Duluth is ditching coal for awhile. The city-owned plant that provides heating and cooling to about 200 buildings downtown will run on natural gas instead of coal for the next seven months, Mayor Emily Larson announced Wednesday.
The city's system sends steam through 10 miles of pipes to heat the buildings. They make that steam by pulling water from Lake Superior and heating it with boilers – that run on coal.
But during their April-through-October experiment, Duluth will instead use natural gas to operate the system. Larson expects the change will lead to a 40 percent drop in the amount of coal burned this year, cutting air pollution by about 15 percent.
As MPR News explains, operators of the plant (which is called Duluth Energy Systems) will still need to use coal during the coldest winter months. But they're hoping they can skip it the rest of the year.
Reducing carbon emissions was one of the priorities Larson laid out in her recent State of the City speech. She set the goal of a 15 percent reduction during her first term.
More efficiencies planned at the plant
The city is calling the switch to natural gas a "first step" because they have other plans for making the steam plant more efficient.
One of the goals set by Ever-Green Energy, the company that operates the plant, is to use hot water instead of steam to heat the buildings in its network. Using hot water would allow the plant to serve buildings farther away from its boiler. But a city official told Midwest Energy News about another advantage, too.
In a hot water system the heat can be recovered after it passes through the buildings, in what's sometimes called a "closed system." The steam system they're using now creates condensation, which just runs into the storm sewers and returns to Lake Superior.
Larson says Duluth has asked the Legislature for $21 million to pay for converting the plant to hot water. Ever-Green Energy is already using a hot water system in St. Paul, where it runs the District Energy plant that serves hundreds of downtown buildings.