FORTUNE -- Bright ideas about how to help the environment and in the process make a few bucks -- or perhaps even a few billion bucks -- abound. But which of them could actually work?
Might it be billionaire Tom Siebel's new venture, the mysteriously-named C3, which aims to use clever software to radically improve big companies' energy use and carbon output?* Or perhaps it will be Global Thermostat, which says its "carbon negative" technology can suck carbon dioxide right out of the air. (For power the company uses the excess heat generated by existing industrial processes such as smelting, energy that currently goes to waste.) Carbon capture technology would look especially appealing if Japan's recent catastrophe sends zero-carbon nuclear power into a long-term decline.
Many of the contenders will get a chance to reveal their plans at Fortune's annual Brainstorm Green conference, which starts today and brings together a who's-who of the green movement from government, the Fortune 500 and all manner of newcomers. More
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