Agricultural organic waste composting method for nitrogen fixation and emission reduction and application thereof

Abstract

The present application belongs to the field of organic matter composting, and particularly relates to a nitrogen-fixing and emission-reducing agricultural organic waste composting method and application thereof. The specific technical scheme is as follows: a composting method, wherein biochar is uniformly mixed with organic matter to be composted to obtain composting raw materials, yeast is added to the composting raw materials, composting is performed, and methanotrophs are added in the middle of composting. The present application combines the use of modified substrate, modified biochar and various microorganisms to realize organic matter composting, can effectively reduce the C and N overflow in the composting process, fix more carbon and nitrogen in the composting end product, and not only reduces environmental pollution, but also improves the quality of the composting end product.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of organic matter composting, and particularly relates to a nitrogen-fixing and emission-reducing agricultural organic waste composting method and application thereof. BACKGROUND

[0002] With the rapid development of the livestock, breeding, planting and other industries, the production of organic waste such as straw and livestock and poultry manure is also increasing. At present, the humification and harmless treatment of such waste is generally realized by the way of aerobic composting. However, CO2, CH4, N2O and NH3 gases are produced in aerobic composting, which not only leads to the loss of C and N elements and reduces the fertility, but also causes air pollution and aggravates the greenhouse effect.

[0003] The prior art generally reduces the loss of carbon and nitrogen during composting by adding microorganisms, composite acid, low-concentration iron salt and the like to the pile, but these methods have problems such as high difficulty in obtaining microorganisms, difficulty in quickly occupying a dominant ecological niche in composting, complex raw material ratio, small concentration operability and high cost.

[0004] In summary, it is urgent to develop a carbon and nitrogen preserving waste organic matter composting method which has simple and readily available raw materials and high operability. SUMMARY

[0005] The application aims to provide a nitrogen-fixing and emission-reducing composting method for resource utilization of agricultural waste organic matter and application thereof.

[0006] To achieve the above application purposes, the technical solution adopted by the application is as follows: a composting method, wherein biochar is mixed with organic matter to be composted to obtain composting raw materials, yeast is added to the composting raw materials, and methanotrophs are added to the composting midway.

[0007] Preferably, the biochar is modified biochar, and the modification method comprises: soaking the biochar in an NH3-NH4Cl buffer solution.

[0008] Preferably, the C / N ratio of the composting raw materials is adjusted to 25-30:1, the water content is adjusted to 55%-60%, and the pH is adjusted to 6.0-8.0 by using a substrate, and then the yeast is added.

[0009] Preferably, the substrate is straw, and the straw is modified straw, and the modification method comprises: soaking the straw in a fumaric acid solution.

[0010] Preferably, the method comprises the following steps:

[0011] (1) adding biochar to organic matter to be composted, mixing uniformly to obtain composting raw materials;

[0012] (2) the C / N ratio of the matrix is adjusted to 25-30:1, the water content is 55-60%, and the pH is 6.0-8.0;

[0013] (3) the yeast is evenly spread on the surface of the compost raw material, and is evenly stirred to perform aerobic composting;

[0014] (4) when the methane production in the compost is increased to 120% of the production of the previous day or more, the methanotrophs are added.

[0015] Preferably, the biochar in step (1) is modified biochar, and the modification method comprises: soaking the biochar in an NH3-NH4Cl buffer solution.

[0016] Preferably, the mass of the biochar is 10-15% of the mass of the organic matter to be composted.

[0017] Preferably, the matrix in step (2) is modified matrix, and the modification method comprises: soaking the matrix in a fumaric acid solution.

[0018] Preferably, the preparation method of the fumaric acid solution is: dissolving fumaric acid crystals in water; and the addition amount of the fumaric acid crystals is 10-12% of the fresh weight of the matrix.

[0019] Preferably, in the composting, the turning frequency is 4-7 times per day, the ventilation amount is 3-4 times per day, and the ventilation rate is 0.2 L / kg·min.

[0020] The present application has the following beneficial effects:

[0021] The present application realizes composting of organic matter by using modified matrix, modified biochar and various microorganisms, which can effectively reduce C and N overflow in the composting process, fix more carbon and nitrogen in the compost end product, reduce environmental pollution, and improve the quality of the compost end product.

[0022] The present application uses fumaric acid to modify the matrix for the first time. Fumaric acid is an important intermediate substance in the tricarboxylic acid cycle, which can be directly utilized by microorganisms, promote the rapid colonization of microorganisms in the compost, accelerate the growth and reproduction speed, and occupy the dominant ecological niche in the compost more quickly. Meanwhile, fumaric acid can also act as an electron acceptor, generate propionic acid through the succinic acid decarboxylation and acrylic acid pathways, consume H2 and formic acid, thereby reducing CH4 production. Fumaric acid can also provide an acidic environment and has the characteristics of direct aminoization, further reducing NH3 emission and increasing the nitrogen content in the fertilizer. Fumaric acid can also improve the utilization rate of H2 and formic acid by microorganisms other than methanogens, thereby reducing the methane production rate. In addition, fumaric acid can also shorten the composting time of substrates such as straw, so that the humification requirement can be met more quickly.

[0023] The biochar is added in the pile body used in the present application. The biochar has abundant pore structure, plays a supporting role in the pile body, can reduce the density of the pile body, and improve the ventilation. The specific surface area, surface alkaline functional groups and surface metal oxides of the biochar are all related to the adsorption of NO3 - -N, and the cation exchange capacity (CEC) dominates the adsorption of NH4 + -N, thereby reducing the nitrogen in the pile body in the form of ammonia or nitrous oxide, and playing a nitrogen preservation role. Moreover, a large number of hydroxyl, carboxyl groups and conjugated aromatic structures exist on the surface of the biochar, which can passivate heavy metal ions through the action of electrostatic adsorption and ion exchange.

[0024] The present application modifies the biochar by using NH3-NH4Cl buffer solution. The biochar modified by ammonium chloride can promote the growth of methanotrophs and nitrifying bacteria in the compost, promote carbon and nitrogen cycles, reduce the generation of odor and methane during the composting process, and improve the compost quality. Moreover, the ammonium ion in the ammonium chloride can be utilized by the fermenting microorganisms on the one hand to promote the growth of the microorganisms, and on the other hand to increase the N content in the final product of the compost, which can provide nitrogen elements for crops after being applied into the soil. In addition, the chloride ion can inhibit the activity of nitrifying bacteria, thereby retaining the ammonium ion in the pile body to a greater extent. Nitrate and nitrite can act as electron acceptors to compete for reducing equivalents with the methanogenic process, and nitrite can also reduce the methane production rate by inhibiting the electron carrier system of methanogens, thereby further reducing the generation and overflow of methane.

[0025] The present application adds yeast bacteria in the compost. The yeast bacteria can promote the growth and development of acetogenic bacteria in the pile body, consume hydrogen in the pile body, thereby limiting the growth of methanogens due to insufficient substrate and reducing the production of methane. In addition, the yeast bacteria can also promote the conversion of nitrogen-containing organic matter in the pile body to water-soluble organic nitrogen, shorten the composting time, and achieve the effect of nitrogen preservation.

[0026] The present application uses M. capsulatus as methanotrophs. The microorganism can produce a membrane-bound enzyme called methane monooxygenase (pMMO), which can obtain energy for its own growth by oxidizing methane. The methanotrophs can first oxidize methane to formic acid or formaldehyde in their bodies, and then different subsequent products appear according to the types of methanotrophs. The tetrahydropyrimidine generated by the methanotrophs can form a thick hydration layer around the biological macromolecules, enhancing the tolerance of cells to various stresses (such as high salt, heat, dryness and freezing); the succinic acid generated as an intermediate product of the TCA cycle can improve the metabolic efficiency of the microorganisms, thereby improving the degradation of organic matter in the compost, increasing the composting degree and shortening the composting time. The methanotrophs can also convert the organic matter in the compost to small molecular organic matter, and the yeast bacteria can utilize the small molecular organic matter to better grow and metabolize. The cooperation and complementation between the bacterial agents further promote the decomposition and degradation of the compost raw materials. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The flow chart of the present application. DETAILED DESCRIPTION

[0028] The present application provides a new composting method using organic matter (preferably waste organic matter), which comprises the following steps:

[0029] 1. Cut or crush the fermentation substrate such as straw, preferably cut into small pieces of 5-8 cm, and soak in a fumaric acid solution for 8-12 h to allow the substrate to fully absorb the fumaric acid solution, then take it out and air dry to obtain a modified substrate. The substrate serves to reduce the bulk density of the pile, increase the aeration, and adjust the C / N ratio of the pile. The modified substrate also has a promoting effect of fumaric acid on composting and a combined effect of fumaric acid and the substrate. The fumaric acid solution can be obtained by dissolving fumaric acid crystals in water; the amount of fumaric acid crystals added is 10%-12% (w / w) of the fresh weight of the fermentation substrate.

[0030] 2. Dry the waste organic matter such as straw that can be used to prepare biochar at room temperature, crush and sieve it, preferably through an 80-mesh sieve, and then add it to a biomass pyrolysis furnace for low-oxygen carbonization at a temperature of 300-500°C with a heating rate of 10°C / min and a holding time of 1 h to obtain biochar.

[0031] 3. Add solid ammonium chloride to ammonia water, and the mass ratio of ammonia water to ammonium chloride is preferably 1.74:1 to prepare an NH3-NH4Cl buffer solution with a pH of about 9.0. Add the biochar prepared in step 2 to the NH3-NH4Cl buffer solution, and after oscillation at room temperature at 180 r / min for 4-8 h, take it out to obtain modified biochar.

[0032] The modified biochar needs to be added to the organic matter (preferably waste organic matter) to be composted, such as livestock and poultry manure, within 2 h after the modification is completed, and mixed evenly to obtain compost raw materials. The preferred scheme is that the mass of the modified biochar added is 10%-15% of the mass of the organic matter to be composted.

[0033] 4. Adjust the C / N ratio of the compost raw materials to 25-30:1, the moisture content to 55%-60%, and the pH to 6.0-8.0 using the modified substrate. Sprinkle the yeast evenly on the surface of the compost raw materials and mix well to carry out aerobic composting. The preferred amount of yeast added is 0.01-0.05 kg per ton of organic matter to be composted.

[0034] The yeast can promote the decomposition and fermentation of organic matter, promote the maturation of the pile, and limit the activity and effect of methanogens. Preferably, the yeast is Pichia stipitis, which is purchased from the China Institute of Food Fermentation Industry and has a preservation number of CICC1960. In addition to the general effects of yeast, CICC1960 can better degrade lignocellulose in the pile, further improving the composting effect and product quality.

[0035] 5. Adding yeast at the beginning of composting can help quickly establish the dominance of the microbial community, facilitate the rapid increase of the pile temperature in the early fermentation stage, and help the production of organic acids. With the passage of time, oxygen is continuously consumed in the pile and anaerobic areas are generated, and the methane production of the pile is greatly increased. At this time, Methylococcus capsulatus is uniformly sprayed on the surface of the compost raw materials, and after uniform turning, composting is continued. The preferred amount of addition is 20-30 g of Methylococcus capsulatus per ton of organic matter to be composted. The addition time of Methylococcus capsulatus can be determined according to the turning frequency and / or the methane production. When the methane production is greatly increased (for example, increased to more than 120% of the production of the previous day), or when the first turning is performed (for example, the turning frequency is 4 times / day, and the Methylococcus capsulatus is added on the 5th day of composting, i.e., the first turning), the Methylococcus capsulatus is added.

[0036] 6. In composting, the turning frequency is 4-7 times / day, the ventilation amount is 3-4 times / day, and the ventilation rate is 0.2 L / kg·min.

[0037] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. If not specifically indicated, the technical means used in the embodiments are conventional means familiar to those skilled in the art. The obtained data are all average values obtained after at least 3 repetitions, and the data obtained in each repetition are all valid data.

[0038] Example: Comparison of composting methods and effect display

[0039] 1. Set up experimental groups, and set up 3 repetitions for each group. The experimental group setting method is as follows: select wheat straw as the fermentation substrate. Cut the wheat straw into 5-8 cm straw segments, soak them in a fumaric acid solution for 10 h to make them fully absorb the fumaric acid solution. The fumaric acid solution is obtained by dissolving fumaric acid crystals in water, and the addition amount of fumaric acid crystals in each group is shown in Table 1.

[0040] After soaking is completed, the wheat straw is taken out, dried at room temperature, crushed and passed through an 80-mesh sieve, and then added to a biomass pyrolysis furnace. The pyrolysis temperature is shown in Table 1, the heating rate is 10℃ / min, and the holding time is 1 h to obtain a modified substrate.

[0041] A solid ammonium chloride was added to the ammonia water to prepare a NH3-NH4Cl buffer solution with pH = 9.0. The wheat straw was crushed and carbonized to obtain biochar. The biochar was crushed and washed with deionized water to remove the surface dust, and then added to the NH3-NH4Cl buffer solution. After oscillation at room temperature at 180 r / min for 6 h, the modified biochar was obtained. The modified biochar was added to the cow dung (to be composted organic matter) within 2 h, and mixed uniformly.

[0042] The C / N ratio of the compost raw material was adjusted to 25:1 using the modified substrate, the moisture content was 60%, and the pH was 8.0. The yeast was uniformly sprayed on the surface of the compost raw material, and the aerobic composting was started after uniform mixing. The source of the yeast is shown in Table 1. The yeast strain is CICC1960.

[0043] When the composting was carried out to the 5th day, the methanotrophic bacteria Methylococcus capsulatus was uniformly sprayed on the surface of the compost raw material, and the composting was continued after uniform mixing. The source of the bacteria Methylococcus capsulatus is shown in Table 1. When not specifically stated, the Methylococcus capsulatus is ATCC 19069.

[0044] During the composting process, the turning frequency was 7 times / day, the forced ventilation amount was 4 times / day, and the ventilation rate was 0.2 L / kg·min. At the same time, a blank control group CK was set, without adding any additives, directly using the cow dung composting, using the unmodified substrate to adjust the C / N ratio of the cow dung to 25:1, the moisture content was 60%, and the pH was 8.0; the management conditions during the composting were the same.

[0045] In Table 1, “\” indicates that the corresponding condition is not set; the fumaric acid crystal addition amount is based on the fresh weight of the wheat straw (%); the bacteria dosage is the amount used per ton of cow dung; and the modified biochar addition amount is based on the mass of the cow dung (%).

[0046] Table 1 Comparison table of conditions and parameters of experimental groups and control groups

[0047]

[0048]

[0049] When the temperature of the compost in each group stabilized at room temperature level or close to the ambient temperature, it was the composting maturity period. The total ammonia and methane accumulation amounts of each group of composting from the start of composting to the maturity period were collected and determined, and the results are shown in Table 2.

[0050] Table 2 Comparison table of composting results of each group

[0051]

[0052]

[0053] The above embodiments are only to describe the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification, variation, modification, and replacement of the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method of composting, characterised by: Biochar is mixed with organic matter to be composted to obtain composting raw materials. Yeast is added to the composting raw materials for composting. Methanophilic bacteria, specifically *Methylcoccus capsulatum*, are added during the composting process. Methylococcus capsulatus ATCC 19069; The biochar is modified biochar, and the modification method comprises: soaking the biochar in an NH3-NH4Cl buffer solution. The C / N ratio of the compost raw material is adjusted to 25-30:1, the moisture content is adjusted to 55%-60%, and the pH is adjusted to 6.0-8.0 by using a substrate, and then yeast is added; the substrate is straw, and the straw is modified straw, and the modification method comprises: soaking the straw in a fumaric acid solution.

2. The composting method of claim 1, wherein: The method comprises the following steps: (1) adding biochar to the organic matter to be composted, and mixing uniformly to obtain compost raw material; (2) adjusting the C / N ratio of the compost raw material to 25-30:1, the moisture content to 55%-60%, and the pH to 6.0-8.0 by using a substrate; (3) uniformly spreading yeast on the surface of the compost raw material, and mixing uniformly to carry out aerobic composting; (4) when the methane yield in the compost is increased to 120% or more of the yield of the previous day, adding methanotrophs.

3. The composting method of claim 2, wherein: The biochar in step (1) is modified biochar, and the modification method comprises: soaking the biochar in an NH3-NH4Cl buffer solution.

4. The composting method of claim 2 or 3, wherein: The biochar is added in an amount of 10%-15% of the mass of the organic matter to be composted.

5. The composting method of claim 2, wherein: The substrate in step (2) is modified substrate, and the modification method comprises: soaking the substrate in a fumaric acid solution.

6. The composting method of claim 5, wherein: The preparation method of the fumaric acid solution is: dissolving fumaric acid crystals in water; and the addition amount of the fumaric acid crystals is 10%-12% of the fresh weight of the substrate.

7. The composting method of claim 2, wherein: In the compost, the turning frequency is 4-7 times per day, the ventilation amount is 3-4 times per day, and the ventilation rate is 0.2 L / kg·min.

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