Appalachian Basin

Three Key Takeaways From Drexel’s New Methane Study

A recent study from researchers at Drexel University found that based on data collected in 2015, volatile organic compounds (VOCs) emissions from natural gas development are not likely impacting local background levels in rural regions of Pennsylvania near Marcellus development. The study also found methane only increased very slightly—100 parts per billion, which essentially means emissions remained flat—from samples taken by the team in 2012 in certain areas where the two collections overlapped.

Here are three key takeaways from the study:

This study and others show VOCs from Marcellus are not impacting background levels.

Importantly, the report states that VOC emissions from development are not likely impacting local background concentrations.

“CH4 local background mole fractions were not found to have a detectable relationship between well density or production rates in either region. In Northeastern PA, CO was observed to decrease 75 ppbv over the three year period. Toluene to benzene ratios in both study regions were found to be most similar to aged rural air masses indicating that the emission of aromatic VOC from Marcellus Shale activity may not be significantly impacting local background concentrations.”

This aligns with the findings of several other Marcellus studies, including the researchers’ own previous 2012 sampling study:

“Most notably, we did not observe elevated levels of any of the light aromatic compounds (benzene, toluene, etc.) that have previously been observed in oil and NG operations. With the exception of CH43OH, which was observed at one compressor station and has been observed at NG well pads, all of the other VOCs detected have been attributed to on-road engine exhaust.” (Page E; emphasis added)

The 2012 study also explained:

“Additionally we have shown that in contrast to other unconventional NG resources there are few emissions of nonalkane VOCs (as measured by PTR-MS) from Marcellus Shale development.” (Page H; emphasis added)

As Peter DeCarlo, the lead researcher for both studies, said of the previous study, “we didn’t see a lot of the air quality pollutants that we expected.”

Pennsylvania Department of Environmental Protection’s (DEP) Annual Marcellus Inventory shows methane emissions have decreased as natural gas production has increased.

The tiny increase—100 parts per billion—shown in the Drexel study is pretty well aligned with data being collected annually by the DEP. Data from DEP’s most recent report showed a slight, one percent increase in methane emissions from 2013 to 2014. More importantly, the data also show methane emissions in Pennsylvania fell 12 percent between 2012 and 2014, while “unconventional gas wells increased significantly, from 3.1 trillion cubic feet of gas to 4.1 trillion cubic feet.” That’s a 33 percent increase in production.

A one percent increase despite 12 percent more midstream facilities reporting according to DEP demonstrates the diligence of the industry to reduce its emissions throughout the process of developing and delivering natural gas.

Perhaps more importantly, Pennsylvania has been able to achieve drastic decreases from other sources like electricity generation that has lowered emissions as a whole for the state. This is something DEP Acting Secretary Patrick McDonnell explained in the press release for the most recent inventory,

“Although the reported emissions from the natural gas sector increased in 2014, overall our air quality continues to improve due to emissions reductions from other point sources such as electric generating units,” McDonnell said. “Between 2011 and 2014, NOx and SO2 emissions from electric generating units have decreased by 18 percent (27,246 tons per year) and 17 percent (54,973 tons per year), respectively.”

Former DEP Secretary Chris Abruzzo previously highlighted similar sentiments as well, explaining that the emission reductions from the state’s increased use of natural gas based on 2012 data represented “between $14 billion and $37 billion of annual public health benefits,” and that,

“It is important to note that across-the-board emission reductions … can be attributed to the steady rise in the production and development of natural gasthe greater use of natural gas, lower allowable emissions limits, installation of control technology and the deactivation of certain sources.” (emphasis added)

This trend, including the health benefits, will only get better as more natural gas is developed from the Marcellus and used here in the Commonwealth.

Perspective: 100 parts per billion (ppb) is a minuscule amount.

It is also important to put the study’s findings on methane emissions in the proper context. The researchers found an increase of 100 parts per billion in 2015, which is a minuscule amount and shows emissions essentially remained flat. Let’s put that figure into perspective—the Texas Commission on Environmental Quality (TCEQ) has a chart that helps to break down this figure with real world applications explaining what one part per billion is. Using TCEQ’s examples, 100 parts per billion would be:

  • 100 grains of salt in 1,000,000,000 grains of sugar.
  • 100 pennies in 10 million dollars.
  • 1 minute 40 seconds in 32 years.
  • 100 feet of a trip to the moon.
  • 100 blades of grass on a football field.
  • 100 drops of water in an Olympic-size swimming pool.

Nonetheless the Drexel researchers have called this rate of methane increase “quite substantial compared to the global increase” and attribute the rate of increase to methane leakage.

First, methane emissions from natural gas systems are decreasing according to the Environmental Protection Agency’s (EPA) 2017 Green House Gas Emissions Inventory. According to the inventory, natural gas system methane emissions are down 18.6 percent since 1990, 1.3 percent from 2005, and 1.1 percent since 2011. Like in Pennsylvania, this is occurring at the same time natural gas production has skyrocketed—up 42 percent since 2005! From the report,

“Methane emissions from natural gas systems and petroleum systems (combined here) decreased from 254.8 MMT CO2 Eq. in 1990 to 201.5 MMT CO2 Eq. (53.3 MMT CO2 Eq. or 20.9 percent) from 1990 to 2015.”

Leakage may occur and is actually allowed within the levels agreed upon through the permitting process.  But numerous studies—the Department of Energy (DOE), the University of Colorado at Boulder/NOAAMIT, the University of Maryland, Carnegie Mellon and Cornell University — have found that methane leakage from natural gas systems is well below the threshold for natural gas to retain its climate benefits.

So, there is a large body of research that shows the Drexel researchers’ statement that “with the increased background levels of methane, the relative climate benefit of natural gas…for power production is reduced” is inaccurate. Especially given the drastic decreases in methane that have occurred in Pennsylvania as a result of more natural gas-fired electric facilities.

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