The amount of methane leaking from natural gas pipelines, storage facilities, and other sources in the Boston area is as much as three times greater than previously estimated — a loss that contributes to the region’s high energy costs and adds potent greenhouse gases to the atmosphere, according to a new study by scientists at Harvard University.
The leaks would be enough to heat as many as 200,000 homes a year and are valued at $90 million a year, the authors said.
The study — the first of its kind to quantify methane emissions from natural gas leaks in an urban area — also suggests that regulators are substantially underestimating the amount of the nation’s methane emissions. Methane is 20 times more powerful than carbon dioxide, meaning small amounts of the heat-trapping gas can have a significant impact on global warming.
“We were surprised to find that emissions are as high as they seem to be,” said Steven Wofsy, a lead author of the study and professor of atmospheric chemistry at Harvard’s School of Engineering and Applied Sciences. “Once we understand where they come from, we can find ways to reduce them in a cost-effective way.”
The findings come after the Obama administration this month announced new regulations on the oil and gas industry that would cut methane emissions by up to 45 percent from 2012 levels by 2025.
The scientists said the study suggests that state and national regulators should be doing more to curb methane emissions at the end of the pipelines. The administration’s plan focuses on reducing leaks that have come mainly from the drilling, production, and transportation of oil and gas wells related to hydraulic fracturing, which has sparked a boom in US energy over the past decade.
“The emissions in regions receiving natural gas need to be considered more seriously,” said Kathryn McKain, another lead author and graduate student at Harvard.
The study, which will be published Thursday in the Proceedings of the National Academy of Sciences, relied on measurements from September 2012 to August 2013 taken by laser spectrometers at Copley Square, Boston University, Nahant, and the Harvard Forest in Petersham.
The instruments found about 300,000 metric tons of natural gas leaks — about 2.7 percent of all natural gas delivered to the region. State and federal authorities had previously estimated that 1.1 percent of natural gas was being lost to leaks from a range of sources in the area, including homes, businesses, and electricity generation facilities.
If federal estimates are correct, that would mean the Boston area is contributing to 9 percent of the nation’s methane from natural gas, the authors said.
“That seems pretty impossible, and it suggests the entire national estimate is wrong,” McKain said. “It’s difficult to imagine that our region is contributing that much to the total number.”
She said the findings suggest regulators should reevaluate their models for quantifying emissions, conduct similar studies in other urban areas, and consider policies that would provide incentives to utilities and ratepayers to do more to curb emissions quickly.
State and city officials said a law the Legislature passed last summer should accelerate the replacement of old, leaky pipelines. The region has some of oldest pipelines in the country.
“This report supports the city’s ongoing efforts to understand the extent of methane leakages in Boston,” Austin Blackmon, the city’s environmental chief, said in a statement.
The new law allows municipalities to request data about gas leaks from the state, allowing cities and towns to pressure utilities to plug them. Information about the location of leaks in Boston should be available in March.
“This data should further our work with the local utilities to coordinate effective infrastructure repairs, so we can minimize the environmental and public safety risks posed by gas leaks, as well as avoid undue economic losses,” Blackmon said.
Most leaks are unlikely to be a threat to public safety, given that they’re typically small.
Amy Mahler, a spokeswoman for the state Executive Office of Energy and Environmental Affairs, said the new law also makes it easier for the utilities to recoup their costs.
“It allows us to make sure gas companies are going to be able to make repairs sooner,” she said.
Utility officials said they understand the urgency to reduce leaks and are working as quickly as they can.
Since 2010, National Grid has replaced more than 630 miles of natural gas mains in Massachusetts. Over the next five years, the company plans to send $2.4 billion on its gas pipelines.
“We’re accelerating the amount we’ve replaced every year,” said Jake Navarro, a spokesman for National Grid.
NStar officials said this year they plan to replace 30 miles of their 390 miles of cast-iron pipelines at a cost of $43 million, which means they will have replaced more than two-thirds of them.
“We have an aggressive maintenance and inspection program,” said Caroline Pretyman, a spokeswoman for NStar.
Steven Hamburg, chief scientist of the Environmental Defense Fund, called the study “a really important piece of an emerging picture of methane emissions.”
“We don’t want to waste a resource; we don’t want to pollute the air; and we don’t want to release additional greenhouse gases,” he said. “This study makes it clear we need to better understand the sources of emissions in the urban environment.”
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