Contribution to characterisation of biochar to estimate the labile fraction of carbon

► Feedstock type and pyrolysis conditions influence the degree of biochar carbonisation. ► Intrinsic lability of biochar revealed via spectroscopic and thermogravimetric analysis. ► Wet oxidation provided qualitative and quantitative information on biochar lability. ► C evolved as CO2 from biochar-amended soil after 110 h was related to carbonisation degree.