ABSTRACT
The crude oil-based gasoline fuels have been widely used in the transportation sector since the 1920s. However, there have been great public concerns over the adverse environmental and human impact of these fuels. Hence, biomass-based bioethanol fuels have increasingly been used in blending gasoline fuels, in the fuel cells, and in the biochemical and biohydrogen fuel production in a biorefinery context. However, it is necessary to pretreat the biomass to enhance the yield of the bioethanol prior to the bioethanol production through the hydrolysis of the biomass and fermentation of the resulting hydrolysates. The research in the fields of biological, chemical, and, to a lesser extent, mechanical and hydrothermal pretreatments of the biomass has thus intensified in recent years. The most prolific pretreatments have been enzymatic hydrolysis, enzymatic pretreatments, ionic liquid pretreatments, fungal pretreatments, and, to a lesser extent, acid pretreatments and alkali pretreatments at the microscale. Further, the most used groups of the biomass have been biomass constituents and, to a lesser extent, wood, agricultural residues, and grass while the most used individual biomass and biomass constituents have been cellulose, lignin, wood, and, to a lesser extent, corn stover, softwood, switchgrass, wheat straw, and lignocellulosic biomass. However, it is essential to develop efficient incentive structures for the primary stakeholders to enhance the research in this field. Although there have been a number of review papers on the biomass pretreatments, there has been no review of the most- cited 25 articles in this field. Thus, this book chapter presents a review of the most-cited 25 articles in the field of the biomass pretreatments. Then, it discusses the key findings of these highly influential papers and comments on the future research priorities in this field.
