OP is possibly posting the query in relation to what they've heard about Terra Preta, which is a dark and healthy soil found across the Amazon, rich in charcoal

OP is possibly posting the query in relation to what they've heard about Terra Preta, which is a dark and healthy soil found across the Amazon, rich in charcoal, and suspected to be significantly anthropogenic in origin... https://en.wikipedia.org/wiki/Terra_preta https://en.wikipedia.org/wiki/Terra_preta - ed I think charcoal's use in this context is more in terms of a structural matrix, rather than itself being of 'nutritious value'.