JP2006247601A - Methanation method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a methanation method capable of generating a larger amount of gas than a conventional methane fermentation method, and a methanation apparatus. <P>SOLUTION: The methanation method comprises the step of carrying out methane fermentation treatment after an organic waste material containing oils and fats, and protein is subjected to acid fermentation treatment under an aerobic condition. The methanation apparatus includes an acid fermentation treatment tank and a methane fermentation tank. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a methane production method and a methane production apparatus.

  When organic waste is treated with methane bacteria in an anaerobic state, digestive gas (a mixed gas of methane and carbon dioxide) is obtained.

  When methane fermentation is carried out using triglyceride (TG) or fatty acid (FA) such as milk, the amount of gas generated gradually decreases.

  One reason for this is that higher fatty acids produced during the hydrolysis of fats and oils are thought to inhibit the action of methane-fermenting bacteria, separating and removing fats and oils from organic wastewater, and subjecting the supernatant to methane fermentation treatment. A method has been proposed (Patent Document 1).

  However, in this method, since a large amount of organic components are removed before methane fermentation, the amount of generated gas is reduced.

JP-A-8-66693

  An object of this invention is to provide the methane fermentation method of the organic waste which can continue generation | occurrence | production of gas stably.

  Another object of the present invention is to provide an apparatus for carrying out the above method.

  As a result of diligent efforts to solve the above problems, the present inventors have found the following.

1. When methane fermentation is performed using milk as a substrate, inhibition occurs due to fats and oils generated by demulsification.

2. If milk is used as a substrate for methane fermentation after acid fermentation (not limited to lactic acid fermentation), inhibition can be avoided without demulsification.

3. However, in the long term, when milk with a high concentration of acid fermentation (not limited to lactic acid fermentation) is used as a substrate, inhibition by ammonia occurs.

4). By mixing acid fermentation (not limited to lactic acid fermentation) milk with other raw materials (for example, Aosa), ammonia concentration can be kept low and inhibition by ammonia can be avoided.

5. Furthermore, after the milk is acid-fermented (not limited to lactic acid fermentation), the supernatant (whey) from which the solids (mainly proteins denatured by acid) are removed by a method such as centrifugation is low in ammonia concentration. If this is used as a substrate for methane fermentation, inhibition by ammonia can be further avoided.

  The present invention has been completed based on the above findings.

  The gist of the present invention is as follows.

(1) A method for producing methane, comprising subjecting organic waste containing fats and oils to an acid fermentation treatment under anaerobic conditions followed by a methane fermentation treatment.

(2) The methane production method according to (1), wherein the microorganism used for the acid fermentation treatment is a lactic acid bacterium.

(3) The method for producing methane according to (1), wherein the microorganism used for the acid fermentation treatment belongs to the genus Bacillus or the genus Lactobacillus .

(4) Microorganisms used for acid fermentation treatment are Bacillus cereus OZ-6 strain (Accession No .: FERM P-20381), Lactobacillus sp. OZ-7 strain (Accession No .: FERM P-20382) and their related bacterial species. The method for producing methane according to (3), which is selected from the group consisting of:

(5) The methane according to any one of (1) to (4), wherein the organic waste containing fats and oils is selected from the group consisting of mammalian milk, avian eggs and products made from them. Generation method.

(6) Organic waste with less nitrogen content than organic waste before or after acid fermentation treatment of organic waste containing fats and oils under anaerobic conditions The method for producing methane according to any one of (1) to (5), wherein a methane fermentation treatment is performed after adding the product.

(7) The method for producing methane according to (6), wherein the organic waste having a lower nitrogen content than the organic waste containing fats and oils is seaweed.

(8) The seaweed is selected from the group consisting of Aosa, Macombu, Ogonori, Susbinori, Wakame, Anaaaosa, Amanori, Tsunomata, Sawtooth Moku, Black human egusa, Yabregusa, Ribbon Aosa, Button Aosa, Nagaaoosa, Sueaonoori, Usubaaoori The method for producing methane according to (7), wherein the method is at least one kind of seaweed.

(9) The methane production method according to (7) or (8), wherein seaweed is crushed.

(10) The method for producing methane according to (9), wherein the seaweed is further heat-treated.

(11) The organic waste containing fats and oils is subjected to an acid fermentation treatment under anaerobic conditions, and then the produced solid matter is removed, and then the methane fermentation treatment is performed according to any one of (1) to (10). Methane production method.

(12) The method for producing methane according to (11), wherein solids are removed by centrifugation or filter removal.

(13) A methane generator comprising an acid fermentation treatment tank and a methane fermentation treatment tank.

(14) The methane generator according to (13), further comprising means for crushing seaweed.

(15) The methane generator according to (14), further comprising means for heating the seaweed and a tank for heat-treating the seaweed.

(16) The methane generator according to any one of (13) to (15), further comprising solid-liquid separation means.

(17) While using the digestion gas obtained with the methane production | generation apparatus in any one of (13)-(15) as a fuel of a cogeneration facility, while converting into electricity and heat energy, the obtained heat is (1 A method for producing methane, including use in the method for producing methane according to any one of (12) to (12).

(18) While using the digestion gas obtained with the methane production | generation apparatus in any one of (13)-(15) as a fuel of a cogeneration facility, while converting into electricity and heat energy, the obtained heat is (1 The methane production | generation apparatus utilized for the methane production | generation method in any one of ()-(12).

  Examples of the organic waste containing fats and oils include mammalian milk, avian eggs and products made from them as raw materials. Examples of mammalian milk include cow milk and goat milk. Examples of products made from mammalian milk include butter, cheese, yogurt, and nonfat dry milk. Examples of avian eggs include poultry eggs, and examples of products made from avian eggs include mayonnaise.

  Seaweed etc. can be illustrated as an organic waste with less nitrogen content than the organic waste containing fats and oils and protein.

  In the present specification, “acid fermentation treatment” refers to fermentation accompanied by the production of an organic acid. Acid fermentation is basically by anaerobic culture. However, it is not necessary to have a strict (advanced) anaerobic state like methane fermentation. There is no problem if the oxidation-reduction potential (ORP or reduction potential) is 100 mV or less. Fermentation refers to a reaction in which organic substances such as sugar are decomposed to acquire energy by phosphorylation at the substrate level.

The “methane fermentation treatment” is a reaction for obtaining energy using carbon dioxide or acetic acid as a final electron acceptor, and is called methane fermentation because it is performed in a reduced state and the final product is methane. Carbon dioxide is also produced when acetic acid is the final electron acceptor. The microorganism that performs the reaction is called a methanogen or methanogen archaea. A gas (mixed gas of methane and CO ₂ ) generated by methane fermentation is called biogas or digestion gas.

  In methane fermentation using fats and oils such as milk and organic waste containing proteins as substrates, there are two problems: inhibition by fats and oils and inhibition by ammonia. Although not bound by a specific theory, the principle of the present invention is considered as follows.

1.Avoidance of inhibition by fats and oils Fats and oils contained in milk (triglyceride; one molecule of glycerol with an ester bond of three linear fatty acids) is de-emulsified and precipitates, becomes butter-like and floats in the culture medium . (Demulsification is the principle of making butter from milk.)

  This butter-like substance adheres to the surface of the microorganism (methanogen) immobilization carrier and causes clogging. Most of the immobilization carriers have a structure in which pores or thin fibrous materials are folded and the surface area is increased so that the contact between the microorganism and the culture solution is improved. Butter-like substances block these pores. It also adheres to the surface of the microorganism (methane producing bacteria) itself, and inhibits the mass transfer into the microorganism. There are also reports that oils and fats destroy the cell membranes of microorganisms.

  When milk is subjected to acid fermentation under anaerobic conditions (mostly lactic acid fermentation, and acetic acid fermentation and butyric acid fermentation also occur), demulsification does not occur. Therefore, the inhibition by the butter-like substance is not recognized.

2. Avoiding inhibition by ammonia Since milk contains protein, long-term methane fermentation using milk as a substrate results in anaerobic degradation of protein and liberation of ammonia. Ammonia inhibits methane fermentation (ammonium ions do not inhibit).

  When milk is subjected to acid fermentation under anaerobic conditions, the pH is lowered, so that most of the protein is denatured and becomes insoluble in water. This denatured protein can be removed by centrifugation or filter removal. The liquid from which the denatured protein is removed is generally called whey. Whey is thought to contain organic acids, amino acids, highly water-soluble proteins, and sugars. Amino acids are considered to be proteins that have been degraded before denaturation with low pH, proteins that have high water solubility remain water-soluble even when they are denatured, and sugars that are not converted to organic acids by fermentation. In addition, amino acids, highly water-soluble proteins and saccharides are in lower concentrations than the original milk.

  According to the present invention, a larger amount of gas can be generated from organic waste than the conventional methane fermentation method.

  Hereinafter, some embodiments of the present invention will be described with reference to the drawings. Here, milk is used as an organic waste containing fats and oils.

1. FIG. 1 is a flow chart of organic waste recycling including the methane production method of the present invention.

  In the methane production method of the present invention, an organic waste (in this case, milk) containing fats and oils is subjected to an acid fermentation treatment under anaerobic conditions, followed by a methane fermentation treatment.

Milk is acid-fermented in a pretreatment tank. The acid fermentation treatment may be any treatment that allows organic acids to be produced by microorganisms. For example, after heating milk to a temperature suitable for the growth of microorganisms, the microorganisms for producing organic acids are cultured in the solution. Good. When the microorganism is cultured in a solution such as milk, the solution may be an alkaline solution, an acidic solution, or a neutral solution. When culturing microorganisms in an alkaline solution, the pH of the solution at the start of cultivation of microorganisms is 7.5 or more, and when culturing microorganisms in an acidic solution, the pH of the solution at the start of cultivation of microorganisms is When the microorganism is cultured in a neutral solution at a pH of 6.5 or less, the pH of the solution at the start of culturing the microorganism is preferably in the range of 6.5 to 7.5. It is more effective to adjust the pH at the start of the culture to the optimum growth pH of the microorganism to be used. In order to bring the solution to a desired pH, an acid or alkali solution (for example, NaOH solution, KOH solution, Ca (OH) ₂ solution, Mg (OH) ₂ solution, NH ₃ solution, HCl solution, HNO ₃ solution, H ₂ CO ₃ solution) may be added. Culture may be any of static culture, shaking culture, and stirring culture, and may be performed under anaerobic conditions, but is preferably performed under static anaerobic conditions. It is desirable to optimize the culture conditions according to the microorganism used. The culture is preferably performed at a temperature of 10 to 40 ° C. for 12 hours or more. The culture may be any of a batch method, a continuous method, a semi-batch culture method, and a fed-batch culture method.

  The acid fermentation treatment produces at least one organic acid such as acetic acid, lactic acid, formic acid, butyric acid, propionic acid, pyruvic acid, glyoxylic acid, and oxalic acid. In addition, it is necessary to produce | generate at least 1 type of organic acid which can be biochemically converted into an acetic acid by acid fermentation process.

The microorganism may be any microorganism as long as it produces an organic acid from a raw material (here, milk, seaweed, etc.) serving as a substrate. The types of microorganisms include lactic acid fermentation microorganisms, soil microorganisms, food microorganisms, etc., or microorganisms that inhabit the sea, for example, microorganisms that inhabit the sea area from which seaweeds are collected, or that adhere to the collected seaweeds. Such as microorganisms. Specific examples include microorganisms belonging to the genus Lactobacillus , Bacillus genus and Lactobacillus. Among these, Bacillus cereus OZ-6 strain, Lactobacillus sp. OZ-7 strain, and their related species (16S-rDNA base) Microorganisms whose sequences are 98% or more identical are preferred. These microorganisms may be used alone as a microorganism, or a mixed microorganism system in which these microorganisms are mixed and function effectively. The amount of microbial seed is preferably 10 ⁵ cells or more per ml of the solution.

  Milk subjected to acid fermentation is methane-fermented in a methane fermentation tank. Digestion gas produced in the methane fermentation tank (methane gas, mixed gas of methane gas and carbon dioxide, etc.) is removed with hydrogen sulfide (desulfurization) in a gas purification facility (not shown) if necessary, and then digested gas is digested. It is sent to a gas utilization facility (for example, a cogeneration facility including these facilities such as a gas engine, a gas turbine, and a fuel cell, a boiler, etc.) and used as electricity and thermal energy. Although not shown, it is desirable to install a gas storage facility (gas tank) after the gas purification facility. If necessary, a gas compressor or a drain treatment device is used. When a cogeneration facility or a boiler is used, all or part of the obtained heat is used as a heat source for preheating for heating, heating or heating, and heating of the methane fermentation tank. As a heat source for preheating, heat generated (recovered) at the time of cooling when transferring milk from the acid fermentation tank to the methane fermentation tank can also be used. A part of the heat obtained from the cogeneration facility and the boiler may be used for heating and heating the acid fermentation treatment tank and the methane fermentation tank. By using these heats, the energy can be used more effectively. Moreover, it can also use for the fuel of a motor vehicle and a ship as a utilization method of digestion gas.

  The residue remaining in the methane fermenter after the methane fermentation is performed (milk after the methane fermentation is performed) can be used as a fertilizer, a soil improvement material, or the like.

  Methane fermentation is performed by culturing methanogens in an anaerobic state with milk subjected to acid fermentation treatment. In addition, about the methane fermentation method, the thing similar to the methane fermentation method generally performed may be sufficient. (Reference: Methane fermentation of waste, Scientist 2000)

2. FIG. 2 is a flow diagram of another organic waste recycling that includes the methane production process of the present invention.

  In the methane production method of the present invention, the organic waste (in this case, milk) containing fats and oils is subjected to an acid fermentation treatment under anaerobic conditions, after the acid fermentation treatment, or simultaneously with the acid fermentation treatment, the organic waste. After adding organic waste (here, seaweed) having a lower nitrogen content than waste, methane fermentation treatment may be performed.

  First of all, by pretreatment means, Aosa, Macombu, Ogonori, Susbinori, Wakame, Anaaaosa, Amanori, Tsunomata, Sawtooth Moku, Black Hitusa, Yabregusa, Ribbon Aosa, Button Aosa, Nagaaosa, Suseoonori, Usu-Aoori To process. The seaweed may be naturally inhabited in the sea, coral, beach, or the like, or may be cultured. The seaweed that is cultivated may be cultivated for food or dashi, or may be cultivated as a countermeasure for eutrophication in the sea area. The seaweed may be dried. Furthermore, the seaweed residue which extracted effective ingredients, such as an umami | flavor ingredient and alginic acid, may be sufficient. In the present invention, these seaweeds can be collected and used.

For example, as a pretreatment, seaweed is crushed or crushed using a crushing means such as a mill or a cutter, and then an appropriate liquid (for example, neutral water (pH 6.5 to 7.5), alkaline solution (pH 7.5 or more), It is diluted to an appropriate concentration (for example, a concentration containing 0.1 to 15% by weight of seaweed by dry weight) with an acid solution (pH 6.5 or less). Neutral water includes pure water, tap water, industrial water, and the like. Examples of the alkaline solution include an NaOH solution, a KOH solution, a Ca (OH) ₂ solution, an Mg (OH) ₂ solution, an NH ₃ solution, or a solution obtained by mixing at least two of these. Examples of the acid solution include an HCl solution, an HNO ₃ solution, an H ₂ SO ₄ solution, an H ₂ CO ₃ solution, or a solution in which at least two of these are mixed.

If seaweed contains a lot of skeletal polysaccharides and viscous polysaccharides (eg cellulose, hemicellulose, glucuronoxyloramnan sulfate, glucuronoxyloramnogalactan sulfate, alginic acid, fucoidan, agarose, galactan, funolan, etc.) The seaweed solution obtained by the treatment may be heat treated. This heat treatment reduces the molecular weight of the skeletal polysaccharide and viscous polysaccharide of seaweed. The heat treatment may be any treatment that can reduce the molecular weight of the seaweed skeletal polysaccharide and viscous polysaccharide by heating the seaweed, and is preferably heated at a temperature of 50 ° C. or higher and maintained at that temperature for a predetermined time. To do. Since this reaction is a hydrolysis reaction, the treatment time can be shortened by increasing the treatment temperature. The heat treatment may be performed by any method using any apparatus, for example, using an autoclave, a thermostatic bath, a water bath, an oil bath, steam addition, or the like. The heat treatment may be performed under aerobic conditions or anaerobic conditions. When seaweed is heat-treated in an alkaline solution, the pH of the solution at the start of heat treatment is preferably 7.5 or more. When seaweed is heat-treated in an acid solution, the pH of the solution at the start of heat treatment is preferably 6.5 or less. In order to bring the solution to a desired pH, an acid or alkali solution (for example, NaOH solution, KOH solution, Ca (OH) ₂ solution, Mg (OH) ₂ solution, NH ₃ solution, HCl solution, HNO ₃ solution, H ₂ SO ₄ solution, H ₂ CO ₃ solution) may be added. When heat-treating seaweed in a neutral solution, pure water, tap water, industrial water, etc. should be used as they are, and the solution having a pH of 6.5 to 7.5 at the start of heat treatment should be used. .

  The amount of the skeletal polysaccharide and the viscous polysaccharide in the seaweed after the heat treatment is not particularly limited. In this specification, the amount of the water-soluble fraction dissolved in the solution is used as an index to estimate the degree of molecular weight reduction of the skeletal polysaccharide and the viscous polysaccharide. Regarding the amount of the water-soluble fraction, the difference between the weight of the solid before the treatment and the weight of the solid in the solution after the treatment is taken.

  Pretreatment, and optionally further heat-treated seaweed solution is added to the pretreatment tank. When the seaweed solution is heat-treated, it may be added to the pretreatment tank after being cooled to a temperature suitable for the growth of microorganisms used in the pretreatment tank. The subsequent processing is the same as in FIG.

3. FIG. 3 is yet another organic waste recycling flow diagram that includes the methane production process of the present invention.

  In the methane production method of the present invention, an organic waste (in this case, milk) containing fats and oils is subjected to an acid fermentation treatment under anaerobic conditions, and then the produced solid matter is removed, followed by a methane fermentation treatment. Good.

  Milk is subjected to an acid fermentation treatment as in FIG. Thereafter, solid matter is removed from the milk subjected to the acid fermentation treatment by solid-liquid separation means.

  Examples of the solid-liquid separation method include centrifugation and filter removal.

  Examples of the solid-liquid separation means include a centrifuge, a decanter, a filter press, and a filtration device.

  The solid after the solid-liquid separation can be used as a fertilizer, a soil improvement material, or the like.

  The liquid after solid-liquid separation is subjected to methane fermentation treatment in a methane fermentation tank. The subsequent processing is the same as in FIG.

  Although the present invention has been described above with reference to the drawings, modifications and improvements obvious to those skilled in the art are also within the scope of the present invention.

  Hereinafter, the present invention will be specifically described by way of examples. These examples are for explaining the present invention, and do not limit the scope of the present invention.

  The apparatus used for the methane fermentation method of Example 1 is shown in FIG. Milk was flowed into the acid fermenter and cultured in the thermostat (1) with the microorganisms, resulting in the production of organic acids. Milk fermented with acid fermentation containing organic acids flows into the methane fermenter and is cultured in a thermostat (2) with methanogens fixed to the carrier. As a result, digestion gas (methane gas, methane gas and A mixed gas with carbon). The produced digestion gas was collected in a gas collector (means for collecting the produced methane gas). As the methanogen, the bacterial species used in ordinary methane fermentation was used. The methanogen was cultured while stirring the culture solution with a stirrer. The pH of the culture solution was measured with a pH meter.

  The apparatus used for the methane fermentation method of Example 2 is shown in FIG. Milk was flowed into the acid fermenter along with pretreated and heat-treated seaweed. Other processes are the same as those in the first embodiment.

  The apparatus used for the methane fermentation method of Example 3 is shown in FIG. The acid fermentation treatment of milk is the same as in Example 1. The acid-fermented milk containing organic acid was solid-liquid separated by a centrifuge and then flowed into a methane fermentation tank. Subsequent processing is the same as in the first embodiment.

  Moreover, the composition of the synthetic medium for methane fermentation used in Comparative Examples and Examples 1 to 3 is as follows.

Comparative example

1. Test conditions In a 600 ml glass reactor, 600 ml of milk and a small amount of inoculum (sludge system) were added. A porous carrier was placed in the liquid as a microorganism-fixing carrier. Stirring was performed with a magnetic stirrer. The reactor was installed in a thermostat and controlled at 55 ° C. The pH was controlled at about 7.0 to 8.3. The evolved gas was collected by water replacement. On the 21st day from the start of the test, 400 ml of milk was replaced.

2. Experimental results The results are shown in FIG. The figure shows the integrated value of gas generation from the start of the test. On the 21st day, after confirming that gas generation was almost gone, the raw milk was replaced. In the second test, the amount of gas generated decreased drastically. The state of the carrier installed in the reactor after the test is shown in FIG. As can be seen from the photograph, a large amount of oily substance was deposited on the surface of the carrier. The decrease in gas generation is thought to be caused by the poisoning of microorganisms by oily substances.

  Milk was acid-fermented and then methane-fermented. The test conditions are as follows.

1. Test conditions (Pretreatment 1)
Acid Fermentation Treatment In a glass reactor (1000 ml), 10 g of fermented food (seafood pickled in seafood) was added to 1000 ml of commercially available milk, stirred gently, and then statically cultured in a thermostat (30 ° C.) for 48 hours.

2. Test conditions (methane fermentation treatment)
In a 1 L glass reactor, a porous carrier (about 30 cc) was placed in the liquid as a microorganism-fixing carrier. Stirring (about 50 rpm) was performed with a magnetic stirrer. The reactor was installed in a thermostat and controlled at 55 ° C. The pH was controlled at about 7.5.

  100 ml of the pretreatment liquid and a small amount of inoculum (sludge system) were added to 900 ml of the synthetic medium (above). Then, the operation | work which replaces 100 ml of pretreatment liquids and methane fermentation liquids was repeated suitably, and the continuous fermentation test was done. The evolved gas was collected by water replacement. The ammonia concentration in the reactor solution was measured with an ion chromatograph manufactured by Shimadzu. The organic acid concentration in the reactor solution was measured with a Shimadzu liquid chromatograph.

3. Experimental results The results are shown in FIGS. No inhibition by oil was observed. The generation of biogas was continuous. However, acetic acid, a direct substrate for methane, accumulated. This was thought to be a result indicating that the methane production process was somewhat disturbed. In addition, with the passage of time, the ammonia concentration increased (exceeding 3000 ppm).

  After pre-treating seaweed, it was mixed with milk and subjected to acid fermentation. Thereafter, a methane fermentation treatment was performed. The test conditions are as follows.

1. Test conditions (Pretreatment 2)
(1) Seaweed pretreatment Dried seaweed was pulverized with PERSONAL MILL SCM-40 manufactured by SHIBATA. 50 g of ground Aosa was added to water (1000 ml) and treated in an autoclave at 121 ° C. for 15 minutes.

(2) Acid fermentation treatment of seaweed + milk In a glass reactor (1000 ml), 500 ml of commercially available milk and 500 ml of the seaweed treatment solution were mixed, and 10 g of fermented food (seafood pickled in seafood) was added. After gently stirring, the cells were statically cultured in a thermostatic chamber (30 ° C.) for 48 hours.

2. Test conditions (methane fermentation treatment)
In a 1 L glass reactor, a porous carrier (about 30 cc) was placed in the liquid as a microorganism-fixing carrier. Stirring (about 50 rpm) was performed with a magnetic stirrer. The reactor was installed in a thermostat and controlled at 55 ° C. The pH was controlled at about 7.5.

  100 ml of the pretreatment liquid and a small amount of inoculum (sludge system) were added to 900 ml of the synthetic medium (above). Thereafter, the pretreatment solution was appropriately replaced by 100 ml until the 80th day of culture, and after the 81st day of culture, the load was increased and 150 ml was replaced. The evolved gas was collected by water replacement. The ammonia concentration in the reactor solution was measured with an ion chromatograph manufactured by Shimadzu. The organic acid concentration in the reactor solution was measured with a Shimadzu liquid chromatograph.

3. Experimental results The results are shown in FIGS. There was little accumulation of organic acids, and biogas generation was vigorous. Further, the ammonia concentration was maintained at about 2500 ppm.

  After the milk was subjected to an acid fermentation treatment, it was centrifuged and the supernatant (whey) was subjected to a methane fermentation treatment. The test conditions are as follows.

1. Test conditions (Pretreatment 3)
Acid fermentation treatment (whey)
In a glass reactor (1000 ml), 10 g of fermented food (seafood pickled in seafood) was added to 1000 ml of commercially available milk. After gently stirring, the cells were statically cultured in a thermostatic chamber (30 ° C.) for 48 hours. Thereafter, the statically cultured solution was placed in a 200 ml container, centrifuged at 3000 rpm for 30 minutes, and only the supernatant (whey) was collected.

2. Test conditions (methane fermentation treatment)
In a 1 L glass reactor, a porous carrier (about 30 cc) was placed in the liquid as a microorganism-fixing carrier. Stirring (about 50 rpm) was performed with a magnetic stirrer. The reactor was installed in a thermostat and controlled at 55 ° C. The pH was controlled at about 7.5.

  100 ml of whey was added to what was subjected to a continuous fermentation test for several months with pretreated milk, and a continuous test was performed. The evolved gas was collected by water replacement. The ammonia concentration in the reactor solution was measured with an ion chromatograph manufactured by Shimadzu. The organic acid concentration in the reactor solution was measured with a Shimadzu liquid chromatograph.

3. Experimental results The results are shown in FIGS. The generation of biogas was vigorous, and the amount of organic acid accumulated was decreasing. This seems to be because the organic acids are converted to methane + CO _2. Further, the ammonia concentration was lowered.

We tried to isolate organic acid-producing bacteria from fermented food (seafood pickles) using tryptosoy agar medium (pH5.5), tryptosoy agar medium (pH7.3) and LBS agar medium (pH5.5). The culture was performed anaerobically in a CO ₂ / H ₂ atmosphere at 30 ° C. for 7 days. Fifteen strains from OZ-1 to OZ-15 were obtained as a single colony.

  Next, each of the 15 isolates was inoculated into Aosa heat treatment solution (5% dry Aosa suspended in distilled water and autoclaved at 121 ° C for 15 minutes), followed by stationary culture at 30 ° C for 7 days. It was. The culture solution after completion of the culture was subjected to HPLC, and the produced organic acid was quantified. A part of the results is shown in Table 2.

  The OZ-6 and OZ-7 strains that produced significant amounts of organic acid (lactic acid) were identified. Table 3 shows typical mycological properties.

Furthermore, the 16S-rDNA base sequences of the OZ-6 and OZ-7 strains were decoded, and the results were collated with a database to determine the taxonomic position. As a result, the base sequence (533 bp) of 16S-rDNA of OZ-6 strain was 100% identical with the base sequence of 16S-rDNA of Bacillus cereus . Further, the base sequence (562 bp) of 16S-rDNA of the OZ-7 strain was 98.9-99.1% identical with the base sequence of 16S-rDNA of Lactobacillus fructivorans .

Based on the above, the OZ-6 strain was identified as Bacillus cereus . The OZ-7 strain was identified as a bacterium belonging to the genus Lactobacillus .

  The base sequence (533 bp) of 16S-rDNA of OZ-6 strain is shown in SEQ ID NO: 1. The base sequence (562 bp) of 16S-rDNA of OZ-7 strain is shown in SEQ ID NO: 2.

  In addition, OZ-6 shares were registered with the Patent Microorganism Deposit Center (IPOD) (1-1-1 East Tsukuba City, Ibaraki Prefecture) on January 28, 2005, under the accession number FERM P-20381. Has been deposited. The OZ-7 strain was deposited on January 28, 2005 at the National Institute of Advanced Industrial Science and Technology Patent Microorganism Depositary Center (IPOD) (1-1-1 East Tsukuba, Ibaraki) under the accession number FERM P-20382. Has been.

  According to the present invention, a larger amount of gas can be generated from organic waste than the conventional methane fermentation method. The methane production method and apparatus of the present invention makes it possible to effectively use organic waste as an energy source. Furthermore, fertilizer can also be obtained as a by-product.

It is a flowchart of organic waste recycling including the methane production | generation method of this invention. It is a flowchart of another organic waste recycling including the methane production | generation method of this invention. It is a flowchart of another organic waste recycling including the methane production | generation method of this invention. An example of the methane production | generation apparatus of this invention is shown. Another example of the methane production | generation apparatus of this invention is shown. Another example of the methane production | generation apparatus of this invention is shown. It is a graph which shows the experimental result of a comparative example. The number of days on the horizontal axis is the number of culture days in the methane fermentation treatment. The vertical axis represents the integrated value of the biogas amount. The mode of the support | carrier installed in the reactor of a comparative example is shown. 4 is a graph showing experimental results of Example 1. The upper figure shows the time change of the gas generation rate, and the lower figure shows the time change of the organic acid concentration. The number of days on the horizontal axis is the number of culture days in the methane fermentation treatment. 2 is a graph showing the ammonia concentration in the reaction tank in Example 1. FIG. 6 is a graph showing experimental results of Example 2. The upper figure shows the time change of the gas generation rate, and the lower figure shows the time change of the organic acid concentration. The number of days on the horizontal axis is the number of culture days in the methane fermentation treatment. 4 is a graph showing the ammonia concentration in the reaction tank in Example 2. 10 is a graph showing experimental results of Example 3. The upper figure shows the time change of the gas generation rate, and the lower figure shows the time change of the organic acid concentration. The number of days on the horizontal axis is the number of culture days in the methane fermentation treatment. 6 is a graph showing the ammonia concentration in the reaction tank in Example 3.

<SEQ ID NO: 1>
SEQ ID NO: 1 shows a partial base sequence (533 bp) of 16S-rDNA of OZ-6 strain.
<SEQ ID NO: 2>
SEQ ID NO: 2 shows the partial base sequence (562 bp) of 16S-rDNA of OZ-7 strain.

Claims (18)

A method for producing methane, comprising subjecting organic waste containing fats and oils to acid fermentation under anaerobic conditions followed by methane fermentation. The method for producing methane according to claim 1, wherein the microorganism used in the acid fermentation treatment is a lactic acid bacterium. The method for producing methane according to claim 1, wherein the microorganism used in the acid fermentation treatment belongs to the genus Bacillus or the genus Lactobacillus . Microorganisms used for acid fermentation treatment are Bacillus cereus OZ-6 strain (Accession No .: FERM P-20381), Lactobacillus sp. OZ-7 strain (Accession No .: FERM P-20382) and their related bacterial species 4. The method of producing methane according to claim 3, which is selected. The method for producing methane according to any one of claims 1 to 4, wherein the organic waste containing fats and oils is selected from the group consisting of mammalian milk, avian eggs and products made from them. Organic waste containing fat and protein is added before or after acid fermentation under anaerobic conditions or at the same time as acid fermentation. Then, the methane production method according to any one of claims 1 to 5, wherein the methane fermentation treatment is performed. The method for producing methane according to claim 6, wherein the organic waste having a lower nitrogen content than the organic waste containing fats and oils is seaweed. The seaweed is selected from the group consisting of Aosa, Macombu, Ogonori, Sugobinori, Wakame, Anaaaosa, Amanori, Tsunomata, Sawtooth Moku, Black-faced Rabbit, Yabregusa, Ribbon Aosa, Button Aosa, Nagaaosa, Sueaonori, Usubaaoori, Touhou Aonori The method for producing methane according to claim 7, which is a kind of seaweed. The method for producing methane according to claim 7 or 8, wherein seaweed is crushed. The method for producing methane according to claim 9, wherein the seaweed is further heat-treated. The methane production | generation method in any one of Claims 1-10 which perform the methane fermentation process after removing the produced | generated solid substance after carrying out the acid fermentation process of the organic waste containing fats and oils and anaerobic conditions. The method for producing methane according to claim 11, wherein the solid matter is removed by centrifugation or filter removal. A methane generator comprising an acid fermentation tank and a methane fermentation tank. Furthermore, the methane production | generation apparatus of Claim 13 provided with the means for crushing a seaweed. Furthermore, the methane production | generation apparatus of Claim 14 provided with the means for heating a seaweed, and the tank for heat-treating a seaweed. Furthermore, the methane production | generation apparatus in any one of Claims 13-15 provided with a solid-liquid separation means. The digested gas obtained by the methane generator according to any one of claims 13 to 15 is used as a fuel for a cogeneration facility, and is converted into electricity and thermal energy, and the obtained heat is converted to any one of claims 1 to 12. A method for producing methane, including use for the method for producing methane according to claim 1. The digested gas obtained by the methane generator according to any one of claims 13 to 15 is used as a fuel for a cogeneration facility, and is converted into electricity and thermal energy, and the obtained heat is converted to any one of claims 1 to 12. A methane generator used for the methane generation method according to claim 1.

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