KR100520457B1 - Method for composting foodstuff waste by aerobic fermentation and system using the same - Google Patents

Abstract

      The present invention relates to a composting method and system of food waste by aerobic fermentation,

      In the method according to the present invention, in the composting method of food waste using an aerobic fermentation tank having an aeration means for supplying air through a lower diffuser and an agitating means provided thereon, an upstream into which food waste having a relatively high moisture content is introduced. The area adjacent to the input section is blown with blowing pressure of 4,000 ~ 10,000mmAq to increase the air transfer rate, and below the middle stream, it adopts the dualization blowing method consisting of blowing with blowing pressure of 1,000 ~ 4,000mmAq, and conveys a part of mature dry compost. There is provided an aerobic fermentation method and a system using the same, characterized in that by adopting a conveying method by mixing with food waste introduced by

      The method and system of the present invention are capable of efficient aerobic fermentation, so that there is little odor generation and no leachate generation problems, and by adopting a transfer method of mature dry compost, a water content control material that requires additional cost is purchased. In addition, it is possible to shorten the induction period for the growth of microorganisms and is suitable for economical and large-scale processing that can shorten the fermentation period.

Description

      METHODS FOR COMPOSTING FOODSTUFF WASTE BY AEROBIC FERMENTATION AND SYSTEM USING THE SAME

      The present invention relates to a composting method and system of food waste by aerobic fermentation, and more particularly, less odor generated by efficient aerobic fermentation, there is no problem of leachate generation, and external supply of a separate water content control material (調節 材) The present invention relates to a food waste composting method and a composting system using the same, which is possible to shorten the fermentation period and have a high economical efficiency.

      It is known that the annual amount of garbage generated in Korea is about 20 million tons, of which food waste accounts for about 25.4%, about 0.25kg of food waste per person per day. Only about 33% of this waste is recycled, and the rest is disposed of by landfill or incineration, which translates into 8 trillion won in total, and 10 trillion won in total, including landfill costs, environmental recovery costs, and landfill maintenance costs. It is estimated to exceed.

        Food wastes spilled about 20,000 tons per day cause secondary environmental pollution and odors caused by leachate if left untreated, and its disposal is a very important environmental issue. It is becoming.

       Representative methods of treating food waste include a pyrolysis method of incineration in an incinerator, a method of embedding at a predetermined site, and a method of recycling by feed or composting.

       However, in the case of pyrolysis of incineration of food waste, the use of auxiliary fuel and incineration ash for incineration is considerable depending on the characteristics of food waste of more than 80% of water content, and incineration is expensive and incineration is required. As it causes air pollution and odors caused by environmental harmful substances such as dioxin and exhaust gas including carbon dioxide, it is accompanied by another serious environmental problem. In recent years, it has become one of the major causes of civil complaints. have.

       In the case of the landfill method, as a result of anaerobic fermentation, severe odors such as nitrogen and sulfur compounds are generated, there is a fear of explosion by methane, etc., and it becomes a breeding place of pests, and leachate is generated from landfill food waste. Drinking water sources such as soil or groundwater are likely to be contaminated, and in order to reclaim, landfills must be secured in a nearby area, which is not a desirable method in an environment such as Korea where the land is narrow and the population density is high.

       Therefore, in order to solve the above-mentioned problems in the pyrolysis and landfilling methods, the recycling of food waste into feed or compost is of interest, and this method minimizes environmental pollution caused by food waste. In addition, it is possible to solve the secondary pollution problem caused by acidification of farmland or the establishment of waste disposal plant due to excessive use of various chemical fertilizers, and it is recognized as the most desirable method in terms of resource recycling.

       However, in the case of feed for ruminants, the recycling method is strictly regulated due to disease problems not only for livestock, but also for humans, and regulations for other livestock are being tightened. Because of this wide variety, it is difficult to standardize nutritional ingredients as a feed, so its use is quite limited, and most livestock farmers have neglected it even in the range of use.

       Therefore, at present, the most practical and most applicable is the composting method, which can be divided into aerobic fermentation method and anaerobic fermentation method.

       First, in the composting method by anaerobic fermentation, since organic substances in food waste are used as a substrate of anaerobic microorganisms and finally recycled to an energy source such as methane gas, the composting method shows a higher decomposition rate of organic matter than aerobic fermentation. As long as the fermentation period is long, most anaerobic methane-producing bacteria show optimal growth at neutral pH at medium temperature, so food wastes with a pH of 4-5 should be calibrated before input. Methane gas, which is very sensitive to this external environment (especially the presence of oxygen as a poison to the microorganisms) and the end product, is highly explosive and requires high technology for its operation, maintenance and safety management operations. There is a problem that the initial investment and maintenance of the facility will have to cost a considerable amount.

       On the other hand, in the conventional composting method by aerobic fermentation to adjust the water content by adding a moisture control material such as sawdust or chaff to food waste, and then stirring or blowing in consideration of the characteristics of the microorganisms that require oxygen for growth. Oxygen is supplied, and fermentation proceeds at a temperature of 45-80 ° C., which is a relatively high temperature growth condition, generally 55-60 ° C., by heat of fermentation (substrate oxidation heat), and shows good characteristics in maturity and water content. .

       The composting method by aerobic fermentation can be roughly classified into a low speed fermentation method and a high speed fermentation method.

       The fast fermentation method usually uses a batch type fermenter with a stirrer or a self-rotating, forced aeration means and temperature control means, which has a relatively short fermentation period compared to the slow fermentation method. Although there is an advantage, such a device requires a lot of energy costs and is suitable for small-scale fermentation, so that its use in compost, etc., in which its added value is relatively low, is very difficult in reality.

       Although slow fermentation methods exist, various fermentation structures exist, but a typical method is to install an air supply pipe at the bottom, cover rice hulls on top, and stir several times a day. Although it has a low cost and is suitable for mass production, if the oxygen supply is not localized smoothly, it can not be tolerated by the generation of ammonia gas and sulfur dioxide gas by the growth of facultative anaerobics or anaerobics. Leachate problems due to odor and anaerobic fermentation may occur, and the fermentation takes relatively long fermentation periods of 40 days to 3 months, and a lot of sawdust or chaff as a moisture control agent. Supply and demand are also not constant throughout the year, especially for sawdust which is poorly fermented (cellulose and lignin Since the compost produced by fermenting food waste is naturally decomposed after a period of time, it is absorbed into the soil smoothly, while sawdust, which is not easily decomposed, remains on the soil surface. Farmers have the problem of avoiding the use of compost, and in order to avoid this problem, some low-speed or high-speed fermentation process is to separate the compost and sawdust again, but the new problem that the process is cumbersome, energy cost and time-consuming Is causing. In particular, the conventional composting facilities by aerobic fermentation adopt a method of uniformly supplying a constant pressure of air throughout the fermentation tank, so that it does not adequately cope with the change of substances occurring in the upstream, middle, and downstream portions of the fermentation tank. The reality is that the efficiency is not satisfactory enough.

      Therefore, it is possible to minimize the damage of primary environmental pollution caused by food waste not only in the industry but also in the country, and there is no secondary environmental pollution problem in the treatment process, and it has high high maturity, which is desirable in preventing acidification of farmland and recycling of resources. Economical composting methods and systems are desired.

      Accordingly, a first object of the present invention is to provide a composting method of food waste suitable for mass production, which can effectively shorten the composting period at low cost.

      The second object of the present invention is a cost-efficient composting method of economical food waste, which can improve the quality of the compost produced and simplify the process by eliminating the external procurement of moisture control materials such as sawdust or rice husk, which is a problem in supply and demand. It is to provide.

      A third object of the present invention is to provide a method for composting environmentally friendly food waste, which does not have a problem of leachate or dehydration by effectively suppressing anaerobic fermentation while minimizing odor generation by efficient aerobic fermentation. will be.

      A fourth object of the present invention is to provide a composting method of food waste which has high maturity and can provide high quality compost with a minimum water content.

      A fifth object of the present invention is to provide an efficient composting system of low power requirement capable of smoothly achieving the method of the present invention according to the first to fourth objects described above.

      First, prior to the description of the present invention, the biological reaction mechanism (Mechanism) and conditions that can occur in the composting process using food wastes briefly look as follows.

When organic wastes with high moisture content, such as food waste, are released into the atmosphere, carbohydrates and proteins, which are easy to use microorganisms, are decomposed into simple inorganic substances such as CO ₂ and H ₂ O by primary aerobic microorganisms.

* Organic Waste + Oxygen (O ₂ ) --- (Aerobic Microorganisms)-> Microorganisms + Metabolites + CO ₂ + H ₂ 0

In the natural state without artificial air supply, when oxygen dissolved amount is reduced by the growth of aerobic microorganisms, anaerobic microorganisms proliferate and organic matters are simple minerals such as CO ₂ , CH ₄ , NH ₃ , H ₂ S and volatile amines. As it decomposes into low molecular weight organic substances such as volatile alcohols, volatile organic acids and mercaptans, severe odors are generated. Therefore, the composting process needs to be supplied with sufficient oxygen to operate to suppress this reaction as much as possible. There is.

* Organic waste --- (anaerobic microorganisms)-> microorganisms + metabolites + CO ₂ + H ₂ 0 + CH ₄ + NH ₃ + H ₂ S

+ Volatile amines + volatile alcohols + volatile organic acids + mercaptans

      In the composting process, when the above-mentioned aerobic microorganisms are oxidized, the temperature rises due to the heat of reaction, and the proliferation of thermophilic bacteria is active. Therefore, the larvae and eggs of the pathogenic microorganisms and pests that are weak to heat are killed. do.

* Organic waste + oxygen (O ₂ ) --- (thermophilic microorganism)-> microorganism + metabolite + CO ₂ + H ₂ 0

      This reaction is unlikely to occur for organic wastes with high water content or under anaerobic conditions.

Subsequently, when the substrate of the thermophilic microorganism decreases, proliferation of actinomycetes, fungi, yeasts, and mesophilic microorganisms of the general soil occurs, and the polyphenolic compound is produced as a metabolite. Hydrogen peroxide (H ₂ O ₂ ) is produced as it is oxidized to quinone compound by the catalytic reaction of polyphenoloxidase) and hydrogen peroxide reacts with microbial enzyme to produce oxidase. The quinone compound undergoes a polycondensation reaction with lignin, cellulose, tannin, and the like, which are difficult to be degraded by microorganisms, and are then matured by being converted into a non-volatile stable humic substance.

* Organic waste + oxygen (O ₂ ) --- (corrosive microorganisms)-> microorganisms + polyphenolic metabolites

+ Other metabolites + CO ₂ + H ₂ 0

* Polyphenolic Metabolite + Oxygen (O ₂ ) --- (polyphenoloxidase)-> Quinone Compound + H ₂ 0 ₂

* H ₂ 0 ₂ + enzyme ----> oxidase

* Quinone Compound + Lignin, Cellulose, Tannin-(Polycondensation Reaction)-> Corrosive Precursor + H _{2 0} -----> Corrosive

      Corrosive microorganisms include actinomycetes, Bacillus mycoides, bacillus, Sorangium cellulosum, Myxobacteria, and fungi (Aspergillus niger, Penicillium sp). , Mucor sp., Fusarium sp.), And these microorganisms are known as corrosive microorganisms that convert polyorganic substances from their metabolites to convert organic substances into corrosive substances.

      In addition, in order for the corrosion reaction to proceed smoothly, the reaction by the oxidase polyphenol oxidase must be smooth.

      Microorganisms such as filamentous fungus and Pseudomonas sp. Ingest the corroded corrosive as a substrate to promote growth such as vitamins and auxins, which are physiologically active substances useful for plant growth among metabolites. Excrete the substance.

      The caustic finally reacts with the active minerals (water soluble minerals) in the coarse minerals of the soil, and the corrosive soils (colloidal soil) in the form of colloidal micelles of chelate caustic mineral complexes. Becomes

      Therefore, in order to produce high quality compost from organic waste such as food waste, corrosive microorganisms (such as actinomycetes, Bacillus mycoides, Sorangium cellulosum, Myxobacteria), which convert organic substances into stable corrosive substances, as mentioned in the biological reaction mechanisms described above. , Aspergillus niger, Penicillium sp., Mucor sp., Fusarium sp.…) And useful soil microorganisms (Pseudomonas sp., Interstitial fungi, rhizomes, filamentous fungi) In order to produce high quality compost, the composting treatment should be carried out while maintaining the optimal growth environment conditions such as), molds, yeasts (Torura sp., Mycotorula sp.,) And nitrogen-fixed fungi.

      In conclusion, the most important factors in the composting method by aerobic fermentation of food waste are the proper control of moisture content of food waste in the pretreatment stage, the proper air supply and the proper agitation in the fermentation stage, and especially the aerobic fermentation process. The smooth supply of air is one of the most essential and essential operating conditions for the purpose of supplying sufficient oxygen into the reaction substrate, reducing the water content by evaporation of water, and controlling the temperature.

      The composting method and system of food waste by aerobic fermentation according to the present invention is essentially different from the conventional composting method and system

      First, since the collected food waste has a water content of 80-87%, which is unsuitable for the growth of aerobic fermentation microorganisms, while it is a good condition for the growth of anaerobic microorganisms, the supply of oxygen from the initial stage of fermentation or the upstream portion of the fermenter can be reduced. It is performed more sufficiently than the middle part of the stage or fermenter to drastically reduce the initial moisture content, and at the same time to create conditions suitable for aerobic fermentation,

      Second, the oxygen supply at the boil stage of the fermentation or the downstream outlet portion of the fermentation tank, which is the ripening stage of the fermentation, is performed more sufficiently than the middle stage of fermentation or the upstream portion of the fermentation tank, thereby further reducing water content to provide high quality compost. At the same time, the moisture content and the porosity of the high water content food waste introduced by returning a predetermined amount of the thus-dried ripe compost to the initial introduction stage or upstream of the fermentation tank are aerobic without the addition of a separate moisture control material. Reduce to suit fermentation,

      Fourth, since a large amount of composting strains are spawned by the return of the mature compost, it is possible to effectively shorten the fermentation period by effectively shortening the lag phase, which is an environmental adaptation period of the initial microorganisms.

      Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

      1 is a block diagram showing a composting method according to a preferred embodiment of the present invention, the method according to the invention is a food waste sorting / shredding step as an optional step, the mixing step of food waste and mature dry compost, and aerobic It consists of a fermentation step and a mature dry compost shipping and conveying step.

      On the other hand, Figure 2 is a partially omitted schematic plan view showing a composting system according to a preferred embodiment of the present invention, the composting system according to the present invention is an aerobic fermentation tank (1), the roots installed on at least one side of the aerobic fermentation tank (1) First aeration means such as a blower 22 and a compressor 21, a branch air line 25a serving as a plurality of diffusers provided upstream and downstream with the main air line 25 communicating therewith, Second aeration means such as a turbo shock 23 provided on at least one side of the aerobic fermentation tank 1, a main air line 24 communicating therewith, and a branch air line 24a as a plurality of diffusers provided in the midstream; , Agitation means (not shown) that is movable along a pair of rails provided above the aerobic fermentation tank 1. The spacing between the main air lines 25 and 24 and the spacing between the main air lines 24 and 24 across the aerobic fermentation tank 1 is about 1 to 3 m, preferably about 1.5 to 2 m, but It is not restrictive in this invention. On the other hand, the distance between the branch air lines 24a and 24a and the branch air lines 25a and 25a is 2 to 50 cm, preferably about 5 to 30 cm, but this is not limitative in the present invention. .

      In addition, if necessary, an odor removing air filter (not shown) may be provided above the aerobic fermentation tank 1, and heating means (not shown) for use in winter may be provided in an area adjacent to the food waste introduction portion. It is also possible to install a forced air blowing means to avoid excessive temperature rise by thermophilic bacteria above, and to install a conveyor (not shown) for the automatic transfer of mature dry compost, all of which are optional in the present invention. It is only.

      For convenience of description, a composting method by aerobic fermentation and a system using the same according to the present invention shown in FIGS. 1 and 2 will be described together.

      First, as an optional step and apparatus in the present invention, it is also possible to perform a step of removing impurities such as vinyl present in the collected food waste using a sorter, but if the collected food waste is thoroughly separated and collected Steps and devices may be omitted.

      Subsequently, as an optional step and apparatus in the present invention, it is preferable to perform cutting and crushing of food waste using a crusher.

      The particle size of the food wastes crushed by the crusher acts as an important factor in aerobic fermentation, that is, when the surface area of the food waste particles is increased by cutting and crushing, the surface area of contact with the microorganisms is increased to promote the growth of microorganisms. Increasing the rate of decomposition of food waste as a substrate, and if the particle size is too small, the porosity is reduced, which interferes with the circulation of air in the aerobic fermenter, resulting in a decrease in the amount of oxygen available to aerobic microorganisms, thereby increasing the activity and activity of microorganisms Is reduced. In addition, the amount of outflow of leachate is reduced in the food waste which has undergone the crushing step.

      As such, since the particle size of the food waste may be a factor affecting the microbial utilization of carbon and nitrogen contained therein, in the present invention, the particle size of the food waste is not limited but crushed to about 5 cm or less in diameter, Preferably about 3 cm or less.

      The food waste which may be passed through the sorting / crushing step is mixed with the mature dry compost discharged from the aerobic fermentation tank 1 at a predetermined ratio before being introduced into the aerobic fermentation tank 1.

      The aerobic fermentation tank 1 in the present invention is not particularly limited as long as it is an aerobic fermentation tank for mass production. Preferably, the aerobic fermentation tank 1 is a fermentation tank that is capable of continuous process processing and has relatively easy operating conditions.

      In general, food waste has a water content of 80 to 87%, a C / N ratio of 13 to 17, and a pH of 4 to 5, and by itself has environmental conditions unsuitable for aerobic fermentation, so it is suitable for aerobic fermentation, that is, water content of 50 to 75 In order to control and control by%, C / N ratio 20-30, and pH6-8, in this invention, the mature dry compost about 13-35% of water content discharged | emitted from the aerobic fermentation tank 1 is conveyed and mixed.

      Conventionally, sawdust, which is most widely used as a moisture control agent, is easily composed of moisture, but has a C / N ratio close to 100, and since sawdust itself is made of wood, it is mainly composed of components that are not suitable for aerobic fermentation such as cellulose, lignin, and tannin. It is worth noting that complete fermentation is almost impossible and fermentation of food waste components takes a relatively long time and the biggest problem is high cost.

      The mixing ratio of the food waste and the mature dry compost in the mixing step is based on various parameters such as the water content, the type, the moisture content of the mature dry compost, the type of fermentation tank, the operating conditions of the fermentation tank, the temperature conditions, the aeration conditions, and the like. Although it can be varied in various ranges, in the present invention, 50 to 150% by volume (ie, 1: 0.5 to 1.5 times volume ratio) of mature dry compost per unit volume of food waste, preferably 70 to 120% (1 : 0.7 ~ 1.2 times volume ratio) Return to volume.

      As described above, the food waste mixed with the mature dry compost is introduced into the aerobic composting tank, that is, the aerobic fermentation tank 1, and moves, for example, a pair of rails (not shown) installed on the upper wall and the rails. While stirring the fermentation object or the progress with the stirring operation from the upstream to the downstream and an agitator (not shown), which is installed under the aerobic fermentation tank (1) and oxygen in the fermentation target or fermentation progress in the aerobic fermentation tank (1) It is provided with the air supply apparatus which supplies. The basic configuration of the aerobic fermentation tank and the stirrer is known in the art, the stirrer may be any of the escalator or rotary type, and the stirring is performed once or twice a day to perform the inversion of the fermentation progress.

      Food waste put into the aerobic fermentation tank (1) is usually loaded at a height of 1.2m ~ 2m and moved from upstream to downstream with stirring / fermentation, each position between the upstream food waste introduction section and the downstream mature dry compost discharge section In the fermentation process, there is a difference in height fluctuations, water content differences, and density differences (porosity fluctuations) due to the gradual evaporation of organic fermentation and decomposition of organic matter, so that the air is supplied at a uniform pressure uniformly at each position from the lower part of the aerobic fermentation tank 1. In the case of high water content adjacent to the upstream part of the upstream, there is a high possibility that the air transfer rate is significantly lowered, so that effective aerobic fermentation will not occur, and conversely, if the initial air supply is not smooth, Anaerobic fermentation proceeds, resulting in extreme odor and low volatility caused by the formation of sulfur-containing compounds There is a high risk of causing a sharp drop in pH due to the generation of acidic organic acids, which leads to severe inhibition of proliferation and / or activity of aerobic fermentation microorganisms and a failure in composting fermentation itself due to a decrease in temperature. May result.

      Therefore, in the aerobic fermentation tank 1, the control of the microbial growth environment in the region adjacent to the introduction portion of the food waste, in particular, the smooth supply of oxygen and the moisture content control is most important for the smooth fermentation progress in the entire aerobic fermentation tank 1, Fermentation at the introduction is a factor in determining the overall fermentation efficiency.

      The present invention is to solve the above-mentioned problems caused by the large difference in the rate of delivery of the air supplied from the bottom between the food waste introduction portion and the discharge portion of the aerobic fermentation tank (1), air in the aerobic fermentation tank (1) It is possible to dualize the aeration means for supplying the first air supply means and the aerobic fermentation tank (1) which occupies most of the region of the high pressure first aeration means capable of providing a large air transfer rate to the areas adjacent to the upstream and downstream of the food waste introduction unit. To install a second ventilation means capable of supplying sufficient air at a small pressure. Here, the above-mentioned second venting means may also be provided in the region adjacent to the downstream as needed, which is optional for the present invention.

      In this specification, only the example which dualized the above-mentioned ventilation means is described, but it is also within the scope of the present invention to diversify, which is obvious to those skilled in the art.

      In the case of low pressure, fermentation may be anaerobic due to insufficient air transfer rate in the region adjacent to the introduction of the aerobic fermenter (1) in the case of low pressure, while in the case of high pressure, due to the temperature decrease by rapid drying and cooling Since fermentation may be inhibited, it is important to harmonize and optimize the above-mentioned diversification or dualization.

      In the present invention, the region adjacent to the upstream inlet, which occupies 10-30% of the total length of the aerobic fermentation tank 1, is a high-pressure blow (4,000-10,000 mmAq) with a Roots blower to increase the air transfer rate, and in the midstream with a turbo fan or a ring blower. Blowing (1,000 ~ 4,000mmAq) ensures sufficient air transfer rate, and high pressure blowing (4,000 ~ 10,000mmAq) with Roots blower in the area adjacent to the downstream outlet which occupies 10 ~ 20% of the aerobic fermenter (1). By increasing the air transfer rate, the mature compost is smoothly dried.

      By the aerobic fermentation step according to the dualization of the aeration means and conveying, mixing step of the mature dry compost, the present invention is water content of the food waste introduced initially by conveying the mature dry compost and mixing with the food waste introduced initially It is possible to shorten the induction period of microbial growth by inoculating a large amount of composting strains while inoculating a suitable range for aerobic fermentation without adding a separate moisture control material, and in particular, by improving the air supply efficiency upstream of the aerobic fermentation tank (1). Not only can the fermentation proceed rapidly, but also the evaporation of the moisture contained in the high moisture content food waste introduced early has the effect of inducing in full-scale fermentation.

      The introduced food waste is changed into mature compost having a high maturity of water content of approximately 40% when it reaches the end of the aerobic fermentation tank 1, that is, the discharge part, while undergoing a smooth fermentation and after-aging process. In the present invention, as described above, in order to substitute the mature compost as a moisture control material is dried by high-pressure blowing (4,000 ~ 10,000mmAq) with a Roots blower as an additional drying process.

      The final dry compost discharged from the aerobic fermentation tank (1) is dark brown with visual observation. The moisture content is about 13-35% and the total organic-to-nitrogen ratio (OM / N) is 18-28. The completion of is usually completed in 21-35 days, although it can be varied by various parameters such as the type, size, aeration conditions, temperature of the outside air, etc.

      Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1: Preparation of compost by aerobic fermentation according to the present invention

      The collected food waste is removed by using a sorting machine to remove foreign substances such as iron and vinyl in the food waste, and then crushed to a diameter of 3 cm or less, crushed food waste (water content of 85%) and mature dry compost (water content of 32%). Was added into a fermenter (length 70m, height 2m, width 14m) by mixing the mixture in a ratio of 1: 1 in volume ratio, and the mixture was stirred at room temperature (temperature of about 25 ° C.) for 1 day. Aerobic fermentation was carried out with two flips and a gradual transfer.

      The aeration conditions were a high pressure blow (5,000 mmAq) with a Roots blower in the area adjacent to the upstream inlet (25%) of the aerobic fermenter (1) and the area near the outlet (15%) downstream (150 mmAq). 20 cm of branch airline), except for the remaining midstream, was blown (1,500 mmAq) with a turbo fan and the aerobic fermentation was completed in 24 days.

      As a method for determining the maturity of the prepared compost, the amount of carbon dioxide generated using the microbial activity, the water-soluble organic carbon in the composition, the water-soluble carbonyl ratio, the ratio of water-soluble carbon to total organic nitrogen and the amount of carbon dissolved in NaOH, the naked eye The color by, etc. were measured according to a conventional method in the art. At this time, the quality of the composted quality compost is about 120 mg CO2 / kg / hr or less, water-soluble organic carbon 10g / kg or less, water-soluble carbon ratio of 16 or less, water-soluble carbon to total organic nitrogen ratio of 0.70 or less The amount of carbon dissolved in NaOH was determined to be 60 g / kg or less, and it was confirmed that the compost prepared according to the present example satisfies all of the above criteria.

      In addition, the final mature dry compost was reduced by 68.2% of the amount of the original raw material, it was found that the amount of food waste was effectively decomposed.

Comparative Example 1: Preparation of Compost by Conventional Aerobic Fermentation

Ventilation conditions were blown (1,000 mmAq) at a uniform pressure in the upper and lower streams of the fermenter at a uniform pressure, except that the sawdust was added at a volume ratio of 6: 4 to the volume of food waste without mixing the dry and dried compost. It was carried out under the same apparatus and conditions as in Example 1, and the aerobic fermentation was completed in 38 days. The reduction rate of food waste was 32.1%, and the suitability of the fermentation products as compost was examined according to the method and standard of Example 1, and the values were close to the standard values. However, the test results for the fermented products collected on the 24th day of fermentation were found to be insufficient for composting because they were insufficient for all items.

Comparative Example 2: Preparation of Compost by Anaerobic Fermentation

30 tons of collected food wastes were fermented in an anaerobic fermentation plant with only agitation without oxygen supply. The total fermentation period took 4 months. Finally, 21.5 tons were obtained, yielding 71.7% of the original raw material. Reduction of food waste was only 26.3%, and the suitability of the fermentation product as a compost was tested according to the method and standard of Example 1, and it was found that the standard was not met and was not suitable as compost.

      As described above, according to the composting method and a system using the aerobic fermentation of food waste according to the present invention, the dehydration process of the food waste introduced into the fermentation tank is unnecessary, there is no occurrence of leachate and other waste water, such as sawdust, etc. It is not necessary to purchase and use the moisture control material of the product, and it is controlled by the optimum fermentation conditions (water content, C / N ratio, pH, high inoculation of fermentation microorganism as a seed) by mixing with the food waste introduced by returning mature dry compost. By at least dualizing the aeration conditions, the aerobic fermentation at the food waste introduction portion of the fermentation tank can be performed smoothly so that anaerobic fermentation can be effectively suppressed, thereby minimizing the occurrence of odor, and effective throughout the fermentation tank. Aerobic fermentation takes place, drying of mature compost Yirueojim together and, at the same time, is not required by the power and labor for these tasks efficiently and can also be highly economical production of high quality compost high drying manure in a continuous manner.

      1 is a block diagram showing a composting method according to a preferred embodiment of the present invention.

      Figure 2 is a schematic diagram showing the airline of the composting system according to a preferred embodiment of the present invention.

Explanation of symbols on main parts of drawing

1: Aerobic Fermenter 21: Compressor

22: Rootsblower 23: Turbo Soap

24, 25: main line 24a, 25a: branch line

Claims (8)

      In the composting method of food waste by an aerobic fermentation tank provided with aeration means for supplying air through a lower diffuser and an agitating means therein, the region adjacent to an upstream inlet portion where food waste having a relatively high moisture content is introduced is introduced. Air flow rate is increased by blowing at wind pressure of 4,000 ~ 10,000mmAq, and below midstream, it is fermented while applying dualization blowing method which consists of blowing at blowing pressure of 1,000 ~ 4,000mmAq.       Composting of food waste by aerobic fermentation.       Composting food waste by aerobic fermentation consisting of the following steps:       (A) A mixture of food waste having a relatively high moisture content and (C) ripe dry compost with a moisture content of 13 to 35% returned in the shipping and conveying step below in a volume ratio of 1: 0.7 to 1.2. Mixing the food waste and ripe dry compost to adjust the water content of 50 to 75%;       (B) Blowing at a blowing pressure of 4,000 to 10,000 mmAq in the upstream inlet area where food waste with a relatively high moisture content is introduced and in a downstream area adjacent to the mature compost discharge, and blowing at a blowing pressure of 1,000 to 4,000 mmAq in the midstream area. Aerobic fermentation step of fermentation for 21 to 35 days while performing flipping and stirring for gradual transfer once or twice a day; And       (C) Shipment and conveyance of the mature dry compost which ships the mature dry compost which shows black brown, and conveys at least one part to the mixing step of said food waste (A) and mature dry compost.       The composting method of food waste by aerobic fermentation according to claim 1 or 2, further comprising the step of preliminarily carrying out a crushing step of cutting the food waste introduced as a pretreatment step.       The method of claim 2, wherein the region adjacent to the upstream introduction portion occupies 10-30% of the total length of the aerobic fermentation tank, and the region adjacent the downstream discharge portion occupies 10-20% of the total length of the aerobic fermentation tank. A composting method of food waste by aerobic fermentation wherein said middle-class region is the remaining intermediate region.       5. The method of composting food waste by aerobic fermentation according to claim 2 or 4, wherein the ripe dry compost is 13-35% water content and the total organic-to-nitrogen ratio (OM / N) is 18-28. delete       Blowing pressure in communication with the aerobic fermenter and the main air line located in the region adjacent to the upstream inlet portion into which the food waste below the aerobic fermenter is introduced and in the downstream region adjacent to the mature compost discharge part and a plurality of branch air lines as diffusers. Forced blowing with a first blowing means for forcing to ~ 10,000 mmAq and blowing pressure of 1,000 to 4,000 mmAq in communication with a plurality of main air lines and a plurality of branch air lines as diffusers located in the midstream region below the aerobic fermenter. In the composting system of food waste by aerobic fermentation comprising a second ventilation means for Composting system of the food waste by aerobic fermentation further comprising agitating means for the transfer and fermentation gradual transfer is installed to move along the fermentation tank above the aerobic fermentation tank.       8. The composting of food waste by aerobic fermentation according to claim 7, further comprising a sorting and crushing means in front of the aerobic fermenter, and further comprising conveying means and mixing means for conveying the finished compost and mixing with the food waste. system.