Study On Anaerobic Digestion Of Food Waste:Effect Of Pretreatment

With the continuous growth of the economy,the gradual improvement of the quality of residents' life,the amount of food waste in our country is huge.Anaerobic digestion technology not only produce clean gas energy methane but also dispose food waste harmless,which has benefits to environment and economy.Therefore anaerobic digestion has been considered as a promising energy-producing process for food waste treatment.This dissertation studied the anaerobic digestion technology of food waste,the effects of VS inoculation ratio,temperature,agitation speed,ultrasonic pretreatment,oil content,lipase and emulsifier pretreatment were studied in batch anaerobic digestion for food waste.This dissertation also studied the gas production characteristics of food waste anaerobic digestion,the main factors affecting the system performance and stability were discussed as well.By comparing the experiment results,this dissertation try to provide a theoretical basis and reference for the development of efficient and stable food waste anaerobic digestion.In the optimization experiment of basic conditions,when VS inoculation ratio,temperature and agitation speed were 40%,35? and 200 rpm,the anaerobic digestion system started quickly and had higher biogas production.For ultrasonic pretreatment,the effect of ultrasonic is closely related to ultrasonic frequency,sound energy density and time.Lower ultrasonic frequency,higher sound energy density and longer pretreatment time,the effect ultrasonic pretreatment was better.The SCOD of food waste was higher after cracking.Under the ultrasonic condition of 25 kHz,16 min and 1300 W/L,for the four components of food waste,the growth rate of SCOD was rice>pork>cabbage>tofu.In addition,ultrasonic pretreatment can improve the anaerobic digestion performance of food waste and increase the biogas production.Compared with the blank group,the total methane production of 1-9 group increased by 17.87%,and the highest increased by 34.48%.Ultrasonic pretreatment also increased the biodegradability of food waste.In the range of experimental parameters,the better effect of ultrasonic cracking,the better the removal efficiency of TS and VS.High oil content can improve food waste gas production potential.When the oil content below 7%,the effect of oil content on anaerobic digestion of food waste was positive,the total methane production increased with the increase of oil content.Emulsifier can increase the contact area of microbial and oil by forming micelles.Compared with the blank group,the experimental group after added emulsifier had lower pH,indicated emulsifier can promotes the lipid hydrolysis.In the experimental range,the methane content after added emulsifier increased slightly,the more adding amount of emulsifier the more methane yield,up to 288.85 mL CH4/(g·VS).Emulsifier can improve the lipid biodegradability of food waste,making it easier to be absorbed by microorganisms,increase the removal rate of organic matter.Triglyceride can be hydrolyzed into glycerol and fatty triglyceride by lipase.After adding lipase,the hydrolysis rate of oil in food waste is faster,and lipid becomes more easily absorbed by microorganisms.The sequence of factors affecting the food waste emulsifier and lipase pretreatment were determined by response surface methodology,and the biogas yield polynomial model of food waste emulsifiers and lipase pretreatment was established.