Study: Methane pollution from oil and gas industry much larger than prior estimates

Last week, a team led by Harvard scientists Scot Miller and Steven Wofsy published a new study in the prestigious Proceedings of the National Academy of Sciences (PNAS) that found that methane pollution from the oil and gas industry, agriculture and other industrial activity could be 50-70 percent higher than the EPA and others had previously thought.

The new study adds to the growing body of evidence that methane leakage from natural gas production and distribution systems is larger than we thought, giving this fuel a bigger global warming footprint than current government and industry estimates.  (Methane makes up as much as 90 percent of natural gas.) 

Specifically, the Harvard study indicates that methane emissions caused by human activity, including agriculture and natural gas supply, is 50 percent more than EPA’s current national estimates. If you consider the oil and gas industry alone, EPA’s latest inventory reports that about 1.5 percent of all natural gas produced is emitted (leaked or vented). But, if we assume the same 50 percent discrepancy for methane emissions from the oil and gas industry in particular, we can infer that about 2.3 percent of all natural gas produced is actually emitted into the atmosphere. 

The discrepancy was even higher in the South Central region of the U.S. (which includes major oil and gas producing states like Texas, Oklahoma and Kansas, and accounts for about a quarter of national methane emissions). There, the study measured methane emissions from the fossil fuel industry that were 5-7 times higher than previously estimated by EDGAR, a comprehensive global methane inventory. [See below for how the study differs from the EPA and EDGAR inventories.]


Figure from the paper showing the discrepancy of methane emissions estimated by this study versus an existing inventory (EDGAR), overlaid on a map of the US. Green and blue hues indicate measurements in excess of current inventories, which are particularly pronounced near Texas and California.

At such high methane leakage levels, the climate advantage of natural gas over coal would be much smaller than many previously thought. The reason is that methane is a very potent heat-trapping gas that is at least 28 times more powerful than carbon dioxide over the long-term, and 84 times more powerful over a shorter 20-year horizon. So leaking a relatively small amount of methane packs a wallop.  

This underscores the fact that, as a society, in order to stop runaway climate change we must move away from fossil fuels as quickly as possible. As NRDC President Frances Beinecke emphasizes, we have the resources and ingenuity to power our country with clean energy – wind, solar, energy efficiency – and we must focus on these. But until then, while we are still using natural gas, it is absolutely essential to stop leaking it away into the atmosphere where it just makes climate change even worse.

The paper’s findings refute claims by the oil and gas industry that the federal government (EPA) doesn’t need to regulate methane pollution from their operations, and that EPA has overestimated how much pollution the industry is responsible for. To the contrary, it suggests EPA has underestimated the leakage problem and strong federal methane standards are sorely needed. This wanton leakage and waste is unnecessary and unacceptable. 

In fact, we know just how to sharply reduce the methane pollution from natural gas operations. By taking advantage of proven, cost-effective measures that exist now, we can cut up to 80 percent of the methane pollution from the oil and gas industry. And what’s more, these measures can actually save the industry as much as $1.5 billion a year, so there’s really no excuse to delay action. (Last month, I testified on these measures at a Senate Subcommittee hearing.)

Just a couple of weeks ago, Colorado proposed new, first-of-their-kind standards that—though they can and should go further—would be a promising start at reducing methane and other air pollution from the state’s booming oil and gas industry.

This new Harvard study underlines the scale of this threat and the urgent need for other states and the federal government to also take action to tackle methane pollution from the gas industry. At the federal level, that means EPA needs to step up and directly regulate all methane emissions from the oil and gas industry. At the state level, it means states should also adopt strong methane standards (building on the promising start demonstrated by Colorado). And industry should immediately step up to install available technology to prevent these leaks.  EPA must also redouble its efforts to more accurately estimate methane leakage from the oil and gas and other industries.

And, as a nation, it reminds us of the urgent need to continue building a cleaner energy future.

NOTE: For those interested in a more detailed look at the findings of the PNAS paper, a short summary follows:

  • The paper was published in PNAS by a team of scientists led by Scot Miller and Steven Wofsy from the Department of Earth and Planetary Science at Harvard University. The paper was co-authored by fourteen other researchers from leading universities and research institutions from across the country (and one from Italy).
  • The study’s authors have summarized in the paper what they see as its significance in this way: “We find greenhouse gas emissions from agriculture and fossil fuel extraction and processing (i.e., oil and/or natural gas) are likely a factor or two greater than cited in existing studies.  Effective national and state greenhouse gas reduction strategies may be difficult to develop without appropriate estimates of methane missions from these source sectors.”
  • The paper’s main finding is that methane emissions from the fossil fuel and the animal husbandry (livestock) industries have much larger greenhouse gas impacts than estimated in current inventories.
    • Across the US, methane emissions due to human activity were 50-70 percent higher than inventories, including the one regularly released by the EPA.
    • In the South Central region of the US (which includes states like Texas, Oklahoma and Kansas that are major oil and gas producing states, and account for about a quarter of national methane emissions), the study measured methane emissions caused by human activity that were ~2.7 times those in inventories, and up to 5-7 times more in the case of emissions from the fossil fuel industry.
  • The research team used a “top-down” approach combining atmospheric methane observations (more than 12,000 observations from aircraft and towers), modeling, and spatial datasets. The emissions monitoring data was from 2007 and 2008. The researchers’ methodology was able to differentiate the methane leakage from different sources, such as the oil and gas industry, livestock, landfills and coal mining.
    • These results highlight a yawning divergence between “top down” atmospheric measurement studies and previously published inventories that generally use a “bottom-up” approach to estimating emissions (aggregating leakage by multiplying the number of wells, compressors and other pieces of equipment, by assumed leakage rates). The paper’s “top-down” approach, grounded in actual measurements of methane in the atmosphere, provides a reality check on shortcomings with traditional “bottom-up” approaches, which may have overlooked significant leakage sources and/or used outdated assumptions.  At the very least, the current inventories should be revised to incorporate this new information and to improve their current procedures.