Minnesota Power announced Wednesday that it will shut down two more of its coal-fired electrical generators, Boswell Units 1 and 2 in Cohasset, as the utility continues its move away from coal.

The Duluth-based utility said it will idle the 1960-vintage units by the end of 2018 as it moves toward more natural gas and renewable energy from solar and wind generation.

The changeover is part of the utility’s long-term Energy Forward focus and helps it comply with state regulations to get more energy from renewable sources.

The move also was pushed by the state’s Public Utilities Commission, which in June ordered Minnesota Power to shut Boswell 1 and 2 down no later than 2022.

Minnesota Power originally had proposed keeping the units churning until 2024 but said Wednesday that further economic analysis showed the earlier shutdown was warranted.

The move away from coal also has been pushed by environmental groups because coal-fired power plants are among the largest sources of carbon dioxide, the greenhouse gas that scientists say is spurring global climate change. Coal also produces other pollutants, including mercury that can taint fish and make them unsafe to eat.

“Fresh Energy and our clean energy partners advocated that these units appear to be no longer economic to run, with cleaner energy available and cheaper,’’ said J. Drake Hamilton, senior policy director of Minnesota-based Fresh Energy. “We are pleased with the company’s economic decision not to wait another six years, and the several years of lead time before 2018 allows them to provide for a smooth transition for the plant’s workers to other positions at the company.”

Minnesota Power’s goal is to eventually produce about one-third of its electricity from natural gas, one-third from renewable sources and one-third from coal. While some environmental groups have pushed to eliminate coal as an energy source in the state, Minnesota Power officials say they need the 24/7/365 baseload of electricity that coal can provide at a lower cost - especially for its largest industrial customers, such as taconite plants and paper mills.

Minnesota Power made it clear Wednesday it has no intention of shutting down or repowering Boswell Units 3 and 4 in Cohasset, the utility’s largest coal-fired generators that, at 355 and 585 megawatts, respectively, are the backbone of Minnesota Power’s system. The company noted it has spent millions of dollars on Boswell 3 and 4 in recent years to comply with state and federal air pollution laws for mercury and sulfur dioxide, although the controls do not limit carbon dioxide.

Company officials made the announcement to employees Wednesday at the Cohasset facility.

Josh Skelton, Minnesota Power’s vice president of generation operations, said the decision to retire units 1 and 2 directly affects 30 employees, and the company is working to avoid layoffs through attrition and retirements.

“We will assist them, as well as the Cohasset community, to help mitigate impacts during this transition,” Skelton said.

With the Boswell units going offline, coupled with the shutdown of coal units at its Laskin facility in Hoyt Lakes and Taconite Harbor on the North Shore, Minnesota Power now has committed to taking 335 megawatts of coal-fired capacity off the grid.

“The decision to retire units 1 and 2 at Boswell, though difficult for our employees and host communities, is consistent with Minnesota Power’s Energy Forward strategy of diversifying its energy mix, reducing its carbon footprint and evolving away from smaller, older coal generators,” said Alan Hodnik, CEO of Allete, the parent company of Minnesota Power.

“Minnesota Power is responsibly answering the nation’s call to transform its energy landscape,” he said.

The utility has achieved a 25 percent renewable energy mix, well ahead of the state’s renewable energy goal of 25 percent by 2025. Minnesota Power expects to reduce carbon emissions on its system by about 20 percent by 2020 and 30 percent by 2025 compared with 2005 levels.

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