Fig. 8

(A) FTIR spectrum of spent mushroom substrate-derived biochar (SMS-B), showing characteristic absorption peaks at 3417–3423 cm⁻1 (O–H stretching), 1618 cm⁻1 (C = C and C = O stretching in aromatic rings), and 1045 cm⁻1 (C–O stretching). (B) XRD pattern of SMS-B, indicating the presence of crystalline minerals such as SiO₂, CaCO₃, KCl, and CaSO₄, with distinct peaks around 25.5, 30°, and other relevant 2θ positions.