Among different CO 2 removal strategies, pyrolysis of biomass plays a prominent role . The residual carbonrich char (biochar) obtained in this is a negative CO 2 ]. Yet, pyrolysis of biomass results in a carbon sink (C-sink) only if the biochar can be stored for very long times . Although biochar has significantly higher permanence compared to biomass , it needs to be secured that the removed carbon does not come back to the atmosphere due to combustion or gradual decomposition. The issue of permanent storage of the biochar is challenging, considering the large quantities that may need to be accommodated if this climate action becomes global. One currently considered strategy is storing the biochar in soils, see e.g. .