Study On Hydrogen And Butanol Produced Mechanism By Anaerobic Fermentation Of Food Waste

With the rapid development of society and economy,people’s demands for living standards have been increasing.Food waste emissions have increased year by year and its disposal often brings secondary pollution to the environment in China,as well as the waste of biomass resources.In recent years,anaerobic fermentation technology has been maturing.Anaerobic fermentation on the production of hydrogen and butanol using anaerobic activated sludge and rejected material has attracted much attention.The anaerobic fermentation of food waste can not only efficiently convert waste resources into bio-hydrogen,bio-methane,and bio-butanol,but also avoid secondary pollution caused by landfill and incineration.This article explores the impact of food waste load on hydrogen production performance through intermittent and continuous fermentation.Wild bacteria which produces butanol were screened from different bacterial source,and the butanol accumulation patterns during fermentation based on different substrates were studied,as well as the characteristics and mechanism of butanol production.The batch-type fermentation results of food waste showed that the load had a significant effect on the gas composition and gas yield.When the load was low（2-8g-VS/L）,the biogas components were dominated by CH₄ and CO₂.After reaching 10g-VS/L,the gas composition was dominated by H₂ and CO₂;when the load was 2g-VS/L,the methane concentration in the biogas was as high as 90%,and the methane yield was 212.99 m L/g.VS.When increased to 30g-VS/L,the H₂ and CO₂contents were 50%and 48%,respectively,and the hydrogen yield was 96.67mL/g.VS.The main VFAs were butyric acid,acetic acid and propionic acid,which belinged to butyrate-type fermentation.Through analysis of the anaerobic microbial community structure in the system,the results showed that Ornatilinea,Levilinea,and Bellilinea were the dominant bacteria in the low load system,and optimum pH was 6.0-8.5.In high load environment,Clostridium sensu stricto,Trichococcus are the predominant microflora,and acetic acid,butyric acid and H₂ were mainly produced,which led to a change in the structure of the flora within the system from the predominant predominance of methanogens to the preponderance of hydrogen-producing bacteria.In addition,the effect of food waste on the performance of hydrogen production by continuous hydrogen-producing was explored.The sludge was treated with alkali to inhibit the activity of methanogens.The results showed that optimum load was 15 g-VS/L,and the total gas cumulative production reached 14440 m L;the proportion of H₂ in the early stage of fermentation was relatively large,reached 60%-70%,no CH₄ was generated;The fermentation started to produce CH₄（3%-29%）in the 3th batch,and H₂ content decreased,CH₄production gradually decreased after the 6th batch;the ammonia nitrogen concentration gradually increased after each batch of fermentation,and which inhibited the activity of methanogens.In order to obtain the butanol-producing strains of excellent performance,and use food wastes et al.the butanol-producing strains:NG1311,NG132 and CC were separately screened from soil and food waste.NG1311 and CC had the same colony morphology,showing white,prominent,round,opaque;single colony morphology of NG132 was different from that,and showed gray,round,slightly prominent,and the edges were slightly irregular.After the three strains were stained by gram and spore,they were examined by microscopy.The results showed that the strain was purple,indicating that the strain was gram positive bacteria.The spore was a fusiform,indicating that the strain was clostridium difficile and belonged to anaerobes.After three strains were fermented by 7%corn mash,the amount of butanol produced by NG1311 was 0.76 g/L,the highest among results.The main organic acid products were butyric acid,acetic acid and propionic acid.The influence of different substrates on the butanol production was studied by using commercial bacterial strain:Clostridium acetobutylicum DSMZ 792.The results showed that the yield of fermentation solvent with corn mash was the highest,the yield of butanol and total solvent reached 11.95 g/L and 18.45 g/L respectively,A:B:E was 3:6:0.5,and the Clostridium acetobutylicum DSMZ 792 could efficiently use corn starch.In order to reduce the production cost of fermentation,the production of butanol and total solvents was 2.52 g/L and 3.71 g/L,respectively,when food waste was used as substrate of the food cron.The radio of A:B:E was 3.25:9:1 in which butanol accounted for the majority,in this way,food waste was conducive to the production of butanol fuel.