Coproduction of Biodiesel and Bioethanol from Ricinus communis Seed Through an Integrated Process

The growing demand for renewable energy has spurred an interest in non-edible feedstocks for biofuel production. Ricinus communis (castor) seeds are a promising resource due to their high oil and starch content, as well as their adaptability to marginal lands. This study evaluated the integrated use of R. communis seeds for the production of biodiesel and bioethanol using eco-efficient technologies. Ultrasound-assisted extraction enhanced oil recovery reached a maximum yield of 34%, surpassing the conventional Soxhlet method. Transesterification was optimized through factorial design, achieving a predicted biodiesel yield of 97% (Qualitek 4.0, 90% confidence interval), with an experimental maximum yield of 90.8% under optimal conditions (24:1 methanol-to-oil ratio, 0.4% catalyst, 90% sonication amplitude, 60 min). The biodiesel met international standards for engine applications. Starch from the residual seed cake was hydrolyzed with enzymatic complexes, yielding 6.8 g/L of reducing sugars, equivalent to 91.4% hydrolysis yield. Fermentation of the hydrolysates with Zymomonas mobilis produced 3.1 g/L ethanol, corresponding to 90.8% of the theoretical yield. This integrated approach exemplifies a circular bioeconomy model by combining biodiesel and bioethanol production, maximizing resource utilization, and minimizing waste. The results highlight the potential of R. communis as a sustainable, scalable feedstock for renewable energy, contributing to energy security and environmental sustainability.