Duluth-based Minnesota Power also said Thursday it will petition the Minnesota Supreme Court to overturn a recent state appellate court ruling that could be a major setback for the Superior plant.

The Minnesota Court of Appeals last month ordered the Minnesota Public Utilities Commission (PUC) to re-examine the proposed plant's environmental effects.

The Nemadji Trail Energy Center would be built and co-owned by Duluth-based Minnesota Power and La Crosse-based Dairyland Power Cooperative. The Public Service Commission of Wisconsin voted 2-1 Thursday to approve the project.

"It passed a major hurdle today," said Julie Pierce, vice president for strategy and planning at Minnesota Power, which would take half of the plant's electricity production.

The project still needs permits from the U.S. Army Corps of Engineers, the Wisconsin Department of Natural Resources and the city of Superior. Minnesota Power expects those permits to be granted during the first quarter, Pierce said.

However, the regulatory process in Minnesota is in a sort of limbo.

Back in 2018, the Minnesota PUC voted 3-2 to approve Minnesota Power's stake in the Superior project despite opposition from a state administrative law judge and clean-energy advocates and ratepayer groups. The PUC didn't require a formal environmental review of the Superior project — a judgment that was appealed by environmental groups.

In December, the Minnesota Court of Appeals held that the Wisconsin plant is subject to Minnesota's environmental laws, ordering the PUC to further review it.

The PUC has not said yet whether it plans to ask the Minnesota Supreme Court to reverse the appellate court ruling.

It's not clear how the environmental review in Minnesota would affect construction of the Superior plant.

Environmentalists argue that the Superior gas plant isn't needed, and that adding more renewable energy would be more cost effective. The Sierra Club Thursday panned the decision by Wisconsin utility regulators, calling the plant an "environmental and economic disaster."

Minnesota Power said the Superior gas plant is necessary as the utility adds more wind and solar power and moves away from coal-fired electricity.

Natural gas plants, like coal generators, can provide constant power when the sun is down and the wind is dead. Gas-fired power plants are cheaper to operate than most coal generators, and they emit about half the amount of greenhouse gases.

Minnesota Power is Minnesota's second-largest utility with about 145,000 customers in northeastern and central Minnesota.