Perspectives towards biomass valorization in integrated circular biorefineries: Insights from sorghum residue-based value chains in Sub-Saharan Africa

Sorghum residues are an abundant, drought-resilient lignocellulosic feedstock across Sub-Saharan Africa (SSA) with underexplored potential in circular biorefinery systems. Their underutilization stems from limited technological development, fragmented supply-chain structures, and a lack of integrated biorefinery models tailored to low- and middle-income contexts. This review examines how sorghum residues can be optimally integrated into circular biorefineries, identifies promising conversion configurations and product portfolios across regional contexts, and synthesizes the technical, economic, and policy barriers limiting large-scale deployment in SSA. The review integrates evidence on feedstock physicochemical characteristics, conversion performance across biochemical, thermochemical, and hybrid pathways, and multi-product valorization strategies, highlighting sweet sorghum systems in which co-valorization of juice and bagasse significantly enhances overall biomass utilization. Comparative synthesis indicates that sorghum exhibits favourable water-use efficiency, low input requirements, and competitive per-hectare energy yields under marginal-land conditions, supporting its suitability for decentralized and modular biorefinery concepts. Circular design principles such as cascading valorization, energy and nutrient recycling, and strategic co-product integration (e.g., biochar, digestate, lignin-derived chemicals) emerge as central to improving economic resilience and environmental performance. The review concludes by articulating transferable design insights and targeted research and policy priorities, including pilot-scale techno-economic and life-cycle assessments, supply-chain aggregation mechanisms, and modular processing technologies, to accelerate circular biorefineries that support low-carbon development and rural value creation in SSA and beyond.