Method for reducing greenhouse gas emission in aquaculture wastewater resource utilization process

Abstract

The invention provides a method for reducing greenhouse gas emission in a culture wastewater resource utilization process, and belongs to the technical field of planting and breeding circulation and culture waste resource utilization. The method comprises the following steps: S1, preparing a culture wastewater hydrothermal lysis solution; s2, partially replacing the chemical fertilizer with the aquaculture wastewater hydrothermal lysis solution to be used for crops, and evaluating the agricultural effect of partially replacing the chemical fertilizer with the hydrothermal lysis solution to return to the field; and S3, analyzing greenhouse gas emission in the process of returning the hydrothermal cracking liquid to the field. The method can shorten the storage time of the breeding wastewater, so that the emission of greenhouse gases during the storage period is reduced; the hydrothermal lysis solution partially replaces the chemical fertilizer, and ammonia volatilization and greenhouse gas emission can be remarkably reduced in the field returning process.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated planting and breeding cycles and the resource utilization of breeding waste, and relates to a method for reducing greenhouse gas emissions during the resource utilization of breeding wastewater. Background Art

[0002] The scale of China's livestock and poultry breeding industry is huge, generating approximately 3.05 billion tons of livestock and poultry manure annually, of which breeding wastewater accounts for as high as 70%. These breeding wastewaters contain a large amount of organic matter and nutrients. If not properly treated, they will become the main source of agricultural non-point source pollution, threatening the safety of soil and water bodies.

[0003] Currently, through policies such as the promotion of projects in whole counties and pilot projects for integrated planting and breeding cycles, China has achieved an integrated utilization rate of livestock and poultry manure of 79.4%. However, there are still problems such as high collection costs and low technical conversion efficiency. Research shows that returning livestock and poultry breeding wastewater to farmland has a good growth-promoting effect on crops. However, before returning the breeding wastewater to farmland, it needs to go through a long storage and fermentation process, and a large amount of greenhouse gases such as ammonia, nitrous oxide, methane, and carbon dioxide will be generated during this stage. In addition, nitrous oxide (N 2 O) may be generated during the wastewater treatment process, and its global warming potential is 265 times that of CO 2 At the same time, the breeding wastewater contains nutrients such as ammonia nitrogen and phosphorus. During the process of returning it to farmland, it is necessary to control the input of nitrogen and phosphorus nutrients, otherwise there will be a high ammonia volatilization and greenhouse gas emissions.

[0004] Currently, wastewater treatment is clearly incorporated into the emission reduction accounting system to promote the standardized development of the industry. At the same time, greenhouse gas emissions in the agricultural field are reduced by more than 10%, and the resource utilization of breeding wastewater is one of the key paths.

[0005] The resource utilization of breeding wastewater is not only the core means to solve the pollution problem, but also an important starting point for the low-carbon transformation of agriculture. Through technological innovation and policy support, it has significant potential in reducing the emissions of powerful greenhouse gases such as methane and nitrous oxide, which is crucial for achieving global climate goals and the sustainable development of agriculture.

[0006] Therefore, there is an urgent need for a technology and method to reduce greenhouse gas emissions during the resource utilization of livestock and poultry breeding wastewater. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a method for reducing greenhouse gas emissions during the resource utilization of breeding wastewater: performing hydrothermal cracking reaction on the breeding wastewater, which solves the problem of large greenhouse gas emissions during the long-term storage and anaerobic fermentation process of traditional resource utilization of breeding wastewater; the obtained hydrothermal cracking liquid is used to replace part of the chemical fertilizer with the nitrogen recommendation amount for returning to farmland, reducing greenhouse gas emissions in farmland.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The present invention provides a method for reducing greenhouse gas emissions during the resource utilization of aquaculture wastewater, comprising the following steps:

[0010] S1. Prepare a hydrothermal pyrolysis liquid of aquaculture wastewater;

[0011] S2. Partially replace chemical fertilizers with the hydrothermal pyrolysis liquid of aquaculture wastewater for crops, and evaluate the agronomic effects of partially replacing chemical fertilizers with the hydrothermal pyrolysis liquid for returning to the field;

[0012] S3. Analyze the greenhouse gas emissions during the process of returning the hydrothermal pyrolysis liquid to the field.

[0013] Preferably, the method for preparing the hydrothermal pyrolysis liquid of aquaculture wastewater in S1 is as follows:

[0014] Collect aquaculture wastewater;

[0015] Immediately carry out a hydrothermal reaction on the aquaculture wastewater in a high-pressure reactor to obtain a hydrothermal reaction mixture;

[0016] Filter the hydrothermal reaction mixture to obtain a hydrothermal carbonization liquid of aquaculture wastewater.

[0017] Preferably, the aquaculture wastewater is pig farm aquaculture wastewater or cattle farm aquaculture wastewater.

[0018] Preferably, the temperature of the hydrothermal pyrolysis reaction is 180-220°C, and the reaction time is 0.8-1.2 h.

[0019] Preferably, in S2, the recommended dosage for partially replacing chemical fertilizers is to replace 25-50% of nitrogen.

[0020] Preferably, the crops in S2 include but are not limited to wheat, corn, millet or sorghum.

[0021] Preferably, the agronomic effects in S2 include but are not limited to seed germination rate, plant height, biomass, grain yield, soil nutrient content.

[0022] Preferably, in S3, the greenhouse gases are detected by the static chamber method, and the greenhouse gases include but are not limited to CO 2 , N 2 O.

[0023] Preferably, the hydrothermal pyrolysis liquid of aquaculture wastewater can improve the seed germination rate, promote the growth of crop seedlings, and can significantly reduce ammonia volatilization and greenhouse gas emissions.

[0024] It has at least the following beneficial technical effects:

[0025] At present, there are utilization methods for livestock and poultry breeding wastewater. Among them, using livestock and poultry breeding wastewater for crop growth has good utilization effects. However, generally, the treatment of breeding wastewater is through long-term storage and then fermentation when it is used or directly applied to farmland. A large amount of greenhouse gases such as ammonia, nitrous oxide, methane, and carbon dioxide are generated during the storage stage. And a large amount of greenhouse gases are also generated during microbial fermentation. When applied to farmland, greenhouse gas emissions occur again. Therefore, a large amount of greenhouse gases are generated in the whole stage of the current utilization of breeding wastewater.

[0026] The method described in the present invention solves the problems of large greenhouse gas emissions during long-term storage and anaerobic fermentation in the traditional resource utilization of breeding wastewater.

[0027] The hydrothermal pyrolysis liquid obtained by the method of the present invention replaces part of the chemical fertilizer with the nitrogen recommended application rate for returning to the field, reducing greenhouse gas emissions in farmland. Brief Description of the Drawings

[0028] Figure 1 is a technical roadmap;

[0029] Figure 2 is the germination situation of wheat seeds under different seed soaking treatments;

[0030] Figure 3 is the influence of different seed soaking treatments on the germination potential of wheat seeds;

[0031] Figure 4 is the influence of different seed soaking treatments on the germination rate of wheat seeds;

[0032] Figure 5 is the influence of different treatments on the SPAD of wheat seedlings;

[0033] Figure 6 is the influence of different seed soaking treatments on the total root length of wheat seedlings;

[0034] Figure 7 is the influence of different seed soaking treatments on the total root surface area of wheat seedlings;

[0035] Figure 8 is the influence of different dairy farm wastewater treatments on the total root volume of wheat seedlings;

[0036] Figure 9 is the influence of different pig farm wastewater treatments on the total root volume of wheat seedlings;

[0037] Figure 10 is the influence of different treatments on the total root volume of wheat seedlings. Detailed Embodiments

[0038] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terms used in the present invention are only for describing particular embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0041] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of this application are merely exemplary.

[0042] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0043] As used in the present invention, "room temperature" and "normal temperature" are both calculated as 25 ± 2°C unless otherwise specified.

[0044] Unless otherwise specified, the raw materials used in the following examples of the present invention are all obtained commercially.

[0045] Example 1

[0046] 1 Materials and Methods

[0047] 1.1 Test Materials

[0048] 11.3 kg of raw materials of pig farm breeding wastewater from Nanxiaowu Village, Jinzhou; 10.862 kg of raw materials of dairy farm breeding wastewater from Chengxin Dairy Farm, Zhengding; hydrothermal pyrolysis liquid products of pig farm breeding wastewater; hydrothermal pyrolysis liquid products of dairy farm breeding wastewater; wheat: Leimai 18; deionized water; 0.5% hydrogen peroxide solution; nutrient solution: H3 BO 3 0.58 g / L (9.3 mmol / L), MnSO 4 ·H 2 O 0.15 g / L (0.18 mmol / L), ZnSO 4 ·7H 2 O 0.26 g / L (0.9 mmol / L), CuSO 4 ·5H 2 O 0.04 g / L (0.18 mmol / L), ammonium molybdate 0.22 g / L (0.18 mmol / L), FeSO 4 ·7H 2 O 5.0 g / L (18 mmol / L), KNO 3 202.20 g / L (2 mol / L), KH 2 PO 4 68.05 g / L (0.5 mol / L), KCl 1.41 g / L (18.9 mmol / L), CaCl 2 443.92 g / L (4 mol / L), MgSO 4 30.09 g / L (250 mmol / L)

[0049] 1.2 Test equipment

[0050] Henan Lansite high-pressure reactor FCF-20;

[0051] Henan Lansite vacuum filter ZF-20LB;

[0052] Hydroponic box of Shanghai Yaya Greening Co., Ltd.;

[0053] Haili oxygen pump ACO-208.

[0054] 1.3 Test plan

[0055] 1.3.1 Preparation of hydrothermal pyrolysis liquid

[0056] Weigh 11.3 kg of the raw material of the pig farm wastewater from Nanxiaowu Village, Jinzhou and transfer it to the Henan Lansite high-pressure reactor. Control the reaction temperature at 200 °C and the reaction time at 1 h. After the reaction, naturally cool it to room temperature. The hydrothermal pyrolysis liquid of the pig farm wastewater obtained is collected in 500 mL plastic bottles and stored at room temperature indoors; weigh 10.9 kg of the raw material of the dairy farm wastewater from Zhengding Chengxin and prepare the hydrothermal pyrolysis liquid in the same way, collect it in 500 mL plastic bottles and store it at room temperature indoors.

[0057] 1.3.2 Preliminary experiment - Determination of the germination potential and germination rate of wheat seeds

[0058] First, soak wheat seeds in deionized water for 5 min. Replace the deionized water and add 0.5% hydrogen peroxide to it, stir well, then soak the wheat seeds again for 30 min. Float the seeds to remove the shriveled grains. After soaking, select plump seeds, spread them on filter paper, place them in a tray to air dry, and set aside for use.

[0059] Respectively pipette 2 ml, 1 ml, 0.5 ml, 0.2 ml, 0.1 ml (diluted 50, 100, 200, 500, 1000 times) of four solutions, namely the breeding wastewater from Nanxiaowu Village Pig Farm in Jinzhou, the breeding wastewater from Zhengding Chengxin Dairy Farm, the hydrothermal pyrolysis liquid of pig farm breeding wastewater, and the hydrothermal pyrolysis liquid of cattle farm breeding wastewater, into 100-ml volumetric flasks, make up to 100 ml with distilled water, shake well, and set aside for use.

[0060] Wash and dry the petri dishes for later use.

[0061] Place double-layer filter paper in the petri dishes, add 5 ml of each of the above 100-ml volumetric flask solutions to them. At the same time, set up a control group. Each treatment is set with 4 replicates. Place 20 wheat seeds in each petri dish, cover the lid to retain moisture, place them in a constant temperature incubator for cultivation, and record the daily germination situation of the wheat seeds.

[0062] 1.3.3 Hydroponic wheat seedling experiment with hydrothermal pyrolysis liquid of breeding wastewater

[0063] Test culture solutions: Fulvic acid stock solution; breeding wastewater from Nanxiaowu Village Pig Farm in Jinzhou; breeding wastewater from Zhengding Chengxin Dairy Farm; hydrothermal pyrolysis liquid of pig farm breeding wastewater; hydrothermal pyrolysis liquid of cattle farm breeding wastewater;

[0064] Germination of wheat seeds: Place the above-prepared wheat seeds in an incubator in advance, cultivate wheat to germinate with distilled water, and uniformly transfer them to the incubator with the reserve culture solution after germination.

[0065] Configuration of the culture solution:

[0066] ① First configuration on April 11: Respectively take 190 ml, 95 ml, 47.5 ml, 19 ml, 9.5 ml of the five culture solutions, add tap water to 9.5 kg, cover the lid, install an oxygen pump, a check valve, and sand and gravel, start cultivation, and aerate for 15 min each in the morning, noon, and evening in the early stage. According to the volume of the liquid in the incubator, each nutrient solution is added at a dilution of 1000 times;

[0067] ② Second configuration on April 21: Respectively take 148 ml, 74 ml, 37 ml, 14.8 ml, 7.4 ml of the five culture solutions, add tap water to 7.4 kg. Add 7.4 ml of each of the ten nutrient solutions;

[0068] ③4.26 Third configuration: Take 148 ml, 74 ml, 37 ml, 14.8 ml, and 7.4 ml of the five culture media respectively, and add tap water to 7.4 kg. Add 7.4 ml of each of the ten nutrient solutions;

[0069] ④4.29 Fourth configuration: Take 148 ml, 74 ml, 37 ml, 14.8 ml, and 7.4 ml of the five culture media respectively, and add tap water to 7.4 kg. Add 7.4 ml of each of the ten nutrient solutions.

[0070] Harvest wheat seedlings after 18 days of hydroponics, and store the roots and stems and leaves separately.

[0071] 1.3.4. Technical route

[0072] See Figure 1 。

[0073] 1.4 Measurement indicators and methods

[0074] 1.4.1 Determination of basic indicators of aquaculture wastewater raw materials and liquid phase products

[0075] Use a conductivity meter to measure the EC of the solution; use a pH meter to measure the pH of the solution; use the external heating method of potassium dichromate to measure the organic matter; use H 2 SO 4 -H 2 O 2 Digestion method to measure the total nitrogen, phosphorus and potassium content of the solution.

[0076] 1.4.2 Preliminary experiment - Germination potential and germination rate of wheat seeds

[0077] (1) Germination potential of wheat seeds

[0078] The ratio of the sum of the number of germinated seeds per day within the number of days to the number of days, an indicator to measure the speed of seed germination;

[0079] (2) Germination rate of wheat seeds

[0080] Place the seeds under the most suitable germination conditions and calculate the number of seeds germinated within four days, accounting for the percentage of the tested seeds.

[0081] 1.4.3 Determination of wheat seedling indicators in hydroponics experiment

[0082] Randomly select three replicates for each treatment, scan them using a root scanner, and then analyze the wheat seedling roots using software.

[0083] 1) Biomass (fresh weight, dry weight) Weigh the leaves of wheat seedlings after cutting off the roots, and place them in an oven at 60 °C until dried to a constant weight

[0084] 2) Number of leaves

[0085] 3) Plant height: The length from the base of the wheat (i.e., the tillering node) to the tip of the top leaf

[0086] 4) SPAD value: Using a chlorophyll content meter, select three leaves on each seedling and take the average value

[0087] 5) Total root length

[0088] 6) Root surface area

[0089] 7) Total root volume

[0090] 2 Data statistical analysis

[0091]

[0092] Where: Gt - The number of germinations at time t days; Dt - The number of germination days; M1 - The final number of germinated seeds; M - The number of tested seeds

[0093] 3 Results and analysis

[0094] 3.1 Determination and analysis of basic indicators of aquaculture wastewater raw materials and liquid-phase products

[0095] The nutrient contents of pig farm aquaculture wastewater, cattle farm aquaculture wastewater, hydrothermal pyrolysis liquid of pig farm aquaculture wastewater, and hydrothermal pyrolysis liquid of cattle farm aquaculture wastewater are shown in Table 1. The organic matter content in the hydrothermal pyrolysis liquid of pig farm aquaculture wastewater increased by 740.63% compared with the original pig farm aquaculture wastewater, TN increased by 17.24%, TP increased by 300%, EC decreased by 2.9 units, and pH increased by 1.14 units; the organic matter content in the hydrothermal pyrolysis liquid of cattle farm aquaculture wastewater decreased by 25.81% compared with the original cattle farm aquaculture wastewater, and the contents of TN, TP, and TK remained unchanged, EC decreased by 15.4 units, and pH increased by 0.29 units. After the substances in the hydrothermal pyrolysis raw materials are pyrolyzed and converted into organic matter and concentrated in the solid-phase products, the organic matter content in the hydrothermal pyrolysis liquid decreases compared with the original liquid, and all of TN, TP, and TK in the raw materials enter the liquid phase, and the pH increases after hydrothermal pyrolysis.

[0096] Table 1 Nutrient contents of aquaculture wastewater and its hydrothermal pyrolysis liquid

[0097]

[0098]

[0099] 3.2 EC and pH parameters of the culture solution

[0100] The EC and pH data of the culture solution are shown in Table 2.

[0101] Table 2 Basic indicators of the culture solution

[0102]

[0103] 3.3 Analysis of Wheat Seed Germination Potential and Germination Rate

[0104] Under the same conditions, wheat seeds were hydroponically cultured. As Figure 2 can be seen, compared with the CK group, among the germinated seeds of wheat seeds on the first day, except for the 1000-fold dilution of the original pig farm wastewater, the germinated seeds of the remaining dilution multiples were lower than those of the CK group. All dilution multiples of the original cattle farm wastewater and the hydrothermal pyrolysis liquid of pig farm wastewater were lower than those of the CK group. Except for the 50-fold dilution of the hydrothermal pyrolysis liquid of cattle farm wastewater, they were lower than those of the CK group. On the second day, except for the 100-, 200-, and 500-fold dilutions of pig farm wastewater, they were higher than the control group. Among them, the germination rate of the 1000-fold dilution of the original pig solution reached 100%. The number of germinated seeds of the 500-fold dilution of the original cattle farm wastewater, the 50-fold dilution of the hydrothermal pyrolysis liquid of pig farm wastewater, and the 50- and 200-fold dilutions of the hydrothermal pyrolysis liquid of cattle farm wastewater were higher than those of the control group. 3 ml of liquid was added uniformly on the second day. On the third day, the number of germinated seeds of most wheat seeds was stable. The germination rates of the original pig 50, the original pig 1000, the original cattle 200, the original cattle 500, the pig solution 50, the pig solution 200, the cattle solution 50, and the cattle solution 200 were all higher than those of the control group. On the fourth day, it was observed that the germination potential of wheat seeds cultured with the original pig 1000, the original cattle 200, the original cattle 500, and the cattle solution 200 reached 100%.

[0105] As Figure 3 can be seen, the germination potential of the original pig 1000 and the cattle solution 50 was higher than that of the control group. Therefore, the seed germination of the original pig 1000 and the cattle solution 50 was faster than that of the control group.

[0106] As Figure 4 can be seen, the influence of different treatments on the wheat germination rate was relatively complex. Influence on the wheat germination rate: As the concentration of the original pig farm wastewater decreased continuously, the germination rate of wheat seeds gradually decreased; the original cattle farm wastewater showed a trend of first increasing and then decreasing as the concentration decreased. Among them, the germination rates of the original cattle 200 and 500 treatments were the highest; the hydrothermal carbonization liquid-phase product of pig farm wastewater was generally the same as the germination rate of wheat seeds; the hydrothermal carbonization liquid-phase product of cattle farm wastewater first decreased, then increased, and then decreased as the concentration decreased. Among them, the germination rate of wheat seeds in the cattle solution 200 treatment reached 100%.

[0107] 3.4 Analysis of Wheat Seedling Measurement Indexes

[0108] 3.4.1 Influence on the Photosynthesis of Wheat Seedlings

[0109] See Figure 5, by measuring the SPAD value of wheat seedling leaves, it can be seen that the values of 1000 of fulvic acid stock solution, 200 of pig original, 500 of pig original, 100 of cattle original, 1000 of cattle original, 200 of cattle original, and 200 of pig solution are all higher than those of the control group. Therefore, the above six are beneficial to the photosynthesis of wheat seedlings and increase the chlorophyll content. Among them, the effect of 200 of cattle original is the best, followed by 1000 of fulvic acid stock solution, and the effect of 100 of cattle original is second only to 1000 of fulvic acid stock solution. Among the hydrothermal carbonization liquids, only 200 of pig solution has a better effect, increasing by 15.87% compared with the CK group.

[0110] 3.4.2 Effects on the above-ground parts of wheat seedlings

[0111] For all wheat seedlings, three plants were randomly selected for measurement and recording. According to Table 3 and the continued Table 3, except for the fulvic acid stock solution, the fresh weight and dry weight of wheat seedlings cultured with most of the raw materials of pig farm wastewater, raw materials of cattle farm wastewater, hydrothermal pyrolysis liquid of pig farm wastewater, and hydrothermal pyrolysis liquid of cattle farm wastewater showed an upward trend. Among them, the growth-promoting effects of 200 of pig original, 1000 of cattle original, 500 of cattle original, and 200 of pig solution were the most obvious. Compared with the control group, when 200 of pig original was used as the hydroponic culture solution, the fresh weight increased by 203.97% and the dry weight increased by 112.5%. The fresh weight of 1000 of cattle original increased by 169.05% and the dry weight increased by 108.33%. The fresh weight of 500 of cattle original increased by 146.03%; the dry weight increased by 95.83%. The fresh weight of 200 of pig solution increased by 118.25% and the dry weight increased by 95.83%. The number of leaves of all treatments except the fulvic acid stock solution and 50 and 100 of pig original increased. Among them, the number of leaves of 500 of cattle original, 1000 of cattle original, 500 of pig solution, and 500 of cattle solution increased the most. Compared with the average plant height of the control group, the plant height of 200 of pig original increased by 32%, the plant height of 500 of cattle original increased by 29.71%, and the plant height of 200 of pig solution increased by 29.14%. Based on the above data, it can be seen that 500 of cattle original has the best growth-promoting effect on the above-ground parts of wheat seedlings, followed by 200 of pig original and 1000 of cattle original, and 200 of pig solution follows closely.

[0112] Table 3 Indexes of the above-ground parts of wheat seedlings

[0113]

[0114] Continued Table 3 Indexes of the above-ground parts of wheat seedlings

[0115]

[0116] 3.4.3 Effects on the underground parts of wheat seedlings

[0117] See Figures 6 - 10, The effects of different hydroponic culture solutions on the underground parts of wheat seedlings were analyzed by the total root length, total surface area, and total volume of the roots. Compared with the CK group, the root-promoting effect of Pig Original 200 was the most obvious with an increase of 128.90%, the growth increment of Cow Original 500 as a culture solution was 106.86%, and the growth increment of Pig Solution 200 was 63.07%;

[0118] The promoting effects of the hydrothermal pyrolysis solutions of the livestock farm and pig farm wastewater as culture solutions on the total root surface area were very obvious. In the original livestock farm wastewater, Cow Original 1000, Pig Original 200, and Cow Original 500 had a promoting effect on root growth, among which the promoting effect of Cow Original 1000 was the most obvious, approaching twice that of the control group; among the hydrothermal pyrolysis solutions of the livestock farm wastewater, the effect of Pig Solution 200 was the best, followed by Pig Solution 500 and Cow Solution 200;

[0119] Compared with the control group, Mengbang (fulvic acid stock solution) 1000 had a significant effect on the root volume, but it was found by analysis that the difference in concentration between Mengbang 200 and Mengbang 500 had no significant effect on the root volume.

[0120] There were significant differences between Cow Solution 200, Cow Solution 1000 and Cow Solution 50, Cow Solution 100, indicating that in the hydrothermal carbonization solution of the livestock farm wastewater, with the stepwise change of concentration, the effect on the change of the total root volume was obvious, but the difference between these five groups of the hydrothermal carbonization solution of the livestock farm wastewater and the control group was not significant.

[0121] There was a significant difference between Cow Original 1000 and the control group. Except for Cow Original 1000, there was no significant difference with the control group. In addition, there were also significant differences between Cow Original 1000 and Cow Original 50, Cow Original 100, and there was no significant difference between Cow Original 200 and Cow Original 500.

[0122] There was no significant difference between the treatment of the Pig Solution group and the control group, but there was a significant difference between Pig Solution 200, Pig Solution 500 and Pig Solution 50, indicating that the change of concentration within some concentration gradients had a significant effect on the total root volume.

[0123] There was a significant difference between Pig Original 500 and the control group, and there were significant differences between Pig Original 200 and Pig Original 50, Pig Original 1000.

[0124] In the original livestock farm wastewater, Pig Original 500, Pig Original 200, and Cow Original 1000 had the most significant effects; compared with the control group, Cow Original 1000, Pig Original 500, and Pig Original 200 increased by 75%, 64.29%, and 50% respectively; in the hydrothermal carbonization solution of the livestock farm wastewater, Cow Solution 1000, Pig Solution 500, and Pig Solution 200 had a significant effect on the root volume of wheat seedlings. Pig Solution 500, Pig Solution 200, and Cow Solution 1000 increased by 41%, 39.29%, and 28.57% respectively compared with the control group.

[0125] 3.4.4 Summary

[0126] Compared with the control, after cultivating wheat seeds with the original solution of pig farm wastewater diluted 50 times, 100 times, the original solution of cattle farm wastewater diluted 200 times, 500 times, the hydrothermal pyrolysis liquid of pig farm wastewater diluted 50 times, and the hydrothermal pyrolysis liquid of cattle farm wastewater diluted 50 times, 200 times, the germination rate of wheat seeds was greater than or equal to that of the control group. Therefore, pig solution 50, pig solution 100, cattle solution 200, cattle solution 500 in the original solution, and pig solution 50, cattle solution 50, cattle solution 200 in the hydrothermal carbonization liquid could all promote the germination of wheat seeds.

[0127] Compared with the control, among the original solution, only the SPAD values of cattle original 200, cattle original 100, cattle original 1000 and pig solution 200 in the hydrothermal carbonization liquid were higher than those of the control group. Among them, the chlorophyll content of cattle original 200 increased by 36.19%. Other hydrothermal carbonization liquid phase products had a slight inhibitory effect on the chlorophyll content of wheat seedlings.

[0128] Compared with the control, among the original solution of pig original 200, cattle original 500, cattle original 1000, and in the hydrothermal pyrolysis liquid of cattle solution 200, pig solution 200, pig solution 500, after comprehensively considering the fresh weight, dry weight, number of leaves, and average plant height, they showed a significant promoting effect on the above-ground part of wheat seedlings.

[0129] Compared with the control, among the original solution of pig original 200, cattle original 500, cattle original 1000, and in the hydrothermal pyrolysis liquid of pig farm wastewater, pig solution 200, pig solution 500, pig solution 100 had a good effect on root length; in the original solution of cattle original 1000, pig original 200, cattle original 500 in the original solution of breeding wastewater had a promoting effect on root growth; in the hydrothermal pyrolysis liquid of breeding wastewater, pig solution 200 had the best effect, followed by pig solution 500 and cattle solution 200; in the original solution of pig original 500, pig original 200, cattle original 1000 in the original solution of breeding wastewater, and in the hydrothermal pyrolysis liquid of pig solution 1000, pig solution 500, pig solution 200 in the hydrothermal pyrolysis liquid of breeding wastewater had a significant impact on the root volume of wheat seedlings.

[0130] 4 Conclusions

[0131] (1) Applying the original solution of breeding wastewater and hydrothermal pyrolysis liquid can promote the germination of wheat seeds, but appropriate concentrations need to be selected. Through this experiment, it can be seen that diluting the pig farm wastewater appropriately by 100 times, the cattle farm wastewater appropriately by 200 times, 500 times, diluting the hydrothermal pyrolysis liquid obtained after the hydrothermal pyrolysis reaction of pig farm wastewater by 50 times, and diluting the cattle farm by 50 times, 200 times have a good effect on promoting the germination of wheat seeds.

[0132] (2) Considering the relevant indicators of photosynthesis, above-ground part, and underground part comprehensively, pig solution 200 has the most significant promoting effect on the growth of wheat seedlings, followed by pig solution 500 and cattle solution 200.

[0133] The above conclusions show that the liquid products of hydrothermal pyrolysis of pig farm and cattle farm breeding wastewater can improve the germination of wheat seeds and the growth of seedlings, but the appropriate concentration needs to be selected through experiments.

[0134] Example 2

[0135] 1 Materials and Methods

[0136] The experiment was carried out in Nanxiaowu Village, Jinzhou City, Hebei Province, and the tested crop was winter wheat. The climate of the experimental field belongs to the temperate continental semi-humid monsoon climate, with an average annual rainfall of 580 mm. Wheat, corn and other crops have been continuously planted in the experimental field for many years. The basic properties of the tested soil (0-20 cm) are as follows: pH is 7.8 (soil: water = 1:2.5), organic matter content is 1.3%, total nitrogen is 1.6 g / kg, available phosphorus is 13.04 mg / kg, and available potassium is 146 mg / kg.

[0137] Using pig farm wastewater as raw material, the hydrothermal pyrolysis liquid of pig farm wastewater was prepared by a batch reaction device at 200 °C of hydrothermal reaction. The nutrient contents of the raw material and the hydrothermal carbonization product are shown in Table 4:

[0138] Table 4 Nutrient contents of raw material and hydrothermal carbonization product

[0139]

[0140] 2 Experimental Design

[0141] This experiment adopted a field plot experiment, and the plot area was 4.5 m * 7 m = 31.5 m 2 . A total of 6 treatments were set in this experiment: taking conventional fertilization as the control, 50% N replaced by pig farm wastewater, 25% N replaced by pig farm wastewater, 50% N replaced by the hydrothermal pyrolysis liquid of pig farm wastewater, 25% N replaced by the hydrothermal pyrolysis liquid of pig farm wastewater, liquid fertilizer of hydrothermal carbonization of pig farm wastewater (adding mineral source fulvic acid potassium, urease inhibitor, urea, etc.). The total nutrient input of each treatment was equal, which were: N 182 kg / hm 2 , P 2 O 5 107 kg / hm 2 , K 2 O 86 kg / hm 2 . Each treatment had 3 replicates and was randomly arranged. The nitrogen fertilizer used in this experiment was urea, the phosphorus fertilizer was diammonium phosphate, potassium dihydrogen phosphate and superphosphate, and the potassium fertilizer was potassium chloride. The irrigation method was border irrigation, and the irrigation amount per time was set at 900 m 3 / hm 2 / time, and the whole growth period was irrigated 3 times.

[0142] 3 Sample Collection and Determination

[0143] Ammonia volatilization was collected and measured by the closed chamber intermittent exhaust-dilute sulfuric acid absorption method. The closed chamber was a 20 cm diameter organic glass cylinder with an air inlet and a gas collection hole on the top. The air inlet was connected to a 1.5 m high ventilation pipe, and the gas collection hole was connected to a vacuum pump through an absorption device. Ammonia volatilization was collected every day for 7 days after each fertilization or precipitation (irrigation). Ammonia volatilization was collected every other day for 7-14 days. The collection time was 9:00-11:00 in the morning and 14:00-16:00 in the afternoon. Ammonia absorption was measured by a flow analyzer. The accumulation of ammonia volatilization was the sum of daily emissions during the observation period.

[0144] The calculation formula of ammonia volatilization flux is:

[0145] F=c*V*10 -2 *(24 / 4) / (π*r 2 )

[0146] Where F represents the ammonia volatilization flux [kg / (hm 2 ·d)]; c represents the concentration of ammonium nitrogen in the absorption liquid (mg / L); V represents the volume of sulfuric acid used for absorption (L); 24 / 4 represents the ratio of 24 h to the daily ammonia volatilization collection time of 4 h; r represents the radius of the gas chamber (m).

[0147] Greenhouse gases are measured using a closed static box-gas chromatograph method: The basic principle of a static box is to use a static box to cover the surface to be measured, and use an instrument to extract the gas in the static box at fixed intervals and inject it into a headspace bottle. The concentration of the gas to be measured in the headspace bottle is detected by a gas chromatograph, and the gas exchange rate between the surface soil and the atmosphere to be measured is obtained based on the rate of change of the gas concentration over time. During the growth period of winter wheat, the gas is collected once a day within 7 days after each fertilization or precipitation (irrigation), and once every two days from 7 to 14 days. The collection time is 9:00-11:00. While collecting the gas, the temperature at a depth of 5 cm in the soil, the surface soil temperature, the gas temperature in the static box, and the temperature of the atmosphere outside the box are recorded. Before covering the box, add water to the sealed water tank to ensure that the static box and the base are completely isolated from the outside world. Then start the fan in the static box, start timing after the gas in the box is evenly mixed, and use the automatic collection box device to extract the gas in the box at 0, 10, 20, and 30 minutes. After injecting it into a specific headspace bottle, the concentration of the gas in the bottle is detected as soon as possible. At the beginning and end of gas collection, a portable temperature sensor was used to measure the air temperature in the top box every 10 minutes. 2 、N 2 O was measured using a gas chromatograph, and the soil temperature at 5 cm and the ground surface temperature were measured using a portable temperature sensor while collecting greenhouse gases.

[0148] 4 Results and analysis

[0149] 4.1 Effect of hydrothermal pyrolysis of piggery wastewater on NH3 Effect of volatilization

[0150] The ammonia volatilization nitrogen loss rate in winter wheat soil was 6.2 - 29.4%, and the cumulative ammonia volatilization loss reached 5.4 - 32.8 kg / hm 2 , and the ammonia volatilization loss rate and cumulative loss amount were the highest in the conventional fertilization treatment. The ammonia volatilization loss rate and cumulative loss amount were the lowest in the treatment with 50% N replaced by the hydrothermal pyrolysis liquid of pig farm wastewater, which was 15.2% lower than that in the treatment with 50% N replaced by pig farm wastewater and 28.7% lower than that in the treatment with 25% N replaced by pig farm wastewater, and the difference reached a significant level.

[0151] 4.2 Effect of hydrothermal pyrolysis liquid of pig farm wastewater on CO 2 emission during the growth period of winter wheat

[0152] Analysis of change data

[0153] The cumulative CO 2 gas emissions in winter wheat soil were 15.3 - 22.6 t / hm 2 . The cumulative CO 2 gas emissions in the conventional fertilization treatment increased by 10.3% compared with the treatment with 50% N replaced by the hydrothermal pyrolysis liquid of pig farm wastewater and by 2.3% compared with the treatment with 50% N replaced by pig farm wastewater. Through significance analysis, the hydrothermal pyrolysis liquid had a significant effect on soil CO 2 gas emissions. Returning the hydrothermal pyrolysis liquid of pig farm wastewater to the field could significantly reduce the CO 2 gas emissions, indicating that the hydrothermal pyrolysis liquid had an obvious effect on the respiration of plant roots and soil organisms, and had an emission reduction effect on CO 2 gas compared with pig farm wastewater.

[0154] 4.3 Effect of hydrothermal pyrolysis liquid of pig farm wastewater on N 2 O emission during the growth period of winter wheat

[0155] The cumulative N 2 O gas emissions in winter wheat soil were 0.32 - 0.94 kg / hm 2 , and the N 2 O gas emissions were the largest in the conventional fertilization treatment. Compared with returning pig farm wastewater to the field, the cumulative N 2 O gas emissions in the treatment with the hydrothermal pyrolysis liquid of pig farm wastewater returned to the field decreased by 10.2 - 13.8%. This conclusion was consistent with the CO 2 gas emission law, indicating that the hydrothermal pyrolysis liquid of pig farm wastewater played a certain inhibitory role in the activity of soil denitrifying bacteria and had a positive effect on the reduction of soil N 2 O gas emissions.

[0156] 5 Conclusion

[0157] Returning the hydrothermal pyrolysis liquid of pig farm wastewater to the field can significantly reduce soil ammonia volatilization and greenhouse gas emissions of winter wheat, with a significant difference compared to the conventional fertilization treatment. In addition, the greenhouse gas emissions during the storage of pig farm wastewater need to be further detected to accurately evaluate the emission reduction effect of the hydrothermal carbonization technology throughout its life cycle. Monitor the effects of returning the hydrothermal pyrolysis liquid of pig farm wastewater to the field on wheat grain yield, soil organic carbon, available nitrogen, and phosphorus content to evaluate the agronomic effects of the resource utilization of pig farm wastewater.

[0158] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for reducing greenhouse gas emissions during resource utilization of aquaculture wastewater, characterized in that: The following steps are involved: S1 prepares aquathermal pyrolysis solution of aquaculture wastewater; S2. Use the hydrothermal cracking liquid of aquaculture wastewater to partially replace chemical fertilizers for crops, and evaluate the agronomic effect of returning the hydrothermal cracking liquid to the field to partially replace chemical fertilizers; S3. Analyze greenhouse gas emissions from the process of returning hydrothermal pyrolysis liquid to the field.

2. The method according to claim 1, characterized in that The preparation method of the aquatic thermal lysis liquid of aquaculture wastewater in S1 is: Collect aquaculture wastewater; Immediately subjecting the aquaculture wastewater to a hydrothermal reaction in a high-pressure reactor to obtain a hydrothermal reaction mixture; The hydrothermal reaction mixture is filtered to obtain aquaculture wastewater hydrothermal carbonization liquid.

3. The method according to claim 2, characterized in that The aquaculture wastewater is pig farm aquaculture wastewater or cattle farm aquaculture wastewater.

4. The method according to claim 2, characterized in that The temperature of the hydrothermal cracking reaction is 180-220° C., and the reaction time is 0.8-1.2 h.

5. The method according to claim 1, characterized in that The recommended dosage of S2 is to partially replace chemical fertilizers by replacing 25-50% of nitrogen.

6. The method according to claim 1, characterized in that The crops in S2 include but are not limited to wheat, corn, millet or sorghum.

7. The method according to claim 1, characterized in that The agronomic effects in S2 include but are not limited to seed germination rate, plant height, biomass, grain yield, and soil nutrient content.

8. The method according to claim 1, characterized in that: The greenhouse gases in S3 are detected by a static chamber method, and the greenhouse gases include but are not limited to CO2 and N2O.

9. The method according to claim 1, characterized in that: The aquathermal cracking liquid of the aquaculture wastewater can improve the germination rate of seeds, promote the growth of crop seedlings, and significantly reduce the emission of ammonia volatilization and greenhouse gases.

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