This study investigates the transformation and characterisation of abundant crop residues found primarily in Gunupur, Rayagada, such as rice husk, cotton stem, and coconut shell, into biochar adsorbents through pyrolysis. Biochar, a car-bon-rich solid from biomass pyrolysis, was investigated here across multiple types produced via slow pyrolysis at 235– 800°C. A comparative analysis reveals distinct physicochemical properties and adsorption capacities, highlighting their potential for sustainable environmental remediation. In this study efficiency of the biochar primarily made of rice husk, cotton stem and coconut shell was compared for making a better adsorbent. The biochars were characterised in terms of pore size, surface area analysis, chemical composition, and crystalline structure. Scanning electron microscopy (SEM) is used to analyse the morphology and characteristics of different biochars. XRD analysis was done to detect graphitic carbon peaks (like d002 and d101), quartz (SiO₂) and other minerals formed during pyrolysis. Higher pyrolysis tem-peratures typically increase crystallinity, showing sharper peaks for ordered carbon structures. The Brunau-er-Emmett-Teller (BET) method employs N₂ adsorption-desorption isotherms at 77 K to determine total surface area, pore volume, and pore size distribution, which govern biochar's sorption performance. CHNS elemental analysis was conducted to quantify the percentages of carbon (C), hydrogen (H), nitrogen (N), and sulphur (S) in the biochar sample. Fourier transform infrared (FTIR) is used to characterize the molecular structure of biochar by detecting vibrational modes of bonds in functional groups like hydroxyl (-OH), carbonyl (C=O), and aromatic C=C. These insights help predict biochar stability and reactivity in applications such as carbon sequestration. Comparative findings identify rice husk biochar produced at optimal pyrolysis temperatures as exhibiting superior surface area, functional diversity, and adsorp-tion efficiency over cotton stem and coconut shell variants for sustainable environmental remediation.

Biochar, Pyrolysis, Adsorbent, Scanning Electron Microscopy (SEM), Physicochemical Properties, Comparative Analysis, Surface Area, Crystallinity, Adsorption Capacity