Methane leaks of shale gas may undermine its climate benefits

If methane leak rates are more than 3 percent of output, fracking of shale gas formations may be boosting greenhouse gas emissions rather than lowering them.

Debate about the environmental impact of hydraulic fracturing or fracking usually centers around the potential risks to our water supply from contamination by toxic fracking fluids, which are pumped at high pressure over a mile under the ground to break up gas-bearing shale formations. In recent months, however, there has been renewed controversy over the effect that gas drilling has had on greenhouse gases in the atmosphere.

Proponents of fracking assert that the boom in natural gas has helped to cut America’s emissions of carbon dioxide, by encouraging coal-burning power plants to switch over to the cheaper and cleaner burning natural gas. CO2 output is now at its lowest level since the early 1990s, due in part to the increasing use of natural gas, and also to greater fuel efficiencies and the slow but steady growth in renewables.  

But critics counter that the climate advantage of less CO2 may be canceled out by higher emissions of methane. Natural gas is primarily methane, the most powerful of the greenhouse gases, and the next most abundant in the atmosphere after CO2. The critical question is how much methane leaks during the drilling process, and also subsequently during processing and transport of the gas. The Environmental Defense Fund (EDF) says that if leak rates are greater than 3 percent of the total output, then fracking may actually be increasing America’s greenhouse gas load rather than diminishing it, as the industry claims.

That’s because methane has anywhere from 20 to 70 times more warming potential than CO2, depending on the time frame that one considers. It is especially damaging in the short term, but has a briefer half-life, leaving the atmosphere quicker than carbon dioxide, so methane’s long-term effects are not as great.  

But it is precisely the next few years that are critical. If we don’t put a brake on the rate of increase in greenhouse gases quickly, scientists warn, the momentum of climate change might become all but impossible to slow down. Methane may well tip the balance. 

The levels of methane in the atmosphere have been increasing steadily since 2007, roughly the beginning of the current fracking boom. Is gas-drilling to blame for this rise, or are natural processes like the thawing of Arctic tundra and bacterial decomposition of organic material in wetlands and rice paddies responsible? We can’t say for sure, for the simple reason that nobody is monitoring methane leak rates from gas and oil wells. The industry is not required to do this, and neither are government agencies. 

In the absence of hard data from the field, gas companies have made their own assumptions. The Environmental Protection Agency recently released a report that estimated that methane leaks from gas drilling amount to 1.5 percent, based on industry guesses, and the recent application of new pollution-control technologies. However, this low figure is disputed by some scientists, like Robert Howarth and Anthony Ingraffea of Cornell University. Drs. Howarth and Ingraffea are the authors of a controversial 2011 paper that estimated that methane leaks from fracking are far higher than the gas industry has claimed.

This Cornell study is also basically speculative, since there are no comprehensive monitoring studies of methane leaks nationwide. But there have been isolated regional assessments. In one conducted by the National Oceanic and Atmospheric Administration and the University of Colorado, Boulder, methane leaks in the Uinta Basin in Utah and the Denver-Julesburg field in Colorado ranged between 4 and 9 percent of the total output from the wells. 

While it is impossible to know whether these local “snapshots” are typical of fracking elsewhere, the alarmingly high numbers have spurred efforts to measure leaks more comprehensively. This is hard to do, because methane is not just escaping at the fracking wells. There are also leaks from both long-distance pipes and also from municipal gas distribution systems, which are difficult to track. While precise figures are hard to come by, researchers in Boston, Washington, New York, and Los Angeles have recorded higher than expected leakage rates from aging gas mains.  

The EDF has joined forces with energy companies and private philanthropies to conduct a multiple-year study of the leak problem; the first of several reports is due out this month or next. But EDF has drawn fire from a coalition of grassroots environmental organizations for what Gail Pressberg, a senior program director with the Civil Society Institute, calls their "willingness to be co-opted" by industry. [Editor's note: This paragraph was updated with a new time frame for the release of the first EDF report.]

In an interview, Ingraffea told me that he, too, questions whether this new study will be thoroughgoing and objective, given that EDF has a longstanding policy position that fracking is on balance good for the environment: “It's an awkward position to be in when you’ve already stated what you want the answer to be, and then claim that you are doing the 'definitive study' to prove it.”  

EDF president Fred Krupp responds to his critics: “If fracking is going to take place anywhere in the US – and clearly it is – then we need to do everything in our power to protect the people living nearby. That includes improving industry performance in every way possible.” Mr. Krupp clearly hopes that the new study will encourage the gas companies to clean up their act. 

The joint EDF/gas industry survey is one of a half dozen studies currently in the works to assess the extent of the methane leak problem. Howarth and Ingraffea have also done their own monitoring study of methane levels in Pennsylvania's fracking zone, to be published shortly. We soon may have a better idea if fracking is the climate boon that its backers claim it is, or the bane that many environmentalists fear it will turn out to be.

– Richard Schiffman is an environmental journalist whose work has appeared in the Washington Post, NPR, the Guardian, and elsewhere.