Development and techno-economic analysis of Calophyllum inophyllum biorefinery for the production of biodiesel, biohydrogen, bio-oil, and biochar: Waste to energy approach

The biorefinery integrates the biomass conversion process to produce a range of value products for a circular bioeconomy in an environmentally sustainable manner. The present study reports the biorefinery of Calophyllum inophyllum seeds for biochar, bio-oil, biodiesel, and biohydrogen production. Biochar from the Calophyllum inophyllum husk was used as an effective adsorbent for treating dairy effluent to remove toxic chemicals. The Langmuir and Freundlich adsorption isotherms and kinetics were investigated and reported. The bio-oil obtained was converted into biodiesel using transesterification by industrial waste dolomite. The maximum FAME yield of 91.67% was obtained after the reactive distillation under an optimal methanol-to-oil ratio of 16:1, the catalyst of 3 wt%, a flow rate of 0.2 mL min−1, and a temperature of 80 °C. The performance and emission analysis of 10% biodiesel and diesel were compared. A 10% biodiesel blend reduced CO emissions by 14.58% and HC emissions by 19.54% for full load conditions. Biohydrogen was produced through simultaneous saccharification and dark fermentation using deoiled cake by cocultures of Enterobacter aerogenes and Trichoderma harzianum. A maximum of 44.5 mL H2/L was obtained after the optimization of process parameters, such as cake concentration, culture ratio, and pH. Further, the techno-economic analysis was performed to evaluate the financial flow of the proposed biorefinery. Using Aspen Plus Economic Analyzer, the payback period for the biorefinery process for the Biohydrogen, Biodiesel, Bio-oil, and biochar from Calophyllum inophyllum was calculated to be 4.04 years and for the biohydrogen production plant, it was found to be 3.30 years with selling price of biohydrogen taken as 2.5 $ per kg. The results of the techno-economic analysis show that the biorefinery process is extremely feasible and profitable. Thus, the present research demonstrated the biorefinery of non-edible Calophyllum inophyllum seed for obtaining sustainable energy and byproducts with net zero carbon emissions.