Sustainable Pretreatment of Food Waste for Enhanced Bioethanol Production and Improved Waste Management: A Review.

Rapidly increasing global food-waste generation poses major environmental, economic, and waste-management challenges due to its high organic load and improper disposal practices. Addressing this problem requires sustainable valorization strategies, including bioethanol production, which can simultaneously reduce waste burdens and contribute to renewable-energy generation. This review synthesizes current knowledge on the physical and chemical characteristics of food waste, the rationale behind pretreatment methods, and their role in improving downstream bioconversion efficiency. Pretreatments-physical, chemical, physicochemical, and biological-are examined with emphasis on how they enhance hydrolysis and improve fermentable-sugar release. Fermentation is the critical biochemical step in this pathway, as it converts the hydrolyzed sugars into bioethanol through the metabolic activity of yeast and bacteria. Enzymatic hydrolysis and microbial fermentation, the core steps that convert complex biomass into ethanol, are critically evaluated alongside bioprocessing strategies such as SHF, SSF, SSCF, and consolidated bioprocessing. The review identifies that physical and chemical pretreatments improve fermentable-sugar release but may involve higher energy or chemical inputs, whereas enzymatic and biological methods offer more sustainable alternatives with lower inhibitory by-product formation. Among bioprocessing strategies, SSF and SSCF consistently demonstrate higher bioethanol yields and reduced processing time compared with SHF. Consolidated bioprocessing shows strong potential for future development due to its reduced operational steps and lower overall costs. Collectively, these findings highlight the importance of integrating efficient pretreatment with optimized fermentation strategies to maximize bioethanol production while enhancing the sustainability of food-waste management.