Method for improving methane yield by treating livestock manure with peracetic acid-biochar

Abstract

The invention discloses a method for improving methane yield by treating livestock manure with peracetic acid-biochar. The method comprises the following steps: S1, peracetic acid-biochar treatment; S2, anaerobic fermentation treatment; through the synergistic effect of PAA and biochar, a three-dimensional path of'oxidation release + ammonia nitrogen adsorption + electronic boosting 'is constructed for the first time, on one hand, the excrement structure is broken to release organic matters, on the other hand, direct interspecific electron transfer is promoted by using functional groups on the surface of biochar, meanwhile, ammonia nitrogen is adsorbed to relieve the inhibition effect, and the methane production efficiency and the system stability are remarkably improved; compared with a control group, the gas production rate is increased by 30% or above, and efficient technical support is provided for rural manure energy utilization.

Description

Technical Field

[0001] This invention relates to the field of methane production technology, specifically to a method for increasing methane production by treating livestock manure with peracetic acid-biochar. Background Technology

[0002] Methane can serve as a clean and renewable energy source to replace some traditional fossil fuels, being used for power generation, heating, and even conversion into biogas, helping to alleviate energy shortages in rural areas. However, in practical engineering operations, livestock and poultry manure often presents challenges to anaerobic systems due to its high solids content, high ammonia nitrogen concentration, and low carbon-to-nitrogen ratio, resulting in low substrate utilization, slow gas production rates, and system instability. Organic matter in manure is often encapsulated in extracellular polymers or cell structures, making release difficult; high concentrations of ammonia nitrogen inhibit methanogenic bacteria activity; furthermore, traditional electron transfer pathways rely on coenzyme transport, which has low efficiency and limits electron flow to the methanogenic reaction. Therefore, there is an urgent need to construct a highly efficient synergistic pathway that can simultaneously address "organic matter dissolution, toxicity mitigation, and electron enhancement," improving anaerobic methanogenesis performance across the entire chain from source to gas production.

[0003] In recent years, related research has attempted to increase methane production from sewage using methods such as chemical oxidation, thermal hydrolysis, nano-additives, and biochar enhancement. Some of these methods, similar in concept to this invention, include:

[0004] Patent ①CN202210897791.7: Introducing antiviral drugs to replace traditional conditioners, and increasing methane production by regulating microbial metabolic pathways under appropriate addition conditions, a new strategy of "drug + sludge co-fermentation" is proposed, which has certain innovation and resource reuse significance; however, there are problems such as high drug cost, limited source and insufficient environmental risk assessment.

[0005] Patent ② CN202211310417.9 proposes a method to enhance sludge methanogenesis using a synergistic regulation of citric acid and zero-valent iron, which improves substrate degradability and microbial activity. However, the process requires precise control of pH and dosage ratio, making scale-up applications difficult, and the economics of citric acid consumption have not been fully assessed. Some literature has attempted to treat sludge with PAA alone, showing some release effect, but has not deeply integrated electron transport and ammonia nitrogen mitigation. In summary, existing methods mostly focus on single aspects such as "cell wall disruption" or "stability," lacking a systematic synergistic strategy to address the "dissolution-inhibition-mitigation-electron transport" process. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for treating poultry and livestock manure with peracetic acid-biochar to increase methane production.

[0007] The technical solution of this invention is: a method for increasing methane production by treating poultry and livestock manure with peracetic acid-biochar, characterized by comprising the following steps:

[0008] S1, Peracetic acid-biochar treatment

[0009] Peracetic acid at a dosage of 10-20 mg / g TSS and biochar at a dosage of 0.5-2.0 g / g VSS were added to poultry and livestock manure, and then the mixture was treated in a constant temperature shaker at 30-35℃ and 120 rpm for 10-14 hours until it was evenly mixed to obtain poultry and livestock manure treated with peracetic acid-biochar.

[0010] S2, Anaerobic fermentation treatment

[0011] Add inoculated sludge to the peracetic acid-biochar treated poultry and livestock manure at a volume ratio of 1:1-2 (VSS of peracetic acid-biochar treated poultry and livestock manure to VSS of inoculated sludge). Adjust the pH to 6.8-7.2, then purge with nitrogen to maintain an anaerobic environment. Seal the container and place it in a constant temperature shaking incubator. Shake and culture at 30-35℃ and 110-130 rpm for 10-12 hours, then allow it to ferment statically for 0-30 days.

[0012] Explanation: PAA is used as the oxidant primarily because of its strong oxidizing power while maintaining a milder and more controllable reaction. PAA's oxidation potential is 1.81V, slightly higher than H2O2 (1.78V), sufficient to disrupt cell membranes, lyse extracellular polymeric substances (EPS), and kill microorganisms. Compared to ozone (2.07V), PAA's reaction rate is slightly slower, the oxidation process is milder, and it does not excessively damage the biodegradability of the substrate, making it more conducive to subsequent anaerobic digestion. It produces no toxic byproducts; the decomposition products are acetic acid, oxygen, and water, making it relatively safe for the environment and microorganisms. Simultaneously possessing both disinfection and oxidation functions, PAA is a highly efficient bactericide that can rapidly inactivate bacteria, viruses, and spores. In sludge / fecal waste systems, it not only lyses cell structures but also reduces pathogen risk, offering better disinfection capabilities compared to H2O2 or PMS.

[0013] The advantages of using livestock and poultry manure as a substrate are its large quantity and concentration. Compared with agricultural waste such as straw, livestock and poultry manure is usually collected centrally at farms, resulting in lower raw material acquisition and transportation costs. It is rich in organic matter, with a higher organic loading rate than municipal sludge, which can provide greater methane production. It is also nutrient-rich, containing abundant nitrogen, phosphorus, potassium, and other nutrients, which can provide the necessary nutrition for microorganisms in the anaerobic digestion system. Furthermore, it has good degradability, enabling both high-efficiency production and pollution reduction through recycling. Therefore, it is one of the most representative and practically valuable substrates for anaerobic digestion.

[0014] Furthermore, in S1, the addition method is as follows: first, biochar is added to the poultry and livestock manure, and then peracetic acid is added to the poultry and livestock manure containing biochar.

[0015] Explanation: By adding biochar first and then peracetic acid, the adsorption effect of biochar on peracetic acid can be utilized, allowing the peracetic acid to be released slowly and for a longer period of time, thereby further increasing the production of methane.

[0016] Furthermore, in S1, the preparation steps of the biochar are as follows:

[0017] (1) Cut rice husks and straw into small pieces, treat them with hydrothermal heat at 150-200℃ for 20-30 minutes, wash them with water and air dry them for 3-4 days. Then dry them in an electric heating oven at 100-105℃ for 24-48 hours. Next, place them in a quartz box and put the quartz box in a vacuum tube furnace. Then pyrolyze the straw pieces in an anaerobic environment. Finally, grind the pyrolyzed straw biochar in a mortar and pass it through a 100-140 mesh sieve. The biochar passed through the sieve is the biochar used in the experiment.

[0018] (2) The biochar is mixed with a 1-3M sodium hydroxide solution at a mass ratio of 1:8-10. After stirring evenly, the mixture is reacted at 80-90℃ for 2-3 hours. After the reaction is completed, the biochar is washed with deionized water 3-5 times until the washing solution is neutral. Then it is dried at 100-105℃ for 10-12 hours to obtain modified biochar.

[0019] (3) The modified biochar was impregnated in 1-butyl-3-methylimidazolium hydrogen sulfate, stirred evenly, and then allowed to stand at room temperature for 22-24 hours; the mass ratio of the modified biochar to 1-butyl-3-methylimidazolium hydrogen sulfate was 1:1-5.

[0020] Note: Coexisting ions in fecal waste (such as Cl) - SO4 2- Humic acid and peracetic acid compete for the same reaction, reducing the efficiency of organic matter degradation and thus affecting the substrate supply for methane production; 1-butyl-3-methylimidazolium hydrogen sulfate has good adsorption properties and can effectively adsorb Cl from manure. - SO4 2- It combines with humic acid to reduce the competitive reaction between these substances and peracetic acid, thereby improving the degradation efficiency of organic matter.

[0021] Furthermore, the rice husk and straw fragments are 3-5 cm in length and have a surface area of ​​<15 cm². 2 ;

[0022] Note: The above limitation of straw fragments can reduce the temperature gradient difference of pyrolysis, avoid uneven local carbonization caused by excessively small fragment length, and the limitation of surface area can stabilize the heating rate, thereby improving the pyrolysis efficiency.

[0023] Further, in (1), the method of anaerobic pyrolysis is as follows: nitrogen gas is continuously introduced into the vacuum tube at a flow rate of 0.3-0.5 L / min for 10-15 min, and then heated to 550-600℃ at a heating rate of 8-10℃ / min under anaerobic conditions, and held for 1.5-2 h for pyrolysis.

[0024] Note: The above nitrogen flow rate can effectively suppress back mixing of pyrolysis gas, and the limited heating rate can avoid excessive temperature fluctuations. The isothermal pyrolysis treatment at 550-600℃ for 1.5-2 hours can achieve a decomposition rate of dioxin precursors (such as chlorobenzene) of >99.9%, meeting environmental emission requirements.

[0025] Furthermore, in S2, during the static fermentation process, the feed is added in batches, and the stirring speed is reduced to 70-80 rpm during feeding; the method of batch feeding is as follows:

[0026] When the temperature is ≤33℃ and the pH value is <6.5, during the anaerobic fermentation treatment cycle, add 3-4wt% of the fermentation liquid to the fermentation liquid every day to replenish the organic waste after biochar treatment.

[0027] When the temperature is >33℃ and the volatile fatty acid (VFA) is >2000mg / L, the fermentation broth is centrifuged every 2-3 days during the anaerobic fermentation process. After removing the supernatant, the precipitate is resuspended with 200-400mL of deoxygenated water. Then, the organic waste treated with biochar is added in cycles at 3-4wt%, 4-5wt%, and 5-6wt% of the fermentation broth.

[0028] Note: Batch feeding provides a continuous substrate supply, avoiding substrate overload caused by adding a large amount of substrate at once, thereby improving system stability and methane production. At low temperatures, microbial metabolism is slower, and the fermentation process is less active. In this case, direct feeding can provide more substrate to sustain fermentation. A pH below 6.5 indicates a high accumulation of acidic substances in the fermentation broth, which may inhibit the activity of methanogens. In this situation, direct feeding can provide more substrate, promote microbial metabolism, and help regulate the pH.

[0029] While peracetic acid pretreatment can decompose some organic matter, the remaining recalcitrant macromolecules may hinder the metabolism of methanogens. At higher temperatures, microbial metabolism is faster, and the fermentation process is more active. Under these conditions, volatile fatty acids (VFAs) accumulate in the fermentation broth, which inhibits methanogen activity. A VFA concentration exceeding 2000 mg / L indicates a significant accumulation of acidic substances in the fermentation broth, which may further suppress methanogen activity. In such cases, centrifugation can remove the supernatant from the fermentation broth, reducing VFA accumulation and mitigating the inhibitory effect on methanogens. Adding deoxygenated water after centrifugation maintains osmotic pressure balance, enhancing methanogen activity. This step, in conjunction with a co-buffered buffer, increases the methane content. To address the issues of low efficiency and limited methane production in anaerobic fermentation under low-temperature conditions, which necessitate additional energy input to maintain suitable temperatures, this application utilizes the porous structure of biochar to adsorb methanogenic bacteria and reduce heat loss, enabling the reaction system to maintain suitable temperature-equivalent metabolic activity at low temperatures. Simultaneously, the phosphate-carbonate buffer system forms a thermostable enzyme complex after pretreatment, thereby improving enzyme activity retention at low temperatures.

[0030] Mesophilic methanogens (such as Methanosarcina) exhibit a decreased metabolic rate below 33°C, and direct feeding avoids cell loss caused by centrifugation. When pH < 6.5, volatile fatty acids (VFAs) accumulate in the fermentation broth; direct feeding alleviates acidification through dilution. High-temperature, high-VFA centrifugation feeding is used because centrifugation effectively retains VFAs (removal rate > 40%), preventing their inhibition of methanogens (methane yield decreases by 30% when VFA > 2000 mg / L); deoxygenated water resuspension reduces the damage of oxidizing substances to the functional groups on the biochar surface.

[0031] Furthermore, the parameters for centrifuging the fermentation broth are: centrifugation speed of 5000-6000 rpm and centrifugation time of 12-15 min;

[0032] Note: The above centrifugation parameters can effectively separate bacterial cells from the supernatant, with a high bacterial cell recovery rate, while avoiding damage to biochar particles due to excessive rotation speed. A process time shorter than 12 minutes may result in incomplete separation, while a process time longer than 15 minutes will increase the processing time and reduce equipment turnover.

[0033] Furthermore, in S2, the nitrogen gas is introduced at a rate of 40-100 mL / min for a duration of 2-4 min.

[0034] Note: The above nitrogen flow rate can replace more than 90% of the oxygen in the reactor within 2-4 minutes, meeting strict anaerobic conditions (dissolved oxygen < 0.2 mg / L) and avoiding inhibition of methanogenic bacteria activity; short-term nitrogen flow can avoid cell damage caused by prolonged aeration (such as increased survival rate of Bifidobacteria). In anaerobic fermentation, VFA accumulation is reduced under nitrogen protection, and methane yield is increased; it is suitable for batch feeding processes (such as nitrogen flow before feeding in S3), and works in conjunction with stirring speed to avoid bubble interference.

[0035] PAA exerts its strong oxidizing effect through the free radical pathway. The free radical pathway refers to PAA's oxidizing capacity by generating free radicals such as ·OH, O2·-, and RO· (CH3C(O)O·, CH3C(O)OO·, CH3OO·, CH3·). The active free radicals generated by PAA can effectively disrupt the EPS structure and microbial cell walls of livestock and poultry manure, promoting the lysis of livestock and poultry manure flocs and thus releasing organic matter from the solid phase of the manure. Combined pretreatment reduces PAA decomposition losses through the adsorption and slow release of PAA by biochar, thereby generating more active free radicals and enhancing its oxidative and cell-wall-breaking capabilities.

[0036] The PAA oxidation process may involve the following reactions

[0037] CH3C(O)OOH→CH3C(O)O·+HO·

[0038] CH3C(O)O·→CH3·+CO2

[0039] CH3C(O)O·+CH3C(O)O·→(CH3C(O)O)2

[0040] CH3·+O2→CH3OO·

[0041] CH3C(O)OOH+HO·→CH3C(O)OO·+H2O

[0042] CH3C(O)OOH+CH3C(O)O·→CH3C(O)OO·+CH3C(O)OH

[0043] CH3C(O)OO·→CH2CO+O2 ·- +H +

[0044] CH3C(O)O·+H2O2→O 2·- +CH3C(O)OOH+H +

[0045] The beneficial effects of this invention are:

[0046] (1) This invention constructs a three-dimensional pathway of “oxidation release + ammonia nitrogen adsorption + electron boosting” for the first time by synergistically combining PAA and biochar. On the one hand, it breaks down the structure of manure to release organic matter, and on the other hand, it uses the functional groups on the surface of biochar to promote direct interspecies electron transfer. At the same time, it adsorbs ammonia nitrogen to alleviate the inhibition effect, significantly improving the efficiency of methanogenesis and the stability of the system. The gas production is increased by more than 30% compared with the control group, providing efficient technical support for the energy utilization of rural manure.

[0047] (2) This invention utilizes functionalized biochar, formed by hydrothermal treatment and anaerobic pyrolysis of rice husk straw to create biochar with a high specific surface area (>800 m²). 2 / g) biochar, with a 3-fold increase in VFA adsorption capacity; NaOH treatment introduces carboxyl and phenolic hydroxyl groups, enhancing adsorption of heavy metals (such as Cu). 2+ Zn 2+ The chelating ability of 1-butyl-3-methylimidazolium hydrogen sulfate is enhanced to reduce toxicity; 1-butyl-3-methylimidazolium hydrogen sulfate is loaded on the surface of biochar to form an electron transport channel, promoting the electron transfer efficiency of methanogens; combined with alkali activation and ionic liquid modification, the biochar adsorbs VFAs (such as acetic acid and propionic acid), avoiding a sudden drop in pH; at the same time, 1-butyl-3-methylimidazolium hydrogen sulfate provides an electron mediator to accelerate interspecies electron transfer; it chelates heavy metals, protects the integrity of the microbial membrane, and optimizes the reusability of biochar.

[0048] (3) This invention provides a continuous substrate supply by feeding the substrate in batches during anaerobic digestion, avoiding substrate overload caused by adding a large amount of substrate at once, thereby improving system stability and methane production. At low temperatures, the metabolic rate of microorganisms is slower; batch feeding better adapts to the metabolic rate of microorganisms, ensuring that they can fully utilize the substrate at each stage. Although peracetic acid pretreatment can decompose some organic matter, residual recalcitrant macromolecules may hinder the metabolism of methanogens. At higher temperatures, centrifugation effectively removes residual lignin from peracetic acid pretreatment (removal rate >60%), reducing its electron transport blocking effect on methanogens. Adding deoxygenated water after centrifugation maintains osmotic pressure balance, enhancing methanogen activity. This step, in conjunction with the co-buffer, increases the methane content. Attached Figure Description

[0049] Figure 1 This is a comparison of the cumulative methane production of livestock and poultry manure under different pretreatment methods;

[0050] Figure 2 It is a comparison of the particle size distribution of livestock and poultry manure under different pretreatment methods;

[0051] Figure 3 This is a comparison chart of VSS reduction and percentage reduction after 28 days of anaerobic digestion of livestock and poultry manure under different pretreatment methods. Detailed Implementation

[0052] The present invention will now be described in more detail with reference to specific embodiments, so as to better demonstrate the advantages of the present invention.

[0053] TSS (Total Suspended Solids) refers to the total amount of solid matter suspended in water, including inorganic and organic particles. A peracetic acid dosage of "15 mg / g TSS" indicates that 15 mg of peracetic acid is needed per gram of fecal waste for disinfection or oxidative degradation of organic matter.

[0054] VSS (volatile suspended solids) refers to the volatile organic components in suspended solids (SS), reflecting the content of degradable organic matter in fecal waste. "1.2g / g VSS" means that 1.2g of biochar needs to be added for every gram of volatile suspended solids in fecal waste to optimize the degradation or adsorption of organic matter.

[0055] Example 1: A method for increasing methane production by treating poultry and livestock manure with peracetic acid-biochar, comprising the following steps:

[0056] S1, Peracetic acid-biochar treatment

[0057] Peracetic acid was added to livestock manure at a dosage of 15 mg / g TSS and biochar at a dosage of 1.2 g / g VSS. The mixture was then treated in a constant temperature shaker at 33°C and 120 rpm for 12 hours until homogeneous, resulting in livestock manure treated with peracetic acid and biochar. In S1, the addition method was as follows: biochar was added to the livestock manure first, and then peracetic acid was added to the livestock manure containing biochar.

[0058] In S2, the preparation steps of biochar are as follows:

[0059] (1) Cut the rice husks and straw into pieces with a length of 4cm and a surface area of ​​15cm². 2 The straw fragments were hydrothermally treated at 175℃ for 25 minutes, washed with water, and air-dried naturally for 3 days. Then, they were dried in an electric heating oven at 103℃ for 36 hours. Next, they were placed in a quartz box and placed in a vacuum tube furnace for anaerobic pyrolysis. Finally, the straw biochar obtained from the pyrolysis was ground in a mortar and passed through a 100-140 mesh sieve to obtain the biochar used in the experiment.

[0060] The method of anaerobic pyrolysis is as follows: nitrogen gas is continuously introduced into the vacuum tube furnace at a flow rate of 0.4 L / min for 13 min, and then heated to 575 °C at a heating rate of 9 °C / min under anaerobic conditions, and held for 1.8 h for pyrolysis.

[0061] (2) The biochar was mixed with a 2M sodium hydroxide solution at a mass ratio of 1:9. After stirring evenly, the mixture was reacted at 85℃ for 2.5h. After the reaction was completed, the biochar was washed with deionized water 4 times until the washing solution was neutral. Then it was dried at 103℃ for 11h to obtain modified biochar.

[0062] (3) The modified biochar was impregnated in 1-butyl-3-methylimidazolium hydrogen sulfate, stirred evenly, and then allowed to stand at room temperature for 23 hours; the mass ratio of modified biochar to 1-butyl-3-methylimidazolium hydrogen sulfate was 1:3.

[0063] S3, Anaerobic fermentation treatment

[0064] The inoculum sludge (obtained from an anaerobic digester at a sludge treatment plant in Tianjin) was added to the peracetic acid-biochar treated poultry and livestock manure with a volume ratio of VSS to VSS of inoculated sludge of 1:1.5. The pH was adjusted to 7.0, and nitrogen gas was introduced to maintain an anaerobic environment. The mixture was sealed and placed in a constant temperature shaking incubator. It was shaken and cultured at 33°C and 120 rpm for 10-12 hours, and then allowed to ferment statically for 28 days. The nitrogen gas introduction rate was 60 mL / min and the introduction time was 3 min.

[0065] Example 2: Unlike Example 1, in S1, peracetic acid was added to poultry and livestock manure at a dosage of 10 mg / g TSS and biochar at a dosage of 0.5 g / g VSS.

[0066] Example 3: Unlike Example 1, in S1, peracetic acid was added to poultry and livestock manure at a dosage of 20 mg / g TSS and biochar at a dosage of 2.0 g / g VSS.

[0067] Example 4: Unlike Example 1, in S1, the poultry and livestock manure was treated for 10 hours at 30°C and 120 rpm until it was evenly mixed, resulting in peracetic acid-biochar treated manure.

[0068] Example 5: Unlike Example 1, in S1, the poultry and livestock manure was treated for 14 hours at a constant temperature shaker at 35°C and 120 rpm until it was mixed evenly, to obtain poultry and livestock manure treated with peracetic acid-biochar.

[0069] Example 6: Unlike Example 1, in S1, the preparation steps of biochar are as follows: (1) Rice husk straw is cut into pieces with a length of 3cm and a surface area of ​​10cm². 2The straw fragments were hydrothermally treated at 150℃ for 20 minutes, washed with water and air-dried naturally for 3 days. Then they were dried in an electric heating oven at 100℃ for 24 hours. Next, they were placed in a quartz box and placed in a vacuum tube furnace for anaerobic pyrolysis to burn the straw fragments.

[0070] Example 7: Unlike Example 1, in S1, the preparation steps of biochar are as follows: (1) Rice husk straw is cut into pieces with a length of 5cm and a surface area of ​​15cm². 2 The straw fragments were hydrothermally treated at 200℃ for 30 minutes, washed with water and air-dried naturally for 4 days. Then they were dried in an electric heating oven at 105℃ for 48 hours. Next, they were placed in a quartz box and placed in a vacuum tube furnace for anaerobic pyrolysis to burn the straw fragments.

[0071] Example 8: Unlike Example 1, in S1, the method of anaerobic pyrolysis is as follows: nitrogen gas is continuously introduced into the vacuum tube at a flow rate of 0.3 L / min for 10 min, and then heated to 550°C at a heating rate of 8°C / min under anaerobic conditions, and held for 1.5 h for pyrolysis.

[0072] Example 9: Unlike Example 1, in S1, the method of anaerobic pyrolysis is as follows: nitrogen gas is continuously introduced into the vacuum tube at a flow rate of 0.5 L / min for 15 min, and then heated to 600°C at a heating rate of 10°C / min under anaerobic conditions, and held for 2 h for pyrolysis.

[0073] Example 10: Unlike Example 1, in S1, (2) biochar and sodium hydroxide solution with a concentration of 1M are mixed at a mass ratio of 1:8, stirred evenly, and reacted at 80°C for 2 hours. After the reaction is completed, the biochar is washed with deionized water 3 times until the washing liquid is neutral, and then dried at 100°C for 10 hours to obtain modified biochar.

[0074] Example 11: Unlike Example 1, in S1, (2) biochar and sodium hydroxide solution with a concentration of 3M are mixed at a mass ratio of 1:10, stirred evenly, and reacted at 90°C for 3 hours. After the reaction is completed, the biochar is washed with deionized water 5 times until the washing liquid is neutral, and then dried at 105°C for 12 hours to obtain modified biochar.

[0075] Example 12: Unlike Example 1, in S1, (3) the modified biochar was impregnated in 1-butyl-3-methylimidazolium hydrogen sulfate, stirred evenly and then left to stand at room temperature for 22 hours; the mass ratio of modified biochar to 1-butyl-3-methylimidazolium hydrogen sulfate was 1:1.

[0076] Example 13: Unlike Example 1, in S1, (3) the modified biochar was impregnated in 1-butyl-3-methylimidazolium hydrogen sulfate, stirred evenly and then left to stand at room temperature for 24 hours; the mass ratio of modified biochar to 1-butyl-3-methylimidazolium hydrogen sulfate was 1:5.

[0077] Example 14: Unlike Example 1, in S2, inoculated sludge was added to the peracetic acid-biochar treated poultry and livestock manure VSS at a volume ratio of 1:1 to inoculated sludge VSS. The pH was adjusted to 6.8, and nitrogen gas was introduced to maintain an anaerobic environment. The mixture was sealed and placed in a constant temperature shaking incubator. It was shaken and cultured at 30°C and 110 rpm for 10 hours, and then allowed to ferment statically for 5 days. The nitrogen gas introduction rate was 40 mL / min and the introduction time was 2 min.

[0078] Example 15: Unlike Example 1, in S2, inoculated sludge was added to the peracetic acid-biochar treated poultry and livestock manure VSS at a volume ratio of 1:2 to inoculated sludge VSS. The pH was adjusted to 7.2, and nitrogen gas was introduced to maintain an anaerobic environment. The mixture was sealed and placed in a constant temperature shaking incubator. It was shaken and cultured at 35°C and 130 rpm for 12 hours, and then allowed to ferment statically for 30 days. The nitrogen gas introduction rate was 100 mL / min and the introduction time was 4 min.

[0079] Example 16: Unlike Example 1, in S2, the material is fed in batches during the static fermentation process, and the stirring speed is reduced to 75 rpm during feeding.

[0080] The method for batch replenishment is as follows:

[0081] When the temperature is ≤33℃ and the pH value is <6.5, during the anaerobic fermentation process, organic waste treated with biochar, accounting for 3wt% of the fermentation liquid, is added to the fermentation liquid every other day for replenishment.

[0082] When the temperature is >33℃ and the volatile fatty acid (VFA) is >2000mg / L, during the anaerobic fermentation process, the fermentation broth is centrifuged at 5500rpm for 14min every 2-3 days. After removing the supernatant, the precipitate is resuspended in 300mL of deoxygenated water. Then, the organic waste treated with biochar is added in cycles at 3wt%, 4wt%, and 5wt% of the fermentation broth.

[0083] Example 17: Unlike Example 16, in S2, the material was fed in batches during the static fermentation process, and the stirring speed was reduced to 70 rpm during feeding.

[0084] Example 18: Unlike Example 16, in S2, the material was fed in batches during the static fermentation process, and the stirring speed was reduced to 80 rpm during feeding.

[0085] Example 19: Unlike Example 16, the batch feeding method is as follows:

[0086] When the temperature is ≤33℃ and the pH value is <6.5, add 3wt% of the biochar-treated organic waste to the fermentation liquid every other day on the 1st, 3rd, 5th and 7th days of the anaerobic fermentation cycle.

[0087] When the temperature is >33℃ and the volatile fatty acid (VFA) is >2000 mg / L, during the anaerobic fermentation process, on the 2nd, 4th, 6th, ... every 2 days, the fermentation broth is centrifuged at 5000 rpm for 12 min. After removing the supernatant, the precipitate is resuspended with 200 mL of deoxygenated water. Then, the organic waste treated with biochar is added in cycles at 3 wt%, 4 wt%, and 5 wt% of the fermentation broth.

[0088] Example 20: Unlike Example 16, the batch feeding method is as follows:

[0089] When the temperature is ≤33℃ and the pH value is <6.5, add 4wt% of the biochar-treated organic waste to the fermentation liquid every other day on the 1st, 3rd, 5th and 7th days of the anaerobic fermentation cycle.

[0090] When the temperature is >33℃ and the volatile fatty acid (VFA) is >2000 mg / L, during the anaerobic fermentation process, on the 2nd, 4th, 6th, ... every 2 days, the fermentation broth is centrifuged at 6000 rpm for 15 min. After removing the supernatant, the precipitate is resuspended in 400 mL of deoxygenated water. Then, the organic waste treated with biochar is added in cycles at 4 wt%, 5 wt%, and 6 wt% of the fermentation broth.

[0091] Experimental Example 1: Investigating the effect of biochar preparation methods on the treatment efficiency of poultry and livestock manure.

[0092] Comparative Example 1: Unlike Example 1, the pyrolysis of straw fragments is not environmentally restricted.

[0093] Comparative Example 2: Unlike Example 1, the anaerobic pyrolysis does not use a gradient heating method.

[0094] Comparative Example 3: Unlike Example 1, the step of impregnating modified biochar with 1-butyl-3-methylimidazolium hydrogen sulfate is missing.

[0095] Table 1. Effects of the preparation methods of Examples 1-15 and Comparative Examples 1-2 on the treatment effect of poultry and livestock manure.

[0096]

[0097] Conclusion: As can be seen from the table above, the methane production and sludge VSS reduction percentage obtained according to the methods of Examples 1-15 showed significant changes. Among them, the parameter changes within the scope defined in this application had a relatively small impact on methane production and sludge VSS reduction percentage. Example 1 is superior overall. The results of treating poultry and livestock manure using the method of Example 1 are as follows: Figures 1-3 As shown.

[0098] Depend on Figure 1 It can be seen that, compared with PAA pretreatment and biochar pretreatment, the combined pretreatment significantly promoted the formation of methane in livestock and poultry manure. This may be related to the synergistic effect between PAA and biochar: on the one hand, PAA utilizes its strong oxidizing properties to destroy the EPS structure of livestock and poultry manure, transferring a large amount of organic matter from the solid phase to the liquid phase, providing more available substrates for anaerobic digestion; on the other hand, biochar utilizes its high specific surface area and abundant pores to adsorb NH3 and NH4+ from livestock and poultry manure. 4 + The combined pretreatment with PAA and biochar effectively promoted methanogenesis in livestock and poultry manure through synergistic effects. This was achieved by mitigating the inhibitory effects of high ammonia nitrogen concentrations and utilizing oxygen-containing functional groups on the surface to participate in and enhance DIET (digestion-exchange process) between microorganisms, thereby increasing the electron transfer rate during anaerobic digestion. However, biochar slightly inhibited methane production from livestock and poultry manure, which may be attributed to its ability to adsorb small amounts of organic molecules in the manure, leading to a reduction in the organic substrate available for methanogenesis in anaerobic digestion.

[0099] Depend on Figure 2 It can be seen that different pretreatment methods have different effects on the particle size of livestock and poultry manure. After pretreatment by different methods, the concentration values ​​of the particle size distribution of livestock and poultry manure, ranked from smallest to largest, are: combined pretreatment group, PAA pretreatment group, control group, and biochar pretreatment group. It can be inferred that both PAA pretreatment and combined pretreatment can significantly disrupt the EPS structure of livestock and poultry manure, breaking down larger flocculent particles. This is attributed to the cell-wall-breaking effect of PAA's strong oxidizing properties. Furthermore, combined pretreatment further enhances the breaking effect of PAA pretreatment, possibly because the adsorption and storage of PAA by biochar reduces the loss of PAA due to decomposition or escape, allowing PAA to exert its oxidative cell-wall-breaking effect for a longer period. However, biochar pretreatment has little effect on breaking down flocculent particles in livestock and poultry manure.

[0100] Depend on Figure 3It can be seen that VSS reduction is an indicator of the disintegration of livestock and poultry manure sludge. Compared with the control group, the VSS reduction of PAA pretreatment and combined pretreatment increased by 9.87% and 11.17%, respectively. This further illustrates that combined pretreatment can utilize strong oxidizing agents to break down the structure of livestock and poultry manure, releasing organic matter in the solid phase. This organic matter is mainly used for methanogenesis in anaerobic digestion, ultimately leading to a greater reduction in VSS of livestock and poultry manure. However, because biochar adsorbs a small amount of organic matter in livestock and poultry manure, this organic matter is not used for methanogenesis in anaerobic digestion, thus resulting in a smaller VSS reduction in the biochar pretreatment group. The above data indicate that combined pretreatment can improve the degree of disintegration of livestock and poultry manure, promote the release of organic matter, and thus increase methane production.

[0101] A comparison of Examples 1, 7-9, and Comparative Examples 1-2 reveals that both the lack of environmental constraints in straw fragment pyrolysis and the absence of gradient heating in anaerobic pyrolysis weaken the treatment effect of livestock manure. This is because anaerobic pyrolysis avoids oxidation reactions, improving the quality and performance of biochar; while gradient heating ensures a uniform pyrolysis process, forming a uniform pore structure and enhancing the adsorption capacity of biochar and microbial attachment sites. These factors work together to improve the effectiveness of biochar in anaerobic fermentation, thereby increasing cumulative methane production and the percentage reduction in sludge VSS.

[0102] A comparison of Examples 1, 12-13, and Control Example 3 shows that the absence of the modified biochar impregnation step with 1-butyl-3-methylimidazolium hydrogen sulfate also weakens the treatment effect of livestock manure. This is because the modification step can significantly improve the adsorption capacity, microbial adhesion performance, and pore structure of biochar, thereby increasing the efficiency of anaerobic fermentation and methane production. Experimental verification shows that the modified biochar exhibits significant improvements in adsorption performance, microbial adhesion, and anaerobic fermentation effect.

[0103] 2. Investigate the impact of the steps in the anaerobic digestion process on the treatment efficiency of livestock manure.

[0104] Comparative Example 3: Unlike Example 16, the pretreatment of the inoculated sludge was not performed.

[0105] Comparative Example 4: Unlike Example 16, the batch feeding only involves adding 3 wt% of the biochar-treated organic waste to the fermentation broth every other day.

[0106] Table 2. Effects of the preparation methods of Examples 1, 16-22, and Comparative Examples 3-4 on the treatment effect of poultry and livestock manure.

[0107]

[0108]

[0109] Conclusion: The comparison between Examples 1 and Examples 16-20 shows that the batch feeding step in the anaerobic digestion process has a significant impact on the treatment effect of poultry and livestock manure, and the effect is optimal under the parameters of Example 16. This is because batch feeding in the anaerobic digestion process can provide a continuous substrate supply, avoiding substrate overload caused by adding a large amount of substrate at once, thereby improving the stability of the system and methane production.

[0110] A comparison of Examples 16-18 and Control Example 3 shows that the lack of pretreatment of the inoculated sludge weakens the treatment effect of livestock manure. This is because pretreatment can improve the activity and adaptability of microorganisms, remove inhibitors, and regulate the fermentation environment. These steps are crucial for ensuring the stability and efficiency of the fermentation process. The data above confirms that the absence of these steps leads to a decrease in cumulative methane production and a reduction in the percentage of VSS reduction in sludge.

[0111] A comparison of Examples 16, 19-20, and Control Example 4 reveals that adding only 3 wt% biochar-treated organic waste to the fermentation broth every other day during batch feeding weakens the treatment effect of livestock manure. This is because insufficient feeding frequency and amount lead to inadequate substrate supply, interrupted microbial metabolism, and an unstable fermentation environment, thus affecting fermentation efficiency and methane production. By increasing the feeding frequency and amount, monitoring fermentation parameters, and pretreating the feeding substrate, fermentation efficiency and methane production can be effectively improved, thereby enhancing the treatment effect of livestock manure.

Claims

1. A method for treating poultry and livestock manure with peracetic acid-biochar to increase methane production, characterized in that, Includes the following steps: S1, Peracetic acid-biochar treatment Peracetic acid at a dosage of 10-20 mg / g TSS and biochar at a dosage of 0.5-2.0 g / g VSS were added to poultry and livestock manure, and then the mixture was treated in a constant temperature shaker at 30-35℃ and 120 rpm for 10-14 hours until it was evenly mixed to obtain poultry and livestock manure treated with peracetic acid-biochar. S2, Anaerobic fermentation treatment Add inoculated sludge to the peracetic acid-biochar treated poultry and livestock manure at a volume ratio of 1:1-2 (VSS of peracetic acid-biochar treated poultry and livestock manure to VSS of inoculated sludge). Adjust the pH to 6.8-7.2, then purge with nitrogen to maintain an anaerobic environment. Seal the container and place it in a constant temperature shaking incubator. Shake and culture at 30-35℃ and 110-130 rpm for 10-12 hours, then allow it to ferment statically for 0-30 days.

2. The method for increasing methane production by treating livestock manure with peracetic acid-biochar as described in claim 1, characterized in that, In S1, the addition method is as follows: first, biochar is added to the poultry and livestock manure, and then peracetic acid is added to the poultry and livestock manure containing biochar.

3. The method for increasing methane production by treating livestock manure with peracetic acid-biochar as described in claim 1, characterized in that, In S1, the preparation steps of the biochar are as follows: (1) Cut rice husks and straw into small pieces, treat them with hydrothermal heat at 150-200℃ for 20-30 minutes, wash them with water and air dry them for 3-4 days. Then dry them in an electric heating oven at 100-105℃ for 24-48 hours. Next, place them in a quartz box and put the quartz box in a vacuum tube furnace. Then pyrolyze the straw pieces in an anaerobic environment. Finally, grind the pyrolyzed straw biochar in a mortar and pass it through a 100-140 mesh sieve. The biochar passed through the sieve is the biochar used in the experiment. (2) The biochar is mixed with a 1-3M sodium hydroxide solution at a mass ratio of 1:8-10. After stirring evenly, the mixture is reacted at 80-90℃ for 2-3 hours. After the reaction is completed, the biochar is washed with deionized water 3-5 times until the washing solution is neutral. Then it is dried at 100-105℃ for 10-12 hours to obtain modified biochar. (3) The modified biochar is impregnated in 1-butyl-3-methylimidazolium hydrogen sulfate, stirred evenly, and then left to stand at room temperature for 22-24 hours; the mass ratio of the modified biochar to 1-butyl-3-methylimidazolium hydrogen sulfate is 1:1-5.

4. The method for increasing methane production by treating livestock manure with peracetic acid-biochar as described in claim 3, characterized in that, The rice husk and straw fragments are 3-5cm in length and have a surface area of ​​<15cm². 2 .

5. The method for increasing methane production by treating livestock manure with peracetic acid-biochar as described in claim 3, characterized in that, In (1), the method of anaerobic pyrolysis is as follows: nitrogen gas is continuously introduced into the vacuum tube at a flow rate of 0.3-0.5 L / min for 10-15 min, and then heated to 550-600℃ at a heating rate of 8-10℃ / min under anaerobic conditions, and held for 1.5-2 h for pyrolysis.

6. The method for increasing methane production by treating livestock manure with peracetic acid-biochar as described in claim 1, characterized in that, In S2, during the static fermentation process, the feed is added in batches, and the stirring speed is reduced to 70-80 rpm during each addition. The method for this batch feeding process is as follows: When the temperature is ≤33℃ and the pH value is <6.5, during the anaerobic fermentation process, 3-4wt% of the fermentation liquid should be added to the fermentation liquid every day to replenish the organic waste after biochar treatment. When the temperature is >33℃ and the volatile fatty acid (VFA) is >2000mg / L, the fermentation broth is centrifuged every 2-3 days during the anaerobic fermentation process. After removing the supernatant, the precipitate is resuspended with 200-400mL of deoxygenated water. Then, the organic waste treated with biochar is added in cycles at 3-4wt%, 4-5wt%, and 5-6wt% of the fermentation broth.

7. The method for increasing methane production by treating livestock manure with peracetic acid-biochar as described in claim 6, characterized in that, The parameters for centrifugation of the fermentation broth are: centrifugation speed of 5000-6000 rpm and centrifugation time of 12-15 min.

8. The method for increasing methane production by treating livestock manure with peracetic acid-biochar as described in claim 1, characterized in that, In S2, the nitrogen gas is introduced at a rate of 40-100 mL / min for 2-4 min.

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