'Big, bold idea': Duluth hopes to heat homes with wastewater energy

a woman speaks in front of a podium
Duluth Mayor Emily Larson discusses a $700,000 grant on Tuesday the city will use to design a system that would use wastewater energy to heat the Lincoln Park neighborhood.
Dan Kraker | MPR News

The city of Duluth has received a major federal grant to design a system that would use leftover energy from a wastewater treatment plant to heat hundreds of buildings in the burgeoning Lincoln Park neighborhood.

The proposal is referred to as a geothermal heating district, but don’t think of geysers like Old Faithful. It wouldn’t harness the energy in underground pools of hot water and steam that exist naturally. 

Rather, the project would use waste heat captured from effluent at the nearby Western Lake Superior Sanitary District to heat about 2.4 million square feet of buildings in the area west of downtown, which has boomed over the past decade with the construction of breweries, restaurants, shops and apartment buildings.   

Over the next year, the $700,000 grant will be used to analyze the technical and economic feasibility of creating the system, which would take 95-degree water from the treatment plant, bump up the temperature to around 130 degrees and pipe it using heat pumps to Lincoln Park, and potentially to additional buildings downtown. 

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In layman’s terms, “this technology will use pumps to move heat around, instead of using fossil fuels to gain heat,” explained Duluth sustainability officer Mindy Granley. 

It’s a “big, bold idea” that has potential to be “a model for the nation,” said Ken Smith, CEO of Ever-Green Energy, which will lead the study. “You’re using heat that’s already available to meet the heating needs of a community,” he added. 

Smith said there are only a few projects like it around the world: three in Finland, three in Sweden, and one in China. 

“As far as tapping into the waste heat at a wastewater treatment plant and using that to serve a community, that does not exist in the United States,” Smith said. 

Duluth is one of 11 communities nationwide to receive a planning award from the U.S. Department of Energy, joining other cities including Chicago and New York. 

Advocates say the time is ripe for such a transformative project because of the impending reconstruction of West Superior Street, the main thoroughfare through Lincoln Park. 

The city was recently awarded a $25 million federal grant to completely rebuild a 2-mile stretch of the roadway, which will include replacing all the underground utilities, such as water, sewer and stormwater. 

Smith estimates a 40 percent cost savings from building a geothermal project at the same time the street is getting rebuilt, which is forecast to start in 2026. 

“The West Superior grant is the catalyst that makes this possible,” Smith said. “You’re already going to be disrupting this neighborhood, opening up this infrastructure.” Together with the proximity to WLSSD, “everything is aligned to really make this transformative project possible.”

Smith estimates the overall cost of a project to be in the “tens of millions” of dollars. It will require new infrastructure to transport the hot water and connect it to the existing heating systems in hundreds of buildings. 

The federal government could potentially pay up to 90 percent of the cost, said Jodi Slick, CEO of the Lincoln Park-based nonprofit Ecolibrium3 and the project’s co-leader. After 11 months of study, the city will submit its design to the government for potential funding, she said. 

Slick is most excited about the potential to create an environmental justice model that could be duplicated nationwide.

Many of the nation’s more than 16,000 wastewater treatment plants are located near low-income neighborhoods like Lincoln Park. Those plants are often viewed as environmental burdens, but this effort could benefit communities, Slick said.

“We have the ingredients that we need to look at really creating a national model for how you can take energy that already exists in the community and apply it in a really smart way that has economic and environmental benefits,” said Slick.