Duluth's steam plant is expected to burn 20,638 fewer tons of coal this year, thanks to the installation of new controls that will allow two of its four boilers to run on natural gas.

Duluth Mayor Emily Larson hailed the development during a press conference at the steam plant Wednesday and announced: "Today is the first day in which we are going coal-free in a pilot program here down at Duluth Steam."

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Plans call for the plant to run exclusively on natural gas from April to October. But it will revert to coal during the winter months, as that fuel remains a more economical option during periods of peak demand.

Nevertheless, operating with natural gas the rest of the year is not expected to drive up rates for the 200-or-so downtown businesses that receive service from the steam system.

"We expect the pilot project to be cost-neutral for our customers," said Ken Smith, CEO of Ever-Green Energy, which runs Duluth's steam plant.

The seven-month switch is expected to reduce the plant's greenhouse gas emissions by 13,050 tons - the equivalent of taking about 2,500 vehicles off the road for a year.

In her "State of the City" address, which she delivered in March, Larson set a goal to reduce emissions of greenhouse gases from city operations by 80 percent by 2050.

Larson pledged to achieve a 15 percent cut by the end of her mayoral term in 2020, and she predicts the changeover at the steam plant will get her two-thirds of the way toward that goal by trimming the city's emissions by an estimated 10 percent.

"This is very intentional that we are charting this course, because we think the numbers matter," said Larson, noting that the city has a responsibility to be a good steward.

Besides cutting carbon emissions, Alex Jackson, Duluth's energy coordinator, said that burning natural gas in lieu of coal at the plant will release less mercury, sulfur dioxide and nitrogen oxide into the atmosphere.

During the seven months of the year when the plant eliminates coal from its diet, its baghouse can be idled. The baghouse, which captures coal particulate matter before smoke leaves the stack, is the plant's biggest energy hog, and it won't be needed while boilers are running on natural gas.

The plant also will be able to shut down its ash-handling equipment.

All told, those operations account for about 70 percent of the plant's electrical demand when it's running on coal, said Ken Smith, CEO of Ever-Green Energy, which runs Duluth's steam plant.

Over the course of the year, the plant expects to trim 878,000 kilowatt hours from its power bill - reducing the plant's annual power consumption by 34 percent.

The conversion to natural gas this year also will eliminate the need for 826 trucks delivering coal to the plant, as well as 35 trucks hauling ash away from it. Larson noted that having fewer of those 25-ton trucks on the road will not only reduce operating costs but also will result in less wear and tear on city streets.

Meanwhile, Duluth continues its efforts to secure $21 million in state bond funding to replace downtown steam pipes with a more efficient, closed-loop system that would instead circulate hot water.

If Duluth can garner funding for the project, Montgomery promised more progress toward reducing the city's carbon footprint.

"What that will do is additionally impact our use of coal by making the system more efficient and less fuel-intensive. So we'll be able to continue to reduce our reliance on coal," he said.

Win or lose, Montgomery believes the city's efforts to replace coal with natural gas through the new pilot project demonstrates its serious commitment to improve operations.

"This shows we aren't standing still waiting around for the Legislature. We are doing those things that are necessary to upgrade, modernize and improve the efficiency of this plant and to increase our resiliency and to reduce our environmental impact. We're doing those things anyway," he said.