Biochar (or horticultural charcoal) should not be used alone without a source of organic material, so we are combining it in a dry mixture with VermiCompost. We call the blend BioPreta.
Our BioPreta products are for sale at: BioPretaSuperSoil
Then, brewing a "tea" with BioPreta gives biochar the immediate short-term inoculation of microorganisms needed to convert the organic material to "inorganic soluble salts" required by plant roots for immediate absorption.
VermiHarvester and while they learn about vermiculture, their parents get drawn into a discussion of sustainability, and converting organic waste into food.
You will find the story of biochar and Terra Preta del Indios at the blog: AbonoChar LLC.