The following article is reprinted from the March Environmental Synopsis newsletter from the Joint Legislative Air and Water Pollution Control and Conservation Committee, Sen. Scott Hutchinson (R-Venango), Chair. The article was written by Coleen P. Engvall, Research Analyst with the Committee.
Hydraulic fracturing and directional drilling of natural gas have allowed producers to access vast reserves of the fuel, transforming the American energy sector, as well as the economy. Here in Pennsylvania, the Marcellus Shale region produced as much as 16 billion cubic feet of gas per day in 2016, and production shows no sign of slowing.
Natural gas is relatively cheap and clean-burning when compared to other fossil fuels, such as coal or diesel. However, leaks during the processing of natural gas, where methane can escape during compression, for example, have been speculated to impact local air quality.
Researchers from Drexel University in Philadelphia have published a study on the potential air quality impacts of this growing industry. The study, Analysis of Local-Scale Background Concentrations of Methane and Other Gas-Phase Species in the Marcellus Shale, was published in February.
In order to test the relative concentrations of methane and other byproducts, researchers compared ground-based mobile measurements taken in 2012 and 2015, as well as several large scale studies conducted by organizations such as the National Oceanic and Atmospheric Administration.
They measured local concentrations of methane, ethane, carbon monoxide and other chemicals, adding considerations for geography and other compounding variables. They also compared the data to the number of unconventional wells in the area, along with how much gas they were producing.
Their analysis appeared to show that new wells being drilled in the region were not the primary driver of spikes in local atmospheric methane, since the number of new wells declined by over 50 percent from 2012-2015.
From the various measurements researchers used, regions in southwestern and northeastern Pennsylvania did show higher levels of methane, despite this slow-down in new well drilling.
So where was the methane coming from?
By analyzing the composition of the air quality, urban influences and other polluters were ruled out as primary causes. Additionally, the levels of carbon monoxide, which is a byproduct of well drilling, had decreased.
Therefore, the natural gas industry appeared to be the cause of the elevated methane levels, however, the development of new wells was clearly not the cause. Instead, researchers noted that other forms of natural gas infrastructure, such as compressors and pipelines, have increased in the region.
Based on these findings, researchers suggest that the transport and processing of natural gas is responsible for the increased methane. The finding supports the idea of “super-emitters,” which are described as facilities disproportionately responsible for the majority of the natural gas industry’s emissions.
This phenomenon was described in a widely-circulated study published by researchers from Stanford University in 2016.
The researchers acknowledge efforts by natural gas producers to prevent methane leaks, but note that more progress could be made. In order to identify and understand the sources of methane, they also endorse increased air quality monitoring in areas that host unconventional drilling.
Pointing to the few studies that have been conducted that revealed potential dangers, especially to vulnerable groups like children and the elderly, the researchers stress the importance of filling this data gap.
From a policy perspective, regulations have primarily targeted the contamination of water sources. With greater understanding of air quality impacts, the researchers say that methane leaks could also be targeted.
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