Integrated valorization of mango kernel biomass for biodiesel and biosyngas production via optimized transesterification and gasification using response surface methodology

Mango kernel biomass is an abundant yet underutilized agro-industrial residue with considerable potential for sustainable renewable energy production. This study examines the integrated valorization of mango kernel oil and its solid residue for the concurrent production of biodiesel and biosyngas, employing Response Surface Methodology (RSM) to optimize key process variables. Oil was extracted from mango kernels using Soxhlet extraction and converted to biodiesel via sodium methoxide–catalyzed transesterification, with operating conditions optimized through a Central Composite Design (CCD). An optimum experimental biodiesel yield of 92.19% was obtained at a methanol-to-oil molar ratio of 9:1, catalyst loading of 3 wt%, reaction temperature of 65 °C, and reaction time of 60 min. Fuel characterization revealed that most properties met the ASTM D6751 specifications, including viscosity, cetane number, and oxidative stability. The defatted kernel residue was subsequently converted to biosyngas through steam gasification in a laboratory-scale bubbling fluidized-bed reactor. Process parameters, including gasification temperature, steam-to-biomass ratio (S/B), and particle size, were optimized using a Box–Behnken Design (BBD). Maximum experimental syngas compositions of 37.59% H₂, 18.85% CO, and 10.61% CH₄ were achieved at 900 °C, S/B = 0.60, and 2.50 mm particle size. Statistical analysis (ANOVA) confirmed the strong influence of both individual and interaction effects on biodiesel yield and syngas composition. The integrated CCD–BBD optimization strategy enables efficient energy recovery from mango kernel biomass and establishes a sustainable, non-edible feedstock pathway for biofuel production, with particular relevance to biomass-rich regions such as Nigeria, where sustainable energy diversification is critically needed.