Study On Enhancing Means Of Novel Methanogenesis In Organic Solid Waste Fermentation

In recent years,the global energy crisis has become increasingly serious,and the resource disposal of organic solid waste caused widespread attention.The production of organic solid waste is large of low price,such as agricultural solid waste(straw),urban food waste(FW)and waste activated sludge(WAS)from urban sewage treatment.These organic solid wastes have a high carbon content,and biogas energy can be produced with them by anaerobic digestion(AD).However,traditional methanogenesis has slow hydrolysis rate,low methane production,and uneven nutrition.Even if a co-fermentation strategy was adopted,its fermentation potential is still not fully utilized.The discovery of Direct Interspecies Electron Transfer(DIET)is expected to solve the problem of low anaerobic digestion efficiency.According to reports,there are two main modes for establishing and strengthening DIET path: first mode,the addition of conductor materials;and second mode,adding ethanol or using ethanol-type fermentation to produce ethanol to enrich DIET-type partner microorganisms.This paper first studied the effects of the addition of zero-valent iron and conductive materials on anaerobic digestion.The effect of addition of zero-valent iron in the single-phase reactor on the anaerobic digestion of food waste and adding iron-carbon bed in two-phase anaerobic reactor on co-digestion of food waste and corn straw(CS)was studied respectively.It is reported that the addition of zero-valent iron can promote the traditional methanogenic path and the addition of carbon material can promote direct interspecies electron transfer.The ironcarbon bed was added to the methanogenic phase of the two-phase anaerobic reactor called “experiment group”,and the methane yield of experiment group was 35% higher than that of control group.However,the abundance of microorganisms such as Geobacter which can performance DIET in the methanogenic phase was still small.The using of ethanol-type fermentation to establish direct interspecific electron transfer(DIET)to achieve efficient methane production from organic solid waste is considered a promising strategy,yet it has not been successfully applied to anaerobic digestion of organic solid waste.In this study,corn straw(yeast fermentation)was used as a source of bioethanol mixed with waste activated sludge for further anaerobic co-digestion(AcoD).The aim was to establish a methanogenic pathway based on direct interspecific electron transfer(DIET)during the co-fermentation of straw and waste activated sludge.The results showed that the ethanol production from corn straw after yeast fermentation accounted for 11-16% of the total fermentation product,while ethanol was not detected in the precursor phase reactor without yeast.The average methane yield of the yeast group was about 36% higher than that of the control group.Multiple lines of evidence including sludge conductance,effects of activated carbon on methanogenesis and microbial community demonstrated that ethanol from the straw fermentation stimulated direct interspecies electron transfer to be established in the digesters.The results suggested that using ethanol produced from straw was a cost-effective novel way for energy recovery from disposal of agricultural and municipal wastes.