This footprint -- in the form of methane emissions -- calls into question the use of gas extracted from shale, often promoted as a climate-friendly alternative to fossil fuels.
Researchers from Cornell University evaluated the greenhouse gas footprint of natural gas obtained by high-volume hydraulic fracturing of shale formations -- often referred to as "fracking" -- and estimated methane emissions created by the process.
They calculated during the life of an average shale-gas well, 4 percent to 8 percent of the total production of the well is emitted to the atmosphere as methane in routine venting and equipment leaks, as well as with flow-back return fluids during drilling following the fracturing of the shale formations, an article in the journal Climate Change Letters said.
"The large greenhouse gas footprint of shale gas undercuts the logic of its use as a bridging fuel over coming decades, if the goal is to reduce global warming," Cornell researcher Robert Howarth said. "The full footprint should be used in planning for alternative energy futures that adequately consider global climate change."