It’s possible to fracture gas-rich rock formations without using any water at all. Indeed, gas and oil companies have been using carbon dioxide this way for decades, albeit on a limited basis. Right now carbon dioxide fracking is used in places, like Wyoming, that already have carbon dioxide pipelines. But if this approach is going to be used on a large scale, it will require a major investment in infrastructure for getting carbon dioxide to fracking sites. And in some cases a price on carbon emissions may be the only way to make the economics work.
A price on carbon, for example, could create a big supply of cheap carbon dioxide by giving utilities incentive to capture it from power plants’ smokestacks. This might make sense in China, where the best shale gas deposits are in arid areas (see “China Has Plenty of Shale Gas, but It Will Be Hard to Mine”).