Optimized process and modeling of waste Gmelina arborea seed pyrolytic oil production and its characterization as a sustainable biofuel

Biofuels from bioresources are a viable renewable energy source, but high prices, the food versus fuel debate, and biodiversity loss limit the demands for bioenergy. Sourcing alternative bioresources from waste with a higher yield and energy value to produce bioenergy, as well as optimizing biofuel refining processes, are crucial for reducing production costs and increasing output to mitigate high prices and feedstock availability. The extracted bio-oil of non-edible seeds of Gmelina arborea is being investigated for transesterification into biofuels, a process that does not entirely maximize the bioenergy generated from the bioresources and generates further waste. However, pyrolysis can convert wholly the lignocellulose seed components into bioproducts with high-quality fuel properties without associated glycerol. Consequently, in this study, pyrolytic oil was produced from waste Gmelina arborea seed, the process parameters were optimized using the surface response methodology with experimental validations, the process model was established, and the pyrolytic oil was characterized. The optimum yield of 54 % at a temperature of 485 °C, a heating rate of 40 °C/min, and a particle size of 0.9 mm were established, and a corresponding regression model equation was developed. The Gmelina arborea seed biomass was revealed to have 81.95 % volatile matter with oil extractives of 44.80 %. The GC-MS analysis shows that the aliphatic hydrocarbon of a cyclic monoterpene occupies the highest concentration of 67.46 %. The fuel properties and the calorific value of 33.69 MJ/kg of the pyrolytic oil compared to ASTM standard specifications for pyrolytic liquid biofuel show suitability for commercial and industrial fuel. The absence of sulfur in the pyrolytic oil elemental analysis adds credence to its usefulness as a sustainable fuel. • The waste Gmelina arborea seed, with a high volatile matter of 81.95 %, is a viable feedstock for pyrolytic oil production. • The Gmelina arborea seed yielded an optimal pyrolytic bio-oil yield of 54 % at 485°C, 40 °C/min, and 0.9 mm particle size. • The developed regression model adequately predicts the seed's pyrolytic oil yield under the pyrolysis process conditions. • Produced pyrolytic oil has 67.46 % cyclic monoterpenes of aliphatic hydrocarbon compounds likened to diesel's long chain.