Waste-derived mesoporous biochar for glycerol to glycerol carbonate upgrading: intensified process design and techno-economic analysis

Abstract

Biochar-based green catalysts are increasingly important for sustainable chemical manufacturing, offering a low-cost and environmentally friendly approach to catalysts by utilizing agricultural waste materials rich in natural minerals. This study developed a self-activated potassium-rich mesoporous biochar catalyst derived from banana bunch stalks (BS) for glycerol carbonate (GyC) synthesis via transesterification with dimethyl carbonate (DMC). Unlike conventional alkali-impregnated catalysts, the biochar exhibited intrinsic basic active sites without any external chemical modification, enhancing its sustainability and cost-effectiveness. BS, an abundant agricultural waste material with a high alkaline content, were transformed into a heterogeneous catalyst through controlled pyrolysis. The research employed response surface methodology with a central composite design to optimize the reaction conditions for GyC yield. The highest GyC yield was found to be 92.40%, under the derived optimal conditions of: 3.45 wt% catalyst loading, 3.58 : 1 DMC : glycerol molar ratio, 90 °C reaction temperature, and 119 min reaction time. Detailed characterization showed that the catalyst's high potassium content and strong basicity (3.66 mmol g⁻¹) contributed to its catalytic efficiency, establishing a clear structure–activity relationship between intrinsic mineral species and performance. Kinetic studies revealed that the reaction follows a pseudo-first-order mechanism with an activation energy of 55.70 kJ mol⁻¹, confirming a chemically controlled regime under optimized conditions. Importantly, this study integrates catalyst development, reaction optimization, kinetic modelling, process simulation, and techno-economic evaluation within a unified framework, providing a comprehensive assessment of industrial feasibility. Process simulation validated the scalability of the optimized process, achieving a product enrichment of near purity (99.9%). Techno-economic analysis demonstrated that larger production capacities significantly enhanced the profitability, reducing the payback period, and increasing the net present value and internal rate of return. This work demonstrates a scalable waste-to-value catalytic platform that advances circular bioeconomy strategies and sustainable chemical manufacturing for high-value glycerol upgrading.