Trees suck carbon dioxide (CO₂) out of the air and turn it into energy: carbohydrates. Shells are largely composed of calcium carbonate, a stable amalgam made from CO₂. Physicist Klaus Lackner would like to imitate those natural processes because "if sustainable development is to succeed, then energy better be cheap, copious and clean." It's the latter part that the natural processes can help with. Lackner has designed"and his start-up Global Research Technologies in Tucson, Ariz., has built demonstration versions of"tall towers that can absorb the CO₂ in the atmosphere and concentrate it so that it can be stored. "Without carbon capture and storage, fossil energy is doomed," Lackner said at the State of the Planet conference. But what to do with the carbon after you've captured it? "If nothing else, we can inject it into the ground," he said. "But I'm not entirely convinced that we can deal with 2,000 billion tons of CO₂, and that is the scale at which we have to operate." Instead, Lackner suggests we imitate the shell-making creatures of the sea and sequester all that carbon in carbonates. The process is simple chemistry, albeit chemistry that requires energy to make it happen, all that's left is to demonstrate it"and the capture side of things"on real coal-fired power plants or in vast farms of CO₂-scrubbing towers. That is not something the Bush administration has shown much interest in of late, most recently scrapping the FutureGen power plant that would have demonstrated similar technology. "Things were getting more serious," Lackner noted, "and they said: 'Don't bother us, we are only pretending to do something.'"