How to recycle food waste

Abstract

To provide a more effective recycling method in processing of food wastes such as coffee grounds and used green tea leaves and effective utilization of processed products.SOLUTION: Food wastes such as coffee grounds or used green tea leaves are subjected to hydrothermal treatment to form a hydrothermal char involving higher fatty acids such as palmitic acid. Higher fatty acids are extracted from the obtained hydrothermal char for effective utilization as raw materials for cosmetics, detergents, coatings, synthetic resins, etc. in accordance with kinds of higher fatty acids. Higher fatty acid-extracted residues can be converted to fuels, etc. for reuse.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for recycling food waste, and is directed to a method for extracting higher fatty acids from, for example, coffee grounds or green tea leaves, and further enabling the effective use of the residues. [Background technology]

[0002] The treatment of municipal solid waste has become an important issue from the standpoint of cost and environmental problems, and there is a need for the development of various recycling technologies as a field of biomass utilization technology.

[0003] Conventional techniques relating to the processing of coffee grounds include the inventions described in the following Patent Documents 1 to 3, for example.

[0004] Patent Document 1 discloses a method for producing a carbonized product at a relatively low temperature with a high recovery rate by hydrothermal carbonization of a plant-based raw material including coffee grounds in ion-exchanged water at a temperature of 150 to 350°C.

[0005] Patent Document 2 discloses a biomass processing method for efficiently subjecting biomass such as coffee grounds to methane fermentation.

[0006] Patent Document 3 discloses a methane fermentation method using coffee grounds, which involves solubilizing the coffee grounds by heating them at 60°C or higher and adding a dilution medium in an amount equivalent to 5 to 10 times the dry weight of the coffee grounds. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2016-150894 A [Patent Document 2] JP 2015-003280 A [Patent Document 3] JP 2011-206737 A Summary of the Invention [Problem to be solved by the invention]

[0008] The coffee grounds processing techniques described in the above Patent Documents 1 to 3 are basically aimed at producing a carbonized product and effectively utilizing it as fuel.

[0009] However, when taking into consideration the production costs of the carbonized material, its value and effectiveness as a fuel, and its impact on the environment, it cannot necessarily be said to be an efficient recycling technology.

[0010] The present invention aims to provide a more efficient recycling method for treating food waste such as coffee grounds and green tea leaves and for effectively utilizing the treated materials. [Means for solving the problem]

[0011] The method for recycling food waste of the present invention is characterized in that food waste is subjected to hydrothermal treatment to produce hydrothermal char containing higher fatty acids.

[0012] In the present invention, for example, grounds from coffee extraction or grounds from tea extraction such as green tea, black tea, or barley tea can be used as food waste.

[0013] By extracting higher fatty acids from the hydrothermal char obtained by the present invention, they can be effectively used as raw materials for cosmetics, detergents, paints, synthetic resins, etc., depending on the type of higher fatty acid. In addition, the residue from which higher fatty acids are extracted can be used for fuel recycling and carbonization such as activated carbon. and It can be used as such.

[0014] The hydrothermal treatment is carried out at about 150 to 220° C., preferably at 150 to 200° C. The yield of hydrothermal char is high when the hydrothermal treatment temperature is around 180° C., but the yield tends to decrease when the temperature exceeds 220° C.

[0015] The hydrothermal treatment time varies depending on the type of food waste, but is preferably about 3 to 48 hours, more preferably about 3 to 24 hours. The longer the hydrothermal treatment time, the higher the yield of hydrothermal char tends to be, but depending on the type of food waste, the rate of increase in yield may be low. stomach It is unclear whether the acidity is increased, and long-term treatment is not efficient. In addition, when the organic acid in the residual liquid is used for, for example, dissolving slag or eluting metals, the acidity tends to decrease (pH increases) as the hydrothermal treatment time increases, so the hydrothermal treatment time is preferably within 24 hours or 12 hours. Effect of the Invention

[0016] According to the present invention, food waste such as coffee grounds and green tea grounds can be hydrothermally treated to produce pulp and paper. Michi By extracting the higher fatty acids from the hydrothermal char, they can be effectively used as raw materials for cosmetics, detergents, paints, synthetic resins, etc., depending on the type of the higher fatty acids. In addition, the residue from which the higher fatty acids are extracted can be used as fuel, etc. [Brief description of the drawings]

[0017] [Figure 1] This graph shows the hydrothermal char yields for coffee grounds, green tea grounds, barley tea grounds, and black tea grounds when the hydrothermal treatment temperatures were 180°C and 220°C in tests on the food waste recycling method of the present invention. [Diagram 2] FIG. 2 is a graph showing the pH of the residual liquid after hydrothermal treatment in the test of FIG. [Diagram 3] This is a graph showing the structural analysis by X-ray diffraction of hydrothermal char obtained by hydrothermal treatment for 24 hours for coffee grounds, black tea grounds, green tea grounds, and barley tea grounds in the food waste recycling method of the present invention. [Figure 4] This graph shows the structural analysis by X-ray diffraction of hydrothermal char obtained at various treatment temperatures (180°C, 220°C) and times (3 hours to 24 hours) when coffee husks were hydrothermally treated. [Diagram 5] This graph shows the structural analysis by X-ray diffraction of hydrothermal char obtained at different treatment temperatures (180℃, 220℃) and times (12 hours, 24 hours) when green tea was hydrothermally treated. [Figure 6] This is an SEM photograph taken with a scanning electron microscope (SEM) of coffee husk char after coffee husks were hydrothermally treated at 220°C for 24 hours (1 day). [Figure 7] 1 is a graph showing the X-ray diffraction intensity of palmitic acid and cetanol. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Tests conducted to confirm the effects of the present invention will now be described. Raw material shells: coffee, green tea, barley tea shells, black tea shells Hydrothermal treatment conditions: 180℃, 220℃, 3 to 24 hours Solvent: H2O

[0019] After synthesis, the black residue (hydrothermal char) was recovered by solid-liquid separation. The test results are shown in Figs.

[0020] Figure 1 is a graph showing the hydrothermal char yield for coffee grounds, green tea grounds, barley tea grounds, and black tea grounds when the hydrothermal treatment temperatures are 180°C and 220°C, and Figure 2 is a graph showing the pH of the residual liquid after hydrothermal treatment.

[0021] In these graphs, coffee grounds are represented by ● when hydrothermally treated at 180°C, by ◯ when hydrothermally treated at 220°C, green tea grounds are represented by ▲ when hydrothermally treated at 180°C, by △ when hydrothermally treated at 220°C, barley tea grounds are represented by ■ when hydrothermally treated at 180°C, by □ when hydrothermally treated at 220°C, black tea grounds are represented by ▼ when hydrothermally treated at 180°C, and by ▽ when hydrothermally treated at 220°C.

[0022] When coffee grounds were hydrothermally treated at 180°C (●) versus 220°C (◯), the yield of hydrothermal char was higher when the grounds were hydrothermally treated at 180°C.

[0023] When coffee grounds were hydrothermally treated at 180°C, the yield of hydrothermal char was highest when treated for 24 hours. When coffee grounds were hydrothermally treated at 220°C, the yield of hydrothermal char was highest when treated for 12 hours, but the difference due to the treatment time was not very clear.

[0024] The pH of the organic acids in the residual liquid from coffee grounds tended to be slightly higher at 220°C than at 180°C, but no significant difference was observed in relation to the hydrothermal treatment time.

[0025] When green tea leaves were hydrothermally treated at 180°C (▲) and 220°C (△), the yield of hydrothermal char was higher when hydrothermal treatment was performed at 180°C.

[0026] For green tea leaves, the yield tended to decrease when hydrothermal treatment was performed for a long time at both 180℃ and 220℃. The pH of the organic acids in the residual liquid from green tea leaves tended to be higher the longer the treatment (the shorter the treatment the stronger the acidity). From this, it is thought that for green tea leaves, hydrothermal treatment for 3 to 12 hours is preferable rather than 24 hours.

[0027] Furthermore, Figure 2 shows that when comparing coffee grounds and green tea grounds, the pH of the organic acids derived from coffee grounds is lower.

[0028] Although the amount of data for barley tea leaves and black tea leaves was not necessarily sufficient, results for black tea leaves were similar to those for green tea leaves, and results for barley tea leaves were intermediate between those for coffee leaves and green tea leaves.

[0029] Figure 3 shows a graph of the structure analysis by X-ray diffraction of hydrothermal chars obtained by hydrothermal treatment of coffee grounds (CF), black tea grounds (ET), green tea grounds (GT), and barley tea grounds (BT) at 220°C for 24 hours. E denotes chars washed with ethanol.

[0030] In CF220 / 24, which was obtained by hydrothermal char from coffee husks, two highly intense diffraction peaks were observed at around 21.4° and 23.7° (indicated by dotted lines in Figure 3).

[0031] In addition, Pal Michi The characteristic high intensity peaks of carboxylic acid are at 2.7°, 7.22°, 21.5°, and 24.1°. Michi Other higher fatty acids detected were palladium, phosphate, and glycerol. Michi In addition to carboxylic acid, stearic acid was also detected. Michi The graph shows the X-ray diffraction intensity of acetic acid (top) and cetanol (bottom).

[0032] For GT220 / 24, which was obtained from hydrothermal char from green tea leaves, two intense diffraction peaks were observed at around 21.4° and 23.7°.

[0033] The CF220 / 24E and GT220 / 24E were washed with ethanol to remove the pulp from the hydrothermal char. Michi Since higher fatty acids such as carboxylic acid and carboxylic acid were removed, pulp and cellulose were obtained from the hydrothermally treated char. Michi Diffraction peaks of phosphoric acid, etc. disappeared.

[0034] Figure 4 is a graph showing X-ray diffraction analysis of coffee grounds that were hydrothermally treated at 220°C for 3, 6, and 24 hours, and at 180°C for 12 and 24 hours. The grounds that were hydrothermally treated at 220°C are shown as CF220 / 3, CF220 / 6, and CF220 / 24, while the grounds that were hydrothermally treated at 180°C for 12 and 24 hours are shown as CF180 / 12 and CF180 / 24.

[0035] For chars hydrothermally treated at 220°C, clear peaks were observed at around 2.5° and 21.4° for CF220 / 3 and CF220 / 6, and peaks were also observed for CF220 / 24.

[0036] The char hydrothermally treated at 180°C has a clearer peak than the char hydrothermally treated at 220°C, and in addition to the peaks near 2.5° and 21.4°, a weak peak is also seen near 23.5°. Between CF180 / 12 and CF180 / 24, the peak is clearer in the case of CF180 / 12.

[0037] Figure 5 is a graph showing the X-ray diffraction analysis of green tea leaves that have been hydrothermally treated. The samples that were hydrothermally treated at 220°C for 24 hours are shown as GT220 / 24, and the samples that were hydrothermally treated at 180°C for 12 and 24 hours are shown as GT180 / 12 and CF180 / 24.

[0038] In GT220 / 24, a relatively clear peak is seen at around 21.4°, but in GT180 / 24 and CF180 / 12, the X-ray diffraction intensity at the peak is higher, and peaks can be confirmed at around 2.5°, 21.4°, and 23.5°.

[0039] From the above test results, it was found that the hydrothermal char obtained by hydrothermal treatment of coffee grounds, green tea grounds, etc. Michi It was confirmed that it contains higher fatty acids such as carboxylic acid.

[0040] Figure 6 shows SEM images of coffee husks hydrothermally treated at 220°C for 24 hours. (b) is an enlarged image of (a).

[0041] The generation of spherical char was also observed in the photograph in Figure 6. Therefore, it is expected that the carbonaceous material derived from coffee can be used as porous carbon, for example for ethylene adsorption.

Claims

1. A method for recycling food waste, which comprises hydrothermal treating the food waste to produce hydrothermal char containing higher fatty acids, characterized in that the hydrothermal treatment is carried out at a temperature of 150 to 200°C for 3 to 48 hours.

2. 2. The method for recycling food waste according to claim 1, further comprising extracting said higher fatty acids from said hydrothermal char.

3. 3. The method for recycling food waste according to claim 1 or 2, wherein the food waste is coffee or green tea extract grounds.

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