Increased global attention to sustainable natural resources has encouraged the exploration of plant-based biomass as an alternative precursor for activated carbon production. This study aimed to develop and comprehensively characterize granular activated carbon (GAC) derived from Melaleuca cajuputi var. cumingiana wood waste, an abundant and underutilized biomass source in South Kalimantan, Indonesia. The preparation process involved dehydration, followed by carbonization at 500°C for 1 hour, and subsequent separate chemical activations with 10% H₃PO₄ and 10% KOH for 24 hours. The resulting samples—designated as GAC0 (non-activated), GAC1 (H₃PO₄-activated), and GAC2 (KOH-activated)—were washed, dried at 105°C for 3 hours, and analyzed using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM–EDS). FTIR analysis revealed distinct chemical modifications following activation. GAC1 exhibited evident phosphate-related absorption peaks, confirming the successful incorporation of oxygenated phosphorus groups. Meanwhile, GAC2 showed enhanced hydroxyl and carbonyl functional groups, indicating increased surface reactivity. SEM observations revealed improved pore development in both activated samples, particularly in GAC2, which displayed more heterogeneous surface morphology. EDS results further supported the variation in elemental composition, which was influenced by the type of chemical activator. Overall, the findings demonstrate that M. cajuputi wood waste can be effectively converted into high-quality activated carbon with favorable physicochemical characteristics. This work highlights the viability of locally generated biomass as a sustainable and economical precursor for natural adsorbents, offering promising applications in environmental remediation and contributing to regional waste valorization efforts. © 2026 Ishak et al.