Methanogenesis Performance Of Representative Components Of Kitchen Waste In Anaerobic Fermentation

The production of kitchen waste in China increased year by year,and its disposal is more severe.Anaerobic fermentation is a kind of ideal treatment and disposal method to kitchen waste,which can make it harmless,stable and resource.This paper is focused on the representative components of kitchen waste.Through batch experiment,the biochemical methane potential,the degradation of organic matter and the release of metabolites of raw and cooked representative components of kitchen waste were investigated under the mesophilic and thermophilic anaerobic fermentation.And the mechanism of anaerobic fermentation of the raw and cooked kitchen waste preliminary discussed.The results are as follows:In mesophilic anaerobic fermentation,the optimum inoculation ratio of the raw and cooked rice were all 1:4,and the maximum methane production were 141.04mL/gVS and 163.12mL/gVS,respectively.In thermophilic anaerobic fermentation,the ideal inoculation rates of the raw and cooked rice were 1:1 and 1:4,respectively,and the maximum methane production were 190.22mL/gVS and 55.38mL/gVS,respectively.In mesophilic anaerobic fermentation,the activity of amylase is higher,but the activity of methanogens is low,so rice is more prone to acidification than thermophilic anaerobic fermentation at low inoculation ratio.After the rice was cooked,it becomes easier to hydrolyze,so the cooked rice was more prone to acidification than the raw rice during the anaerobic fermentation.In mesophilic anaerobic fermentation,the optimum inoculation ratio of the raw and cooked pork were both 1:1,and the maximum methane production were 284.44mL/gVS and 246.96mL/gVS,respectively.In thermophilic anaerobic fermentation,the best inoculation ratio of raw and cooked pork were both 1:2,and the maximum methane production were 82.11mL/gVS and 113.38mL/gVS,respectively.In mesophilic anaerobic fermentation,the optimum inoculation ratio of the raw and cooked fish were both 1:1,and the maximum methane production were 421.71 mL/gVS and 383.77mL/gVS,respectively.The optimum inoculation rates of raw and cooked fish were 1:1 and 1:2,respectively,and the maximu,methane production were 162.57mL/gVS and 204.88mL/gVS,respectively.In thermophilic anaerobic fermentation,protease activity was amplified,protein hydrolysis released TVFA(Total Volatile Fatty Acid)and ammonia nitrogen faster,but the TVFA consumed rate was also quick,so the rate of pH increased faster in thermophilic anaerobic fermentation.Free ammonia is more toxic to methanogens at high pH,so the anaerobic fermentation performance of meat kitchen in thermophilic anaerobic fermentation is poor than that in mesophilic anaerobic fermentation.After cooked,some hydrolyze organic matter in meat kitchen was lost.Thus the release rate of ammonia nitrogen in cooked meat was lower than the raw meat,and the inhibition of ammonia was also weak.Therefore,the anaerobic fermentation performance of cooked meat kitchen is better than that of raw one.In mesophilic anaerobic fermentation,the best inoculation ratio of animal oil and vegetable oil were 1:2 and 1:4,respectively,and the maximum methane production were 374.7mL/gVS and 225.72mL/gVS,respectively.In thermophilic anaerobic fermentation,the optimum inoculation rates of animal oil and vegetable oils were 1:1 and 1:2,respectively,and the maximum methane production were 513.70mL/gVS and 291.73mL/gVS,respectively.Oil is easy to form oil film that can covers the surface of microbial cells,and inhibiting the use of TVFA.High temperature can improve the diffusion coefficient and solubility of oil,thus make it more susceptible to be used by microorganisms at high temperature.Therefore,the performance of oil in thermophilic anaerobic fermentation is better than that in mesophilic anaerobic fermentation.In mesophilic anaerobic fermentation,the ideal inoculation ratio of the raw and cooked celery were both 1:2,and the maximum methane production were 124.04mL/gVS and 128.5mL/gVS,respectively.In thermophilic anaerobic fermentation,the best inoculation ratio of raw celery was 1:1,the maximum methane production were 231.82mL/gVS and 192.59mL/gVS,respectively.In mesophilic anaerobic fermentation,the activity of methanogens is lower than that in thermophilic anaerobic fermentation.Therefore,the accumulation of TVFA is higher,and the pH is lower in mesophilic anaerobic fermentation.TVFA is more toxic to methane bacteria at low pH.That is why the mesophilic anaerobic fermentation performance of celery is poor than that in thermophilic anaerobic fermentation The structure of the celery was destroyed after cooking,and became easily to be hydrolyzed,so it was more prone to acidification.Therefore,the performance of the raw celery is better than the cooked one.