A Portland-based aquaculture company could expand its shellfish hatchery at Harpswell’s Mitchell Field to add a kelp-growing facility, which may help reduce the amount of carbon dioxide in the atmosphere.

Running Tide Technologies is considering moving its kelp operation from Portland to Harpswell, adjacent to its existing hatchery where it hatches millions of oyster and clam seeds per year, according to a joint letter the town and company wrote to the select board. However, the company needed to change its lease with the town to gain control of a nearly 4-acre lot next to the hatchery to add a kelp facility.

The select board unanimously approved changing its lease with the company Sept. 30.

According to Running Tide’s website, the company is growing kelp that floats on the water’s surface to absorb and store carbon dioxide from the atmosphere as part of a pilot project. The company then sinks the kelp holding the carbon dioxide where it’ll remain out of harm’s way.

“Running Tide is a leading producer of Casco Bay grown shellfish with oysters and surf clams sold throughout Portland and surrounding areas,” the town and Running Tide wrote in a joint statement to the select board. “Running Tide also grows kelp for carbon removal in the offshore environment operations. Together, the company aims to scale its operations to be able to provide consumers with healthy, low-carbon proteins and make a dent in our fight against climate change.”

PORTLAND, ME – SEPTEMBER 2: Oysters are sorted by size before being bagged by 100-count at the Portland Fish Exchange. The Eastern (Crassostrea virginica) oysters were brought in by Running Tide which farms in upwellers at different locations in Casco Bay. (Staff photo by Derek Davis/Staff Photographer)

Like trees, kelp absorbs carbon dioxide — a greenhouse gas — from the air and store it in the plant itself, according to the National Oceanic and Atmospheric Administration. In fact, according to Running Tide’s website, kelp can absorb and store 20 times more carbon per acre than forest.

When greenhouse gas molecules like carbon, nitrogen and methane are left in the atmosphere, the molecules absorb and emit light, preventing some of it from escaping the Earth. That trapped light heats up the atmosphere and raises the planet’s average temperature, otherwise known as global warming.

Should the company go through with the move, Marty Odelin, owner of Running Tide Technologies, told the select board the company would construct a new building on the four-acre lot that would be “a more substantial facility…that would allow us to increase the size and scope of our operation.”

Odelin said he doesn’t have any plans for the new building, but said it wouldn’t be taller than two stories. He added he doesn’t know when construction on a new building would begin, but said “It would be optimistic for me to say this would start in the next year.”

“COVID has caused a lot of delays for us in our business plans,” he said. “If we were to start construction, it would be in the off-season of activity (in Mitchell Field.)”

Though the select board has approved the lease change, any plans for new buildings would need to go through the town’s planning board.

The revamped 10-year lease comes with a monthly price tag of $4,770, totaling about $58,000 a year, which will increase 3% each year, according to Harpswell’s Business Negotiator Steve Levesque.

“When I look at the big picture, this is a really cool business and I think it’s a good fit for the Marine Business District in Harpswell,” Levesque told selectmen last Thursday. “It’s exciting what they can do and it’s cool that it’ll be based in Harpswell.”

Running Tide Technologies did not return requests for comment Monday.

When Running Tide’s oyster hatchery first opened, the company renovated a pre-existing building leftover from Mitchell Field’s days as a former Navy site.

Mitchell Field sits on 112-acres on the west side of Harpswell Neck Road that served as a former fuel depot for the Brunswick Naval Air Station. The depot closed in 1992, and Harpswell acquired the land in 2001.