DEVICE FOR ELECTROCHEMICALLY ASSISTED AEROBIC COMPOSTING OF ORGANIC SOLID WASTE AND METHOD THEREFOR

Abstract

The present disclosure discloses a device for electrochemically assisted aerobic composting of organic solid waste and method therefor. The aerobic composting device includes a compost bioreactor, a working electrode, an auxiliary electrode, and a reference electrode. The working electrode is situated on the inner wall of the compost bioreactor, and the reference electrode is situated between the working electrode and the auxiliary electrode. The bottom of the compost bioreactor is provided with a ventilation pipeline with an aeration head. A method for electrochemically assisted aerobic composting of organic solid waste by using the device is also disclosed. By performing electrochemically assisted composting through the composting device of the present disclosure can enrich and utilize electric energy microorganisms to promote the progress of the redox reaction in the compost pile, quickly increase the temperature of the compost, shorten the compost period, and increase the compost maturity.

Claims

1. A device for electrochemically assisted aerobic composting of organic solid waste, comprising a compost bioreactor, a working electrode, an auxiliary electrode, and a reference electrode; the working electrode is provided on an inner wall of the compost bioreactor, and the reference electrode is situated between the working electrode and the auxiliary electrode; a ventilation pipeline with an aeration head is provided at a bottom of the compost bioreactor.

2. The device for electrochemically assisted aerobic composting of organic solid waste according to claim 1, wherein a distance between the working electrode and the auxiliary electrode is 10 cm to 100 cm.

3. The device for electrochemically assisted aerobic composting of organic solid waste according to claim 1, wherein the working electrode is at least one selected from the group consisting of a stainless steel plate, a graphite plate, a carbon felt, and a carbon cloth electrode; the auxiliary electrode is at least one selected from the group consisting of a carbon felt, a carbon cloth, and a graphite electrode; the reference electrode is one selected from the group consisting of a Hg/HgO electrode, an Ag/AgCl electrode, a hydrogen standard electrode, and a saturated calomel electrode.

4. The device for electrochemically assisted aerobic composting of organic solid waste according to claim 3, wherein the potential of the working electrode relative to the reference electrode is set to 5 V to 5 V.

5. The device for electrochemically assisted aerobic composting of organic solid waste according to claim 1, wherein the working parameters of aeration of the ventilation pipeline are: once to twice a day, each aeration is for 15 minutes to 30 minutes, a flow rate of the aeration is 0.1 L/min.Math.m.sup.3 to 0.2 L/min.Math.m.sup.3.

6. The device for electrochemically assisted aerobic composting of organic solid waste according to claim 1, wherein the compost bioreactor is covered with a thermal insulation layer.

7. A method for electrochemically assisted aerobic composting of organic solid waste, comprising 1) mixing organic solid waste and auxiliary material, adding water and stirring evenly to obtain compost raw material; 2) placing the composting raw material into the device of claim 1 to perform composting.

8. The method for electrochemically assisted aerobic composting of organic solid waste according to claim 7, wherein in step 1), a mass ratio of the organic solid waste and the auxiliary material is 10:(1 to 3).

9. The method for electrochemically assisted aerobic composting of organic solid waste according to claim 7, wherein in step 1), the water content of the compost raw material is 50 wt % to 60 wt %.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a schematic structural diagram of a device provided by the present disclosure;

[0025] FIG. 2 is a graph showing changes in compost temperature with the turning compost time in embodiment 1 and comparative example 1;

[0026] FIG. 3 is a graph showing changes in compost temperature with the turning compost time in embodiment 2 and comparative example 2;

[0027] FIG. 4 is a graph showing changes in compost temperature with the turning compost time in embodiment 3 and comparative example 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] A device for electrochemically assisted aerobic composting of organic solid waste, including a compost bioreactor, a working electrode, an auxiliary electrode, and a reference electrode. The working electrode is provided on the inner wall of the compost bioreactor, and the reference electrode is situated between the working electrode and the auxiliary electrode. A ventilation pipeline with an aeration head is provided at the bottom of the compost bioreactor.

[0029] Preferably, in the device, the compost bioreactor is a cylindrical reactor or a strip reactor.

[0030] Further, when the compost bioreactor is a cylindrical reactor, the diameter is 50 cm to 80 cm, and the height is 80 cm to 120 cm; when the compost bioreactor is a strip reactor, the length is 1.5 m to 2.5 m, the width is 0.5 m to 1.5 m, and the height is 0.5 m to 1.5 m.

[0031] Further, in the device, the distance between the working electrode and the auxiliary electrode is 10 cm to 100 cm.

[0032] Preferably, in the device, the working electrode is at least one selected from the group consisting of a stainless steel plate, a graphite plate, a carbon felt, and a carbon cloth electrode; the auxiliary electrode is at least one selected from the group consisting of a carbon felt, a carbon cloth, and a graphite electrode; the reference electrode is one selected from the group consisting of a Hg/HgO electrode, an Ag/AgCl electrode, a hydrogen standard electrode, and a saturated calomel electrode.

[0033] Preferably, in the device, the potential of the working electrode relative to the reference electrode is set 5 V to 5 V.

[0034] Preferably, in the device, the diameter of the ventilation pipeline is 8 mm to 20 mm.

[0035] Preferably, in the device, working parameters of the aeration of the ventilation pipeline are: once to twice a day, each aeration is for 15 minutes to 30 minutes, and the flow rate of the aeration is 0.1 L/min.Math.m.sup.3 to 0.2 L/min.Math.m.sup.3.

[0036] Preferably, in the device, the compost bioreactor is covered with a thermal insulation layer. Further, the thermal insulation material used for the thermal insulation layer is a conventional choice in the field and can be one selected from the group consisting of quilts, aluminum foil self-adhesive rubber-plastic sheets, high-temperature resistant aluminum silicate needle punched ceramic fiber thermal insulation cotton, flame-retardant rubber-plastic sponge, and glass wool.

[0037] Preferably, in the device, a temperature probe (online thermometer) is set around the compost bioreactor to record the temperature change of compost in real-time.

[0038] A method for electrochemically assisted aerobic composting of organic solid waste, including the following steps:

[0039] 1) mixing organic solid waste and auxiliary material, adding water and stirring evenly to obtain compost raw material;

[0040] 2) placing the composting raw material into the device for electrochemically assisted aerobic composting of organic solid waste mentioned above to perform composting.

[0041] Preferably, in step 1), the mass ratio of the organic solid waste and the auxiliary material is 10:(1 to 3).

[0042] Preferably, in step 1) of the composting method, the organic solid waste is at least one of chicken manure, duck manure, goose manure, pig manure, cow manure, dog manure, cat manure, sheep manure, horse manure, or sludge.

[0043] Preferably, in step 1) of the composting method, the auxiliary material is at least one of rice bran, straw, or rice husk.

[0044] Preferably, in step 1), the water content of the compost raw material is: 50 wt % to 60 wt %.

[0045] FIG. 1 is a structural diagram of the device of the present disclosure, which only represents one example of the device of the present disclosure, and the device of the present disclosure is not limited to the structure shown in the diagram. In FIG. 1, 1potentiostat; 2working electrode; 3the outer wall of compost bioreactor; 4reference electrode; 5auxiliary electrode; 6thermal insulation layer; 7air pump; 8aeration head.

[0046] In combination with FIG. 1, the content of the present disclosure will be further described in detail through specific embodiments. The raw materials used in the embodiment can be obtained from conventional commercial channels without special description.

Embodiment 1

[0047] 1) Design of Compost Bioreactor:

[0048] When the cylindrical compost reactor is adopted, the diameter is 55 cm and the height is 100 cm. A rectangular working electrode is arranged along the inner wall of the plastic barrel, which is made of stainless steel sheet with an area of 3 to 5 m.sup.2. A cylindrical auxiliary electrode is placed in the center of the plastic barrel, the circular tube is the inner center with a diameter of 5 cm and a height of 8 0 cm, and a saturated calomel reference electrode is connected at the upper portion of the plastic barrel. The bottom of the plastic barrel is provided with a ventilation pipeline, wherein the diameter of the ventilation pipeline is 10 mm. To ensure uniform aeration, the height of the ventilation pipeline is 30 to 50 cm, from the bottom to the 30 cm position, the aeration holes are punched every 10 cm, and from the 30 cm position to the 50 cm position, and aeration holes are punched every 20 cm. The outer wall of the plastic barrel is wrapped with cotton fiber, which is used for heat preservation of the reactor. At the same time, an online thermometer is set around the plastic barrel to record the temperature change of compost in real-time.

[0049] 2) Compost Raw Material and Proportion Thereof:

[0050] Chicken manure is used as the main compost material and rice bran as the auxiliary material. The above raw material and ingredients are evenly mixed to ensure moisture content at 50% to 60%; the evenly stirred manure is placed into the designed compost bioreactor, connecting the potentiostat, and conducting aerobic composting.

[0051] 3) Operational Parameters:

[0052] Composting at room temperature. Connecting the potentiostat, the potential of the working electrode is designed as 2 V (the reference electrode is a saturated calomel electrode). A small air pump is used as the air source for aeration once a day, the aeration time is 15 minutes each time, and the aeration flow is 0.15 L/min.Math.m.sup.3. Every 10 days is the turning cycle at which turning is carried out. When the compost pile is turned over, after mixing evenly, the potentiostat can be connected for recomposting.

Embodiment 2

[0053] When the strip compost reactor is adopted, which is 2 m long, 1 m wide and 1 m high, a rectangular working electrode is arranged along the long side and the material is a graphite plate with an area of about 1 m.sup.2. On the other side of the long side, an auxiliary electrode of the same size is placed. A saturated calomel reference electrode is connected to the upper portion of the compost pile. The bottom is provided with a ventilation pipeline, wherein the diameter of the ventilation pipeline is 10 mm. To ensure uniform aeration, the height of the ventilation pipeline is 30 to 50 cm, from the bottom to the 30 cm position, aeration holes are punched every 10 cm, and from the 30 cm position to the 50 cm position, the aeration holes are punched every 20 cm. The aeration working parameters are the same as those in Embodiment 1. The outer wall of the reactor is wrapped with cotton fiber for heat preservation of the reactor. At the same time, an online thermometer is set around the interior of the compost pile to record the temperature change of compost in real-time. The potential of the potentiostat is set to +5 V vs SCE (the saturated calomel electrode is the reference electrode).

[0054] Sludge is used as the composting raw material, straw is used as the auxiliary material, the mass ratio is 10:3, and the rest is the same as that of Embodiment 1.

Embodiment 3

[0055] In Embodiment 3 and Embodiment 2, the same compost bioreactor is used, pig manure is used as the composting raw material, rice husk as the auxiliary material, a mass ratio of 10:1, and the potential of the potentiostat is set as: 5 V vs SCE (the saturated calomel electrode as reference electrode). The rest is the same as that of Embodiment 1.

Comparative Example 1

[0056] Without using the device for electrochemically assisted aerobic composting of organic solid waste, the same composting raw material as in Embodiment 1 is taken for conventional composting treatment.

Comparative Example 2

[0057] Without using the device for electrochemically assisted aerobic composting of organic solid waste, the same composting raw material as in Embodiment 2 is taken for conventional composting treatment.

Comparative Example 3

[0058] Without using the device for electrochemically assisted aerobic composting of organic solid waste, the same composting raw material as in Embodiment 3 is taken for conventional composting treatment.

Composting Effect:

1. Composting Effects of Embodiment 1 and Comparative Example 1

[0059] FIG. 2 is a graph showing changes in compost temperature with the turning compost time in embodiment 1 and comparative example 1. As shown in FIG. 2, the maximum temperature of electrochemically assisted composting is 63.5 C., which is 6.2 C. higher than that of conventional composting (57.3 C.). In the second and third cycles of compost turning, the temperature difference is more significant. This shows that the electrochemical method can further improve the compost temperature, which is more conducive to killing eggs, pathogens, etc.

[0060] DOM (dissolved organic matter), DON (dissolved organic nitrogen), and EC (electrical conductivity) are the key indicators to characterize the compost maturity. Thus, DOM, DON, and EC of compost were analyzed by three-dimensional fluorescence spectrum after composting for 30 days. The results show that after 30 days composting, the DOM, DON, and EC in the conventional composting system were 855.6 mg/L, 329 mg/L, and 36.2 S/m, respectively, and the removal rate of DOM was 33.8%. The DOM, DON, and EC of the electrochemically assisted composting system were 710.3 mg/L, 469 mg/L, and 30.8 S/m, respectively, and the removal rate of DOM was 45.1%, which is 11.3% higher than that of the conventional composting system. The results show that electrochemically assisted composting promotes the humification of compost.

[0061] At the same time, the products from the above two composting methods were tested by verifying the seed germination index. The germination index (GI) of the product seed in conventional compost is 99%; the germination index (GI) of electrochemically assisted compost is 138%, which is 39% higher than that of conventional compost. The results showed that the seed germination rate of compost could be significantly increased by the electrochemically assisted method.

2. Composting Effect of Embodiment 2 and Comparative Example 2

[0062] FIG. 3 is a graph showing changes in compost temperature with the turning compost time in embodiment 2 and comparative example 2. As can be seen from FIG. 3, the maximum temperature of electrochemically assisted composting is 63.3 C., the temperature of conventional composting is 58.1 C., and the temperature of electrochemically assisted composting is 5.2 C. higher than that of conventional composting. The germination index (GI) of the seed product in conventional compost is 92%, and the germination index (GI) of electrochemically assisted compost is 142%, which is 50% higher than that of conventional compost.

3. Composting Effect of Embodiment 3 and Comparative Example 3

[0063] FIG. 4 is a graph showing changes in compost temperature with the turning compost time in embodiment 3 and comparative example 3. As can be seen from FIG. 4, the maximum temperature of electrochemically assisted composting is 66 C., the temperature of conventional composting is 59 C., and the temperature of electrochemically assisted composting is 7 C. higher than that of conventional composting. The germination index (GI) of the seed product in conventional compost is 98%, and the germination index (GI) of electrochemically assisted compost is 145%, which is 47% higher than that of conventional compost.

[0064] It can be seen from the above embodiments that the temperature of the electrochemically assisted composting is higher than that of conventional composting. In the second and third cycles of compost turning, the temperature difference is more significant. Under the second turning cycle, the temperature of conventional compost decreased to 55 C., while under electrochemical action, the temperature of the second cycle did not decrease, but, instead, increased by 3-4 C. relative to that of the first cycle. This is because under the action of electrochemistry, the electric energy microorganism can be enriched, and the organic matters that cannot be degraded in the process of conventional composting are utilized by the electric energy microorganisms so that the composting temperature increases. These results show that the electrochemically assisted composting can promote the redox reaction in the compost pile, improve the composting temperature rapidly, shorten the composting cycle, improve the compost maturity and save costs.