Trading some corn-ethanol land for solar can triple US solar energy production

In the U.S., 12 million hectares of land—an area about the size of New York state—are currently used to grow corn for ethanol. But strategically converting a small portion of that to solar facilities could vastly increase energy production per hectare, as well as provide ecological benefits and financial resiliency for farmers.

In a paper published April 21 in the Proceedings of the National Academy of Sciences, researchers found that putting solar facilities on just 3.2% of land currently used for corn-ethanol crops would increase the production of utility-scale solar energy from 3.9% to 13%. Adding solar facilities with features that boost biodiversity, such as perennial plants, could provide further benefits, including filtration of runoff and habitats for pollinators and wildlife.

“By envisioning energy development as a part of ecosystems, we can begin to recognize socioecological trade-offs that can inform sustainable land-use change,” said senior author Steven Grodsky, assistant professor of natural resources and the environment, and assistant unit leader of the U.S. Geological Survey New York Cooperative Fish and Wildlife Research Unit, housed in the College of Agriculture and Life Sciences.

“We demonstrated that even small injections of ecologically informed, highly efficient solar in vast cropland landscapes, largely used to produce ethanol fuel, can lead to great potential benefits for people and planet,” Grodsky said.

The authors, including postdoctoral researchers Matthew Sturchio and Adam Gallaher, first compared the amount of energy, in equivalent thermal units, produced by corn-ethanol crops versus solar arrays per hectare. They found that the energy generated by one hectare of utility-scale solar would require 31 hectares of corn-ethanol crops. In other words, solar can generate the same amount of energy as corn-ethanol in just 3.2% of the land used.

In addition to requiring more land, growing corn for ethanol, which is used primarily as an additive for gasoline, has led to homogenized crops, mostly in the midwestern U.S., that require large amounts of water, fertilizers and pesticides; also, the savings on emissions are a matter of debate, with some studies finding corn-ethanol more carbon-intensive than gasoline. And as more consumers transition to electric vehicles, the need for ethanol is declining, the authors said, while demand on the electric grid is expected to grow by up to 75% by 2050.

“Solar has a bunch of different end uses,” said Sturchio, first author of the study. “Energy going to the grid could go to a home, your car, your phone, your computer, anything that’s electrified.”

The authors cited previous research that shows that planting perennials around solar arrays can provide ecological and agricultural benefits—increased filtration and habitats for pollinators and wildlife—which could be particularly beneficial when incorporated in the large, homogenized corn-ethanol croplands in the Midwest.

Using spatial analysis, the researchers identified sites in the Midwest within two miles of transmission infrastructure, where solar could realistically, and in the near-term, replace 3.2 % of the land used to grow corn-ethanol.

“The common thing we hear is that it’s $1 million a mile to build transmission infrastructure, so once you get outside a five-mile buffer, it’s not going to happen,” Sturchio said. “The way to get these projects done is to put them where there’s already transmission infrastructure.”

The authors found sites within the two-mile buffer that could also greatly benefit from land diversification—where planting perennials could improve water quality and provide pollinator and wildlife habitats.

“In the Midwest, you can see it from space that these monocultures of annual croplands take up the majority of the landscape,” Sturchio said. “We’re lacking natural areas, and placing solar in these homogenized croplands offers an economically viable pathway for large scale restoration that increases landscape diversity.”

For farmers, the conversion of even a small portion of their corn-ethanol crop to solar could increase revenue on the land—an estimated three or four times what they might make with corn for ethanol—which could provide resiliency in years when crops underperform.

“It could be a way for farmers to diversify their land uses and to stay on their land when crops aren’t as successful,” Sturchio said. “I think there’s tremendous opportunity.”

Transitioning the land used to grow corn for ethanol to renewables could yield even greater energy returns, the researchers said. Co-locating wind energy facilities with the solar arrays at the sites the authors identified could improve consistency and reliability of the grid while adding 23% to U.S. 2050 decarbonization goals. If 46% of the land used for corn-ethanol production were transitioned to solar, they said, it could generate enough energy to completely meet those goals.

The next phase of needed research, Sturchio said, is on-the-ground—to engage with rural communities.

“In those areas we identified, we want to give stakeholders the power to make informed decisions,” Sturchio said. “Energy transitions do not happen in a vacuum, so it will be important to evaluate how these land-use changes impact people and communities.”