Mechanism Research On Combined Anaerobic Fermentation Of Food Waste And Corn Straw

China is a great agricultural and populous country,producing huge amount of agricultural waste and food waste every year.If these wastes are not handled properly,it will not only cause the waste of resources,but will pollute the environment.As one of the important ways of energy disposal,combined anaerobic fermentation can make waste to treasure.Biogas produced in the process of fermentation can be upgraded and incorporated into the natural gas pipeline network to achieve high value utilization,and biogas slurry and residues can be made into fertilizer,feedstuff and other nutrients.So more researchers are paying great attention to anaerobic fermentation.Anaerobic fermentation is a complex process involving a variety of micro-organisms and many kinds of biological and chemical reactions.This study investigated gas production potential of food waste and corn straw,simulated dynamics models,and explored the mechanism of internal transformation and microbial community structure of the acid phase and methane phase at different operating conditions.The main conclusions are as follows:(1)The KOH pretreatment can destruct the connection between lignin,hemicellulose and cellulose in corn straw,increasing the surface area.It is beneficial for the fermentation process,the methane yield increase by 1.23 times.The biodegradation rates of food waste,corn straw without pretreatment and corn straw with KOH pretreatment were 54.47%,43.05% and 53.15% respectively.The anaerobic fermentation of food waste worked well,and KOH pretreatment can improve the biodegradation rate of corn straw.(2)Cone model and Modified Gompertz model can simulate the anaerobic fermentation process of three kinds of raw materials in this study well.As can be seen from the simulation parameters,KOH pretreatment can shorten the lag period and increase the hydrolysis rate.The methane production rate of the food waste was higher than that of corn straw significantly.(3)pH of three experiments were adjusted to 5,6,7 respectively,and pH of the control experiment was not adjusted.In these four experiments,the content of carbon dioxide was higher than that of hydrogen.In the experiment without pH adjustment,the value of carbon dioxide content was the highest,while in the experiment with adjusting pH to 5 and 6,the value decreased significantly.In the experiment without pH adjustment,the value of hydrogen content was the smallest,and in the other three experiments,the value increased,and decreased with the increase of pH gradually.(4)VFA concentrations of all these experiments with pH adjustment were larger than the one without pH adjustment.pH adjustment can affect the composition of acid liquid significantly,and benefit to anaerobic fermentation.(5)In the experiment with adjusting pH to 5,hydrolysis acidification products were mainly acetic acid and propionic acid;fermentation type was propionic acid fermentation;the dominant bacteria were Propionibacterium and Selenomonadales.In the experiment with adjusting pH to 6,hydrolysis acidification products were mainly acetic acid and higher butyric acid;fermentation type was butyric acid fermentation;the dominant bacteria were Clostridiales and Pseudomonadales.In the experiment with adjusting pH to 7,hydrolysis acidification products were mainly acetic acid and butyric acid,with a ratio close to 1:1;fermentation type was butyric acid fermentation;the dominant bacteria were Clostridiales,Sphingomo and Enterobacteriales.In the experiment without adjusting pH,hydrolysis acidification products were mainly acetic acid and higher ethanol;fermentation type was ethanol fermentation;the dominant bacteria were Bacteroidales and Lactobacillales.(6)At the beginning,stable and ending stages of the methanation process,the main methanogenic pathways were the hydrogenotrophic methanogenic pathway,the acetoclastic methanogenic pathway and coexisting of the two pathways,respectively.