Finding Trends in Biochar Types to Maximize Carbon Dioxide Adsorption

Carbon dioxide (CO₂) emissions are a prominent factor in driving global climate change, intensifying concerns over global temperatures and socio-environmental instability. In addressing this worldwide challenge, biochar – a byproduct of biomass pyrolysis and a soil amendment widely used in facilitating agriculture and gardening – has gained favor for its ability to sequester carbon in the soil. In addition to its use as a soil amendment, it has been shown particularly with activation procedures to be a good adsorbent for various toxins and more recently for CO₂ from the air. Nonetheless, a significant knowledge gap remains regarding the identification of activators, both physical and chemical, that can be used to optimize the adsorption capacity. This study reviews 24 papers in the literature to uncover activators with high CO₂ adsorption capacities. Amongst the 11 activation processes evaluated in this review, specific activators, namely Potassium hydroxide (KOH) + CO₂, Aluminum (Al), Steam, and Iron (Fe), emerge as leaders for their potential for enhancing carbon capture when used to activate biochar. The study also investigates feedstock selection and the conditions under which biochar is produced. An analysis of feedstock was conducted to identify the most effective biochar types. From this subset of high-performing feedstocks, patterns in relation to 20 associated variables were analyzed. Among these, 2 specific parameters – Nitrogen content, and Carbon content – were recognized as potential predictors of feedstocks with a strong likelihood of yielding high-performing biochar after pyrolysis. This study forms the foundation for future investigations, including the development of a machine-learning model for identification of trends in CO₂ adsorption.