Carbon Footprint Analysis of Source Water for Hydraulic Fracturing: A Case Study of Mine Water Versus Freshwater

Abstract

In the face of climate change, less carbon intensive fuels are being sought. Natural gas has been perceived as a transition fuel, producing less CO2 when burned than coal, but it is not a renewable resource. Hydrocarbon-rich shale formations contain natural gas, natural gas condensate, and oil production potential, and the extraction of these compounds has allowed the USA to become one of the largest global producers of natural gas. Horizontal drilling and hydraulic fracturing are used to extract the shale gas, but hydraulic fracturing of one well typically requires between 7 and 19 million L of water. One option being explored is the use of treated mine water as an alternative to freshwater. The Marcellus and Utica shale formations underlie much of the eastern USA, and the Utica Shale is being pursued for its high natural gas potential in eastern Ohio. Permits for wells are being approved, but concerns about the water source for hydraulic fracturing fluid are increasing. We analyzed the carbon footprints of three different water sources: treated mine water from Corning, Ohio, freshwater from the Ohio River, and freshwater from Seneca Lake near the well site. CO2 emissions for each source were calculated during pumping, transportation, and treatment of the water for a one-time well use and annual use. The primary productivity increase that occurred after removal of mine discharge or reduction due to extraction from freshwater sources was also calculated. Annually, using treated mine water would emit 110,000 t of CO2-e (CO2 equivalent) if trucked to a treatment plant or 90,000 t of CO2-e if treated on-site, while using water from the Ohio River would emit 2,000 t of CO2-e, and using water from Seneca Lake would emit 4,500 t of CO2-e, annually. Of course, decreasing the amount of unpolluted freshwater used has other environmental benefits.