Method for resource utilization of pig manure mixed with fly ash by using hermetia illucens larvae

Abstract

The present disclosure belongs to the technical field of excrement treatment, and specifically provides a method for resource utilization of pig manure mixed with fly larvae and fly ash, comprising: S1, feeding pig manure mixed with fly larvae and fly ash in a circulating fluidized bed; S2, periodically measuring the length and weight gain of the larvae, and measuring the crude protein, crude fat, waste reduction rate and intestinal microbiome of the larvae after the conversion is completed; S3, determining the appropriate addition ratio of the fly ash in the circulating fluidized bed according to the measured indexes. The fly larvae reduce the mixture of pig manure and fly ash, and the worm manure produced not only meets the requirements of organic fertilizer for organic matter, nitrogen, phosphorus and potassium nutrients, but also is rich in silicon elements which may promote rice growth. After the fly ash enters the worm intestine, it undergoes a strong acid digestion link, so that the fly ash experiences a similar acid modification process, and the strong acid corrosion causes micropores to appear on the surface of the fly ash particles, which may play an important role in soil structure and fertility.

Description

Technical Field

[0001] This disclosure relates to the field of fecal treatment technology, and in particular to a method for the resource utilization of black soldier fly larvae by mixing pig manure with fly ash. Background Technology

[0002] Due to the rapid development of intensive farming, the number of high-density, enclosed pig farms has increased significantly. In 2017, pig farms generated 1.64 × 10⁻⁶... 9 Tons of pig manure. Pig manure is a source of environmental pollution, harboring infectious diseases, heavy metals, and organic pollutants, endangering public health. Various manure treatment technologies have been developed to modify the physical, chemical, and / or biological properties of manure, improve its transportation, or reduce its environmental impact.

[0003] Circulating fluidized bed (CFB) boilers have many advantages, including wide fuel adaptability, high combustion efficiency, and simple structure and easy operation, and have been widely used in my country in recent years. The combustion temperature of CFB boilers is typically 800–900℃, far lower than the operating temperature of pulverized coal boilers (≥1200℃). Due to the use of in-furnace sulfur fixation technology, CFB ash has a higher calcium and sulfur content. Therefore, compared with traditional pulverized coal boiler (PC) fly ash, CFB ash has unique physicochemical properties: larger average particle size and irregular block shape; higher CaO and SO3 content in its chemical composition; and its phase composition mainly consists of quartz, anhydrite, and amorphous aluminosilicates, and may also contain small amounts of lime, hematite, unburned carbon, and free CaO. With the increase of CFB power generation units in coal-producing areas of my country, the emission of CFB ash has also increased, but its utilization rate is relatively low. Large amounts of unused CFB ash accumulate, seriously threatening the ecological environment.

[0004] Recently, black soldier fly larvae (BSF) have attracted attention due to their diverse feeding habits, high conversion rate, environmental friendliness, and low cost. Their larvae have been shown to be effective at digesting various animal excrement. BSF larvae can alter the physical, chemical, and biological properties of excrement, as well as its moisture and nutrient composition, within one to two weeks. Studies have shown that BSFs are highly efficient at converting organic waste, and the larvae fed with waste are rich in protein and oil, making them suitable for use as animal feed additives, in biodiesel production, and in antimicrobial peptide formulations. The frass produced by the insects converting organic waste meets organic fertilizer standards and can be used for plant growth. Currently, there are no studies reporting the effects of feeding inorganic waste on the insects themselves and their frass. Summary of the Invention

[0005] This disclosure aims to at least solve one of the technical problems existing in the prior art, and proposes a method for the resource utilization of black soldier fly larvae by mixing pig manure with fly ash.

[0006] This disclosure provides a method for the resource utilization of black soldier fly larvae by mixing pig manure with fly ash, including:

[0007] S1, using pig manure mixed with circulating fluidized bed fly ash to feed black soldier fly larvae;

[0008] S2, larval length and larval weight gain are measured regularly, and crude protein, crude fat, waste reduction rate and gut microbiome of larvae are measured after transformation.

[0009] S3. Determine the appropriate addition ratio of fly ash for circulating fluidized bed based on the indicators measured in S2.

[0010] Preferably, the pig manure is the manure of growing pigs aged 4-15 weeks.

[0011] Preferably, S1 specifically includes:

[0012] Pig manure was mixed with circulating fluidized bed fly ash and fed to 4-day-old black soldier fly larvae in groups. The conversion cycle was 12-16 days according to the larval growth curve.

[0013] Preferably, S1 specifically includes: the proportion of fly ash added to the circulating fluidized bed is 2.5%-7.5% of the total feed weight.

[0014] Preferably, after step S3, the method further includes:

[0015] S4. The insect excrement produced under the appropriate addition ratio is observed by scanning electron microscopy to determine the heavy metal content and the microstructure of fly ash and insect excrement. The organic matter, nitrogen, phosphorus and potassium of insect excrement are determined according to the national standard for organic fertilizer. The specific mesoporous data of fly ash after passing through the insect intestine are determined by BET. Attached Figure Description

[0016] Figure 1 Physiological sections of black soldier fly larvae intestinal tissue provided in this embodiment of the method for resource utilization of black soldier fly larvae using pig manure mixed with fly ash;

[0017] Figure 2 This is an illustration of the gut microbiome of black soldier fly larvae using a method of resource utilization of pig manure mixed with fly ash, as provided in an embodiment of this disclosure.

[0018] Figure 3 This is an example of the gut microbiota network of black soldier fly larvae using a method of resource utilization of pig manure mixed with fly ash provided in this embodiment of the disclosure;

[0019] Figure 4 SEM detection of insect excrement in the method of resource utilization of black soldier fly larvae using pig manure mixed with fly ash provided in the embodiments of this disclosure;

[0020] Figure 5 The elemental spectrum of the excrement was measured after using the method of resource utilization of black soldier fly larvae by mixing pig manure with fly ash in the embodiments of this disclosure. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] In the various figures, the same elements are represented by similar reference numerals. For clarity, not all parts in the figures are drawn to scale. Furthermore, some well-known parts may not be shown in the figures.

[0023] Many specific details of this disclosure, such as the structure, materials, dimensions, processing methods, and techniques of the components, are described below to provide a clearer understanding of the disclosure. However, as those skilled in the art will understand, this disclosure may be implemented without following these specific details.

[0024] This invention specifically provides a method for the resource utilization of black soldier fly larvae by mixing pig manure with fly ash, comprising the following steps:

[0025] S1, using pig manure mixed with circulating fluidized bed fly ash to feed black soldier fly larvae;

[0026] S2, larval length and larval weight gain are measured regularly, and crude protein, crude fat, waste reduction rate and gut microbiome of larvae are measured after transformation.

[0027] S3, determine the appropriate addition ratio of fly ash for circulating fluidized bed based on the indicators measured in S2;

[0028] S4. The insect excrement produced under the appropriate addition ratio is observed by scanning electron microscopy to determine the heavy metal content and the microstructure of fly ash and insect excrement. The organic matter, nitrogen, phosphorus and potassium of insect excrement are determined according to the national standard for organic fertilizer. The specific mesoporous data of fly ash after passing through the insect intestine are determined by BET.

[0029] Based on existing research findings mentioned in the background section, this invention uses growing pig manure (from 4-15 week old pigs) mixed with different proportions of circulating fluidized bed fly ash to feed 4-day-old black soldier fly larvae in groups. The conversion cycle is 12-16 days according to the larval growth curve. During this period, larval length and weight gain are measured regularly. After conversion, the crude protein, crude fat, waste reduction rate, and intestinal microbiome of the larvae are measured based on their weight, and intestinal physiological sections of the larvae are observed. The appropriate addition ratio of circulating fluidized bed fly ash is determined based on these indicators. The resulting insect excrement is then observed using scanning electron microscopy to determine the heavy metal content and the microstructure of fly ash and insect excrement. The organic matter, nitrogen, phosphorus, and potassium content of the insect excrement are measured according to national standards for organic fertilizers. BET analysis is used to determine the specific mesopore data of fly ash after passing through the insect intestine.

[0030] Fly ash was encased in insect excrement. EDS analysis showed that the insect excrement containing fly ash was rich in silicon (CFA5, for example). Silicon enrichment plays an important role in the growth of plants, especially rice. Therefore, this experiment shows that the insect excrement produced by adding fly ash not only meets the standards for organic fertilizer, but also has functions such as promoting growth in certain crops.

[0031] Experimental results of embodiments of the present invention:

[0032] 1. Weight gain and body length. The highest body weight of a single insect in the control group (CK) reached 137 mg on day 12, while the highest body weight in the fly ash-added group reached 16 days. Among the experimental groups, the body weight of the insects with CFA 2.5-7.5 added to the circulating fluidized bed was higher than that of the other CFA 10-20 experimental groups, as shown in Table 1 below:

[0033] Table 1. Results of weight gain determination of larvae in pig manure with added fly ash

[0034]

[0035] Note: Different lowercase letters in the superscript of peer data indicate significant differences. P <0.05, the same or no letter indicates no significant difference ( P >0.05). Same as the table below.

[0036] The growth of larvae in the control group is shown in Table 2. As the addition ratio increased, the larval body length decreased significantly linearly. P <0.05).

[0037] Table 2. Results of larval body length determination using pig manure with added fly ash

[0038]

[0039] 2. Larval protein and fat composition. With increasing addition ratio, larval protein (CP) showed a significant linear decreasing trend. P =0.04), crude fat (EE) remained relatively stable, while waste reduction rate (WR) showed a significant decreasing trend with the addition of fly ash. P< 0.0001), as shown in Table 3 below:

[0040] Table 3. Nutritional impact and reduction rate of larvae in pig manure after adding fly ash.

[0041]

[0042] 3. Effects of larval gut on results. Staining of physiological sections showed that with increasing additive ratio, the intestinal contents changed from a uniform, dense state to a vacuolated, coagulated state. Figure 1 Increased gut microbial diversity Figure 2 ),Depend on Figure 3It can be seen that there are differences in the microbial network diagrams of different experimental groups. According to the network topology diagram feature analysis results, the number of network nodes from least to most is as follows: CFA5 group (39), CFA2.5 group (37), CFA10 group (34), CFA7.5 group (33), and CK group (33). The number of network topology diagram connections from least to most is as follows: CFA7.5 group (64), CFA5 group (56), CFA2.5 group (38), CFA10 group (32), and CK group (28). Microbial networks can be used to analyze the complex interactions between microorganisms and prove the mathematical validity of microbial community aggregation. According to existing research, the higher the number of nodes and connections, the more complex the network, and the more complex the network usually represents a more stable and healthy gut. In this experiment, the network complexity of the fly ash addition group was higher than that of the control group. Among them, the number of microbial network nodes and connections of the CFA5 group was the highest. Therefore, the gut network of this group was the most complex, which means that the gut of the larvae in this group was more stable and healthy than that of other groups.

[0043] 4. Nutrient Analysis of Insect Manure. According to the national standard for organic fertilizer (NY 525-2012), the organic matter, total nitrogen, total phosphorus, and total potassium content of insect manure in different addition groups were tested. The results showed that the experimental groups with added circulating fluidized bed fly ash (CFA) 2.5-7.5 met the organic fertilizer standard (NY 525-2012) in terms of total nutrients, pH, and organic matter content. The experimental groups with CFA 10 and higher additions had organic matter content below 45%, which did not meet the standard (Table 4).

[0044] Table 4. Results of detection of organic matter, total nitrogen, total phosphorus and total potassium content in insect excrement

[0045]

[0046] 5. SEM detection of insect excrement. Figure 4 and Figure 5 It can be seen that fly ash is encased in insect excrement. EDS analysis shows that the insect excrement containing fly ash is rich in silicon (CFA5 for example). Silicon enrichment plays an important role in the growth of plants, especially rice. Therefore, this experiment shows that the insect excrement produced by adding fly ash not only meets the standards of organic fertilizer, but also has the function of promoting growth for certain crops.

[0047] 6. Results of Insect Excrement Surface Structure Characteristics. Currently, the main method used in the chemical industry for fly ash is modification. Acid modification, alkali modification, and functional group modification can endow fly ash with various abilities, such as adsorbing heavy metal ions, and it is commonly used in soil remediation. Insect midgut acidity is low, typically 2-4. Therefore, whether adding fly ash through the insect gut will acidify it was investigated. Based on this, BET was used to determine the nitrogen adsorption ratio of fly ash after passing through the intestinal acid environment to determine the effect of intestinal acid on fly ash. If there is a difference, insect excrement is not only a functional organic fertilizer but may also have a positive effect on soil aggregate formation and soil remediation. Mesopore data are shown in Table 5 below:

[0048] Table 5. Data on insect frass pores

[0049]

[0050] As shown in Table 5, the BET surface area of ​​the insect excrement produced by the experimental groups with different concentrations of circulating fluidized bed fly ash (CFA2.5–CFA7.5) was significantly higher than that of the original fly ash (CFAC). P The specific surface area of ​​the insect manure produced by adding 5% fly ash was <0.05, which was higher than that of the insect manure produced by the pig manure test group (CK). The specific surface area of ​​organic fertilizer has many effects on soil, mainly including the following:

[0051] 1. Soil structure: A larger specific surface area helps increase the contact area between organic fertilizer and soil particles, promotes the formation of soil aggregates, improves the soil pore structure, and enhances the soil's aeration and water retention.

[0052] 2. Enhance soil fertility: It enables organic fertilizer to better combine with the soil, slowly release nutrients, and improve the soil's nutrient supply and fertilizer retention capacity.

[0053] 3. Promotes microbial activity: Provides more space for soil microorganisms to attach and grow, which is conducive to the reproduction and activity of microorganisms, thereby promoting the transformation and cycling of substances in the soil.

[0054] 4. Enhance soil's adsorption capacity for pollutants: Increase the soil's adsorption and fixation of harmful substances, and reduce the migration and diffusion of pollutants in the soil.

[0055] Therefore, utilizing black soldier fly larvae to reduce the mixture of pig manure and fly ash produces insect excrement that not only meets the requirements of organic fertilizer for organic matter, nitrogen, phosphorus, and potassium, but its high silicon content may also promote rice growth. Furthermore, its increased specific surface area may play a significant role in soil structure and fertility. Regarding the reason why the specific surface area of ​​the insect excrement increases after adding fly ash, experiments show that after entering the larval intestine, the fly ash undergoes a strong acid digestion process in the midgut, resulting in an acid-like modification process. The strong acid corrosion causes micropores to appear on the surface of the fly ash particles, increasing their surface area. Currently, no literature or research has explored the biological gastrointestinal acid modification of fly ash. Traditional acid modification requires a large amount of labor, chemical raw materials, and resources, and poses a certain threat to the environment. In contrast, the biological acid modification in this study occurs naturally alongside waste reduction, which is highly innovative.

[0056] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for the resource utilization of black soldier fly larvae by mixing pig manure with fly ash, characterized in that, include: S1, using pig manure mixed with circulating fluidized bed fly ash to feed black soldier fly larvae; Four-day-old black soldier fly larvae were fed in groups using pig manure mixed with circulating fluidized bed fly ash. The conversion period was 12-16 days according to the larval growth curve. The proportion of circulating fluidized bed fly ash added was 2.5%-7.5% of the total feed weight. S2, larval length and larval weight gain are measured regularly, and crude protein, crude fat, waste reduction rate and gut microbiome of larvae are measured after transformation. S3, determine the appropriate addition ratio of fly ash for circulating fluidized bed based on the indicators measured in S2; S4. The insect excrement produced under the appropriate addition ratio is observed by scanning electron microscopy to determine the heavy metal content and the microstructure of fly ash and insect excrement. The organic matter, nitrogen, phosphorus and potassium of insect excrement are determined according to the national standard for organic fertilizer. The specific mesoporous data of fly ash after passing through the insect intestine are determined by BET.

2. The method for resource utilization of black soldier fly larvae by mixing pig manure with fly ash according to claim 1, characterized in that, The pig manure mentioned is from growing pigs aged 4-15 weeks.

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