Society depends on fossil fuels as an important energy source. Although global availability of alternative fuel sources (eg, wind power) continues to slowly increase, the majority of daily energy demand is met by coal, oil, and natural gas. Prior to the availability of hydraulic fracturing (fracking), tremendous volumes of natural gas and oil were inaccessible by conventional drilling methods; it was difficult to extract fuel reserves from the oil-laden shale known to underlie many of the more porous geologic formations used historically.