Shale gas: Opportunities and challenges

Shales are becoming the most important source of natural gas in North America, and replacement of coal by natural gas is reducing CO2 emissions and improving air quality. Nevertheless, shale gas is facing strong opposition from environmental nongovernmental organizations. Although these organizations have greatly exaggerated the potential negative environmental impacts of shale gas and shale oil, methane leakage and contamination of groundwater and surface water by flowback and produced waters are serious concerns. These contamination pathways are not unique to shale gas and shale oil, and they are manageable.