A significant increase in carbonyl species is observed with a combination of SPC and NaOH. An absorption maximum of the carbonyl species is reached after 60 minutes, but no significant change in absorption can be observed after only 15 minutes of reaction time. The basic activation of the hydrogen peroxide is probably the reason for this. In a strongly basic environment, hydrogen peroxide forms the perhydroxyl ion with hydroxide ions (Figure ) . As further reactive species, hydroxyl radicals and superoxide anion radicals, among others, can be generated by homolytic cleavage. High temperatures and the presence of transition metals (Fe 2+ on the surface of bowl and balls) further favour radical formation in basic environments . Temperature measurements (Fig. ) showed that in all experiments, except the SPC/NaOH series, temperatures of 35°C were not exceeded as a maximum value. For the SPC/NaOH series, however, a maximum value of approx. 50°C was observed after 5-6 minutes of reaction time. Presumably, these high temperatures result from an uncontrolled formation of radicals and their reaction with lignin. The high temperature together with the increased basicity due to the NaOH as well as the presence of transition metals in the form of the stainless-steel cup and beads could indicate that the radical species observed in wet chemical experiments are also the reactive species in the mechanochemical experiments.