| The technology of straw field anaerobic fermentation can not only transform straw into clean energy,but also improve soil structure,kill pests and diseases.The ratio of carbon to nitrogen and inoculum are important factors affecting the fermentation process and the production of biomethane.In this study,rice straw was used as raw material to produce biomethane by simulating the conditions of field anaerobic fermentation with a self-made anaerobic fermentation device.The anaerobic development of rice straw under different treatments was studied by setting different carbon nitrogen ratios(15:1,20:1,25:1,30:1,control(53:1))and introducing different inoculums(biogas slurry,pig manure extract,biogas slurry + pig manure extract,control).The effects and mechanisms of C/N ratio and inoculum on biogas production by anaerobic fermentation of rice straw were revealed.The main conclusions of this study are as follows:(1)Adding urea to regulate the C/N of anaerobic fermentation system will affect the process of gas production,cumulative gas production,cumulative methane production and straw degradation.The time and size of peak value of physical and chemical parameters were different in different treatments.Adding urea to regulate C/N can improve the methane production efficiency of rice straw anaerobic fermentation and promote straw degradation,and the treatment of C/N 20:1 has the best promotion effect.The peak value of methane production of the treatment with C/N 25:1 was the earliest,5 days earlier than that of the control,but the peak value of methane production with C/N 20:1 was the highest,27.55% higher than that of the control;The cumulative gas production(4235.00 ± 41.93 m L)and methane production(1526.34 ± 12.54 m L)of 20:1 treatment were the highest,which were 30.78% and 51.31% higher than those of the control group,respectively;the effect of 20:1 treatment on straw degradation was the best,and the total degradation rate,cellulose degradation rate and hemicellulose degradation rate were 51.33%,55.31% and 53.05% respectively.(2)The time and size of the peak value of physical and chemical parameters were different in different treatments.Adding inoculum can improve the methane production efficiency of rice straw anaerobic fermentation and promote the degradation of rice straw.The peak value of methane production increased by 192.75% compared with the control,and the stagnation period shortened by 10 days;the cumulative gas production(4458.33 ± 99.85 m L)and the cumulative methane production(2014.67 ± 18.92 m L)was the highest,70.82% and 122.93% higher than that of the control group;the total degradation rate,cellulose degradation rate and hemicellulose degradation rate reached 54.71%,42.20% and 42.70% respectively,80.56%,96.64% and 42.14% higher than that of the control group.(3)The addition of inoculum can significantly improve the abundance and diversity of bacteria and archaea in the early and middle stages of each treatment.There was no significant difference in the level of phylum among the treatments.Bacteroides,Proteobacteria,Firmicutes and Syntrophites were the dominant groups of bacteria.At the level of genus,the species of bacteria in each treatment were more abundant,and the species and relative abundance of dominant genera were quite different;Archaea in each treatment were at the level of phylum There was no significant difference on the genus level,but there was a significant difference on the genus level.In the control group,the dominant bacteria were Methanosarcina in the first half,Methanobacteria and Methaspirillum in the later half,and H2/CO2 methanogenic bacteria were the dominant bacteria in each period. |
