Pretreatment Of Cotton Stalks And Microbial Community Diversity In Biogas Fermentation System

China is a major cotton-producing country, and has abundant resources of cotton stalks. Biogas fermentation of cotton stalks is one of the effective ways to use these resources. Since cotton stalks are a kind of hard stalk with high lignified degree and abundant phloem fibre, it is difficult to degrade cotton stalks in the process of biogas fermentation, which affects the efficiency of gas production. In order to improve the efficiency of biogas fermentation of cotton stalks, it is necessary to pretreat cotton stalks, and to screen and domesticate high active inocula for biogas fermentation. Therefore, the biological pretreatment methods of cotton stalks and screening and domestication of inocula had been studied in this paper. The influences of different pretreatment methods and different inocula on biogas fermentation of cotton stalks were studied. Since microbial community plays a key role in biogas fermentation, the diversity of microbial community structure after pretreatment of cotton stalks and that during the subsequent biogas fermentation process was analyzed. The major results obtained in this paper were as follows.(1) A composite microbial system MEG with high efficient and stable degradation of cotton stalks was screened through the method of multigeneration selection. This microbial system was inoculated to the cotton stalks with 12% of inoculation amount, and then stationarily treated for 7 days. Afterwards, biogas fermentation was conducted. Compared to the condition of non-pretreatment, the gas production increased by 25%. DGGE analysis showed that the diversity of bacterial community structure in the biogas fermentation system of cotton stalks was more abundant compared to the condition of non-pretreatment.(2) Inocula domesticated from the mixture of five kinds of activated sludge from river bed mud, sewage ditch, industrial wastewater bed, pond bed, and lake bed could be acted as effective inocula for biogas fermentation of cotton stalks. Compared to the inocula domesticated from one kind of activated sludge, the daily gas production and cumulative gas production were higher.(3) DGGE analysis indicated that the structural diversity of bacterial communities varied with fermentation period, and closely related to the biogas production and substrate degradation.