PEMBROKE — In a patch of woods beside manicured lawns, a small metal stump poking out of the earth was silently and invisibly leaking methane, a potent greenhouse gas.
The natural gas oozing from an underground utility line in this quiet suburb south of Boston is one of the roughly 16,000 such leaks in Massachusetts — emissions that have long vexed environmental officials seeking to curb the state’s contribution to climate change.
But a crew from Columbia Gas that came to repair the leak on a recent morning brought a new tool to the often Sisyphean task of patching up the utility’s network of aging pipes: the FluxBar.
The high-tech device, the product of a rare partnership between environmental advocates and the state’s gas companies, was designed to allow crews to more easily pinpoint the location of methane leaks, and more importantly, accurately determine how much of the gas is being released. Methane is considered about 25 times more powerful than carbon dioxide in trapping heat in the atmosphere.
“This is groundbreaking,” said Dan Cote, vice president of pipeline safety at NiSource, the parent company of Columbia Gas, at a recent meeting with environmental advocates at MIT.
Utility officials and advocates hope the FluxBar, which looks like a cross between a tuning fork and a metal detector, will solve a problem that has long pitted them against each other.
For years, the utilities have focused their maintenance efforts on plugging leaks that pose an immediate safety concern, while rarely addressing their environmental consequences. Massachusetts has among the nation’s oldest, leakiest natural gas pipes.
Now, with estimates showing that just 7 percent of the state’s gas leaks are responsible for about 50 percent of their total emissions, the state is putting pressure on the utilities to plug the largest leaks, known as “superemitters.”
Last week, the Department of Public Utilities held a public hearing on how to implement a new law that requires the utilities to “establish specific criteria for the identification of the environmental impact of gas leaks.”
Columbia Gas owns eight FluxBars and expects to expand their use next year as its crews perform maintenance and plug leaks along its 5,000 miles of pipelines in Massachusetts. The company has about 3,000 known leaks in its system.
“This is helping us tremendously,” said Marty Poulin, manager of regulatory affairs at Columbia Gas, which serves 314,000 customers in the southeastern part of the state.
Poulin and other utility officials thanked environmental advocates for drawing their attention to the problem and pressing them to find a solution.
At Eversource Energy, which has about 3,900 known leaks across its nearly 3,300 miles of pipelines in Massachusetts, officials said they have been encouraged by their tests of the device.
“It’s simple, measures properly, and it’s something that we’re all comfortable using, without spending a lot of money,” said Kevin Kelley, the company’s vice president of gas operations. “The environmental groups really opened our eyes to this issue, and we all believe this is the best way to identify the higher-emitting leaks.”
The idea for the FluxBar was sparked by steady criticism from environmental groups frustrated with the traditional approach of finding leaks, a laborious process that involved boring holes into the ground and using a monitor to locate the source of the gas. The method didn’t measure how much gas was escaping.
After a long lobbying campaign, environmental groups persuaded the utilities to try a new approach that would allow their crews to identify leaks that have spread more than 2,000 square feet. With the help of MIT students at a hackathon and a company in Hopkinton that makes similar devices, the first FluxBar was built in March, at a cost of about $1,000 apiece.
“My hope is that the gas utilities will have a better understanding of their distribution systems, and with that should come an efficiency of repairs that will help to save both the environment and ratepayer dollars,” said Brian Ferri, president of Millibar, the company that has manufactured 16 of the devices since March.
For environmental advocates, who have also criticized the utilities for how they report leaks, the gas companies still must prove that they will actually use the findings of the FluxBars to patch their larger leaks.
“The utilities now have to act on the information,” said Audrey Schulman, president of the Home Energy Efficiency Team, or HEET, a Cambridge nonprofit that helped develop the device.
The state’s three largest utilities — Columbia Gas, Eversource, and National Grid — have agreed to use the device next year on “randomly selected large volume leaks,” she said.
“My hope is that the FluxBar will make it possible to reduce the problem, at the least cost and disruption,” she said.
Kesley Wirth, founder of Mothers Out Front, a Boston-based environmental advocacy group, acknowledged that the utilities face many “competing pressures” that “don’t necessarily align with a commitment to fix the largest gas leaks.”
“In this context, the utilities have been working with us with surprising good will,” she said. “The collaboration has been impressive.”
Off Elliot Street in Pembroke, where neighbors have become accustomed to the odor of rotten eggs from the nearby leak, the Columbia Gas crew fenced off a large area and dug 19 holes in the ground.
With another device, they identified the hole closest to the leak, where they inserted the FluxBar. They took a series of readings, which found that about 20 percent of the soil had been saturated with methane.
It would take more calculations back at the office to figure out how much gas was escaping.
Rather than waiting, the crew dug through rock and past cable lines until they exposed the leak, then sealed it.