Upcycling Waste Biomass–Production of Porous Carbonaceous Supports from Paper Mill Sludge and Application to CO₂ Conversion

Abstract The urgent need for sustainable waste management strategies has led to the exploration of innovative approaches for the valorization of waste. In this study, a method is proposed for carbonizing waste biomass materials, particularly paper mill waste sludges (primary and biological) and knots, to produce porous carbonaceous supports. Through an initial hydrothermal carbonization followed by carbonization with nitrogen flow, porous carbon materials are successfully generated. The findings of this investigation validate the successful generation of effective carbonaceous supports utilizing waste biomass materials. These materials are then evaluated for their effectiveness as porous supports in the ionic liquid‐catalyzed cycloaddition reaction of CO₂ to styrene oxide, achieving a remarkable conversion rate of up to 98% and an impressive selectivity exceeding 99%. Additionally, the results underscore the significant impact of the selected IL on the overall conversion process. Overall, this study presents a promising pathway for the valorization of paper mill waste sludge through the production of porous carbon materials with potential applications in catalysis and beyond.