A new study of the Barnett Shale in Texas, published by the Proceedings of the National Academy of Sciences (PNAS), contained conclusions that will likely inflame the debate surrounding methane emissions from oil and gas sites. The study shows that methane emissions are likely far higher than previously estimated and that a few high-emitting facilities are responsible for a majority of the emissions. This will provide additional ammunition for those groups that support the regulation of methane leaks from older, existing sources.
This study is significant in several ways. There are two common methods used to estimate methane emissions: the “top-down” method and the “bottom-up” method. Several previous studies have used only one approach or the other, which led to vastly different estimates. Top-down studies attempt to measure methane leaks from the air, using aircraft equipped with methane sensors. These aircraft will fly over an entire oilfield region in order to assess the percentage of methane emissions that stem from oil and gas operations. One criticism of this method is that, in doing so, the aircraft can pick up inaccurate data from non-oil and gas sources such as landfills. Top-down studies have typically found much higher rates of methane emissions than bottom-up studies. In bottom-up studies, the methane emissions are assessed from ground level. This method uses measurements directly collected from drilling sites and along the natural gas supply chain.
The current study, which was conducted over a two-week period in 2013, was the first study to test oil and gas-related methane emissions by using both the top-down and bottom-up approach. The study also addressed concerns related to both methods, asserting that it “reduced uncertainty in top-down estimates by using repeated mass balance measurements, as well as ethane as a fingerprint for source attribution,” and that the “bottom-up estimate incorporates a more complete count of facilities than past inventories, which omitted a significant number of major sources, and more effectively accounts for the influence of large emission sources using a statistical estimator that integrates observations from multiple ground-based measurement datasets.”
After reconciling the data from both sets of tests, the study concluded that the amount of methane leaking from oil and gas sites is “significantly higher” than the estimates used by the EPA—anywhere from 1.9 to 5.5 times as high, depending on which EPA study is used. This means the measured oil and gas methane emissions could be 90% larger than estimates based on EPA’s Greenhouse Gas Inventory.
The study also found that the “estimated emission distributions imply that, at any one time, 2% of facilities in the Barnett region are responsible for half of the emissions, and 10% are responsible for 90% of emissions found.”
The monetary loss due to methane emissions is also staggering: the study found that the emissions resulted in a 1.5% loss of the total production of the Barnett region, which corresponds to a yearly loss of approximately $100 million.
This study comes at a precarious time for the oil and gas industry, which is rallying against any further regulation of methane by the EPA. In August 2015, EPA proposed rules that, together with existing regulations, would cut methane emissions by 20% to 30% below 2012 levels by 2025. The rules would apply only to new sources of emissions and focus on stopping leaks and capturing lost gas.
EPA is also considering whether to regulate existing sources, however, which the oil and gas industry strongly opposes due to the anticipated high cost. Studies like this one clearly do not help the industry’s cause, where they highlight the government’s underestimation of methane emissions and point to several high-emitters as the source of a majority of the emissions.
In a recent letter to EPA Administrator Gina McCarthy, Senator Jim Inhofe of Oklahoma raised concerns generally over EPA’s focus and use of the “social cost of methane” (“SCM”) when developing new rules on reducing methane emissions. Sen. Inhofe stated that “[t]he timing of the SCM’s application is seemingly driven by the international climate negotiations so the Obama Administration can cite regulatory actions for methane and tout outlandish benefit estimates for reducing methane conjured by the SCM.”
This article was authored by Jennelle D. Arthur, Jackson Kelly, PLLC.