Clearer view of risky leaks from gas mains in Boston

raise warning signs for climate change. Methane accounts for about one tenth of U.S. greenhouse gas emissions. On average over a 20-year period, a methane molecule released into the atmosphere traps about eighty-six times as much heat as does a carbon dioxide molecule, Phillips points out.

“We know we have a problem with aging natural gas infrastructure, but we need a better understanding of how big the problem is and the best ways to solve it,” Hendrick says.

One major issue is a lack of agreement on the number of gas leaks. For instance, Phillips led a 2013 survey on all Boston city roads that found 3,356 gas leaks. The most recent estimate from an annual report filed by National Grid with the Massachusetts Department of Public Utilities (DPU), which regulates natural gas in the state, is about half that number.

Massachusetts categorizes gas leaks by risk, with potentially explosive leaks given a Grade 1 classification. The National Grid annual report cited a total of 36 Grade 1 leaks — but the BU fieldwork, identifying 15 out of 100 leaks as Grade 1, suggests that that figure may be low.

Even if all parties agree on how to assess gas leaks and prioritize their repair, fixing them will not be inexpensive, and the cost is borne by gas customers.

“We’re stuck in this conundrum where if we were to retrofit this infrastructure quickly, there would be huge rate increases, and families might not be able to pay their utility bills,” Hendrick says. “But it isn’t if these old pipes will start leaking, it’s when.”

Bills now before the Massachusetts legislature may help to better address these challenges. In the meantime, the BU researchers encourage the public to stay watchful for any gas leaks. “People may become habituated to the smell of a gas leak, but if you smell one you should call it in to your local gas company,” says Phillips.

While the first priority in dealing with leaks is to assure public safety, it’s also critical to consider the climate implications, Hendrick emphasizes. Her paper proposes a leak classification scheme that includes both safety and climate risks.

“We are consuming more natural gas than ever before in the United States,” she notes. “We need research to try to characterize fugitive methane emissions across the entire natural gas system.”

That need is highlighted by the recent environmental disaster as natural gas escaped from storage in Porter Ranch, California — the worst such leak in U.S. history. “We’re starting to realize that unless the entire natural gas system is better regulated, the carbon footprint may be just as bad for natural gas as it is for coal and oil,” Hendrick says.

— Read more in Margaret F. Hendrick et al., “Fugitive methane emissions from leak-prone natural gas distribution infrastructure in urban environments,” Environmental Pollution, 213 (June 2016):  710–16 (        doi:10.1016/j.envpol.2016.01.094)