Thermochemical pretreatment method for anaerobic digestion of biodegradable plastics

Abstract

The present invention relates to a thermochemical pretreatment method for anaerobic digestion of biodegradable plastics. The pretreatment method of the present invention comprises a step of heat treatment following bringing biodegradable plastics into contact with a chemical substance that can cause a molecular weight reduction of the biodegradable plastics or accelerate the molecular weight reduction.

Description

Thermochemical pretreatment method for anaerobic digestion of biodegradable plastics

[0001] The present invention relates to a thermochemical pretreatment method for the anaerobic digestion of biodegradable plastics. More specifically, the present invention relates to a thermochemical pretreatment method that can increase the efficiency of anaerobic digestion of biodegradable plastics, shorten the decomposition time, and thus significantly increase the efficiency of biogas production, such as biomethane.

[0002]

[0003] In the plastics industry, which uses fossil fuels, there is a need to address the problem of carbon emissions and the accumulation of plastic waste due to an industrial structure that does not allow for recycling.

[0004] Accordingly, biodegradable plastics are attracting attention as an alternative to addressing the ecological hazards of existing petroleum-based products and the environmental pollution caused by the increased use of plastics. However, biodegradation is problematic because each type requires different processing conditions, including temperature, humidity, and marine and terrestrial environments. Furthermore, some types do not decompose under natural conditions, necessitating research into a unified processing method.

[0005] Accordingly, research is being conducted to process biodegradable plastics through anaerobic digestion, an organic recycling method that utilizes the biodegradability characteristic of biodegradable plastics. However, since complete decomposition is not achieved within about 40 days, which is the operating time of anaerobic digestion facilities operated in industry, technological development is needed to shorten the decomposition time.

[0006]

[0007] Prior art literature

[0008] (Non-patent literature 1) Park, Jeong-su, Joo, Heung-soo, Ryu, Jae-young, Bae, Jae-geun, and Jeon, Yeong-seung. (2002). Biodegradability of biodegradable plastics by anaerobic digestion. Organic Resource Recycling, 10(1).

[0009]

[0010] Therefore, the main purpose of the present invention is to provide a method for increasing the anaerobic digestion efficiency of biodegradable plastic and shortening the decomposition time.

[0011]

[0012] In one aspect, the present invention provides a thermochemical pretreatment method for anaerobic digestion of biodegradable plastics according to the following items:

[0013] 1. A thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, comprising the step of contacting the biodegradable plastic with a chemical substance capable of causing or accelerating a reduction in the molecular weight of the biodegradable plastic and heat-treating the same.

[0014] 2. A thermochemical pretreatment method for anaerobic digestion of biodegradable plastic, wherein in item 1, the contact is mixing the biodegradable plastic with an alkaline solution.

[0015] 3. A thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, wherein in item 1 or 2, the biodegradable plastic is one or more selected from the group consisting of poly lactic acid (PLA), poly butylene adipate terephthalate (PBAT), and poly butylene succinate (PBS).

[0016] 4. A thermochemical pretreatment method for anaerobic digestion of biodegradable plastic, wherein in item 2 or 3, the alkaline solution is a solution of an alkali selected from the group consisting of sodium hydroxide (NaOH) and potassium hydroxide (KOH).

[0017] 5. A thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, wherein in any one of items 2 to 4, the alkaline solution is a 0.13 to 0.75 M sodium hydroxide aqueous solution or a 0.09 to 0.53 M potassium hydroxide aqueous solution.

[0018] 6. A thermochemical pretreatment method for anaerobic digestion of biodegradable plastic, wherein the biodegradable plastic is mixed with the alkaline solution at a concentration of 50 to 300 g / ℓ in any one of items 2 to 5.

[0019] 7. A thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, wherein in any one of items 1 to 6, the heat treatment is performed at a temperature of 80 to 200°C for a period of less than 24 hours.

[0020] 8. A thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, wherein the anaerobic digestion is batch anaerobic digestion under mesophilic conditions in any one of items 1 to 7.

[0021]

[0022] The present invention significantly increases the efficiency of anaerobic digestion of biodegradable plastics, significantly reduces decomposition time, and thus significantly increases the production efficiency of biogas such as biomethane. Based on these findings, the present invention is expected to significantly contribute to the recycling of biodegradable plastics and, consequently, contribute significantly to the prevention of environmental pollution.

[0023]

[0024] Figure 1 shows the amount of biogas generated from anaerobic digestion of biodegradable plastic using a pretreatment method using an aqueous NaOH solution as an alkaline solution and PLA as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where the pretreatment method was not used.

[0025] Figure 2 shows the amount of biomethane generated from anaerobic digestion of biodegradable plastic using a pretreatment method using an aqueous NaOH solution as an alkaline solution and PLA as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where no pretreatment method was used.

[0026] Figure 3 shows the amount of biogas generated from anaerobic digestion of biodegradable plastic using a pretreatment method using a KOH aqueous solution as an alkaline solution and PLA as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where the pretreatment method was not used.

[0027] FIG. 4 shows the amount of biomethane generated from anaerobic digestion of biodegradable plastic using a pretreatment method using a KOH aqueous solution as an alkaline solution and PLA as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where no pretreatment method was used.

[0028] FIG. 5 shows the amount of biogas generated from anaerobic digestion of biodegradable plastic using a pretreatment method using an aqueous NaOH solution as an alkaline solution and PBAT as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where no pretreatment method was used.

[0029] FIG. 6 shows the amount of biomethane generated from anaerobic digestion of biodegradable plastic using a pretreatment method using an aqueous NaOH solution as an alkaline solution and PBAT as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where no pretreatment method was used.

[0030] Figure 7 shows the amount of biogas generated from anaerobic digestion of biodegradable plastic using a pretreatment method using a KOH aqueous solution as an alkaline solution and PBAT as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where the pretreatment method was not used.

[0031] FIG. 8 shows the amount of biomethane generated from anaerobic digestion of biodegradable plastic using a pretreatment method using a KOH aqueous solution as an alkaline solution and PBAT as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where no pretreatment method was used.

[0032] FIG. 9 shows the amount of biogas generated from anaerobic digestion of biodegradable plastic using a pretreatment method using an aqueous NaOH solution as an alkaline solution and PBS as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where no pretreatment method was used.

[0033] FIG. 10 shows the amount of biomethane generated from anaerobic digestion of biodegradable plastic using a pretreatment method using an aqueous NaOH solution as an alkaline solution and PBS as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where no pretreatment method was used.

[0034] Figure 11 shows the amount of biogas generated from anaerobic digestion of biodegradable plastic using a pretreatment method using an aqueous KOH solution as an alkaline solution and PBS as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where no pretreatment method was used.

[0035] Figure 12 shows the amount of biomethane generated by anaerobic digestion of biodegradable plastic using a pretreatment method using an aqueous KOH solution as an alkaline solution and PBS as a biodegradable plastic as a pretreatment method according to one embodiment of the present invention, compared to the case where no pretreatment method was used.

[0036]

[0037] The present invention relates to a thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, comprising the step of contacting the biodegradable plastic with a chemical substance capable of causing or accelerating a reduction in the molecular weight of the biodegradable plastic and heat treating the biodegradable plastic.

[0038] By using the pretreatment method of the present invention, it is possible to expect an effect of increasing the efficiency of anaerobic digestion of biodegradable plastics, for example, an effect of increasing the anaerobic digestion rate, and / or an effect of increasing the production efficiency of biogas, for example, biomethane, resulting from anaerobic digestion of biodegradable plastics, compared to, for example, anaerobic digestion without using the pretreatment method of the present invention.

[0039] In the present invention, the chemical agent, i.e., the chemical agent capable of causing or accelerating a reduction in the molecular weight of the biodegradable plastic, may be an alkali, and the contact may be mixing the biodegradable plastic with an alkaline solution.

[0040] In the present invention, the biodegradable plastic is capable of anaerobic digestion and may be a biodegradable plastic known to be applicable to anaerobic digestion. For the expected effects of the present invention, it is preferably one or two or more selected from the group consisting of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBS).

[0041] In the present invention, the alkaline solution may be any alkaline solution known to be applicable to the solubilization of biodegradable plastics. For the expected effects of the present invention, it is preferably an alkaline solution selected from the group consisting of sodium hydroxide (NaOH) and potassium hydroxide (KOH).

[0042] In addition, the alkaline solution of the present invention is preferably a 0.13 M or more (0.5% (w / v) or more) sodium hydroxide aqueous solution for the expected effects of the present invention. More preferably, the alkaline solution of the present invention is a 0.15 M or more (0.6% (w / v) or more) sodium hydroxide aqueous solution, more preferably a 0.18 M or more (0.7% (w / v) or more) sodium hydroxide aqueous solution, more preferably a 0.2 M or more (0.8% (w / v) or more) sodium hydroxide aqueous solution, more preferably a 0.23 M or more (0.9% (w / v) or more) sodium hydroxide aqueous solution, and more preferably a 0.25 M or more (1% (w / v) or more) sodium hydroxide aqueous solution. At this time, the upper limit of the sodium hydroxide molar concentration of the sodium hydroxide aqueous solution may be 2.5 M (10% (w / v)), preferably 2.25 M (9% (w / v)), more preferably 2 M (8% (w / v)), more preferably 1.75 M (7% (w / v)), more preferably 1.5 M (6% (w / v)), more preferably 1.25 M (5% (w / v)), more preferably 1 M (4% (w / v)), more preferably 0.75 M (3% (w / v)).

[0043] In addition, the alkaline solution of the present invention is preferably a 0.09 M or more (0.5% (w / v) or more) potassium hydroxide aqueous solution for the expected effects of the present invention. More preferably, the alkaline solution of the present invention is a 0.11 M or more (0.6% (w / v) or more) potassium hydroxide aqueous solution, more preferably a 0.12 M or more (0.7% (w / v) or more) potassium hydroxide aqueous solution, more preferably a 0.14 M or more (0.8% (w / v) or more) potassium hydroxide aqueous solution, more preferably a 0.16 M or more (0.9% (w / v) or more) potassium hydroxide aqueous solution, and more preferably a 0.18 M or more (1% (w / v) or more) potassium hydroxide aqueous solution. At this time, the upper limit of the potassium hydroxide molar concentration of the potassium hydroxide aqueous solution may be 1.78 M (10% (w / v)), preferably 1.6 M (9% (w / v)), more preferably 1.43 M (8% (w / v)), more preferably 1.25 M (7% (w / v)), more preferably 1.07 M (6% (w / v)), more preferably 0.89 M (5% (w / v)), more preferably 0.71 M (4% (w / v)), more preferably 0.53 M (3% (w / v)).

[0044] For the expected effects of the present invention, preferably, the biodegradable plastic is mixed with an alkaline solution at a concentration of 1000 g / ℓ or less. More preferably, the biodegradable plastic is mixed with an alkaline solution at a concentration of 900 g / ℓ or less, more preferably, it is mixed with an alkaline solution at a concentration of 800 g / ℓ or less, more preferably, it is mixed with an alkaline solution at a concentration of 700 g / ℓ or less, more preferably, it is mixed with an alkaline solution at a concentration of 600 g / ℓ or less, more preferably, it is mixed with an alkaline solution at a concentration of 500 g / ℓ or less, more preferably, it is mixed with an alkaline solution at a concentration of 400 g / ℓ or less, more preferably, it is mixed with an alkaline solution at a concentration of 300 g / ℓ or less, more preferably, it is mixed with an alkaline solution at a concentration of 200 g / ℓ or less, and more preferably, it is mixed with an alkaline solution at a concentration of 150 g / ℓ or less. At this time, the lower limit of the concentration of biodegradable plastic may be 10 g / ℓ, preferably 20 g / ℓ, more preferably 30 g / ℓ, more preferably 40 g / ℓ, more preferably 50 g / ℓ, more preferably 60 g / ℓ, more preferably 70 g / ℓ, more preferably 80 g / ℓ, more preferably 90 g / ℓ.

[0045] In the present invention, the heat treatment is preferably performed at a temperature of 80°C or higher to achieve the expected effects of the present invention. More preferably, the heat treatment is performed at a temperature of 85°C or higher, more preferably at a temperature of 90°C or higher, and even more preferably at a temperature of 95°C or higher. At this time, the upper limit of the heat treatment temperature may be 200°C, preferably 150°C, more preferably 130°C, more preferably 120°C, preferably 115°C, more preferably 110°C, more preferably 105°C, and even more preferably 100°C.

[0046] In addition, in the present invention, the heat treatment is preferably performed for a period of less than 24 hours to achieve the expected effects of the present invention. More preferably, the heat treatment is performed for a period of 1 to 24 hours, more preferably for a period of 6 to 24 hours, and even more preferably for a period of 12 to 24 hours.

[0047] In the present invention, anaerobic digestion is anaerobic digestion under mesophilic conditions (e.g., temperature conditions of 35 to 45°C) or high-temperature conditions (e.g., temperature conditions of 50 to 60°C), and for the expected effects of the present invention, batch anaerobic digestion under mesophilic conditions is preferably used. That is, the pretreatment method of the present invention can be expected to have a better effect when applied as a pretreatment method for a biodegradable plastic treatment process using a batch anaerobic digestion method under mesophilic conditions.

[0048] In addition, the anaerobic digestion of the present invention is preferably batch anaerobic digestion under mesophilic conditions with an F / M ratio of 1 to 2 for the expected effects of the present invention. More preferably, the anaerobic digestion of the present invention is batch anaerobic digestion under mesophilic conditions with an F / M ratio of 1.1 to 1.9, more preferably batch anaerobic digestion under mesophilic conditions with an F / M ratio of 1.2 to 1.8, more preferably batch anaerobic digestion under mesophilic conditions with an F / M ratio of 1.3 to 1.7, more preferably batch anaerobic digestion under mesophilic conditions with an F / M ratio of 1.3 to 1.6, and more preferably batch anaerobic digestion under mesophilic conditions with an F / M ratio of 1.4 to 1.5.

[0049]

[0050] Hereinafter, the present invention will be described in more detail through examples. These examples are intended merely to illustrate the present invention, and therefore, the scope of the present invention is not to be construed as being limited by these examples.

[0051]

[0052] [Example]

[0053] Example 1

[0054] A 0.13 to 0.75 M (corresponding to approximately 0.5 to 3% (w / v)) sodium hydroxide (NaOH) aqueous solution was prepared as an alkaline solution, transferred to a test tube, and then 50 to 300 g / ℓ of polylactic acid (PLA) as a biodegradable plastic was added. At this time, PLA was used in the form of flakes. The test tube containing the PLA-containing alkaline solution was placed in a stainless steel shaker and heated at 80 to 100°C for 12 to 24 hours (pretreatment step).

[0055] After the pretreatment step, the batch anaerobic digestion step was performed under mesophilic conditions (approximately 40°C). The seed sludge was collected from the anaerobic digestion tank in the Goyang Biomass Energy Facility in Gyeonggi-do, and the F / M ratio (substrate to sludge concentration ratio) was set to approximately 1.42 (where the substrate was a biodegradable plastic with a concentration of approximately 10 g / ℓ and the sludge concentration was approximately 7.1 g / ℓ). In addition, the medium and composition at this time were based on the literature [Angelidaki, I., Alves, M., Bolzonella, D., Borzacconi, L., Campos, JL, Guwy, AJ, Kalyuzhnyi, S., Jenicek, P., Van Lier, JB (2009). Defining the biomethane potential (BMP) of solid organic wastes and energy crops: a proposed protocol for batch assays. The anaerobic culture medium was referenced from [Water science and technology, 59 (5), 927-934].

[0056]

[0057] Example 2

[0058] The same method as in Example 1 was used, but instead of the NaOH aqueous solution, a 0.09 to 0.53 M (corresponding to approximately 0.5 to 3% (w / v)) potassium hydroxide (KOH) aqueous solution was used.

[0059]

[0060] Example 3

[0061] The same method as in Example 1 was used, but polybutylene adipate terephthalate (PBAT) was used instead of PLA. In this case, PBAT was used in film form.

[0062]

[0063] Example 4

[0064] The same method as in Example 3 was used, but a 0.09 to 0.53 M KOH aqueous solution was used instead of the NaOH aqueous solution.

[0065]

[0066] Example 5

[0067] The same method as in Example 1 was used, but polybutylene succinate (PBS) was used instead of PLA. In this case, PBS was used in powder form.

[0068]

[0069] Example 6

[0070] The same method as in Example 5 was used, but a 0.09 to 0.53 M KOH aqueous solution was used instead of the NaOH aqueous solution.

[0071]

[0072] Comparative Example 1

[0073] The same method as in Example 1 was used, but water was used instead of the NaOH aqueous solution.

[0074]

[0075] Comparative Example 2

[0076] The same method as in Example 2 was used, but water was used instead of the KOH aqueous solution.

[0077]

[0078] Comparative Example 3

[0079] The same method as in Example 3 was used, but water was used instead of the NaOH aqueous solution.

[0080]

[0081] Comparative Example 4

[0082] The same method as in Example 4 was used, but water was used instead of the KOH aqueous solution.

[0083]

[0084] Comparative Example 5

[0085] The same method as in Example 5 was used, but water was used instead of the NaOH aqueous solution.

[0086]

[0087] Comparative Example 6

[0088] The same method as in Example 6 was used, but water was used instead of the KOH aqueous solution.

[0089]

[0090] Comparative Example 7

[0091] The same method as in Example 1 was used, but the pretreatment step was omitted. At this time, PLA that had not undergone the pretreatment step was fed as a substrate in the batch anaerobic digestion step, and the same amount of PLA as in Example 1 was fed based on gVS.

[0092]

[0093] Comparative Example 8

[0094] The same method as in Example 3 was used, but the pretreatment step was omitted. At this time, PBAT that had not undergone the pretreatment step was fed as a substrate in the batch anaerobic digestion step, and the same amount of PBAT as in Example 3 was fed based on gVS.

[0095]

[0096] Comparative Example 9

[0097] The same method as in Example 5 was used, but the pretreatment step was omitted. At this time, PBS that had not undergone the pretreatment step was fed as a substrate to the batch anaerobic digestion step, and the same amount of PBS as in Example 5 was fed based on gVS.

[0098]

[0099] Experimental Example 1

[0100] In Examples 1 to 6 and Comparative Examples 1 to 6, the solubilization rate (the amount of dissolved substances increased after pretreatment compared to the amount of biodegradable plastic input) according to the pretreatment step was investigated. At this time, the investigation was conducted based on the case where the concentration of each biodegradable plastic input was 100 g / ℓ.

[0101] As a result, as shown in Tables 1 to 6, it was found that the solubilization rate was significantly increased when alkali (NaOH or KOH) was used compared to when it was not used, and this increase in solubilization rate was found to increase as the concentration of alkali increased and the heating temperature increased.

[0102] In addition, based on these results, it was determined that the pretreatment temperature should be 95℃ or higher, the pretreatment time should be 12 hours or higher, and the concentration of the alkaline solution used for pretreatment should be 0.25M or higher for NaOH and 0.18M or higher for KOH to easily reach a solubilization rate of 70% or higher.

[0103] PLA pretreated with NaOH aqueous solution (Example 1) Solubilization rate data Temperature (℃) 80 90 100 Hours (h) Concentration (M) Solubilization rate (%) Solubilization rate (%) Solubilization rate (%) 120 (Comparative Example 1) 0.10 24.6 0.13 6.3 19.13 0.40 25 11.8 36.6 52.0 0.38 32.8 45.77 0.30 54 0.25 9.77 8.30 63 50.46 7.08 0.60 75 66.9 75.78 3.5 180 (Comparative Example) 1) 0.11.68.90.1316.230.639.60.2526.752.769.30.3844.471.578.10.553.385.782.00.636093.692.80.7577.194.594.8240 (Comparative Example 1) 0.23.39.10.1320.233.149.70.2530.253.067.90.3848.571.077.70.556.883.786.80.6362.893.895.80.7586.493.899.9

[0104]

[0105] PLA pretreated with KOH aqueous solution (Example 2) Solubilization rate data Temperature (℃) 80 90 100 Hours (h) Concentration (M) Solubilization rate (%) Solubilization rate (%) Solubilization rate (%) 120 (Comparative Example 2) 0.3 0.5 5.3 0.0 99 16.9 3 0.10 18 16.3 2 4.15 1.5 0.2 7 2 0.4 4 3.4 6 7.7 0.3 6 2 3.8 5 7.4 7 8.8 0.4 5 36 6 6.3 8 4.7 0.5 3 5 0.3 7 0 8 5.5 1 8 0 (Comparative Example) 2) 0.51.590.0912.32830.70.1824.450.956.50.2726.368.771.30.3631.981.379.60.4542.388.885.40.5367.691.194.8240 (Comparative Example 2) 0.42.79.40.0918.735.336.50.1833.256.860.50.2752.573.173.90.3666.784.381.70.4575.790.485.20.5379.591.297.1

[0106]

[0107] PBAT pretreated with NaOH aqueous solution (Example 3) Solubilization rate data Temperature (℃) 80 90 100 Hours (h) Concentration (M) Solubilization rate (%) Solubilization rate (%) Solubilization rate (%) 120 (Comparative Example 3) 0.10.0 0.7 0.13 13.84 9.26 6.7 0.25 21.58 7.89 1.90.38 23.89 1.59 4.6 0.53 1.89 1.59 4.10.6 3 45.49 2.79 7.6 0.75 54.79 3.19 7.7 180 (Comparative Example) 3)0.10.50.80.1315.359.970.70.2527.291.193.20.3826.292.195.00.540.895.496.70.6351.195.597.90.756795.698.9240 (Comparative Example 3)0.20.80.80.1328.673.770.40.2538.791.595.60.3850.492.998.10.555.793.398.90.6372.697.299.20.7575.298.999.4

[0108]

[0109] PBAT pretreated with KOH aqueous solution (Example 4) Solubilization rate data Temperature (℃) 80 90 100 Hours (h) Concentration (M) Solubilization rate (%) Solubilization rate (%) Solubilization rate (%) 120 (Comparative Example 4) 0.2 0.3 0.6 0.0 9 5.7 38.4 4 0.9 0.1 8 16.3 6 1.6 6 5.8 0.2 7 20.4 7 9 8 2.8 0.3 6 3 3.8 8 6.4 9 20.4 5 4 8 8 7.1 9 3.4 0.5 3 5 0 9 0.3 9 6.9 1 8 0 (Comparative Example) 4) 0.30.50.70.099.241.946.10.1833.667.771.10.2750.185.688.30.3658.892.895.60.4559.697.797.80.5372.599.298.2240 (Comparative Example 4) 0.70.810.0925.444.552.60.1850.669.270.40.27688888.50.3677.595.598.90.4579.298.799.10.538399.199.7

[0110]

[0111] PBS pretreated with NaOH aqueous solution (Example 5) Solubilization rate data Temperature (℃) 80 90 100 Hours (h) Concentration (M) Solubilization rate (%) Solubilization rate (%) Solubilization rate (%) 120 (Comparative Example 5) 0 0.2 2.5 0.13 1.12 116.5 0.25 10.5 20.7 31.4 0.38 20.9 37.7 42.30.5 37 53.16 1.6 0.6 34 0.76 6.7 79.30.75 49 77.3 85.4 180 (Comparative Example) 5)0.10.33.20.133.41521.90.2512.731.3420.3822.745.967.40.53958.977.40.6344.170.482.70.7560.180.286.4240(Comparative Example 5)0.12.34.60.1312.728.528.50.2525.75262.70.3828.564.368.80.542.574.983.40.6357.78496.30.7571.391.597.6

[0112]

[0113] PBS pretreated with KOH aqueous solution (Example 6) Solubilization rate data Temperature (℃) 80 90 100 Hours (h) Concentration (M) Solubilization rate (%) Solubilization rate (%) Solubilization rate (%) 120 (Comparative Example 6) 0 0.4 2.10.0 9 5.7 19 36.8 0.18 13.33 6.35 1.7 0.27 18.85 1.16 4.10.36 28 63.47 4.10.45 40.17 3.28 1.50.53 49.88 0.68 6.5 180 (Comparative Example 6)0.10.53.50.09835.437.90.1817.752.652.80.2724.865.367.40.3639.475.279.70.4551.682.789.50.5371.387.796.9240 (Comparative Example 6)0.224.40.0924.83744.30.1834.554.359.30.2751.66971.70.3656.281.481.70.4568.489.191.20.5378.194.198.5

[0114]

[0115] Experimental Example 2

[0116] The biogas (biomethane and carbon dioxide) and biomethane production amounts according to Examples 1 to 6 and Comparative Examples 7 to 9 were investigated. At this time, the concentration of each biodegradable plastic input was based on the case of 100 g / ℓ, and each pretreatment temperature, pretreatment time, and concentration of alkaline solution used for pretreatment were set as follows based on the results of Experimental Example 1, and the biogas and biomethane generation amounts were investigated based on these: Example 1 was based on the case where a 0.28 M (equivalent to about 1.13% (w / v)) NaOH aqueous solution was used and heated at 100°C for 18 hours, Example 2 was based on the case where a 0.3 M (equivalent to about 1.71% (w / v)) KOH aqueous solution was used and heated at 95°C for 18 hours, Example 3 was based on the case where a 0.37 M (equivalent to about 1.47% (w / v)) NaOH aqueous solution was used and heated at 95°C for 12 hours, and Example 4 was based on the case where a 0.21 M (equivalent to about 1.16% (w / v)) KOH aqueous solution was used. Based on the case of heating at 95°C for 12 hours, Example 5 was investigated using a 0.41 M (equivalent to approximately 1.62% (w / v)) NaOH aqueous solution and heating at 95°C for 22.8 hours, and Example 6 was investigated using a 0.42 M (equivalent to approximately 2.33% (w / v)) KOH aqueous solution and heating at 95°C for 18 hours.

[0117] The results are shown in Figures 1 to 12, and the cumulative amount of biogas or biomethane produced is summarized in Tables 7 and 8.

[0118] In all cases, the production of biogas and biomethane was significantly higher in the alkaline (NaOH or KOH) pretreated experimental groups (Examples 1 to 6) compared to the non-pretreatment experimental groups (Comparative Examples 7, 8, or 9). This demonstrates that the pretreatment method of the present invention can increase the production efficiency of biogas, particularly biomethane, from biodegradable plastics. In addition, this demonstrates that the use of the pretreatment method of the present invention can increase the decomposition rate of biodegradable plastics, thereby shortening the decomposition time.

[0119] Biodegradable plastic type Chemical type Cumulative biogas generation (mL / gVS) N times more than without pretreatment Without pretreatment With pretreatment PLANaOH 3306181.84 KOH 3306922.09 PBATNaOH 3064531.48 KOH 3064471.46 PBSNaOH 3214381.36 KOH 3214751.48

[0120]

[0121] Biodegradable plastic type Chemical substance type Cumulative biomethane generation (mLCH4 / gVS) N times higher than without pretreatment Without pretreatment With pretreatment PLANaOH 191537.99 KOH 191718.91 PBATNaOH 18794.5 KOH 18905.09 PBSNaOH 251064.21 KOH 251134.49

Claims

1. A thermochemical pretreatment method for anaerobic digestion of a biodegradable plastic, comprising the step of contacting the biodegradable plastic with a chemical substance capable of causing a reduction in the molecular weight of the biodegradable plastic or accelerating the reduction in the molecular weight of the biodegradable plastic and subjecting the biodegradable plastic to heat treatment.

2. In paragraph 1, A thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, wherein the above contact comprises mixing the biodegradable plastic with an alkaline solution.

3. In paragraph 1, A thermochemical pretreatment method for anaerobic digestion of a biodegradable plastic, wherein the biodegradable plastic is one or more selected from the group consisting of polylactic acid, polybutylene adipate terephthalate and polybutylene succinate.

4. In paragraph 2, A thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, wherein the alkaline solution is a solution of an alkali selected from the group consisting of sodium hydroxide and potassium hydroxide.

5. In paragraph 4, A thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, wherein the alkaline solution is a 0.13 to 0.75 M sodium hydroxide aqueous solution or a 0.09 to 0.53 M potassium hydroxide aqueous solution.

6. In paragraph 2, A thermochemical pretreatment method for anaerobic digestion of biodegradable plastic, wherein the biodegradable plastic is mixed with the alkaline solution at a concentration of 50 to 300 g / ℓ.

7. In paragraph 1, A thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, wherein the above heat treatment is performed at a temperature of 80 to 200°C for a period of less than 24 hours.

8. In paragraph 1, The above anaerobic digestion is a thermochemical pretreatment method for anaerobic digestion of biodegradable plastics, which is a batch anaerobic digestion under mesophilic conditions.

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