The process of hydraulic fracturing includes injecting of large volumes of water, sand and chemicals deep underground into gas wells at high pressure to crack open shale rock and extract its natural gas.
Recently it has been established that the amount of wastewater from hydraulically fractured natural gas wells is much lower than this coming from conventional ones.
However, if the scale of fracking operations is taken into account, the amount of wastewater that is produced is much more overall.
This is particularly the case in the region of Marcellus shale of Pennsylvania. Here only about 35% of the total amount of wastewater per unit of gas comes from conventional wells. These numbers come from a study published in the latest issue of the Journal Water Resources Research.
According to the lead author, Brian Lutz, assistant professor of biogeochemistry at Kent State, who led the analysis while he was a postdoctoral research associate at Duke, although shale gas wells produced about 10 times the amount of waste water as conventional wells, they also produce 30 times more natural gas.
This particular finding was quite a surprise to the team, especially considering that hydraulic fracturing is perceived to produce large amounts of wastewater. However, the researchers also found that the wastewater from natural gas production in Marcellus shale has increased with 570% since 2004.
These numbers are of course large and explain the use of hydraulic fracturing, however because the region is too extensive, the amount of wastewater that should be transported and treated is huge. The authors account this to the increased demand for domestic natural gas, and therefore they state that there are trade-offs that should be made.
The study is based on data from gas production and waste water generation for 2,189 gas wells in Pensylvania. They established that chemicals used in hydraulic fracturing are difficult to treat and logistical and technological solutions are needed to deal with the increasing concern.
Nevertheless, the authors are convinced that the limitations of hydraulic fracturing should be weight against the benefits.