Recent advances in biochar-based materials for CO₂ capture: From preparation to application in value-added chemicals and fuels

The escalating rise in global carbon dioxide (CO₂) emissions, primarily from the combustion of fossil fuels, necessitates the advancement of efficient carbon capture technologies. Biochar has emerged as a promising adsorbent due to its tunable properties, cost-effectiveness, and low emissions production. This review presents recent advancements in engineered biochar for CO₂ capture, including biochar modification strategies such as physical treatment, chemical activation, and heteroatom (N, S) doping, which significantly enhance CO₂ capture capacity. Engineered biochar’s achieved CO₂ adsorption capacities up to 7.52 mmol/g at 1 bar and 25 °C, due to the development of microstructure < 1 nm and surface functional groups (N/O-containing). Chemical activation methods have achieved ultrahigh surface areas exceeding 1700 m²/g, while surface doping enhances CO₂ uptake. However, critical challenges remain, including a loss of adsorption stability of more than 20 % after 10 cycles and the need for upscaling production for industrial applications. Beyond capture, engineered biochar in CO₂ conversion to value-added chemicals and fuels, such as syngas, methane, and methanol. Innovative strategies such as functionalization, machine learning (ML) algorithms, and AI-guided design approaches are discussed as future directions to optimize performance. This review identifies critical research gaps and emphasizes the need for pilot-scale validation to bridge laboratory developments with large-scale implementation. Overall, this work positions engineered biochar as a key enabler in next-generation CO₂ mitigation technologies aligned with global carbon neutrality goals.