By making biomass into a combination of both energy and agricultural charcoal, the overall process is not only carbon neutral, but carbon negative. The idea of making agricultural charcoal was inspired by the discovery of Terra Preta soils in the Amazon basin where a pre-Columbian civilization made otherwise barren tropical soils fertile by burying charcoal, along with fish bones, kitchen scraps, compost and pottery shards.

Biochar returns all of the minerals to the soil while also improving the water holding capacity of the soil and permanently removing net carbon from the air and storing it in the soil. Carbon that becomes solid charcoal behaves something like a coral reef for soil bacteria and fungi, is not decomposed, and does not become part of the current carbon-nitrogen balance in the soil.

If fully deployed on a global scale, very rough calculations indicate that biochar made from both agricultural and forest waste might ultimately be able to remove as much carbon from the atmosphere each year as anthropogenic sources are currently emitting every year.

Biochar links:

International Biochar Initiative
biochar-international.org

Biochar.org

Science Daily about the article in Nature - May 12, 2007

Scientific American article - May 15, 2007