With New Tools, A Focus On Urban Methane Leaks

Until recently, little was known about the extent of methane leaking from urban gas distribution pipes and its impact on global warming. But recent advances in detecting this potent greenhouse gas are pushing U.S. states to begin addressing this long-neglected problem.

Battered by storms and weakened with age, the natural gas distribution pipes of urban New Jersey have long been in need of repair. And for a long time, the state’s largest utility, Public Service and Enterprise Group (PSE&G), has wanted to replace them. The problem is that pipelines cost upwards of $1.3 million per mile, and the utility owns 4,330 miles of them. Replacing it all would cost at least $6 billion, not to mention decades of work.

Jukka Isokoski
Workers install a natural gas pipeline.

In December 2014, however, the Environmental Defense Fund (EDF) approached the utility with a solution. Using new technology that can trace methane emissions back to their sources with great precision, researchers could home in on the highest-risk pipes, allowing the utility to prioritize repairs along the worst offending lines. 

EDF and its collaborators, from Colorado State University and Google Earth Outreach, then spent six months gathering data the utility could use.

The state’s Board of Public Utilities, which determines how much money PSE&G can raise from its customers and how it can spend it, had earlier rejected a request from the utility to raise $1.6 billion for 800 miles of new pipeline. But after the results of the monitoring effort were in, the utility narrowed its request to 510 miles of pipeline replacement, at a cost of $905 million over three years. Work on the project begins this month.

This collaborative effort in New Jersey is one of numerous initiatives underway in the United States to drastically reduce fugitive methane emissions from natural gas infrastructure in urban environments. Utilities want to reduce those emissions mostly out of concern for safety: The U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration reports 45 incidents within New Jersey’s natural-gas distribution network alone over the last 20 years — five of them deadly. But leaks also cost money. In the city of Boston, where several studies have observed high concentrations of natural gas in the atmosphere, an estimated $90 million worth of natural gas escapes every year from faulty pipes, an expense local utilities pass on to consumers.

For environmentalists, however, even small fissures in natural gas pipelines are a cause for alarm, because methane is a potent greenhouse gas. Methane doesn’t persist as long in the atmosphere as does carbon dioxide, which lasts for centuries. But in the 12 to 14 years that it lingers, methane traps heat at least 30 times more efficiently than does carbon dioxide. Which means that many small natural gas leaks — too small to cause safety problems — can pose a serious risk to the climate.

Those many otherwise minor leaks have been accumulating at an accelerating pace, not just in Newark, New Jersey — the most leaky city in PSE&G’s territory — but along gas distribution lines in Los Angeles, Boston, Baltimore, and all five boroughs of New York City.

Natural gas escapes into sewer lines and buildings, rides up ventilation shafts, and descends into subways.

One recent study found leaks in Manhattan occurring at a rate of 4.25 per mile — a nearly 10 times greater leak density than the same study found in Cincinnati, Ohio, where Duke Energy addressed the problem with a recently completed, 15-year, $1 billion project to replace old cast-iron pipes with reinforced steel. In a landmark street-level analysis of Boston’s natural gas leaks published in 2012, researchers found that the city loses nearly 3 percent of its supply through cracks in its aging pipes. A subsequent Harvard University study, which sampled air from rooftops in the Boston area from 2012 to 2013, revealed atmospheric methane concentrations two to three times higher than previous estimates, amounting in total as enough to heat 200,000 homes, according to the study’s authors.

Methane leaks from gas pipelines are just one source of global methane emissions from human sources that are of increasing concern to climate scientists. Last October, a wellhead failed at an underground natural gas storage site on the northern edge of Los Angeles called Aliso Canyon, causing a massive release of its contents. By the time the well was capped on February 18, it had spewed 105,822 U.S. tons of methane into the atmosphere, the climate equivalent of carbon dioxide emissions from 900 million gallons of gasoline. In the U.S. and around the world, methane also escapes from landfills, from compressed natural-gas filling stations, and during oil and gas extraction and transmission.

Gas distribution pipelines, which begin at what engineers call the “city gate” and deliver gas to homes and businesses, are different from gas transmission pipelines, which carry natural gas from production fields to distribution hubs. Gas flows through distribution pipelines at relatively low pressure, and they’re closer to the surface, only two or three feet deep. Their maintenance is up to the utilities that own them, and regulated by the states. So even though leaks from the older ones threaten to take a serious bite out of federal efforts to slow the pace of climate change, the federal government can’t do much about them. The problem is that states haven’t either. Like the utilities, regulators and state legislatures haven’t monitored for tiny but climate-harming leaks, concentrating instead on immediate safety issues involving larger leaks that could combust.

Boston has methane leaks (the yellow and orange dots) every mile. View more cities.

Photo: EDF

“The current regulatory framework in most states doesn’t recognize distribution leaks as an environmental problem,” says Simi Rose George, a regulatory affairs expert with EDF. “That’s something we think needs to change.”

The first step toward that change has been to find out just how much natural gas emits from city pipelines, and where. But measuring methane in cities is hard, says Rob Jackson, an environmental scientist at Stanford University who, with Boston University’s Nathan Phillips, worked on the first block-by-block city analysis of methane leaks five years ago in Boston. “It’s not like measuring methane at oil and gas production facilities,” Jackson says. “You can’t see it at a distance with an infrared camera.” Natural gas also moves around. “When cars zip by, the gas goes up and down and sideways.” It escapes into sewer lines, into buildings, rides up ventilation shafts, and descends into subways.

The utilities themselves have typically compared what comes in at the city gate with actual deliveries to consumers to arrive at a figure for lost gas. That’s in part because you don’t need precise measurements to detect a combustible amount of natural gas in the air; since odorants are added at the city gate, it just takes a nose. But it’s also because, until recently, the technology to quantify leaks with any precision wasn’t yet on the market. The industry’s standard methane detector has long been a handheld box with a wand you wave around in the air, something like the ghost-detecting prop in the Ghostbuster movies. “It’s only semi-quantitative,” Phillips says. “You don’t look at it and say, ‘We’ve got 4.1 parts per million in this spot.’ You can only say, ‘We’re getting gas.’”

That changed in 2010, when Picarro, Inc., a technology company based in Santa Clara, California, unveiled a special kind of sensor, called a “cavity ring-down spectrometer” to detect atmospheric concentrations of greenhouse gases in finer detail than ever before.

If utilities fix gas leaks for environmental reasons, they can catch leaks decades before they have a chance to explode.

The Picarro instrument draws air into a partial vacuum and reveals its precise chemical makeup with a laser pulse that pings off mirrors. The process slows down, or decays, depending on what kind of gas is in the chamber.

“It’s like a ping pong ball bouncing around,” Phillips says. If it’s bouncing around in plain air, it keeps bouncing for a while. “But if it’s bouncing around in molasses, it’s going to slow down.”

Phillips, a tree physiologist, became fascinated with the technology and its possibilities as a mobile device that could be attached to cars and produce spatial renderings of possible pipeline corrosion. “It’s one thing to smell a leak as I’m walking by someplace, and report it to the gas company,” Phillips says. “That’s just an anecdote.” It’s another to see all of those anecdotes mapped. “Then everyone can see the scope of the problem.”

Phillips thinks the work he and Jackson pioneered was probably inevitable; if they hadn’t done it, someone else would have. “It’s the natural outcome of mobile networks and sensors and spatial information,” he says. Nevertheless, it’s become the model for several other mapping projects, including EDF’s collaboration with Google Earth Outreach and Colorado State University.

That effort has now mapped segments of the Los Angeles metropolitan area, along with Boston, Chicago and Indianapolis, outfitting Google Street View cars with Picarro sensors, wind gauges, and GPS. It has revealed what might be considered an obvious trend, but one that nevertheless proves a point: Cities whose infrastructure haven’t been shored up in the last half century lose natural gas from their pipelines at higher rates than cities with newer pipeline infrastructure.

The natural gas escaping from pipelines in Massachusetts accounts for 10 percent of the state’s greenhouse gas emissions.

“We think it’s a compelling tool to help regulators assess the need for pipeline replacement programs,” says EDF’s George. She notes that if utilities fix gas leaks for environmental reasons, they can catch leaks years, even decades, before they ever have a chance to ignite and explode.

Five years ago, an explosion in San Bruno, California that killed eight people and leveled 38 homes was traced back to a faulty weld in a steel natural gas pipeline owned by Pacific Gas & Electric, a large for-profit utility that serves parts of Central and Northern California. In addition to the tragedy of lost lives and a neighborhood destroyed, the accident cost the utility dearly in fines and legal fees: California regulators hit the utility with a $1.6 billion fine for the negligence that caused that accident. The California utility later became the first in the nation to employ the Picarro sensor to detect even the most miniscule methane emissions from its pipelines.

The Southern California Gas Company, too, might have benefitted from better leak detection technology at its Los Angeles underground storage well field, where the four-month leak issued more methane into the atmosphere than any other such event in U.S. history. Just the expense of moving residents out of the Porter Ranch community adjacent to the storage field will run into the tens of millions of dollars. The Los Angeles County district attorney has filed criminal charges against the utility, and personal-injury lawyers swarming the incident are just getting started.

More proactively, the Picarro sensor’s detailed findings, combined with the vivid maps the street car projects generate, have begun to move lawmakers in certain more environmentally progressive states to consider the climate impact of natural gas distribution system problems.

New Jersey legislators introduced a bill in February that would require utilities to quantify and repair leaks for environmental reasons, modeled on a law Massachusetts passed in 2014.

California legislators passed a similar law that same year, out of concern that the state’s efforts to promote renewable energy were being undercut by natural gas pipelines losing methane into the atmosphere as they deliver supplies to the state’s consumers. In late March, state regulators considering how to implement the law proposed requiring all utilities to monitor their natural gas distribution lines using mobile sensors mounted on cars.

Nathan Phillips thinks California officials are right to be worried. In Massachusetts, he says, the amount of natural gas escaping from pipelines might account for as much as 10 percent of the state’s greenhouse gas emissions inventory. “Ten percent,” he says. “That to me is a big number. Because it was something we had not even included. It was a complete element of the pie chart that wasn’t ever in the ledger. Now it is.”