Effects of feedstock and pyrolysis temperature on carbon stabilization and mineral functionality of biochars

Understanding how feedstock composition and pyrolysis conditions regulate carbon stabilization, mineral transformation, and surface characteristics is critical to predicting biochar evolution across biomass resources. This study examined how feedstock type and pyrolysis temperature influence physicochemical, mineralogical, and surface properties of biochars from sugarcane bagasse (SB), pistachio branches (PB), and cattle manure (CM) at 300, 500, and 700 °C. Increasing pyrolysis temperature reduced yield, zeta potential, moisture, volatile matter, hydrogen, oxygen, H/C, O/C, and cation exchange capacity (CEC), while increasing fixed carbon, pH, pHpzc, EC, ash, and organic carbon content. At 700 °C, lignocellulosic biochars showed higher carbon and fixed-carbon contents and lower H/C and O/C ratios, indicating greater carbonization and aromatic condensation. In contrast, CM biochars generally showed higher yields, pH, CEC, ash content, and mineral concentrations than lignocellulosic biochars, whereas their EC values were lower. Their elemental and oxide compositions were richer, with more pronounced crystalline structures. These features indicate pronounced mineral inheritance from the mineral-rich feedstock. These findings provide a physicochemical framework for biochar evolution, linking carbon structure, mineral composition, surface chemistry, and porosity to feedstock–temperature-dependent characteristics. Such insights provide a basis for future environmental and agricultural application-oriented studies, while direct performance evaluations remain necessary before practical recommendations can be made.