Analysis Of Biochar On Carbon And Nitrogen Sequestration And Community Succession Of Related Microorganisms In Cow Manuresugarcane Straw Waste Composting

The quality of compost is drastically reduced due to the loss of carbon,which negatively impacts the environment.Reducing carbon emissions and fixing carbon dioxide（CO₂）is the key to focusing on"carbon peaking"and achieving"carbon neutrality".In this study,the relationship between CO₂ emissions,humus substance（HS）formation and cbb L-containing autotrophic carbon-fixing microorganisms（CCAM）was analyzed by adding charcoal to the cow dung-bagasse compost as the experimental group（group B）.The results showed that charcoal could promote the degradation of organic matter（OM）and the formation of HS,enhancing the diversity and richness of the CCAM community,thereby promoting CO₂ fixation and reducing carbon loss during composting.High-throughput sequencing analysis showed that the relative abundances of Actinobacteria and Proteobacteria in group B were significantly increased by30.97%and 10.48%,respectively,compared with the control group（group C）,resulting in a 32.07%increase in CO₂ fixation.In addition,the alpha diversity index of group B increased significantly during the thermophilic period,Shannon index increased by 143.12%,and Sobs index increased by 51.62%.Redundancy analysis（RDA）showed that CO₂ was positively correlated with C/N,temperature,HS and dissolved organic matter（DOM）,while Corynebacterium and Bifidobacterium were positively correlated with temperature,CO₂ and C/N（p<0.01）.To study the impact of carbon-emitting microorganisms on CO₂ emissions and sequestration.In this study,by adding bamboo charcoal as the experimental group（group B）,the metagenomics technology was used to analyze the abundance of relevant CO₂-emitting enzymes gene（pyruvate dehydrogenase,PDH;isocitrate dehydrogenase,IDH;α-ketoglutarate dehydrogenase,α-KGD）and CO₂ fixing enzymes gene（ribulose-1,5-bisphosphate carboxylase/oxygenase,Ru Bis CO）.The results showed that the addition of bamboo charcoal increased the relative abundance of Ru Bis CO gene by 13.22%,improving the diversity of carbon-fixing microorganisms.In addition,in the late stage of composting,bamboo charcoal also inhibited the relative abundance of PDH,IDH,andα-KGD,thereby reducing the release of CO₂ by 16.77%.Bamboo charcoal can also reduce the gene abundance of Methyl coenzyme-M reductase（MCR）,which in turn reduces methane（CH₄）release.RDA showed that Proteobacteria was the dominant phylum in the compost system during the cooling and maturity stages of compost,which dominated the CO₂ emission and was positively correlated with PDH,IDH,and A＿KGD（p<0.01）.In addition,Rubis CO was negatively correlated with OM,CO₂,CH₄（p<0.01）.Therefore,bamboo charcoal can inhibit the activity of CO₂-emitting microorganisms,thereby reducing carbon loss.In addition,the denitrification process is an important cause of nitrogen loss during composting.Therefore,to reveal the effect of bamboo charcoal addition on nitrous oxide（N₂O）emissions and nitrogen fixation.This study analyzed changes in nitrogen transformation,nitrogen function genes and related microbial communities by metagenomics technology,and explored their relationship with N₂O.The results showed that compared with the group C,the N₂O emission in the treatment group B was significantly reduced,and the contents of nitrate nitrogen（NO₃^--N）and total Kjeldahl nitrogen（TKN）were increased by 15.4%and 0.11%,respectively.Metagenomic analysis revealed that the abundances of nap A and nor B genes decreased by 26.9%and 22.44%,respectively,while nitrogen-fixing genes（nif K,nif D,and nif H）only increased by 46.9%,60%,and11.5%,respectively,during the thermophilic period.RDA showed that the emission of N₂O was proportional to the content of NO₃^--N and ammonium nitrogen（NH₄⁺-N）.Denitrification genes are proportional to Proteobacteria,while nitrogen fixation genes are proportional to Firmicutes.Furthermore,at the end of composting,the abundance of Luteimonas in group B decreased by 7.45%,while the abundance of Frankia increased by 27.52%.Therefore,adding bamboo charcoal can enhance nitrogen sequestration by nitrogen-fixing microorganisms,thereby reducing nitrogen loss.Overall,the addition of biochar to cow dung-bagasse compost provided a more favorable environment for microorganisms to increase the relative abundance of carbon-fixing and nitrogen-fixing microorganisms and inhibit the growth of carbon-emitting and denitrifying microorganisms,thereby reducing the loss of carbon and nitrogen,providing a sustainable way to improve the quality of compost products.