Recent Progress in Bioethanol Production from Renewable Biomass and Waste: A Critical Review of Technologies and Challenges

Abstract

The need for climate change mitigation coupled with the necessity of decarbonizing the transport sector has led to an increasing interest in seeking bioethanol as an alternate and sustainable transport fuel. Transport generates approximately one-quarter of the global energy-related CO2 emissions; hence, a low-carbon transport fuel that is compatible with existing infrastructures is needed. Although the role of first-generation bioethanol produced from food crops is significant in the global bioethanol pool, with some sustainability concerns raised about the future potential of this pool of bioethanol, the interest is now focused on newer sources like agricultural residues, food waste, forestry by-products, and industrial wastes. This article critically reviews recent advances in the conversion of these materials into bioethanol between 2020 and 2025, particularly with regard to the importance of properties of these materials on pretreatment, hydrolysis, fermentation, and separation. Unlike prior reviews, this article focuses more on scales, efficiency, and techno-economic analysis rather than just maximizing yield from lab-scale studies. Despite advances made, such as novel pretreatment methods and genetically engineered microbes for the conversion of mixed sugars, several challenges prevent the commercialization of bioethanol produced from wastes, with the main being enzyme costs, complexities of integration, and energy-intensive downstream separation.