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Vignesh Gowrishankar’s Blog

No smell of gas - but is that really OK?

Vignesh Gowrishankar

Posted April 16, 2013 in Curbing Pollution, Moving Beyond Oil, Solving Global Warming

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A recent study of Manhattan suggests that a considerable amount of natural gas is being leaked into the atmosphere from our infrastructure. New York is not alone – similar leaks were witnessed earlier in Boston too. These indications cannot be ignored.

When we first got wind of this, my colleague jokingly queried whether the dietary habits and digestive abilities of the millions of critters inhabiting New York City’s subways had been sufficiently accounted for. If only they had anything to do with it!

The alleged culprit in Manhattan (and Boston) was the hundreds of miles of metal pipelines that course through the city’s underground. The Manhattan leakage study was conducted by Gas Safety Inc., which used a methane detector to measure ambient levels of the gas across the city. To generate geo-located data, the detector was connected to a GPS unit, placed on a vehicle and driven across Manhattan.

[To clarify, methane constitutes approximately 90 percent of natural gas, and is, in essence, the fuel. Methane is odorless until mercaptans are added by gas distributors to provide the characteristic “gas smell” and ease leak detection. According to Federal Regulation, presence of methane a little over one percent in air should be detectable by smell; the study’s measurements indicate ambient methane in parts-per-million concentrations, which explains the lack of an omnipresent gas aroma.]

The results of the study include a striking map of Manhattan overlayed with the methane leak concentrations (see Figure below). By extrapolating from these measurements, Gas Safety Inc. estimated the overall leak to be 8.6 billion cubic feet in Manhattan per year. This compares to 300 billion cubic feet of natural gas that are transported annually through Con Edison’s pipelines across the whole of New York City, an area 20 times the size of Manhattan and with thrice as many customers as Manhattan. Thus the authors suggest that the leakage rate is (at least) 2.86 percent, from the natural gas pipeline distribution network alone.

 Manhattan.jpg

Map of Manhattan overlayed with methane emissions

As my previous blogs (here and here) indicate, this is in addition to a little under three percent leakage mainly from parts of the natural gas infrastructure before the “city-gate”. This is alarming! If these numbers are indeed accurate, then around five percent or more of natural gas could be leaking. As my previous blog also points out, this would imply that natural gas no longer engenders a clear advantage over coal for producing electricity or useful thermal energy.

Leaks in New York and Boston could reasonably be isolated occurrences. As we all know, these are old cities with ageing infrastructure (and the dearth of infrastructure spending isn’t helping). At a workshop to discuss methane emissions a few months ago, an American Petroleum Institute spokesperson asserted that old pipelines were the cause, and one solution lay in transporting natural gas through corrosion-resistant, plastic-based pipes. I did not dig too deep back then.  

But lately I have begun to wonder again. Yes, Boston and New York are old. But other US cities are not that brand spanking new either, and what’s to stop relatively newer pipelines from leaking ever greater amounts in the coming years. As for the idea of replacing metal pipes with plastic-based ones, it will take some careful consideration, planning and execution. Digging up New York City is monstrously difficult – near my residence the City is taking four years to run a pipeline three short blocks, even while a high-rise building more than 30 stories high is erected in half that time. Pipe-laying can be excruciatingly snail-paced, not to mention inconvenient. We wonks need to start contemplating a range of solutions now.

The alarm bells aren’t quite ringing at full volume just yet. While these isolated studies are immensely helpful, they do not paint the full picture. I, for one, am waiting for better, comprehensive data to become available, including a forthcoming study by the Environmental Defense Fund in collaboration with natural gas companies. My eyes and nose are on high alert.

 Boston.jpg

            Map of Boston overlayed with methane emissions

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Switchboard is the staff blog of the Natural Resources Defense Council, the nation’s most effective environmental group. For more about our work, including in-depth policy documents, action alerts and ways you can contribute, visit NRDC.org.

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