Development Of Technology And Equipment For Rapid And Harmless Treatment Of Low C/N Waste (Chicken Manure) Without Auxiliary Materials

The livestock and poultry breeding sector in China has witnessed significant growth,leading to a surge in the annual production of waste,including manure.The latest data revealed that the yearly output of livestock and poultry manure has surged to 3.8 billion tons in China,exerting considerable strain on environmental conservation efforts.Consequently,the harmless disposal of livestock and poultry manure has become an urgent problem to be solved in our country.Aerobic fermentation is a widely acknowledged and effective method for the harmless treatment of livestock and poultry manure.This process harnessed the metabolic activities of microorganisms to decompose the raw materials into harmless substances.As these materials degraded,heat was produced,which served to eliminate harmful microorganisms,insect eggs,and weed seeds present in the substrate,and finally realized the innocuity of the raw materials.In conventional aerobic fermentation of livestock and poultry manure,straw is commonly used as an auxiliary material to regulate the initial C/N ratio to 25-30.This approach has been adopted to achieve better harmless treatment.The use of straw as an auxiliary material in aerobic fermentation of livestock and poultry manure has become challenge due to various issues,including seasonal changes and transportation difficulties.Meanwhile,low C/N fermentation presented distinct challenges,such as slow heating rates and substantial nitrogen loss.Therefore,the development of auxin-free fermentation processes and equipment with improved heating rates and nitrogen fixation effects was critical in achieving efficient and environmentally sustainable treatment of livestock manure with low C/N.The study employed experimental methodologies to investigate the rapid and harmless treatment of pure chicken manure without the incorporation of auxiliary materials.Moreover,the study comprised the design and production of a drumtype equipment for harmless treatment,and evaluated the performance and stability of equipment through fermentation tests.The specific research contents of this thesis were as follows:(1)Determination of process conditions for low C/N auxin-free fermentation.Pure chicken manure(C/N=11.54)was used as raw material.Based on the analysis of basic physical and chemical properties,the raw material parameters(moisture content,p H)and treatment methods(pre-culture,addition of microbial agents)were investigated experimentally.The study findings indicated that the pile exhibited the fastest heating rate at 50% and 55% initial moisture content,while the overall fermentation temperature was also higher compared to 60% and 65% moisture content.Moreover,the highest accumulated temperature in the fermentation process was observed at 55% initial moisture content,followed by 50%.It was shown that setting the initial p H values to 6.5,7.0,and 7.5 could effectively reduce nitrogen losses and simultaneously improving the rate of fermentation warming and overall fermentation temperature in p H regulation experiments.During the experiment on fermentation raw material pre-culture,the raw material was pre-cultured at different temperatures(25 ℃,30 ℃,35 ℃,and 40 ℃).The results showed that the fermentation at 35 ℃ exhibited the fastest warming rate and highest peak temperature.The analysis of bacterial community in fermentation samples demonstrated that pre-culturing could alter the microbial community structure,enhance the abundance of Pseudomonas,and Bacillus,and facilitate the temperature increase of the pile.These findings suggested that pre-culturing could improve the efficiency of harmless treatment.To enhance the harmless effect of the fermentation process,an experiment was conducted to evaluate the impact of 35 ℃ preculture followed by the introduction of 0.1%(w/w)biochar-based bacterium.Results indicated that the temperature of fermentation,warming rate,and germination index were higher than those of the control and bacterium groups.These findings suggested that temperature preculture and biochar-based bacterium had a synergistic effect on the fermentation process,facilitating fermentation warming,promoting the efficacy of the harmless treatment,and accelerating the decomposition of organic matter.(2)The mechanical structure design of the drum reactor was developed based on the results of preliminary experiment.The design included the drum body,auxiliary thermal device,mixing and ventilation structure,insulation layer structure,inlet and outlet structure,and support device,among others.ANSYS was used to conduct mechanical force analysis of key components.The results indicated that the deformation of each component was less than 0.1 mm,and the stress strength was within the allowable range of stress limit,which satisfied the mechanical design requirements.(3)The experimental validation of the drum harmless fermentation plant was conducted under low C/N auxin-free fermentation process conditions.The findings revealed that the test group TJ,which involved heating chicken manure at 35°C using auxiliary heat structure with 0.1%(w/w)biochar-based bacterium,demonstrated increased fermentation warming rate and temperature,prolonged high-temperature period,and was less affected by environmental factors.Moreover,the total absolute abundance of antibiotic resistance genes(ARGs)in TJ decreased by 63.85% and increased by 28.73%compared to the conventional strip-palletized fermentation group CK(35.12%).At the end of fermentation,there was a rebound of mobile genetic elements(MGEs)in CK and the bacterial agent test group CJ,which were elevated compared to the starting phase.However,the absolute abundance of MGEs in TJ decreased by 87.29%,and both integrator genes int1 and intl2 were removed at a rate of over 90%.In conclusion,the use of supporting drum harmless treatment equipment for fermentation under low C/N fermentation process conditions could accelerate the fermentation heating rate,increase the fermentation temperature,achieve a better reduction effect of ARGs and MGEs,and provide technical support for low C/N harmless treatment without auxiliary materials.