| A large amount of com stovers are in idle or burned every year, anaerobic digestion of com stovers to produce biogas is a environment-ecology-resource technique. Com stover is a kind of lignocellulose biomass, its special structure of lignocellulose caused a low efficiency of hydrolytic phase during anaerobic digestion, which will affect the efficiency of subsequent methane-producing reaction. This paper focuses on improving anaerobic digestion efficiency of com stovers to produce biogas. With com stovers as raw materials, a novel bionic anaerobic digestion reactor was designed, simulating rumen ruminants efficient digestion principle of lignocellulose biomass, and anaerobic digestion of com stovers was carried out. The characteristics of biogas yields, solid phase, liquid phase and spectroscopy were analysised, to investigate the feasibility of bionic reactor, stability and efficiency of biogas production. Besides, the influence of pH condition on biogas production of com stover anaerobic digestion was discussed. The main conclusions of this study are as follows:The bionic reactor based on ruminant digestion mechanism can effectively improve the liquefaction efficiency of com stovers. Organic matters in com stovers from upper part of the reactor were released into the liquid phase, and the liquid was transferred to the lower part of the reactor through a sieve. The solid content in corn stover in upper part gradually reduced, while organic matters in the liquid phase (lower part of the reactor) effectively increased. In this study,1/3of the liquid in lower part was took and then refluxed to the upper part. The total liquid producion was76.39mL/gVS. The highest VFA concentration in the upper and lower part was31.2g/L and15.75g/L, respectively. The ratio of SCOD and TCOD in the lower part of bionic reactor maintained above90%. The TSS reduction and VSS reduction in solid-phase of upper part showed good linear relationship, and VSS reduction/TSS reduction was up to89.68%, which demonstrated that the organic matters in bionic reactor were well liquefied. With this bionic reactor, the highest biogas production rate was21.6ml/gVS-d, and the cumulative biogas production was256.52mL/gVS, showing that the high liquefaction efficiency of com stovers in bionic reactor significantly impoved the subsequent methane-producing activity.The analysis of organic matters composition and structure in solid and liquid phase was carried out with EEM fluorescence spectrum and FT1R spectroscopy during the anaerobic digestion process. Resultes showed that two fluorescence absorption peaks at Ex/Em:420/495nm and Ex/Em:430/514nm appeared in the early stage of anaerobic digestion, which were attributed to coenzyme F42o and riboflavin; two main fluorescence absorption peaks of protein and coenzyme NADH at Ex/Em:280/356-361nm and Ex/Em:340/425-440nm appeared in later anaerobic digestion, but the fluorescence intensity of both peaks was low. FTIR spectra showed that the absorption peak intensity in upper part of bionic reactor was significantly greater than that in the lower part, and the organic components were mainly related to lipid cellulose, carbohydrates and other materials.Weak alkaline environment of anaerobic digestion is helpful to improve the efficiency of methane production from corn stovers. Different pH conditions showed significant effects on pH, alkalinity, VFA and SCOD of the anaerobic digestion system. The system with a pH of9showed the fastest biogas production rate, and the cumulative biogas production was134.33mL/gVS, which was3.23and6.71times of that with a pH5and11, respectively. The order of different pH conditions for cumulative biogas production was as follows:pH=7> pH=9> pH=5> pH=11. The cumulative biogas production for the system with a pH of7was1.11,3.23and6.71times of that with a pH of9,5and11, respectively.The organic matters composition and structure of liquid were analyzed with EEM fluorescence spectrum and ultraviolet (UV) spectrum in the anaerobic digestion system. EEM fluorescence spectra showed that pH can not only affect organic matter types, but also the intensity of fluorescence peak. UV spectra showed that an absorption peak appeared near280nm and this component was related to lignin. |
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