A method for fixing and storing organic carbon in kitchen waste in soil

Abstract

The present invention discloses a method for fixing and storing organic carbon from food waste in soil. The food waste is pretreated, and the pretreated food waste is mixed with water for washing and then drained. The washed food waste is pre-frozen and subjected to vacuum freeze-drying treatment to obtain a porous structure material. The obtained porous structure material is mixed with a biomass material, crushed and stirred evenly to obtain a food waste organic carbon material. The obtained food waste organic carbon material is applied to the soil and the soil is turned regularly to achieve ecological carbon fixation in the soil. The invention not only provides a method for the effective treatment and resource utilization of perishable solid waste, food waste, but also can improve and enhance soil productivity. The technological process is relatively simple, omitting the complex fermentation process, being easy to promote and implement, and not using chemical fertilizers. It is a very environmentally friendly, ecological and effective carbon fixation method.

Description

Technical Field

[0001] The present invention belongs to the technical field of harmless treatment and resource utilization of solid waste, and relates to a method for fixing and storing organic carbon in food waste in soil. Background Art

[0002] Diet is the primary material basis for human survival and development. Food waste generated during the diet process is the most common waste in urban daily life, including catering waste and kitchen waste, accounting for about 37% - 62% of urban domestic waste. It mainly comes from food processing leftovers and edible residues generated by catering service industries, families, and canteens of enterprises and institutions. The output of food waste shows an increasing trend year by year, and there is a huge gap between the annual treatment capacity and the annual output. Since food waste contains a large amount of organic matter, it is extremely easy to rot, emit a stench, breed harmful substances, and become a breeding ground for pests such as flies. The timely and effective treatment of food waste is related to the food safety of the people, the environmental hygiene of the city, and energy conservation and consumption reduction, and has become one of the most concerned livelihood focus issues. How to efficiently dispose of food waste and utilize it as a resource to turn waste into treasure is the focus of the industry's development, and there is an urgent need for efficient, environmentally friendly, and low-carbon high-value utilization ways and methods for food waste.

[0003] Soil is a repository for material and biogeochemical cycles and the material basis for humans to obtain food and other renewable resources. As an important part of the natural ecosystem, soil connects the atmosphere, hydrosphere, and biosphere and is one of the main components of the earth's atmospheric carbon pool, ocean carbon pool, lithosphere carbon pool, and terrestrial ecosystem carbon pool. The soil carbon pool and the vegetation carbon pool are the main components of the terrestrial ecosystem carbon pool. The soil carbon pool accounts for more than 90%, is 3 - 4 times that of the vegetation carbon pool, and 2 - 3 times that of the atmospheric carbon pool. It can be seen that soil has a huge carbon sequestration capacity and great potential for carbon fixation. Therefore, enhancing the ecological carbon sequestration capacity, giving full play to the carbon fixation role of soil, and increasing the carbon sequestration increment of the soil ecosystem are important ways for future carbon reduction. However, in the field of carbon sequestration research, the attention paid to soil carbon sequestration is far less than that of forest carbon sequestration, and relevant research on the carbon fixation potential of soil needs to be strengthened.

[0004] Food waste is essentially food. Chemically, it mainly consists of components such as carbohydrates, oils and fats, proteins, inorganic salts, and cellulose. Among them, carbohydrates account for about 30% - 60%, proteins account for 6% - 10%, and oils and fats account for 7% - 30%, having typical resource attributes. Using the organic matter of food waste to repair and improve the soil, first, utilize the strong carbon sink capacity of the soil to fix organic carbon in the soil; second, through the repair and improvement of the soil, the plant production in poor soil increases, the soil vegetation is restored, and the plants themselves have the ability to fix carbon dioxide. In this way, from two aspects, the carbon sequestration and sink enhancement effect of the soil is strengthened. It can be seen that soil improvement based on food waste is a restoration method to increase soil carbon sink, which can fully explore the huge emission reduction and sink enhancement effect of the soil carbon pool, restore the original carbon storage capacity of the soil and the carbon sequestration effect of the vegetation, improve the soil carbon capacity, reduce energy consumption and carbon emissions during the soil improvement process, and will become an important way for carbon sequestration and sink enhancement in the future.

[0005] To improve the carbon sequestration ability of the soil, Chinese Patent CN104641756A discloses a method for improving the carbon sequestration ability of mine soil; Chinese Patent CN107509406B discloses a method for rapidly improving the carbon sequestration ability of industrial and mining wasteland soil; Chinese Patent CN114287194A discloses a method for improving the carbon sequestration ability of newly reclaimed cultivated land area soil; Chinese Patent CN109804746B discloses a method for carbon sequestration in field sandy soil; Chinese Patent CN114394867A discloses a carbon sequestration agent for dry farmland soil, its preparation method and application. These technologies show that it is feasible to sequester carbon by utilizing the strong carbon sink capacity of the soil. However, based on the principles of soil physical, chemical, and biological improvement and restoration, there are two obvious deficiencies in the existing technologies. One is that the repair materials used require a fermentation process. Usually, fermentation not only takes a long time but also has a complex operation implementation process and is prone to generating malodorous gases, etc. The other is that there are varying degrees of addition of chemical fertilizers such as urea and potassium dihydrogen phosphate during the repair process. Dependence on chemical fertilizers severely restricts the practical application and promotion of them. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems in the existing technologies and provide a method for fixing and storing the organic carbon of food waste in the soil, eliminating the complex fermentation process and not using chemical fertilizers, sequestering the organic carbon in the soil, and improving soil productivity and carbon sequestration effect.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A method for fixing and storing the organic carbon of food waste in the soil, comprising the following steps:

[0009] Pretreat the food waste, mix the pretreated food waste with water for cleaning, and drain it;

[0010] Pre-freeze the cleaned kitchen waste and subject it to vacuum freeze-drying to obtain a porous structure material;

[0011] Mix the obtained porous structure material with a biomass material, crush and stir evenly to obtain a kitchen waste organic carbon material;

[0012] Apply the obtained kitchen waste organic carbon material to the soil and turn the soil regularly.

[0013] Furthermore, the pretreatment of the kitchen waste includes sorting out and removing non-degradable impurities, and the impurities are one or more of metals, glass, plastics, and ceramics.

[0014] Furthermore, the temperature of the water is 50 - 70°C, and the mass-volume ratio of the pretreated kitchen waste to the hot water is 1:3 - 7.

[0015] Furthermore, the number of times of mixed cleaning is 1 - 3 times, and the draining time is 10 - 30 min.

[0016] Furthermore, the pre-freezing temperature is -18 - -4°C, the pre-freezing time is 7 - 10 h. During the vacuum freeze-drying process, the cold trap temperature is -80 - -40°C, the vacuum degree of sublimation drying is 40 - 100 Pa, and the drying time is 10 - 20 h.

[0017] Furthermore, the biomass material is one or more of sawdust, straw, corncobs, or rice husks.

[0018] Furthermore, the mass ratio of the kitchen waste material to the biomass material is 1:2 - 10.

[0019] Furthermore, the particle size of the kitchen waste organic carbon material is 10 mm or less.

[0020] Furthermore, the application rate of the kitchen waste organic carbon material is 0.5 - 3 tons per mu, and the number of times of turning the soil during this period is 1 - 3 times.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a method for fixing and sequestering organic carbon from kitchen waste in soil. The organic carbon is derived from kitchen waste and common biomass materials, which is green and environmentally friendly. The organic carbon and biomass materials are compatible and have a coupling and complementary effect in terms of organic matter components and trace element content, synergistically enhancing the effect. It does not require complex fermentation processes and the use of chemical fertilizers, etc. The process flow is simple, easy to promote and implement, and has a good carbon sequestration effect. It is a very environmentally friendly, ecological and effective carbon sequestration method. First, the selected kitchen waste is essentially food and rich in organic carbon, which is suitable as an organic nutrient source for soil, improving the physical and chemical properties of infertile soil, fixing organic carbon in the soil while increasing soil fertility. Second, after freeze-drying, the kitchen waste can form a rich pore structure, which can improve soil aeration and the redox environment of the soil. At the same time, it is compatible with inexpensive biomass materials to adjust the carbon content, eliminating the need for complex fermentation processes and being directly applied to the soil to promote plant growth and enhance the soil's carbon sequestration ability. Third, the processed kitchen waste organic carbon material with rich pores can also serve as a carrier for soil microorganisms, facilitating the enrichment and proliferation of microorganisms, increasing soil biodiversity, and improving soil productivity and carbon sequestration effect. Finally, kitchen waste has a wide source and large output. While saving high treatment costs, it realizes the recycling of waste resources, has a great cost advantage, and also provides an effective way for the effective treatment and high-value utilization of organic perishable solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is an infrared spectrogram of the kitchen waste organic carbon material prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0026] Accordingly, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings:

[0028] The present invention provides a method for fixing and storing organic carbon from kitchen waste in soil, comprising the following steps:

[0029] After the kitchen waste is collected, it is pretreated by sorting out non-degradable impurity components such as metals, glass, plastics, and ceramics.

[0030] The sorted and impurity-removed kitchen waste is mixed with hot water at 50-70°C in a mass-to-volume ratio of m / v of 1:3-7 and washed 1-3 times, and then drained. The draining time is controlled within 10-30 minutes to remove the grease on the surface of the kitchen waste.

[0031] The washed kitchen waste is pre-frozen at -18 to -4°C for 7-10 hours. The pre-frozen kitchen waste is taken and subjected to vacuum freeze-drying. It is dried for 10-20 hours at a cold trap temperature of -80 to -40°C and a sublimation drying vacuum degree of 40-100 Pa to obtain a porous kitchen waste material.

[0032] The vacuum freeze-dried kitchen waste material is mixed with a biomass material in a mass ratio of 1:2-10. The mixed material is pulverized and stirred evenly, and the particle size after pulverization is ≤10 mm to obtain a kitchen waste organic carbon material.

[0033] The obtained kitchen waste organic carbon material is applied to the soil at a dosage of 0.5-3 tons per mu, and the soil is turned over 1-3 times during this period.

[0034] Further, the biomass material is one or more of sawdust, straw, corncob, or rice husk.

[0035] Example 1:

[0036] Collect food waste, sort out and remove non-degradable impurity components such as metals, glass, plastics, and ceramics. Take 15 kg of sorted and impurity-removed food waste and mix it with 90 L of hot water at a temperature of 55 °C for 1 wash, then drain for 15 min to remove the grease on the surface of the food waste. Put the washed food waste into a freezer and pre-freeze it at -5 °C for 7 h. Then control the cold trap temperature of the vacuum freeze dryer at -40 °C and the sublimation drying vacuum degree at 60 Pa, and carry out vacuum freeze drying treatment for 17 h. Take 10 kg of the vacuum freeze-dried food waste and mix it with 70 kg of corncobs, and then carry out stirring and crushing treatment. The particle size after crushing is ≤ 10 mm. Then conduct a field test on the soil carbon sequestration ability. The test field area is 9 square meters (3×3), and the soil is the soil at a depth of 0 - 20 cm in the plough layer. Apply the obtained food waste organic carbon material to the soil at a application rate of 2.0 tons per mu, and deep plough 3 times during the test period.

[0037] Example 2

[0038] Collect food waste, sort out and remove non-degradable impurity components such as metals, glass, plastics, and ceramics. Take 15 kg of sorted and impurity-removed food waste and mix it with 60 L of hot water at a temperature of 60 °C for 2 washes, then drain for 20 min to remove the grease on the surface of the food waste. Put the washed food waste into a freezer and pre-freeze it at -10 °C for 8 h. Then control the cold trap temperature of the vacuum freeze dryer at -60 °C and the sublimation drying vacuum degree at 100 Pa, and carry out vacuum freeze drying treatment for 12 h. Take 10 kg of the vacuum freeze-dried food waste and mix it with 30 kg of wheat straws, and then carry out stirring and crushing treatment. The particle size after crushing is ≤ 10 mm. Then conduct a field test on the soil carbon sequestration ability. The test field area is 9 square meters (3×3), and the soil is the soil at a depth of 0 - 20 cm in the plough layer. Apply the obtained food waste organic carbon material to the soil at a application rate of 1.0 tons per mu, and deep plough 2 times during the test period.

[0039] Example 3

[0040] Collect food waste, sort out and remove non-degradable impurity components such as metals, glass, plastics, and ceramics. Take 15 kg of the sorted and impurity-removed food waste and mix it with 75 L of hot water at a temperature of 70 °C for cleaning 3 times, and then drain for 30 min to remove the grease on the surface of the food waste. Put the cleaned food waste into a freezer and pre-freeze it at -15 °C for 9 h. Then control the cold trap temperature of the vacuum freeze dryer to -70 °C and the sublimation drying vacuum degree to 80 Pa, and carry out vacuum freeze-drying treatment for 15 h. Take 10 kg of the vacuum freeze-dried food waste and mix it with 50 kg of corn straw, and then carry out stirring and crushing treatment. After crushing, the particle size is ≤ 10 mm. Then carry out a field test on the soil carbon sequestration ability. The test field area is 9 square meters (3×3), and the soil is the soil at a depth of 0 - 20 cm in the tillage layer. Apply the obtained food waste organic carbon material to the soil at a application rate of 1.5 tons per mu, and deep plow 3 times during the test period.

[0041] Example 4

[0042] Collect food waste, sort out and remove non-degradable impurity components such as metals, glass, plastics, and ceramics. Take 15 kg of the sorted and impurity-removed food waste and mix it with 45 L of hot water at a temperature of 50 °C for cleaning 1 time, and then drain for 10 min to remove the grease on the surface of the food waste. Put the cleaned food waste into a freezer and pre-freeze it at -5 °C for 7 h. Then control the cold trap temperature of the vacuum freeze dryer to -40 °C and the sublimation drying vacuum degree to 60 Pa, and carry out vacuum freeze-drying treatment for 10 h. Take 10 kg of the vacuum freeze-dried food waste and mix it with 20 kg of sawdust, and then carry out crushing and stirring treatment. After crushing, the particle size is ≤ 10 mm. Then carry out a field test on the soil carbon sequestration ability. The test field area is 9 square meters (3×3), and the soil is the soil at a depth of 0 - 20 cm in the tillage layer. Apply the obtained food waste organic carbon material to the soil at a application rate of 0.5 tons per mu, and deep plow 1 time during the test period.

[0043] Example 5

[0044] Collect food waste, sort out and remove non-degradable impurity components such as metals, glass, plastics, ceramics, etc. Take 15 kg of sorted and impurity-removed food waste and mix it with 105 L of hot water at 65 °C for 2 washes, then drain for 25 min to remove the grease on the surface of the food waste. Put the pretreated food waste into a freezer and pre-freeze it at -4 °C for 7.5 h. Then control the cold trap temperature of the vacuum freeze dryer at -50 °C and the sublimation drying vacuum degree at 70 Pa, and carry out vacuum freeze drying treatment for 19 h. Take 10 kg of the vacuum freeze-dried food waste and mix it with 90 kg of rice straw, and then carry out stirring and crushing treatment. After crushing, the particle size is ≤10 mm. Then carry out a field test on the soil carbon sequestration ability. The test field area is 9 square meters (3×3), and the soil is the soil at a depth of 0-20 cm in the plough layer. Apply the obtained food waste organic carbon material to the soil at a application rate of 2.5 tons per mu, and deep plough 2 times during the test period.

[0045] Example 6

[0046] Collect food waste, sort out and remove non-degradable impurity components such as metals, glass, plastics, ceramics, etc. Take 10 kg of sorted and impurity-removed food waste and mix it with 50 L of hot water at 70 °C for 3 washes, then drain for 30 min to remove the grease on the surface of the food waste. Put the pretreated food waste into a freezer and pre-freeze it at -12 °C for 8.5 h. Then control the cold trap temperature of the vacuum freeze dryer at -60 °C and the sublimation drying vacuum degree at 90 Pa, and carry out vacuum freeze drying treatment for 20 h. Take 10 kg of the vacuum freeze-dried food waste and mix it with 100 kg of crushed rice husks, and then carry out stirring and crushing treatment. After crushing, the particle size is ≤10 mm. Then carry out a field test on the soil carbon sequestration ability. The test field area is 9 square meters (3×3), and the soil is the soil at a depth of 0-20 cm in the plough layer. Apply the obtained food waste organic carbon material to the soil at a application rate of 3 tons per mu, and deep plough 1 time during the test period.

[0047] Performance test:

[0048] Use an energy dispersive spectrometer (EDS) to analyze the food waste organic carbon material prepared in Example 1. The results are shown in Table 1. It can be seen from Table 1 that the carbon element reaches 74.41%, and the carbon content is high, which is helpful for soil carbon sequestration.

[0049] Table 1 Main element contents (%) of Example 4

[0050]

[0051] Use a Fourier transform infrared spectrometer (FTIR) to analyze the structural composition of the food waste organic carbon material prepared in Example 1. The results are as Figure 1 shown. From Figure 1It can be seen that the prepared organic carbon material from food waste has a rich functional group structure, which is beneficial for microbial utilization and increases the soil carbon sequestration effect.

[0052] Northwestern farmland loess was selected as the test soil for the field test on soil carbon sequestration ability. The test field area was 9 square meters (3×3). The soil was from the 0 - 20 cm depth of the tillage layer. The application period was from September 2021 to March 2022. During this period, deep plowing was carried out 1 - 3 times. For 1 - time deep plowing, it was carried out 3 months after application. For 2 - time deep plowing, it was carried out in the 2nd and 4th months after application. For 3 - time deep plowing, it was carried out in the 1st, 3rd, and 5th months after application. After the application period expired, soil organic matter was sampled and analyzed, and a control test was also analyzed at the same time. The results are shown in Table 2.

[0053] Table 2 Increase in soil organic carbon

[0054]

[0055] Note: When analyzing the total organic carbon (TOC), the soil - water ratio (m / v) was 1:20.

[0056] From the test results in Table 2, it can be seen that the addition of the organic carbon material from food waste increased the concentration of active organic carbon in the soil and improved the soil carbon sequestration ability. It can be seen that the method provided by the present invention is an effective way for soil carbon sequestration.

[0057] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for fixing and storing organic carbon in kitchen waste in soil, characterized in that, It includes the following steps: Pretreat the kitchen waste, mix the pretreated kitchen waste with water for cleaning, and drain it; Pre-freeze the cleaned kitchen waste and perform vacuum freeze-drying treatment to obtain a porous structure material; Mix the obtained porous structure material with a biomass material, crush and stir evenly to obtain a kitchen waste organic carbon material; Apply the obtained kitchen waste organic carbon material to the soil and turn the soil regularly; The mass ratio of the porous structure material to the biomass material is 1:(2 - 10); The application rate of the kitchen waste organic carbon material is 0.5 - 3 tons per mu, and the number of times of turning the soil during this period is 1 - 3 times.

2. The method for fixing and storing organic carbon in kitchen waste in soil according to claim 1, characterized in that, The pretreatment of the kitchen waste includes sorting out and removing non-degradable impurities, and the impurity components are one or more of metals, glass, plastics, and ceramics.

3. A method for fixing and sequestering organic carbon from kitchen waste in soil according to claim 1, characterized in that, The temperature of the water is 50 - 70 °C, and the mass-volume ratio of the pretreated kitchen waste to the hot water is 1:(3 - 7).

4. A method for fixing and sequestering organic carbon in kitchen waste in soil according to claim 1, characterized in that, The number of times of mixing and cleaning is 1 - 3 times, and the draining time is 10 - 30 min.

5. A method for fixing and storing organic carbon in kitchen waste in soil according to claim 1, characterized in that, The pre-freezing temperature is -18 - -4 °C, the pre-freezing time is 7 - 10 h. During the vacuum freeze-drying treatment, the cold trap temperature is -80 - -40 °C, the sublimation drying vacuum degree is 40 - 100 Pa, and the drying time is 10 - 20 h.

6. A method for fixing and sequestering organic carbon in kitchen waste in soil according to claim 1, characterized in that, The biomass material is one or more of sawdust, straw, corn cobs, or rice husks.

7. A method for fixing and storing organic carbon from kitchen waste in soil according to claim 1, characterized in that, The particle size of the kitchen waste organic carbon material is 10 mm and below.

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