That's the sound of fracking —pumping a mix of water, sand and chemicals a mile or more into the Earth to shatter shale deposits and release the natural gas within.

From the Barnett shale in Texas to the "supergiant" Marcellus shale that stretches from West Virginia to New York State, so much natural gas has been found that the U.S. may have enough to burn for 100 years or more. And burning natural gas releases 43 percent less CO2 than burning coal.

Fort Worth has transitioned from cow town to gas town. It's the booming capital of fracking with thousands of wells within city limits. But fracking comes with a cost.

In addition to water use, there's the problem of what to do with the brine and chemicals left over afterwards. Bad drilling lets natural gas seep up to drinking water aquifers and wells, causing some taps to literally burn . And independent testing has shown toxic gas levels hundreds of times higher than safe limits in nearby DISH , Tex.

Fracking may have a lot of upside , but such fossil-fuel exploration and exploitation has to be done right. Or we'll have a fracking mess on our hands.

—David Biello