CN114315485A

CN114315485A - Kitchen waste aerobic composting method and application thereof and compost

Info

Publication number: CN114315485A
Application number: CN202210033636.0A
Authority: CN
Inventors: 孙照勇; 高杨; 汤岳琴
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2022-01-12
Filing date: 2022-01-12
Publication date: 2022-04-12

Abstract

The invention discloses a kitchen waste aerobic composting method and application and composting thereof. According to the invention, the auxiliary materials are adopted to prepare the kitchen waste, then the mature compost of the kitchen waste is used as an aerobic compost strain for aerobic fermentation, and a semi-continuous feeding mode is adopted, so that the kitchen waste with the same weight is treated, the treatment time required by the invention is obviously reduced, and the treatment efficiency of the kitchen waste is improved; the invention adopts the composting reactor for composting, effectively prevents odor from being discharged inorganically in the composting process, is particularly suitable for distributed on-site treatment of kitchen garbage, and has simple equipment and easy maintenance.

Description

Kitchen waste aerobic composting method and application thereof and compost

Technical Field

The invention relates to the technical field of compost, in particular to an aerobic composting method of kitchen garbage, application thereof and compost.

Background

With the increasing speed of urbanization footsteps in China, the yield of urban domestic garbage is increased by 8-12% year by year. The kitchen waste is used as the most abundant component in the municipal domestic waste, and the yield is increased. Statistical data show that the yield of kitchen garbage in China in 2018 is over 1 hundred million tons and reaches 10,800 million tons. The original domestic garbage mixed treatment mode (landfill or incineration) no longer meets the requirements of sustainable development of China and is difficult to be applied to treatment of kitchen waste, so that how to select a reasonable kitchen waste treatment technology to form a reliable, economic and effective kitchen waste disposal mode becomes a problem to be solved urgently in China.

The kitchen waste has the dual attributes of waste and resources, so that on one hand, a large amount of kitchen waste brings risks of environmental pollution and ecological damage; on the other hand, the kitchen waste has higher recycling value than other household waste. Aiming at the treatment of kitchen waste, the most effective treatment mode at present mainly comprises aerobic composting and anaerobic digestion. The compost is a simple, mature, economic and reliable organic waste treatment means, and has been fully demonstrated and widely applied at home and abroad. The composting treatment of the kitchen waste fully utilizes the property of resource property of the kitchen waste, not only can realize the harmless treatment of the kitchen waste, but also can recycle the compost finished product as organic fertilizer or soil conditioner, really realizes the resource treatment of the kitchen waste, and meets the requirement of sustainable development in China.

In the traditional composting process, sawdust serving as an auxiliary material is mixed with kitchen waste after being crushed and pulped in a composting reactor according to a certain proportion, aerobic fermentation is carried out, the retention time period is 1-3 months, the treatment efficiency is low, and the quick treatment of the kitchen waste is not facilitated.

Disclosure of Invention

The invention aims to provide a kitchen waste aerobic composting method, application and composting thereof, which solve the problem of long fermentation period in the traditional composting process and can realize stable operation in the composting process.

In addition, the invention also provides application of the aerobic composting method and compost produced by the aerobic composting method.

The invention is realized by the following technical scheme:

a kitchen waste aerobic composting method takes kitchen waste mature compost as an aerobic composting strain, takes kitchen waste prepared by auxiliary materials and water as a raw material, mixes the aerobic composting strain and the raw material, and adopts a semi-continuous feeding mode to carry out aerobic fermentation so as to realize long-term composting treatment.

The aerobic composting method adopts mature kitchen garbage compost as aerobic composting strains, and does not need to additionally add exogenous strains.

According to the invention, the auxiliary materials are adopted to prepare the kitchen waste, then the mature kitchen waste compost is used as an aerobic compost strain for aerobic fermentation, and a semi-continuous feeding mode is adopted, so that the kitchen waste with the same weight is treated, the treatment time required by the invention is obviously reduced, and the treatment efficiency of the kitchen waste is improved.

Take 100kg of kitchen garbage as an example:

by adopting the traditional composting method, kitchen garbage is added into a composting reactor after being mixed with auxiliary materials and water, and aerobic fermentation is directly carried out, which needs 30-90 days.

By adopting the method, kitchen waste (consistent with the amount of traditional compost) is added with auxiliary materials and water to prepare 100kg of material, then 10kg of the prepared material and aerobic compost strains are added into a compost reactor in proportion to react for 1-2 days, part of the fermented material (the material is taken out to be less than 10kg under the condition that the material in the compost reactor is kept constant due to degradation) is taken out, then 10kg of the prepared material is added into the compost reactor, so that the mass ratio of the prepared material to the rest material (product compost) in the compost reactor is the same as the ratio of the prepared material to the aerobic compost strains at the beginning until the material completely reacts, and the retention time is 10-20 days.

Further, the mature compost of kitchen waste comprises initial compost used for composting first feeding and product compost used for feeding during long-term operation of composting.

Further, the method comprises the following steps:

s1, preparing original compost;

s2, preparing raw materials: adding auxiliary materials into the kitchen waste to obtain a mixture, and adding water to adjust the water content of the mixture to 55-60%;

s3, long-term composting: and (3) mixing the original compost prepared in the step (S1) with the raw materials obtained in the step (S2), adding water to regulate the water content of the mixture to 55-60%, ventilating in a closed environment, carrying out aerobic fermentation, feeding the compost once every 1-2 days in the composting process, using the product compost generated by the aerobic fermentation of the previous batch for the aerobic compost strain of the aerobic fermentation of the next batch during feeding, and controlling the water content of the mixture to 55-60% after feeding.

The moisture content of 55-60% is generally regarded as the ideal moisture content of the compost, which not only ensures the moisture required by the biotransformation process, but also has good air permeability, and tests prove that (examples): the water content is controlled to be 55-60% in the fermentation process, which is beneficial to improving the germination index of compost seeds.

Further, in step S1, the preparation process of the raw compost is as follows:

mixing the auxiliary materials with the kitchen waste after crushing and pulping, adjusting the water content of the initial raw material to 55-60%, ventilating in a closed environment, and performing aerobic fermentation to obtain the original compost.

Further, the aerobic fermentation process comprises the following steps:

after the composting begins, gradually raising the temperature of the initial raw materials to 55-60 ℃, heating and maintaining the temperature at 55-60 ℃ for 3-4 days, and ending the composting process when the temperature is reduced to 35 ℃ and maintained at the temperature for 55-60 days.

Furthermore, the auxiliary materials comprise wood chips and crop straws.

The crop stalks include straw stalks, corn stalks and sorghum stalks.

Further, the weight ratio of the raw materials to the aerobic composting strain is less than 1: 4.

Theoretically, the smaller the weight ratio of the raw material to the aerobic compost strain is, the more favorable the stable operation of the aerobic fermentation process is, but from the aspect of treatment efficiency, the larger the weight ratio of the raw material to the aerobic compost strain is, the more favorable the treatment efficiency is, and therefore, the weight ratio of the raw material to the aerobic compost strain (i.e. the amount of each supplement) needs to comprehensively consider the treatment efficiency and the operation stability.

The applicant finds through experiments that the operation stability is poor when the weight ratio of the raw material to the aerobic composting bacterial strain is equal to 1:4 and 3:7, and the operation stability is good when the weight ratio of the raw material to the aerobic composting bacterial strain is equal to 1:9 (less than 1: 4).

Furthermore, the temperature of aerobic fermentation is 55-60 ℃.

The application of the kitchen waste aerobic composting method in the on-site chemical treatment of the kitchen waste.

At present, the development of kitchen waste disposal mainly focuses on big cities with gathered population, so that a centralized kitchen waste disposal idea is mostly adopted, and the research on the local kitchen waste disposal is less. However, since there are many provinces, cities, counties and counties in China, the kitchen waste yield in each region is different due to the difference of factors such as population scale, economic level, climate conditions and the like, for the regions such as urban-rural villages, urban-rural combination and the like in China, the kitchen waste yield is small and relatively dispersed, and the centralized disposal of the kitchen waste is faced with the problems of low collection and transportation efficiency, high operation cost, secondary pollution and the like. The idea of distributed on-site disposal of kitchen waste can effectively solve the problem and reduce the source of the kitchen waste.

The kitchen waste aerobic composting method can be realized by a composting reactor, the kitchen waste can be treated in situ by adopting the composting reactor, and the composting reactor can adopt a device disclosed in the patent with the application number of 201620017639.5.

201620017639.5 patent discloses a device includes compost room, heat preservation shell and controller, the compost room sets up inside the heat preservation shell, is equipped with the heat band on the compost outdoor wall, and the compost indoor portion is close to the bottom position and is equipped with porous supporting baseplate, porous supporting baseplate forms a cavity with compost room bottom, the cavity passes through admission line and outside intercommunication, the admission line is located the outside one end of heat preservation shell and is connected with gas flowmeter and solenoid valve, the compost roof portion is equipped with the pipeline of giving vent to anger, the pipeline of giving vent to anger is located the outside one end of heat preservation shell and is connected with the absorption bottle, the indoor portion of compost still is equipped with temperature sensor, heat band, temperature sensor, gas flowmeter and solenoid valve are connected with the controller electricity.

The device has the advantages of simple structure and easy maintenance.

The compost prepared by the kitchen waste aerobic composting method can be recycled as organic fertilizer or soil conditioner, so that the resource treatment of the kitchen waste is realized.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. aiming at the current situation of kitchen waste generation in China, the invention develops an efficient and stable quick aerobic composting treatment method for the kitchen waste, realizes the harmlessness, reduction and reclamation of the kitchen waste, and has short fermentation period (10-20 days).

2. The kitchen waste generated by treatment every 1-2 days (semi-continuous operation) is adopted, the current situation that the kitchen waste is generated every day (the kitchen waste is short in storage time and prevented from being corrupted) is met, and the operation is convenient.

3. The composting process of the invention lasts at high temperature (about 60 ℃), and the hygienization effect is good.

4. The reactor is adopted for composting, odor generated in the composting process is effectively prevented from being discharged inorganically, the reactor is particularly suitable for distributed on-site treatment of kitchen garbage, and the reactor is simple in equipment and easy to maintain.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a schematic diagram showing the change of moisture and pH of materials in different stages of composting;

FIG. 2 is a schematic diagram showing the temperature variation of compost and the ambient temperature at different stages;

FIG. 3 is a schematic diagram showing the variation of organic acid concentration and soluble organic carbon (DOC) in different stages of composting process;

FIG. 4 is a diagram showing the change of germination index and conductivity of seeds during different stages of composting.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.

Example 1:

preparation of raw compost (i.e. traditional composting process):

selecting sawdust as an auxiliary material to be mixed with kitchen garbage after crushing and pulping according to a certain proportion, adjusting the water content of the initial raw material to be about 60%, uniformly mixing, weighing and then loading into a composting reactor. Wherein the mass ratio of the kitchen garbage to the wood chips is 3.9: 1.1. Controlling the ventilation quantity of the reactor to be 0.5L/min after composting is started, heating to 60 ℃ at the heating rate of 0.8 ℃/h (after composting is started, the temperature of the compost is increased because organic matters are degraded and generate heat, when the heating rate of the compost is more than or equal to 0.8 ℃/h, the compost is not heated), maintaining the external temperature for 60 ℃ for three days, stopping heating, and maintaining the temperature until the composting process is finished (60 days) after the temperature is reduced to 35 ℃. At the end of 60 days composting the material was used as mature compost strain. The germination index of the mature compost seeds is 60 percent, and the concentration of the organic acid is reduced to 200 mg/kg^-1-TS, concentration of soluble DOC 5,573.1mg kg-1-TS, EC 2.40mS cm^-1。

Example 2:

an aerobic composting method of kitchen garbage comprises the following steps:

s1, taking the original compost prepared in the example 1 as mature compost of kitchen waste, adding the compost into a compost reactor as aerobic compost strain of the kitchen waste, wherein the compost reactor adopts a device in the patent with the application number of 201620017639.5;

s2, preparing raw materials: adding sawdust (or crop stalks such as straw stalks, corn stalks, sorghum stalks and the like) into the kitchen waste to obtain a mixture, and adding tap water to regulate the water content of the mixture to be 55-60%;

s3, long-term composting: mixing the raw compost prepared in the step S1 and the raw material obtained in the step S2 in a composting reactor (the weight ratio of the raw material to aerobic compost strains is 1:9, namely the feeding amount is 10%), adding water to regulate the water content of the mixture to be 55-60%, covering the compost reactor, controlling the temperature of the composting reactor to be 55-60 ℃, ventilating, and carrying out aerobic fermentation:

the composting process runs for a long time: after 1-2 days, pouring out the compost residues in the step S3 as strains of the next batch, taking out partial materials (keeping the quality of aerobic compost strains unchanged), adding the raw materials prepared in the step S2, fully mixing to keep the feeding amount at 10%, and composting again. This operation is repeated during long runs.

Comparative example 1:

this comparative example is based on example 2, differing from example 2 in that:

at step S3, the moisture in the compost reactor is not adjusted. That is, the moisture content of the raw material fed into the composting reactor is adjusted to 55-60% each time, so that the moisture content of the mixture in the composting reactor is maintained at about 40%.

Comparative example 2:

the feeding amount is increased from 10 percent to 20 percent, namely, the weight ratio of the raw materials to the aerobic compost strains is 2:8 during each feeding.

Comparative example 3:

the feeding amount is increased from 10 percent to 30 percent, namely, the weight ratio of the raw materials to the aerobic compost strains is 3:7 during each feeding.

For the purpose of comparing the fermentation effects of example 2, comparative example 1 to comparative example 3, the following tests were carried out:

the kitchen waste was composted by the fermentation process described in comparative example 1 after 23 days (transition phase), then composted for 25 days (feed 10% phase) according to the fermentation process described in example 2, then composted for 17 days (feed 20% phase) according to the fermentation process described in comparative example 2, and composted for 15 days (feed 30% phase) according to the fermentation process described in comparative example 3.

The data for the transition phase, feed 10% phase, feed 20% phase and feed 30% phase were monitored separately and the results are shown in fig. 1-4:

in the transition stage, only adjusting the moisture content of the kitchen garbage to be about 55-60% (in the transition stage, only adjusting the moisture content of the raw material entering the composting reactor to be 55-60% each time), and at the moment, sampling is carried out before the materials in the composting reactor are supplemented, and the moisture content of the sample is maintained to be about 40%; and in the 10% feeding stage, tap water is added during each feeding, the moisture content of the mixture of the kitchen waste and the mature compost strains is adjusted to 55-60% (namely the 10% feeding stage is used for adjusting the moisture content of the raw materials and the fermentation residues in the compost reactor to 55-60%), so that the sampling is carried out before the materials in the compost reactor are fed, and the moisture content of the sample is maintained at 55-60%. At the moment, the temperature of the two stages is kept stable at about 60 ℃, the pH keeping temperature is about 8.0, no organic acids (VFAs) are left in the reactor, and the soluble organic carbon (DOC) is kept at a lower stable level, which indicates that the two stages can keep stable fermentation. However, as can be seen from the compost seed germination index, the seed germination index at the transition stage is about 50%, and the conductivity of the sample at the 10% feeding stage is about 70%, and the conductivity at the transition stage and the 10% feeding stage are respectively 3.5mS/cm and 2.5mS/cm, and it can be seen that the fermentation effect at the 10% feeding stage for adjusting the moisture of the mixture to be about 60% is better.

However, despite adjusting the mixture moisture in the composting reactor to 55-60%, after increasing the feed ratio from 10% to 20% or 30% (reference to the 20% feed stage and the 30% feed stage), the semi-continuous composting process does not remain stable, as evidenced by increased organic acid residue, soluble organic carbon, and a significant decrease in the seed germination index.

The water extract of the compost sample is used for analyzing germination index, organic acid concentration, soluble DOC and conductivity, and the preparation process of the water extract is as follows: taking compost and a certain volume of ultrapure water (1:10, m/V, compost/ultrapure water), horizontally shaking for 2h at 30 ℃, centrifuging the suspended matters for 10min at 10000r/min, and obtaining supernatant after filtering with a 0.45-micron filter membrane, namely the water extract. The organic acid concentration and the soluble DOC concentration in the extract were measured by liquid chromatography (SCL-10A VP, Shimadzu, Japan) and TOC analyzer (TOC-VE, Shimadzu, Japan). The electrical conductivity was measured with a conductivity meter (SG3, mettler toledo, usa). The data for each index are reported as the average of the measurements taken on 3 samples taken at each stack turnover.

Seed germination test: a piece of filter paper (Whatman #2) with a diameter of about 9cm was placed in a sterilized 9cm petri dish, 10 cress seeds (Lepidium sativum L.) were uniformly placed, 8.0mL of water extract or ultrapure water (control) was pipetted into the petri dish, and each sample was repeated 3 times, and incubated in a 20 ℃ incubator for 48 hours in the dark. The germination index is determined by counting the number of germinated seeds and determining the root length, and calculating by the following equation:

index of germination of seeds

From the comparison of the data above, it can be seen that:

1) according to the invention, the kitchen waste mature compost and the kitchen waste blended materials are mixed according to a certain proportion, and then aerobic fermentation is carried out in a semi-continuous feeding mode, so that the kitchen waste treatment efficiency can be improved.

2) In the transition stage, only the water content of the raw materials entering the composting bin each time is adjusted to be 55-60%, so that the water content of the mixture is maintained at about 40%; and the 10% feeding stage is to adjust the moisture of the raw materials and the fermentation residues to 55-60% (as shown in the figure), namely, the moisture of the materials in the reactor is kept to be 55-60% all the time, and the moisture in the composting reactor in the 10% feeding stage is higher than that in the transition stage, so that the result shows that the material decomposition degree in the 10% stage is better (such as better germination index), namely, the moisture of the materials in the reactor is kept to be 55-60% all the time, and the aerobic fermentation of the kitchen waste raw materials is facilitated.

3) The mass ratio of the raw materials to the fermentation residues (product compost) in the composting reactor is optimally controlled to be less than 1:4, and when the mass ratio of the raw materials to the fermentation residues in the composting reactor is equal to 1:4, the semi-continuous composting process cannot be kept stable.

Therefore, the invention reasonably uses the kitchen waste mature compost as the aerobic compost strain, and reasonably controls the weight ratio of the raw materials to the aerobic compost strain, thereby not only realizing stable fermentation, but also controlling the organic acid residue, the soluble organic carbon to be lower or even no residue, and controlling the seed germination index to be higher.

The compost prepared by the kitchen waste aerobic composting method can be recycled as organic fertilizer or soil conditioner, and the resource treatment of the kitchen waste is realized.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The kitchen waste aerobic composting method is characterized in that mature kitchen waste compost is used as an aerobic composting strain, kitchen waste prepared from auxiliary materials and water is used as a raw material, the aerobic composting strain and the raw material are mixed, and a semi-continuous feeding mode is adopted for aerobic fermentation to realize long-term composting.

2. The aerobic composting method of kitchen waste as claimed in claim 1, wherein the mature compost of kitchen waste comprises initial compost used for composting first charge and product compost used for charging during long-term operation of composting.

3. The aerobic composting method of kitchen waste as claimed in claim 2, characterized in that it comprises the following steps:

s1, preparing original compost;

4. The aerobic composting process of kitchen waste as claimed in claim 3, wherein in step S1, the raw compost is prepared as follows:

5. The aerobic composting method of kitchen waste as claimed in claim 4, characterized in that the aerobic fermentation process is:

after the composting begins, the initial raw materials are heated to 55-60 ℃, the temperature is maintained to be 55-60 ℃ for 3-4 days, the temperature is reduced to 35 ℃, the temperature is maintained for 55-60 days, and the composting process is finished.

6. The aerobic composting method of kitchen waste as claimed in claim 1 or 3, characterized in that the auxiliary material comprises wood chips and crop straw.

7. The aerobic composting method of kitchen waste as claimed in claim 1 or 3, characterized in that the weight ratio of the raw material and the aerobic composting strain is less than 1: 4.

8. The aerobic composting method of kitchen waste as claimed in claim 1 or 3, characterized in that the temperature of the aerobic fermentation is 55-60 ℃.

9. Use of the aerobic composting method of kitchen waste as claimed in any of the claims 1-8 for the in-situ disposal of kitchen waste.

10. Compost produced by the aerobic composting process of kitchen waste according to any of claims 1-8.