Maps From Google and Green Group Make Pavement-Level Pollution More Concrete

Say what you want about oil spills. At least when you're standing in one it's hard to miss.

That's not true of methane spills, which are invisible and -- unless it's a potentially explosive concentration of gas -- unsmellable.

Persistent, low-grade methane leaks are of interest for a couple of reasons. For gas companies, they mean the loss of product that could be heating homes or fueling generators. For everybody, it means climate pollution that nobody’s seeing, measuring or capping.

That's why the Environmental Defense Fund (EDF) and Google Earth Outreach have spent the last two years wiring cars with methane sensors and gradually testing them out in American cities to "see" any leakiness and estimate how much gas is heading skyward. The same methane that heats homes and powers turbines is a strong heat-trapping gas in the atmosphere.

The partnership is a novel endeavor -- a civil society group harnessing private technology to simultaneously help out gas utilities and influence public policy. Steven Hamburg, EDF's chief scientist called it "entrepreneurial science."

“This is the beginning of what I really see as a big shift in the way we can give people data” about the environments they live in, he said.

Today, the pilot project announces its results from three U.S. urban areas, Boston, Indianapolis and New York City's Staten Island.

The team’s initial results suggest America's older cities, with their decades-old underground infrastructure, still have work to do investigating leakiness. EDF, which is in charge of the program’s scientific research, has broken its findings into three general categories: leaks with low, medium and high volume of gas.

Here's Boston, an older city with pipes that could be more than a half-century old. Yellow leaks have the same near-term climate impact as driving a car between 100 and 1,000 miles a day; orange ones between 1,000 and 9,000 miles per day; and red even more than that.

Natural gas leaks measured in Boston. Source: EDF and Google Earth Outreach

The team also recorded emissions on Staten Island, particularly around the borough's large methane-producing landfill:

Natural gas leaks measured in Staten Island, New York. Source: EDF and Google Earth Outreach

The cleanest of the three cities is Indianapolis, where the sensor recorded one leak every 200 miles. “The most interesting question is why Indianapolis has fewer leaks than other cities so far," said Robert Jackson, an environmental scientist at Stanford University, by email. A likely answer -- probably involving new pipes -- could influence how other cities plan. Jackson, who also studies methane releases in U.S. cities, has known about the EDF-Google Earth Outreach project for some time but isn't directly involved.

Natural gas leaks measured in Indianapolis. Source: EDF and Google Earth Outreach

The maps and preliminary findings are available here.

Here's how the car works.

The Google Street View car is a Subaru Impreza equipped with a camera set atop a black pole. Fully equipped, the car needs more than 10-foot clearance. Scientists outfitted it with barely-noticeable tubing that runs across the bottom of the grill in front, through the car, into the back. There, it feeds a continuous air sample into the tiniest dehumidifier you ever saw, and finally into the gas analyzer, which reads the methane levels.

The gas spectrometer works in real time and is calibrated to a GPS unit so the computer knows at all times where the car is, how fast it's going and how much methane is on the street. For most of the ride, the level hovered at or just above the atmospheric baseline of about 1.9 parts of methane per million parts of air.

A computer monitor set up in the passenger’s front seat displays several graphs, the most important being fever-charts showing the gas level and speed. I took this snapshot just as we pulled out, at 21st Street and Park Avenue.

See the spike?

The methane analyzer in the EDY and Google Earth Outreach car. Photographer: Eric Roston/Bloomberg

That is probably what in the business is called a "false positive." The sensor did smell methane, but it was likely coming from the natural-gas-powered package delivery truck pulled over behind us, not below the street. If the car was actually monitoring methane on Monday, rather than driving a journalist around, it would conduct more than one pass, to see if the spike is truly real, or if it was a passing thing. False positives are removed from the final results to ensure the integrity of the data.

And that spike is at a safe level. In all the miles logged for this project, the sensors haven’t picked up a “tier 1,” or dangerous gas leak, Hamburg said.

It took about a year of research and testing to understand and correct for what the scientists were seeing, and how to estimate the rate of the gas flows, according to Joseph von Fischer, a Colorado State biologist who is working with EDF and Google Earth Outreach.

Google Earth Outreach has helped NGOs on environmental projects before, but never commandeered Street View cars for one of them. It declined to disclose its cost for this project.

EDF has spent the last couple of years looking aggressively into potentially leaky U.S. gas infrastructure. Leaks make up about a quarter of a percent of gas deliveries, according to the EPA, a number that has fallen 22 percent since 1990. EDF has also worked with the American Gas Association, which represents local utilities, and Washington State University researchers to look at actual leaks from 13 companies' pipelines and compressors. The study is set to be released later this year.

Almost 40 states offer companies incentives to replace old pipes. “Because of the low-cost of natural gas, now is an opportunity to accelerate the replacement of pipelines,'' said Dave McCurdy, the gas association’s president.

Now, scientifically enhanced cars can accelerate that and other discussions, too.

With assistance from Mark Drajem in Washington.

More by Eric Roston (@eroston on Twitter):

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