"[USDA's models are] more marketing than science," said Jason Hill, a professor and biofuels expert at the University of Minnesota. The model, some scientists say, has undercounted how much land has been plowed under for row crops.

Doug Berven, vice president of corporate affairs at Sioux Falls-based Poet, the nation's largest ethanol company, dismisses criticism of indirect land-use analyses.

"This completely ignores the fact that we're oversupplied [with corn] dramatically," Berven said.

With environmental and farm groups squared off, the White House convened a working group to adopt the tax credit's underlying model, promising to release the new analysis by March 1. But that date has come and gone.

In mid-February, Reuters suggested the soon-to-be-released model would ramp up requirements for corn ethanol's eligibility, putting pressure on farmers to reduce tillage and plant cover crops. For some farmers, this is concerning.

Syverson, a former president of Minnesota Corn Growers Association, is experimenting this winter with a cover crop of rye in his fields. But he expressed reservation about widespread regenerative practices, such as cover crops.

"We're a long ways north," he said. "In Minnesota, we run our crops right up to the freezing temperatures, and we don't have any time after the main crop is off where it's actually beneficial [to plant a cover crop]."

According to the U.S. Department of Agriculture's 2022 census, released last month, only 3% of Minnesota's croplands see a winter cover.

Whatever the ultimate decision, industry officials and members of Congress are asking for a decision soon.

Last month, Minnesota's two senators — Amy Klobuchar and Tina Smith — as well as congressional members Angie Craig and Brad Finstad signed a letter to the Biden Administration asking that they "act quickly" in developing the tax credit model.

The White House did not respond to the Star Tribune's request for comment.

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