JP7816772B2 - Liquid fertilizer manufacturing method - Google Patents

Description

The present invention relates to a method for producing liquid fertilizer from livestock waste, and more specifically to a method for producing odorless, high-quality liquid fertilizer from livestock manure in a short period of time.

Livestock waste, primarily livestock manure, is discharged in large quantities from the livestock industry. It has a strong odor, a high pollution load, and a significant impact on the water quality of closed water bodies. Therefore, the Act on Proper Management and Promotion of Utilization of Livestock Manure (also known as the Livestock Manure Act) stipulates the appropriate management and utilization of livestock manure.

Livestock manure is often composted for use because it is rich in the three fertilizer elements of nitrogen, phosphorus, and potassium, as well as organic matter. However, composting livestock manure presents a number of problems, including: (1) the need to adjust the moisture content and turn the manure over, which is time-consuming; (2) the composting process takes a long time, lasting several months; and (3) the composting process produces high concentrations of foul odors, such as ammonia, which remain in the resulting compost, making it difficult to use.

Patent Document 1 proposes a method for producing fermented fertilizer while suppressing odor generation by mixing koji mold spores into feces, fermenting the feces to decompose the organic matter contained in the feces, and promoting the growth of at least one beneficial microorganism among fungi, lactic acid bacteria, and bifidobacteria, which use the decomposed organic matter as a nutrient source. Patent Document 2 also proposes a method for producing odorless swine manure fertilizer in a relatively short period of time, around two to three months, by storing swine manure under alternating anaerobic and aerobic conditions, adding at least one microorganism selected from photosynthetic bacteria, yeast, and filamentous fungi, and fermenting the manure under aerobic conditions.

Japanese Patent Application Publication No. 11-171674 JP 2001-80980 A

However, the method described in Patent Document 1 targets the "feces" that are solid and have little moisture in the excrement excreted by animals, and is primarily intended for chicken manure collected in solid form from livestock barns. Therefore, no method has been proposed for treating excrement from animals such as pigs and cows, which produce large amounts of urine and therefore have a high moisture content in their excrement, resulting in a slurry or liquid state.

In addition, the method described in Patent Document 2 desirably treats pig manure from which as much urine as possible has been separated and removed. This method also involves multiple steps, including storing the pig manure under alternating anaerobic and aerobic conditions, and then fermenting it under aerobic conditions, and the fertilizer production period can last several months.

Therefore, the present invention was made in consideration of the above-mentioned drawbacks of the prior art, and its purpose is to provide a method for producing odorless liquid fertilizer from slurry or liquid livestock waste in an extremely short period of time, such as one day to several weeks, while suppressing the generation of odors.

Another object of the present invention is to provide a method for producing liquid fertilizer that can promote plant growth and improve yield per unit area.

To solve the above problems, the method for producing liquid fertilizer of the present invention includes the steps of preparing livestock wastewater containing livestock manure and at least 90% by weight of water, adding oils and fats and koji mold to the livestock wastewater, and aerating the livestock wastewater to which the oils and fats and koji mold have been added at a temperature of 15 to 40°C.

By adding koji mold to liquid or slurry livestock manure containing 90% or more water by weight and subjecting it to aeration, the aerobic microorganism koji mold proliferates in the livestock manure and decomposes the organic matter contained in the manure. Livestock manure typically contains high concentrations of nitrogen, ranging from 5,000 to 7,000 mg/L, resulting in a significantly low C/N ratio. This nitrogen generates high concentrations of ammonia, and the livestock wastewater maintains a high pH, slowing the activity and growth of koji mold. However, the inventors have discovered that adding oils and fats to the livestock manure effectively improves the C/N ratio in the livestock wastewater, allowing koji mold to decompose the oils and fats, increasing the carbon content in the livestock manure and using it as nutrition. Furthermore, large amounts of nitrogen are taken up by the actively growing koji mold cells, where it is converted into koji mold cell proteins, thereby suppressing ammonia production. Furthermore, because ammonia generation is suppressed, the growth of koji mold is not hindered, and the koji mold that grows rapidly in the livestock manure decomposes organic matter and absorbs nitrogen. This makes it possible to produce odor-free liquid fertilizer from livestock manure in an extremely short period of time, about one day to one week, while suppressing the generation of unpleasant odors. Note that, in the present invention, "odor-free" does not refer to a state in which there is no odor at all, but rather to a state in which the odor (mainly ammonia) generated from the livestock manure being treated has been almost completely eliminated and the manure can be used without any resistance as liquid fertilizer.

In addition, in the liquid fertilizer manufacturing method of the present invention, it is also preferable that the oil or fat mentioned above is vegetable oil or livestock animal fat. This allows for effective utilization of used vegetable oil and livestock animal fat separated during meat processing and disposed of as waste. Of these, livestock animal fat is solid at room temperature and has a low specific gravity, so it floats on the top surface of the livestock wastewater during aeration treatment and is decomposed by koji mold. Therefore, even if excess livestock animal fat is added, the koji mold will decompose only the required amount of livestock animal fat, and when the aeration treatment is completed, the remaining oil or fat floating on the top surface can be easily collected and separated to obtain liquid fertilizer.

In addition, in the liquid fertilizer manufacturing method of the present invention, it is also preferable to add 0.06 parts by weight or more of fats and oils per 100 parts by weight of livestock waste liquid. This allows the selection of an appropriate amount of fats and oils to be added, which will suppress the generation of unpleasant odors while producing odorless liquid fertilizer.

In addition, in the liquid fertilizer manufacturing method of the present invention, it is also preferable that the koji mold is seed koji. This allows for the selection of koji mold in a form that is easy to handle.

In the liquid fertilizer manufacturing method of the present invention, it is also preferable that the koji mold is black koji mold or white koji mold. Black koji mold and white koji mold produce citric acid, which adjusts the pH of the livestock wastewater and suppresses the generation of ammonia.

In the liquid fertilizer manufacturing method of the present invention, it is also preferable that the koji mold is yellow koji mold. By adding yellow koji mold, nitrogen is actively taken up by the fungus body, and ammonia production is also suppressed.

In the method for producing liquid fertilizer of the present invention, it is also preferable to add koji mold so that the viable cell count of koji mold in the livestock wastewater is 1 x ¹⁰ CFU/mL or more. This allows for the selection of an appropriate amount of koji mold to be added, which allows for the production of an odorless liquid fertilizer while suppressing the generation of unpleasant odors.

In addition, in the liquid fertilizer manufacturing method of the present invention, it is also preferable that the livestock manure is pig or cow manure. This allows for the selection of an appropriate treatment target when manufacturing the liquid fertilizer of the present invention.

The method for deodorizing livestock wastewater of the present invention also includes the steps of preparing livestock wastewater containing livestock manure and a water content of 90% by weight or more, adding oils and fats and koji mold to the livestock wastewater, and aerating the livestock wastewater to which the oils and fats and koji mold have been added at a temperature of 15 to 40°C.

According to the present invention, a method for producing liquid fertilizer having the following excellent effects can be provided.
(1) It is possible to produce an odorless liquid fertilizer while suppressing the generation of odors such as ammonia from livestock manure.
(2) Liquid fertilizer can be produced from livestock manure in an extremely short period of time (about one day to one week).
(3) In the production process, there is no need to adjust the moisture content of livestock manure or turn it over, which saves time and effort. In addition, all that is required for production is a tank for storing livestock wastewater and an aeration device, which reduces production costs.
(4) A liquid fertilizer can be obtained that can promote plant growth and increase the yield per unit area.

1 is a flowchart schematically showing a method for producing liquid fertilizer according to the present embodiment. 10 is a graph showing the analysis results of brown rice obtained by applying the liquid fertilizer of the present invention and brown rice obtained by applying a commercially available organic fertilizer in Example 4. FIG. 10 is a diagram showing a schematic configuration of a continuous treatment device used to produce liquid fertilizer in Example 5.

The method for producing liquid fertilizer of the present invention will be described below with reference to Figure 1. As shown in Figure 1, the method for producing liquid fertilizer P1 according to an embodiment of the present invention is roughly composed of step S0 of preparing livestock wastewater, step S1 of adding oils and fats and koji mold to the livestock wastewater, and step S2 of aerating the liquid.

(Preparation of livestock wastewater)
First, we will explain step S0 of preparing livestock wastewater, as shown in Figure 1. In the present invention, livestock wastewater refers to a liquid or slurry-like wastewater containing livestock manure and urine, containing 90% or more by weight of water. Livestock manure is the waste of livestock animals such as pigs, cows, and chickens. In the present invention, pig or cow manure is preferred, with pig manure being particularly preferred, because it contains high amounts of nitrogen, phosphorus, and potassium and produces a liquid fertilizer with a high fattening effect, as shown in Table 1 below (quoted from the Central Livestock Association, "Technology and Examples of Treatment and Utilization of Livestock Urine Wastewater," 1989). Furthermore, while livestock wastewater is primarily composed of livestock manure, it may also contain wastewater from livestock barn cleanings, and if the moisture content of the livestock manure is less than 90% by weight, water may be added to adjust the moisture content. For example, according to Table 1 below, the SS of swine manure (mixed) is 8%, and the SS of cow manure (mixed) is 7.4%, so the moisture content of pig or cow manure is approximately 92-93%, but chicken excrement has a low moisture content, so livestock waste can be made by adding water. Even with cow or pig excrement, if the excrement has a low moisture content due to manure separation, water can be added to make livestock waste. Furthermore, the livestock manure contained in livestock waste is not limited to being from the same type of livestock, and it can also be a mixture of manure and urine from different types of livestock.

The moisture content of the above-mentioned livestock wastewater is preferably 90% by weight or more, more preferably 92% by weight or more, and even more preferably 95% by weight or more, in order to efficiently aerate in the aeration treatment described below.

Next, we will explain process S1, which involves adding oil and fat and koji mold to livestock wastewater.

(Addition of oils and fats)
In this process, fats and oils are added to the livestock wastewater. The fats and oils referred to in the present invention refer to glycerol esters of higher fatty acids. From the viewpoint of safety, vegetable fats and oils or animal fats that are primarily edible are preferably used. Examples of such fats and oils include vegetable oils that are liquid at room temperature, such as soybean oil and rapeseed oil; vegetable fats that are solid at room temperature, such as palm oil; animal fats that are liquid at room temperature, such as fish oil; and animal fats that are solid at room temperature, such as lard, beef tallow, and chicken fat, as well as combinations thereof. Among these, oils with low melting points and liquid at room temperature, such as vegetable oils, are preferably selected from the viewpoint of rapid odor reduction. In the present invention, the addition of fats and oils to the livestock wastewater includes not only the addition of fats and oil products produced from fats and oil raw materials through processes such as extraction and refining to the livestock wastewater, but also the direct addition of animal or plant tissues containing fats and oils to the livestock wastewater. The amount of oil and fat to be added is preferably 0.06 to 10 parts by weight, more preferably 0.1 to 3 parts by weight, and even more preferably 0.3 to 1 part by weight, since if the amount of oil and fat added per 100 parts by weight of livestock waste liquid is less than 0.06 parts by weight, the effect of suppressing the generation of bad odors from livestock manure and the effect of deodorizing the liquid fertilizer will be impaired.

In particular, in the present invention, waste oil or waste containing oil is preferably used when adding oils and fats, from the perspective of effective waste utilization. Among these, livestock fats, such as lard, beef tallow, and chicken fat, separated when slicing meat for consumption at meat processing plants, and animal tissues containing such fats are disposed of in large quantities as waste, which is problematic. However, in the present invention, these fats can be effectively utilized as oils and fats to be added to livestock wastewater. Furthermore, while used vegetable oils (rapeseed oil, soybean oil, corn oil, palm oil, sesame oil, etc.) present disposal issues, such used vegetable oils and fats are also suitable for use in the present invention. Furthermore, because livestock fats such as lard, beef tallow, and chicken fat are solid at room temperature and have a low specific gravity, livestock fats and animal tissues containing such fats float to the top surface of livestock wastewater during aeration treatment and are decomposed by the koji mold described below. Therefore, even if an excess amount of oil or fat is added, the koji mold will decompose the required amount of livestock animal fat, and when the aeration process is completed, the remaining oil or fat floating on the upper surface can be easily collected and separated to obtain liquid fertilizer.

(Addition of koji mold)
In this process, koji mold is added to the livestock wastewater. The koji mold in the present invention refers to a microorganism primarily used in producing koji-fermented foods, specifically black koji mold, white koji mold, and yellow koji mold, or a combination thereof. Among these, black koji mold refers to a group of molds of the genus Aspergillus that form black or dark brown conidia (a type of asexual spore) and are used in the production of distilled alcoholic beverages such as awamori in Okinawa and sweet potato shochu in Kagoshima. Specific examples include, but are not limited to, Aspergillus awamori var kawachi (Kawachi black koji mold), Aspergillus ryukuensis, Aspergillus awamori, Aspergillus saitoi, Aspergillus inui, Aspergillus usami, and Aspergillus aureus. Furthermore, white koji mold refers to a group of molds of the genus Aspergillus that form white-ochre conidia, specifically, for example, Aspergillus kawachi. Furthermore, yellow koji mold refers to a group of molds of the genus Aspergillus that form yellow or yellow-green conidia, and is a microorganism that is mainly used in the production of sake, miso, soy sauce, etc. Specific examples include, but are not limited to, Aspergillus oryzae and Aspergillus sojae.

In the present invention, black koji mold or white koji mold is preferably used because it produces citric acid and has a pH-adjusting effect that suppresses an increase in the pH of livestock wastewater, as well as an excellent odor-suppressing effect. Yellow koji mold is also preferably selected because it is excellent at improving the C/N ratio. Specifically, black koji molds such as Kawachi black koji mold (Aspergillus awamori var. kawachii), Aspergillus luchuensis, or Aspergillus inuii, white koji molds such as Aspergillus kawachii, yellow koji molds such as Aspergillus oryzae, and combinations thereof are preferably used.

The addition of koji mold can be carried out, for example, by adding koji starter or by adding koji mold that has been previously cultured in a liquid medium or the like and grown to a certain amount as a starter, but adding koji starter is preferred from the viewpoint of ease of handling. When adding koji mold, it is preferable to add koji mold spores. For example, when the number of spores contained in 1 g of koji starter is 1 billion, it is preferable to add about 0.001 to 5 parts by weight of koji starter per 100 parts by weight of livestock wastewater, and it is more preferable to add about 0.001 to 1 part by weight of koji starter. Furthermore, since the deodorizing effect of livestock manure is impaired if the viable koji mold count in the livestock wastewater is less than 1 x 10 ⁴ CFU/mL, it is preferable to adjust the amount of koji mold added so that the viable koji mold count in the livestock wastewater is at least 1 x 10 ⁴ CFU/mL, and it is even more preferable to adjust the amount of koji mold added so that the viable koji mold count is at least 1 x 10 ⁵ CFU/mL.

(Aeration treatment)
Next, the aeration step S2 will be described. In this step, air is blown into the livestock wastewater to which koji mold and oils and fats have been added to perform the aeration treatment. The aeration treatment is carried out by generating a large amount of air bubbles in the livestock wastewater using an aeration device such as an aeration tube, aeration plate, or a diffuser, thereby bringing the air into contact with the livestock wastewater. Aeration in the aeration treatment is preferably carried out so that the oxidation-reduction potential (ORP) value of the livestock wastewater is −300 mV or higher, and more preferably in the range of −300 mV to 100 mV. This promotes the growth of koji mold, thereby accelerating the decomposition of organic matter and added lipids in the livestock wastewater and enabling the immobilization of a large amount of nitrogen contained in the livestock wastewater. Furthermore, the aeration treatment is preferably carried out under conditions where the temperature of the livestock wastewater is 15 to 40°C, and more preferably 30 to 40°C. This increases the growth rate of the koji mold and also improves the activity of the enzymes produced by the koji mold, thereby improving the treatment rate of the livestock wastewater. When the outside air temperature is low and the temperature of the livestock wastewater does not reach 15°C or higher, it is preferable to adjust the liquid temperature using a heating device such as a heater. It is preferable to control the viable cell count of koji mold contained in the livestock wastewater during aeration treatment so that it is at least 1 x ¹⁰⁴ CFU/mL or more, and it is even more preferable to control the viable cell count of koji mold so that it is 1 x ¹⁰⁵ CFU/mL or more.

Liquid fertilizer P1 is considered complete when the livestock wastewater has been aerated, eliminating the distinctive odor of livestock manure and rendering it nearly odorless. The time required for aeration varies from one day to one week depending on the temperature of the livestock wastewater, i.e., the growth rate of the koji mold and the activation state of the koji mold or the enzymes it produces. However, if the temperature of the livestock wastewater is between 30 and 40°C, odorless liquid fertilizer P1 can be obtained from the livestock wastewater in approximately one day.

By adding koji mold to livestock wastewater and carrying out the aeration treatment described above, the koji mold proliferates in the livestock wastewater, and the numerous enzymes it produces, such as carbohydrate-degrading enzymes, proteases, and lipases, break down and decompose the organic matter contained in the livestock manure.

As shown in Table 1 above, livestock manure generally contains high concentrations of nitrogen, ranging from 5,000 to 7,000 mg/L, and the C/N ratio of livestock wastewater that primarily contains livestock manure is significantly low. Therefore, if livestock wastewater is inoculated with only koji mold and subjected to aeration treatment, the nitrogen in the livestock wastewater is easily mineralized, resulting in the generation of high concentrations of ammonia gas and an increase in the pH of the livestock wastewater, which inhibits the growth of koji mold and also inhibits the decomposition of organic matter.

However, in the present invention, by adding oils and fats to livestock wastewater, the C/N ratio of the livestock wastewater is increased and improved. As a result, the koji mold breaks down the oils and fats, increasing the carbon content in the livestock wastewater and using it as its own nutrition. At the same time, a large amount of nitrogen is absorbed into the growing koji mold cells, converting the nitrogen in the livestock wastewater into koji mold cell proteins and suppressing the generation of ammonia from the livestock wastewater. Furthermore, because the generation of ammonia is suppressed, the increase in pH in the livestock wastewater is also suppressed, so the growth of the koji mold is not hindered, and the koji mold, which grows rapidly in the livestock wastewater, decomposes organic matter and absorbs nitrogen. This makes it possible to produce odorless liquid fertilizer in an extremely short period of time, from one day to one week, while suppressing the generation of unpleasant odors from the livestock wastewater.

The aeration treatment of livestock wastewater to which oils and koji mold have been added can be carried out by batch (batch) treatment or continuous treatment. In the case of continuous treatment, the aerated livestock wastewater is withdrawn in an amount equal to the amount of livestock wastewater newly introduced into the aeration tank and transferred to another tank, etc. When aeration treatment of livestock wastewater is carried out using a continuous treatment method, new livestock wastewater is introduced and the aerated livestock wastewater is withdrawn, thereby adding additional oils and koji mold so that the amount of oil and the number of live koji mold cells relative to the total amount of livestock wastewater in the aeration tank are not insufficient. Regarding oils and fats, it is preferable to add additional oils and fats so that the amount of oil and fat is at least 0.06 parts by weight, and more preferably 0.1 to 1 part by weight, per 100 parts by weight of the total livestock wastewater in the aeration tank. Furthermore, with regard to koji mold, it is preferable to adjust the amount of koji mold added so that the viable cell count of koji mold in the livestock wastewater in the aeration treatment tank is at least 1 x 10 ⁴ CFU/mL or more, and it is even more preferable to adjust the amount of koji mold added so that the viable cell count is 1 x 10 ⁵ CFU/mL or more.

Next, the present invention will be explained in more detail using examples, but the present invention is not limited to these examples in any way.

[Example 1]
1. Production of liquid fertilizer of the present invention 1 (black koji mold + vegetable oil)
A 2-L beaker was charged with 1,000 g of swine manure with a water content of 99.4% by weight to prepare livestock wastewater. To this livestock wastewater, 10 g of black koji mold (Aspergillus luchuensis) seed koji (1 billion spores per 1 g of seed koji) was added. Then, 10 g of used vegetable oil (canola oil) recovered from a commercial fryer was added to the beaker as an oil and fat. Air was then blown into the livestock wastewater at 1 L/min through an air tube installed in the beaker, and the livestock wastewater was aerated. The temperature of the livestock wastewater was adjusted to 36°C using a water bath, and the aeration treatment was carried out for 24 hours to obtain the liquid fertilizer of Example 1.

[Example 2]
2. Production of liquid fertilizer of the present invention 2 (yellow koji mold + vegetable oil)
A liquid fertilizer of Example 2 was obtained using the same materials and method as in Example 1, except that the koji mold added to the livestock wastewater was changed to 10 g of seed koji (1 billion spores/1 g of seed koji) of yellow koji mold (Aspergillus oryzae).

[Example 3]
3. Production of liquid fertilizer of the present invention 3 (black koji mold + animal fat)
The liquid fertilizer of Example 3 was obtained using the same materials and method as in Example 1, except that the oil and fat added to the livestock waste liquid was replaced with 10 g of tissue containing pork fat that had been discarded at a meat processing plant.

For each livestock wastewater sample in Examples 1-3, odor, pH, dissolved oxygen concentration (DO), oxidation-reduction potential (ORP), and C/N ratio were measured before aeration and at predetermined intervals after the start of aeration. C/N ratio measurements were performed using a simplified method that calculated the C/N ratio from total nitrogen (%) determined by Kjeldahl degradation and ion electrode analysis and total carbon (%) determined by loss on ignition analysis (URL: https://www.naro.affrc.go.jp/org/tarc/seika/jyouhou/H12/tnaes00046.html, National Agriculture and Food Research Organization website, FY2000 Tohoku Agricultural Research Results Information). Odor measurements were also performed using a sensory test, where the livestock wastewater was smelled during aeration to assess odor intensity. Evaluation results were expressed as +++: strong odor, ++: strong odor, +: easily detectable odor, ±: weak odor, and -: almost no odor. The results are shown in Tables 2 to 6 below.

[Comparative Example 1]
In this comparative example, the livestock wastewater was aerated using only black koji mold without adding any fats or oils. That is, the liquid fertilizer of Comparative Example 1 was obtained using the same materials and method as in Example 1, except that no fats or oils were added to the livestock wastewater.

For the livestock wastewater of Comparative Example 1, odor, pH, dissolved oxygen concentration (DO), oxidation-reduction potential (ORP), and C/N ratio were measured before aeration treatment and at predetermined time intervals after the start of aeration treatment. The results are shown in Tables 2 to 6 below. C/N ratio and odor measurements were performed using the same methods as in Examples 1 to 3.

In Examples 1 and 2, where vegetable oil was added, the aeration treatment was performed with the vegetable oil dispersed almost uniformly throughout the livestock wastewater. On the other hand, in Example 3, where animal fat was added, the added lard was semi-solid or creamy, emulsifying over the course of the aeration treatment and dispersing throughout the livestock wastewater. As a result of the tests conducted for the examples, all of the livestock wastewater samples in Examples 1 to 3, which were subjected to aeration fermentation with the addition of oil (vegetable oil or lard), were odorless within 24 hours and ready for use as liquid fertilizer. Furthermore, in all test plots in Examples 1 to 3, the odor began to weaken within approximately one hour of the start of the test. In particular, the odor of Example 1 (black koji mold + vegetable oil) was significantly reduced within approximately six hours of the start of the test. Furthermore, when comparing Example 2 (yellow koji mold + vegetable oil) with Example 3 (black koji mold + animal fat), the odor of Example 3, where black koji mold was added, was slightly reduced. These findings demonstrate that black koji mold has a greater odor-reducing effect. Furthermore, when comparing vegetable oil and animal fat as added fats and oils, vegetable oil, which has a lower melting point and is more easily dispersed in livestock wastewater, was found to reduce odor in a shorter time and to deodorize the livestock wastewater more quickly. In contrast, the livestock wastewater of Comparative Example 1 maintained a very strong odor from the start of the test until 24 hours after aeration treatment. This demonstrates that adding koji mold and fats and oils to livestock manure together can suppress the generation of odors and produce deodorized liquid fertilizer in an extremely short period of time, such as one day.

Furthermore, the pH values of the livestock wastewater in Examples 1-3, which contained added fats and oils, were lower than those in the Comparative Example. The dissolved oxygen concentration (DO) values were similar in Examples 1-3 and Comparative Example 1 due to the high pollution load of the livestock wastewater. However, the oxidation-reduction potential (ORP) values of Examples 1 and 2, which contained added vegetable oil, were higher. Furthermore, the C/N ratios of the Examples containing added fats and oils were significantly improved, with the C/N ratio of Example 2, which used yellow koji mold, showing the greatest change. This suggests that the use of yellow koji mold actively promotes nitrogen uptake into the fungus. The C/N ratio of Example 3, which used animal fat, was low because the added animal fat was not sufficiently dispersed in the livestock wastewater, resulting in the sample not containing the added animal fat. In Example 3, the same odor suppression effect as in Examples 1 and 2 was observed, which suggests that the koji mold in the livestock wastewater had come into sufficient contact with the animal fat, allowing the koji mold to decompose the fat and oil and use it as a carbon source for itself, while also taking in sufficient nitrogen.

[Example 4]
4. Fertilization Effect of Liquid Fertilizer of the Present Invention Two adjacent rice paddies of equal size were fertilized, one with a commercially available organic fertilizer (product name: Marui Organic, product of Marui Farm Co., Ltd.) and the other with a liquid fertilizer prepared with the same materials and method as in Example 3 (black koji mold + animal fat). The amounts of nitrogen, phosphate, and potassium applied were adjusted to be approximately equal, and the amount of fertilizer applied per tan was as shown in Table 7 below. After rice harvest, the yield per tan and the weight per 1,000 grains of rice were measured for the control and test paddies. The results are shown in Table 8 below.

The results shown in Table 8 surprisingly showed that the rice yield in the test paddy fields where the liquid fertilizer of the present invention was used was significantly improved, with the yield being 1.5 times higher than that of commercially available organic fertilizer. This demonstrates that the liquid fertilizer of the present invention has the effect of promoting plant growth and increasing the yield per unit area.

In addition, the brown rice harvested from each paddy field was analyzed for moisture (%), protein (%), amylose (%), fatty acid content (mg KOH/100g), and superoxide scavenging activity (units SOD/g), and its taste was also evaluated. Explanations of the analysis items other than superoxide scavenging activity are provided in Table 9 below, and the results of each analysis are shown in Figure 2.

The analytical results shown in Figure 2 indicate that rice grown in the test field using the liquid fertilizer of the present invention had a lower protein content than rice grown in the control field. A lower protein content allows rice to absorb water more easily during cooking, resulting in soft, fluffy rice, which contributes to improved eating quality. Furthermore, while a high amylose content results in rice with a dry, non-sticky texture, the rice grown in the test field using the liquid fertilizer of the present invention had a low amylose content, resulting in rice with a sticky, chewy texture. Furthermore, the fatty acid content of the rice grown in the test field was low, indicating less oxidation and an excellent aroma. These analytical results demonstrate that the rice grown in the test field using the liquid fertilizer of the present invention had a superior overall eating quality. Furthermore, the superoxide scavenging activity of the rice grown in the test field was higher than that of the control field, demonstrating excellent antioxidant activity. These results were obtained in the first year after applying the liquid fertilizer of the present invention, and it was speculated that continued application of this liquid fertilizer would further improve the soil and further increase the yield and quality of rice.

[Example 5]
5. Production of liquid fertilizer of the present invention 4 (continuous processing)
A continuous treatment apparatus as shown in Figure 3 was prepared, and liquid fertilizer according to the present invention was produced using this apparatus. In this continuous treatment apparatus, a livestock wastewater receiving tank was provided before an aeration treatment tank with a capacity of 10 t ( ^m3 ), and a liquid fertilizer tank was provided after the aeration treatment tank. Livestock wastewater _W1 provided from a livestock facility was first received in the livestock wastewater receiving tank and then transferred to the aeration treatment tank. Livestock wastewater _W2 aerated in the aeration treatment tank was transferred to the liquid fertilizer tank, and the sediment was used as liquid fertilizer LF.

First, ^{10 m3} of swine manure with a moisture content of approximately 99% by weight was added to the aeration tank. 50 kg of used vegetable oil (canola oil) recovered from a commercial fryer was added to the aeration tank, and 3 kg of black koji mold (Aspergillus luchuensis) seed koji (1 billion spores/1 g of seed koji) was added. Air was then blown into the livestock wastewater through an air diffuser installed in the aeration tank, and the livestock wastewater was aerated. The temperature of the livestock wastewater in the aeration tank was kept in the range of 25 to 35°C. Samples were taken from the livestock wastewater in the aeration tank at the start of aeration (day 1) and every day from the start of aeration (days 2 to 7), and the odor was evaluated using the same method as in Examples 1 to 3. The results are shown in Table 10 below.

According to these results, the livestock wastewater had a strong odor at the start of the aeration treatment, but the odor was significantly reduced by the second day, became weak on the third day, and was odorless on the fourth day. Thus, even when the treatment was scaled up to an aeration treatment tank with a capacity of 10 ^m3 , it was confirmed that the generation of foul odors from livestock manure was suppressed and the livestock wastewater was odorless, just as in Examples 1 to 3.

Next, starting from the eighth day after the start of the aeration treatment, continuous treatment was initiated in which 0.5 to 1 ton (m ³ ) of livestock wastewater was received daily into the livestock wastewater receiving tank and transferred to the aeration treatment tank daily. Before the livestock wastewater W ₁ was introduced into the aeration treatment tank, aerated livestock wastewater W ₂ was transferred to the liquid fertilizer tank in an amount equal to the amount of newly introduced livestock wastewater W _1. The amount of livestock wastewater W ₁ transferred to the aeration treatment tank and the amount of aerated livestock wastewater W ₂ transferred to the liquid fertilizer tank were 0.5 to 1 m ³ /day. The viable count of koji mold contained in the livestock wastewater in the aeration treatment tank was measured every other day. The amount of oil and fat blended was also controlled. The test was conducted over a period of four and a half months. The temperature of the livestock wastewater in the aeration treatment tank varied depending on the ambient temperature, but was in the range of 25 to 35°C (without the use of a heating device).

As a result, it was found that when the number of viable koji mold cells contained in the livestock wastewater in the aeration treatment tank becomes less than 1 x 10 ⁴ CFU/mL, the odor-suppressing effect of the livestock wastewater decreases and the urine odor remains, and that the odor-suppressing effect of the livestock wastewater also decreases when the amount of oil and fat mixed is less than 0.06 weight parts per 100 weight parts of the total livestock wastewater in the aeration treatment tank.

Furthermore, when continuous treatment was continued for about a month while adjusting the amounts of koji mold and oil added so that the live koji mold count in the livestock wastewater in the aeration tank was 1 x ¹⁰ CFU/mL or more and the amount of oil and fat mixed was about 0.1 to 1 part by weight per 100 parts by weight of the total livestock wastewater in the aeration tank, the SV30 of the livestock wastewater _W2 transferred to the liquid fertilizer tank was 8 to 10%, and improved solid-liquid separation was observed. The results of analysis of various items of the livestock wastewater _W2 in the aeration tank, the liquid fertilizer _LF recovered as sediment in the liquid fertilizer tank after transfer, and its supernatant W3 are shown in Tables 11 to 13 below.

These results indicated that the nitrogen content of the resulting liquid fertilizer LF was low, at 15 ppm, in inorganic form. This is believed to confirm that the nitrogen in the livestock wastewater was incorporated into the koji mold cell proteins, demonstrating that the liquid fertilizer LF produced in this invention is useful as a slow-release fertilizer. Furthermore, the supernatant _W3 from the liquid fertilizer tank was light yellow in color but highly transparent, and the COD and BOD values, which initially exceeded 20,000 ppm, were reduced to approximately 100 ppm, demonstrating a high level of water purification. This supernatant _W3 can be reused as commercial water, such as for cleaning livestock barns. Thus, by performing the continuous processing described above, it was possible to stably produce high-concentration liquid fertilizer in a simple manner while rapidly suppressing the generation of odors from livestock waste, and the water quality of the supernatant portion could also be purified.

The present invention is not limited to the above-described embodiments or examples, and its technical scope also includes various modified designs that do not deviate from the gist of the invention described in the claims.

The present invention provides a liquid fertilizer that promotes plant growth and also provides a method for effectively utilizing and treating livestock waste, and is therefore widely useful in industries related to agriculture, livestock farming, and wastewater treatment.

Claims (9)

A step of preparing a livestock waste liquid containing livestock manure and having a water content of 90% by weight or more;
Adding oils and fats and koji mold to the livestock wastewater;
and aerating the livestock wastewater to which the oil and fat and the koji mold have been added at a temperature of 15 to 40°C. A method for producing liquid fertilizer as described in claim 1, characterized in that the oil or fat is vegetable oil or livestock animal fat. A method for producing liquid fertilizer as described in claim 1 or 2, characterized in that 0.06 parts by weight or more of the oil and fat are added per 100 parts by weight of the livestock waste liquid. A method for producing a liquid fertilizer described in any one of claims 1 to 3, characterized in that the koji mold is seed koji. A method for producing liquid fertilizer described in any one of claims 1 to 4, characterized in that the koji mold is black koji mold or white koji mold. A method for producing liquid fertilizer described in any one of claims 1 to 4, characterized in that the koji mold is yellow koji mold. 7. The method for producing a liquid fertilizer according to claim 1, wherein the koji mold is added so that the viable cell count of the koji mold in the livestock wastewater is 1×10 ⁴ CFU/mL or more. A method for producing liquid fertilizer described in any one of claims 1 to 7, characterized in that the livestock manure is pig or cow manure. A step of preparing a livestock waste liquid containing livestock manure and having a water content of 90% by weight or more;
Adding oils and fats and koji mold to the livestock wastewater;
and aerating the livestock wastewater to which the oil and fat and the koji mold have been added at a temperature of 15 to 40°C.