| Dry anaerobic digestion technology handles wastes with Total solid (TS) between20%and40%. The process seemed much easier to handle with than wet anaerobic and the water was not necessarily added to the solid wastes. It has attracted much attention from researchers, therefore the decomposer were directly applied to farmland in the rural area. Recently, the study of anaerobic fermentation technology major in material pretreatment, influencing factors, vaccination agent selection and deployment, gas production and the process conditions. It was rarely reported of the transformation mechanwasm of organic matter and dynamic succession law of microbial during the dry anaerobic fermentation system.The aim of this paper was to study the system of dry anaerobic digestion with corn stover. And to analyze the structure of corn stover particle, degradation of hemicellulose, cellulose and lignin (LHC), relationship between TS of substrate and production of organic acid, analysis of law of microbial dynamic succession, the study was explored the transformation mechanism of organic matter and microbial succession law in the process of corn stover during dry anaerobic fermentation. The principal contents and result are as follows:(1) Dry anaerobic digestion technology treat Corn corn stover with different TSWe were carried out the experiment of dry anerobic digestion of corn stove, and take the concentration of TS was20%,25%,30%,35%and40%respectively. The results showed that dry anaerobic fermentation system of each corn stover treatment can start successfully and operate steadily when the concentration of TS was20%-35%. And the gas production maximum and best reduction effectiveness of dry anaerobic fermentation system of corn stover was under the TS concentration of30%. The reduction quantity of TS and VS were43.3%and43.8%respectively under the TS concentration of30%. The volume decreased by48.3%. The biogas production was194.4m3/t·VS and the content of methane was64.2%and52.2%respectively.(2)(2) Analysis of matrix particle microstructureBy the means of Environmental Scanning Electron Microscopy (ESEM), X ray diffraction (XRD) and Frustrated Total Internal Reflection (FTIR), we analyze the surface morphology of the substrate particles, the degree of crystallization and the dynamic changes of molecular surface groups during dry fermentation process. The results show that the destruction of surface morphology of matrix particles are related to the fermentation time and the TS concentration. It was gradually destroyed with the extension of time. the fracture of surface morphology was obvious and occurrence time was short when the TS was20%or25%. Just the groove holes are formed on the surface after dry fermentation when the TS content was30-35%. The surface morphology of the particles was not significantly changed when the TS content was up to40%. The matrix crystallinity and crystallite size of the particles have a dynamic change of fall-rise-decline, and the relativity between the TS concentration and the crystallinity of the particles was-0.088at the beginning and rised to0.698at the end. The infrared characteristic peaks were mainly at872cm-1、1000-1030cm-1、2920cm-1and3100-3680cm-1and the changing trend was different obviously during fermentation process.(3) LHC groups dynamic of in the particlesThe study wasanalyzed the transformation difference of different groups/bond type of cellulose, hemicelluloses and lignin in stalks during the dry fermentation process with FTIR. The results showed that the degradation ratio of cellulose, hemicellulose and lignin was low. They are refractory organic compounds. But the degradation ratio of cellulose can reach40.5%, which was significantly higher than the19.1%of hemicellulose and17.0%of lignin. The relative intensity changes of characteristic peaks of β-glucoside bond, C-H, O-H and CH2-CH2in cellulose differ significantly, and CH2-CH2was the most difficult to degrade in all treatments. The degradation ratio of the strength of the characteristic peak of C=O in hemicellulose xylan and other types was not significantly different during the fermentation process, but there was obvious difference in degradation trend during fermentation process. The degradation rate of C=O in xylan was lower than other types of C=O within the matrix when the TS was less than35%. The degradation rate of C=O in xylan was higher than other types of C=O when the total solid was40%. The variation tendency of benzene ring, C-H, C-O-H, O-H, C-C, C-O-C and C=O in lignin was not the same during dry fermentation process. The benzene ring was the group which was most difficult to degrade in lignin, and the C-O-C, C=O and C-C are easily degraded groups.(4) Producted mechanism of organic acid in dry anaerobic digestionThrough the study of production rules of volatile fatty acid (VFAs) and the screening of characteristic organic acid in the dry fermentation system and combined with the analysis of the correlation between organic acid content and fermentation substrate TS concentration, the results showed that although the content of VFAs experienced increasing, stability and decline, but the content of VFAs returned to the initial stage content at the end of fermentation. At the same time, the content of VFAs in the fermentation system was not affected by the TS concentration. The general content was about127mg/L. VFAs is mainly composed of acetic acid, propionic acid, butyric acid, valeric acid and caproic acid. The content of organic acid in different treatment were basically stable in the fermentation process. The acetic acid was the advantage organic acid (36.3～41.7%) and the content of the propionic acid was the lowest (5.9～8.0%).The content of acetic acid was among46.6～68.5g/L during the dry fermentation process. Combined with the correlation analysis between acetic acid and methane production, we regard the content of acetic acid at48.0-54.6g/L as the best methane production concentration. Concentration of acetic acid at46.6-47.2g/L and55.0-60.0g/L suppressed the production of methane.(5) Study on the law of dynamic succession of microorganismWe detected the microorganism during the dry fermentation process with the PCR-DGGE. We analyzed the succession trend of microorganism, microbial diversity and the similarity of community structure during the fermentation process, and sequence the dominant microorganisms. The results showed that of all total solid concentration in the dry fermentation system, DGGE spectra showed that the total number, species and brightness of microorganisms stripbands has greatly changed. The microorganisms similarity of bacteria, actinomycetes and fungi at the end to the initial stage were46.9%,59.9%and48.7%. The maximum variation mainly occurred in the first5days of the fermentation process, and the similarity of bacteria, actinomycetes and fungi decreased by39.4%,27%and34.5%respectively. |
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