Multi-dimensional maize biomass utilization: Mitigating existing agro-waste by meaningful value addition

Maize stover is an abundantly available biomass across different parts of the world, accounting for about 47-50 % dry mass of the maize plant. Primarily comprising of cobs, stems, leaves, and husks, maize biomass contains significant amount of cellulose, hemicellulose and lignin. Utilization of these lignocellulosic components to produce a suitable spectrum of marketable products such as hydrolytic enzymes, second-generation bioethanol, furfurals, organic acids, biohydrogen, biopolymers, prebiotic xylooligosaccharides, etc., holds promise to generate new markets and complement the economic viability of first-generation ethanol. Maize biorefineries can provide self-sufficient and sustainable options to break wheat-paddy crop rotation cycle and enhance sustainability of bioconversion processes if the agro-residues are efficiently harnessed. This study aims to present an integrative view on global generation and utilization of maize biomass while emphasizing on multi-dimensional product formation in a circular approach. Emerging pretreatment techniques such as deep eutectic solvents, biphasic fractionation and integrated carbon-capture strategies are evaluated. Process modifications like enzyme recycling and the suitability of valorized products for high-value markets to enable a holistic and profitable maize lignocellulose biorefinery are discussed. In addition to compositional and process-based discussions, techno-economic analyses and life cycle assessments are reviewed to quantify capital and operating costs, greenhouse-gas footprints, and overall environmental impacts. Current challenges and policy interventions to achieve industrial scale workflows are also highlighted. The review offers a comprehensive perspective on the present landscape of maize biomass valorization using different technologies and varied products, catering to different markets. Finally, future research directions to bridge current technological gaps and accelerate commercial deployment are outlined.