Fuel-Grade Bioethanol Production: Process Strategies, Laboratory Evaluation, and Global Review

Fuel-grade bioethanol has gained global significance as a renewable and sustainable alternative to fossil-derived petrol, owing to its potential to reduce greenhouse gas emissions, enhance energy security, and support climate action goals. This review presents a comprehensive analysis of bioethanol production process strategies with a focus on achieving fuel-grade ethanol quality, alongside a global perspective on major producing regions. Key stages of bioethanol production are examined, including feedstock selection, fermentation processes—commonly employing Saccharomyces cerevisiae—and downstream purification strategies such as multi-stage and fractional distillation. Special emphasis is placed on sugarcane-based bioethanol production, which dominates in countries like Brazil and India, while corn-based ethanol systems prevalent in the United States are also discussed. Process optimization approaches reported in laboratory- and industrial-scale studies demonstrate that extended fermentation and advanced distillation techniques significantly enhance ethanol recovery and purity. Analytical methods such as gas chromatography are widely utilized to assess ethanol quality, with near-azeotropic purities (~95–97%) being essential for ensuring blend stability, engine compatibility, and prevention of phase separation in ethanol–petrol blends. Overall, this review provides a clear understanding of fermentation- and distillation-based bioethanol production and its global relevance, supporting the role of bioethanol as a sustainable fuel option in current and future energy systems.