Breaking the obstacle of carbohydrate to direct transformation of bioethanol fermentation residues for production of high-quality resins
Direct transformation of bioethanol fermentation residues to valuable products is a challenge for current bioethanol fermentation process. Traditionally, adding of carbohydrate will reduce the performance of lignin-based resin, which seriously limited the utilization of the fermentation residues (lignin-rich component) into resin. In this study, we succeeded in our efforts to overcome this challenge by the simple and novel strategy to produce high-quality co-condensed fermentation residue-based resins (FRs) over inexpensive sodium hydroxide and sodium carbonate as catalysts. Herein, the physical properties, chemical structures, and curing behavior of the prepared resins obtained from two different types of fermentation residues were thoroughly characterized. It is the first to meticulously investigate the synergistic effect of lignin and carbohydrates on resins. The mechanism results indicated that the numerous co-condensed linkages were formed to produce resins with a firm structure. More importantly, the carbohydrate-rich solid residues could substitute wheat flour to adjust viscosity, prevent excessive osmosis, and improve the bonding strength of the FRs. Under the synergistic effect, the produced green FRs can be utilized to manufacture plywood with a satisfactory bonding strength (1.07 MPa). The emission of formaldehyde, a harmful volatile organic compound, could also be reduced by 94%. This work develops a promising sustainable technology with no waste production for direct transformation of bioethanol fermentation residues in bioethanol manufacturing. The technique reported here vastly broadens the application of fermentation waste and advances the road of the bioethanol industry.