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MARK AUSTIN THOMAS: When we think of alternate energy sources, we think of things like solar power, wind power or maybe biofuels. But there’s another energy source that’s attracting new attention. It comes from the earth’s own heat. From the Marketplace Sustainability Desk Sam Eaton explains.

SAM EATON: It’s called geothermal energy, and a team of MIT scientists have come out with the first comprehensive study to assess the technology’s potential in more than three decades.

Project leader Jefferson Tester says by tapping the vast amounts of heat trapped in the earth’s crust, the U.S. could generate a tenth of its power needs without emitting a single molecule of CO2.

JEFFERSON TESTER: And we can get access to it technically. This isn’t something that requires new drilling technology.

It’s just a matter of drilling to depths of 5,000 feet or more, fracturing the rocks and then pumping water in to create steam.

That steam drives turbines on the surface, generating electricity. And unlike other renewable energy technologies such as wind and solar, geothermal provides a constant energy source, so long as there’s enough water.

And there’s the rub. The shallowest pockets of hot rock are in the western U.S., where water can be hard to come by.

I’m Sam Eaton for Marketplace.