A method for reducing greenhouse gas emissions in the process of resource utilization of aquaculture wastewater

Abstract

The application provides a method for reducing greenhouse gas emission in the process of recycling utilization of aquaculture wastewater, and belongs to the technical field of aquaculture cycle and recycling utilization of aquaculture waste. The method comprises the following steps: S1, preparing aquaculture wastewater hydrothermal cracking liquid; S2, using the aquaculture wastewater hydrothermal cracking liquid to partially replace chemical fertilizer for crops, and evaluating the agronomic effect of the aquaculture wastewater hydrothermal cracking liquid; and S3, analyzing the greenhouse gas emission in the process of returning the aquaculture wastewater hydrothermal cracking liquid to field. The method can shorten the storage time of the aquaculture wastewater, and further reduce the greenhouse gas emission during the storage; the ammonia volatilization and the greenhouse gas emission can be significantly reduced in the process of returning the aquaculture wastewater hydrothermal cracking liquid to field.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of recycling and resource utilization of breeding waste, and relates to a method for reducing greenhouse gas emissions in the process of resource utilization of breeding wastewater. BACKGROUND

[0002] China's livestock and poultry breeding industry is large, producing about 3.05 billion tons of livestock and poultry manure annually, of which breeding wastewater accounts for as high as 70%. These breeding wastewater contains a large amount of organic matter and nutrients, and if not properly treated, it will become a major source of agricultural non-point source pollution, threatening soil and water safety.

[0003] At present, through the whole county promotion project, breeding and cultivation recycling pilot and other policies, China has achieved a comprehensive utilization rate of 79.4% of livestock and poultry manure, but there are still problems such as high collection cost and low technical conversion efficiency. Studies have shown that returning breeding wastewater to the field has a good effect on promoting crop growth. However, the breeding wastewater needs to be stored and fermented for a long time before it is returned to the field, which will produce a large amount of greenhouse gases such as ammonia, nitrous oxide, methane and carbon dioxide. In addition, nitrous oxide (N2O) may be produced during wastewater treatment, and its global warming potential is 265 times that of CO2. At the same time, the breeding wastewater contains nutrients such as ammonia nitrogen and phosphorus, which need to be controlled during the process of returning to the field, otherwise there will be high ammonia volatilization and greenhouse gas emissions.

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

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

[0006] Therefore, there is an urgent need for a technology and method for reducing greenhouse gas emissions in the process of resource utilization of livestock and poultry breeding wastewater. SUMMARY

[0007] Therefore, the purpose of the present application is to provide a method for reducing greenhouse gas emissions in the process of resource utilization of breeding wastewater: carrying out hydrothermal cracking reaction on breeding wastewater, solving the problem of long-term storage and large amount of greenhouse gas emissions during anaerobic fermentation in the traditional resource utilization of breeding wastewater; and using the obtained hydrothermal cracking liquid to replace part of the chemical fertilizer according to the recommended amount of nitrogen returned to the field, thereby reducing the greenhouse gas emissions in farmland.

[0008] In order to achieve the above purpose, the present application provides the following technical solutions:

[0009] The present application provides a method for reducing greenhouse gas emission in the process of recycling aquaculture wastewater, comprising the following steps:

[0010] S1. Preparing aquaculture wastewater hydrothermal pyrolysis liquid;

[0011] S2. Replacing part of chemical fertilizer with aquaculture wastewater hydrothermal pyrolysis liquid for crops, and evaluating the agronomic effect of replacing part of chemical fertilizer with aquaculture wastewater hydrothermal pyrolysis liquid;

[0012] S3. Analyzing the greenhouse gas emission in the process of replacing part of chemical fertilizer with aquaculture wastewater hydrothermal pyrolysis liquid.

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

[0014] Collecting aquaculture wastewater;

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

[0016] Filtering the hydrothermal reaction mixture to obtain aquaculture wastewater hydrothermal carbonization liquid.

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

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

[0019] Preferably, in S2, the recommended dosage of replacing part of chemical fertilizer is replacing 25-50% of nitrogen.

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

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

[0022] Preferably, in S3, the greenhouse gas is detected by the static chamber method, and the greenhouse gas includes but is not limited to CO2 and N2O.

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

[0024] At least the following beneficial technical effects are achieved:

[0025] At present, there are utilization methods of livestock and poultry breeding wastewater, among which the livestock and poultry breeding wastewater is used for crop growth and has good utilization effect; however, generally, the breeding wastewater is stored for a long time and then fermented or directly used in farmland when used; a large amount of greenhouse gases such as ammonia, nitrous oxide, methane, carbon dioxide and the like are generated during the storage stage; and a large amount of greenhouse gases are also generated during microbial fermentation; when applied to farmland, greenhouse gases are again discharged; therefore, a large amount of greenhouse gases is generated during the whole stage of the utilization of the breeding wastewater.

[0026] The method solves the problems of long-time storage and large amount of greenhouse gas emission during anaerobic fermentation in the traditional resource utilization of breeding wastewater.

[0027] The hydrothermal cracking liquid obtained by the method is used to replace part of chemical fertilizers and reduce the emission of greenhouse gases in farmland. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a technical roadmap;

[0029] Figure 2 It is the effect of different seed soaking treatments on the germination of wheat seeds;

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

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

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

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

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

[0035] Figure 8 It is the effect of different cattle farm wastewater treatments on the total volume of wheat seedling roots;

[0036] Figure 9 It is the effect of different pig farm wastewater treatments on the total volume of wheat seedling roots;

[0037] Figure 10 It is the effect of different treatments on the total volume of wheat seedling roots. DETAILED DESCRIPTION

[0038] The following detailed description of various exemplary embodiments of the application will not be considered to be limiting of the application. Instead, it should be understood to describe certain aspects, features and embodiments of the application in more detail.

[0039] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. In addition, where particular ranges of values are given, understand that each intervening value, to the upper or lower limit of the ranges is also specifically included. Each smaller range that falls within the broader ranges is also specifically included in the present application. The upper and lower limits of these smaller ranges can independently be included or excluded in the range.

[0040] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All patents, patent applications, publications, and descriptions mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the patents, patent applications, publications, and descriptions are cited.

[0041] Many modifications and variations of this application of the application can be made without departing from its spirit or scope, which will be apparent to those skilled in the art. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given should be considered exemplary only.

[0042] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional elements or steps.

[0043] As used herein, the terms "room temperature", "ambient temperature" refer to 25 ± 2 °C, unless otherwise specified.

[0044] Unless otherwise specified, the starting materials used in the following examples of the application are commercially available.

[0045] Example 1

[0046] 1. Materials and Methods

[0047] 1.1 Test materials

[0048] Jinzhousouth Xiaowucun pig farm breeding wastewater raw material 11.3 kg; Zhengding Chongxin dairy farm breeding wastewater raw material 10.862 kg; pig farm breeding wastewater hydrothermal cracking liquid product; dairy farm breeding wastewater hydrothermal cracking liquid product; wheat: Leimei 18; deionized water; 0.5% hydrogen peroxide solution; nutrient solution: H3BO3 0.58 g / L (9.3 mmol / L), MnSO4·H2O 0.15 g / L (0.18 mmol / L), ZnSO4·7H2O 0.26 g / L (0.9 mmol / L), CuSO4·5H2O 0.04 g / L (0.18 mmol / L), ammonium molybdate 0.22 g / L (0.18 mmol / L), FeSO4·7H2O 5.0 g / L (18 mmol / L), KNO3202.20 g / L (2 mol / L), KH2PO4 68.05 g / L (0.5 mol / L), KCl 1.41 g / L (18.9 mmol / L), CaCl2443.92 g / L (4 mol / L), MgSO4 30.09 g / L (250 mmol / L)

[0049] 1.2 Test equipment

[0050] Henan Lanshigui special high-pressure reactor FCF-20;

[0051] Henan Lanshigui special vacuum filter ZF-20LB;

[0052] Shanghai Yayagreening Co., Ltd. hydroponic box;

[0053] Heli oxygen pump ACO-208.

[0054] 1.3 Test scheme

[0055] 1.3.1 Preparation of hydrothermal cracking liquid

[0056] Take 11.3 kg of pig farm breeding wastewater raw material from Xiaowucun in Jinzhou and transfer it to the high-pressure reactor of Henan Lanshigui Special, control the reaction temperature at 200℃, and the reaction time is 1h. After the reaction is completed, it is naturally cooled to room temperature. The obtained pig farm breeding wastewater hydrothermal cracking liquid is collected in a 500mL plastic bottle and stored at room temperature. Take 10.9 kg of dairy farm breeding wastewater raw material from Zhengding Chongxin, and prepare the hydrothermal cracking liquid in the same way and collect it in a 500mL plastic bottle and store it at room temperature.

[0057] 1.3.2 Pre-experiment: determination of wheat seed germination energy and germination rate

[0058] Firstly, the wheat seeds were soaked in deionized water for 5 minutes, and then the deionized water was replaced with 0.5% hydrogen peroxide and stirred evenly. After soaking for another 30 minutes, the seeds were floated to remove the shriveled grains. The full seeds were selected and placed on filter paper in a tray for air drying, ready for use.

[0059] Respectively, 2ml, 1ml, 0.5ml, 0.2ml, 0.1ml (diluted 50, 100, 200, 500, 1000 times) of Jincheng Nanxiaowucun pig farm breeding wastewater, Zhengding Chongxin dairy farm breeding wastewater, pig farm breeding wastewater hydrothermal cracking liquid, and cow farm breeding wastewater hydrothermal cracking liquid were taken into 100ml volumetric flask, and distilled water was added to 100ml, and then shaken evenly for standby use.

[0060] The culture dishes were washed and dried for standby use.

[0061] The double-layer filter paper was placed in the culture dish, and 5ml of the above-mentioned 100ml solution was added, and the control group was set up, with 4 replicates for each treatment. 20 wheat seeds were placed in each culture dish, and the lid was covered to keep the water. The culture dishes were placed in a constant temperature incubator for cultivation, and the germination of wheat seeds was recorded every day.

[0062] 1.3.3 Wheat seedling test with hydrothermal cracking liquid of breeding wastewater

[0063] Test culture solution: fulvic acid stock solution; Jincheng Nanxiaowucun pig farm breeding wastewater; Zhengding Chongxin dairy farm breeding wastewater; pig farm breeding wastewater hydrothermal cracking liquid; cow farm breeding wastewater hydrothermal cracking liquid;

[0064] Wheat seed germination: the above-mentioned standby wheat seeds were placed in the incubator, and distilled water was used to cultivate wheat germination. After the emergence of the sprouts, they were uniformly transferred to the incubator with the reserved culture solution.

[0065] Culture solution configuration:

[0066] ① First configuration on April 11: 190ml, 95ml, 47.5ml, 19ml, 9.5ml of five kinds of culture solution were taken and added to 9.5kg of tap water. The lid was covered, the oxygen pump, check valve and sand were installed, and the cultivation started. In the early stage, 15min of oxygen was supplied every day, and according to the volume of the liquid in the incubator, 7.4ml of each nutrient solution was added.

[0067] ② Second configuration on April 21: 148ml, 74ml, 37ml, 14.8ml, 7.4ml of five kinds of culture solution were taken and added to 7.4kg of tap water. Seven kinds of nutrient solution were added with 7.4ml each.

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

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

[0070] After 18 days of hydroponics, wheat seedlings were collected, and the roots and stems and leaves were stored separately.

[0071] 1.3.4. Technical route

[0072] See Figure 1 .

[0073] 1.4. Determination index and method

[0074] 1.4.1. Basic index determination of aquaculture wastewater raw materials and liquid products

[0075] The conductivity of the solution was determined by conductivity meter; the pH of the solution was determined by pH meter; the organic matter was determined by potassium dichromate external heating method; the total nitrogen, phosphorus and potassium content of the solution was determined by H2SO4-H2O2 digestion method.

[0076] 1.4.2. Pre-experiment-wheat seed culture germination force and germination rate

[0077] (1) Wheat seed germination force

[0078] The ratio of the sum of the number of germinated seeds per day to the number of days within 7 days is an index for measuring the speed of seed germination;

[0079] (2) Wheat seed germination rate

[0080] The number of seeds germinated within four days under the most suitable germination conditions was calculated as a percentage of the test seeds.

[0081] 1.4.3. Index determination of wheat seedlings in hydroponics experiment

[0082] Three groups of repeats were randomly selected for each treatment, scanned by root scanning instrument, and then analyzed by software for wheat seedling root system.

[0083] 1) Biomass (fresh weight, dry weight) After cutting off the roots, the leaves were weighed and placed in a 60°C oven for drying to constant weight

[0084] 2) Leaf number

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

[0086] 4) SPAD value SPAD value was measured using a chlorophyll content meter, and the average value of three leaves from each seedling was selected

[0087] 5) Total root length

[0088] 6) Root surface area

[0089] 7) Total root volume

[0090] 2 Data statistical analysis

[0091]

[0092] In the formula: Gt - the number of germination at time t days; Dt - germination days; M1 - the final number of germination seed particles; M - the number of test seed particles

[0093] 3 Results and analysis

[0094] 3.1 Basic index determination and analysis of raw material and liquid product of aquaculture wastewater

[0095] The nutrient content of pig farm wastewater, cattle farm wastewater, pyrolysis liquid of pig farm wastewater, and pyrolysis liquid of cattle farm wastewater is shown in Table 1. The organic matter content of the pyrolysis liquid of pig farm wastewater increased by 740.63% compared to the raw liquid, 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 of the pyrolysis liquid of cattle farm wastewater decreased by 25.81% compared to the raw liquid, TN, TP, and TK contents remained unchanged, EC decreased by 15.4 units, and pH increased by 0.29 units. After pyrolysis of the substances in the raw material, organic matter is concentrated in the solid product, resulting in a decrease in organic matter content in the pyrolysis liquid compared to the raw liquid. TN, TP, and TK in the raw material all enter the liquid product, and the pH increases after pyrolysis.

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

[0097]

[0098]

[0099] 3.2 EC and pH parameters of culture solution

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

[0101] Table 2 Basic indicators of culture solution

[0102]

[0103] 3.3 Analysis of wheat seed germination potential and germination rate

[0104] Wheat seeds were hydroponically cultured under the same conditions. Figure 2 It can be seen that compared with the CK group, on the first day, the number of germinated wheat seeds was lower than that of the control group at all dilutions except for the 1000-fold dilution of pig farm wastewater concentrate. The number of germinated seeds at all dilutions of cattle farm wastewater concentrate and pig farm wastewater hydrothermal pyrolysis solution was lower than that of the CK group, except for the 50-fold dilution of cattle farm wastewater hydrothermal pyrolysis solution. On the second day, except for the 100, 200, and 500-fold dilutions of pig farm wastewater concentrate, the number of germinated seeds was higher than that of the control group. Specifically, the 1000-fold dilution of pig concentrate reached 100%, and the 500-fold dilution of cattle farm wastewater concentrate and pig... The number of germinated seeds in the hydrothermal pyrolysis solution of livestock farm wastewater diluted 50 times, and the number of germinated seeds in the hydrothermal pyrolysis solution of cattle farm wastewater diluted 50 and 200 times were higher than those in the control group. On the second day, 3 ml of solution was added to each solution. On the third day, the number of germinated seeds in most wheat seeds was stable. The number of germinated seeds in the solutions of pig (50), pig (1000), cattle (200), cattle (500), pig (50), pig (200), cattle (50), and cattle (200) were all higher than those in the control group. On the fourth day, it was observed that the germination potential of wheat seeds in the solutions of pig (1000), cattle (200), cattle (500), and cattle (200) reached 100%.

[0105] Depend on Figure 3 It can be seen that the germination potential of Zhuyuan 1000 and Niuye 50 is higher than that of the control group, therefore, the seeds of Zhuyuan 1000 and Niuye 50 germinate faster than those of the control group.

[0106] Depend on Figure 4 It is evident that the effects of different treatments on wheat germination rate are quite complex. Regarding the impact on wheat germination rate: as the concentration of the pig farm wastewater concentrate decreased, the germination rate of wheat seeds gradually decreased; for the cattle farm wastewater concentrate, the germination rate initially increased and then decreased with decreasing concentration. Treatments of 200 and 500 for cattle farm wastewater showed the highest germination rates. The germination rates of wheat seeds in the hydrothermal carbonization liquid phase products of pig farm wastewater remained largely consistent; for the hydrothermal carbonization liquid phase products of cattle farm wastewater, the germination rate initially decreased, then increased, and then decreased again with decreasing concentration, with the germination rate of wheat seeds in the 200 treatment for cattle farm wastewater reaching 100%.

[0107] 3.4 Analysis of Measurement Indicators for Wheat Seedlings

[0108] 3.4.1 Effects of photosynthesis on wheat seedlings

[0109] See Figure 5, the SPAD value of wheat seedling leaves can be determined, and the original solution of fulvic acid 1000, pig original 200, pig original 500, cow original 100, cow original 1000, cow original 200, pig liquid 200 are higher than the control group, so the above six kinds of culture solution are beneficial to the photosynthesis of wheat seedlings and increase the chlorophyll content. Among them, the effect of cow original 200 is the best, followed by fulvic acid original solution 1000, and the effect of cow original 100 is only second to fulvic acid original solution 1000. Only pig liquid 200 in water heat carbonization liquid has good effect, which increases by 15.87% compared with CK group.

[0110] 3.4.2 Effect on the aboveground part of wheat seedlings

[0111] All wheat seedlings were randomly selected for measurement and record. According to Table 3, Table 3, except for fulvic acid original solution, most of the pig farm breeding wastewater raw materials, cow farm breeding wastewater raw materials, pig farm breeding wastewater hydrothermal cracking liquid, and cow farm breeding wastewater hydrothermal cracking liquid showed an upward trend in the fresh weight and dry weight of wheat seedlings. Among them, pig original 200, cow original 1000, cow original 500, and pig liquid 200 had the most obvious growth-promoting effect. Compared with the control group, pig original 200 as the water culture liquid increased the fresh weight by 203.97%, and the dry weight by 112.5%. Cow original 1000 increased the fresh weight by 169.05%, and the dry weight by 108.33%. Cow original 500 increased the fresh weight by 146.03%, and the dry weight by 95.83%. Pig liquid 200 increased the fresh weight by 118.25%, and the dry weight by 95.83%. Except for fulvic acid original solution and pig original 50 and 100, the number of leaves of all treatments increased, among which cow original 500, cow original 1000, pig liquid 500, and cow liquid 500 increased the most. Compared with the average plant height of the control group, pig original 200 increased by 32%, cow original 500 increased by 29.71%, and pig liquid 200 increased by 29.14%. Based on the above data, cow original 500 had the best growth-promoting effect on the aboveground part of wheat seedlings, followed by pig original 200 and cow original 1000, and pig liquid 200.

[0112] Table 3 Index of the aboveground part of wheat seedlings

[0113]

[0114] Table 3 Index of the aboveground part of wheat seedlings

[0115]

[0116] 3.4.3 Effect on the underground part of wheat seedlings

[0117] See Figure 6-10The effects of different hydroponic solutions on the underground part of wheat seedlings were analyzed by total root length, total surface area and total volume. Compared with the CK group, pig original 200 had the most obvious root-promoting effect with an increase of 128.90%, followed by cow original 500 with an increase of 106.86%, and pig liquid 200 with an increase of 63.07%.

[0118] The total surface area of the root system was significantly promoted by the wastewater hydrothermal cracking liquid from the cattle and pig farms. The original liquid of the cattle and pig farms, including cow original 1000, pig original 200, and cow original 500, promoted the growth of the root system, with cow original 1000 being the most effective, nearly twice that of the control group. Among the wastewater hydrothermal cracking liquid, pig liquid 200 was the most effective, followed by pig liquid 500 and cow liquid 200.

[0119] Compared with the control group, the root volume was significantly affected by the original liquid of the sprout (fulvic acid), but the analysis showed that the difference in concentration between sprout 200 and sprout 500 had no significant effect on the root volume.

[0120] Cow liquid 200 and cow liquid 1000 had significant differences with cow liquid 50 and cow liquid 100, indicating that the change in concentration had a significant effect on the total volume of the root system in the wastewater hydrothermal carbonization liquid from the cattle farm, but there was no significant difference between the five groups of wastewater hydrothermal carbonization liquid from the cattle farm and the control group.

[0121] There was a significant difference between cow original 1000 and the control group, and there was no significant difference between the control group and the other groups except cow original 1000. In addition, there was a significant difference between cow original 50 and 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 pig liquid group and the control group, but there was a significant difference between pig liquid 200, pig liquid 500 and pig liquid 50, indicating that the change in concentration within the concentration gradient had a significant effect on the total volume of the root system.

[0123] There was a significant difference between pig original 500 and the control group, and there was a significant difference between pig original 200 and pig original 50 and pig original 1000.

[0124] The most effective in the original liquid of the breeding wastewater were pig original 500, pig original 200 and cow original 1000. 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 wastewater hydrothermal carbonization liquid, cow liquid 1000, pig liquid 500 and pig liquid 200 had a significant effect on the root volume of wheat seedlings, and pig liquid 500, pig liquid 200 and cow liquid 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, the germination rate of wheat seeds was greater than or equal to the control group after the wheat seeds were cultured with pig farm breeding wastewater original solution diluted 50 times, 100 times, cattle farm breeding wastewater original solution diluted 200 times, 500 times, pig farm breeding wastewater hydrothermal cracking solution diluted 50 times, and cattle farm breeding wastewater hydrothermal cracking solution diluted 50 times, 200 times, so the pig liquid 50, pig liquid 100, cattle liquid 200, cattle liquid 500 in the original solution and the pig liquid 50, cattle liquid 50, cattle liquid 200 in the hydrothermal carbonization solution can promote the germination of wheat seeds.

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

[0128] Compared with the control, the pig original 200, cattle original 500, cattle original 1000 in the original solution, and the cattle liquid 200, pig liquid 200, pig liquid 500 in the hydrothermal cracking solution showed significant promoting effect on the aboveground part of wheat seedlings in terms of fresh weight, dry weight, leaf number, and average plant height.

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

[0130] 4 Conclusion

[0131] (1) The application of breeding wastewater original solution and hydrothermal cracking solution can promote the germination of wheat seeds, but the appropriate concentration should be selected. According to the test, the pig farm breeding wastewater should be diluted by 100 times, the cattle farm breeding wastewater should be diluted by 200 times and 500 times, and the pig farm breeding wastewater hydrothermal cracking solution should be diluted by 50 times, and the cattle farm breeding wastewater hydrothermal cracking solution should be diluted by 50 times and 200 times to promote the germination of wheat seeds.

[0132] (2) Based on the photosynthesis, aboveground and underground related indicators, pig liquid 200 had the most significant promoting effect on the growth of wheat seedlings, followed by pig liquid 500 and cattle liquid 200.

[0133] The above results show that the pyrolysis liquid products of pig farm and cattle farm breeding wastewater can improve the seed germination and seedling growth of wheat, but the appropriate concentration should be selected through experiments.

[0134] Example 2

[0135] 1. Materials and Methods

[0136] The experiment was conducted in Nanxiaowu Village, Jinzhou City, Hebei Province, and the test crop was winter wheat. The test site has a temperate continental semi-humid monsoon climate, with an average annual rainfall of 580 mm for many years. The test site has been continuously planted with crops such as wheat and corn for many years. The basic properties of the test 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] Pig farm wastewater was used as raw material to prepare pig farm wastewater pyrolysis liquid under hydrothermal reaction at 200℃ using a sequencing batch reactor. 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 used field plot test, and the plot area was 4.5m*7m=31.5m 2 . This experiment set up 6 treatments: conventional fertilization as control, pig farm wastewater replacing 50% N, pig farm wastewater replacing 25% N, pig farm wastewater pyrolysis liquid replacing 50% N, pig farm wastewater pyrolysis liquid replacing 25% N, pig farm wastewater hydrothermal carbonization liquid fertilizer (adding mineral potassium fulvic acid, urease inhibitor, urea, etc.), each treatment with equal total nutrient input, respectively: N 182kg / hm 2 , P2O5 107kg / hm 2 , K2O 86kg / hm 2 , each treatment with 3 replicates, 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 was set to 900m 3 / hm 2 / time, with 3 times of irrigation during the whole growth period.

[0142] 3. Sample Collection and Determination

[0143] Ammonia volatilization was measured by the closed chamber intermittent air pumping-dilute sulfuric acid absorption method. The closed chamber was a 20 cm diameter organic glass cylinder with a gas inlet hole and a gas sampling hole at the top. The gas inlet hole was connected to a 1.5 m high air pipe, and the gas sampling hole was connected to a vacuum pump through an absorption device. Ammonia volatilization was collected continuously every day within 7 days after each fertilization or precipitation (irrigation), every other day from 7 to 14 days, and the collection time was from 9:00 to 11:00 am and from 14:00 to 16:00 pm. The ammonia absorption amount was measured by a flow analyzer. The accumulation of ammonia volatilization was the total daily emission during the observation period.

[0144] The formula for calculating ammonia volatilization flux is:

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

[0146] In the formula, F represents the ammonia volatilization flux [kg / (hm 2 ·d)]; c represents the ammonium nitrogen concentration 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; and r represents the radius of the gas chamber (m).

[0147] Greenhouse gases were measured by the closed static chamber-gas chromatograph method. The basic principle of the static chamber is to cover the surface to be measured with a static chamber, and every fixed time, the gas in the static chamber is extracted and injected into a headspace bottle using an instrument, and the concentration of the measured gas in the headspace bottle is detected by a gas chromatograph. According to the rate of change of gas concentration with time, the gas exchange rate between the soil surface and the atmosphere is obtained. During the winter wheat growing period, one collection was performed every day within 7 days after each fertilization or precipitation (irrigation), and one collection was performed every two days from 7 to 14 days, with the collection time being from 9:00 to 11:00. The temperature of the soil at a depth of 5 cm, the surface soil temperature, the gas temperature in the static chamber, and the temperature of the atmosphere outside the chamber were recorded simultaneously with the collection of the gas. Before covering the chamber, water was added to the sealed tank to ensure that the static chamber and the base were completely separated from the outside. Then the fan in the static chamber was started, and after the gas in the chamber was mixed evenly, the timing was started. At 0, 10, 20, and 30 min, the automatic sampling device was used to extract the gas in the chamber and inject it into a specific headspace bottle, and then the concentration of the gas in the bottle was detected as soon as possible. At the beginning and end of gas collection, a portable temperature sensor was used to measure the temperature in the headspace every 10 min. The determination of CO2 and N2O used a gas chromatograph, and the temperature of the soil at a depth of 5 cm and the surface temperature were measured simultaneously with the collection of the greenhouse gases.

[0148] 4 Results and analysis

[0149] 4.1 Effect of swine wastewater pyrolysis liquid on NH3 volatilization during the growing period of winter wheat

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

[0151] 4.2 Effect of pig farm wastewater hydrothermal cracking liquid on CO2 emission during the growth period of winter wheat

[0152] Change data analysis

[0153] The cumulative CO2 emission amount of winter wheat soil was 15.3-22.6 t / hm 2 The cumulative CO2 emission amount of the conventional fertilization treatment was increased by 10.3% and 2.3% compared with the pig farm wastewater hydrothermal cracking liquid replacing 50% N treatment and the pig farm wastewater replacing 50% N treatment, respectively. Through significance analysis, the effect of the hydrothermal cracking liquid on soil CO2 emission was significant, and the pig farm wastewater hydrothermal cracking liquid could significantly reduce the CO2 emission amount, indicating that the hydrothermal cracking liquid had a significant effect on the respiration of plant roots and soil organisms, and had a CO2 emission reduction effect compared with the pig farm wastewater.

[0154] 4.3 Effect of pig farm wastewater hydrothermal cracking liquid on N2O emission during the growth period of winter wheat

[0155] The cumulative N2O emission amount of winter wheat soil was 0.32-0.94 kg / hm 2 Among them, the N2O emission amount of the conventional fertilization treatment was the largest. Compared with the pig farm wastewater, the cumulative N2O emission amount of the pig farm wastewater hydrothermal cracking liquid was reduced by 10.2-13.8%, which was consistent with the CO2 emission rule, indicating that the pig farm wastewater hydrothermal cracking liquid had a certain inhibitory effect on the activity of soil denitrifying bacteria and had a positive effect on N2O emission reduction.

[0156] 5 Conclusion

[0157] The pig farm wastewater hydrothermal cracking liquid could significantly reduce the ammonia volatilization and greenhouse gas emission of winter wheat soil, and the difference was significant compared with the conventional fertilization treatment. In addition, the greenhouse gas emission of the pig farm wastewater during storage needed to be further detected to accurately evaluate the emission reduction effect of the whole life cycle of the hydrothermal carbonization technology. The effect of the pig farm wastewater hydrothermal cracking liquid on the wheat grain yield, soil organic carbon, available nitrogen, and phosphorus content after being applied to the field was monitored to evaluate the agronomic effect of the pig farm wastewater resource utilization.

[0158] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A method for reducing greenhouse gas emissions during the resource utilization of aquaculture wastewater, characterized in that, Includes the following steps: S1 is used to prepare hydrothermal pyrolysis solution of aquaculture wastewater; S2. Use hydrothermal pyrolysis liquid from aquaculture wastewater to partially replace chemical fertilizers for crops, and evaluate the agronomic effects of hydrothermal pyrolysis liquid partially replacing chemical fertilizers in returning to the field. S3. Analyze greenhouse gas emissions during the hydrothermal pyrolysis liquid return process; The preparation method of the aquaculture wastewater hydrothermal pyrolysis liquid in S1 is as follows: Collect aquaculture wastewater; The aquaculture wastewater was immediately subjected to a hydrothermal reaction in a high-pressure reactor to obtain a hydrothermal reaction mixture. The hydrothermal reaction mixture was filtered to obtain aquaculture wastewater hydrothermal carbonization liquid. The aquaculture wastewater is either pig farm aquaculture wastewater or cattle farm aquaculture wastewater; The hydrothermal pyrolysis reaction is carried out at a temperature of 180–220°C for a reaction time of 0.8–1.2 h. The S2 partially replaces chemical fertilizers to replace 25-50% of nitrogen; The agronomic effects in S2 include seed germination rate, plant height, biomass, grain yield, and soil nutrient content. In S3, greenhouse gases are detected using a static chamber method, and the greenhouse gases include CO2 and N2O.

2. The method according to claim 1, characterized in that, The crops in S2 include wheat, corn, millet, or sorghum.

3. The method according to claim 1, characterized in that, The hydrothermal pyrolysis liquid from the aquaculture wastewater can improve seed germination rate, promote crop seedling growth, and significantly reduce ammonia volatilization and greenhouse gas emissions.

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