Method and system for treating organic waste

Abstract

To provide an organic waste treatment method and organic waste treatment system that can stably and inexpensively perform methane fermentation of organic waste. [Solution] The organic waste treatment method according to this disclosure is an organic waste treatment method comprising methane fermentation of a mixture of chicken manure and food waste, wherein the mixture contains 5% or more of the food waste.

Description

[Technical Field]

[0001] This disclosure relates to a method for treating organic waste and an organic waste treatment system. [Background technology]

[0002] A known method involves treating organic waste by methane fermentation. For example, Patent Document 1 discloses a technology for methane fermentation of chicken manure. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 4512823 [Overview of the project] [Problems that the invention aims to solve]

[0004] The inventors have identified the following problems with respect to organic waste treatment methods and organic waste treatment systems. Chicken manure contains uric acid, resulting in a high nitrogen concentration, which can cause uric acid to convert to ammonia in the fermentation tank. Since ammonia can inhibit methane fermentation, measures such as diluting the waste with water to lower the nitrogen concentration and installing ammonia removal equipment are taken to ensure stable methane fermentation. However, diluting the waste with water increases the amount of treated water, thus increasing the cost of treating the treated water, and also increases the equipment cost due to the increased number of fermentation tanks. Furthermore, installing ammonia removal equipment increases the cost of installing the equipment. Therefore, there has been a need for the development of a low-cost, stable technology for methane fermentation of organic waste.

[0005] This disclosure is made in view of these challenges and aims to provide an organic waste treatment method and an organic waste treatment system that can stably and inexpensively perform methane fermentation of organic waste. [Means for solving the problem]

[0006] One embodiment for achieving the above objective is: A method for treating organic waste, which involves methane fermentation of a mixture of chicken manure and food waste, The mixture contains 5% or more of the food waste.

[0007] One embodiment for achieving the above objective is: A method for treating organic waste by methane fermentation of a mixture of chicken manure and chicken eggs, The mixture contains less than 20% of the chicken eggs.

[0008] One embodiment for achieving the above objective is: An organic waste treatment system that uses methane fermentation to process a mixture of chicken manure and food waste, The mixture contains 5% or more of the food waste.

[0009] One embodiment for achieving the above objective is: An organic waste treatment system that uses methane fermentation to process a mixture of chicken manure and chicken eggs, The mixture contains less than 20% of the chicken eggs. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide an organic waste treatment method and an organic waste treatment system that can stably and inexpensively perform methane fermentation of organic waste. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing an example configuration of an organic waste treatment system according to an embodiment. [Figure 2] This is a flowchart illustrating an example of the flow of an organic waste treatment method according to an embodiment. [Figure 3] This graph shows the amount of methane produced when a mixture containing food waste is subjected to methane fermentation. [Figure 4] It is a graph showing the amount of methane generated when a mixture containing chicken eggs is anaerobically digested.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions may be omitted as necessary for clarity of explanation. Also, for ease of understanding, the scales of each part in the drawings may be different from the actual ones.

[0013] FIG. 1 is a block diagram showing a configuration example of an organic waste treatment system 100 according to an embodiment. The organic waste treatment system 100 is a system that treats a mixture containing chicken manure and an additional material by anaerobic digestion. The additional material is food waste or chicken eggs. The food waste includes leftover food, cooking waste, etc., and is, for example, waste discarded from a cafeteria. The organic waste treatment system 100 is a system that calculates and presents the amount and type of the additional material to be added according to the amount of chicken manure to be treated.

[0014] As shown in FIG. 1, the organic waste treatment system 100 includes at least an additional material amount calculation unit 110 and a display unit 160, and may further include a gas amount calculation unit 120, a power generation amount calculation unit 130, a compatibility estimation unit 140, and a recovery income calculation unit 150. The additional material amount calculation unit 110 receives an input of the amount of high-nitrogen-concentration organic waste to be treated, that is, chicken manure, and calculates the amount of additional material to be added based on the following mathematical formula (1). The additional material amount calculation unit 110 calculates the amount of additional material for each type of additional material. When the additional material is food waste, the additional material amount calculation unit 110 calculates the amount of food waste to be added so that the food waste is contained in the mixture of chicken manure and food waste at a weight ratio of 5% or more. When the additional material is chicken eggs, the additional material amount calculation unit 110 calculates the amount of chicken eggs to be added so that the chicken eggs are contained in the mixture of chicken manure and chicken eggs at a weight ratio of less than 20%. Mixtures containing 5% or more of food waste and mixtures containing less than 20% of chicken eggs can be efficiently methane-fermented, which is preferable. [Number]

[0015] Here, TC represents the total carbon amount, and TN represents the total nitrogen amount. TC / TN max is the TC / TN ratio at the maximum of the co-digestion performance index (CPI). TC / TN i is the TC / TN ratio of the high-nitrogen-concentration organic waste, that is, chicken manure, which is the substrate. TC / TN add is the TC / TN ratio of the additional material to be additionally input. α i is the estimated amount of high-nitrogen-concentration organic waste. β i is the amount of additional material to be additionally input.

[0016] The gas quantity calculation unit 120 calculates the amount of methane gas generated when the mixture is subjected to methane fermentation based on the additional material amount calculated by the additional material amount calculation unit 110 and the following mathematical formula (2). Further, the gas quantity calculation unit 120 may calculate the amount of methane gas generated when the high-nitrogen-concentration organic waste is subjected to methane fermentation without adding an additional material. In this case, the gas quantity calculation unit 120 may calculate how much the methane gas increases when an additional material is added and methane fermentation is performed.

Number

[0017] Note that VS is volatile substances. CPI TC / TN is a mixed fermentation evaluation index assumed from the TC / TN ratio. VS ai is the VS ratio (%) of the high-nitrogen-concentration organic waste. α gas is the amount of methane gas generated (m 3 / g-VS) when the high-nitrogen-concentration organic waste is fermented alone. VS βadd is the VS ratio (%) of the additional raw material to be additionally inputted. β gas is the amount of methane gas generated (m 3 / g-VS) when the additionally inputted additional raw material is fermented alone.

[0018] The power generation amount calculation unit 130 calculates the power generation amount generated by using the methane gas generated by methane fermentation based on the amount of methane gas generated calculated by the gas quantity calculation unit 120 and the following mathematical formula (3). When the amount of increased methane gas generated when methane fermentation is performed by adding an additional material is calculated, the power generation amount calculation unit 130 may calculate the difference in the power generation amount due to the increased amount of methane gas.

Number

[0019] Note that J is the calorific value of methane (kcal / m 3D is the power generation efficiency (%). E is the heat energy equivalent value (kcal / kWh). The power generation amount calculation unit 130 may also further calculate the revenue from selling electricity based on the calculated power generation amount. Revenue from selling electricity is the amount of revenue that can be expected to be obtained by selling the generated electricity. If the amount of methane gas that increases when additional materials are added and methane fermentation is performed has been calculated, the power generation amount calculation unit 130 may also calculate the difference in revenue from selling electricity due to the increase in methane gas.

[0020] The compatibility estimation unit 140 estimates the type of additional material that is compatible with high nitrogen concentration organic waste. Specifically, based on the amount of additional material calculated by the additional material amount calculation unit 110, the compatibility estimation unit 140 selects the type of additional material that minimizes the amount of additional material to be added as the type of additional material that is compatible with high nitrogen concentration organic waste.

[0021] The recovery revenue calculation unit 150 calculates the amount of revenue that can be obtained when additional materials are recovered. Food waste discarded by businesses such as restaurants generally incurs disposal costs. Therefore, when food waste is used as additional materials, the business can receive a fee for the recovery of the food waste from the business that discards the food waste. The fee for the recovery of food waste is generally determined on a per-weight basis. The recovery revenue calculation unit 150 calculates the recovery revenue based on the amount of additional materials calculated by the additional material amount calculation unit 110 and the recovery revenue of additional materials determined on a per-weight basis.

[0022] The display unit 160 displays the data calculated and estimated in the organic waste treatment system 100 in a way that is visible to the user. Specifically, the display unit 160 may display the following data. The amount of additional material calculated by the additional material amount calculation unit 110 The amount of methane gas generated when methane fermentation is carried out using only high nitrogen concentration organic waste, and the amount of methane gas generated when methane fermentation is carried out using a mixture with additional materials, as calculated by the gas amount calculation unit 120. The amount of methane gas produced, which increases by adding additional materials and performing methane fermentation, as calculated by the gas quantity calculation unit 120. • The amount of electricity generated by the generated methane gas and the amount of electricity generated by the increasing amount of generated methane gas, as calculated by the power generation calculation unit 130. • The power generation calculation unit 130 calculates the revenue from selling electricity generated from methane gas and the revenue from selling electricity generated from the increased amount of methane gas. • The revenue collection calculation unit 150 calculated the revenue collection • Compatibility of each type of additional material with high-nitrogen-concentration organic waste.

[0023] Next, with reference to Figure 2, the flow of the organic waste treatment method according to the embodiment will be explained. In the organic waste treatment method according to the embodiment, first, the amount of high nitrogen concentration organic waste to be treated is received as input (step S101). Next, the additional material amount calculation unit 110 calculates the amount of additional material for each type of additional material based on the amount of high nitrogen concentration organic waste received as input in step S101 (step S102).

[0024] Next, the gas quantity calculation unit 120 calculates the amount of methane gas generated when only the high nitrogen concentration organic waste received in step S101 is subjected to methane fermentation. The gas quantity calculation unit 120 also calculates the amount of methane gas generated when the additional material calculated in step S102 is added and methane fermentation is performed (step S103).

[0025] Next, the power generation calculation unit 130 calculates the amount of power generated and the revenue from selling electricity when power is generated using methane gas, based on the amount of methane gas generated calculated in step S103. The power generation calculation unit 130 also calculates the amount of power generated and the revenue from selling electricity that would increase when methane fermentation is performed with additional materials, based on the amount of methane gas generated that increases when methane fermentation is performed with additional materials, as calculated in step S103 (step S104).

[0026] The compatibility estimation unit 140 estimates the compatibility between the high nitrogen concentration organic waste input in step S101 and each additional material based on the amount of additional material for each type of additional material calculated in step S102 (step S105). The recovery revenue calculation unit 150 calculates the recovery revenue when the additional material is recovered based on the amount of additional material calculated in step S102 (step S106). The display unit 160 displays the data calculated and estimated in steps S102 to S106 in a way that is visible to the user (step S107). The user refers to the data displayed on the display unit 160 to determine the additional material and the amount of additional material to be used, and processes the high nitrogen concentration organic waste.

[0027] Thus, by mixing appropriate types and quantities of additional materials with high-nitrogen-concentration organic waste and performing methane fermentation, stable treatment can be achieved. Furthermore, since the additional materials are food waste or chicken eggs, the cost of preparation is low. Therefore, the organic waste treatment method according to this embodiment can treat organic waste at low cost. [Examples]

[0028] Next, embodiments of the present disclosure will be described. A sample of the organic waste treatment method related to this disclosure has been prepared as follows.

[0029] <Ingredients for the mixture> The organic waste consisted of 1.5g of chicken manure. The additional material consisted of food waste or chicken eggs. The food waste was garbage discarded from the cafeteria. The organic waste and additional material were mixed in weight ratios of 1:0, 100:1, 100:5, 10:1, 10:2, and 0:1.

[0030] <Fermentation conditions> 100 ml of digestate was added to the above mixture, and a mixed fermentation test was conducted at 37°C. The digestate was from a pig manure plant.

[0031] <Test Results> Figure 3 shows the test results when the additional material is food waste. Figure 4 shows the test results when the additional material is chicken eggs. The dotted lines in Figures 3 and 4 represent the theoretically calculated amount of methane gas produced. The solid lines in Figures 3 and 4 represent the actual amount of methane gas produced. As shown in Figure 3, when the mixture contained 5% or more food waste, the actual amount of methane gas produced was greater than the theoretically calculated amount. Also, as shown in Figure 4, when the mixture contained less than 20% chicken eggs, the actual amount of methane gas produced was greater than the theoretically calculated amount. From this, it was confirmed that methane fermentation can be efficiently carried out when the mixture contains 5% or more food waste and less than 20% chicken eggs.

[0032] This disclosure is not limited to the embodiments described above, and may be modified as appropriate without departing from its spirit. [Explanation of symbols]

[0033] 100 Organic Waste Treatment Systems 110 Additional material amount calculation section 120 Gas volume calculation unit 130 Power generation calculation unit 140 Compatibility Estimation Unit 150 Revenue Calculation Department 160 Display section

Claims

1. A method for treating organic waste, which involves methane fermentation of a mixture of chicken manure and food waste, The mixture contains 5% or more of the food waste. Methods for treating organic waste.

2. A method for treating organic waste by methane fermentation of a mixture of chicken manure and chicken eggs, The mixture contains less than 20% of the chicken eggs. Methods for treating organic waste.

3. An organic waste treatment system that uses methane fermentation to process a mixture of chicken manure and food waste, The mixture contains 5% or more of the food waste. Organic waste treatment system.

4. An organic waste treatment system that uses methane fermentation to process a mixture of chicken manure and chicken eggs, The mixture contains less than 20% of the chicken eggs. Organic waste treatment system.

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