A method for reducing nitrogen loss during cow dung composting

Abstract

The present invention discloses a method for reducing nitrogen loss in the process of cow dung composting, and relates to the technical field of fertilizer preparation. The method comprises the preparation of nanovesicles; pretreatment of composting raw materials; addition of nanovesicles; and composting fermentation. The present invention provides a method for reducing nitrogen loss in the process of cow dung composting by using nanovesicle technology. The method effectively reduces ammonia volatilization and nitrogen loss by preparing and using a specific type of nanovesicles, thereby improving the fertilizer efficiency of the compost product.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizer preparation, and more particularly to a method for reducing nitrogen loss in a cow dung composting process. Background Art

[0002] With the acceleration of urbanization, people's demand for meat, poultry and eggs has continued to increase, making my country's livestock and poultry farming industry gradually develop in the direction of scale, industrialization and structure, and thus a large amount of livestock and poultry manure has been generated. Livestock and poultry manure is rich in various nutrients required for plant growth and is a very valuable agricultural resource. Returning these nutrients to the land is a sustainable measure that can effectively promote nutrient circulation and increase the content of soil organic matter. Composting is an effective way to achieve its harmlessness and resource utilization. Under the biochemical action of microorganisms, organic matter is degraded and converted into organic fertilizer. The high temperature in the composting process kills pathogens, insect eggs and weed seeds, which has the advantages of short cycle and large processing capacity. However, in the warming and high temperature stage of aerobic high-temperature composting, due to the large-scale reproduction of microorganisms, the organic matter decomposes rapidly, and the organic nitrogen in livestock and poultry manure is easily decomposed by microorganisms and converted into ammonium nitrogen, and accumulates in the pile. Studies have pointed out that under the induction of high temperature and high pH, ​​the loss of ammonium nitrogen in poultry manure composting is as high as 62%, and the nitrogen loss caused by ammonia volatilization can reach 44%-99% of the total. This not only reduces the nutrient content in the fertilizer, but also intensifies the stench of the composting site, causing secondary pollution to the environment.

[0003] Therefore, providing a method for reducing nitrogen loss during cow dung composting is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0004] In view of this, the present invention provides a method for reducing nitrogen loss during cow dung composting.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for reducing nitrogen loss during cow dung composting comprises the following steps:

[0007] (1) phospholipids and cholesterol were mixed in a molar ratio of 8:1, phospholipids and cholesterol were dissolved in chloroform, the solvent was removed by a rotary evaporator to form a uniform film, and an aqueous phase solution was added for hydration, and the mass ratio of the aqueous phase to the film was 1:4;

[0008] (2) the temperature was controlled at 50 °C and the pH value was 7.0, and the nanovesicle suspension was treated with ultrasound at 20-40 kHz for 15 min and cooled at 4 to 10 °C;

[0009] (3) obtaining single-layer nanovesicles with a particle size between 100 and 150 nm by extrusion;

[0010] (4) Spread the cow dung out to dry in the sun to evaporate some of the water, add dry high-carbon auxiliary materials (such as straw and sawdust) to absorb water and increase porosity, adjust the moisture content to 50%-60%, increase the carbon-nitrogen ratio to 25-30:1, and keep the pH value between 6.5-7.5;

[0011] (5) In the initial stage of cow dung composting, the prepared nanocapsules are evenly sprayed or mixed into the cow dung at a rate of 1% to 5% of the total mass of the compost raw materials, and the compost is piled into a strip shape; the compost temperature is controlled between 40-60° C., and the compost is turned regularly to maintain the aeration of the compost, so as to promote the degradation of organic matter and the effective utilization of nitrogen;

[0012] (6) The treated cow dung is piled up for composting and fermentation; the composting temperature is controlled at 40-60° C., the fermentation time is 30-45 days, and the pile is turned every 5-7 days.

[0013] Furthermore, the phospholipid is a mixture of distearoylphosphatidylcholine (DSPC) and distearoylphosphatidylglycerol (DSPG), and the mass ratio is DSPC:DSPG=2:1.

[0014] Furthermore, the extrusion method in step (3) uses a high-pressure extruder and selects a polycarbonate membrane with a pore size of 100 nanometers;

[0015] The ultrasonically treated nanovesicle suspension is placed in the syringe of the extruder, and pressure is applied manually or by a pump to pass the suspension through the pore size of the polycarbonate membrane. To ensure the consistency and uniformity of the particle size, the suspension is extruded through the membrane of the same pore size multiple times, and 5 to 10 cycles of extrusion are performed to obtain the desired nanovesicle particle size.

[0016] Furthermore, the aqueous phase solution is a phosphate buffer solution containing nitrogen fertilizer, humic acid (Sigma-Aldrich, 68131-04-4) is dissolved in the phosphate buffer solution, and the zeolite is evenly dispersed in the aqueous phase solution by mechanical stirring or ultrasonication;

[0017] The humic acid accounts for 2% of the total mass of the phospholipids, and the zeolite accounts for 3% of the total mass of the phospholipids.

[0018] Furthermore, the nitrogen fertilizer is urea and ammonium sulfate, and the component ratio is: urea: 0.5% of the total mass of the aqueous solution; ammonium sulfate: 1% of the total mass of the aqueous solution;

[0019] The phosphate buffer composition is:

[0020] Sodium dihydrogen phosphate (NaH 2 PO 4 ): 8g / L;

[0021] Sodium hydrogen phosphate (Na2 HPO 4 ): 1.15g / L;

[0022] Sodium chloride (NaCl): 137 mM;

[0023] Potassium chloride (KCl): 2.7 mM;

[0024] The pH is 7.

[0025] Furthermore, the mechanical stirring condition is 1000-1500 rpm, 20-30 min; the ultrasonic condition is 20-40 kHz, 5-15 min.

[0026] It can be seen from the above technical solution that, compared with the prior art, the beneficial effects of the present invention are:

[0027] Nanovesicles are a nanoscale vesicle structure wrapped by a phospholipid bilayer, which has good encapsulation ability and biocompatibility. The application of nanovesicles in the process of cow dung composting can effectively reduce nitrogen loss and improve the fertilizer efficiency of composting through encapsulation and slow release functions.

[0028] (1) The method of the present invention achieves the slow release and effective utilization of nitrogen fertilizer by encapsulating nitrogen fertilizer in nanocapsules, reduces the volatilization loss of ammonia during cow dung composting, and improves the fertilizer efficiency of compost products. The method is not only simple and easy to implement, but also environmentally friendly and efficient.

[0029] (2) Humic acid has a strong cation exchange capacity and can absorb ammonia and reduce its volatilization. At the same time, humic acid can also promote soil microbial activity and improve nitrogen fixation capacity.

[0030] (3) The sulfate ions in ammonium sulfate can combine with ammonia to form non-volatile ammonium salts, thereby reducing the volatilization of ammonia. In addition, ammonium sulfate can also provide additional sulfur elements to promote plant absorption and utilization.

[0031] (4) Zeolite is a natural silicate mineral with strong adsorption capacity and can adsorb ammonia and other volatile nitrogen compounds. In addition, zeolite can also improve the physical structure of compost materials and improve aeration. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] Preparation of Nanovesicles:

[0035] A mixture of distearoylphosphatidylcholine (DSPC) and distearoylphosphatidylglycerol (DSPG) with a mass ratio of DSPC:DSPG = 2:1 was used to prepare phospholipids;

[0036] Phospholipids and cholesterol were mixed at a molar ratio of 8:1, dissolved in chloroform, the solvent was removed by a rotary evaporator to form a uniform film, and then an aqueous solution was added for hydration, and the mass ratio of the aqueous phase to the film was 1:4;

[0037] The aqueous solution is a phosphate buffer containing nitrogen fertilizer (urea: 0.5% of the total mass of the aqueous solution; ammonium sulfate: 1% of the total mass of the aqueous solution), humic acid (Sigma-Aldrich, 68131-04-4, 2% of the total mass of phospholipids) is dissolved in the phosphate buffer, and zeolite (3% of the total mass of phospholipids) is evenly dispersed in the aqueous solution by mechanical stirring (1500 rpm, 20 min);

[0038] The composition of phosphate buffer is:

[0039] Sodium dihydrogen phosphate (NaH 2 PO 4 ): 8g / L;

[0040] Sodium hydrogen phosphate (Na 2 HPO 4 ): 1.15g / L;

[0041] Sodium chloride (NaCl): 137 mM;

[0042] Potassium chloride (KCl): 2.7 mM;

[0043] The pH is 7.

[0044] The temperature was controlled at 50°C and the pH value was 7.0. Ultrasonic waves were used at 30kHz for 15 minutes and the nanovesicle suspension was cooled at 4°C. A polycarbonate membrane with a pore size of 100 nanometers was selected. The nanovesicle suspension treated with ultrasonic waves was placed in a syringe of an extruder. Pressure was applied manually or by a pump to pass the suspension through the pore size of the polycarbonate membrane. To ensure the consistency and uniformity of the particle size, the suspension was extruded through a membrane with the same pore size for multiple times. The extrusion was repeated 5 to 10 times to obtain single-layer nanovesicles with a particle size between 100 and 150 nanometers.

[0045] Composting raw material pretreatment:

[0046] Spread the cow dung out to dry, evaporate some of the water, add dry auxiliary materials (such as straw, sawdust) to absorb water and increase porosity, adjust the moisture content to 50-60%, increase the carbon-nitrogen ratio to 25:1, and keep the pH value between 6.5-7.5. Mix the above substances with the cow dung evenly and pile them into strips.

[0047] Addition of Nanovesicles:

[0048] In the initial stage of cow dung composting, the prepared nanocapsules are evenly sprayed or mixed into the cow dung at 2.5% of the total amount of compost raw materials. The compost temperature is controlled at 40-60℃, and the compost is turned regularly to maintain the aeration of the compost to promote the degradation of organic matter and the effective utilization of nitrogen.

[0049] Composting:

[0050] The treated cow dung is piled up for composting. The composting temperature is controlled at 40-60℃, the fermentation time is 45 days, and the pile is turned every 7 days.

[0051] Comparative Example:

[0052] Raw material pretreatment: Spread the cow dung out to dry in the sun to evaporate some of the water, add dry auxiliary materials (such as straw, sawdust) to absorb moisture and increase porosity, adjust the moisture content to 50-60%, increase the carbon-nitrogen ratio to 25:1, and keep the pH value between 6.5-7.5.

[0053] Composting: The treated cow dung is piled up for composting. The composting temperature is controlled at 40-60℃, the fermentation time is 45 days, and the pile is turned every 7 days.

[0054] As shown in Table 1, total nitrogen decreased to varying degrees in each example.

[0055] Table 1 Total nitrogen changes in each case during composting (g / kg)

[0056]

[0057] The control example decreased by 36.39%, and the sample example decreased by 27.07%, indicating that the present invention can effectively inhibit the loss of nitrogen during cow dung composting and promote the retention and maintenance of nitrogen.

[0058] Organic nitrogen is the main component of total nitrogen. Its changing trend during the composting process is consistent with that of total nitrogen, and its content in each example has decreased. As shown in Table 2, the changes of organic nitrogen in each example during the composting process.

[0059] Table 2 Changes of organic nitrogen in various cases during composting (g / kg)

[0060]

[0061] The organic nitrogen content of the comparative example decreased by 55.08% compared with the initial stage of composting, and the sample example decreased by 42.02%, which was significantly lower than that of the comparative example. This shows that the present invention can effectively reduce the loss of organic components in nitrogen, promote the fixation of organic nitrogen, and thus increase the organic matter content in the compost product.

[0062] The composting process is a process of continuously converting difficult-to-degrade organic matter into active nutrients that are easily absorbed and utilized through the activity of microorganisms. Under the action of microorganisms, available nitrogen is released from organic matter and the content gradually increases. As shown in Table 3, the changes in available nitrogen in each case of the composting process.

[0063] Table 3 Changes in available nitrogen in each case during composting (mg / kg)

[0064]

[0065] The available nitrogen in the comparative example increased by 21.32%, and that in the sample example increased by 25.48%. The sample example had a significantly higher ability to enhance the available nitrogen than the comparative example, indicating that the present invention can promote the conversion of stable nitrogen into mobile nitrogen and increase the available nutrient content in the compost product.

[0066] Table 4 Nitrogen loss due to ammonia volatilization (mg / pot)

[0067]

[0068] The ammonia volatilization of the comparative example was faster, reaching a peak on the 13th day; the sample example showed a higher ammonia volatilization loss only on the fourth day (still lower than the comparative example), reached a volatilization peak on the 45th day, and maintained a relatively low ammonia volatilization amount overall, indicating that the present invention is beneficial to reducing nitrogen loss.

[0069] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for reducing nitrogen loss during cow dung composting, characterized in that: The following steps are involved: (1) phospholipids and cholesterol were mixed in a molar ratio of 8:1, phospholipids and cholesterol were dissolved in chloroform, the solvent was removed by a rotary evaporator to form a uniform film, and an aqueous phase solution was added for hydration. The mass ratio of the aqueous phase to the film was 1:4; (2) The temperature was controlled at 50 °C and the pH value was 7.

0. Ultrasonic treatment was performed at 20-40 kHz for 15 min and the nanovesicle suspension was cooled at 4 °C to 10 °C. (3) Obtaining single-layer nanovesicles with a particle size between 100 and 150 nanometers by extrusion; (4) Spread the cow dung out to dry, evaporate some of the water, add dry high-carbon auxiliary materials to absorb water and increase porosity, adjust the moisture content to 50%-60%, increase the carbon-nitrogen ratio to 25-30:1, and keep the pH value between 6.5-7.5; (5) In the initial stage of cow dung composting, the prepared nanocapsules are evenly sprayed or mixed into the cow dung at a rate of 1% to 5% of the total mass of the compost raw materials and piled into a strip shape; the compost temperature is controlled between 40-60°C, and the compost is turned regularly to maintain the aeration of the compost, so as to promote the degradation of organic matter and the effective utilization of nitrogen; (6) Pile the treated cow dung into piles for composting and fermentation; control the composting temperature at 40-60°C, the fermentation time is 30-45 days, and turn the pile every 5-7 days; The aqueous solution is a phosphate buffer solution containing nitrogen fertilizer, humic acid is dissolved in the phosphate buffer solution, and zeolite is dispersed uniformly in the aqueous solution by mechanical stirring or ultrasonic wave; The humic acid accounts for 2% of the total mass of the phospholipids, and the zeolite accounts for 3% of the total mass of the phospholipids; The nitrogen fertilizer is urea and ammonium sulfate, and the component ratio is: Urea: 0.5% of the total mass of the aqueous solution; Ammonium sulfate: 1% of the total mass of the aqueous solution; The phosphate buffer composition is: Sodium dihydrogen phosphate (NaH2PO4): 8 g / L; Disodium hydrogen phosphate (Na2HPO4): 1.15 g / L; Sodium chloride (NaCl): 137 mM; Potassium chloride (KCl): 2.7 mM; The pH is 7.

2. The method according to claim 1, characterized in that The phospholipid is a mixture of distearoylphosphatidylcholine (DSPC) and distearoylphosphatidylglycerol (DSPG), and the mass ratio of DSPC:DSPG is 2:

1.

3. The method according to claim 1, characterized in that The extrusion method in step (3) uses a high-pressure extruder and selects a polycarbonate membrane with a pore size of 100 nanometers; The ultrasonically treated nanovesicle suspension is placed in the syringe of the extruder, and pressure is applied manually or by a pump to pass the suspension through the pore size of the polycarbonate membrane. To ensure the consistency and uniformity of the particle size, the suspension is extruded through the membrane of the same pore size multiple times, and 5 to 10 cycles of extrusion are performed.

4. The method according to claim 1, characterized in that The mechanical stirring condition is 1000-1500 rpm, 20-30 min; the ultrasonic condition is 20-40 kHz, 5-15 min.

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