A Research On The Key Technologies In The Cleaner Production Of Ethanol And Methane Production From Switchgrass Pretreated By Subcritical Water

Currently, with the rapid development of Chinese industrialization process, the total amount of waste water is increasing.However, the lack of water has become a serious crisis in our country. Under the trend of advocating energy conservation, the treatment of waste water has increasingly become the focus of the society. To achieve the sustainable development, the raw materials, production processes, comprehensive utilization and environmental protection must be considered as a whole. With cleaner production appearing, theadvancing concept and technological innovation will be annecessary way to achieve the sustainable development. In this paper, the subcritical water was employed to pretreat switchgrass. The water-soluble portion and insoluble portion of the switchgrass were conducted by methane fermentation and ethanol fermentation, respectively.Then the supernatant was reused after methane fermentation in the subcritical water pretreatment process. The wastewater was recycled. The main contents and results were as follows:1. Under optimal conditions of the subcritical water, the residue of twenty cycles the results of SEM was analyzed. Optimal pretreatment conditions was: 203 ℃, 0 min. The residue yield of switchgrass has been about 60% stably. The content of hemicellulose decreased. The content of cellulose was stably at 30% to 35%. The content of lignin reduced. The result of SEM showed that switchgrass was from raw materials to being pretreamented, being digested, after being fermented. The surface was smooth and neat, became rough, then disorganized, and finally debris, we can see that the microstructure of switchgrass is destroyed step by step.2. Under optimal conditions of the subcritical water,the liquid pretreated of twenty cycles fermented. With the cycles carrying on, the volume of methane reduced, and finally stabilized. The volume of the methane maintained at 300 mL, while the pH is lower and lower.3. The composition of monosaccharide of water-soluble fraction was analyzed. The reduced sugar of cycle tenth, eleventh, twelfth were 1179, 783, 1432, 931 mg /1000 mL. The methane of methane fermentation were 378,255,231,256 mL. Reduced sugar were mainly xylose and glucose after subcritical processing. After methane fermentation there were no sugar or less sugar in the liquid.4. Under the optimal conditions of subcritical water. The ethanol fermentation was optimized. The samples were processed at different times of sonication and soaking in ethanol, the concentration of ethanol up to 4.3% after fermentation. The concentration of ethanol of the ethanol fermentation between the twenty cycles was from 3.18% to 1.66%. The concentration of glucose is about 4 mg / mL in the enzymolysis of 24 h. A small amount of glucose is not utilized after 96 h. At 24 h the yeast was inoculated into the fermentation broth, the yeast colonies is 1.3 × 10~6-1.7 × 10~6.