A Critical Evaluation of Sustainability Practices, Waste Management Strategies, and Circular Economy Principles in Sago Processing Optimisation

This narrative review offers a critical, decision-oriented synthesis of sustainability practices, waste management strategies, and circular economy levers for optimising Metroxylon sagu (sago) processing at mill scale. Evidence from 2000 to 2025 is organised against two frames: the circular economy principles (eliminate waste and pollution, circulate materials at their highest value, and regenerate natural systems) and the ISO 14040/44 life cycle stages. We evaluate options through five adoption lenses: technology, environment, economics, culture, and regulation and link each intervention to mill-level key performance indicators (e.g., starch yield, process water uses per tonne of starch, effluent chemical/biological oxygen demand, energy displacement, and payback). Three propositions emerge. Firstly, source-level loss prevention, combined with inline starch recovery and process water recirculation, consistently delivers the most significant near-term reductions in wastewater strength while preserving material value. Secondly, treatment methods that also recover energy, such as anaerobic digestion with heat recovery or combined heat and power, become financially robust when compliance signals (standards/fees) are paired with renewable energy incentives and concessional finance. Thirdly, materials-level valorisation of fibrous residues (hampas) as quality-controlled feed or benignly functionalised sorbents/nanocellulose can retain a higher value than energy recovery, provided quality assurance, reagent loop closure, and reliable offtake are in place. Wastewater-to-bacterial cellulose films show promise but remain at an intermediate level of technology readiness. The review contributes (i) an explicit mapping from challenge → strategy → performance metric → circular principle, (ii) a mechanism-based policy table linking instruments to adoption economics, and (iii) a prioritised bundle for small- and medium-scale mills (starch recovery and water recirculation → anaerobic digestion with heat recovery → targeted materials routes). Limitations stem from heterogeneous reporting and contextual variation; a focused agenda is proposed for standardised metrics, seasonal stability trials, and transparent cost tracking. Collectively, these findings translate circular economy intent into bankable, mill-level action.