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Growing demand for renewable and sustainable energy sources has prompted research into bioethanol production as a viable alternative to hydrocarbon fuel for automobile engines. Based on their high carbohydrate content, Chlorella vulgaris microalgae were chosen for this study as a feasible biomass for bioethanol synthesis. After conducting microwave-based acid hydrolysis with varying acid concentrations of sulfuric acid (H2SO4) for 1–15 min, this study found that 3% H2SO4 for 5 min yielded the highest yield of reducing sugar (6.77 g/L). In this work, the RSM approach of central composite design (CCD) was utilized for modeling and optimization of ethanol fermentation and the MATLAB Simulink approach was employed for the simulation of ethanol fermentation. This study compared the effects of using Saccharomyces cerevisiae yeast for fermentation at different fermentation times (12 to 48 h), temperatures (28 to 32°C), and size of inoculum (0.5–1.5 g/L). Based on the actual and predicted results, the best conditions for fermentation were 36 h of time, 30°C of temperature, and 1.5 g/L of inoculum size. This gave the maximum ethanol concentration of 3.31 g/L. Furthermore, the RSM method provides minimum error and maximum R² value results for ethanol production compared to MATLAB simulation prediction (MSP). In addition, residue biomass from biofuel production is evaluated for its suitability for a further form of biofuel production. This research explores the opportunities for zero-waste biomass utilization in the development of biofuels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chlorella vulgaris biomass was hydrolyzed by microwave irradiation with H 2 SO 4. • Maximum reducing sugar was achieved at 3% of H 2 SO 4 for 5 min. • RSM and ANN tools were utilized to model and optimize for bioethanol production. • ANN developed a good fit model compared to the RSM model. • Leftover biomass was characterized after the hydrolysis process completion. Bioethanol is a promising biofuel for replacing gasoline due to its sustainability. This work uses microwave irradiation and acid hydrolysis to produce bioethanol from Chlorella vulgaris. The hydrolysis procedure used 1%–3% sulfuric acid (H 2 SO 4). The maximum output of reducing sugar was 6.773 g/L after 5 min of irradiation. This study used RSM and ANN to optimize bioethanol production. The study predicted bioethanol yield using three factors: fermentation duration (12–36 h), temperature (28–32 °C), and inoculum concentration (0.5–1.5 g/L). The highest bioethanol yield was achieved using fermentation conditions of 36 h, 30 °C temperature, and 1.5 g/L inoculum concentration. The ANN model predicted the best ethanol output compared to the RSM model. The leftover biomass from biofuel synthesis was characterized for its potential for other energy production. The current study examined the feasibility of employing biomass in an environmentally sustainable manner to enhance the production of biofuels. [ABSTRACT FROM AUTHOR]