State regulators rule that burning trash and wood can be considered 'carbon-free'

Burning trash and wood to generate electricity will now be considered as a carbon-free source under Minnesota’s landmark clean energy law, after a decision by state utility regulators following a contentious hearing Thursday.

The law that passed in 2023 requires 100 percent of electricity produced in Minnesota to be generated from carbon-free sources by 2040. The goal was to significantly cut the amount of greenhouse gases the state emits, which contribute to global climate change. 

But the law didn’t specify which power sources would qualify. Instead, the legislation defined “carbon-free” as “a technology that generates electricity without emitting carbon dioxide.” Lawmakers left it up to the Minnesota Public Utilities Commission to determine what meets that definition. The commission has held a series of proceedings in the years since the law passed to hash out how to implement the new law. 

Technologies like wind and solar are straightforward. They produce electricity without generating any greenhouse gas emissions. 

What’s proved controversial is deciding how to treat power plants that burn municipal waste or wood waste, which generate significant amounts of greenhouse gas emissions. 

But those materials can also contribute to climate change even if they aren’t burned to create electricity. For example, wood scraps left to decompose release carbon dioxide. Trash that’s landfilled releases methane, a potent greenhouse gas. That’s why some argue that burning wood and trash for power is still environmentally beneficial.

In a raucous meeting Thursday that was twice interrupted by protestors, the five members of the state PUC ruled that facilities that burn municipal waste or biomass to generate electricity can still be considered carbon-free, even if they emit large amounts of carbon dioxide or other greenhouse gas emissions. 

They can do that if they pass a life-cycle analysis that proves that burning trash or biomass in that facility generates fewer greenhouse gases than what would most likely occur if the wood or waste were disposed of in another manner. 

Commissioner Audrey Partridge described a hypothetical example of a Minnesota county that collected wood waste from forests damaged by storms and insects. The county recycled 10 percent of the wood and burned the rest so the pest infestation wouldn’t spread, resulting in the release of 100 tons of carbon into the atmosphere. 

A utility wanted to instead burn that wood in a biomass power plant. If a life cycle analysis found that would release fewer than 100 tons of carbon, then that would be considered “carbon-free” under state law. 

“If taking this waste and using it to generate electricity provides a climate benefit, then it should qualify,” Partridge said. “I believe that this is the best path for implementing this law and for improving the climate.”

But several environmental groups and attendees in the audience strongly disagreed. The meeting was disrupted twice, with people repeatedly shouting, “This is not the bill the people passed!”

DFL State Sen. John Marty of Roseville co-authored the 100 percent clean energy bill and addressed the PUC during their meeting Thursday. He was one of 42 legislators who wrote a letter to the Commission, urging them to not consider fuels such as biomass and waste incineration to be considered carbon-free under the law.

“I urge you to follow the plain wording of the law and the vision the legislature showed in 2023,” Marty told the commissioners. “It's not ambiguous.”

“I know you're looking at the life-cycle analysis,” Marty continued. “But I would suggest that if the legislature wanted a life-cycle analysis, we could have done so.”

Only about 2 percent of the electricity generated in Minnesota comes from biomass and trash incineration. But environmental groups worry that this decision will lead to an increased use of incinerators to generate power, increasing the amount of greenhouse gases and particulate matter pollution emitted into the atmosphere.

“It's possible that some of our biggest coal plants will be converted to partially burn trees, which is terrible for the environment, and it's just a huge step backwards from the law that was passed in 2023,” said Hudson Kingston, legal director for the environmental group CURE. 

Hudson said biomass and waste to energy plants should instead be compared against solar and wind projects, which don’t emit any greenhouse gas emissions. 

Duluth-based Minnesota Power told the PUC it is considering converting part of the Boswell coal-fired power plant in Cohasset to biomass when that coal facility closes in 2035. 

The utility also operates a biomass plant in Duluth that generates about 1 percent of all the electricity it produces. “But it serves an important purpose in terms of reliability and also serves northern Minnesota by providing a safe and sustainable place to dispose of diseased wood and storm debris,” said Minnesota Power spokesperson Amy Rutledge. 

The utility said it looks forward to working with state agencies on a life-cycle analysis of the facility. 

Community advocates voiced concern that the burning of trash at the Hennepin Energy Recovery Center, or HERC, a controversial waste incinerator in downtown Minneapolis that neighborhood activists have tried to shut down for years, could still be allowed to qualify as carbon-free under the PUC’s decision. 

“We don't have any faith,” said Nazir Khan with the Zero Burn Coalition in Minneapolis.

But commissioners Joe Sullivan and Audrey Partridge said the state Legislature has already determined that electricity produced at the HERC cannot be considered carbon-free. The PUC reaffirmed that portion of state law in its decision.

The decision could be the subject of litigation. The Minnesota Center for Environmental Advocacy, which has sued over the issue before, said it’s still regrouping after the PUC decision to determine its next steps. 

Editor's note (Feb. 4, 2026): An earlier version of this story suggested the Hennepin Energy Recovery Center could qualify as “carbon-free” under a recent Public Utilities Commission ruling. To clarify, state law doesn't allow electricity generated by the HERC waste incinerator to be considered carbon-free.

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