As the world searches for practical ways to slow climate change, scientists are taking a closer look at an unlikely material: biochar, a carbon-rich substance made from agricultural residues, wood waste, sewage sludge, animal manure, and other biomass. A new review published in Carbon Research highlights how engineered biochar, especially heteroatom-doped biochar, could become a sustainable and cost-effective adsorbent for capturing carbon dioxide.
Rising atmospheric carbon dioxide levels remain a major driver of global warming and extreme weather. Carbon capture, utilization, and storage technologies are widely viewed as important tools for reducing emissions, but the capture step is often costly and energy intensive. Conventional solid adsorbents, including zeolites, metal-organic frameworks, and activated carbon, can show strong performance, but many still face challenges related to cost, stability under humid conditions, large-scale production, or regeneration energy.
Biochar offers a different route. Produced through thermochemical conversion of biomass and organic waste, biochar is renewable, relatively low-cost, and environmentally friendly. However, raw biochar often has limited pore structure and insufficient surface chemistry, which restrict its ability to capture carbon dioxide efficiently. The review explains that carefully engineered biochar can overcome these limitations by tuning pore size, surface area, hydrophobicity, alkalinity, and functional groups.
"Biochar is not just a waste-derived carbon material. With rational engineering, it can be transformed into a functional adsorbent for sustainable carbon capture," said corresponding author Xiangping Li. "Our review shows that heteroatom doping is one of the most promising strategies for improving both the physical and chemical interactions between biochar and carbon dioxide."
The review focuses on heteroatom doping, a modification strategy that introduces elements such as nitrogen, sulfur, phosphorus, and boron into the biochar structure. These atoms can change the electronic distribution of the carbon framework, create active adsorption sites, and improve interactions with acidic CO2 molecules. Among these dopants, nitrogen has attracted particular attention because it can enhance surface basicity, adjust pore structure, and strengthen both physical adsorption and chemisorption.
According to the authors, nitrogen-containing groups such as pyridinic nitrogen, pyrrolic nitrogen, and pyridone-like structures can improve CO2 affinity through Lewis acid-base interactions and hydrogen bonding. At the same time, micropores, especially ultramicropores smaller than 0.7 nanometers, are critical because their size closely matches the kinetic diameter of CO2 molecules. This allows CO2 to be trapped more effectively through micropore filling and van der Waals interactions.
The review also compares different engineering pathways. Physical activation using CO2 or steam can increase porosity and surface area, while chemical activation and heteroatom doping can enrich surface functional groups. The authors note that pre-modification doping, in which heteroatoms are introduced during biomass carbonization, often provides better doping efficiency and structural stability than post-modification of already-formed biochar. Co-doping strategies, such as nitrogen-phosphorus or nitrogen-sulfur doping, may further improve adsorption by creating synergistic effects.
Beyond laboratory performance, the review emphasizes the need to address practical barriers before engineered biochar can be widely deployed. These include techno-economic feasibility, regeneration energy costs, standardized characterization methods, long-term cyclic stability, and life-cycle assessment. The authors also point to machine learning as a promising tool for accelerating material design by linking biomass feedstocks, preparation conditions, pore structures, surface chemistry, and adsorption performance.
"Future progress will depend on balancing physical adsorption and chemical adsorption," said corresponding author Peng Liang. "The goal is to design biochar materials that maintain high microporosity while introducing the right surface chemistry for selective and energy-efficient CO2 capture."
By summarizing recent advances and remaining challenges, the review provides a roadmap for developing engineered biochar as a scalable and sustainable material for carbon capture. As global demand grows for low-carbon technologies, waste-derived biochar could help turn biomass residues into useful tools for climate mitigation.
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Journal reference: Li, X., Li, X., Zhang, C. et al. Recent advances in the development of engineered biochar for CO2 adsorption: Research on heteroatom-doped biochar. Carbon Res. 5, 26 (2026).
https://doi.org/10.1007/s44246-026-00264-6
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About Carbon Research
The journal Carbon Research is an international multidisciplinary platform for communicating advances in fundamental and applied research on natural and engineered carbonaceous materials that are associated with ecological and environmental functions, energy generation, and global change. It is a fully Open Access (OA) journal and the Article Publishing Charges (APC) are waived until Dec 31, 2025. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon functions around the world to deliver findings from this rapidly expanding field of science. The journal is currently indexed by Scopus and Ei Compendex, and as of June 2025, the dynamic CiteScore value is 15.4.
