Abstract:Anaerobic digestion is a promising technology by which crop straw can be biologically transformed into biogas. However, the efficiency of anaerobic digestion was significantly influenced by the complicated structural resistance from lignocellulose. Therefore, aerobic digestion was used to break down the structure of lignocellulose before anaerobic digestion process. The TRIZ theory was applied to design aerobic-anaerobic combined digestion process of rice straw, and the effects of different aeration modes and addition of fungicides on the fermentation characteristics were studied. The results showed that after aerobic digestion process, the degradation rate of lignocelluloses in each group was increased to some extent. The degradation rate of lignocellulose was the highest in the aerated group added mixed bacteria, and the degradation rates of hemicellulose, cellulose and lignin were 46.3%, 40.4% and 8.2%, respectively. The modified Gompertz equation and the first-order equation could well fit the cumulative methane production, with R2 greater than 0.97. The cumulative methane yield of the aerated group added mixed bacteria in the experiment was 294.38mL/g, which were 279.58mL/g and 320.11mL/g fitted by two equations, respectively. The calculated methane yield was 424.7mL/g calculated by the Baswell formula. The test value was about 69% of the theoretical methane yield which was higher to predict methane yield for inert substances such as rice straw. The total VS degradation rates of aerobic exposure group, aerated group added Trichoderma, aerated group added Aspergillus niger, aerated group added mixed bacteria of Trichoderma and Aspergillus niger and mixed group added mixed bacteria of Trichoderma and Aspergillus niger were 15.99%, 35.47%, 37.99%, 54.68% and 40.92% higher than that of direct anaerobic fermentation group, respectively. The effect of aeration was better than that of mixing for oxygen supply. The effect of adding mixed bacteria in aeration process was better than that of adding single bacteria.
