Study On The Anaerobic Digestion Process Of Mixed Tail Vegetables And Cow Dung

Energy shortage has become an important problem facing the world today.Developing and utilizing renewable energy is one of the important ways to solve the problem of fossil fuel depletion.As one of the agricultural waste,vegetable wastes are good substrate for the production of biogas by anaerobic digestion.This research by vegetable wastes as the main object of fermentation,using laboratory batch fermentation experiments,based on the analysis of its individual based on the results of the fermentation,using pretreatment method for improvement of the vegetable wastes of methane production rate,and then through high-throughput sequencing microbial analysis before and after the pretreatment,to explore different blending ratio on the vegetable wastes and cow dung mixed anaerobic digestion to produce the effects of the biogas on the basis of single factor,in the process of fermentation parameters were optimized by response surface to find the vegetable wastes mixed fermentation food efficiently the process of producing biogas,while increasing the vegetable wastes anaerobic digestion process stability,to solve the problem of vegetable wastes pollution to provide the theory and practice basis.The main results are as follows:(1)Different pretreatments can all improve the methanogenic capacity of the reaction system.The order to promote the generation of methane was ultrasonic crushing > ultrasonic cleaning > lye soaking > biogas slurry and the optimal pretreatment parameter for ultrasonic crushing was ultrasonic power 30%(rated power 450 W).(2)Through to the cabbage and celery pretreatment microbial bacteria microbial analysis found that the processing of cabbage and celery,cabbage and celery in the control group of microorganisms had obvious changes,prior treatment group of microbes and bacteria liquid contains microbes were similar,main advantage bacterium were Weissella,Clostridium sensu stricto,Sedimentibacter,Proteiniphilum and Petrimonas bacteria.(3)When the mixing ratio of cow manure and cabbage was 2:1,the methane production rate was 52.7% higher than that of cabbage anaerobic digestion alone.When the mixing ratio of cow manure and celery was 3:1,the methane yield increased by 52.0% compared with the anaerobic digestion of celery alone.(4)On the basis of single factor experiment,the response surface method was used tooptimize the parameter conditions in the fermentation process.Taking methane production rate as the response value,three factors,namely fermentation temperature,solid-liquid concentration and stirring interval,were selected to study their effects on the biogas rate in the fermentation process.The order of influence of cabbage and celery on methane yield was as follows: liquid concentration(x2)> fermentation temperature(x1)> stirring interval(x3)and fermentation temperature(x1)> liquid concentration(x2)> stirring interval(x3).The optimal parameters for cabbage and celery were: fermentation temperature 37.2?,material and liquid concentration3.1%,and stirring interval 25.6 h/ time.The fermentation temperature was 38.7?,the material and liquid concentration was 2.7%,and the stirring interval was 26.8 h/time.Through the analysis of the potential of biogas production by anaerobic digestion of different vegetable waste,it was found that there are some differences in the potential of gas production by anaerobic digestion of different vegetable wastes.Cabbage and celery with large differences were selected as vegetable wastes for experimental research.Through pretreatment,the acidification process of anaerobic digestion of vegetable waste can be delayed and the gas production rate of vegetable waste can be improved.Through the microbial analysis before and after pretreatment,the dominant bacteria produced a large number of volatile fatty acids such as acetic acid,which prolonged the acidification period,promoted the anaerobic digestion process,and thus improved the methane production rate.Mixed anaerobic digestion by adding cow manure and vegetable waste may improve the living environment of microorganisms,increase the species and quantity of microorganisms in the system,improve the buffering capacity of the system,avoid acidification phenomenon when fermentation alone,enhance the stability of the fermentation system,and improve the anaerobic digestion efficiency.Through the study of the fermentation of cabbage and celery parameter optimization,get the best vegetable waste and cow dung mixed anaerobic digestion process,cabbage after the optimization process was: the ultrasonic broken power of 30% for preprocessing of cabbage after pretreatment with cow dung to 2:1 ratio of mixture,the fermentation temperature 37.2?,the concentration of the feed liquid3.1%,mixing interval 25.6 h/time under the condition of anaerobic digestion.The optimized process of celery was as follows: pretreatment of celery with ultrasonic crushing power of 30%.The pre-treated celery and cow dung were mixed in a ratio of 3:1,and anaerobic digestion isconducted under the conditions of 38.7 ? fermentation temperature,2.7% solid-liquid concentration and 26.8 h/time stirring interval.This process can improve the methane production rate and methane content of vegetable waste and cow dung and provide theoretical basis for the realization of co-digestion.