Evaluation Of Carbon Emission Reduction Effect Of Hermetia Illucens Transformation Technology And Screening Of Related Function Bacteria

To promote the comprehensive low-carbon and green development,Chinese government has proposed the“Dual carbon strategy”,which has global significance.Meanwhile,with the increasing production of organic waste,the importance of resource utilization of organic waste is increasingly valued.Among various organic waste treatment methods,biotransformation by Hermetia illucens L（Black soldier fly,BSFL）could solve these two problems.As a resource utilization insect,BSFL not only have environmentally friendly and pollution-free processes,but also have high conversion efficiency.The transformation can harvest highly nutritious organic fertilizer and a large amount of insect protein,insect fat,and other by-products.By converting carbon and nitrogen from organic waste into biomass,they can reduce carbon and nitrogen losses during the treatment process,which has great development potential.This study establishes a multiple gases online monitoring system and utilizes a CO₂ absorption and quantification device to conduct carbon balance accounting for the entire process of BSFL conversion and evaluate its carbon emission reduction（CER）.Further targeting a series of related function bacteria through selective isolation and cultivation,detection of related function bacteria,screening of carbon fixing genes,and collaborative transformation evaluation.The main results of this study are as follows:（1）Construction of carbon balance and evaluation of CER in the transformation process of BSFLThis study constructs a multiple gases online monitoring system based on gas integrated sensing probes,achieving online monitoring of 5 gases released during the conversion process of BSFL:CO₂,NH₃,NO_x,H₂S,and CH₃SH.By simulating the material conversion process of BSFL for 6 days,the results show that the total CO₂ emissions from BSFL conversion were about 62.75 kg/t of material,which decreased by 65.71-80.52%compared to composting treatment（usually 183-323 kg/t of material）.Furthermore,we conduct simulated transformation（long-term）experiment of BSFL for 50 day by CO₂absorption and quantification device.The results show that the total CO₂ emissions from the conversion of BSFL were approximately 261.82 kg/t of material,a decrease of 27.37%compared to natural fermentation（360.49 g/kg of material）.Both conversion system experiments demonstrate that process of BSFL conversion has good CER potential.（2）Screening of efficient related function bacteria8 strains of related function bacteria are selected for cultivation of BSFL and their living environment by carbon free culture medium.They are named CO-1（Aquamicrobium sp.）,CO-2（Brucella pseudintermedia）,CO-3（Brucella pseudintermedia）,CO-4（Ochrobactrum sp.）,CO-5（Bordetella sp.）,CO-6（Cellulosimicrobium sp.）,CO-7（Achromobacter sp.）,and CO-8（Alcaligenes sp.）.Through CO₂-fixing efficiency measurement experiments,the results show that the CER potential of CO-2,CO-3,CO-4,CO-5,and CO-7 are relatively strong,with CER efficiency of 5.74,6.19,5.47,7.43,5.78,and 6.02[mg/（h×kg bacterial fluid）].The CER potential of 5 strains of bacteria is evaluated by the synergistic transformation experiment of related function bacteria and BSFL.The results showed that the direct CO₂emissions of group CO-4 were significantly reduced compared to the group control,by7.09%.The direct CO₂emissions of other groups were significantly higher than those of the group control.Therefore,CO-4:Ochrobacillus sp.has high potential for CER applications.（3）CER evaluation of efficient related function bacteria agent CO-4 synergistically BSFL transformingThe CER of the synergistic BSFL simulation transformation experiment and the synergistic BSFL chicken manure transformation experiment are evaluated.The results show that the total CO₂ emissions are 14.19 kg/t of material and 20.40 kg/t of material,respectively,which are reduced by 6.40%and 5.20%compared to group control（15.16 kg/t of material and 21.52 kg/t of material）.This indicates that the synergistic BSFL transformation with bacterial agent CO-4 can further enhance CER of BSFL transformation.These experiments also estimate the NH₃ inhibition effect of bacterial agent CO-4,and the results show that the total NH₃ emissions are 0.19 g/t of material and 2.28 g/t of material,respectively,which are reduced by 98.06%and 71.96%compared to group control.It indicates that the bacterial agent CO-4 has a good inhibitory effect on NH₃.These experiments also detect the relative abundance of cbb L genes in the transformation matrix.The results show that the relative abundance of cbb L genes group control don’t significantly increase in both experiments,but show significant increase in group CO-4,ultimately increasing by 13.19 times and 287.40 times compared to group control,respectively.TheivCER may be related to the expression of the cbb L gene.The CO₂ emission from BSFL conversion could be converted into other organic matter causing CER,by increasing the expression of the CBB pathway or related carbon fixing pathway.