Figure 2

Van-krevelen diagram with H:C and O:C molar ratios for dead wood (DW) and forest floor (FF) feedstock, biochars and charcoals. The areas in blue, grey, pink and yellow indicate typical values for feedstocks, hydrochars, biochars and wildfire charcoals, respectively25, 37, 47. The dotted lines in the X axis mark the half-lives ranges (>1000 yrs; 100–1000 yrs; and <100 yrs) according to Spokas29.