The effects of a contaminated ethanol plant in Nebraska brewing fuel with discarded seed coated with pesticides continue to reverberate in Minnesota.

The widely used seeds are pretreated with neonicotinoids — pesticides that are neurotoxins and that have devastated bee populations and been shown to harm mammals and birds.

The Nebraska contamination prompted a proposed ban in Minnesota on using neonicotinoid-treated seed for food, feed, oil or making ethanol but the legislative effort failed under opposition from Senate Republicans.

Meanwhile, a Land O'Lakes unit that shipped discarded pretreated seed to the Nebraska plant, AltEn LLC, agreed Friday to clean up the site along with five other large seed companies — AgReliant Genetics, Corteva Agriscience, Syngenta Seeds, Bayer U.S. and Beck's Superior Hybrids, all of which operate in Minnesota.

In a statement to the Star Tribune, Arden Hills-based Land O'Lakes said it terminated its relationship with AltEn when it learned of the problems.

"We remain committed to the proper disposal of treated seed and have created an internal team to determine our future disposal practices and identify responsible partners," the statement read.

Researchers are still trying to gauge the extent of the AltEn pollution.

The 24-million-gallon capacity plant is just outside Mead, Neb., a small town near Omaha. The site has leaking lagoons of toxic wastewater and 84,000 tons of contaminated distiller's grain, a byproduct that was being spread on fields, according to Nebraska state documents. AltEn was using manure from a cattle lot next door for methane to fuel the plant.

AltEn closed in February, the same month a frozen pipe burst and spilled about 4 million gallons of manure and pesticide-contaminated wastewater.

Nebraska Attorney General Doug Peterson has sued AltEn, accusing it of polluting public water and illegally operating a solid waste management facility, among other things. It's one of two ethanol plants using treated seed, according to the complaint. The other is in Kansas. Nebraska lawmakers have banned using treated seeds for ethanol.

AltEn did not respond to numerous requests for comment.

The plant is owned by Kansas-based AltEn LLC associated with late businessman Dennis M. Langley. State documents show Langley's stepson Tanner Shaw as president.

In its answer to Nebraska's complaint, AltEn denied wrongdoing and said it had a permit for a solid waste compost facility.

Minnesota ag professionals say they don't think it could happen here.

Ashwin Raman, spokesman for the Minnesota Bio-Fuels Association, said it's not aware of any ethanol producers in the state using neonicotinoid-treated seeds to make ethanol. Randall Doyal, chief executive of Al-Corn Clean Fuel, one of Minnesota's largest ethanol producers, said no responsible producer would do that.

"No way in hell," Doyal said. "You can't use that stuff. I'm not surprised they created such a tremendous environmental wreck.

"I think the seed manufacturers are going to have to think what to do with it instead of just dumping it off somewhere."Others say the risks of neonicotinoid-treated seeds demand extra caution. Chris Cowen, a local lobbyist for the Pesticide Action Network, called AltEn an ecological disaster that Minnesota should do everything to avoid.

"Why Minnesota would hesitate for a minute in making treated seed feedstock illegal, begs the question: How bad does it have to be?" Cowen said. "Concerned Minnesotans need to look beyond the Legislature to have any chance of fixing this."

The AltEn situation has drawn concern about the widespread use of treated seeds and disposal challenges. Farmers typically hold leftovers for the next year or return it to dealers who typically return it to seed companies.

Seed companies can incinerate the discarded seeds at permitted facilities; send them to power plants or cement kilns; or landfill them, according to the American Seed Trade Association. One seed company said discarded seeds can be donated for "conservation initiatives" and wildlife habitat.

But it seems most companies were shipping discards to AltEn. AltEn claimed to have been handling 98% of the country's unused treated seed.

Mac Ehrhardt, owner of Albert Lea Seed, which mainly sells organic and non-GMO seed, said AltEn has triggered a "necessary reckoning."

His company also sells treated seeds and shipped some to AltEn, Ehrhardt said.

"It's really discouraging to find out that their practices led to this contamination problem," Ehrhardt said.

"The big picture thing for me is the seed industry needs to be honest with itself about the dangers of the chemicals that it uses and needs to find safe ways to dispose of these chemicals when they are not used," he said, adding that the seed industry "hasn't been willing to face the music on this."

Treated seed containers have a tag saying "Do not use for feed, food or oil purposes." Some farmers say that's enough and a ban is unnecessary.

Minnesota Department of Agriculture spokeswoman Margaret Hart said the agency ensures the labels have the instructions, but doesn't enforce how they are followed. The agency does not regulate treated seed, Hart said, although inspectors do check to see that it isn't in grain used for food, feed or making oil.

The agency supported the proposed ban on making ethanol with treated seed, Hart said.

It's estimated that nearly all corn in the U.S. and up to half of soybeans are coated with neonicotinoids, a class of insecticides called neonics that includes thiamethoxam, imidacloprid and clothianidin. All three are banned in Europe for outdoor use.

The Minnesota Department of Natural Resources (DNR) has recently found neonics in the majority of deer spleens from deer tested across the state. South Dakota deer research has shown neonics harm the animal's reproductive system and can kill fawns.

"We're at the early stages of trying to understand and untangle these relationships," said Dave Olfelt, the DNR's director of fish and wildlife.

The AltEn situation has seed companies scrambling for alternatives.

In its statement, Land O'Lakes said it discarded only "a very minimal amount" of treated seed.

"Once we were made aware of the environmental conditions created by AltEn, we terminated our relationship and, in fact, have not discarded any treated seed since that termination," the statement said.

Bayer AG is also considering options: "In the meantime, we are sending our unused seed to a sustainable packager who transports it to a specially permitted, high-temperature incineration facility," spokeswoman Susan Luke said.

Mead resident Jody Weible, said she is "beyond grateful" the seed companies have stepped up. The stench is unbearable, she said.

"It's between rotten, acidic and sweet, and it will burn your nose," she said.

Bill Bond, executive director of Minnesota Crop Production Retailers, said AltEn was operating "illegally and unethically."

"It's an aberration in the system," he said. "They got caught. We're glad about that."

Jennifer Bjorhus • 612-673-4683