Quickly: An alternative to using water in fracking for natural gas, potentially eliminating the water use and wastewater disposal concerns, detailed over at Inside Climate News. One major downside to date is that it costs more than using water in hydraulic fracturing, so few companies have been willing to use propane gel to crack the rock and get at natural gas.
Called liquefied propane gas (LPG) fracturing, or simply "gas fracking," the waterless method was developed by a small energy company, GasFrac, based in Calgary, Alberta.
Still awaiting a patent in the U.S., the technique has been used about 1,000 times since 2008, mainly in gas wells in the Canadian provinces of Alberta, British Columbia and New Brunswick and a smaller handful of test wells in states that include Texas, Pennsylvania, Colorado, Oklahoma and New Mexico, said GasFrac Chief Technology Officer Robert Lestz.
Like water, propane gel is pumped into deep shale formations a mile or more underground, creating immense pressure that cracks rocks to free trapped natural gas bubbles. Like water, the gel also carries small particles of sand or man-made material—known as proppant—that are forced into cracks to hold them open so the gas can flow out.
Unlike water, the gel does a kind of disappearing act underground. It reverts to vapor due to pressure and heat, then returns to the surface—along with the natural gas—for collection, possible reuse and ultimate resale.
And also unlike water, propane does not carry back to the surface drilling chemicals, ancient seabed salts and underground radioactivity.
Read more, and (no doubt) debate at will: Inside Climate News
Personally, while I'm still mulling this one over, I'm not sure it eliminates the concerns about watershed contamination at all -- though reducing the water use itself is certainly a good thing. And I'm not sure it reduces the higher emissions of natural gas obtained via fracking versus natural gas obtained from more conventional drilling methods.