US, Nov. 11 -- The material that keeps carbon out of the sky

Biochar looks like charcoal. In many ways, it is. But where burning sends a plant's carbon straight back into the atmosphere within minutes, biochar locks that carbon into a stable solid that can stay put for centuries.

It starts as biomass, any organic material a living plant built by pulling carbon from the air. Crop residue, wood and forestry leftovers, nut shells, and other waste that would otherwise be burned or left to rot can all become biochar. Heated with almost no oxygen, that material becomes something else entirely.

Same carbon, opposite outcome: one path feeds the crisis, the other takes a load off the sky and leaves behind soil that holds water and grows better...