Researchers at Carnegie Mellon University released a study earlier this month on greenhouse gas emissions produced from hydraulic fracturing. The study challenges a similar study published by Cornell in May.
The study by Carnegie Mellon estimates that greenhouse gas emissions from shale gas is lower than emissions from coal burning by between 20 to 50 percent. The previous Cornell study said greenhouse gas emissions from shale gas were greater than coal emissions by 20 percent.
The new findings have energized the ongoing debate over the extraction of natural gas from wells underneath New York State through the controversial method known as “hydrofracking” — a technique where a chemical mixture is pumped into shale rock underneath the ground at high pressure to break apart rocks and release natural gas.
One of the authors of the Cornell study, Prof. Robert Howarth, ecology and environmental biology, explained the contradicting conclusions of the two studies by bringing attention to Carnegie Mellon’s use of data, which he called “internally inconsistent and poorly documented.”
Cornell’s study, conducted by Howarth, Prof. Anthony Ingraffea, civil and environmental engineering, and Renee Santoro, a research technician in ecology and evolutionary biology, has previously been used as a scientific reference for advocates against hydrofracking.
Their research determined that the shale gas released through hydrofracking generated life greenhouse gas emissions that were “at least 20 percent greater” than that of burning coal. This meant that using natural gas as a source of energy was “dirtier” than coal in respect to its environmental impact.
According to a University spokesperson, Carnegie Mellon’s research will in no way affect Cornell’s current ban against hydrofracking on its land, a policy that has been in place since 2010.
One significant difference in the Carnegie Mellon study was its use of a 100-year time scale to determine the global warming potential of methane, a large component of shale gas, Cornell’s use of using a 20-year time scale. Since methane has an atmospheric lifetime of around 12 years, as listed by the Environmental Protection Agency, a longer time frame diminishes its global warming potential.
According to one of the Carnegie Mellon researchers, Prof. Chris Hendrickson, the century-long estimate is “the standard way it’s done for climate change modeling.”
However, Santoro defended the 20-year interval used in her research, calling it more appropriate for solving short-term issues in the field of climate change.
Carnegie Mellon’s study received negative peer review from Howarth for lacking an explanation as to why its results differed so greatly from his own.
“The [Carnegie Mellon] paper did not reference our paper, and they have come under heavy criticism for this. As scientists, we are supposed to acknowledge the work of peers and say how our work does or not agree,” Howarth said in an e-mail statement.
In response, Hendrickson claimed that he was unaware of Cornell’s study, saying it had not yet been published when he completed his research. He also asserted the legitimacy of his own conclusions.
“This is how scientific research proceeds. You’ve got multiple experiments and multiple studies,” Hendrickson said. “This is how the scientific process works.”