The Effects And Mechanism Of Deodorization By Combining Biochar With Functional Microorganism Or MgO Desulfurization Residue During Chicken Manure Composting

Chicken manure is an important livestock waste.Aerobic composting is reported as an effective way for the successful disposal of solid waste because of the increasing evaporation of water,low cost and stable good quality of the products,which can partially replace the chemical fertilizer.Nevertheless,the emission of odors,such as ammonia,hydrogen sulfide,and volatile organic compounds（VOCs）,is one of the most crucial problem during the composting progress,which may cause another serious pollution to the environment.How to reduce or even eliminate the odors pollution has become the key factor influencing the development of poultry litter composting.Engineering is one of the reducing methods and there are some problems with this method,such as increasing building and working cost for the deodorization installation,low efficacy and reducing fertilizer quality by flowing away nitrogen and sulphur.In the present study,therefore,composting deodorization in situ was conducted.Biochar,prepared by atmosphere furnace,was isolated as the core material due to its properties such as odors adsorbent,functional microorganism carrier,and acidity regulator at critical area.The majority objective of the study was combining biochar with deodorizing microorganism or MgO desulfurization residue to achieve deodorizing in situ during chicken manure composting and find out the underlying mechanism by using composting reactor,pot experiments,krystal diffraction,and high-throughput sequencing methods.The results were listed below.（1）Biochar prepared from citrus branch and peanut shell under the same condition exhibited significantly difference in output rate,elements content,p H value,bore diameter,pore volume,specific surface area,scanning electron microscope,infrared spectrum,and energy spectrum map.The specific surface area of citrus-branchs-biochar prepared at 700oC was 6.27 m²/g and the p H was 10.02,while the specific surface area of peanut-shell-biochar prepared at 700oC was 2.58 m²/g and the p H was 10.38.Significant relationship was observed between most of the characterization and pyrolyzation temperature,the equation with high correlation coefficient could be fitted and the coefficient of correlation was up to0.9524.（2）The ammonia and H₂S adsorption by citrus-branchs-biochar and peanut-shell-biochar prepared at same temperature was different between each other,so was between the same biochar prepared at different temperature.The H₂S adsorption by citrus-branchs-biochar and peanut-shell-biochar was increasing under higher pyrolysis temperature and the adsorption abilities were up to 173.70 mg/g and 219.92 mg/g,respectively.Citrus-branchs-biochar prepared at 325oC and peanut-shell-biochar prepared at 350oC showed the highest one-time adsorption ability of ammonia with 28.43 mg/g and 18.04 mg/g,respectively.The mock experiment of ammonia-H₂S-ammmonia adsorption by biochar indicated that greater adsorption potential could be motivated.In addition,the accumulation of ammonia adsorption by citrus-branchs-biochar prepared at 325oC was 129.66 mg/g,it was higher than that by peanut-shell-biochar prepared at 300oC,which was 93.01 mg/g.Furthermore,the accumulation of H₂S adsorption also significantlyincreased.（3）Citrus-branch-biochar was chosen as the carrier of functional microorganism and culturing experiment was conducted to isolated.The biochar was combining with VT-400deodorizing microorganism.The culturing lasted for 30 days and the population of microorganism was decreasing during the experiment.15 days after the experiment conducting,the population of functional bacteria,fungi,and actinomycetes were began to decreasing rapidly by two order of magnitude.According to the population determined at 5and 10 days after inoculation,the citrus-branchs-biochar prepared at 325oC was chosen for the best functional microorganism carrier.Based on the overall consideration of the strongly adsorption of ammonia and H₂S and lower cost for preparing,the citrus-branchs-biochar prepared at 325oC was finally used as functional microorganism carrier and to prepared functional microorganism granular biocha.（4）Deodorization by functional microorganism granular biochar（CDB）was significantly stronger than those by individual deodorizing microorganism（CD）or biochar（CB）and control treatment（CC）.The accumulation of ammonia emission by CDB was reduced by 29.7%,which was higher than that by CD（15.2%）and CB（13.1%）;The accumulation of H₂S emission by CDB was reduced by 17.2%,which was also significantly higher than that by CD（7.04%）and CB（13.6%）.The total emission of VOCs by CD,CB,and CDB were 7.4%,27.17%,and 28.42%,respectively,lower than that by CC.In addition,the emission of methyl disulfide was reduced by 8.8%,30.42%,and 29.5%by CD,CB,and CDB,respectively.Furthermore,the total nitrogen and sulphur contents were both increased in the compost from CDB by 16.96%and 14.46%,respectively.（5）The deodorization in situ by combination of granular biochar and MgO desulfurization residue（CMB）was stronger than those by individual MgO desulfurization residue（CM）or biochar（CB）and control treatment（CC）,but the effect on the Dimethyl sulfur reduction was not very well.Compared with control,the total emission of VOCs in treatment CB,CM,and CMB were reduced by 27.17%,41.67%,and 44.63%,respectively,and the emission of methyl disulfide was reduced by 30.42%,54.34%,and 55.27%,respectively.Furthermore,the p H value was significantly decreased in treatment CM,but the total nitrogen content was increased.The ammonia reduction in situ in treatment CM was better than that in CB,but the emission of H₂S was increased.The total nitrogen content in the compost from CMB was increased by 67.7%compared with CC and it was significantly higher than that from CB and CM,which was increased by 8.15%and 29.96%compared with CC.（6）According to the results from scanning electron microscope（SEM）and X ray,it was proven that magnesium ammonium phosphate crystal was formed after the MgO desulfurization residue adding to the compost.High-throughput sequencing results showed that significantly influences on bacterial community were observed by different treatments.The dominate phylum in six treatments were Proteobacteria,Actinobacteria,and Bacteroidetes.The relative abundance of Proteobacteria were significantly increased in treatment CM and CMB.In addition,the dominate genera in treatments CB,CD,CDB,CM,and CMB were significantly different with control and there were 10,12,9,13,and 12 genera,respectively,which were totally different with control.Furthermore,the PCA and NMDS analysis indicated that the structure and diverdity of bacterial community was significantly different with control.（7）Two-season pot experiment was conducted to evaluate the effect of mature compost from CC,CD,CB,CDB,CM,and CMB on the growth and quality of Chinese flowering cabbage and Leaf lettuce.The results indicated that treatments CDB and CMB were able to increase the yields of vegetables and decrease the nitrate content,which were significantly better than CB and CM.The nitrate contents in CDB and CMB were reduced by 17.4%and27.6%,respectively,compared with CC.The soil alkali-hydrolyzable nitrogen（AN）,and available potassium（AK）were decreased in different treatments.The contents of vitamin C and soluble sugar were significantly increased in treatments CM and CMB,but the soil p H and content of AK were lower than those in control.In conclusion,the functional microorganism granular biochar made from citrus-branchs-biochar prepared at 325oC and deodorizing microorganism could effectively reduce ammonia,H₂S,and parts of VOCs emission during chicken manure composting,promote the quality of the compost product,increase the yield of vegatables,and decrease the nitrate content.The underlying mechanism may be attributed to the significantly changes in microorganism community of compost and the properties of the additive materials.The findings in the present study have broad application prospect in guiding composting enterprises to deodorizing in situ.