Method and product for recycling kitchen waste anaerobic fermentation biogas residues and degradable plastic wastes

Abstract

The invention relates to a method for recycling kitchen waste anaerobic fermentation biogas residues and degradable plastic wastes and a product thereof, and the method specifically comprises the following steps: (1) mixing kitchen biogas residues and agricultural and forestry wastes according to a ratio of (1-10): (1-10) to obtain an initial compost substrate, and controlling the water content of the initial compost substrate to be 50-70% and the C / N ratio to be (20-30): 1; and (2) adding the degradable plastic waste fragments into the initial composting substrate at one time, uniformly mixing, starting an aerobic composting device, and performing a complete composting period on the compost body to obtain the fertilizer. According to the prepared fertilizer, the seed germination rate is remarkably increased, and humus substances and humic acid substances are remarkably increased. Meanwhile, according to the international standard (EN13432-2002), good disintegration of the degradable plastic is achieved through the co-processing technology. The fertilizer meets the use requirements of organic manure, and the purpose of recycling kitchen waste anaerobic fermentation biogas residues and degradable plastic waste is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic solid waste treatment, and specifically relates to a method and product for anaerobic fermentation of kitchen waste and coordinated resource utilization of biodegradable plastic waste. Background Art

[0002] With the rapid development of the economy and the catering industry, a large number of food waste treatment plants have gradually emerged in my country. It is a comprehensive facility dedicated to converting food waste into resources. At present, anaerobic digestate from food waste (hereinafter collectively referred to as food digestate) is generally transported to incineration plants or landfills, which further increases the operating costs of food waste treatment plants that originally have limited profitability. There are relatively many technologies for composting food waste, such as "A method for aerobic composting of food waste" with patent publication number CN115010520A and "A mixed bacteria-based composite enzyme for fermentation of food waste, preparation and rapid composting method" with patent publication number CN116376878A. However, there are relatively few technologies for composting food digestate, which may be related to problems such as high moisture content, low C / N and poor physical structure of food digestate. Patent publication number CN110668852A, "Method for preparing organic fertilizer by anaerobic fermentation of food waste biogas residue", uses mature biogas residue-based fertilizer and new biogas residue for mixed composting, effectively improving the efficiency and fertilizer quality of the single food waste composting process. In general, effective food waste co-disposal solutions are relatively lacking.

[0003] With the vigorous promotion of degradable plastics, degradable plastics will completely replace traditional petroleum-based plastics in the future, and then a large amount of degradable plastic waste will be generated. Under ideal conditions, degradable plastic waste can be transformed by microorganisms, or even completely mineralized, to achieve zero pollution. However, many reports currently point out that a large amount of degradable plastic waste fragments remain in the environment, which may pose environmental risk problems similar to petroleum-based plastics (Liu Jiaqian, Hou Lijun, Liu Tingting, et al. Screening of PBAT mulch-degrading bacteria and study of their degradation characteristics. Journal of Agricultural Environmental Science, 2021, 40(01): 129-136.). In order to avoid the accumulation of degradable plastic waste in the environment, the development of technical solutions for "waste treatment" and "waste resource utilization" of degradable plastic waste is more in line with the strategic goal of green and sustainable development.

[0004] Plastic products are particularly widely used in the catering industry and have become indispensable supplies. They are widely used in food packaging, take-out packaging, plastic sealing and preservation. A large amount of plastic flows to the food waste treatment plant along with the food waste. Although garbage sorting can effectively screen plastics and food waste, it is also accompanied by a lot of workload. The relatively high carbon content and fluffy characteristics of degradable plastics are used to replace conditioners. It is highly feasible to develop a co-composting technology of food waste sludge and degradable plastic waste. On the one hand, degradable plastic waste can supplement the carbon source of food waste and reduce the external carbon source; on the other hand, co-processing can reduce the workload of screening. In addition, this will also directly reduce the serious secondary risks caused by the environmental retention of degradable plastic waste. Summary of the invention

[0005] The purpose of the present invention is to provide a method and product for the anaerobic fermentation of kitchen waste and biogas residue to coordinate the resource utilization of degradable plastic waste. By adding degradable plastic waste, the transformation and decomposition of organic matter in the compost sample are promoted, the compost humification process is promoted, the fertilizer efficiency and application potential of the fertilizer are increased, and at the same time, the smooth progress of the composting process is ensured, and the quality of the fertilizer is significantly improved.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for anaerobic fermentation of kitchen waste and biodegradable plastic waste for resource utilization, specifically comprising the following steps:

[0008] (1) mixing food waste and agricultural and forestry waste in a ratio of (1-10):(1-10) to obtain an initial compost matrix, controlling the moisture content of the initial compost matrix to be 50%-70% and the C / N ratio to be (20-30):1;

[0009] (2) Add degradable plastic waste fragments to the initial composting matrix at one time, mix and stir, and then start the aerobic composting device. The composting pile undergoes a complete composting cycle to obtain fertilizer.

[0010] In a preferred embodiment, in step (1), the food digestate and agricultural and forestry waste are mixed in a ratio of (3-5): (1-2) to obtain an initial compost matrix;

[0011] In a preferred embodiment, in step (1), the food waste biogas residue is solid biogas residue obtained by anaerobic fermentation and two-phase separation of food waste;

[0012] In a preferred embodiment, in step (1), the agricultural and forestry waste is a combination of one or more of wood shavings, sawdust, peanut shells, rice husks, straw and garden waste;

[0013] In a preferred embodiment, in step (1), the moisture content of the initial composting matrix is ​​65%-70%;

[0014] In a preferred embodiment, in step (2), the amount of the degradable plastic waste fragments added is 1%-10% of the dry weight of the initial composting substrate;

[0015] In a preferred embodiment, in step (2), the degradable plastic waste fragments are obtained by mechanical crushing and have a size of 5 mm×5 mm-10 mm×10 mm;

[0016] In the preferred embodiment, in step (2), the pile undergoes a complete composting cycle, which means that the compost undergoes a heating period, a high temperature period, a cooling period and a maturity period. Generally, the heating period: the initial mixed material temperature is 50°C; the high temperature period: the pile temperature is 50°C or above; the cooling period: the pile temperature of 50°C or above drops to room temperature; then, the compost enters the maturity period. Among them, the high temperature period needs to be above 55°C for 3 days or above 50°C for 5-7 days, and the maturity period needs to be continued for 7 days or more after the temperature drops to room temperature;

[0017] In the preferred scheme, aerobic composting is carried out under aeration conditions, and the aeration rate is 0.1-0.4L·min -1 , preferably 0.35-0.4L·min -1 ;

[0018] In the preferred solution, during the composting cycle, the frequency of turning the pile is once every 4-5 days;

[0019] Another object of the present invention is to provide a fertilizer prepared by co-composting food waste biogas residue and degradable plastic waste, wherein the fertilizer is prepared by a method of anaerobic fermentation of food waste biogas residue and coordinated resource utilization of degradable plastic waste.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention provides a method and product for the coordinated resource utilization of food digestate and degradable plastic waste. The addition of degradable plastic waste promotes the transformation and decomposition of organic matter in compost samples, promotes the compost humification process, increases the fertilizer efficiency and application potential of fertilizers, and at the same time provides a method for effectively reducing degradable plastic waste, reduces the potential farmland ecological risks caused by plastic residues, and provides ideas for the coordinated treatment of agricultural and forestry wastes.

[0022] (2) This scheme is simple, easy to operate, and has a short cycle. It can simultaneously achieve the three effects of retaining nitrogen, promoting decay, and accelerating the degradation of mulch film with one stone. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a comparison chart of the seed germination rates of the fertilizers prepared in Comparative Example 1 and Examples 1-2;

[0024] Figure 2 This is a comparison chart of dissolved organic carbon of the fertilizers prepared in Comparative Example 1 and Examples 1-2;

[0025] Figure 3 This is a comparison chart of humus and humic acid substances in the fertilizers prepared in Comparative Example 1 and Examples 1-2;

[0026] Figure 4 This is a comparison chart of the cumulative ammonia emissions of the fertilizers prepared in Comparative Example 1 and Examples 1-2;

[0027] Figure 5 This is a comparison chart of the ammonium nitrogen content of the fertilizers prepared in Comparative Example 1 and Examples 1-2;

[0028] Figure 6 This is a comparison chart of the organic matter content of the fertilizers prepared in Comparative Example 1 and Examples 1-2;

[0029] Figure 7 This is a comparison chart of the weight loss rate of degradable plastic waste on the 20th day of composting in Example 1-2;

[0030] Figure 8 This is a comparison chart of the apparent loss rate of degradable plastic waste on the 20th day of composting in Example 1-2;

[0031] Fig. 9 This is a comparison chart of the theoretical disintegration rates of degradable plastic waste on the 20th day of composting in Examples 1-2. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] In this study, the food waste residue was taken from the residue after the two-phase separation of wet anaerobic fermentation in a food waste treatment plant in Harbin. Its moisture content, pH, conductivity, total carbon and total nitrogen were 79.61%, 8.62, 2.66ms / cm, 24.56% and 3.64%, respectively. Sawdust was taken from a wood processing plant in Harbin, and its moisture content, total carbon and total nitrogen were 5.53%, 45.74% and 0.44%, respectively. Degradable plastics were purchased from a craft products company in Shantou City. The implementation standards were "Biodegradable Plastic Shopping Bags" (GB / T38082-2019) and "General Technical Requirements for Fully Biodegradable Plastic Products" (DB / T505-2020). The product materials were polybutylene terephthalate adipate (PBAT), starch-based, polylactic acid (PLA), and its moisture content, total carbon and total nitrogen were 0.53%, 43.06% and 2.18%, respectively. The kitchen biogas residue and sawdust are mixed in a ratio of 4:1 to obtain an initial compost matrix with a moisture content of about 66.0% and a carbon-nitrogen ratio of about 21.0. Then, 1% or 10% of the dry weight of the initial compost matrix is ​​mixed with degradable plastic fragments, and the mixture is stirred and then composting is started.

[0034] The present invention adopts the following detection method to measure the substance content in the fertilizer:

[0035] 1. pH value determination: Take a certain mass of fresh compost sample and mix it with ultrapure water in a ratio of 1:10 (mass g: volume ml), shake it at 25℃ and 180r / min for 1h, centrifuge it at 5000rpm for 10min, and use a pH meter to detect the pH value of the supernatant;

[0036] 2. Determination of seed germination rate: According to the requirements of the organic fertilizer (NY / T 525-2021) standard, cucumber seeds (uncoated) were selected for testing;

[0037] 3. Determination of dissolved organic carbon content: Take a certain mass of fresh compost sample and mix it with ultrapure water in a ratio of 1:10 (mass g: volume ml), mix and shake at 25°C and 180r / min for 24h, centrifuge at 5000rpm for 10min, then take the supernatant and centrifuge at 10000rpm for 10min, filter the supernatant through a 0.45μm filter membrane to obtain an extract, dilute the extract 50-200 times, and determine it with a TOC analyzer;

[0038] 4. Three-dimensional fluorescence spectrum (humus and humic acid) analysis: Take a certain mass of fresh compost sample and mix it with ultrapure water at a ratio of 1:10 (mass g: volume ml), shake it at 180 rpm for 24 hours, centrifuge it at 5000 rpm for 20 minutes, filter it through a 0.45 μm filter membrane, and measure it using a three-dimensional fluorescence spectrometer;

[0039] 5. Determination of cumulative ammonia emissions: Use 0.5 mol / L boric acid solution to absorb ammonia. Take a certain amount of boric acid absorption liquid at a specific time every day. After dilution, use 0.01 mol / L sulfuric acid solution for color titration. Calculate the cumulative ammonia emissions based on the consumption of sulfuric acid solution.

[0040] 6. Determination of ammonium nitrogen content: Take a certain mass of fresh compost sample and mix it with 1 mol / L potassium chloride solution in a ratio of 1:10 (mass g: volume ml), shake it at 25°C and 180 r / min for 1 hour, centrifuge it at 5000 rpm for 10 minutes, then take the supernatant and centrifuge it at 10000 rpm for 10 minutes, filter the supernatant through a 0.45 μm filter membrane to obtain an extract, and determine the ammonium nitrogen content by Nessler colorimetry;

[0041] 7. Determination of organic matter content: Weigh a certain mass of fresh compost sample and place it in a tin foil box with a mass of m; dry it in a blast drying oven at 105°C for 24 hours to obtain a dried sample, whose mass is recorded as m1; place the dried sample in a crucible and burn it in a muffle furnace at 600°C for 4 hours to obtain a burned sample, whose mass is recorded as m2; according to the mass difference (m1-m2), the organic matter content = (m1-m2) / (m1-m)×100%;

[0042] 8. Degradation test of degradable plastics (determination of weight loss rate and apparent loss rate): Place several pieces of plastic wrapped in 250μm nylon bags (including but not limited to 10cm×10cm) in the composting reactor to observe the degradation behavior of the plastic during the composting process. In the set degradation cycle, take out the plastic wrapped in nylon bags from the composting reactor, and measure its weight loss rate and apparent loss. Specifically, weight loss rate = (initial mass - mass after degradation) / initial mass × 100%; use ImageJ software to measure the area and length and manually count the number, apparent loss rate = (initial area - area after degradation) / initial area × 100%; disintegration rate = apparent loss rate + apparent residual rate × proportion of disintegrated components (<2mm×2mm);

[0043] The detection methods are all conventional methods in the art, such as the methods disclosed in the literature (Chen ZQ, Wu Y.Q., Wen QX, et al., Insight into the effects of sulfamethoxazole and norfloxacin on nitrogen transformation functional genes during swine manure composting. Bioresource Technology, 2020, 297: 122463; Bao HY, Chen ZQ, Wen QX, et al., Effect of calcium peroxide dosage on organic matter degradation, humification during sewage sludge composting and application as amendment for Cu(II)-polluted soils. Journal of Hazardous Materials, 2022, 439: 129592.).

[0044] Comparative Example 1

[0045] (1) Take 6 kg of initial compost substrate, without adding degradable plastic fragments, mix and stir well, and start the aerobic composting device, which is counted as composting day 0. Aeration is performed continuously during the composting process, and the aeration rate is 0.4 L min -1 , the pile is turned manually every 5 days;

[0046] (2) After the temperature of the pile drops to room temperature for a period of time, the pile has undergone a complete composting cycle, which lasts for 30 days, and the fertilizer is obtained. After testing, the seed germination rate of the fertilizer is 37%, which is lower than the 70% specified in the standard for organic fertilizers (NY / T525-2021); the organic matter content is greater than 30%, and the pH value is between 5.5-8.5, which meets the standard for organic fertilizers (NY / T525-2021).

[0047] Example 1

[0048] (1) Take 6 kg of initial compost matrix, add 1% (DW) of the initial compost matrix of degradable plastic fragments, mix and stir well, and start the aerobic composting device, which is counted as composting day 0. Continuous aeration is performed during the composting process, and the aeration rate is 0.4 L min -1 , the pile is turned manually every 5 days;

[0049] (2) After the temperature of the pile drops to room temperature for a period of time, the pile has undergone a complete composting cycle, which lasts for 30 days, and fertilizer is obtained. After testing, the seed germination rate, organic matter content and pH value all meet the standards of organic fertilizer (NY / T 525-2021).

[0050] Example 2

[0051] (1) Take 6 kg of initial compost matrix, add 10% (DW) of the initial compost matrix of degradable plastic fragments, mix and stir well, and start the aerobic composting device, which is counted as composting day 0. Continuous aeration is performed during the composting process, and the aeration rate is 0.4 L min -1 , the pile is turned manually every 5 days;

[0052] (2) After the temperature of the pile drops to room temperature for a period of time, the pile has undergone a complete composting cycle, which lasts for 30 days, and fertilizer is obtained. After testing, the seed germination rate, organic matter content and pH value all meet the standards of organic fertilizer (NY / T 525-2021).

[0053] The seed germination index rate, dissolved organic carbon, humus (fluorescence area integral), humic acid (fluorescence area integral), cumulative ammonia emission, ammonium nitrogen content and organic matter content of the fertilizers prepared in Comparative Example 1 and Examples 1-2 were compared. The results are shown in Figure 1-Figure 6 .in, Figure 1 The seed germination rate of Comparative Example 1 was much lower than that of Examples 1-2, and did not meet the standard of organic fertilizer (NY / T 525-2021). Figure 2 It reflects the content of dissolved organic matter. It is generally believed that the closer the dissolved organic matter is to 10.0 g·kg -1 DW, the higher the degree of maturity. Figure 3 It represents the fluorescence area integral results of humus (humic acid substances + fulvic acid substances) and humic acid substances. Example 1-2 is greater than Comparative Example 1, and Example 1-2 has a higher humification level; Figure 4 It reflects the cumulative emission of ammonia, which is the main form of nitrogen loss in aerobic composting. Comparative Example 1 is greater than Examples 1-2, and Examples 1-2 have better nitrogen retention performance; Figure 5 The results represent the ammonium nitrogen content. Comparative Example 1 is greater than Examples 1-2. Examples 1-2 have higher nitrification and maturity levels. The contents of Comparative Example 1 and Example 1 are 2.88 and 2.71 g kg, respectively. - 1 DW, the difference is small, it may be that the addition of 1% degradable plastic waste has limited effect on the recovery of nitrification capacity during the composting maturity period; Figure 6 The results represent the organic matter content. Example 1-2 is greater than Comparative Example 1, and Example 1-2 has a higher organic matter content.

[0054] The weight loss rate, apparent loss rate and theoretical disintegration rate of the degradable plastic waste on the 20th day of composting in Example 1-2 were compared. The results are shown in Figure 7-Figure 9 .

[0055] The pH of the fertilizers prepared in Examples 1 and 2 of the present invention is 7.69-8.12;

[0056] The seed germination rates of the fertilizers prepared in Examples 1 and 2 of the present invention are both higher than 80%;

[0057] The dissolved organic carbon content of the fertilizers prepared in Examples 1 and 2 of the present invention is close to 10.0 g·kg -1 DW;

[0058] The humus substances in the fertilizers prepared in Examples 1 and 2 of the present invention are both higher than 0.5 au;

[0059] The humic acid substances in the fertilizers prepared in Examples 1 and 2 of the present invention are both higher than 0.3 au;

[0060] The organic matter content of the fertilizers prepared in Examples 1 and 2 of the present invention is higher than 65.00%;

[0061] The degradable plastic waste fragments can be effectively recovered on the 20th day of composting in Example 1-2, but the degradable plastic waste fragments cannot be effectively recovered on the 30th day. The weight loss rate of the degradable plastic in the degradation experiment on the 20th day of composting was higher than 52.90%, and the apparent loss rates in the degradation experiments of Example 1-2 were 78.08% (<2cm×2cm, >60.00%) and 76.10% (<2cm×2cm, >53.33%) respectively; taking the initial addition of 10mm×10mm degradable plastic waste as an example, the theoretical disintegration rate of Example 1-2 was higher than 76.10%+23.90%×53.33%=88.85% (<2mm×2mm). In short, the co-composting system can basically meet the requirements of good disintegration (<2mm, >90%) on the 20th day. On the 30th day of composting, the weight loss rate, apparent loss rate and theoretical disintegration rate of the degradable plastic waste in the fertilizer all reached 100%.

[0062] The germination rate of the fertilizer seeds prepared by the method of the present invention is significantly improved, and the humus and humic acid substances are significantly increased. At the same time, according to the international standard (EN13432-2002), the coordinated disposal technology achieves good disintegration of degradable plastics (<2mm, >90%). The fertilizer meets the use requirements of organic manure and achieves the goal of anaerobic fermentation of kitchen waste and coordinated resource utilization of degradable plastic waste.

[0063] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for anaerobic fermentation of kitchen waste and biodegradable plastic waste resource recovery, characterized in that: The following steps are involved: Step 1: Mixing food digestate and agricultural and forestry waste in a ratio of (1-10):(1-10) to obtain an initial compost matrix, controlling the moisture content of the initial compost matrix to be 50%-70% and the C / N ratio to be (20-30):1; Step 2: Add degradable plastic waste fragments to the initial composting matrix, mix and stir well, and then aerobically compost them. After the composting pile undergoes a complete composting cycle, fertilizer is obtained.

2. The method according to claim 1, characterized in that: In step 1, the food digestate and agricultural and forestry waste are mixed in a mass ratio of (3-5):(1-2) to obtain an initial composting matrix.

3. The method according to claim 1, characterized in that: In step one, the food digestate is solid digestate obtained after anaerobic fermentation and two-phase separation of food waste; the agricultural and forestry waste is one or more of wood shavings, sawdust, peanut shells, rice husks, straw and garden waste.

4. The method according to claim 1, characterized in that: In step 2, the amount of the degradable plastic waste fragments added is 1%-10% of the dry weight of the initial composting matrix.

5. The method according to claim 1, characterized in that: In step 2, the size of the degradable plastic waste fragments is 5mm×5mm-10mm×10mm.

6. The method according to claim 1, characterized in that: In step 2, the complete composting cycle includes a heating period, a high temperature period, a cooling period and a maturity period.

7. The method according to claim 1, characterized in that: In step 2, the aerobic composting is carried out under aeration conditions, and the aeration rate is 0.1-0.4 L·min -1 .

8. The method according to claim 1, characterized in that: In step 2, during the composting cycle, turn the pile every 4-5 days.

9. A fertilizer prepared by co-composting kitchen waste and degradable plastic waste, characterized in that: The fertilizer is a fertilizer prepared by the method according to any one of claims 1 to 8.

10. The fertilizer according to claim 9, characterized in that: In step 2, the pH of the fertilizer is 7.69-8.12.

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