Comparative Morphological and Thermal Analysis of Biochar from Oak, and from Oak, Pine and RDF Blends, in a Downdraft Gasifier

This study investigates the influence of feedstock blending on the structural and thermal properties of biochar produced via downdraft gasification at 850 °C. Biochars from 100% oak, a 1:1 oak-–pine blend, and a ternary blend of 50% oak, 30% pine, and 20% RDF were analyzed using SEM, BET, TGA, XRD, Raman spectroscopy, and CHN elemental analysis. The oak biochar exhibited the highest surface area (107.7 m2/g) and fixed-carbon content (79.94%), while the RDF-based biochar showed a 99.2% decrease in surface area (0.86 m2/g) and a 19.7% reduction in fixed carbon. These findings underscore RDF’s detrimental impact on porosity and stability, despite its waste valorization potential, suggesting its limited use in applications requiring high adsorption or structural integrity. Further studies should optimize RDF preprocessing and blending ratios to balance sustainability with functional performance.