Study On The Efficacy And Mechanism Of Enhancing Odd Carbon VFAs By Anaerobic Fermentation Of Hogwash Waste Grease

Hogwash waste grease has the characteristics of easy availability and high organic matter.It is not only an environmental pollutant but also an ideal waste resource.The resource utilization of hogwash waste grease can not only improve the utilization rate of waste resource production capacity in China but also enhance the utilization value of hogwash waste grease.Anaerobic fermentation is currently the mainstream method of hogwash waste grease resource utilization.The effect of anaerobic fermentation of hogwash waste grease to produce Volatile Fatty Acids(VFAs)is different from other wastes.The production of VFAs is mainly based on Odd Carbon Volatile Fatty Acids(OCFA).And the high concentration of OCFA can be used as a carbon source to synthesize biodegradable plastic Polyhydroxybutyrate(PHV)with excellent toughness,which lays the foundation for directional control of PHV and reduction of synthesis cost.Therefore,the anaerobic fermentation of hogwash waste grease to produce OCFA provides a valuable research approach for waste resource utilization and has broad development prospects.This subject aims to strengthen the production of OCFA in hogwash waste grease and study the mechanism of its production.Using hogwash waste grease as the research object,using batch tests to study the effect of oil content on OCFA production from hogwash waste grease.The changes of VFAs concentration,OCFA concentration and dissolved organic matter during fermentation were investigated.At the same time,the optimal oil content of OCFA produced by anaerobic fermentation of hogwash waste grease was determined by response surface methodology.In order to improve the hydrolysis efficiency of hogwash waste grease and promote its OCFA production efficiency,temperature,lipase,and ultrasonic pretreatment technology are used to strengthen the production of OCFA by hogwash waste grease.Investigate the effect of three pretreatment techniques on the concentration of OCFA,and determine the best pretreatment technique to promote the production of OCFA in hogwash waste grease.On this basis,by studying the change of Long Chain Fatty Acids(LCFA)content and composition in hogwash waste grease,combined with the analysis of microbial community structure,the mechanism of anaerobic fermentation of hogwash waste grease to produce OCFA was explored.The conclusion of the study is as follows:The oil content of 10 g/L is the critical point for anaerobic fermentation of hogwash waste grease to produce OCFA.When the oil content is less than 10 g/L,the increase in oil content promotes the concentration of OCFA and the optimal fermentation time for acid production,while above 10 g/L,the higher the oil content,the lower the acid production concentration and the best fermentation time lags.At the same time,the optimal conditions for the anaerobic fermentation of hogwash waste grease obtained by response surface method are: the fermentation time is 5.2 days and the oil content is 11.32 g/L.Ultrasound is the best pretreatment technology to promote anaerobic fermentation of hogwash waste grease to produce OCFA.The optimal ultrasonic intensity is 300 W/L,which can increase the proportion of OCFA/VFAs in the reactor to 82%.Compared with the other two pretreatment technologies,the ultrasonic pretreatment technology has the best effect and the best stability on the production of OCFA in hogwash waste grease,and it can also effectively promote the dissolution of propionic acid in the hogwash waste grease.LCFA has a significant effect on the production of OCFA in hogwash waste grease.The main components that affect the production of OCFA in hogwash waste grease are palmitic acid and oleic acid.Among them,oleic acid is abundant in hogwash waste grease.After ultrasonic pretreatment,the oleic acid content and proportion increase significantly,and oleic acid degradation can produce higher concentration of propionic acid,so oleic acid is the dominant factor affecting the production of OCFA in hogwash waste grease;There are a large number of bacteria related to anaerobic fermentation production of OCFA in the reactor,such as Veillonellaceae fungus,Propionispira genus,etc.,which is one of the reasons that the anaerobic fermentation of hogwash waste grease to produce VFAs is mainly caused by OCFA.In summary,controlling the oil content in the reactor and using ultrasonic to pretreat hogwash waste grease can significantly intensify the system's production efficiency of OCFA.In addition,the existence of a large amount of oleic acid and propionic acid-producing bacteria in the system is one of the reasons that promote the production of OCFA in hogwash waste grease.