Mayo Clinic officials are trying to clear the air about their request to modify its emissions permit.
A request to modify the clinic’s air emissions permit filed with the Minnesota Pollution Control Agency asks to allow an increase of emissions by more than 250,000 tons per year.
The permit change request comes as Mayo prepares to update boilers and generators at the Franklin Heating Station, 119 Third Street Southwest. The plan calls for replacing four natural gas boilers with three new boilers and replacing two diesel generators at the plant.
The clinic filed a permit that outlines net emissions increases of more than 202,000 tons per year of carbon dioxide equivalents, 47 tons per year of carbon monoxide; 35 tons per year of nitrogen oxide and about 25 tons per year of fine particulate matter.
The amendment shows a net increase in emissions over the highest actual emissions from the facility over the last 10 years, according to Minnesota Pollution Control officials. The emission estimates are based on running all boilers and generators at full capacity all day, every day, over the year.
“The increase is defined as the potential to emit versus the historic actuals from the plant,” said Brett Gorden, who is responsible for energy management on the Rochester campus.
Most of the time, Mayo runs with one boiler offline in case of a surge in need. The diesel generators are mostly fired up one hour a month for testing and four hours of testing once a year. Otherwise, the most common use of the diesel is when Rochester Public Utilities, which provides electricity to some parts of Mayo, asks for energy curtailment during peak usage times.
Under the emissions amendment, Mayo’s new allowable emissions limit will be 27 percent less than its current permit, Gorden said. The new boilers will also run at a higher efficiency. Gorden said he predicts the plant to run at about 39 percent below the 10-year historic actual emissions.
Two of the natural gas boilers being replaced were installed in 1952, the other two were installed in 1967.
“They’ve run their useful life,” Gorden said.
The new boilers will run at 85 percent efficiency compared to the 67 percent efficiency of the boiler in place.
Rick Morris, Rochester clean energy organizer for Sierra Club’s North Star Chapter, said he understands the power plant will be more efficient than a first glance at the permit might indicate. However, he said he is concerned that the change carries forward commitment to fossil fuels without any public input.
To meet its downtown power demand, Mayo Clinic produces 30 megawatts of power. That’s about the size of many rural utility companies. Morris noted utility companies that are building or replacing generation capacity are required to prioritize renewable energy sources over fossil fuels under the Clean Energy First Act. As a private company, Mayo Clinic is not beholden to the requirement. Under the act, utility companies adding fossil fuel capacity need to demonstrate it’s necessary to ensure reliable, affordable electricity.
“We would like to see more transparency to see if Mayo Clinic did the same due diligence a small-town utility would have had to do,” Morris said.
Gorden said generating that much power in a downtown setting eliminates most conventional renewable sources. The Damon Parking Ramp downtown has solar panels on the roof that generate 145 kilowatts of power — about enough to power the building most days. To meet Mayo’s downtown needs, they would need about 200 more of those.
“That’s a lot of solar panels,” Gorden said.
The natural gas boilers are the most efficient way to generate the needed power in the given space, he added.
Morris said that even if that's the case, the decision still affects the health and air quality of downtown.
“We think the public at least deserves to be a part of that discussion,” he said.
The boiler system is also a combined heat and power system that captures the heat that would otherwise be wasted to provide steam energy that can be used for space heating, cooling and hot water generation.
To help offset continued use of fossil fuels, Mayo is working to make more efficient use of the energy it generates, said Amanda Holloway, Mayo director of sustainability.
In October 2017, Mayo met a goal to reduce energy use by 20 percent from 2010 to 2020, Holloway said. Now Mayo has its sites on 30 percent by 2025.