I own GasFrac which uses NatGas to instead of water.
While it seems crazy to use NatGas, I've been told by people in the know that its safe and environmentally its better as any thinglost will seep away just like the gas/oil they are trying to collect.
I invested in it based on two thesis: 1. Some early test users are claiming their recovery is better than water improving their ROI materially. Hopefully this is true. 2. Federal/State rules on limiting wastewater/usage. Unfortunately while the general thesis still may hold this damages it a little better as I expect states to follow this rule.