Biochar Slurry CO₂ Capture in a Rotating Bed Reactor: A Proof-of-Concept Study

Carbon dioxide capture remains central to climate mitigation, yet conventional amine-based systems carry high energy penalties, solvent degradation, and corrosion concerns. Biochar derived from biomass pyrolysis offers low-cost CO₂ adsorption alongside waste valorisation, while mineral carbonation provides a thermo-dynamically stable, permanent sequestration route. Coupling rapid adsorption with durable mineralisation within a single intensified process could deliver both adsorption speed and mineralisation permanence. To date, fewer studies have integrated adsorption and in-pore mineralisation within a rotating bed reactor, where high centrifugal acceleration enhances gas–liquid–solid mass transfer. This work develops and evaluates such a hybrid system using a calcium-loaded biochar slurry. This work is currently at the proof-of-concept stage; therefore, the abstract describes the proposed framework and experimental approach and does not include or imply validated results.

Biochar will be produced from walnut shell via pyrolysis at a high temperature, then KOH-activated (2:1) to maximise micropore development. Calcium nitrate impregnation (0.5:1 and 1:1) followed by calcination at 450 °C deposits CaO within the pores, so CO₂ captured inside reacts permanently to form CaCO₃. The feed materials will be characterised by BET surface area analysis, XRD, FTIR, TGA, SEM-EDX. CO₂ capture experiments are planned to be conducted in a rotating bed reactor (manufactured by Spinchem, Sweden). The solvent of sodium hydroxide with an appropriate concentration will be used to capture carbon dioxide. The framework is expected to demonstrate enhanced CO₂ capture efficiency through improved gas-liquid-solid contact, provide three-dimensional spatial proof of in-pore CaCO₃ formation, and contribute toward scalable carbon capture, utilisation and storage (CCUS) and carbon-neutral technologies.