A biological bacterial fertilizer and its application in improving acid soil containing microplastics

Abstract

This invention discloses a bio-fertilizer and its application in improving acidic soil containing microplastics. The bio-fertilizer comprises a microbial inoculant; the microbial inoculant includes *Bacillus amyloliquefaciens* and *Bacillus licheniformis*; wherein the preservation number of *Bacillus amyloliquefaciens* is CGMCC NO.27765, and the preservation number of *Bacillus licheniformis* is CGMCC NO.24736. This invention prepares the microbial inoculant by screening strains from specific sources, and then combines this microbial inoculant with other nutrients to prepare a bio-fertilizer. Applying the bio-fertilizer of this invention can not only significantly improve crop yield and quality and reduce the inhibitory effect of microplastics on crops, but also effectively improve the quality of acidic soil and increase soil pH.

Description

Technical Field

[0001] This invention relates to the field of agricultural ecological technology, and more specifically, to a bio-fertilizer and its application in improving acidic soil containing microplastics. Background Technology

[0002] With the development of modern agriculture, soil pollution has become increasingly serious. Microplastics, a new type of pollutant, refer to plastic particles with a diameter of less than 5 millimeters. They can enter the soil through mulching, air deposition, sewage, and industrial wastewater, posing a potential threat to the soil environment and crop growth. Simultaneously, with the development of modern agriculture, the area of ​​acidic soils is also gradually expanding. Acidic soils are a general term for soils with low pH values. Acidic soil areas have abundant rainfall, strong leaching, and a large loss of basic ions, resulting in low basic saturation. Furthermore, acidic soils have high concentrations of H+. + A1 3+ Mn 2+ and Fe 2+ These substances have a direct toxic effect on plants. This not only affects crop growth but also leads to soil structure damage, increased activity of heavy metal ions, and deterioration of the ecological environment.

[0003] Therefore, finding an effective method to remediate acidic soil containing microplastics is of great significance for environmental protection and sustainable agricultural development.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a bio-fertilizer and its application in improving acidic soil containing microplastics. This bio-fertilizer has multiple benefits, including improving the quality of acidic soil, reducing the negative impact of microplastics on the soil ecosystem, and promoting crop growth.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a bio-fertilizer, which includes a microbial agent; the microbial agent includes Bacillus amyloliquefaciens and Bacillus licheniformis.

[0008] The accession number for Bacillus amyloliquefaciens is CGMCC NO.27765, and the accession number for Bacillus licheniformis is CGMCC NO.24736.

[0009] Secondly, the present invention provides the application of the above-mentioned bio-fertilizer in improving acidic soil containing microplastics.

[0010] Thirdly, the present invention provides a method for improving acidic soil containing microplastics, which includes adding the above-mentioned bio-fertilizer to the soil containing microplastics.

[0011] The present invention has the following beneficial effects:

[0012] This invention involves screening strains from specific sources to prepare microbial inoculants, which are then combined with other nutrients to create a bio-fertilizer. Applying this bio-fertilizer can significantly improve crop yield and quality, reduce the inhibitory effects of microplastics on crops, and effectively improve the quality of acidic soils, increasing soil pH. Detailed Implementation

[0013] 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0014] According to a first aspect of the present invention, a bio-fertilizer is provided, the raw materials of which include microbial agents, humic acid powder, nitrogen fertilizer, calcium magnesium phosphate fertilizer, potassium fertilizer, black gluten powder, lignin and dry filler powder.

[0015] Specifically, by weight, the raw materials of bio-fertilizer include: 20-30 parts of humic acid raw powder; 1-10 parts of microbial agent; 1-15 parts of nitrogen fertilizer; 1-10 parts of calcium magnesium phosphate fertilizer; 1-15 parts of potassium fertilizer; 5-10 parts of lignin; 1-10 parts of black gluten powder; and 20-30 parts of dry filler powder.

[0016] In this invention, the total viable count of the microbial agent is 1×10⁻⁶. 9 ~1×10 11 cfu / g.

[0017] The microbial agents contain strains including Bacillus amyloliquefaciens with accession number CGMCC NO.27765 and Bacillus licheniformis with accession number CGMCC NO.24736.

[0018] Bacillus amyloliquefaciens, belonging to the genus Bacillus, is a bacterium highly related to Bacillus subtilis. It is a facultative anaerobe, and its colonies on LB agar and beef extract peptone medium appear as pale yellow, opaque colonies with a rough, raised surface and irregular edges. During its growth, it produces a series of metabolites that inhibit the activity of fungi and bacteria.

[0019] The preservation information of Bacillus amyloliquefaciens of the present invention is as follows:

[0020] Bacillus amyloliquefaciens, classified as Bacillus amyloliquefaciens, is deposited at the Guangdong Provincial Center for Microbial Culture Collection, located at 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, on July 3, 2023, with accession number GDMCC NO.27765.

[0021] Bacillus licheniformis is a common Gram-positive thermophilic bacterium found in soil. Its cells are rod-shaped and solitary. It can adjust dysbiosis to achieve therapeutic effects, and can stimulate the body to produce antibacterial substances to kill pathogens. It can produce anti-active substances and has a unique biological oxygen-scavenging mechanism that inhibits the growth and reproduction of pathogens.

[0022] The Bacillus licheniformis strain used in this invention, with accession number CGMCC NO.24736, is an existing strain that has been disclosed in patent documents such as CN202210757961.1 and CN202210757986.1.

[0023] This invention combines the above-mentioned Bacillus amyloliquefaciens and Bacillus licheniformis, and through experiments, the optimal addition ratio was determined: the ratio of live Bacillus amyloliquefaciens to Bacillus licheniformis is 0.5-3:0.5-3, and more preferably, the ratio of the two bacteria is 1:2. Under this ratio, the biological bacteria prepared by the microbial agent can better improve acidic soil containing microplastics.

[0024] In order to provide sufficient nutrients for crops, the bio-fertilizer of the present invention also includes humic acid raw powder, nitrogen fertilizer, calcium magnesium phosphate fertilizer, potassium fertilizer, black gluten powder, lignin and dry filler powder.

[0025] As for the type of nitrogen fertilizer, it can be ammonium nitrogen fertilizer, nitrate nitrogen fertilizer, urea nitrogen fertilizer, or other types of nitrogen fertilizer; the potassium fertilizer can be potassium nitrate, potassium dihydrogen phosphate, potassium sulfate, potassium chloride, or other types of potassium fertilizer. The specific choice of nitrogen and potassium fertilizer can be made according to actual needs, and this invention does not limit this.

[0026] By preparing the above-mentioned specific microbial strains into microbial inoculants, and then compounding them with humic acid raw powder, nitrogen fertilizer, calcium magnesium phosphate fertilizer, potassium fertilizer, black gluten powder, lignin and filler dry powder, bio-fertilizers can be obtained, which can improve the soil environment, promote plant growth, and thus improve the photosynthetic efficiency of plants.

[0027] The preparation method of the bio-fertilizer composed of the above ingredients is as follows:

[0028] (1) Preparation of microbial inoculants:

[0029] The selected Bacillus amyloliquefaciens and Bacillus licheniformis were cultured aerobically, activated, and fermented. Then, they were coupled with the encapsulation material and prepared into composite microcapsules by spray drying for later use.

[0030] The aerobic culture conditions are as follows: culture at 25-35℃ and pH 6.5-7.5 for 24-96 hours; the embedding material is prepared from sodium alginate and calcium chloride. The reason for using sodium alginate and calcium chloride is that sodium alginate can quickly undergo ion exchange with calcium ions to form a gel.

[0031] (2) Humic acid powder, nitrogen fertilizer, calcium magnesium phosphate fertilizer, potassium fertilizer, black gluten powder, lignin and filler dry powder are crushed, mixed and granulated and dried to make organic fertilizer. Then microbial agents are added in proportion and mixed to obtain bio-fertilizer.

[0032] Organic fertilizer is fertilizer containing 30-60% OM, 0-5% N, 0-5% P2O5 and 0-5% K2O.

[0033] According to a second aspect of the present invention, the application of the above-mentioned bio-fertilizer in improving acidic soil containing microplastics is provided.

[0034] Currently, domestic and international research focuses on current status surveys of microplastic pollution or exploring the impact of acidic soils on the ecological environment, while studies on the combined pollution of microplastics and acidic soils are relatively limited. However, the inventors of this invention discovered during their research that bio-fertilizers prepared using microbial agents containing Bacillus amyloliquefaciens and Bacillus licheniformis can improve acidic soils containing microplastics. On the one hand, this improves the quality of acidic soils, and on the other hand, it reduces the negative impact of microplastics on the soil ecosystem, thus jointly promoting crop growth.

[0035] According to a third aspect of the present invention, a method for improving acidic soil containing microplastics is provided, comprising adding a bio-fertilizer to the soil containing microplastics; the bio-fertilizer being the aforementioned bio-fertilizer; wherein the amount of bio-fertilizer used is 150-300 kg / mu; and the dry weight ratio of microplastics to soil is ≤2% w / w.

[0036] When applying the bio-fertilizer of the present invention to soil containing microplastics, the application methods of the bio-fertilizer include hole application, pond application, strip application, and broadcast application.

[0037] The microplastics are selected from at least one of polybutylene terephthalate (PBAT), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene succinate (PBSA), carbon dioxide copolymer (PPC), polylactic acid (PLA), polyhydroxyalkanoate (PHA), and starch plastics.

[0038] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0039] The Bacillus amyloliquefaciens used in this embodiment of the invention has the accession number CGMCC NO.27765; the Bacillus licheniformis has the accession number CGMCC NO.24736.

[0040] Example 1

[0041] This embodiment provides a bio-fertilizer, the raw material composition of which is as follows:

[0042] 28 parts of humic acid raw powder; 4 parts of microbial inoculant; 10 parts of nitrogen fertilizer; 10 parts of phosphate fertilizer; 5 parts of potassium fertilizer; 8 parts of black viscous powder; 8 parts of lignin; 27 parts of dry filler powder.

[0043] The number of live bacteria in the bio-fertilizer is 8×10⁻⁶. 8 cfu / g. Among them, the viable count ratio of Bacillus amyloliquefaciens to Bacillus licheniformis was 1:2.

[0044] The above-mentioned bio-fertilizer is prepared by the following method:

[0045] S1. Selected Bacillus amyloliquefaciens and Bacillus licheniformis were cultured aerobically at 26℃ and pH=6.5 for 72h to activate and expand the culture. Then, they were ion-gel coupled with sodium alginate and calcium chloride and spray-dried to prepare composite bacterial agent microcapsules for later use.

[0046] S2. Humic acid raw powder, nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, black gluten powder, lignin and filler dry powder are crushed and mixed in proportion, granulated and dried to make organic fertilizer. Then, microbial inoculants are added in proportion, mixed and stirred evenly, granulated in a drum, and dried at low temperature to obtain bio-fertilizer.

[0047] Example 2

[0048] This embodiment provides a bio-fertilizer, the specific preparation method of which is the same as that in Embodiment 1, the difference being the different raw material composition of the bio-fertilizer, which is as follows:

[0049] 30 parts humic acid raw powder; 5 parts microbial inoculant; 5 parts nitrogen fertilizer; 10 parts phosphate fertilizer; 5 parts potassium fertilizer; 10 parts black viscous powder; 10 parts lignin; 25 parts dry filler powder.

[0050] Example 3

[0051] This embodiment provides a bio-fertilizer, the specific preparation method of which is the same as that in Embodiment 1, the difference being the different raw material composition of the bio-fertilizer, which is as follows:

[0052] 25 parts humic acid raw powder; 6 parts microbial inoculant; 12 parts nitrogen fertilizer; 8 parts phosphate fertilizer; 5 parts potassium fertilizer; 8 parts black viscous powder; 8 parts lignin; 28 parts dry filler powder.

[0053] Example 4

[0054] This embodiment provides a bio-fertilizer. The specific preparation method is the same as in Example 1. The difference is that the ratio of viable Bacillus amyloliquefaciens to Bacillus licheniformis in the microbial agent is different. In this embodiment, the ratio is 1:3.5.

[0055] Example 5

[0056] This embodiment provides a bio-fertilizer. The specific preparation method is the same as in Example 1. The difference is that the ratio of viable Bacillus amyloliquefaciens to Bacillus licheniformis in the microbial agent is different. In this embodiment, the ratio is 1:1.

[0057] Comparative Example 1

[0058] The difference from Example 1 is that it does not contain microbial inoculants.

[0059] Comparative Example 2

[0060] The difference from Example 1 is that the ratio of viable bacteria of Bacillus amyloliquefaciens to Bacillus licheniformis strain in the microbial agent exceeds the protection range, with a viable bacteria ratio of 8:1.

[0061] Comparative Example 3

[0062] The difference from Example 1 is that the raw material composition of the bio-fertilizer exceeds the scope of protection. The raw material composition of the bio-fertilizer is as follows: 20 parts of humic acid raw powder; 2 parts of microbial agent; 8 parts of nitrogen fertilizer; 10 parts of phosphate fertilizer; 7 parts of potassium fertilizer; 15 parts of black viscous powder; 5 parts of lignin; and 35 parts of dry filler powder.

[0063] Experimental Example 1

[0064] The bio-fertilizers obtained in Examples 1-5 and Comparative Examples 1-3 were subjected to fertilizer efficiency tests, as detailed below:

[0065] The bio-fertilizers from Examples 1-5 and Comparative Examples 1-3 were added to the soil at a rate of 0.5% w / w and mixed thoroughly. The experimental crop was Shanghai bok choy. The experiment was conducted using pot cultivation, with each pot measuring 230mm × 180mm and containing 6kg of soil. Six pots were used as replicates per group. Shanghai bok choy seeds were disinfected twice with 75% ethanol for 2 minutes each time, followed by washing in sterile distilled water for 2 minutes. After germination, three seedlings at the four-leaf-one-heart stage with uniform growth and strong root systems were selected and transplanted. Fertilization was carried out according to the fertilization plan. Basic indicators such as chlorophyll content, plant height, and total dry weight were measured between groups after 28 days. Specific results are shown in Table 1 below. Table 1 also includes a blank control group, which represents the performance of Shanghai bok choy without fertilizer application.

[0066] Table 1 Comparison of chlorophyll content, plant height, total dry weight, and yield increase rate of Shanghai bok choy under different treatments.

[0067] deal with Chlorophyll (SPAD value) Plant height / cm Whole plant dry weight / g Production increase rate % blank 32.7 12.7 1.8 0 Example 1 38.9 17.6 5.8 163.64 Example 2 37.2 16.8 5.1 131.82 Example 3 38.1 17.0 5.3 140.91 Example 4 37.9 16.9 5.2 136.36 Example 5 38.3 17.1 5.5 150.00 Comparative Example 1 34.8 16.3 4.7 113.64 Comparative Example 2 35.5 16.5 4.8 118.18 Comparative Example 3 35.1 16.3 4.6 109.09

[0068] As shown in Table 1, compared with the control group, the examples and comparative examples of fertilizer application all improved the chlorophyll content, plant height, whole plant fresh weight, and yield of Chinese cabbage. Chlorophyll content is closely related to the nitrogen content in leaves, and detecting chlorophyll content can reflect the crop's nitrogen fertilizer requirements, thus proving the fertilizer's effectiveness. Comparison showed that the bio-fertilizers prepared in Examples 1-5 were significantly higher than those in Comparative Examples 1-3 in terms of chlorophyll content, plant height, whole plant fresh weight, and yield. Therefore, it can be proven that the composition and ratio of the bio-fertilizer provided by this invention have better fertilizer efficiency, with Example 1 being the optimal formulation.

[0069] Experiment Example 2

[0070] This experimental example verifies the function of the bio-fertilizer obtained in Example 1 in the improved acidic soil of Xishan Vegetable Garden in Guiping, Guigang, Guangxi. The details are as follows:

[0071] The soil pH in this vegetable garden ranged from 4.1 to 5.3. Due to long-term application of chemical fertilizers and lime, the soil became compacted. The bio-fertilizer obtained in Example 1 was applied as a base fertilizer at a rate of 200 kg / mu for three consecutive years. The soil conditions before and after the application of Example 1 were compared, as shown in Table 2.

[0072] Table 2 Changes in soil physical fertility before and after application of Example 1

[0073]

[0074] The results in Table 2 show that as the application time increases, the pH value of acidic soils treated with the bio-fertilizer of Example 1 gradually increases, the soil bulk density gradually decreases, and the total porosity, capillary porosity, non-capillary porosity, and field water holding capacity all show a continuous increasing trend. The above data prove that acidic soils treated with the bio-fertilizer of Example 1 can be improved.

[0075] Experimental Example 3

[0076] The functional verification of the bio-fertilizer obtained in Example 1 in improving acidic soil containing microplastics is as follows:

[0077] 1. Soil Treatment: The test soil was red soil taken from farmland in Guangming District. This sampling area had never used plastic film mulch. The soil pH was 5.98, and the contents of organic matter (OM), total nitrogen (TN), total phosphorus (TP), and potassium (TK) were 16.84, 0.84, 0.64, and 14.84 g / kg, respectively. The available nitrogen, available phosphorus (AP), and available potassium (AK) were 48.85, 178.20, and 116.01 g / kg, respectively.

[0078] 2. The experimental treatments were divided into six groups: (1) untreated control (no bio-fertilizer and microplastics added); (2) only microbial fertilizer applied; (3) microbial fertilizer and 0.2% PE MPs (0.2% w / w, dry weight ratio between MPs and soil); (4) microbial fertilizer and 2.0% PE MPs (2.0% w / w); (5) microbial fertilizer and 0.2% Bio-MPs; (6) microbial fertilizer and 2.0% Bio-MPs. In this experimental case, the amount of microbial fertilizer applied in each group was 200 kg / mu.

[0079] 3. Test crop: Chinese cabbage, a common economic crop with a growth period of about 20-30 days; Chinese cabbage seeds were disinfected twice with 75% ethanol for 2 minutes each time, and then washed in sterile distilled water for 2 minutes. After germination, 3 seedlings with uniform growth and strong root system at the four-leaf-one-heart stage were selected for transplanting.

[0080] 4. Microplastic source: Polyethylene (PE-MPs) and biodegradable plastics (Bio-MPs) were purchased from Dongguan Huachuang Chemical Trading Co., Ltd.

[0081] 5. Microplastic composition: Biodegradable plastics (Bio-MPs) are composed of polybutylene terephthalate (PBAT) and polylactic acid (PLA).

[0082] 6. Cultivation period: The cultivation period is 28 days. During this period, the soil moisture content is maintained at 60% to 80% of the field capacity of the soil using the weighing method.

[0083] 7. Data Testing: After 28 days, six Chinese flowering cabbage plants were randomly selected from each treatment, and their height and root length were measured using a measuring tape. The leaves, stems, and roots of the plants were washed, dried on paper towels, and the fresh weight of the above-ground and underground parts was recorded separately.

[0084] Upon removal of the plant, loose soil adhering to the root surface was shaken off, leaving approximately 1 mm of soil on the root surface as rhizosphere soil. The plant root zone sample was placed in a 50 mL test tube containing 30 mL of sterile phosphate-buffered saline (PBS) solution and vigorously stirred to remove all rhizosphere soil from the root surface. The rhizosphere soil was concentrated by centrifugation at 10,000 g for 30 seconds. Subsequently, the plant root zone sample, free of rhizosphere soil, was washed twice more with sterile PBS solution to remove any visible adhering soil. The pH of the rhizosphere soil was measured for potential at a soil-to-liquid ratio of 1:2.5 (w / v).

[0085] Soil SOC and OM were determined using the potassium dichromate oxidation-external heating method.

[0086] Data are expressed as mean ± standard deviation (n = 6). Different lowercase letters indicate statistically significant differences between treatments (p < 0.05), based on one-way ANOVA and Duncan's test.

[0087] 8. Analysis of Experimental Results

[0088] Table 3. Experimental Results

[0089]

[0090] The results in Table 3 show that the bio-fertilizer of this invention reshaped the rhizosphere soil environment of Chinese cabbage, including changes in pH (8.56%), SOC (22.12%), and OM (37.44%) relative to the control (p<0.05). The addition of microplastics (MPs) further significantly affected pH, altering the acidity / alkalinity of the rhizosphere soil (from 7.92 to 8.11). Simultaneously, the effects of MPs on other rhizosphere soil indicators in the presence of the bio-fertilizer varied depending on the type of MPs. For example, the addition of Bio-MPs increased the SOC and OM contents by 0.97-1.77 times and 0.91-1.58 times, respectively. These data demonstrate that the application of the bio-fertilizer of this invention to acidic soils contaminated with microplastics can synergistically improve soil pH and fertility in conjunction with microplastics.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of a bio-fertilizer in improving acidic soil containing microplastics, characterized in that, The bio-fertilizer includes microbial agents; the microbial agents include Bacillus amyloliquefaciens and Bacillus licheniformis; The Bacillus amyloliquefaciens has the accession number CGMCC NO.27765, and the Bacillus licheniformis has the accession number CGMCC NO.24736.

2. The application according to claim 1, characterized in that, The viable bacteria count in the microbial agent is 1×10⁻⁶. 9 1×10 11 cfu / g.

3. The application according to claim 2, characterized in that, The live bacteria ratio of Bacillus amyloliquefaciens and Bacillus licheniformis in the microbial agent is 0.5-3:0.5-3.

4. The application according to claim 3, characterized in that, The ratio of live Bacillus amyloliquefaciens to Bacillus licheniformis in the microbial agent is 1:

2.

5. The application according to claim 4, characterized in that, The bio-fertilizer also includes humic acid raw powder, nitrogen fertilizer, calcium magnesium phosphate fertilizer, potassium fertilizer, black gluten powder, lignin, and dry filler powder; The raw materials of the bio-fertilizer, by weight, include: 20-30 parts of humic acid raw powder; 1-10 parts of microbial agent; 1-15 parts of nitrogen fertilizer; and 1-10 parts of calcium magnesium phosphate fertilizer. Potassium fertilizer 1-15 parts; black gluten powder 1-10 parts; lignin 5-10 parts; filler powder 10-20 parts.

6. The application according to claim 5, characterized in that, The preparation method of the bio-fertilizer includes the following steps: crushing, mixing and granulating the humic acid raw powder, nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, black glutinous powder, lignin and filler dry powder in proportion, drying and making organic fertilizer, then adding the microbial agent in proportion, mixing and obtaining the bio-fertilizer.

7. The application according to claim 6, characterized in that, The organic fertilizer contains 30 60% OM, 0 5% N,0 5% P2O5 and 0 Fertilizer with 5% K2O.

8. The application according to claim 6, characterized in that, The preparation method of the microbial agent includes aerobic culture of Bacillus amyloliquefaciens and Bacillus licheniformis at 25-35℃ and pH=6.5-7.5 for 24-96h. After activation and expansion, they are coupled with an embedding material prepared by sodium alginate and calcium chloride. After coupling, they are spray-dried to prepare composite microcapsules, which are the microbial agents.

9. A method for improving acidic soil containing microplastics, characterized in that, This includes adding bio-fertilizer to soil containing microplastics, wherein the bio-fertilizer is the bio-fertilizer described in any one of claims 1-8.

10. The method according to claim 9, characterized in that, The dry weight percentage of microplastics in the soil is ≤2%w / w.

11. The method according to claim 10, characterized in that, The amount of bio-fertilizer used is 150~300 kg / mu.

12. The method according to claim 11, characterized in that, The application methods of the bio-fertilizer include hole application, pond application, strip application, and broadcast application.

13. The method according to claim 12, characterized in that, The microplastics include biodegradable microplastics.

14. The method according to claim 13, characterized in that, The biodegradable microplastics are made of at least one of the following materials: polybutylene terephthalate (PBAT), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene succinate (PBSA), carbon dioxide copolymer (PPC), polylactic acid (PLA), polyhydroxyalkanoate (PHA), and starch plastics.

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