Method for reducing greenhouse gas emission in paddy field by applying mixture of biogas slurry concentrate and pyroligneous acid
By preparing a method for combining biogas slurry concentrate with wood vinegar, the problem of high storage and transportation costs of biogas slurry in farmland was solved, and greenhouse gas emissions from paddy fields were effectively reduced. This achieved the goal of reducing fertilizer use and stabilizing production, and reduced emissions of CH4, N2O and CO2.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV OF SCI & TECH
- Filing Date
- 2023-04-10
- Publication Date
- 2026-05-29
AI Technical Summary
In existing technologies, the application of biogas slurry in farmland faces problems such as high costs for storage, transportation, and pipeline maintenance. At the same time, traditional methods have failed to effectively reduce greenhouse gas emissions from paddy fields.
The method of applying biogas slurry concentrate and wood vinegar in combination is adopted. By preparing biogas slurry concentrate and wood vinegar, the nitrogen fertilizer requirement of agricultural products throughout their entire growth period is used as the accounting benchmark. Combined with conventional chemical fertilizers to supplement nutrients, field trials are conducted to optimize the application mode, reduce the use of chemical fertilizers, and reduce greenhouse gas emissions.
The rational application of biogas slurry concentrate and wood vinegar significantly reduced the emissions of CH4, N2O and CO2 from paddy fields, reduced the amount of chemical fertilizer used, maintained stable rice yields, and mitigated the impact of global warming potential.
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Figure CN116472927B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of greenhouse gas emission reduction technology, specifically a method for reducing greenhouse gas emissions from paddy fields by combining biogas slurry concentrate with wood vinegar. Background Technology
[0002] Global warming has become a major concern for countries worldwide. It is widely believed that the greenhouse effect is closely related to the increased emissions of three greenhouse gases: carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Agricultural soils are one of the main sources of global greenhouse gas emissions, primarily CH4 and N2O, accounting for approximately 14% of total greenhouse gas emissions. Although the greenhouse effect of CH4 and N2O is less pronounced than that of CO2, their global warming potential (GWP) over a 100-year timescale is far greater than that of CO2, being 25 times and 298 times greater, respectively. Therefore, the environmental damage caused by greenhouse gas emissions from agricultural soils cannot be ignored.
[0003] Biogas slurry is a high-concentration organic wastewater produced by the dry-wet separation of waste fermentation liquid discharged during large-scale biogas production. It is characterized by large production volume, high concentrations of organic carbon and ammonium nitrogen, and high chemical and biochemical nutrient requirements, thus it is often used to partially replace nitrogen fertilizer in farmland. However, traditional biogas slurry disposal in farmland faces the challenge of high storage, transportation, and pipeline maintenance costs. Membrane separation technology (a technology that selectively separates mixtures of molecules of different particle sizes at the molecular level when passing through a semi-permeable membrane) combines separation and concentration functions, and is characterized by energy saving, high efficiency, simple process, and ease of control, and is widely used in various separation and concentration fields. Currently, in biogas slurry membrane concentration engineering, relatively mature membrane concentration systems can achieve 5-10 times concentration of the original biogas slurry, greatly improving the nutrient content and stability of the biogas slurry, and providing reliable technical support for the standardization and normalization of biogas slurry application in farmland.
[0004] Chinese patent CN111972233A discloses a method for applying biochar and wood acetic acid in paddy fields and its application in reducing greenhouse gas emissions from paddy fields. It utilizes biochar and wood acetic acid, a byproduct of its production process, to improve soil quality and fertility, and to achieve carbon sequestration. Chinese patent CN108002895A discloses a carbon-based liquid fertilizer and its production system and method. This fertilizer is prepared using wood acetic acid, biochar extract, biogas slurry, a suspending agent, nitrogen, phosphorus, and potassium fertilizer, potassium humate, alginic acid, chitin, and amino acids, and is used as fertilizer in agricultural cultivation. However, there are no reports on using concentrated biogas slurry combined with wood acetic acid to reduce greenhouse gas emissions from paddy fields. Summary of the Invention
[0005] The present invention aims to provide a method for reducing greenhouse gas emissions from paddy fields by combining biogas slurry concentrate and wood vinegar, thereby replacing chemical fertilizers.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] A method for reducing greenhouse gas emissions from paddy fields by combining concentrated biogas slurry with wood vinegar includes the following steps:
[0008] S1. Preparation of biogas slurry stock solution
[0009] Waste pig manure and urine are selected as raw materials for natural fermentation. The fermentation products are initially separated from the solid materials and the original biogas slurry through step-by-step sedimentation and peristaltic flushing of the filter screen.
[0010] S2. Preparation of biogas slurry concentrate
[0011] The solid materials and biogas slurry in the raw biogas slurry are separated in two stages using degreased cotton and microfiltration membranes. Then, the biogas slurry is desalinated and dehydrated through ultrafiltration or nanofiltration membranes to achieve membrane concentration of biogas slurry and discharge of permeate that meets the standards.
[0012] S3. Preparation of wood vinegar
[0013] Crop straw is crushed, placed in a dry distillation kettle for dry distillation, and the crude mixture is allowed to settle naturally, adsorbing light tar and precipitating heavy tar. The mixture is then filtered to obtain wood vinegar.
[0014] S4, combined application of biogas slurry concentrate and wood vinegar reduces greenhouse gas emissions from paddy fields.
[0015] Based on the nitrogen fertilizer requirement of agricultural products throughout their entire growth period, and with conventional fertilizer application treatment as a control, wood vinegar was added to biogas concentrate at different volume ratios and applied at various stages of the agricultural products' growth. To meet the needs of agricultural products for nitrogen, phosphorus, or potassium fertilizers, the missing nutrients were supplemented with conventional compound fertilizers, urea, potassium dihydrogen phosphate, and potassium chloride to ensure the normal growth of agricultural products.
[0016] S5. Select the optimal combination of biogas slurry concentrate and wood vinegar through field trials to reduce fertilizer application and lower greenhouse gas emissions from paddy fields.
[0017] Furthermore, in S1, the fermentation temperature is 25~30℃, and the fermentation time is 25 days.
[0018] Furthermore, in S2, during the preparation of the biogas slurry concentrate, the original biogas slurry is further fermented to increase the nutrient content of the biogas slurry; then, harmful substances and pathogens in the concentrate are removed by ultrafiltration or nanofiltration membrane, ultimately achieving the standard discharge of biogas slurry membrane concentrate and permeate.
[0019] Furthermore, in S3, the distillation temperature is 110~130℃, and the distillation time is 4.5~5 hours.
[0020] Furthermore, in S3, the straw is subjected to high-temperature dry distillation to adsorb light tar, precipitate heavy tar, and filter to obtain a wood vinegar solution rich in organic acids, alcohols, phenols, and ketones, which can then be used as a water-soluble fertilizer of organic matter.
[0021] Furthermore, in S4, wood vinegar was added to the biogas concentrate at volumes of 0%, 5%, 10%, and 20%. Except for the conventional fertilizer application treatment, all experimental treatments were treated with biogas concentrate, and the amount applied was 60% of the nitrogen content of the biogas concentrate replacing the nitrogen content of the conventional fertilizer.
[0022] Furthermore, in S4, the agricultural crop is rice, and the application of biogas slurry concentrate and wood vinegar occurs before seedling transplanting, during the tillering stage, and during the heading stage.
[0023] Furthermore, in S4, to meet the needs of rice for nutrients N, P2O5, and K2O throughout its entire growth period, the missing nutrients are supplemented by conventional urea, superphosphate, and potassium chloride.
[0024] The beneficial effects of the technical solution are:
[0025] 1. The raw materials for biogas slurry of this invention are pig manure and urine, and the raw materials for wood vinegar are crop straw. Both are easy to collect and store, and can also reduce non-point source pollution in rural areas and reduce environmental pollution caused by burning crop straw in rural areas.
[0026] 2. Experiments have shown that, compared with conventional fertilizer application, the application of biogas slurry concentrate combined with straw and wood vinegar has no significant difference in rice yield. This indicates that the reasonable combination of biogas slurry concentrate and wood vinegar can achieve stable yield and reduce the amount of fertilizer applied, thus achieving the goal of reducing fertilizer use and stabilizing yield.
[0027] 3. Compared with conventional fertilizer application treatments, the present invention significantly reduced the cumulative emissions of CH4, N2O, and CO2 from paddy fields by combining biogas slurry concentrate with straw and wood vinegar at volume ratios of 5%, 10%, and 20%. Specifically, the treatment with biogas slurry concentrate combined with 20% wood vinegar showed the best CH4 reduction effect, achieving a reduction of 36.25%; the treatment with biogas slurry concentrate combined with 20% wood vinegar showed the best N2O reduction effect, achieving a reduction of 24.02%; and the treatment with biogas slurry concentrate combined with 10% wood vinegar showed the best CO2 reduction effect, achieving a reduction of 46.15%.
[0028] 4. Compared with conventional fertilizer application treatment, the treatment of biogas slurry concentrate combined with straw and wood vinegar significantly reduced the impact of paddy fields on global warming potential (GWP). Among them, the treatment of biogas slurry concentrate combined with 10% wood vinegar had the best emission reduction effect, reducing emissions by 43.69%. Attached Figure Description
[0029] Figure 1 This embodiment of the invention describes the cumulative methane emissions during the entire growth period of rice treated with different volume ratios of biogas slurry concentrate and straw-wood vinegar.
[0030] Figure 2 This embodiment of the invention describes the cumulative nitrous oxide emissions during the entire growth period of rice treated with different volume ratios of biogas slurry concentrate and straw-wood vinegar.
[0031] Figure 3 This invention relates to the cumulative carbon dioxide emissions during the entire growth period of rice treated with different volume ratios of biogas slurry concentrate and straw-wood vinegar in various embodiments.
[0032] Figure 4 This invention illustrates the impact of different volume ratios of biogas slurry concentrate and straw-wood vinegar on global warming potential (GWP) in various embodiments.
[0033] In the figure, CF represents conventional fertilization, BS+0%PA represents single application of biogas slurry concentrate, BS+5%PA represents biogas slurry concentrate mixed with 5% straw-wood vinegar solution by volume, BS+10%PA represents biogas slurry concentrate mixed with 10% straw-wood vinegar solution by volume, and BS+20%PA represents biogas slurry concentrate mixed with 20% straw-wood vinegar solution by volume. Different lowercase letters in the same column indicate differences of up to 5% between treatments. Detailed Implementation
[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:
[0035] A method for reducing greenhouse gas emissions from paddy fields by combining concentrated biogas slurry with wood vinegar includes the following steps:
[0036] I. Experimental Materials: Preparation of Biogas Slurry Concentrate and Straw Wood Vinegar
[0037] The specific process of obtaining biogas slurry concentrate by using waste pig manure and urine as raw materials is as follows: pig manure and urine are fermented naturally at 25~30℃ for 25 days, and the solid and liquid are separated to obtain biogas slurry. The solid materials and biogas slurry in the biogas slurry are separated a second time using degreased cotton and microfiltration membrane. Then, the biogas slurry is desalted and dehydrated through ultrafiltration or nanofiltration membrane, and finally the biogas slurry membrane is concentrated and the permeate is discharged in compliance with standards.
[0038] The wood vinegar used in the experiment was made from rice straw. The specific process for obtaining straw wood vinegar was as follows: rice straw was crushed and placed in a dry distillation kettle for 4.5-5 hours. When the dry distillation temperature reached 110-130℃, the temperature was kept constant. The coarse mixture was allowed to settle naturally for 40-60 days to adsorb light tar and precipitate heavy tar. The mixture was then filtered to obtain the original wood vinegar solution. The physicochemical properties of the biogas slurry concentrate and the straw wood vinegar solution are shown in Table 1.
[0039] Table 1 Physicochemical properties of biogas slurry concentrate and straw-wood vinegar
[0040]
[0041] Note: "—" indicates that the content of this indicator is below or very close to the detection limit of the corresponding analytical method.
[0042] II. Overview of the Experimental Site and Experimental Methods
[0043] Field trials were conducted in a paddy field in Qiaowang Village, Duzhe Town, Quzhou City, Zhejiang Province. The tested soil was typical local paddy soil with the following basic physicochemical properties: pH 5.75, total nitrogen 1.62 g / kg, total phosphorus 1.82 g / kg, total potassium 12 g / kg, available nitrogen 122.85 mg / kg, available phosphorus 57.68 mg / kg, available potassium 86.75 mg / kg, and organic matter 29.99 g / kg. Straw-wood vinegar was added to the biogas slurry concentrate at volumes of 0%, 5%, 10%, and 20%, with conventional fertilizer application (CF) as a control. Each treatment was replicated in triplicate, and a randomized block design was used in a 4 m × 6 m plot. Except for the conventional fertilizer application (CF) treatment, all experimental treatments used biogas slurry concentrate, with the amount of biogas slurry concentrate replacing 60% of the nitrogen content of the conventional fertilizer. Based on the nutrient requirements of rice throughout its entire growth cycle (N, P2O5, K2O), and considering the nutrient input from biogas slurry and wood vinegar, subsequent fertilizer requirements will be met through conventional urea, superphosphate, and potassium chloride supplementation. The crop is single-season rice, with seedlings transplanted in late June. The nitrogen fertilizer application rate is 180 kg N·m³ / h. 1 For fertilizer application, conventional compound fertilizer with an N:P₂O₅:K₂O ratio of 16:10:12 was used. After applying a mixture of biogas slurry concentrate and wood vinegar, any deficiencies in nitrogen, phosphorus, and potassium fertilizers were supplemented with urea, superphosphate, and potassium chloride, respectively. Fertilizer was applied three times throughout the rice's growth period: basal fertilizer (seedling fertilizer), tillering fertilizer, and panicle fertilizer. The fertilization details for each treatment are shown in Table 2.
[0044] Table 2 Experimental fertilization scheme for the combined application of biogas slurry concentrate and straw-wood vinegar.
[0045]
[0046] Greenhouse gas collection and analysis were performed using a static chamber-gas chromatography (GC) system. Samples were taken twice daily, between 8:00 AM and 10:00 AM, at each growth stage of the rice plant. The static chamber, constructed of polyethylene and insulated with aluminum foil, measured 50cm x 50cm x 50cm. A 12cm diameter fan was installed inside to ensure gas mixing. The chamber included a pressure equalization port, a temperature detection port, and a sampling port. The temperature detection port was used to measure the gas temperature during sampling. The sampling port was connected to a latex tube and a three-way valve for gas sample collection. During sampling, the static chamber was placed on a base and sealed with water. After several minutes of stabilization, one gas sample was collected every 20 minutes using a 25mL medical syringe. Three gas samples were collected each time. These samples were stored in a dedicated vacuum bottle and brought back to the laboratory for analysis of the concentrations of the three gases. The emission rates were calculated based on the changes in the concentrations of the three gases over time, and the emission fluxes of the three greenhouse gases were then calculated from these emission rates. Gas samples were analyzed using a GC-2010plus gas chromatograph. The formula for calculating greenhouse gas emission fluxes from paddy fields is as follows:
[0047] F=ρ·273 / (273+T)·H·dC / dt
[0048] In the formula, F is the greenhouse gas emission flux (mg·m³). -2 ·h -1 or μg·m -2 ·h -1 ); ρ is the density of greenhouse gases under standard conditions: CO2 is 1.816 kg·m³. -3 CH4 content is 0.714 kg·m -3 The N2O content was 1.964 kg·m³. -3 H is the height of the sampling chamber, in meters; dC / dt is the corresponding greenhouse gas emission rate (mL·m³). -3 ·h -1 or μL·m -3 ·h -1 T represents the gas temperature inside the sampling chamber (°C).
[0049] Formula for calculating cumulative greenhouse gas emissions:
[0050]
[0051] In the formula, C is the cumulative gaseous emissions (kg·ha). 1 ), F i and F i+1 Gas emission flux (mg·m³) for two consecutive adjacent sampling periods 2 ·h 1 ), where d is the number of days between two consecutive adjacent sampling times.
[0052] This embodiment selects a 100-year timescale to calculate the global warming potential (GWP) of three rice paddy greenhouse gases (GHGs). The calculation formula is as follows:
[0053] GWP (kg CO2·ha) -1 )=[CO2]+25×[CH4]+298×[N2O]
[0054] In the formula, 25 and 298 are the GWP multiples of CH4 and N2O relative to CO2 on a 100-year scale, respectively.
[0055] III. Results and Analysis
[0056] 1. Effects of applying concentrated biogas slurry mixed with straw and wood vinegar on the physicochemical properties of topsoil
[0057] The effects of biogas slurry concentrate combined with straw-wood vinegar on the physicochemical properties (0-15 cm) of paddy field topsoil are shown in Table 3. Compared with conventional fertilizer application (CF), the biogas slurry concentrate combined with straw-wood vinegar treatment significantly increased soil pH. Meanwhile, there was no significant difference in soil organic matter content between biogas slurry concentrate combined with straw-wood vinegar and conventional fertilization. Regarding total soil nutrients, biogas slurry concentrate combined with straw-wood vinegar had no significant effect on total nitrogen, total phosphorus, and total potassium. Available potassium and available phosphorus in the biogas slurry concentrate combined with straw-wood vinegar treatment were not significantly different from those in conventional fertilization, but the alkaline nitrogen content in the treatments combined with 10% and 20% straw-wood vinegar was significantly increased compared to conventional fertilization.
[0058] Table 3. Effects of applying biogas slurry concentrate mixed with straw vinegar on the physicochemical properties of topsoil.
[0059]
[0060] 2. Effects of concentrated biogas slurry combined with straw and wood vinegar on rice yield and its components.
[0061] Table 4 shows the effects of concentrated biogas slurry combined with straw-wood vinegar on rice yield and its components.
[0062] Table 4. Effects of combined application of biogas slurry concentrate and straw-wood vinegar on rice yield and components.
[0063]
[0064] It can be seen that the rice yield under the conventional fertilizer application treatment (CF) was 3607.61 kg·ha. -1The rice yields of different treatments involving the application of concentrated biogas slurry combined with straw and wood vinegar ranged from 3352.28 to 3937.71 kg·ha. -1 Compared with the CF treatment, there were no significant differences among the treatments that combined biogas slurry concentrate with straw-wood vinegar. P >0.05). Furthermore, regarding the various yield components, the number of effective panicles in rice treated with biogas slurry concentrate combined with 10% and 20% straw-wood vinegar was significantly lower than that in the CF, BS+5%PA, and BS+5%PA treatments, while there was no significant difference in the number of effective panicles among these three treatments. P >0.05); In terms of the number of grains per ear and the weight of 1000 grains, there was no significant difference between the treatments of applying biogas slurry concentrate with straw and wood vinegar and the CF treatment. P >0.05). Overall, a reasonable combination of biogas slurry concentrate and straw-wood vinegar can achieve stable rice yields.
[0065] 3. The impact of applying concentrated biogas slurry combined with straw and wood vinegar on CH4 emissions from paddy fields.
[0066] like Figure 1 As shown, the cumulative CH4 emissions after basal fertilization were 65.28 kg·ha for the three replicates of the CF, BS+0%PA, BS+5%PA, BS+10%PA, and BS+20%PA treatments. -1 60.45 kg·ha -1 48.70 kg·ha -1 43.42 kg·ha -1 41.62 kg·ha -1 Compared with the control group CF, the treatments BS+0%PA, BS+5%PA, BS+10%PA, and BS+20%PA reduced CH4 emissions by 7.41% (BS+0%PA), 25.40% (BS+5%PA), 33.48% (BS+10%PA), and 36.25% (BS+20%PA), respectively. Compared with the control group, the application of different proportions of wood vinegar to the biogas concentrate significantly (P<0.05) reduced CH4 emissions, with the treatment of biogas concentrate with 20% wood vinegar (BS+20%PA) showing the best emission reduction effect.
[0067] 4. The impact of applying biogas slurry concentrate combined with straw vinegar on N2O emissions from paddy fields.
[0068] like Figure 2 As shown, the cumulative N2O emissions after basal fertilizer application were 3.13 kg·ha for the three replicates of the CF, BS+0%PA, BS+5%PA, BS+10%PA, and BS+20%PA treatments. -1 2.73 kg·ha-1 2.59 kg·ha -1 2.66 kg·ha -1 2.38 kg·ha -1 Compared with the control group CF, the BS+0%PA, BS+5%PA, BS+10%PA, and BS+20%PA treatments all reduced N2O emissions by 12.94% (BS+0%PA), 17.44% (BS+5%PA), 15.02% (BS+10%PA), and 24.02% (BS+20%PA), respectively. Compared with the control group, the application of different proportions of wood vinegar to the biogas concentrate significantly (P<0.05) reduced N2O emissions, with the treatment of biogas concentrate with 20% wood vinegar (BS+20%PA) showing the best emission reduction effect.
[0069] 5. The impact of applying biogas slurry concentrate combined with straw and wood vinegar on CO2 emissions from paddy fields.
[0070] like Figure 3 As shown, the cumulative CO2 emissions after basal fertilizer application, and the average cumulative CO2 emissions of the three replicates of the CF, BS+0%PA, BS+5%PA, BS+10%PA, and BS+20%PA treatments, were 17697.55 kg·ha. -1 16552.10 kg·ha -1 14155.01 kg·ha -1 9530.20 kg·ha -1 11083.56 kg·ha -1 Compared with the control group CF, the BS+0%PA, BS+5%PA, BS+10%PA, and BS+20%PA treatments all reduced CO2 emissions by 6.47% (BS+0%PA), 20.01% (BS+5%PA), 46.15% (BS+10%PA), and 37.37% (BS+20%PA), respectively. Compared with the control group, the BS+5%PA, BS+10%PA, and BS+20%PA treatments all significantly reduced CO2 emissions (P<0.05), with the treatment of biogas concentrate combined with 10% wood vinegar (BS+10%PA) showing the best emission reduction effect.
[0071] 6. Greenhouse effect of biogas slurry concentrate combined with straw and wood vinegar
[0072] like Figure 4As shown, different treatments of CO2, CH4, and N2O have an impact on the global warming potential (GWP). The treatment of adding straw and wood vinegar to biogas concentrate can significantly reduce the CO2 emission potential of paddy fields (P < 0.05). Compared with the control group CF, the treatments of BS+0%PA, BS+5%PA, BS+10%PA, and BS+20%PA reduced the CO2 emission equivalent by 6.85% (BS+0%PA), 20.33% (BS+5%PA), 43.69% (BS+10%PA), and 36.67% (BS+20%PA), respectively. Among them, the treatment of biogas concentrate combined with 10% wood vinegar (BS+10%PA) has the best emission reduction effect.
[0073] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.
Claims
1. A method for reducing greenhouse gas emissions from paddy fields by combining concentrated biogas slurry with wood vinegar, characterized in that, Includes the following steps: S1. Preparation of biogas slurry stock solution Waste pig manure and urine are selected as raw materials for natural fermentation. The fermentation products are initially separated from the solid materials and the original biogas slurry through step-by-step sedimentation and peristaltic flushing of the filter screen. S2. Preparation of biogas slurry concentrate The solid materials and biogas slurry in the raw biogas slurry are separated in two stages using degreased cotton and microfiltration membranes. Then, the biogas slurry is desalinated and dehydrated through ultrafiltration or nanofiltration membranes to achieve membrane concentration of biogas slurry and discharge of permeate that meets the standards. S3. Preparation of wood vinegar Crop straw is crushed, placed in a dry distillation kettle for dry distillation, and the crude mixture is allowed to settle naturally, adsorbing light tar and precipitating heavy tar. The mixture is then filtered to obtain wood vinegar. S4, combined application of biogas slurry concentrate and wood vinegar reduces greenhouse gas emissions from paddy fields. Based on the nitrogen fertilizer requirement of agricultural products throughout their entire growth period, and with conventional fertilizer application treatment as a control, wood vinegar was added to biogas concentrate at different volume ratios and applied at various stages of the agricultural products' growth. To meet the needs of agricultural products for nitrogen, phosphorus, or potassium fertilizers, the missing nutrients were supplemented with conventional compound fertilizers, urea, potassium dihydrogen phosphate, and potassium chloride to ensure the normal growth of agricultural products. In this experiment, wood vinegar was added to the biogas slurry concentrate at volumes of 0%, 5%, 10%, and 20%. Except for the conventional fertilizer application treatment, all experimental treatments were treated with biogas slurry concentrate, and the amount applied was 60% of the nitrogen content of the biogas slurry concentrate replacing the nitrogen content of the conventional fertilizer. The agricultural crop is rice. The application of biogas slurry concentrate and wood vinegar occurs before seedling transplanting, during the tillering stage, and during the booting stage. S5. Select the optimal combination of biogas slurry concentrate and wood vinegar through field trials to reduce fertilizer application and lower greenhouse gas emissions from paddy fields.
2. The method for reducing greenhouse gas emissions from paddy fields by combining biogas slurry concentrate with wood vinegar according to claim 1, characterized in that: In S1, the fermentation temperature is 25~30℃ and the fermentation time is 25 days.
3. The method for reducing greenhouse gas emissions from paddy fields by combining biogas slurry concentrate with wood vinegar according to claim 1, characterized in that: In S2, during the preparation of biogas slurry concentrate, the original biogas slurry is further fermented to increase the nutrient content of the biogas slurry; then, harmful substances and pathogens in the concentrate are removed by ultrafiltration or nanofiltration membrane, ultimately achieving the standard discharge of biogas slurry membrane concentrate and permeate.
4. The method for reducing greenhouse gas emissions from paddy fields by combining biogas slurry concentrate with wood vinegar according to claim 1, characterized in that: In S3, the distillation temperature is 110~130℃ and the distillation time is 4.5~5 hours.
5. The method for reducing greenhouse gas emissions from paddy fields by combining biogas slurry concentrate with wood vinegar according to claim 1, characterized in that: In S3, straw is dry distilled at high temperature to adsorb light tar, precipitate heavy tar, and filter to obtain wood vinegar rich in organic acids, alcohols, phenols and ketones, which can be used as a water-soluble fertilizer of organic matter.
6. The method for reducing greenhouse gas emissions from paddy fields by combining biogas slurry concentrate with wood vinegar according to claim 1, characterized in that: In S4, to meet the needs of rice for N, P2O5, and K2O throughout its entire growth period, the missing nutrients are supplemented by conventional urea, superphosphate, and potassium chloride.