Pretreatment of wheat straw using ionic liquids for bioethanol production: A review

Abstract

Ethanol production from sustainable and inexpensive farming residues decreases greenhouse gas emissions, for instance, carbon dioxide, nitrogen dioxide, sulfur oxide, and eliminate smog from the atmosphere. A certain number of agricultural residues and plentifully misused materials are oat straw, rice straw, and wheat straw; waste potato, switchgrass, corn steep liquor, sweet sorghum, bagasse, sugar beet tubers, etc. are used as potential material for bioethanol making in different countries. Wheat straw deposits are one among the residues produced in substantial amounts globally, including Ethiopia. However, the elimination of lignin out of lignocelluloses untreated residues is the most critical step. Various pretreatment methods are explained before by numerous researchers with chemical, physical, biological, and ionic liquid pretreatment. This review carefully evaluates the performance of highly capable and recent techniques of hydrolysis and discusses the potential of wheat straw residue for bioethanol production, using less energy-demanding and more eco-friendlier techniques than the recent commercial pretreatment techniques. The most popular of these is the ionic liquids (ILs). Important pretreatment steps by ionic liquids, such as 1-allyl-3-methylimidazolium chloride,1-ethyl-3-methylimidazolium acetate, 1-butyl-3methylimiazolium,1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium diethyl phosphate, 1-methyl-3-(4-sulfobutyl) imidazolium bisulfate, and cholinium taurate, will be evaluated. Additionally, critical parameters affecting the treatment process, such as temperature, the ratio of ionic liquids to residue dose, concentration of ionic liquids, and time taken, would also be discussed.