The application of biochar for CO₂ capture: influence of biochar preparation and CO₂ capture reactors

This work investigates three types of biochar (bamboo charcoal, wood pellet, and coconut shell) for postcombustion carbon capture. Each biochar is structurally modified through physical (H₂O, CO₂) and chemical (ZnCl₂, KOH, H₃PO₄) activation to improve carbon capture performance. Three methods (CO₂ adsorption isotherms, CO₂ fixed-bed adsorption, and thermogravimetric analysis) are used to determine the CO₂ adsorption capacity. The results show that a more than 2.35 mmol·g^–1 (1 bar, 298 K) CO₂ capture capacity was achieved using the activated biochar samples. It is also demonstrated that the CO₂ capture performance by biochar depends on multiple surface and textural properties. A high surface area and pore volume of biochar resulted in an enhanced CO₂ capture capacity. Furthermore, the O*/C ratio and pore width show a negative correlation with the CO₂ capture capacity of biochars.