Designer biocrude could help corn take flight
As demonstrated by ethanol, corn can be a tremendous feedstock for clean fuel production. But currently, it faces several limitations as a feedstock for sustainable aviation fuel (SAF).
For one, the process of converting corn to SAF is expensive and capital intensive. First, corn must be converted into ethanol, and there isn’t much infrastructure available to upgrade ethanol into SAF. And building out that infrastructure is an expensive proposition.
But more fundamentally, there is a blend wall with SAF made this way. Ethanol-based jet fuel doesn’t have the density or chemical properties to serve as a standalone jet fuel; it must be blended with conventional jet fuel at a minimum 50-50 ratio for use in aircraft.
But new research at the University of Minnesota funded by the corn checkoff could address both of those barriers, giving corn a more viable pathway for participation in the SAF market. Assistant Professor Allen Lee is attempting to engineer a specialized yeast strain that can convert corn glucose into a precise mixture of lipids and hydrocarbons.
Unlike ethanol, this “designer biocrude,” as Lee terms it, would have the density and chemical properties necessary to serve as a standalone jet fuel. And, it would have another benefit: it could be upgraded into SAF with the same infrastructure used to convert vegetable oils, waste oils, and fats into SAF, potentially limiting additional costly capital buildouts.
Lee said his key takeaway for farmers is that sugars are still by far the best feedstock for any type of biomanufacturing.
“I think there’s going to be a time when biomanufacturing is really going to be making an impact” in the aviation and maritime industries,” Lee said. “And when that time comes, glucose is still going to be the state of the art, the most efficient feedstock for biomanufacturing.”
Lee, who has a background in metabolic engineering, has worked with the yeast strain in this study, Yarrowia lipolytica, since his post-graduate days at MIT. The strain in use has shown strong capabilities to convert glucose into lipids.
What Lee aims to do with this project is engineer the yeast so it produces two compounds— lipids and a hydrocarbon called a-bisabolene—at specific rates. Producing enough of the a-bisabolene in the biocrude is critical to ensuring the density of the mixture. He said there are different genetic tools that allow scientists to control what compounds the yeast produce.
If the process works, Lee plans to work with chemical engineering Professor Paul Dauenhauer to convert the biocrude into SAF.
Ultimately, he said, the technology is positioned not as a competitor to existing corn-ethanol infrastructure, but as its essential complement.
“By providing the high-density blending component that ATJ lacks, Designer Biocrude empowers the corn industry to supply the full spectrum of molecules required for 100% renewable, drop-in aviation fuel,” he wrote in his research proposal.
