Hydrogen Production From Characteristic Components Of Kitchen Waste By Combining The Anaerobic Digestion And Microbial Electrolysis Cells(MEC)

The rapid growth of food waste has a serious threat to ecology and human health,fortunately,the organic nutrients it contained are full of application value.Hence,the VFA（volitate fatty acid）obtained from food waste by anaerobic digestion can be used as the substrate of MEC（miceobial electrolysis cells）,which is a new type of hydrogen production method.Based on the characteristics of starchy sugar and high-protein substances in food waste,the anaerobic digestion technology was used to produce VFAs with pork and the pork mixtured with food waste as the substrate.Moreover,the rice and its digestion liquid,the pork and its digestion liquid were used as the MEC substrate to explore the difference of hydrogen production characteristic.And the aim is explore the key factors which affect the VFA production performance of anaerobic digestion and the hydrogen production performance of MEC by using the characteristic component of food waste.Through the different pH aerobic pre-treatment,the acidogenic performances of pork and pork mixtured with a certain proportion of food waste were explored.The results showed that in the aerobic pretreatment group with pH 4.5,8.0 and 10.0,the VFAs production performance of the two substrates was higher than that of the untreated group,and the VFAs in all group were mainly consisting of acetic acid and n-butyric acid.The maximum acid production was both achieved at pH=8.0 treatment groups for two kinds of substrate.The maximum VFAs yield for pork and pork mixture with a certain proportion of kitchen were 32.84 g COD/L and 34.18 g COD/L,respectively,and had an improved percent of 47.31%and 41.36%compared with untreatment group,respectively.The rice and its digestion liquid,the pork and its digestion liquid were used as the MEC substrate to explore the difference of hydrogen production performance.And the result showed that the hydrogen production performance of pork was poor than the anaerobic digestion liquid of pork.Furthermore,when the anaerobic digestion liquid of pork was used as the substrate,both the hydrogen production performance and the organic matter degradation rate in MEC acclimated by BSA were higher than that acclimated by NaAC.The hydrogen yields of the two MEC were 23.15 mmol H₂/g COD and 16.46 mmol H₂/g COD,respectively.The maximum organic matter degradation rate was 84.51%and 72.14%,respectively.The difference was mainly caused by the improvement of the degradation ability of isobutyric acid and isovaleric acid in the subtrate.Among the MEC hydrogen production with different protein content,the low protein content rice liquid contained more acetic acid,and hence the corresponding hydrogen yield was higher,and the hydrogen yield was 18.88 mmol H₂/g COD and 14.64mmol H₂/g COD,respectively,while the current density is equivalent.Moreover,as a result of the higher proportion of carbohydrates in rice raw liquid,the higher hydrogen yield was obtained by using it as the MEC substrate.On the other hand,the lower hydrogen yield was obtained when the anaerobic digestion liquid of rice was used as substrate for the main component of digestion liquid is n-butyric acid,which is not easily degraded in MEC.The hydrogen yields were 10.17 mmol H₂/g COD and 6.86 mmol H₂/g COD,respectively.Furthermore,free ammonia has a great influence on the performance of MEC.When the free ammonia concentration of the system is high（FAN=0.0126mg/L）,the current density and hydrogen production are obviously improved.They were1.72 times and 1.46 times of the corresponding values for low free ammonia concentration（FAN=0.0013 mg/L）.