A method for obtaining the aeration flow rate at different stages of aerobic composting and a method for increasing the humic acid content of compost products

Abstract

The present invention relates to the technical field of resource utilization of agricultural organic waste, and particularly relates to a method for obtaining the ventilation flow rate at different stages of aerobic composting and a method for increasing the humic acid content of compost products. The present invention provides a method for the ventilation flow rate at different stages of aerobic composting, and a method for increasing the humic acid content of compost products by using the obtained ventilation flow rate and moisture adjustment. According to the method of the present invention, after 30 days of composting, compared with the conventional aerobic composting treatment, after regulating the ventilation volume and moisture during the composting process by the present invention, the humic acid content of the compost materials has been greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization of agricultural organic waste, and particularly relates to a method for obtaining the ventilation flow rate at different stages of aerobic composting and a method for increasing the humic acid content of compost products. Background Art

[0002] Aerobic composting is a process in which aerobic microorganisms transform organic materials through their catabolism and anabolism under aerobic conditions. It is currently the main way and technical process for treating agricultural organic waste, and has the characteristics of large processing capacity, economic feasibility, and easy large-scale operation. The successful product of aerobic composting is organic fertilizer, and humic acid is a beneficial component in organic fertilizers, which is formed by the humification transformation of organic materials during the composting process. A large number of existing studies have shown that organic fertilizers with high humic acid content have higher potential in promoting the formation of soil aggregates, improving soil structure, and enhancing the buffering performance of the soil. To some extent, the content of humic acid has an important impact on the quality of organic fertilizers.

[0003] Increasing the humic acid content of compost products is one of the efforts in the current composting process. According to the polyphenol theory of humic acid formation, the main mechanism of humic acid formation is as follows: (1) Organic matter is oxidized into quinone compounds under the mineralization of microorganisms and water medium, and (2) Quinone compounds further undergo oxidation and polycondensation reactions to form humic acid (humus); Appropriate oxygen supply and sufficient water supply are the main external factors affecting humic acid formation. In actual production, when regulating parameters such as compost ventilation and moisture, the regulation is mostly carried out from the perspectives of ensuring the temperature of the compost pile, reducing odor generation, and killing pathogenic microorganisms, resulting in excessive ventilation volume, low moisture content, excessive loss of organic matter mineralization, and low content of precursor reaction substances for further synthesis of humic acid during the composting process, which is not conducive to the formation of humic acid in the compost. At the same time, there is no clear specification for the humic acid content in organic fertilizers in the current national and industry standards for organic fertilizers, resulting in little attention to the humic acid content in organic fertilizers during the production process of organic fertilizers, resulting in low humic acid content in organic fertilizers and restricting the improvement of the quality of organic fertilizers. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for increasing the humic acid content of compost products. Through the method provided by the present invention, without changing the existing aerobic composting process, by adjusting the ventilation volume and moisture during the composting process, the gaseous loss of organic materials during the composting process can be reduced, the humic acid content in the compost products can be significantly increased, and the quality of organic fertilizers can be improved.

[0005] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a method for increasing the humic acid content of compost products, comprising the following steps:

[0007] 1. Measure the basic oxygen consumption rate of unit volume of compost materials at different stages of composting (heating stage, high-temperature stage, cooling stage). The amount of oxygen required to maintain the activities of compost microorganisms is used as the basic oxygen consumption rate required for composting; wherein, the oxygen consumption rate is obtained by the method of interpolating the oxygen concentration per unit time using an oxygen sensor. Specifically: after filling a sealed container with unit volume of compost materials, measure the oxygen concentration at intervals with an oxygen sensor, and then through the formula:

[0008] (Formula 1)

[0009] Calculate and obtain.

[0010] In the formula: S: oxygen consumption rate of unit compost body at a certain temperature, g / (h×m 3 ); p0: percentage of oxygen in air at t = 0, %; pt: percentage of oxygen in air at time t, %; ρo2: density of oxygen, usually taken as 1.43 g / L; t: time required for oxygen to reach the lowest concentration after ventilation stops, min; V air Volume of air in the sealed tank, L; Vp Volume of compost materials.

[0011] 2. According to the obtained basic oxygen consumption rate S of unit volume of compost materials, calculate the minimum ventilation volume required to maintain the activity of compost microorganisms in combination with the air density:

[0012] (Formula 2)

[0013] In the formula: F min Minimum air ventilation volume of unit volume of compost materials, L / (min·m 3 ); S: oxygen consumption rate of unit volume of compost body at a certain temperature, g / (h×m 3 ); ρair: density of air, usually taken as 1.293 g / L.

[0014] 3. Determine the ventilation volume as the upper limit of ventilation volume according to maintaining the temperature and heat balance of the fermentation compost body. The formula is:

[0015] (Formula 3)

[0016] In the formula: F max Is the heat balance air ventilation volume of unit volume of compost materials when maintaining a certain compost body temperature, L / (min·m 3 ); S: oxygen consumption rate of unit volume of compost body at a certain temperature, g / (h×m 3); q: specific heat capacity of oxygen, usually taken as 0.014 kJ / g; γ: heat of vaporization of water at a certain temperature, kJ / kg, calculated according to the formula (γ = -2.4314t + 2502.6, t in °C); C p dry : heat capacity of dry air at a certain temperature, kJ / (m 3 ·K), taking the value of 1.16 under the conditions of 100 kPa and 25 °C; f sat(T) is the saturated humidity of air at a certain temperature, kg / m 3 , obtained by calculation according to the formula ; T amb : environmental temperature; T is the temperature of the exhaust gas, usually taken as the internal temperature of the pile body.

[0017] 4. On the basis of obtaining the minimum ventilation volume F min required for composting and the maximum ventilation volume F max for maintaining heat balance, taking the internal temperature T of the compost pile body, environmental temperature T amb during ventilation and the maximum compost temperature T max expected to be reached during the composting process as parameters to obtain the ventilation flow rate at different times. The actual ventilation volume calculation formula is:

[0018] F = (T - T amb ) / (T max - T amb ) * (F max - F min ) (Formula 4)

[0019] T max usually ranges from 55 - 60 °C.

[0020] 5. To ensure an increase in the humic acid content, the moisture content of the pile body should be higher than the moisture requirements of conventional composting, increased from the moisture content of 50 - 60% in conventional composting to the range of 65% - 70%.

[0021] Beneficial effects Description of the drawings

[0022] Figure 1 is the humic acid content after aerobic composting of different nitrogen source materials. Specific implementation manners

[0023] The following combines examples to elaborate in detail on the solutions provided by the present invention, but they cannot be construed as limiting the protection scope of the present invention. Examples

[0024] Using urea, chicken manure, and cow manure as nitrogen sources respectively, and corn straw as the composting material, the carbon-nitrogen ratio was adjusted to 25:1 uniformly, the moisture content was controlled at 65%, and the volume of the compost pile was 1 m 3 , under the condition that the average environmental temperature was 17 - 21 °C, static pile composting was carried out. To avoid gas inlet errors caused by turning the pile, the pile was not turned during the entire composting process. For different composting materials calculated according to Formulas 1 - 4 of the present invention, the theoretical ventilation rates were respectively:

[0025] Table 1 Theoretical ventilation rates of different compost pile materials

[0026]

[0027] On the basis of determining the upper and lower limits of the ventilation rate, the ventilation rate was adjusted according to the environmental temperature according to Table 1. The ventilation interval was uniformly 10 minutes of ventilation and 4 hours of stop; at the same time, conventional ventilation was used as a control for different mixed materials, and the conventional ventilation rate was fixed at 50 L·min at each stage -1 ·m -3 , also with 10 minutes of ventilation and 4 hours of stop.

[0028] According to the method of the present invention, after 30 days of composting, the content of humic acid in each composting material was as Figure 1 shown. Compared with conventional aerobic composting treatment, after adjusting the ventilation rate and moisture content during the composting process by using the present invention, the humic acid content of the composting materials was increased by a large margin. Among them, the humic acid content of the chicken manure + straw composting material increased by up to 61.5%, the humic acid increase of the urea + straw treatment was 32.4%, and the increase rate of the cow manure + straw treatment was relatively small, but it also reached 18.3%. It can be considered that the application of this technology can increase the humic acid content of the composting material by more than 15%. The present invention is simple and easy to implement. After a single calculation for different materials, it can be used as fixed parameters in the existing fermentation process, and can significantly improve the efficiency of the composting reaction.

[0029] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for obtaining the ventilation flow rate at different stages of aerobic composting, characterized in that, It includes the following steps: (1) Measuring the basic oxygen consumption rate S of the compost material per unit volume at different stages of composting. The basic oxygen consumption rate is the amount of oxygen required to maintain the activities of compost microorganisms; (2)Based on the said basic oxygen consumption rate S, calculate the minimum ventilation volume F required to maintain the activity of compost microorganisms in combination with the air density min : Formula 2; In Formula 2: F min : minimum ventilation volume, L / (min·m 3 ); S: oxygen consumption rate, g / (h·m 3 ); ρair: density of air, with a value of 1.293 g / L; (3) Determining the ventilation volume as the upper limit of the ventilation volume according to maintaining the temperature and heat balance of the fermentation heap. Formula 3 is: In Equation 3: F max : The maximum ventilation volume to maintain thermal balance, L / (min·m 3 ); S: Oxygen consumption rate, g / (h·m 3 ); q: Specific heat capacity of oxygen, with a value of 0.014 kJ / g; γ: The heat of vaporization of water at a certain temperature, kJ / kg, calculated according to the formula γ = -2.4314t + 2502.6, where t is in °C; C p dry : The specific heat capacity of dry air at a certain temperature, kJ / (m 3 ·K), taking the value of 1.16 under the conditions of 100 kPa and 25 °C; f sat(T) is the saturated humidity of air at a certain temperature, kg / m 3 , calculated according to the formula ; T amb is the ambient temperature, K; T is the internal temperature of the heap, K; (4)On the basis of obtaining the minimum ventilation volume F required for composting min and the maximum ventilation volume F for maintaining thermal balance max Based on the internal temperature T of the compost pile during ventilation, the ambient temperature T amb and the maximum temperature T of the compost expected to be reached during the composting process max as parameters, the ventilation flow rate at different times is obtained; the formula for the actual ventilation volume is Formula 4: Formula 4 is F = (T - T amb ) / (T max - T amb ) * (F max - F min ) T max The value range of is 55 - 60 °C.

2. The method according to claim 1, wherein The stages of the composting include the heating stage, the high-temperature stage and the cooling stage.

3. The method according to claim 1, wherein In step (1), the basic oxygen consumption rate is obtained by using an oxygen sensor to measure the interpolation of the oxygen concentration per unit time. Specifically, after a sealed container is filled with the compost material per unit volume, the oxygen concentration at intervals is measured by an oxygen sensor, and then calculated through Formula 1: Formula 1; Where: S: oxygen consumption rate, g / (h·m 3 ); p0: percentage of oxygen in air at t = 0, %; pt: percentage of oxygen in air at time t, %; ρo2: density of oxygen, taken as 1.43 g / L; t: time required for oxygen to reach the lowest concentration after aeration stops, h; V air : volume of air in the sealed tank, L; Vp: volume of compost material, m 3 .

4. Application of the ventilation flow rates at different times of aerobic composting obtained by the method according to any one of claims 1 to 3 in increasing the humic acid content of the compost product.

5. A method for increasing the humic acid content of compost products, characterized in that, It includes the following steps: adjusting the ventilation according to the ventilation flow rates at different times of aerobic composting obtained by the method according to any one of claims 1 to 3, and adjusting the moisture content of the heap to 65 - 70%.

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