Composting method with rotary intermittent air supply

Abstract

The invention relates to a rotary intermittent air supply composting method, which comprises the following steps: S1, material preparation: preparing a composting raw material fish manure, and adjusting the carbon nitrogen ratio and the water content of the raw material; s2, fermentation: adding the compost raw materials into a rotary compost box for fermentation, intermittently supplementing air for the rotation of the compost box, rotating for 4-8 minutes each time, introducing oxygen while rotating for 25-45 minutes at intervals, and ending the fermentation for 15-18 days; the method is convenient to operate and low in cost, the EC value of a compost product prepared through the rotary intermittent air supply composting method is smaller than 4000 [mu] s / cm, the E4 / E6 value is lower than that of a contrast, compost maturity is facilitated, the fermentation period is short, greenhouse gas emission is small, and the environment is protected.

Description

Technical Field

[0001] The invention relates to the technical field of composting, in particular to a composting method with rotating intermittent aeration. Background Art

[0002] Fish manure (FS) is an organic waste produced during the aquaculture process. It is rich in nutrients such as nitrogen, phosphorus, and potassium, and can be used as an organic fertilizer for plant growth. However, fish manure is quite different from traditional cow manure, pig manure, etc. Fish manure is a typical low C / N ratio organic matter. As a fertilizer, low C / N ratio organic matter has a high nitrogen content and a fast nutrient release rate. It can provide a large amount of nutrients for crops in a short time to meet the needs of crop growth in the early stage. However, due to the rapid release of nutrients, some nitrogen may be lost to the environment without being absorbed by crops, causing nutrient waste and environmental pollution, and affecting the long-term stable growth and final yield of crops. At present, the method of using fish manure as raw material for composting is mainly anaerobic composting, but anaerobic composting has a long fermentation cycle, poor compost product quality, low seed germination rate, heavy odor, and high greenhouse gas emissions, which seriously pollutes the environment. Therefore, it is very important to choose a suitable fish manure composting method.

[0003] In addition to anaerobic composting, current composting technology also includes aerobic composting, which is the main method for resource treatment of organic waste. Existing aerobic composting methods mostly use continuous aeration, which is costly and not conducive to compost maturity. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a composting method with rotary intermittent aeration.

[0005] The technical solution of the present invention is:

[0006] A composting method with rotary intermittent aeration comprises the following steps:

[0007] S1. Material preparation: prepare fish manure as compost raw material and adjust the carbon-nitrogen ratio and moisture content of the raw material;

[0008] S2. Fermentation: Add the compost raw materials into a rotating composting box for fermentation. The composting box rotates and replenishes air intermittently. Each rotation time is 4-8 minutes. Oxygen is introduced while rotating. The rotation interval time is 25-45 minutes. Fermentation is completed after 15-18 days.

[0009] Furthermore, the characteristics of the composting raw material fish manure are: COD 5.32±0.32g / kg, TN 0.77±0.13g / kg, NH4 + -N is 324-365g / kg, and the carbon-nitrogen ratio is (8-10):1.

[0010] Furthermore, wheat straw was used in S1 to adjust the carbon-nitrogen ratio of fish manure.

[0011] Furthermore, the carbon-nitrogen ratio of the fish feces in S1 after adjustment is (20-30):1.

[0012] Furthermore, the adjusted moisture content of the fish feces in S1 is 50-60%.

[0013] Furthermore, the rotation speed of the composting box in S2 is 25-35 rpm.

[0014] Furthermore, the ventilation portion of the rotary composting box is located in the middle of the side wall of the box.

[0015] Compared with the prior art, the present invention has at least the following advantages:

[0016] The invention relates to a composting method with rotary intermittent aeration. The method uses fish manure as a composting raw material, uses straw to adjust the carbon-nitrogen ratio of a pile, and rotates a compost box for intermittent aeration during a fermentation process. The rotary aeration time is 5 minutes, and the interval time each time is 25-45 minutes. Experiments have confirmed that the rotary intermittent aeration helps to increase the temperature of the pile, prolong the high temperature maintenance time of the pile, and improve the stability of the temperature of the pile; the EC value of a rotary aeration treatment group is less than 4000 μs / cm, and the E4 / E6 value is lower than that of A and E treatment groups, indicating that the rotary intermittent aeration is more conducive to the maturity of the compost; by testing the seed germination rate, it is found that the rotary intermittent aeration is conducive to the maturity of the compost, is conducive to seed germination, and has low toxicity; and by testing the greenhouse gas emission, it is found that the greenhouse gas emission of the intermittent rotary aeration group is less, which is conducive to environmental protection; finally, the compost microbial community structure is detected during composting, and it is found that the relative abundance of Proteobacteria in the intermittent rotary aeration group is significantly increased, which is conducive to the subsequent degradation of organic matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention, the drawings required for use in the specific embodiments or the description of the prior art will be briefly introduced below.

[0018] Figure 1 This is the temperature change of the pile under different air supply modes in the test example 1 of the present invention;

[0019] Figure 2 This is the change of pH value of the pile under different air supply modes in the test example 1 of the present invention;

[0020] Figure 3 This is the change of EC and E4 / E6 values ​​of the pile under different air supply modes in the test example 1 of the present invention;

[0021] Figure 4 This is the germination rate of seeds of the compost product of Test Example 2 of the present invention;

[0022] Figure 5The greenhouse gas emissions of the stack under different air supply modes in Test Example 3 of the present invention;

[0023] Figure 6 This is the change of microbial community structure at the pile gate level under different air supplementation methods in Test Example 4 of the present invention;

[0024] Figure 7 These are the biomarkers of key microbial groups at the pile body level under different gas supplementation methods in Test Example 4 of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Technicians in this field can make some non-essential improvements and adjustments to the present invention based on the above application content.

[0026] The present invention provides a general and / or specific description of the materials and test methods used in the experiment. The test methods or test methods involved are all conventional methods unless otherwise specified; the reagents or instruments used are all conventional products available on the market, prepared or used in a conventional manner, unless the manufacturer is specified.

[0027] The rotary composting box in the present invention adopts the composting box in the invention patent with publication number CN 117865736 A.

[0028] The present invention uses FS shown in Table 1 as raw material, adjusts the FS carbon-nitrogen ratio to 25:1 according to m(FS):m(wheat straw)=2:3, the total mass of the compost material is 10kg, and tap water is added through a spray device to control the moisture content of the compost body at 55%.

[0029] Table 1 FS characteristics of raw materials

[0030]

[0031] Embodiment 1

[0032] Compost materials were added into the compost box, and the compost box was circulated in a manner of rotating for 5 minutes while replenishing air and standing for 25 minutes. The rotation speed of the compost box was 30 rpm, and the air inlet was set in the middle of the side of the compost box. This embodiment is hereinafter referred to as treatment group B.

[0033] Embodiment 2

[0034] Compost materials were added into the compost box, and the compost box was circulated in a manner of rotating for 5 minutes while replenishing air and standing for 35 minutes. The rotation speed of the compost box was 30 rpm, and the air inlet was set in the middle of the side of the compost box. This embodiment is hereinafter referred to as the C treatment group.

[0035] Embodiment 3

[0036] Compost materials were added into the compost box, and the compost box was circulated in a manner of rotating for 5 minutes while replenishing air and standing for 45 minutes. The rotation speed of the compost box was 30 rpm, and the air inlet was set in the middle of the side of the compost box. This embodiment is hereinafter referred to as the D treatment group.

[0037] Comparative Example 1

[0038] The compost material was added into the compost bin, and the compost bin was not rotated and aerated. This comparative example is hereinafter referred to as treatment group A.

[0039] Comparative Example 2

[0040] The compost material was added into the compost bin, the compost was turned manually every 2 hours, and air was continuously added mechanically. This comparative example is hereinafter referred to as treatment group E.

[0041] Test Example 1: Effects of different gas supply methods on pile quality

[0042] 1.1 Effects of different air supply methods on pile temperature changes

[0043] Temperature is an important parameter for the maturity and stability of composting. The increase in temperature helps to accelerate the decomposition of organic matter and promote the growth of microorganisms. In order to evaluate the effect of aeration on the temperature of the compost, this test case monitored the temperature changes of the compost during the composting process.

[0044] The results are as follows Figure 1 As shown in the figure, it can be seen that the composting temperature of each treatment group shows a change pattern of first increasing and then decreasing; as the composting progresses, each treatment group reaches its respective maximum temperature on the 10th, 8th, 9th, 9th and 7th days, which are 53.52℃, 60.37℃, 56.75℃, 56.34℃ and 59.71℃ respectively; studies have shown that pathogenic microorganisms can be inactivated by maintaining the pile temperature above 55℃ for more than 3 days. In this test example, treatment groups A and E do not meet the requirements. Treatment group B maintains a high temperature environment above 55℃ for 3 days, treatment group C maintains it for 3 days, and treatment group D maintains it for 4 days. Treatment group D maintains high temperature for the longest time, which indicates that pathogenic microorganisms in the compost under the conditions of rotation and intermittent aeration are effectively inhibited. At the same time, the temperature of the B, C, and D treatment groups did not fluctuate significantly during the entire composting process. This is related to the fact that the composting box rotates and replenishes air while realizing the flipping of the pile, which increases the porosity and free air space of the pile, avoiding the compaction effect caused by long-term composting and the inhibition of microbial metabolic activity and heat production caused by uneven moisture distribution. In summary, rotating intermittent aeration helps to increase the temperature of the pile, prolong the high temperature maintenance time of the pile, and improve the stability of the temperature of the pile.

[0045] 1.2 Effects of different gas supplementation methods on pH changes

[0046] pH has an important influence on the life activities of microorganisms and the preservation of nitrogen during composting. The pH changes of each treatment group during composting are as follows: Figure 2 shown.

[0047] As can be seen from the figure, the pH of treatment group A gradually decreased during the entire composting process, the pH of treatment groups B, C and D decreased first and then increased during the entire composting process, and the pH of treatment group E decreased first, then increased, and then decreased again until it stabilized. Among them, the pH of treatment group B gradually decreased to a minimum value of 5.64 on the 6th day, and the pH of treatment groups C and D decreased to minimum values ​​of 5.87 and 5.72 on the 5th day. The minimum value of pH in treatment group B was lower than that in treatment groups C and D. As the composting continued, the pH of treatment groups B, C and D rose again until it stabilized. From the 10th day onwards, the pH of treatment groups B, C and D did not change significantly and remained stable between 7.54-8.13. Comparing the pH of treatment groups B, C, D and E at the end of composting, it can be seen that the longer the rotation time interval, the higher the pH value at the end of composting, which is consistent with the inhibition of NH4 + It is related to the conversion of -N to NH3 and the conversion of NH3 to the atmospheric environment.

[0048] 1.3 Effects of different gas supplementation methods on EC and E4 / E6 values

[0049] EC (EC value of compost refers to its electrical conductivity, i.e. soil electrical conductivity, which is used to determine the concentration of water-soluble salts in compost) can reflect the salinity and maturity of compost and evaluate the potential phytotoxicity of compost products for crop cultivation. When the EC value exceeds 4000μs / cm, it may cause harm to plant growth. In order to evaluate the potential phytotoxicity of compost products, this test case sampled and monitored the EC of compost products during the composting process. The results are as follows: Figure 3 As shown in A. Four days before composting, the EC values ​​of treatment groups B and E increased significantly, while those of groups A, C, and D decreased slowly. At the end of composting, the EC values ​​of each treatment group were 1542μs / cm, 1218μs / cm, 1436μs / cm, 1467μs / cm, and 1339μs / cm, respectively, all less than 4000μs / cm.

[0050] The E4 / E6 value is the ratio of the absorbance of compost products at 465nm and 665nm. It is usually an important indicator of the quality or condensation degree and aromatization degree of humic acid. It decreases with the increase of condensation degree of humic acid molecules and is one of the criteria for judging the maturity of compost. Figure 3As shown in Figure B, it can be seen that during the composting process, the E4 / E6 of each group showed a trend of first increasing and then decreasing; at the end of composting, the E4 / E6 values ​​of each treatment group were 2.43, 2.13, 2.04, 1.96 and 2.17, respectively. The E4 / E6 of treatment groups B, C and D were lower than those of treatment groups A and E, indicating that rotating intermittent aeration is more conducive to the maturity of compost.

[0051] Test Example 2 Effects of different air supply methods on seed germination rate

[0052] The seed germination rate reflects the toxicity of compost to plants. This test case compared the seed germination rate of compost products under 5 different rotary aeration methods. The results are as follows: Figure 4 As shown in the figure, the seed germination rates of the AE treatment groups were 47.42%, 56.44%, 66.89%, 72.76% and 74.32%, respectively, indicating that the rotating intermittent aeration method is conducive to the maturity of the compost and seed germination.

[0053] Test Example 3 Effects of different aeration methods on greenhouse gas emissions during composting

[0054] This test example tests the content of N2O, NH3, CH4, and CO2 in each group.

[0055] N2O is an important greenhouse gas. This test case monitored the amount of N2O produced during the composting process. The results are as follows: Figure 5 As shown in A. As can be seen from the figure, the N2O emissions of each treatment group increased significantly in the early stage of composting, and the N2O produced in the early stage of composting accounted for more than 75% of the gas production in the entire composting cycle. When the composting entered the high temperature stage, the N2O production of each treatment group decreased to varying degrees. Among them, the E treatment group had the highest N2O production, and the N2O produced by the intermittent gas supplement group was B>C>D. The longer the interval between gas supplements, the lower the N2O accumulation.

[0056] The process of NH3 production during composting is as follows Figure 5 As shown in Figure B. As can be seen from the figure, NH3 mainly appeared in the middle and high temperature period of each composting treatment group. Compared with the continuous aeration treatment group E, the cumulative emission of NH3 in the intermittent aeration groups B, C, and D decreased by 27.3%-47.9%, and the generation of NH3 in each intermittent aeration treatment group was B>C>D, which decreased with the increase of the rotation interval time.

[0057] The production process of CH4 during composting is as follows Figure 5C. As shown in the figure, CH4 production is mainly concentrated in the first 4 days after the start of composting. The CH4 production of each treatment group within 4 days accounted for 72.22%, 77.94%, 77.40%, 79.17% and 56.93% of the total emissions, respectively. As the composting continued, the CH4 production decreased significantly. At the end of composting, the cumulative CH4 production of each treatment group was 126.32mg / kg·DM, 204.12mg / kg·DM, 177.24mg / kg·DM, 144.51mg / kg·DM and 332.35mg / kg·DM, respectively. The CH4 production of the E treatment group was the highest. The CH4 produced by the intermittent aeration group was B>C>D, respectively. The longer the interval between aeration, the lower the accumulation of N2O.

[0058] CO2 is mainly produced when microorganisms use oxygen to decompose organic matter. The process of CO2 production during composting is as follows: Figure 5 D. As shown in the figure, in the first 7 days of composting, except for the A treatment group, the CO2 production did not increase significantly, and the cumulative CO2 production of the other treatment groups was 109.43g / kg·DM, 478.53g / kg·DM, 372.96g / kg·DM, 327.98g / kg·DM and 578.13g / kg·DM respectively. With the degradation of organic matter in the compost and the decrease of the pile temperature, the CO2 yield decreased significantly. At the end of composting, the E treatment had the highest cumulative CO2 production, and the D treatment group had the lowest cumulative CO2 production, which indicates that extending the gas supplementation interval helps to reduce the production of CO2 during the composting process.

[0059] The cumulative greenhouse gas emissions of each treatment group are shown in Table 1, which are 109.69 g / kg·DM, 479.03 g / kg·DM, 373.42 g / kg·DM, 328.34 g / kg·DM, and 578.88 g / kg·DM, respectively.

[0060] Table 1 Cumulative gas emissions of each treatment group (unit: g / kg·DM)

[0061]

[0062] Test Example 4 Effects of different aeration methods on the structure of composting microbial communities

[0063] This test case further analyzed the microbial community structure during the high-temperature composting stage under different aeration conditions. Figure 6It can be seen that the main dominant phyla in the high temperature stage are Proteobacteria, Bacteroidetes and Firmicutes, with a total relative abundance of more than 98%. Among them, there was no significant difference in the microbial community structure composition at the phylum level in the three treatment groups with intermittent aeration. Compared with the A treatment group, the relative abundance of Proteobacteria in the B, C, and D treatment groups increased significantly, while the relative abundance of Bacteroidetes and Firmicutes decreased significantly. Proteobacteria mainly include various aerobic, anaerobic and facultative anaerobic bacteria, which are widely present in the waste composting process. They are key microorganisms that drive nitrogen nitrification reactions and can decompose macromolecular compounds into HS precursors, which is beneficial to the subsequent degradation of organic matter.

[0064] In this test case, LEfse analysis was used to determine the biomarkers of key microbial groups at the genus level in the compost bacterial community in different treatment groups from the warming stage (Day 3) to the high temperature stage (Day 7) and the mature stage (Day 16), such as Figure 7 As shown in the figure, with the extension of composting time, the number of biomarkers in all treatment groups gradually increased, indicating that the differences in the response of bacterial communities to different aeration strategies gradually increased. At the same time, all identified bacterial biomarkers mainly belonged to the phyla Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes.

[0065] Ruminococcus and Atopobium are common compost markers in the composting process. They can degrade carbohydrates and lignocellulose to form small molecules by secreting hydrolytic enzymes, thus realizing the humification of organic waste. Pseudoramibacter_Eubacterium exists in the E treatment group, which is a typical denitrifying bacterium and may cause the production of N2O. This is consistent with the conclusion that the E treatment group had the highest N2O production in the mesophilic composting stage of Test Example 3.

[0066] The main marker microorganisms in the high temperature stage of composting include Caldicoprobacter, Corynebacterium, etc. Studies have shown that Caldicoprobacter can decompose substances such as cellulose and xylan through enzymatic hydrolysis under aerobic and anoxic conditions. At the same time, Pseudoramibacter_Eubacterium still exists in the E treatment group, which will lead to a continuous increase in the production of N2O. Compared with the E treatment group, the abundance of facultative anaerobic microorganisms such as Atopobium and VadinCA02 in the intermittent aeration treatment group increased significantly due to the limitation of oxygen content in the pile. These microorganisms also play an important role in the degradation of proteins, carbohydrates and lignocellulose in organic waste.

[0067] In the mature composting stage, the number of bacterial markers in the compost continued to increase. At the same time, different aeration conditions significantly affected the succession of bacterial communities in the mature composting stage, and biomarkers in the high temperature stage of the composting were identified in the mature composting stage. The abundance of biomarkers of lignin and fat decomposition such as Actinomycetes, Clostridium, Tepidimicrobium, and Atopobium in the D treatment group was much higher than that in the B and C treatment groups, which can accelerate the formation of HS precursors, promote the formation of HA in the mature composting stage, and reduce the mineralization rate of organic matter and the production of greenhouse gases (CO2 and CH4). This is consistent with the conclusion that the D treatment group in test case 5 had the lowest cumulative emissions of CH4 and CO2.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A composting method with rotary intermittent aeration, characterized in that: The following steps are involved: S1. Material preparation: prepare fish manure as compost raw material and adjust the carbon-nitrogen ratio and moisture content of the raw material; S2. Fermentation: Add the compost raw materials into a rotating composting box for fermentation. The composting box rotates and replenishes air intermittently. Each rotation time is 4-8 minutes. Oxygen is introduced while rotating. The rotation interval time is 25-45 minutes. Fermentation is completed after 15-18 days.

2. The composting method according to claim 1, characterized in that: The characteristics of the compost raw material fish manure are: COD 5.32±0.32g / kg, TN 0.77±0.13g / kg, NH4 + -N is 324-365g / kg, and the carbon-nitrogen ratio is (8-10):

1.

3. The composting method according to claim 2, characterized in that: Wheat straw was used in S1 to adjust the carbon-nitrogen ratio of fish manure.

4. The composting method according to claim 3, characterized in that: The carbon-nitrogen ratio of fish feces in S1 after adjustment is (20-30):

1.

5. The composting method according to any one of claims 1 to 4, characterized in that: The moisture content of the fish feces in S1 is adjusted to 50-60%.

6. The composting method according to claim 5, characterized in that: The speed of the compost bin in S2 is 25-35rpm.

7. The composting method according to claim 6, characterized in that: The ventilation part of the rotary composting box is located in the middle of the side wall of the box.

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