Modified enteromorpha hydrothermal carbon and application thereof in promoting enrichment of clostridium and / or methanosaeta in dry digestion system of kitchen garbage

Abstract

The present application belongs to the technical field of kitchen waste resource, and particularly relates to a modified Enteromorpha hydrothermal carbon and application thereof in promoting enrichment of Clostridium and / or Methanosaeta in a dry digestion system of kitchen waste. The present application optimizes the microbial community structure of the digestion system, enhances the microbial activity, and enriches functional microorganisms such as Clostridium and Methanosaeta by adding an appropriate amount of phosphate-activated magnetic Enteromorpha hydrothermal carbon in the dry anaerobic digestion system of kitchen waste, thereby effectively promoting the dry anaerobic digestion process of kitchen waste and improving the biogas production. The present application has great significance for realizing kitchen waste reduction, harmlessness and resource.

Description

Technical Field

[0001] This invention belongs to the field of kitchen waste resource utilization technology, specifically involving a modified seaweed hydrothermal charcoal and its application in promoting the enrichment of Clostridium and / or methanogenic bacteria in the dry digestion system of kitchen waste. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Anaerobic digestion of kitchen waste transforms organic waste into renewable energy sources such as biogas through a multi-stage biochemical process, representing a key pathway to achieving waste reduction, resource recovery, and carbon emission reduction goals. This technology relies on the synergistic effect of a multifunctional microbial community, including hydrolytic bacteria, acidifying bacteria, acetic acid-producing bacteria, and methanogenic archaea, to generate methane through the stepwise degradation of organic matter (such as carbohydrates, proteins, and lipids). *Ulva prolifera* contains abundant cellulose, polysaccharides, and minerals. After hydrothermal carbonization and modification, it can form a porous carbon-based material with a high specific surface area, possessing the potential to adsorb inhibitors, promote microbial electron transfer, and regulate the community. Current research has found that adding exogenous additives (alkaline substances, biochar, nano-zero-valent iron, etc.) can alter the microbial community structure within the digestive system, enriching specific bacterial groups (such as *Clostridium* and / or methanogenic bacilli) to promote the hydrolysis of organic matter and biogas production.

[0004] Clostridium difficile can convert sugars, peptides, and amino acids in the anaerobic digestion system of kitchen waste into acetic acid, hydrogen, and carbon dioxide, providing raw materials for methanogenic bacteria. Methanogenic bacilli are indispensable functional microorganisms in the anaerobic digestion system of kitchen waste. As the terminal functional microbial community in the anaerobic digestion process, they directly participate in the conversion of organic acids into methane, and their enrichment level directly affects biogas production. Therefore, enriching Clostridium difficile and / or methanogenic bacilli plays a crucial role in the biogas production of the anaerobic digestion system of kitchen waste. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a modified hydrothermal charcoal from *Ulva prolifera* and its application in promoting the enrichment of *Clostridium* and / or *Bacillus methanogens* in the dry digestion system of kitchen waste. The modified hydrothermal charcoal from *Ulva prolifera* of this invention enhances and enriches the activity of specific microorganisms such as *Clostridium* and *Bacillus methanogens* in the dry digestion process of kitchen waste, thereby increasing the biogas production from the dry digestion of kitchen waste.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a modified hydrothermal carbon of Ulva prolifera, wherein the modified hydrothermal carbon of Ulva prolifera is phosphate-activated magnetic hydrothermal carbon of Ulva prolifera, and the preparation method includes: immersing Ulva prolifera powder in an iron salt solution, followed by a hydrothermal reaction to obtain magnetic hydrothermal carbon of Ulva prolifera, then immersing the magnetic hydrothermal carbon of Ulva prolifera in a phosphate solution for reaction, removing it, washing it, and drying it to obtain phosphate-activated magnetic hydrothermal carbon of Ulva prolifera.

[0008] In some embodiments of the present invention, the seaweed powder is dried at 100-110°C and then pulverized through a 70-80 mesh sieve.

[0009] In this invention, the drying temperature of the seaweed powder can be 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃ or 110℃, etc., and the sieve mesh size of the seaweed powder can be 70 mesh, 71 mesh, 72 mesh, 73 mesh, 74 mesh, 75 mesh, 77 mesh, 78 mesh, 79 mesh or 80 mesh, etc., but is not limited to the values ​​listed above. Other values ​​not listed within the above range are also applicable.

[0010] In some embodiments of the present invention, the iron salt solution is a mixed solution of FeCl3·6H2O and FeSO4·7H2O, wherein the FeCl3·6H2O and FeSO4·7H2O mixed solution contains Fe 3+ with Fe 2+ The molar ratio is 2:1.

[0011] In some embodiments of the present invention, the conditions for the hydrothermal reaction are: temperature 170~190℃, time 3~5h, and heating rate 4~6℃ / min.

[0012] The hydrothermal reaction temperature can be 170℃, 171℃, 172℃, 173℃, 174℃, 175℃, 176℃, 177℃, 178℃, 179℃, 180℃, 181℃, 182℃, 183℃, 184℃, 185℃, 186℃, 187℃, 188℃, 189℃, or 190℃, etc., the hydrothermal reaction time can be 3h, 4h, or 5h, etc., and the heating rate can be 4℃ / min, 5℃ / min, or 6℃ / min, etc., but is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0013] In some embodiments of the present invention, after the hydrothermal reaction is completed, the hydrothermal carbon with a particle size of less than 120 mesh is washed, dried, and screened for phosphate activation.

[0014] In some embodiments of the present invention, the washing is performed using anhydrous ethanol and deionized water.

[0015] In some embodiments of the present invention, the drying temperature is 100~110℃ and the drying time is 5~10 h.

[0016] The drying temperature can be 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃ or 110℃, etc., and the drying time can be 5h, 6h, 7h, 8h, 9h or 10h, etc., but is not limited to the values ​​listed above. Other values ​​not listed within the above range are also applicable.

[0017] In some embodiments of the present invention, the phosphate solution is prepared by mixing K2HPO4 and KH2PO4 at a phosphate molar ratio of 1:1, the phosphate concentration in the solution is 0.05~0.15 mol / L, the mass-to-volume ratio of hydrothermal char to phosphate solution is 1:8~10 (g:mL), and the reaction of magnetic seaweed impregnated in phosphate solution by hydrothermal char is carried out by shaking at a speed of 140~160 rpm for 20~25 h at a reaction temperature of 25~30℃.

[0018] The phosphate concentration in the solution can be 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.10 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, or 0.15 mol / L, etc.; the mass-to-volume ratio of hydrothermal carbon to phosphate solution can be 1:8, 1:9, or 1:10, etc.; the heating rate can be 4℃ / min, 5℃ / min, or 6℃ / min, etc.; and the rotation speed can be 140 rpm / min, 141 rpm / min, 142 rpm / min, 14... The oscillation speeds can be 3 rpm, 144 rpm, 145 rpm, 146 rpm, 147 rpm, 148 rpm, 149 rpm, 150 rpm, 151 rpm, 152 rpm, 153 rpm, 154 rpm, 155 rpm, 156 rpm, 157 rpm, 158 rpm, 159 rpm, or 160 rpm, etc., and the oscillation time can be 20 h, 21 h, 22 h, 23 h, 24 h, or 25 h, etc., and the reaction temperature can be 25℃, 26℃, 27℃, 28℃, 29℃, or 30℃, but are not limited to the values ​​listed above. Other values ​​not listed within the above range are also applicable.

[0019] A second aspect of the present invention provides a method for promoting the enrichment of Clostridium and / or methanogenic bacteria in a dry digestion system of kitchen waste, wherein the above-mentioned modified Ulva hydrothermal char is added to the dry anaerobic digestion system of kitchen waste, and the concentration of the modified Ulva hydrothermal char is not higher than 60 mg / gTS.

[0020] In some embodiments of the present invention, the volume ratio of kitchen waste to inoculated sludge (TS) in the dry anaerobic digestion system is 1 to 4:1.

[0021] In some embodiments of the present invention, the concentration of modified Ulva hydrothermal carbon added is 0~60 mg / g, calculated as TS.

[0022] In some embodiments of the present invention, the pH in the anaerobic digestion system is 6 to 8.

[0023] In some embodiments of the present invention, the reaction temperature in the anaerobic digestion system is 25°C to 35°C.

[0024] In some embodiments of the present invention, the reaction cycle within the anaerobic digestion system is 30 days.

[0025] The volume ratio of kitchen waste to inoculated sludge (TS) can be 1:1, 2:1, 3:1, or 4:1, etc., and the concentration of modified Ulva hydrothermal charcoal can be 0 mg / g, 1 mg / g, 2 mg / g, 3 mg / g, 4 mg / g, 5 mg / g, 6 mg / g, 7 mg / g, 8 mg / g, 9 mg / g, 10 mg / g, 11 mg / g, 12 mg / g, 13 mg / g, or 14 mg / g. / g, 15mg / g, 16mg / g, 17mg / g, 18mg / g, 19mg / g, 20mg / g, 21mg / g, 22mg / g, 23mg / g, 24mg / g, 25mg / g, 26mg / g, 27mg / g, 28mg / g, 29mg / g, 30mg / g, 31mg / g, 32mg / g, 33mg / g, 34mg / g, 35m The anaerobic digestion system can have various concentrations of g / g, such as 36 mg / g, 37 mg / g, 38 mg / g, 39 mg / g, 40 mg / g, 41 mg / g, 42 mg / g, 43 mg / g, 44 mg / g, 45 mg / g, 46 mg / g, 47 mg / g, 48 mg / g, 49 mg / g, 50 mg / g, 51 mg / g, 52 mg / g, 53 mg / g, 54 mg / g, 55 mg / g, 56 mg / g, 57 mg / g, 58 mg / g, 59 mg / g, or 60 mg / g. The pH within the anaerobic digestion system can be 6, 7, or 8. The reaction temperature within the anaerobic digestion system can be 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, or 35℃, but is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0026] A third aspect of the present invention provides the application of the above-described modified Ulva hydrothermal char or the above-described method in biogas production, wherein the application is the addition of modified Ulva hydrothermal char at a concentration not exceeding 60 mg / g TS to an anaerobic digestion system for kitchen waste.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) This invention provides a modified hydrothermal charcoal from *Ulva prolifera* and its application in promoting the enrichment of *Clostridium perfringens* and / or *Bacillus methanogens* in a dry digestion system for kitchen waste. Hydrothermal charcoal possesses a well-developed pore structure, abundant functional groups, and good electrical conductivity, enabling it to effectively enrich functional microorganisms in anaerobic digestion systems. This invention improves the electrical conductivity of the hydrothermal charcoal by magnetizing it, thereby promoting interspecies electron transfer efficiency and enhancing microbial activity. Phosphate activation alleviates acid inhibition in anaerobic digestion systems, providing a favorable living environment for functional microorganisms.

[0029] (2) This invention optimizes the reaction conditions of the anaerobic digestion system by using phosphate-activated magnetic Ulva hydrothermal charcoal to enhance the enrichment of methanogenic archaea (methanogenic bag-shaped bacteria) in the dry anaerobic digestion system of kitchen waste, thereby optimizing the microbial community structure and promoting methane production. This is of great significance for increasing the biogas production from the dry digestion of kitchen waste. Attached Figure Description

[0030] Figure 1 SEM images of the unmodified hydrothermal char and phosphate-activated magnetic Ulva hydrothermal char prepared in the embodiments of the present invention;

[0031] Figure 2 XPS images of unmodified hydrothermal carbon and phosphate-activated magnetic Ulva hydrothermal carbon prepared in the embodiments of the present invention;

[0032] Figure 3 This refers to the alpha diversity of microorganisms at the genus level within the reactor in this embodiment of the invention.

[0033] Figure 4 This is a diagram showing the species richness at the bacterial and archaeal level within the reactor in this embodiment of the invention.

[0034] Figure 5 This is a species richness diagram at the bacterial and archaeal level within the reactor in an embodiment of the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0036] Example 1

[0037] The preparation process of phosphate-activated magnetic hydrothermal charcoal (P-MEPHC) of *Ulva prolifera* is as follows: Wet *Ulva prolifera* was dried at 105℃ for 12 h and then passed through an 80-mesh sieve. 15 g of dried *Ulva prolifera* powder was weighed and added to 135 mL of deionized water. The mixture was placed in a 300 mL reaction vessel and then transferred to a digital display constant temperature oven and heated at 180℃ for 4 h. After heating, the hydrothermal charcoal (EPHC) was removed from the reaction vessel and transferred to a large beaker. It was diluted with deionized water, and the diluted solution was transferred to a 50 mL centrifuge tube. The tube was centrifuged at 7000 rpm / min for 3 min, and the washing was repeated 5 times. Then, the EPHC was dried in a 105℃ drying oven to obtain EPHC.

[0038] Weigh out 4.38 g of FeCl3·6H2O and 2.25 g of FeSO4·7H2O to obtain nFe 3+ nFe 2+The MEPHC was completely dissolved in 135 ml of deionized water at a ratio of 2:1. 15 g of *Ulva prolifera* was added, and the mixture was stirred thoroughly for 1 h using a magnetic stirrer. The pH was adjusted to 11.0 using a prepared 10 mol / L NaOH solution, and the mixture was stirred until fully dissolved. The solution was transferred to a hydrothermal reactor and reacted at 180 °C for 4 h. After the reaction, the reactor was allowed to cool to room temperature. The MEPHC was then transferred to a large beaker and diluted with deionized water. The diluted solution was transferred to a 50 mL centrifuge tube and centrifuged at 7000 rpm for 3 min. The washing was repeated 5 times. The magnetic hydrothermal carbon was then dried in a 105 °C drying oven and separated using a magnet to obtain magnetic *Ulva prolifera* hydrothermal carbon (MEPHC).

[0039] Weigh 5.71 g of K₂HPO₄ (pH 7) and 3.40 g of KH₂PO₄, and dilute to volume in a 500 mL volumetric flask until the phosphate is completely dissolved to obtain the phosphate solution required for activating the hydrothermal carbon. Prepare a mixed solution by taking 20 g of MEPBC at a hydrothermal carbon (mass) to phosphate solution (volume) ratio of 1:9. Place the mixed solution in a constant temperature shaking oven at 150 rpm / min and shake for 24 h. Filter the supernatant and dry the hydrothermal carbon at 105 °C to obtain P-MEPHC.

[0040] Figure 1 SEM and XPS images of unmodified hydrothermal carbon (EPHC) and modified hydrothermal carbon (P-MEPHC) are presented. Figure 1 Comparison of microstructural changes in hydrothermal carbon and Figure 2 The changes in the XPS spectrum show that both iron salts and phosphates were loaded onto the hydrothermal carbon of Ulva prolifera, indicating that the hydrothermal carbon modification was successful.

[0041] Example 2

[0042] The main experimental setup included anaerobic digestion flasks (400 mL working volume), foil gas collection bags, and a constant-temperature shaking incubator. During the experiment, a 2 L foil gas collection bag was connected to a 500 mL anaerobic digestion flask. The experiment was conducted in three sets of anaerobic digestion reactors, each containing multiple digestion flasks. Different proportions of inoculum sludge and food waste were added to each anaerobic digestion flask, with a food waste:inoculum sludge (TS) volume ratio ranging from 1 to 4:1. Different amounts of P-MEPHC hydrothermal charcoal were added to each digestion flask, ranging from 0 to 60 mg / g TS. The initial pH of each digestion flask was adjusted using 2 mol / L NaOH or HCl solution, ranging from 6 to 8. After all materials were added, an anaerobic environment (ORP < -300 mV) was created by purging the headspace with high-purity nitrogen at 0.5 L / min for 60 s. All digestion flasks were sealed with butyl rubber stoppers and placed in a constant-temperature shaking incubator at 25–35°C and 150 rpm / min for 30 days of anaerobic digestion. Gas composition was monitored daily using gas chromatography (Agilent 7890B). Every 48 h, 5 mL of the mixture was collected, centrifuged (8000 × g, 10 min), and parameters such as VFAs and SCOD were analyzed. When the cumulative methane production showed no significant increase, 50 mL of digestion samples from each reactor were collected on day 30, frozen, and transported to Shanghai Meiji Biopharmaceutical Technology Co., Ltd. for metagenomic analysis.

[0043] Example 3

[0044] Three experimental groups were set up with initial substrate pH values ​​of 6.0, 7.0, and 8.0. The volume ratio of kitchen waste to inoculated sludge was set to 2:1. The dosage of P-MEPHC hydrothermal char was 0 mg / g TS. The temperature of the constant temperature shaking incubator was set to 25 ℃, and the rotation speed was set to 150 rpm / min. Anaerobic digestion experiments were conducted according to the steps in Example 2.

[0045] Microbiological analysis results showed that at pH=6.0, Clostridium spp. ( Sporanaerobacter The relative abundance of *Clostridium* spp. was 6.5% at pH 7.0; Sporanaerobacter The relative abundance of *Clostridium* spp. was 13.6%; at pH 8.0, the abundance of *Clostridium* spp. was... Sporanaerobacter The relative abundance of *Bacillus* was 10.3%. Meanwhile, *Bacillus* genus (*Bacillus*) had a higher abundance. Methanoculleus The relative abundance of *Clostridium* at pH 7 was 40.5%, significantly higher than that at pH 6 (22.1%) and pH 8 (31.3%). This indicates that at pH 7, the abundance of *Clostridium* spp. was significantly higher. Sporanaerobacter ) and Methanobacteria genus ( Methanoculleus The enrichment effect is best at ).

[0046] Example 4

[0047] Four experimental groups were set up with inoculated sludge to kitchen waste volume ratios of 1:1, 1:2, 1:3, and 1:4, with an initial pH of 7.0. The P-MEPHC hydrothermal char dosage was 0 mg / g TS. The temperature of the constant temperature shaking incubator was set to 25℃, and the rotation speed was set to 150 rpm / min. Anaerobic digestion experiments were conducted following the steps in Example 2.

[0048] Microbiological analysis results showed that when the volume ratio of inoculated sludge to kitchen waste was 1:1, Clostridium spp. ( Sporanaerobacter The relative abundance of *Clostridium* was 3.1%; when the volume ratio of inoculated sludge to kitchen waste was 1:2, the abundance of *Clostridium* spp. was 3.1%. Sporanaerobacter The relative abundance of *Clostridium* was 11.6%; when the volume ratio of inoculated sludge to kitchen waste was 1:3, the abundance of *Clostridium* spp. was 11.6%. Sporanaerobacter The relative abundance of Clostridium ( ) was 14.3%; when the volume ratio of inoculated sludge to kitchen waste was 1:4, the abundance of Clostridium ( ) was 14.3%; Sporanaerobacter The relative abundance of *Bacillus methanogens* was 13.3%. When the volume ratio of inoculated sludge to kitchen waste was 1:3, the abundance of *Bacillus methanogens* was [missing information]. Methanoculleus The enrichment effect was the best, with a relative abundance of 41.9%, which was 11.2% higher than that of Clostridium spp. when the volume ratio of inoculated sludge to kitchen waste was 1:1, 15.3% higher than that when the volume ratio was 1:2, and 9.2% higher than that when the volume ratio was 1:4. It can be seen that a volume ratio of 1:3 for inoculated sludge to kitchen waste significantly improved the enrichment of Clostridium spp. Sporanaerobacter ) and Methanobacteria genus ( Methanoculleus The enrichment effect is best at ).

[0049] Example 5

[0050] Three experimental groups were set up in a constant-temperature shaking incubator with temperatures of 25 ℃, 30 ℃, and 35 ℃, and an initial pH of 7.0. The volume ratio of inoculated sludge to kitchen waste was 1:3. The dosage of P-MEPHC hydrothermal charcoal was 0 mg / g TS. The rotation speed of the constant-temperature shaking incubator was set to 150 rpm / min. Anaerobic digestion experiments were conducted according to the steps in Example 2.

[0051] Microbiological analysis results showed that when the temperature was set to 30℃, Clostridium spp. ( Sporanaerobacter The enrichment effect of *Bacillus methanans* was the best, with a relative abundance of 14.8%, while the relative abundances at 25℃ and 35℃ were 6.3% and 7.1%, respectively. At 30℃, *Bacillus methanans* (*Bacillus* spp.) showed the best enrichment effect, with a relative abundance of 14.8%, while at 25℃ and 35℃, the relative abundances were 6.3% and MethanoculleusThe relative abundance of *Clostridium* reached 46.4%, but decreased at temperatures of 25℃ and 35℃, with relative abundances of 18.1% and 16.5%, respectively. This indicates that at 30℃, the relative abundance of *Clostridium* spp. was significantly higher. Sporanaerobacter ) and Methanobacteria genus ( Methanoculleus The enrichment effect is best at ).

[0052] Example 6

[0053] Six experimental groups were set up with P-MEPHC dosages of 0 mg / g TS (CK group), 13 mg / g TS, 26 mg / g TS, 39 mg / g TS, 52 mg / g TS, and 52 mg / g TS (MEPHC). The initial pH value was 7.0. The volume ratio of inoculum sludge to kitchen waste was 1:3. The temperature of the constant temperature shaking incubator was set to 30℃, and the rotation speed was set to 150 rpm / min. Anaerobic digestion experiments were carried out according to the steps in Example 2.

[0054] Biogas production analysis showed that, compared with the CK group's 65.91 mL / g TS (biogas production), the biogas production of the 52 mg / g TS P-MEPHC group increased to 99.25 mL / g TS, an increase of 50.6%.

[0055] Microbiological analysis results showed that when the P-MEPHC dosage was 0 mg / g TS (CK group), Clostridium spp. ( Sporanaerobacter The relative abundance of ) was 7.0%, and that of Methanobacteria ( ) Methanoculleus The relative abundance of *Clostridium* spp. reached 29.6%. When the P-MEPHC dosage was 13 mg / g TS, the abundance of *Clostridium* spp. (…) Sporanaerobacter The relative abundance of ) was 11.6%, and that of the genus *Methanobacteria* ( Methanoculleus The relative abundance of *Clostridium* reached 45.1%. When the P-MEPHC dosage was 26 mg / g TS, the abundance of *Clostridium* spp. (…) Sporanaerobacter The relative abundance of ) was 13.7%, and that of the genus *Methanobacteria* ( Methanoculleus The relative abundance of *Clostridium* spp. reached 45.1%. When the P-MEPHC dosage was 39 mg / g TS, the relative abundance of *Clostridium* spp. (…) was… Sporanaerobacter The relative abundance of ) was 13.9%, and that of the genus *Methanobacteria* ( Methanoculleus The relative abundance of *Clostridium* spp. reached 44.5%. When the P-MEPHC dosage was 52 mg / g TS, the relative abundance of *Clostridium* spp. was [missing information]. Sporanaerobacter The relative abundance of ) was 15.0%, and that of Methanobacteria ( ) Methanoculleus The relative abundance of Clostridium spp. reached 47.3%. When 52 mg / g TSMEPHC was added, Clostridium spp. ( SporanaerobacterThe relative abundance of ) was 14.6%, and that of the genus *Methanobacteria* ( Methanoculleus The relative abundance of ) reached 43.1%. It can be found that the addition of 52 mg / g TS P-MEPHC hydrothermal charcoal reduced the abundance of Clostridium spp. ( Sporanaerobacter ) and Methanobacteria genus ( Methanoculleus The enrichment effect is best at ).

[0056] Analysis of the anaerobic digestion system microbial community in the CK group and the 52 mg / g TS P-MEPHC group reactors

[0057] Figure 3 The study showed the genus-level alpha diversity of microorganisms in the digestive systems of the CK group and the 52 mg / g TS P-MEPHC group, with specific phylum-level and species-level microbial richness as follows: Figure 4 and Figure 5 .

[0058] Depend on Figure 3 The results showed that the Sobs and Shannon indices of the 52 mg / g TS P-MEPHC group were 4107 and 3.79, respectively, higher than those of the CK group (3352 and 2.97). The Simpson index of the P-MEHC group was 0.067, lower than that of the CK group (0.104), indicating that P-MEHC increased the microbial richness and diversity in the AD system. This reveals that the introduction of P-MEHC effectively optimized the microbial community distribution, resulting in a more balanced spatial distribution of microorganisms.

[0059] Depend on Figure 4Analysis of changes at the bacterial and archaeological levels revealed that Bacillota had an absolute advantage in the CK group, with its numbers far exceeding those of other phyla within the system. The 52 mg / g TS P-MEPBC group exhibited richer bacterial diversity; in addition to Bacillota, the numbers of Actinomycetota, Pseudomonadota, Planctomycetota, Thermodesulfobacteriota, and Bacteroidota were all increased. This corresponds to the lower Shannon index in the 52 mg / g TS P-MEPHC group compared to the control group. Bacillus is considered an important organic matter-utilizing bacterium, capable of converting macromolecular organic matter into short-chain fatty acids (SCFAs), providing metabolic raw materials for methanogens. Its thick cell wall also allows it to survive in extreme environments, which explains why organic matter in the control group was converted to SCFAs more quickly, increasing the risk of acidification. In the P-MEPHC group, the introduction of P-MEPHC optimized the microbial community structure and enhanced synergistic metabolic functions among the bacterial groups, thereby optimizing the system's organic matter degradation efficiency and methane production. In the 52 mg / g TS P-MEPHC group, the abundance of Euryarchaeota (4066) was significantly higher than that in the control group (480), an increase of approximately 10-fold. This indicates that hydrothermal carbon significantly enriched methanogenic bacteria by optimizing substrate supply (such as H2 / CO2 and acetic acid) and conductivity-mediated electron transfer. In addition, except for Euryarchaeota, the abundance of the top ten archaea in the P-MEPHC group was increased compared to the control group. This reflects that the porous structure of hydrothermal carbon provides ecological niches for functional bacterial communities, increases the abundance of dominant species, and enhances community stability and metabolic complementarity.

[0060] Depend on Figure 5 (Analysis of changes at the bacterial and archaeal levels) revealed that in the 52 mg / g TS P-MEPHC group, under the influence of the porous adsorption and conductivity of hydrothermal carbon, Clostridium species ( ) were associated with the hydrolysis and acidification stage. Sporanaerobacter The relative abundance of ) increased from 7.0% in the CK group to 15.0%. SporanaerobacterThe enrichment of methanogens can be achieved by using 52 mg / g TS P-MEPHC as an electron acceptor to link with methanogens, thereby improving interspecies electron transfer efficiency and promoting the conversion of polysaccharides, fats, and proteins into volatile short-chain fatty acids (VFAs), providing sufficient substrates (such as acetic acid and H2 / CO2) for subsequent methanogenesis. Simultaneously, the *Leuconostoc* spp. in the 52 mg / g TS P-MEPHC group... Leuconostoc The relative abundance of these bacteria increased by 9.74%. These bacteria can influence the isolatory fermentation of carbohydrates, converting pyruvate into ethanol. Ethanol can act as a substrate to drive the conversion between NAD⁺ and NADH, promoting intracellular electron transport. The core role of hydrothermal char lies in its ability to alleviate acid inhibition through physical adsorption, promote intermediate electron transport (DIET), and act as a carrier of functional microbial communities, systematically optimizing the metabolic chain of "hydrolysis-acidification-methanogenesis" and increasing biogas production. The 52 mg / g TS P-MEPHC group contained *Methanobacteria* spp. Methanoculleus The percentage of the control group (47.3%) was significantly higher than that of the control group (29.6%), an increase of approximately 17.7%. Methanoculleus It is a typical hydrogenotrophic microorganism with strong acid resistance, capable of growing and developing under low pH conditions. This allows it to effectively carry out methanogenesis even at high VFA concentrations. Hydrothermal carbon enhances the growth of hydrolytic bacteria (such as...) by creating a favorable microenvironment. Clostridium The method enhances the hydrogen production capacity of the anaerobic digester and accelerates H2 transfer by utilizing the conductivity of magnetic materials, significantly improving the efficiency of the hydrogen-nutritive methanogenesis pathway and promoting the methanogenesis efficiency of the anaerobic digester.

[0061] In summary, microbial community structure analysis showed that P-MEPHC enhanced microbial richness and diversity, and selectively enriched Clostridium spp. ( Sporanaerobacter ) and Methanobacteria genus ( Methanoculleus Functional microorganisms such as [unspecified microorganisms] promote the transformation of organic matter and increase biogas production.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0063] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Although the specific embodiments of the present invention have been described above, they are not intended to limit the protection scope of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for promoting the enrichment of Clostridium and / or Clostridium methanogens in a dry digestion system of kitchen waste, characterized in that, Modified Ulva hydrothermal char was added to the dry anaerobic digestion system for kitchen waste. The concentration of phosphate-activated magnetic Ulva hydrothermal char, calculated as TS, was not higher than 60 mg / g. The modified seaweed hydrothermal carbon is phosphate-activated magnetic seaweed hydrothermal carbon. Its preparation method includes: impregnating seaweed powder in an iron salt solution, then carrying out a hydrothermal reaction to obtain magnetic seaweed hydrothermal carbon, then impregnating the magnetic seaweed hydrothermal carbon in a phosphate solution for reaction, taking it out, washing and drying it to obtain phosphate-activated magnetic seaweed hydrothermal carbon. The iron salt solution is a mixed solution of FeCl3·6H2O and FeSO4·7H2O; The FeCl3·6H2O and FeSO4·7H2O mixed solution contains Fe 3+ with Fe 2+ The molar ratio is 2:1; The temperature of the hydrothermal reaction is 170~190℃.

2. The method for promoting the enrichment of Clostridium and / or Clostridium methanogens in the dry digestion system of kitchen waste as described in claim 1, characterized in that, The particle size of the seaweed powder is 70-80 mesh.

3. The method for promoting the enrichment of Clostridium and / or Methanobacterium in a dry digestion system of kitchen waste as described in claim 1, characterized in that, The conditions for the hydrothermal reaction are: time 3~5 h, heating rate 4~6℃ / min.

4. The method for promoting the enrichment of Clostridium and / or Methanobacterium in a dry digestion system of kitchen waste as described in claim 1, characterized in that, The magnetic seaweed hydrothermal char has a particle size of 100-140 mesh.

5. The method for promoting the enrichment of Clostridium and / or Methanobacterium in a dry digestion system for kitchen waste as described in claim 1, characterized in that, The phosphate solution is prepared by mixing K2HPO4 and KH2PO4 in a phosphate molar ratio of 1:1, and the phosphate concentration in the solution is 0.05~0.15 mol / L.

6. The method for promoting the enrichment of Clostridium and / or Methanobacteria in a dry digestion system of kitchen waste as described in claim 1, characterized in that, The mass-to-volume ratio of the magnetic seaweed hydrothermal charcoal to the phosphate solution is 1g:8-10ml.

7. The method for promoting the enrichment of Clostridium and / or Clostridium methanogens in a dry digestion system of kitchen waste as described in claim 1, characterized in that, The hydrothermal carbon impregnation of magnetic seaweed in phosphate solution was carried out by shaking at 140-160 rpm for 20-25 h at a reaction temperature of 25-30℃.

8. The application of the method for promoting the enrichment of Clostridium and / or Methanobacterium in the dry digestion system of kitchen waste according to any one of claims 1-7 in the production of biogas.

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