High-Pressure Adsorption of CO₂ and CH₄ on Biochar-A Cost-Effective Sorbent for In Situ Applications

The search for an effective, cost-efficient, and selective sorbent for CO₂ capture technologies has been a focus of research in recent years. Many technologies allow efficient separation of CO₂ from industrial gases; however, most of them (particularly amine absorption) are very energy-intensive processes not only from the point of view of operation but also solvent production. The aim of this study was to determine CO₂ and CH₄ sorption capacity of pyrolyzed spruce wood under a wide range of pressures for application as an effective adsorbent for gas separation technology such as Pressure Swing Adsorption (PSA) or Temperature Swing Adsorption (TSA). The idea behind this study was to reduce the carbon footprint related to the transport and manufacturing of sorbent for the separation unit by replacing it with a material that is the direct product of pyrolysis. The results show that pyrolyzed spruce wood has a considerable sorption capacity and selectivity towards CO₂ and CH₄. Excess sorption capacity reached 1.4 mmol·g^-1 for methane and 2.4 mmol·g^-1 for carbon dioxide. The calculated absolute sorption capacity was 1.75 mmol·g^-1 at 12.6 MPa for methane and 2.7 mmol·g^-1 at 4.7 MPa for carbon dioxide. The isotherms follow I type isotherm which is typical for microporous adsorbents.