Power Generation And Hydrogen Produciton From Tubers Waste Based On Bioelectrochemical Systems Microbial

With the increasingly severe challenges of environmental protection, starch isplaying an indispensable role in our daily life and the quality of starch also affectsour health. In northern China, potatoes are the main crops for the production ofstarch, while in most parts of southern China cassavas are the main source of starchproduction. However, large amount of attached products with rich nutrient areproduced except starch when potatoes and cassavas are utilized to produce starch,among which are mainly potato waste residues and cassava residues. Theseresidues have been intense threats to the surrounding environment. The wastewaterformed during the process of residues decay will affect the growth of vegetationand the rancid smell will cause air pollution which threatens the health of humansand animals. The conventional methods to disposal of these residues are using themas livestock feed, food and feed additives, or organic fertilizers after fermentation.Yet, the results are not satisfactory compared to the large amount of resourcesconsumed. So how to recycle these nutrients enriched residues and degrade them ina pollution-free way while produce value-added products has becoming an urgentissue in the academic world.In the present study, single room air-cathode Microbial Fuel Cells （MFCs）with the effective volume/total volume being25ml/27ml were researched as anovel way to dispose of potato waste residues and cassava residues. Differentorganic loading rates were researched to demonstrate their effects on theperformance of these biological electrochemical systems. The optimal organicloading rate was suggested based on the consideration of maximum organicsremoval rate and electricity generation. The potato waste residues were diluted to1g/L,5g/L,10g/L and20g/L using50mM PBS, while the concentrations of dilutedcassava residues were1g/L,5g/L and10g/L. These residues of differentconcentrations were fed to MFCs as substrates. After stable operation of MFCs wasobtained, electrochemical performances were conducted. To further study themicrobial relationship between the communities, the total DNA of the anodebiofilms were extracted for454pyrosequencing. After that, MFC reactors weretransferred to Microbial Electrolysis Cells （MECs） to demonstrate the feasibility ofutilizing potato waste residues and cassava residues to produce methane andhydrogen. The produced biogas was collected and analyzed to calculate theproduction rate and recovery rate of methane and hydrogen. So the optimal organicloading rate was determined for better utilization and degradation of these residues. When potato waste residues were used as the substrates of MFCs, themaximum organic removal rate and electricity generation was obtained at theconcentration of10g/L. Based on the results of454pyrosequencing, the dominantgenera were starch-degrading bacteria Bacterioide and Flavobacterium andexoelectrogenic Geobacter and Dysgonamonas. The synergistic interaction formedbetween starch-degrading bacteria and exoelectrogenic drove the highly efficientMFC systems with simultaneous organic removal and electricity output.While using cassava as the substrate of MFCs, the maximum electricitygeneration was5g/L with18W/m³.Compared with the potato waste residues, theelectrochemical performance was slightly inferior since different percentages butsimilar components of nutritions. With the percentage which was lower starchwhile higher percentage of cellulose content in cassava residues might result inlonger batch period accompanied with shorter reaction time, degration rate oforganic loadings decreased and maxium voltage lasted shorter. Later phase of theexperiment period we choosed the high power generation efficiency ones for thefurther research with the two substrates’ organic loadings5g/L,10g/L respectively.Then MFCs turned into MECs for biohydrogen production. Sequently we analysedthe effects of the hydrogen production for the further detection of the utilization oftubers starch waste residues. With potato starch and cassava starch waste residue asthe substrate in MEC, the concentration of organic matter which was appropriatefor hydrogen production was5g/L.The maximum volumes and rates of hydrogenproduction were0.42mL-H₂/g-COD and1.277mL-H₂/g-COD,0.278mL-H₂/g-COD/d and0.851mL-H₂/g-COD/d respectively to use potato starchand cassava starch waste residue as the substrate.