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An ethanol plant in western Minnesota has been hit with a $250,000 pollution penalty after the state said it illegally spread wastewater to fields, missed deadlines for air emissions tests and spilled beer mash and wet cake that threatened nearby wetlands.

The violations occurred from 2017 through 2022, according to the Minnesota Pollution Control Agency, which announced the civil penalty Wednesday.

The Denco II plant also agreed to train its staff, hire outside consultants to conduct annual environmental audits and install cameras to detect spills, among other things.

The farmer-owned plant in Stevens County, in western Minnesota, produces about 30 million gallons of ethanol from corn per year, which it sells primarily in Minnesota for blending into motor fuel sold at gas stations, but also elsewhere in the United States and Canada.

In a statement, Tom Miller, Denco's general manager, characterized it as a voluntary agreement and claimed there was "no harm to the community or environment."

Still, "we understand that we needed to make some leadership and operational changes to ensure that we are in full compliance with Minnesota's environmental permitting laws," Miller said in the statement. "We believe that the changes we've made to date and those planned for the future show our continuing commitment to the health and safety of our staff, our community and our environment."

He declined to elaborate on the leadership changes.

The MPCA said that Denco II had applied about 1.25 million gallons of process wastewater to nearby fields over the years without a permit, and didn't use a certified professional for the work or test the discharge or soil.

Denco had transported some of the wastewater to two manure storage sites at Riverview Dairy and Prairie Gold Farms, where it was then applied to fields, according to a copy of the settlement.

Three times in 2021 it spilled large quantities of beer mash and wet cake, both ethanol byproducts, onto the ground that ran into the plant's water drainage system and did not immediately notify the state as required, the MPCA said. The plant's drainage system empties out onto a nearby marshy area, but the spill didn't reach the wetlands.

Other violations included exceeding industrial stormwater discharge limits more than 30 times in 2021 and 2022 and missing the deadlines for testing air emissions for nitrogen oxide and particulate matter.

The MPCA has taken a number of enforcement actions against Minnesota ethanol producers over the years, particularly in the industry's early years a decade ago when "the majority" of the plants had problems complying with environmental protections, MPCA spokesman Steve Mikkelson said.

"Since then it's gotten better, but they still do crop up," he said.

Mikkelson said the largest enforcement action was in 2012 when it fined Bushmills Ethanol in Atwater $800,000 for violating air and water regulations, including discharging salt-laden wastewater into a ditch.