pilot plant is to prove commercial viability.
“SAFFiRE is the capstone of several NREL applied science projects. It plans to turn an agricultural waste product of little value—corn stover—into profitable and environmentally friendly fuels. What makes the project so unique is the combination of D3MAX’s commercial sugar production and ethanol fermentation technology and NREL’s patent-pending deacetylation and mechanical refining process, or DMR,” said Michael Himmel, project co-PI and NREL senior research fellow.
The project shows such promise that on June 1, Southwest Airlines announced it was investing in SAFFiRE Renewables and matching the DOE’s grant. Bob Jordan, Chief Executive Officer at Southwest, stated about the investment, “SAF is critical for decarbonizing the aviation sector. This is a unique opportunity to invest in what we believe could be a game-changing technology that could facilitate the replacement of up to approximately 5 percent of our jet fuel with SAF by 2030, with the potential to significantly continue to scale beyond the decade. This first-of-its-kind investment is another step we are taking to address our environmental impact, and it also supports our efforts to partner with organizations and government entities to help our industry reach the goal of carbon neutrality by 2050.”
Reduced Greenhouse Gas Emissions?
According to the White House, 11 percent of the U.S.’s transportation-related emissions come from aviation. Additionally, FuelCellsWorks reports that wet waste, like corn stover, is usually sent to landfills where, worldwide, it contributes up to 6 percent of greenhouse gas emissions.
Consequently, finding a way to use waste-based feedstock could significantly reduce CO2 emissions. In fact, NREL reports that if SAFFiRE is successful, it could reduce carbon intensity by up to 84 percent when compared to conventional jet fuel. Plus, SAF could also be less expensive than petroleum-based jet fuel.
As of this writing, SAFFiRE is in phase one of the process of validating the commercialization of turning corn stover into ethanol technology. And if it’s successful, SAFFiRE will be eligible for funding for its second phase, which will involve building and operating a pilot plant that produces renewable ethanol. After production, Lanzajet, a biorefinery under construction in Georgia, will upgrade SAFFiRE’s ethanol into SAF.
