Co-digestion Of Bagasse And Kitchen Waste For Methane Production

With the improvement of people’s quality of life,the emissions of kitchen waste is increasing day by day.Due to its high salt,high oil,and high protein properties,kitchen waste has become a major problem.Sugarcane is an important raw material for sugar production in China.With sugar producted,a large amount of sugarcane bagasse was also emerged.Because of the high C/N ratio of bagasse,it is hard to degrade,the utilization and conversion technology of bagasse is not perfect,and most of the bagasse being burned or discarded,a large amount of kitchen waste and sugarcane bagasse not only lead to waste of resources,but also cause harm to the ecological environment.Since kitchen waste and bagasse have methanogenic potential,anaerobic fermentation alone has a low methane yield.So bagasse and kitchen waste were mixed or pretreated to improve anaerobic fermentation performance and increase methane yield.To explore the anaerobic co-digestion performance of bagasse and kitchen waste,separate anaerobic digestion studies were conducted on bagasse and kitchen waste.the accumulation methane-producing rate of kitchen waste was 332 m L/g VS,and the bagasse alone achieved 104.95 m L/g VS.To determine the optimum co-digestion ratio of bagasse and kitchen waste,the ratio of bagasse and kitchen waste based on VS ratios were set to 7:3,5:5,3:7,6:4,4:6,2:8 and 1:9.corresponding C/N ratios were 31,28,26,24,23.5,23 and 22,respectively.The results showed that bagasse and kitchen waste had the highest cumulative methane production at 3:7,namely C/N ratio of 23.5,reached to 385 m L/g VS,which increased 15.96% and 266.84% than bagasse and kitchen waste anaerobic digestion alone.In the anaerobic digestion,both mixed fermentation and pretreatment are effective way to improve the methane production of lignocellulosic materials.To explore the best pretreatment method for bagasse and the effects of pretreatment on the methane yield by bagasse anaerobic digestion,five pretreated by ethanol-water,hot water,8% Na OH,5% H2SO4 and Coriolopsis gallica were used to pretreat bagasse and then anaerobic fermentation.A set of experiments revealed that not all pretreatment can improve the yield of the bagasse anaerobic co-digestion the cumulative methane yield of bagasse which pretreated by 8% Na OH(515.11 m L),hot water(128 m L)and ethanol-water(261.14 m L)were 3.60 times,0.13 times and 1.33 times higher than control(111.94 m L).Among them,the bagasse pretreated by Coriolopsis gallica showed the lowest methane yield,achieved 93.2ml.what’s more,the bagasse pretreated by 5% H2SO4 and Coriolopsis gallica both lower than control.In order to compare the methane yield producted by co-digestion of kitchen waste and pretreated bagasse.Bagasse respectively pretreated by ethanol-water,hot water,8% Na OH,5% H2SO4 and Coriolopsis gallica and kitchen waste were mixed respectively based on the optimum co-digestion VS ratio to produce methane.As a result,the bagasse pretreated by 8%Na OH and ethanol-water mixed with kitchen waste still showed strong methane-producing potential,and the cumulative methane production reached to 2120.18 m L,2433.19 m L and 1424.44 m L,1.40 times,1.76 times and 0.61 times higher than control ones(882.3m L).After 5% H2SO4 pretreated,the methane yield was inhibited whether in separate digestion or co-digestion.It was worth noting that the methane yield through the bagasse which pretreated by high temperature hot water co-digestion with kitchen waste was inhibited.In this study,the problems of easily acidified by kitchen waste single digestion and low methane production of bagasse were studied.Three groups of experiments were conducted to explore the optimal methanogenic conditions for each group and improve the stability of the anaerobic digestion system.The first one was bagasse and kitchen waste co-digestion based on different VS ratios,another one was pretreated and untreated bagasse anaerobic digestion alone,co-digestion of pretreated bagasse and kitchen waste was the last group under the optimum VS ratio.The results provided some basis for studying the pretreatment of high-performance methane production technology and different biomass raw materials combined methanogenic process.