Biochar is creating a lot of excitement in climate change mitigation circles. Also called 'agrichar', let me quote from the website of the International Biochar Initiative:

Biochar is a fine-grained charcoal high in organic carbon and largely resistant to decomposition. It is produced from pyrolysis of plant and waste feedstocks. As a soil amendment, biochar creates a recalcitrant soil carbon pool that is carbon-negative, serving as a net withdrawal of atmospheric carbon dioxide stored in highly recalcitrant soil carbon stocks.

In lay terms, the material is created by heating plant wastes in the absence of oxygen to create both burnable gasses (to continue the process and use for other heating applications) and a charcoal residue which is an excellent soil amendment which is said to be stable in the soil for hundreds or perhaps thousands of years. Sounds almost too good to be true. But hopefully this technology (which is not at all new since ancient civilizations knew the value of working charcoal into soils) will be developed and exploited on a massive scale before long to both aid in the production of food and sequester carbon at the same time.

Here are a couple of other background sites on biochar.

• Biochar.org
• Biochar Website from Cornell University

We have not actually found plans for a backyard version of the 'cooker', so let us know if you find one.