The Minnesota Star Tribune reported last fall that the first sustainable aviation fuel, made from a Minnesota-grown crop called winter camelina, powered a Delta Air Lines flight from the Twin Cities to New York City. It marked the beginning of a plan by Minnesota SAF Hub—a coalition including Bank of America, Delta, Ecolab, and Xcel Energy—to eventually convert all Delta flights from MSP to bio-based jet fuels to reduce greenhouse gases.
You may think the sole star of the show here is sustainable aviation fuel. But, as a long-ago radio personality used to say, now for the rest of the story.
By tapping into the market for plant-based aviation fuel, University of Minnesota researchers at the Forever Green Initiative are commercializing two oil-producing plants—winter camelina and domesticated pennycress—that can give farmers a payday for planting winter cover crops that hold soil, take up excess nutrients, and help protect the quality of Minnesota’s streams and groundwater.
Mitch Hunter, associate director of the University’s Forever Green Initiative, says “What we’re trying to do is develop crops that make farmers money, and in the process, provide all those environmental benefits that we’ve been trying to get to for so long with very little success.”
From cover crops to jet fuel
This story really begins with “the big brown spot”—the vast agriculture region of the upper Midwest that stands barren from October through April, with nothing growing to protect the soil. “You can see the brown of this uncovered landscape from space,” says Hunter.
That bare earth is prone to wind and water erosion. Runoff of nutrients, especially nitrogen, into streams and groundwater fertilizes lakes, pollutes sources of drinking water, and contributes to the “dead zone” at the end of the Mississippi River. Says Hunter, “When soil has nothing living on it, rain falls, filters through the soil, and draws those nutrients directly into our waterways. You have to have a plant living there to take up the nitrogen and the phosphorus.”
The solution—plant something, anything, to hold soil and take up excess nutrients until the next cash crop is planted. A recent report by Forever Green partners, including consultants Ecotone Analytics and Friends of the Mississippi River, estimated that widespread use of cover crops could reduce nitrogen loss from farmland by 23 percent and soil erosion by 35 percent by 2050.
But folks have promoted cover crops for a long time. “They get a lot of buzz, and they’re adopted in Minnesota on 2 or 3 percent of the total cropland, despite years and years and years of education and investment and incentives,” says Hunter. “So that model isn’t working.”
The problem? Cover crops take both time and money.
The many contributions of the Forever Green Initiative
So about 30 years ago, the late Don Wyse, Forever Green cofounder and codirector, began working with farmers to grow a perennial rye grass that not only anchors soil, but can be sold for commercial grass seed. Says Hunter, “All of a sudden, you transformed the cropping systems in that region to have perennial cover for a large part of the rotation, and it was all because they developed a crop that actually made farmers money.”
Wyse and his colleagues went prospecting for other potentially profitable cover crops. Of 15 or so, two are pertinent to our story today. The first is winter camelina, an old crop from Europe related to cabbage, kale, broccoli, and canola. Like canola, it produces tiny seeds with an oil content as high as 35 percent. The other is pennycress, a new crop bred from a ubiquitous weed. Like camelina, it is rich in oil, exceptionally winter hardy, and even quicker to grow and mature.
Forever Green’s plan is to target the more than 2 million acres in Minnesota used to raise spring wheat, corn silage, alfalfa, and small grains—crops that are harvested in early fall. Then farmers can plant winter camelina or pennycress, let it grow through late fall, winter, and early spring, and harvest the oil seed crop in late spring before planting the next cash grain crop.
But how to market camelina or pennycress oil seeds to get a good price? Selling them for food-grade oil means competing with a lot of well-established oils like canola and sunflower. Sustainable diesel fuel is a possibility, but ground transportation seems to be moving toward electrification.
Enter sustainable aviation fuel, a use that’s growing exponentially. Aviation accounts for about 2 percent of global emission of the carbon dioxide that drives climate change, according to the U.S. Department of Energy. Like other fields of transportation, aviation seeks to reduce its fossil fuel use.
Trains, trucks, and automobiles have been able to replace internal combustion engines with electric motors and massive banks of batteries. Unfortunately, in the air, every ounce counts—so aviation has looked to fuels from renewable biological sources such as used cooking fat and dedicated energy crops.
Sustainable aviation fuel makes up only about 0.1 percent of total jet fuel burned today, but the hope is to meet much more of the country’s aviation fuel needs with sustainable products in the future.
Hunter adds that state incentives and private support will continue to further the development of sustainable fuels and environmentally beneficial farming practices.
“That market is extremely hungry for oil,” says Hunter. “If we had a big supply right now, we could sell it.”
