Brewer’s spent grain as a sustainable feedstock for high value carboxymethyl cellulose

Brewer's spent grain (BSG), the major by-product of the brewing industry, represents an abundant yet underutilized lignocellulosic resource with high potential for sustainable material production. This study aimed to valorize BSG as a renewable feedstock for synthesizing carboxymethyl cellulose (CMC). Cellulose was extracted from BSG through sequential alkali and bleaching treatments, and alkaline hydrolysis conditions were optimized at 98 °C, 1.4 wt% NaOH, for 2.5 h, yielding high-purity cellulose. The purified cellulose was subsequently converted into CMC via etherification and characterized by FTIR, XRD, SEM, particle size analysis, and ¹H NMR spectroscopy. The CMC exhibited a crystallinity index of 76.30%, rod-like morphology, and an average particle size of 309.40 nm. NMR confirmed successful carboxymethyl substitution, with a degree of polymerization of 13.36 and a molecular weight of 9,567 g/mol. These properties suggest good solubility and rheological stability, suitable for food, pharmaceutical, and biodegradable material applications. This work demonstrates an efficient, eco-friendly approach to converting brewery waste into high-value cellulose derivatives, supporting bio-circular-green economy principles and sustainable materials innovation.