Porosity of a coal ash clearly visible to the naked eye. (Photo: Andreas Thomsen)


A great article with various recipes to activate biochar:

Ways of Making Terra Preta: Biochar Activation
by Hans-Peter Schmidt
Biochar is not a fertilizer, but rather a nutrient carrier and a habitat for microorganisms. First of all, biochar needs to be charged to become biologically active in order to efficiently utilize its soil-enhancing properties. There are numerous methods of activating and producing substrates similar to terra preta aside from mixing biochar with compost. …