Bioconversion and characterization of watermelon rind waste‐based microcrystalline cellulose: A green alternative to synthetic reinforcements

The increasing accumulation of agricultural waste from watermelon ( Citrullus lanatus ) represents a substantial environmental concern, particularly in view of the extensive production and consumption of the fruit on a global scale. This study investigated the valorization of watermelon waste, specifically peel biomass, through the extraction of microcrystalline cellulose (MCC) using acid hydrolysis, providing an eco‐friendly and value‐added waste management solution. To produce high‐purity MCC, the watermelon peel underwent successive bleaching, alkali treatment, and acid hydrolysis. Characterization indicated a crystallinity index of 71.65% and a crystallite size of 31.14 nm, showing good structural order. Fourier transform infrared analysis indicated the elimination of lignin and hemicellulose, whereas SEM and AFM revealed a homogeneous and slightly rough surface shape. TGA verified thermal stability, with substantial deterioration occurring at 319.53 °C and a 28% char residue at 600 °C. The isolated MCC had an average particle size of 77.5 μm, making it suitable for medicinal, food packaging, and biodegradable polymer applications. This work proposes a sustainable technique for transforming watermelon agro‐waste into a high‐value biomaterial that adheres to the principles of circular economy and green chemistry.