BECKER, Minn. — Northern Metal Recycling, a massive metal shredder, settled in this town between the Twin Cities and St. Cloud after being chased out of Minneapolis by the state. Despite its history, company executive Scott Helberg says the facility is on the leading edge of pollution control.

The biggest shredder in Minnesota, it crushes up to 350 tons per hour of cars, appliances and other sources of reusable metal. Shredding the scrap metal risks fouling the air with a range of pollutants, including particulate matter or soot, toxic volatile organic compounds (VOCs) and mercury. Northern Metal funnels its air through two filters and a special heater and plans to add a new system to control acid gases.

Even so, Northern Metal recently was fined $12,000 by the Minnesota Pollution Control Agency for submitting emissions tests late and for exceeding its limit for soot. That came after a long history of operating problems, including fires and pollution violations in north Minneapolis, that triggered neighborhood opposition and a state investigation that found falsified emissions records.

Helberg, the chief operating officer for parent company EMR, says his plant follows the strictest air rules of any shredder in Minnesota, and the competition should be on a level playing field.

Now, state regulators say they're investigating air pollution at every metal shredder in Minnesota, an inquiry that the MPCA started a little over a year ago. Officials did not say what spurred their newly revealed investigation, except that regulators focus on specific industries when new information or new technology warrants it.

"How we looked at things five years ago might not be how we look at them today," said Rachel Studanski, a supervisor in the air compliance unit at MPCA.

No other metal shredder in Minnesota is capturing its air in a building, let alone filtering it, and all have a less-restrictive air permit than the plant at Becker. One metal recycler, in New Ulm, has been at the center of several recent complaints from neighbors.

Helberg says the costs to install and run Northern Metal's air system have limited what it can pay to the haulers that bring in scrap.

"If you have regulation and it's not equal across the board ... is that right, or is it wrong?" he asked.

The Environmental Protection Agency flagged the metal recycling industry in 2021 as one that could be under-reporting emissions, particularly VOCs, which can come from vaporized motor oil.

In response to interview requests, Crow Wing Recycling, which owns shredders in Ironton, Brainerd and New Ulm, and Alter Trading Corp. in Anoka sent statements asserting that they had cooperated with MPCA's requests for information and that they comply with their air pollution permits.

The other two shredders included in the investigation, Bayside Recycling in Duluth and AMG Resources in St. Paul, did not comment after multiple phone calls.

While the Becker site is the largest in the state, Studanski said the MPCA wants to know exactly how much material the other shredders can handle. On average, the shredder in Anoka handles 80 tons an hour, according to Sarah Schlichtholz, a vice president at Alter. That's less than a quarter of Northern Metal's top capacity.

The numbers matter because potential emissions at each site determine what permit shredders receive. A less restrictive registration permit requires shredders only self-report emissions annually, while an individual permit is a part of the federal Clean Air Act and can include many additional pollution controls, which are specific to each location.

Under a registration air permit, it's not required to track whether cars are drained of oil, or whether mercury switches are removed before crushing. At Northern Metal, the individual air permit requires all the cars received be numbered and logged, and a few in each load are checked to make sure polluting components have been removed, Helberg said.

Individual permit holders usually are inspected more frequently, but other factors can bump a site up the list. Four shredders are in Areas of Environmental Justice Concern, meaning they're in neighborhoods with higher numbers of poor people or people of color.

Helberg said he has tried for years to convince state regulators that other shredders should have individual permits like his facility's. He's hired photographers to take pictures from planes flying over his competitors, showing that the other facilities are open to the air.

His firm has also sent letters threatening to sue Crow Wing for violating the Clean Air Act at its newest shredder in Ironton. Crow Wing responded in its own letter that it didn't emit enough to warrant a tighter permit, according to a copy provided by Helberg. The company did not address the legal threat in its statement.

But the target of potential litigation is in question: "should we be suing the competitor or the [MPCA]?" Helberg said.

A lack of air capture at most Minnesota shredders means they can't filter out any airborne pollution. It also makes it hard to test for emissions in the first place.

MPCA sent a letter to shredders around the state as part of its investigation last March, asking that they sample their air within 60 days. But without controlling the flow through vents or other enclosures, doing such a test would be "difficult, if not impossible," said Jared LaFave, a supervisor in the air quality permit section at MPCA.

The alternative is to rely on results from similar facilities around the country, or on data provided by the industry to estimate emissions, LaFave said.

The agency also responds directly to complaints, but Studanski declined to offer any details about recent enforcement moves.

At least one other shredder has recently attracted the ire of its neighbors.

A shredder has operated in New Ulm for years, but it was purchased by Crow Wing roughly 18 months ago. Since then, complaints over noise, vibrations and lingering smoke have increased, the New Ulm Journal reported in November.

Two neighbors and a city official confirmed the site is now shredding far more often than it used to, usually five days a week.

Joe Johnson lives next to the shredder in the house he grew up in and later bought from his parents. Johnson said in an interview that he and his wife are debating whether to leave the home because of the smoke and noise from the metal recycler. His children won't play outside when it's running because of the noise. At times, powerful vibrations have made him worry his windows would shatter.

"I don't think homeowners should have to live next to something like that, especially when they don't know the health hazards," he said. "The more and more I read about airborne particulates, the more it scares me."

Frank Rod Miller, who lives on the other side of the facility, said some of the smoke from the shredder has been yellow- or orange-colored in recent months.

Crow Wing said in its statement that it welcomed "open, transparent dialogue" with neighbors in New Ulm and that it "invested more than $1 [million] dollars on improvements ... to match the needs of the community, its citizens and our business growth."

Chris Dalton, the city manager at New Ulm, said the company had installed rubber mats to try to muffle some of the noise. He also said that the shredder passed noise testing by the city in January and is in compliance with ordinances for both noise and vibration.

Complaints of smoke have been forwarded repeatedly to the MPCA, Dalton said.

"It's not a good situation, but they both [the shredder and the residents] have rights," Dalton said.