A comprehensive review of methods for valorisation and production of bioproducts from various cassava wastes
Cassava is a key tropical crop; however, its processing generates large volumes of residues, including peels, bagasse, leaves, stems, and wastewater. Although these wastes are rich in starch, fibre, and lignocellulosic components with high biotechnological potential, they remain largely underutilised. In this context, this review examines current strategies for the recovery and valorisation of cassava processing residues, encompassing physical, chemical, biological, and enzymatic pretreatments, as well as emerging technologies aimed at biofuel and bioproduct generation. Hydrothermal pretreatment stands out for offering a balanced performance between efficiency and inhibitor formation, while acid pretreatment maximises hemicellulose solubilisation but generates higher levels of toxic compounds. Alkaline pretreatments promote effective delignification and enhance enzymatic accessibility, albeit producing effluents that require further treatment. Biological and enzymatic approaches present environmental advantages and low inhibitor formation, although their application is limited by slower kinetics. Emerging technologies, such as ultrasound and non-thermal plasma, show promising potential to enhance sugar release and reduce hydrolysate toxicity, despite the limited number of studies specifically focused on cassava residues. Overall, the integration of complementary routes emerges as a robust strategy to maximise the production of bioethanol, biogas, biohydrogen, and organic acids from cassava wastes. Biorefinery models consistently demonstrate significant energy gains and reduced environmental impacts, reinforcing cassava residues as a strategic platform for circular economy applications. Consequently, the integrated valorisation of cassava processing wastes represents a relevant opportunity to enhance technological sustainability and environmental performance across cassava value chains.