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Research paper : Bioethanol production from woods with the aid of nanotechnology (T. Endo)−279−Synthesiology - English edition Vol.2 No.4 (2010) that since the wet cutter mill and the disk mill used in this R&D are precision mills, they cannot be readily upsized. However, since our pretreatment process is similar to the mechanical pulping technology of papermaking, we believe up-scaling and practical utilization can be done by applying and developing the papermaking technology.8 Summary and future developmentsAt AIST, we built an integrated manufacturing mini-plant (capable of treating 200 kg of diverse biomass at once) that incorporates our pretreatment process and the saccharification and fermentation processes. Here, extraction of issues in individual elemental technologies and process continuity, issues on biomass species, and economical feasibility assessments are being done. Currently, R&Ds are conducted with companies for commercialization using large-scale processes, and papermaking technologies are being incorporated.In the practical application of bioethanol production technology, high added value for residues and byproducts is also important. The microfibrilized product obtained by the pretreatment of wood is called cellulose nanofiber since it is a nanosize fine fiber. Compared to steel of the same size, its weight is 1/5 lighter and the strength is 5 times greater. Currently, the development of lightweight high-strength material using this property is being developed[15]. Also, application to optical materials and cosmetics is being studied. Some are already in use as filter materials and food additives. In our pretreatment process, no major change in the molecular structure of the wood components occurs. Therefore, the lignin residue after the enzymatic saccharification is unlike the black liquor (broken down lignin) produced as waste in the papermaking process. It is thought to contain structures similar to wood with high molecular weight. This lignin residue can be converted to polymer material and high value-added material that was impossible with lignin in the black liquor that could only be used as fuel. Extremely high economic feasibility can be attained using the cellulose nanofiber production as a common fundamental process with the production of bioethanol (main) and high value-added material (subsidiary).Figure 11 is a summary of the flow of our pretreatment technology development. As a result of studying the conventional technology, we found that the viewpoints from the wood chemistry and cellulose chemistry of the target wood were necessary for the development of the practical pretreatment technology. Moreover, by combining the knowledge and technologies of other fields such as macromolecular chemistry and papermaking, we were able to construct a pretreatment technology based on a new concept. However, there are many unclear points about the properties and reaction mechanism of the enzymes for the cellulose nanofiber obtained by pretreatment, and state-of-the-art analyses are necessary. In the future, the technologies and knowledge of biotechnology, chemical engineering, thermal engineering, LCA assessment, and social sciences may be fused to establish a practical biofuel technology.Fig. 11 Flow of pretreatment technology development.Construction of efficient and effective pretreatment method by combination treatment (wet cutter mill + autoclave + disk mill)Advancement of pretreatmentWhen fibrils (in order of nm) were actually separated by wet mechanochemical treatment, high saccharification was obtained even with high crystallizationDemonstration of hypothesisPractical use (construction of economically feasible bioethanol production process including advanced utilization of byproducts)Development of large-scale process utilizing papermaking technologyFuture developmentEfficient pretreatment by disk mill (stone mortar)Practical pretreatment methodSeparation of fibril is important (hypothesis)Important factors for enzymatic saccharificationApply techniques of macromolecular chemistry (relaxation time measurement by solid NMR)Use of technologies from other fieldsFine pulverization (in order of µm), amorphization of cellulose, and removal of lignin that have been speculated were not important factorsFactors that improve enzymatic saccharificationMilling treatment (mechanochemical treatment) is retested using ball millRe-investigation of classic pretreatmentConventional technologies are insufficient in terms of wood chemistry and cellulose chemistrySurvey of conventional technologyPractical pretreatment technology is mandatory to produce bioethanol from wood

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