Authors: Aditya Choukiker, Om Prakash Sondhiya
Abstract: Bioethanol remains one of the most important renewable liquid fuels because it can be blended with gasoline, distributed through existing fuel systems, and produced from a broad range of biological feedstocks. While first-generation ethanol relies on sugar- and starch-rich crops, increasing interest has shifted toward agricultural residues such as groundnut shell, sugarcane bagasse, rice straw, and corn stover. These residues are attractive because they are abundant, inexpensive, and do not directly compete with food use. Their conversion is nevertheless technically demanding because lignocellulosic materials contain cellulose and hemicellulose embedded within a lignin-rich matrix that resists hydrolysis. This paper presents a research-style review of residue-based bioethanol production with emphasis on feedstock structure, pretreatment methods, hydrolysis and fermentation pathways, product recovery, and practical engineering challenges. Groundnut shell is examined as a representative residue because it is readily available in many agrarian regions yet comparatively underused as an energy resource. The paper synthesizes published engineering and bioenergy literature into a coherent overview, compares selected residues on the basis of composition and process suitability, and discusses major barriers including pretreatment severity, enzyme cost, inhibitor formation, feedstock variability, and scale-up complexity. The review concludes that residue- derived bioethanol is technically feasible and environmentally relevant, but successful deployment depends on better feedstock logistics, process integration, and biorefinery strategies that improve carbon efficiency and reduce conversion cost.
