The Challenge of Methane Emissions: How Important, How to Detect
Much recent debate about shale gas recovery through horizontal drilling and hydraulic fracturing has focused on methane emissions from shale gas wells. The general take on this topic is that methane (the remarkably simple molecule CH4) is a greenhouse gas “20 times” or “25 times,” or some other number, more “potent” than carbon dioxide, the chief greenhouse gas produced by coal combustion.
The take-away from that—as proffered by Cornell University engineering professor Anthony Ingraffea—is that natural gas is a flawed approach to reduce greenhouse gas emissions as compared to coal. Ingraffea is part of a Cornell group that has opposed fracking for natural gas as environmentally dangerous. He wrote in a New York Times op-ed commentary recently of methane, that “even after a century, it is at least 25 times as powerful as carbon dioxide. When burned, natural gas emits half the carbon dioxide of coal, but methane leakage eviscerates this advantage because of its heat-trapping power.”
The Cornell group has argued that fugitive methane emissions from natural gas wells are an uncontrolled problem and as more wells as drilled as a result of fracking technology, more emissions will result. The fugitive emissions, he said, also include leaks from pipelines, gas compressor stations, and gas processing units. He offered an extraordinarily wide range of estimates of fugitive emissions of “from 2.35 to 17% of annual emissions.”
But Ingraffea’s analysis has come under rigorous challenge, even from scientists who are strong supporters of propositions to cut down on greenhouse gas emissions. Writing in Andrew Revkin’s “Dot Earth” blog, University of California physicist Richard Muller commented on Ingraffea’s claim that methane emissions are “25 times” as potent as CO2. “I will argue,” wrote Muller, “that the proper value to use when considering fugitive methane is not 25 but 3.3. This dramatically smaller value can directly affect the way people think about fugitive methane.”
Muller noted that methane breaks down in the atmosphere far faster than carbon dioxide, that methane has a greater energy density than coal, producing more heat per molecule and is therefore more energy efficient, and that methane is burned in combined-cycle generating plants that are much more efficient than the best coal-fired plant. He expressed skepticism that any company in the business of making profits would allow so much of its saleable product—natural gas—to escape as Ingraffea posits.
On the issue of methane leakage, the Environmental Protection Agency recently dramatically cut its estimate of the scale of fugitive emissions from natural gas production, transmission, and storage facilities. The EPA report noted that fugitive emissions from natural gas facilities are falling significantly as production is rapidly increasing. Kathy Klaber, the outgoing head of the Marcellus Shale Coalition in Pittsburgh, said that the EPA figures “reflect that certain emissions-reducing technologies, specifically a process known as green completions, are far more widely used than previously understood.”
Escaping natural gas obviously represents both an environmental challenge and a business proposition: natural gas is valuable, as a commodity that producers sell and consumers use. So it makes sense to try to find the sources of leaks in order to close them and return the gas to economic use.
To that end, the New York Times reports, companies are developing ways to detect and locate gas escaping from pipelines and other sources. The newspaper’s science writer Matt Wald notes that “laser technology, some of it borrowed from the telecommunications industry, is giving engineers and scientists crucial new tools to measure leaks and track them to their source.”
The large combination electric-and-gas utility Pacific Gas & Electric is using a conventional car, equipped with advanced laser and computer technology, to cruise the roads and streets of North California to smell out natural gas leaks (although methane has no smell in human olfactory systems). The technology can detect differences from uncontrollable sources of methane, such as swamps and marshes (and perhaps farm animals) from those resulting from drilled wells, including shale gas production.
The gas sniffing technology is a product of Picarro Inc., which claims it has remarkable accuracy in distinguishing natural and man-made gas emissions. PG&E, the Times reported, has bought six Picarro units. “I see it as a game-changer,” said Nick Stavropoulos, the PG&E’s executive vice president for gas operations. “It’s amazing how much more effective it is in finding gas leaks on our system than traditional technology.”
—Kennedy Maize is MANAGING POWER’s executive editor.