Research On Methane Production Process:Co-digestion Of Broussonetia Papyrifera Leaves And Organic Waste

With the development of animal husbandry,the contradiction between large-scale breeding and ecological protection is increasingly prominent.It is the key to solve the contradiction of develop the ecological planting.In this paper,Broussonetia papyrifera leaves were selected as the research object to study the feasibility of recycling the residue and other wastes in the breeding process of feed.Anaerobic digestion（AD）is the most effective way to convert these wastes into energy.Firstly,anaerobic digestion of nitrogen-rich and lignocellulose-like feedstocks:a case study on Broussonetia papyrifera.Secondly,according to the optimal conditions of batch experiment,the anaerobic fermentation characteristics of leaves were studied by continuous experiments.Finally,it was aimed to investigate the anaerobic co-digestion performance of Broussonetia papyrifera and organic wastes.The conclusions were as follows,firstly,this study aims to investigate the anaerobic digestion performance of Broussonetia papyrifera,a wide distributed nitrogen-rich and lignocellulosic-like plant,for methane production.The fermentation was conducted with the volatile solid（VS）concentration of 0.5%,1.0%,1.5%,2.0%and 4.0%under 37 and 55°C for30 days,respectively.Results suggested that the feedstock concentration at 2.0%and fermentation temperature at 55°C was optimal for the AD treatment of Broussonetia papyrifera.A maximal specific methane yield was achieved at 277.90±19 mL/gVS,which was 94.71%higher than that for the maximum specific methane under the thermophile condition because that the C/N was more suitable compared with other lignocellulosic biomass.Kinetic study suggested that the modified Gompertz equation was reliable（determination coefficients R² greater than 0.97）to describe the kinetic behavior of anaerobic digestion of Broussonetia papyrifera.In general,Broussonetia papyrifera was proved to be a suitabe feedstock for anaerobic digestion for methane production.Secondly,in batch fermentation under the condition of optimum temperature,it was studied to continuous anaerobic fermentation tests under the condition of 55°C and with the different organic load(0.5,1.0,1.5,2.0,and 4.0 gVSL^-1d^-1).The results show that different organic loads could stabilize gas production under the first two hydraulic residence times（0³0 d）,and each index was within the corresponding stable range.When the organic loads were 2.0 and 4.0 gVSL^-1d^-11 the system began to be unstable at the fourth（45⁶0 d）and the third（30⁴0 d）hydroresidence time periods,respectively.Thirdly,this study was aimed to investigate the anaerobic co-digestion performance ofBroussonetia papyrifera and wastes such as cow dung,domestic garbage and rice straw.The fermentation was conducted with mixing in different C/N under the volatile solid（VS）concentration at 2.0%.The results showed that co-fermentation fermentation（C/N=20）of Broussonetia papyrifera and domestic garbage had the best methane production（411.71mL/gVS）,which was 45.45%and 12.61%higher than that separate fermentation（283.06mL/gVS）of Broussonetia papyrifera and separate fermentation（365.61 mL/gVS）.of domestic garbage,respectively.The synergistic effect index showed that the index was6.58%,16.56%,15.40%,11.28%,18.69%,5.14%and 4.72%under anaerobic co-digestion performance of Broussonetia papyrifera and wastes such as cow dung（C/N=15,20）,domestic garbage（C/N=15,20）and rice straw（C/N=15,20,50）,respectively.The results showed that there was a synergistic effect in theco-fermentation of Broussonetia papyrifera and different wastes.Kinetic study suggested that the modified Gompertz equation was reliable（determination coefficients R² greater than 0.97）to describe the kinetic behavior of anaerobic digestion.