Q: what's the difference between charcoal and biochar?

A: By definition biochar is "A solid material obtained from the thermochemical conversion of biomass in an oxygen-limited environment." While charcoal is "a dark or black porous carbon prepared from vegetable or animal substances (as from wood by charring in a kiln from which air is excluded)"

"The highly fertile dark earth soils of the Amazon River basin indicate that a form of biochar has been used in agriculture for many hundreds of years. These dark soils, known as Terra Preta, contain a fine grained, carbon rich material. This material comes from charred organic materials like manure, crop residue and bones that was added to the soil. Without sophisticated kilns and ovens to produce modern biochar, this ancient material was likely made by setting alight a pile of organic material before covering it with dirt to eliminate oxygen but hold in the heat from the fire which, in turn, baked the organic matter."

"The technique of using biochar to improve the fertility of soils originated in the Amazon basin at least 2500 years ago. The native Indians of the region would create biochar and incorporate it in small plots of land from 1 - 80 hectares in size. Terra Preta, as it is known in this area of Brazil, remains highly fertile until today, even with little or no application of fertilizers. And this is in a region of the world known for its highly infertile soils."