Synergistic Effect On Methane Production Of Anaerobic Digestion With Mixed Materials

Anaerobic digestion of biogas production is an important way to realize the effective utilization of agricultural waste and to solve the problem of environmental pollution and energy crisis.Scaled biogas engineering requires a stable feedstock supply and high efficiency and stable biogas production,but anaerobic digestion of single substrates has the problems of nutrition imbalance and the supply capacity is difficult to meet the needs of the development of large biogas project.Synergistic anaerobic digestion with mixed materials is an effective methods to achieve the nutrition balance of substrate,and improve the performance of methane production.In order to evaluate the mixed material synergistic effects on methane production performance of anaerobic digestion,in this paper,tests were conducted under the condition of solid-state(12%total solids)and mesophilic(37±1)?,the experiment study the different proportions of cow manure and tomato stems and leaves anaerobic co-digestion process,different proportions of cow manure,vegetable waste and corn straw anaerobic co-digestion process,analyses the influence of mixing rations on methane production performance and system stability,determines optimum mixing ratios and synergetic effects of co-sunstrates,and the modified Gompertz equation was used to analyzed the dynamic characteristics of producing methane process.The main achievements of this paper are as follows:(1)The proportion of co-substrates can significantly affect the methane production rate and system stability during anaerobic digestion.When the amount of cow manure in the substrate proportion was high,improved system buffer capacity,the methane production rate increased rapidly;when the amount of tomato stem and leaf was high,the rate of methane production was significantly reduced due to insufficient system buffer capacity,and the peak of methane production was delayed.The highest methane yield and highest cumulative methane were achieved when the cow manure and leaves mixed ration was 3:1,were 224.23m L/g VS and 14352m L respectively.The cow manure and tomato stems synergistic effect of anaerobic co-digestion ranged from-9.97%~34.19%,the mixing ratio of 1:3,the process of methane production showed antagonistic effect,and methane production decreased by 9.97%.The modified Gompertz model had feasibility to describe the cow manure and tomato stems methane production process of anaerobic co-digestion,the fitting coefficient R~2 was between 0.9855~0.9989.When the ration of cow manure and tomato stems and leaves was 3:1,the minimum delay time?was 4.51d,and the maximum methane production rate R_m reached a maximum of 9.26 m L/(d·g).(2)A certain proportion methane production performance of cow manure,vegetable waste and corn straw co-digestion was better than from mono-substrate and two kind of feedstocks co-digestion.The three kinds of materials balanced the nutrients and promoted the process of methane produce process,the anaerobic co-digestion performance index was between 1.33~1.92,improved the methane production capacity significantly(P<0.05).When the VS mixed ratio of cow manure,vegetable waste and corn straw was1:0.4:0.6,exhibited the most methane production performance,and obtained the highest cumulative methane of 20 470m L,which was47.83%?180.03%and 67.79%higher than cow manure,vegetable waste and corn straw only group respectively;increased by 12.81%compared of the VS ration of1:1 for co-digestion of cow manure with corn straw.The synergistic effect of three kinds of co-feedstocks improved the biodegradability of raw materials and promoted the conversion of organic matter into methane.A 1:0.4:0.6 VS ratio of cow manure,vegetable waste and corn straw produced the highest removal rate of VS and methane yield,were 65.63%and 286.0m L/g VS respectively,which improved26.11%?23.97%and 42.62%compared to the cow manure,vegetable waste and corn straw only group VS removal rate,respectively.(3)The analysis results of modified Gompertz equation indicated that the model had feasibility to describe the methane production process of anaerobic digestion,the R~2 values of the fitting curves ranged from 0.9838~0.9976.Co-digestion of these substrates improved biochemical methane potential.Cow manure,vegetable waste and corn straw mono-digestion maximum methane production rate R_m were 11.32,7.20 and 7.71m L/(d·g)respectively;the cow manure and corn straw VS ratio of 1:1reached R_m was 14.52 m L/(d·g),which was increased by 28.27%compared of the mono-digestion of manure;for the three kinds of feedstocks co-digestion,cow manure,vegetable waste and corn straw VS ratio of 1:0.4:0.6 has a maximum methane production rate of 17.29m L/(d·g),which was improved 52.74%and 19.08%compared of the mono-digestion of manure,VS ratio of 1:1 for cow manure and corn straw.The noverty of this paper are listed as follows:The synergistic effect of mixed materials on anaerobic co-digestion of methane production and organic substance degradation efficiency was revealed,and the best mixing ratio of raw materials was obtained.