JPS5835120B2 - How to treat organic waste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating organic waste, and more particularly to an anaerobic treatment method for efficiently decomposing, digesting, and gasifying organic waste containing cellulose.

In recent years, anaerobic digestion has been gaining importance due to the growing need for processing organic waste and for energy production.

In particular, anaerobic digestion is suitable for processing kitchen waste in municipal waste that contains a large amount of water.

In the conventional method, kitchen waste is mixed with water or sewage sludge to form a slurry and then subjected to anaerobic fermentation, but it is unavoidable that a considerable amount of paper etc. gets mixed in with the kitchen waste in municipal waste. vinegar,
For this reason, (1) the paper in the slurry swells and increases the viscosity of the slurry, making stirring and pumping difficult;
(11) Since the cellulose content is difficult to decompose in anaerobic digestion, the amount of digested sludge discharged after treatment is large, and (Di) the gas yield is small despite the large load. was there.

It has been proposed to use acid or cellulase to eliminate these drawbacks of the conventional technology, saccharify paper and other cellulose content, facilitate transportation of raw material slurry, increase the amount of methane gas generated, and reduce the amount of digested sludge. However, this method requires a reaction tank for saccharification with acid or cellulase in advance, and in some cases, a heat source such as heating is also required.

By the way, the reaction of anaerobic digestion consists of an anaerobic liquefaction reaction in which the organic matter in the raw material to be treated is reduced in molecular weight by the action of a group of anaerobic liquefaction bacteria and decomposed into lower fatty acids, and then the lower fatty acids and lower fatty acids produced by this liquefaction reaction. It consists of a gasification reaction for converting other decomposition products into methane through the action of gasifying bacteria, and by performing these two reactions separately and each reaction under optimal conditions,
A two-step method is known that shortens the conventional treatment period and improves the methane gas yield.

However, this method does not solve the above-mentioned drawbacks caused by cellulose in kitchen waste.

The present inventors have discovered that cellulase can decompose undecomposed cellulose even during an anaerobic liquefaction reaction in which the physiological activity of anaerobic liquefaction bacteria is being expressed, leading to the present invention.

That is, the present invention provides for, when treating organic waste containing cellulose by an anaerobic digestion method in which at least a liquefaction step and a gasification step are performed separately, cellulase is allowed to coexist in the liquefaction step, and the cellulase used at that time is organic waste or its anaerobic digestion sludge, containing cellulose as
A method for treating organic waste characterized by using a culture obtained by culturing cellulase-producing bacteria in a medium containing cellulose or a mixture of the two as a main component, and is suitable for the treatment of organic waste containing cellulose as described above. eliminates the drawbacks of conventional technology,
The purpose of this project is to increase the amount of recovered methane gas generated, reduce the amount of digested sludge, and also make it possible to apply anaerobic digestion to organic waste with a high cellulose content.

The present invention will be explained in detail below.

Organic waste to be treated in the present invention includes conventional surplus activated sludge, kitchen waste, livestock excrement, waste liquid from fermentation factories and food processing factories, as well as cellulose-containing waste liquid from paper and pulp factories. This includes fibers in municipal waste and agricultural waste.

These raw materials are subjected to physical treatments such as pulverization and disintegration, or chemical treatments using acids, alkalis, etc., as required, to form a slurry at a temperature of 10°C, and then sent to an anaerobic liquefaction tank.

Note that, as in the conventional anaerobic digestion method, it is preferable that the C/N ratio of the raw material is in the range of 10 to 20.

As the cellulase to be coexisted in the anaerobic liquefaction process, for example, cellulase produced by cellulase-producing bacteria belonging to the genus Trichotherma, Aspergillus, Irhexas, Fusarium, Pseudomonas, Ruminococcus, Bacillus, etc. is filtered, extracted, It can be used in the form of a culture of these cellulase-producing bacteria without purification or the like.

For the cultivation to produce this cellulase, either liquid culture method or solid culture method can be applied. In the case of liquid culture method, the culture solution is used as it is, and in the case of solid culture method, the whole solid culture is used as it is. It can be used as a cellulase in this state.

In addition, regarding the culture conditions, the culture medium composition uses organic waste containing cellulose as its main component, its anaerobic digestion sludge (solid residue obtained by solid-liquid separation of digestive fluid), or a mixture thereof; Nutrient sources required for cellulase production may be added as necessary depending on the cellulase-producing bacteria.

By using the raw material treated in the anaerobic digestion step, the digested sludge, or a mixture thereof as the main component of the medium, cellulase-producing bacteria can grow and cellulase can be efficiently produced.

Although there are differences depending on the type of cellulase-producing bacteria used and whether the liquid culture method or solid culture method is used, organic waste containing cellulose may be disintegrated or crushed in a wet or dry method, and digested sludge may be separated by sedimentation. It is preferable to use concentration 1 through centrifugation, p-filtration, etc.

Regarding other culture conditions, liquid culture or solid culture may be carried out by conventional methods under aerobic or anaerobic conditions at a preferred pH of 1 depending on the cellulase-producing bacteria used.

In the present invention, the anaerobic liquefaction reaction as the first step is carried out under anaerobic conditions by allowing liquefaction bacteria and cellulase to act on the slurry of the raw material to be treated.

The temperature and pH at this time are 30~60"C14~
6, and can be appropriately selected depending on the waste to be treated, the liquefaction bacteria group used, and the cellulase used.

During the above liquefaction reaction, to maintain the specified pH, caustic soda,
It is preferable to use a neutralizing agent such as soda carbonate, slaked lime, or calcium carbonate.

Since the liquefaction reaction is completed within a few days, the slurry of the decomposition product after the liquefaction reaction is carried out as it is or after solid-liquid separation, the liquid part is led to the gasification step.

For the gasification reaction as the second step, the procedure of the gasification step in the conventional two-stage anaerobic digestion method can be applied as is.

These steps can be carried out either batchwise or continuously.

The present invention makes it possible to apply anaerobic digestion to waste with a high cellulose content, which was difficult to apply in the past. This method solves the problems associated with waste disposal, reduces residual digested sludge, improves methane gas yield, and has great benefits in waste treatment.

The present invention will be explained in more detail below by way of examples.

Example Preparation of raw material slurry for treatment: 3 parts by weight of sewage sludge generated during sewage treatment, 1 part by weight of a category containing mainly organic components in municipal waste, 1 part by weight of pulp lees from a pulp factory, and 5 parts by weight of water. Slur IJ + obtained by mixing and pulverizing a mixture consisting of parts by weight in a blender was used as a raw material for treatment.

The properties of the raw material slurry thus obtained are shown in Table 1.

Table 1 Dry solid content 2.6% (weight) Cellulose content in dry solid content 32.9% (ll) Excluding total N 33% (ll) ll Ash content 17.3% (〃) Preparation of cellulase: Above The raw material slurry was directly subjected to anaerobic fermentation, and the fermented slurry was concentrated by centrifugation to obtain a slurry with a dry solid content of 3 W/V%.

, KH2PO42P for this concentrated slurry 11,
MgSO4-7H200,3r:H and surfactant (T
2 ml of Tween 80 (manufactured by K.) and the bulb residue from the above-mentioned bulb factory were dried for weighing and adjusted to pH 5.5 by adding 2 ml of Tween 80 (manufactured by K.) to an E ball atlas, and then transferred to a 101-volume glass fermenter. 2 at 120℃
The medium was heat sterilized for 0 minutes and used as a cellulase production medium.

Trichoderma viride ATCC 26921 grown on podeto-dextrose agar slant in this medium.
1 platinum loop of glugose yeast extract liquid medium 5
The culture was started by inoculating 6 flasks (300 ml in total) of the seed culture obtained by culturing in flasks at 28° C. for 24 hours.

Culture was performed at 400 rpm stirring, 0.5vvm ventilation, and 28°C.
, pH 4.5 to -5.0 for 120 hours, cellular
-A culture was obtained to be used as an enzyme.

Anaerobic liquefaction reaction: Pour the above raw material slurry into a 101-volume glass jar fermentor and heat under anaerobic conditions at 50°C, pH 4.8 (caustic soda and pH adjuster). The raw material slurry and the above-mentioned culture to be used as cellulase were each incubated for 2 days.
1/'B and 0.4. It was fed at a rate of 1 day2, and the effluent slurry was led to the next gasification tank.

The fermenter was stirred at 12 Orpm and the gas generated was fed into a gas storage tank.

Gasification reaction: 301 capacity glass jar
The above raw material slurry -14,41 was charged into the flask and stirred at 120 rpm under anaerobic conditions at 50°C and pH 7.5 (hydrochloric acid was used as a pH adjuster).

One week later, the slurry discharged from the liquefaction step was introduced into a gasification jar-fermenter, and continuous operation was started.

The generated gas was led to the gas storage tank, and the gasified slurry was received in the receiving tank.

When continuous operation reaches a stable state (normally, more than 2011 days have passed since the start of continuous operation), the gas yield is 10.3 dollars.
(converted to standard state)·l (treated slurry), and the 7methane content in the gas was 64%.

The dry solid content in the treated slurry is 0.9 weight? 1. It was.

Claims (1)

[Claims] 1. A first method for decomposing organic waste containing cellulose under anaerobic conditions in the coexistence of liquefaction bacteria and cellulase.
step, a second step in which the decomposition product obtained in the first step is decomposed and gasified under anaerobic conditions by a group of gasifying bacteria, and a digested slurry obtained in the second step is obtained by solid-liquid separation. A method of producing organic waste containing cellulose, comprising a third step of culturing cellulase-producing bacteria in a medium containing solid residue, organic waste containing cellulose, or both as main components to produce cellulase. Processing method. 2. The treatment method according to claim 1, wherein the cellulase produced in the third step is used for the decomposition treatment in the first step. 3. The treatment method according to claim 1 or 2, wherein the cellulase is a culture obtained by culturing the cellulase-producing bacteria.