Closing a biorefinery cycle of giant reed through the production of microporous and reusable activated carbon for CO₂ adsorption

The complete valorisation of all biomass components represents a crucial strategy for developing new biorefinery schemes. This study completed a cascade biorefinery process for the exploitation of holocellulose and lignin fractions of the non-food biomass giant reed (Arundo donax L.). The residual lignin-rich solid fraction, obtained after the selective conversion of hemicellulose and cellulose fractions to valuable bioproducts, was characterised and activated by KOH treatment into microporous activated carbon (AC), to be proposed for CO2 adsorption. The production of AC was optimised by the Design of Experiments technique. Under the optimised process conditions (630 degrees C, KOH/lignin 3.0 wt/wt, 60 min) the AC yield was 34.4 wt% and the CO2 uptake reached 72.3 mg/g, confirming the promising application of this biomaterial. Moreover, the obtained AC showed similar CO2 uptake values over 10 cycles of adsorption/desorption tests, demonstrating its good recyclability, keeping its pristine CO2 uptake capacity.