Putting the carbon back: The hundred billion tonne challenge

One way to keep carbon dioxide out of the atmosphere is to put it back in the ground. In this, the first of two News Features on carbon sequestration, Quirin Schiermeier asks when the world's coal-fired power plants will start storing away their carbon. In the second, Emma Marris joins the enthusiasts who think that enriching Earth's soils with charcoal can help avert global warming, reduce the need for fertilizers, and greatly increase the size of turnips.