Study On Anaerobic Fermentation Technology Of Agricultural Straw Strengthened By Woody Biochare

Anaerobic fermentation is one of the important technical approaches for organic waste treatment.However,there were still some bottlenecks in the study of anaerobic fermentation.For example,in the process of processing organic waste under high concentration,the physical and chemical properties of anaerobic fermentation substrates could not matched the physiological and metabolic demands of microorganisms,and the accumulation of intermediate metabolites(ammonia nitrogen,organic acids,etc.)affected the microbial activity.At the same time,it also led to problems such as slow substrate degradation,low biogas production efficiency and insufficient fermentation stability.In recent years,biochar had been used in the study of anaerobic fermentation,which had effectively improved the treatment efficiency of organic wastes in the anaerobic fermentation process and the gas production capacity of the system.However,the current research on biochar enhanced anaerobic fermentation technology is not systematic enough and the technology is not mature enough.In this study,forest harvesting residues were used as ligneous biochar raw materials,and biochar was prepared by using biomass continuous carbonization internal heating pyrolysis device.At the same time,advanced instruments such as elemental analyzer,specific surface and aperture analyzer,scanning electron microscope,gas chromatography,chemical analyzer,inductively coupled plasma(ICP)analyzer were used to characterize the physicochemical properties of biochar.Next,with corn straw as anaerobic fermentation substrates,using AMPTS automatic methane potential test system and continuous anaerobic fermentation platform,etc.,by controlling the biological carbon type,particle size,ash content,and add a dose of key factors,such as the biochar strengthening sequencing batch type anaerobic fermentation and high load under the condition of continuous anaerobic fermentation research.Through the investigation of biogas composition,yield,system ammonia nitrogen,organic acid content,microbial community characteristics,the relationship between microorganisms and various environmental parameters,etc.,the influence of biochar on anaerobic fermentation gas production performance and system long-term operation stability was comprehensively revealed.Main research conclusions are as follows:(1)The wood biochar has complicated pore structure,high ash content,alkaline earth metal elements content,specific surface area,electrical conductivity and strong adsorption ability characteristics,including cypress wood biochar alkaline earth metal elements content in the highest(68.84 mg/g),pH value,specific surface area and adsorption ability to ammonia nitrogen is the largest,and cypress wood biochar,the smaller the particle size,the higher the pH value(10.1)is the highest,the bigger the specific surface area(the maximum is 45.87 m2/g),and the stronger adsorption ability.(2)Woody biochar had a significant effect on the anaerobic fermentation gas production capacity(P<0.05),among which the poplar biochar had the most significant effect on the anaerobic fermentation system(P<0.05),and the smaller the particle size of poplar biochar(particle size<0.5mm),the greater the substrate hydrolysis rate was,and the stronger the anaerobic fermentation system's gas production capacity was.The proper ash content(about 2.6 g/L)can further improve the gas production capacity of the anaerobic fermentation system.(3)When the amount of poplar biochar is 8 g/L,the anaerobic fermentation enhancement effect is the best,which promotes the degradation of substrates,the generation and transformation rate of volatile fatty acids,slows down the rate of NH3-N concentration decline,increases the volume gas production rate by 18.6%,the CH4 content by 7.40%,and reduces the CO2 content by 5.90%.(4)the addition of biochar promoted the growth and reproduction of bacteria(related to hydrolysis and acidification)and archaea(related to methanogenesis),inhibited the growth of Candidatus_Cloacamona related to CO2 production,changed the microbial community structure,and improved the adaptability of microbial flora to the environment.