"Coppicing is a highly skilled way of harvesting wood without chopping down the whole tree (which invariably kills it). Instead, part of the tree is cut, leaving the rest to regrow. Done correctly, regrowth is vigorous, and the same tree can be harvested again every five to ten years, often over hundreds of years." This page is from Vertical Veg, about urban coppicing in Manchester, England. Biochar is just one of the useful byproducts.