Progress in the conversion of biodiesel-derived crude glycerol into biofuels and other bioproducts

Diversification of the global energy scenario to achieve renewable, clean, and affordable energy sources has escalated biodiesel production in recent decades. Crude glycerol (CG), a major byproduct of the transesterification of triglycerides to biodiesel, is often disposed of inappropriately and pollutes the environment. This review explores the advancements in the conversion of CG into biofuels and other bioproducts. The study provides an overview of major techniques for CG purification and the feasibility of biochemical, thermochemical, physicochemical, and electrochemical glycerol upgrading approaches. The outcomes of recent studies on the conversion of glycerol into biofuels such as bioethanol, biohydrogen, biomethane, biohythane, and other bioproducts are highlighted. The techno-economic analysis and life cycle assessment of the CG conversion shows the feasibility and environmental sustainability of the process in contributing to circular bioeconomy, energy security, and sustainable waste utilization. Further studies in advanced metabolic engineering and the development of integrated biorefinery systems are recommended. • Purification of crude glycerol (CG) via appropriate techniques converts it into a useful resource. • Implementation of sustainable upgrading approaches converts CG into biofuels and other products. • Outcomes of recent studies on the conversion of CG into biofuels and other products are reviewed. • TEA, LCA, implications, and future research directions of CG upgrading are highlighted.