Towards a sustainable conversion of biomass/biowaste to porous carbons for CO2 adsorption: recent advances, current challenges, and future directions

Solid adsorbents are considered very attractive for selective CO2 removal from main emission sites, and this method was found suitable for post-combustion carbon capture owing to its cost-effective and retrofit nature. Among various solid adsorbents contested for CO2 adsorption, biomass-derived porous carbons (BPCs) have emerged as an important class due to their unique characteristics, for instance, remarkable textural features, less expensive and abundant precursors, surface chemistry, and tunable porosity, and therefore are considered appropriate for CO2 capture under diverse conditions. Different synthetic strategies have been employed to produce suitable textural as well as physicochemical properties in BPCs to effectively use them for CO2 adsorption applications. In this review, we have comprehensively discussed the origin and compositional analysis of biomass, its conversion strategies (e.g., pyrolysis, hydrothermal carbonization, physical or chemical activation, and sol-gel process), non-functionalized and functionalized BPCs as CO2 adsorbents, the role of heteroatom, for instance, nitrogen, oxygen, and sulfur on BPC's textural features and CO2 adsorption performance, the mechanism behind CO2 capture (either physisorption or chemisorption), a brief note on the main approaches for CO2 capture (e.g., pre-combustion, post-combustion, and oxy-combustion), leading factors that could influence the CO2 adsorption performance of BPCs (role of higher carbon content, processing temperature and time, activating agent and impregnation ratio, etc.), and current major challenges. Finally, a summary is provided that discusses concluding remarks and future research directions with possible solutions for the effective development of BPCs to seek excellent CO2 capture and conversion applications.