“…17,18 Previously, it has been shown that biomass rich in lignin can be used for the production of valuable chemicals via depolymerisation processes. 19,20,47 Wet air oxidation (WAO) is an effective and extensively used industrial oxidation process 21 for organic and inorganic aqueous solutions or suspensions. Typical conditions for wet air oxidation to produce phenolic compounds, depending on the source, ranges from 150-250°C and 1-50 bar.…”