Beneath the ground people walk on is a large network of pipes. These pipes, out-of-sight and seemingly innocuous, have contributed a startling amount of methane gas to the atmosphere, according to a study published Jan. 22 in the Proceedings of the National Academy of Sciences.
Scientists from Boston University, Harvard University and Stanford University found that 2.7 percent of natural gas transmitted and distributed in eastern Massachusetts seeped from the gas infrastructure. Nathan Phillips, one of the authors of the study and a professor of earth and environment at Boston University, said an estimated 10 percent of total greenhouse gas emissions in Massachusetts can be attributed to natural gas pipeline leaks.
Previous research conducted by Phillips, which detected over 3,000 gas leaks in Boston, served as a precedent for this follow-up study on methane emissions.
“That work was the discovery of the thousands of pipeline leaks. These are the pipelines that are underneath the street sidewalks that’s providing the natural gas from our homes and businesses for heating and hot water,” Phillips said. “As any valuable research does, it raised more questions than it answered … What are the safety implications for explosions? What are the other impacts on air quality? What about the damage to the trees? The questions provided impetus to do a follow-up study.”
Phillips and his colleagues used sensors to measure the net buildup of methane. From 2012 to 2013, they collected data from sensors at Copley Square, Boston University, Nahant and the Harvard Forest in Petersham.
“A few strategic locations up in the air, like on top of a tall building, provide a nice measure. You measure the pulse of a person on a part on their wrist, that tells you something about their whole body,” Phillips said.
One of the drivers of methane leaking from natural gas pipelines is the aging infrastructure, said Steven Wofsy, another author of the study and a professor of atmospheric and environmental science at Harvard.
“Many of the gas pipes are from the 19th century, 20th century, if you can believe it. There’s thousands of miles of cast iron pipe, and each segment is 16 feet long,” Wofsy said. “Also, cast iron is brittle.”
Though a significant contributor to emissions, gas leaks do not paint the entire picture, Wofsy said.
“Another major source that we know something about is industrial facilities … those devices also deliver gas in the atmosphere. You have a variety of things that can happen, the more unknown unknowns, appliances like your gas furnace or stove,” he said. “And then some other strange things … if I go to the subway system, it is not uncommon to find higher levels of methane. When we look for traces of natural gas, like sewage, methane is down there too.”
Nonetheless, Phillips said, the leaks need to be patched immediately.
“Natural gas is a fossil fuel. It’s a huge benefit to patch the leaks because one molecule of methane is 34 times as powerful as a corresponding molecule of carbon dioxide, if it leaks to the atmosphere,” Phillips said. “We found that 2.7 percent of all natural gas consumed in the study region was leaked. We have to address that problem and stem those leaks. That’s not a choice. That’s an imperative.”
While it may be an imperative to stem the leaks, policymakers are faced with a different choice — whether or not to continue using natural gas for energy resources.
Lisa Tornatore, sustainability outreach coordinator for sustainability@BU, said scientists and policymakers need to cooperate to achieve the goal of emissions reduction.
“It is certainly concerning to hear that natural gas leaks are higher than previously estimated. Methane is a powerful greenhouse gas, more so than carbon dioxide, so it has implications for increased greenhouse gas concentrations in the atmosphere,” Tornatore said. “Researchers from BU and other universities work closely with the City of Boston and the Commonwealth [of Massachusetts] to bring to light issues like this one so that our lawmakers and utility companies can make improvements quickly and efficiently.”
In the meantime, Phillips said, everyone else needs to consider whether or not gas is worth the risk.
“We really need to think carefully about our reliance on natural gas. Are we using natural gas, are we doubling down on it to stay committed for decades to come?” Phillips said. “Our study really presents us with a choice.”
