Evaluating sustainability of CO₂-mediated pyrolysis of lignocellulose

Despite the growing interest in biomass as a carbon-neutral resource, technical challenges have limited its comprehensive utilization. Pyrolysis has emerged as a promising method for reducing the carbon footprint by more effectively valorizing carbon in biomass. This study investigated the use of carbon dioxide (CO₂) in the pyrolysis of pine cone (PC), a lignocellulosic biomass. Thermogravimetric analysis confirmed that lignin was the primary component of the PC. Characterization and quantification of the three pyrolytic products (syngas, biocrude, and biochar) revealed that CO₂ enhanced CO production and the surface area of the biochar, thereby improving its CO₂ adsorption capacity. Additional heat and a Ni catalyst further amplified CO₂'s functionality. The sustainability of the proposed pyrolysis system was evaluated by calculating energy requirements of the pyrolysis processes and the net CO₂ emissions. Catalytic pyrolysis under CO₂ was the most effective, achieving a reduction of 3.34 g of CO₂ per gram of PC.