JP7260904B2 - Biogas generation method - Google Patents

Description

The present invention relates to a method for producing biogas.

Conventionally, gas-producing bacteria such as hydrogen-producing bacteria that produce hydrogen gas and methanogens that produce methane gas are used to produce biogas derived from living organisms. biogas is generated by mixing with a solution in which organic substances are dissolved, and maintaining the mixed liquid at an appropriate temperature at which gas-producing bacteria can generate gas for a certain period of time (for example, Patent Documents 1 and 2). reference).

Japanese Patent Application Laid-Open No. 2005-200283 Japanese Patent Application Laid-Open No. 2006-021130

However, in Patent Documents 1 and 2, it is necessary to obtain the gas-producing bacteria themselves to be added to the liquid in which the organic matter is dissolved and to culture them under appropriate temperature control, etc., and the liquid mixed with the gas-producing bacteria Also, an environment suitable for gas-producing bacteria to generate gas, for example, if the gas-producing bacteria are anaerobic, an anaerobic environment that satisfies anaerobic conditions, or an appropriate temperature environment in which gas-producing bacteria actively operate It must be maintained for a certain period of time, and labor and energy are required to obtain and culture these gas-producing bacteria, as well as to create an environment suitable for gas generation. There was a problem that it would be expensive.

The present invention has been made in view of such problems, and an object of the present invention is to provide a biogas production method capable of producing biogas at low cost.

In order to solve the above problems, the method for generating biogas according to claim 1 of the present invention comprises:
A method for producing biogas using biogas-producing bacteria that produce biogas in an anaerobic atmosphere,
a pumping step of pumping up the groundwater of the groundwater layer containing the biogas-producing bacteria so as not to mix oxygen in the air;
The groundwater pumped up in the pumping step is mixed with a specific organic substance capable of generating gas by decomposition by biogas-producing bacteria contained in the groundwater in a low-oxygen atmosphere with a predetermined oxygen concentration lower than the oxygen concentration in the air. a mixing step of
A circulation step of returning the groundwater mixed with the specific organic matter in the mixing step to the groundwater layer so as not to mix with oxygen in the air;
a biogas extracting step of extracting biogas from the groundwater layer after a predetermined generation period corresponding to the biogas-producing bacteria has passed since the circulation step;
is characterized by including
According to this feature, since the groundwater containing the biogas-producing bacteria is pumped up from the groundwater layer, it is not necessary to obtain the biogas-producing bacteria. Since biogas is generated by biogas-producing bacteria by returning groundwater mixed with organic matter to the original groundwater layer, the cost of maintaining an environment where biogas-producing bacteria can produce biogas on the ground is reduced. Therefore, biogas can be produced at low cost.

The method for generating biogas according to claim 2 of the present invention is the method for generating biogas according to claim 1,
A degassing step of degassing a high-concentration liquid mixed with the specific organic matter at a concentration higher than the concentration of the specific organic matter in groundwater after the mixing step,
In the mixing step, the specific organic substance is mixed using the high-concentration liquid degassed in the degassing step.
According to this feature, it is possible to prevent the biogas-producing bacteria from dying or decreasing due to the mixture of the specific organic matter containing oxygen.

The method for producing biogas according to claim 3 of the present invention is the method for producing biogas according to claim 1 or 2,
Repeating the pumping step, the mixing step and the reflux step,
It is characterized in that the volume concentration of the specific organic substance mixed in the mixing step is gradually increased for each repetition.
According to this feature, when a high concentration of specific organic matter is mixed at once, other bacteria other than biogas-producing bacteria are generated in the groundwater layer due to the specific organic matter that cannot be completely processed by the biogas-producing bacteria. It is possible to prevent the generation of gas from being adversely affected.

The method for generating biogas according to claim 4 of the present invention is the method for generating biogas according to any one of claims 1 to 3,
It is characterized in that the groundwater from which the biogas is taken out by pumping up in the pumping process is reprocessed by the mixing process and the reflux process.
According to this feature, it is possible to efficiently generate biogas by reusing the biogas-producing bacteria proliferated in the presence of the specific organic matter.

The method for generating biogas according to claim 5 of the present invention is the method for generating biogas according to any one of claims 1 to 4,
The biogas-producing bacterium is characterized by being a hydrogen gas-producing bacterium or a methane gas-producing bacterium.
According to this feature, it is possible to inexpensively generate hydrogen gas or methane gas with high industrial utility value.

The method for generating biogas according to claim 6 of the present invention is the method for generating biogas according to any one of claims 1 to 5,
The specific organic matter is characterized in that it is glucose extracted from food residue.
According to this feature, high-quality specific organic matter necessary for generating biogas can be obtained at low cost.

The present invention may include only the matters specifying the invention described in the claims of the present invention, or may include the matters specifying the invention described in the claims of the present invention as well as the matters specifying the invention other than the matters specifying the invention. It can be anything.

It is a figure which shows the structure of a biogas generation system. FIG. 2 is a diagram showing the configuration of an organic matter mixing device in the biogas generation system; FIG. 4 is a diagram showing steps of a biogas generation method in a biogas generation system;

An embodiment for carrying out the method for producing biogas according to the present invention will be described below.
(embodiment)

FIG. 1 is a diagram showing the configuration of the biogas generation system of the present embodiment, FIG. 2 is a diagram showing the configuration of an organic substance mixing device in the biogas generation system, and FIG. FIG. 4 is a diagram showing steps of a gas generation method;

In the ground, as shown in Fig. 1, there is an organic accretion zone region having a groundwater layer containing anaerobic hydrogen-producing bacteria and a groundwater layer containing anaerobic methanogens. There are areas such as hot spring areas that have underground water of about 30 to 85°C where methanogens are activated. In general, the temperature at which anaerobic hydrogen-producing bacteria are activated is around 60°C, which is higher than the temperature at which anaerobic methanogens are activated at around 45°C. Groundwater formations are often deeper than those containing anaerobic methanogens. In FIG. 1, the groundwater layer containing anaerobic hydrogen-producing bacteria exemplifies the form in which the groundwater layer containing anaerobic methanogenic bacteria is an individual groundwater layer. For example, it may consist of a single groundwater layer so that the upper layer with high temperature is a layer with anaerobic hydrogen-producing bacteria, and the lower layer with low temperature is with anaerobic methanogens. be.

FIG. 1 illustrates an area having two groundwater layers, one containing anaerobic hydrogen-producing bacteria and the other containing anaerobic methanogens. It may be an area with only one groundwater layer.

Examples of these anaerobic hydrogen-producing bacteria include the genus Clostridium, the genus Enterobacter, and Thermococcus kodakaraensis found in hot springs in Kodakara Island, Kagoshima Prefecture. is exemplified, and the above-mentioned anaerobic hydrogen-producing bacteria produce 2 mol of hydrogen in the process of producing 2 mol of pyruvic acid from 1 mol of glucose, and further 2 mol of acetic acid in the process of producing 2 mol of acetic acid from pyruvic acid. To produce 1 mole of hydrogen, a total of 4 moles (about 90 liters) of hydrogen can be produced from 1 mole of glucose.

The biogas generation system 1 of this embodiment, which is provided in an area having two groundwater layers, a groundwater layer containing these anaerobic hydrogen-producing bacteria and a groundwater layer containing anaerobic methanogens, is shown in FIG. It mainly consists of a first well device 2 , a second well device 3 , a gas extraction device 4 and an organic substance mixing device 5 . The distance between the first well apparatus 2 and the second well apparatus 3 may be appropriately determined according to the topography, the scale of the groundwater layer, etc., but for example, from the viewpoint of airtightness, the distance may be between 10m and 100m. It should be a range.

The first well apparatus 2 is provided with a highly airtight pump P such as a gear pump. A first underground pipe 11 and a highly airtight second underground pipe 12 extending to a groundwater layer containing anaerobic methanogens are connected, and the first underground pipe 11 or the second underground pipe 12 is connected by the first well apparatus 2. Through underground pipes 12, groundwater containing anaerobic hydrogen-producing bacteria and groundwater containing anaerobic methanogens are supplied from each groundwater layer without increasing the oxygen concentration of the groundwater due to contamination with oxygen in the air. It is designed so that it can be pumped out to the ground.

The second well apparatus 3 is also provided with a pump P such as a highly airtight gear pump. A highly airtight third underground pipe 21 and a highly airtight fourth underground pipe 22 extending to the groundwater layer containing anaerobic methanogens are connected to the pump P, and anaerobic hydrogen is supplied from each groundwater layer. Groundwater containing methanogenic bacteria and groundwater containing anaerobic methanogenic bacteria can be pumped out to the ground without oxygen from the air causing an increase in the oxygen concentration of the groundwater. Mixed groundwater to which glucose, which is a specific organic substance, has been added (mixed) in the organic substance mixing device 5 can be fed into each groundwater layer without mixing with oxygen in the air. The pump P may be any pump as long as it can pump up groundwater or send it into the groundwater layer without contamination with oxygen in the air.

Between the first well apparatus 2 and the second well apparatus 3, groundwater pumped up by the first well apparatus 2 is supplied through a supply pipe 6, and hydrogen is produced from the groundwater by anaerobic hydrogen-producing bacteria. A gas extraction device 4 for extracting groundwater gas containing biogas such as hydrogen gas and methane gas produced by anaerobic methanogens; is provided, and the mixed groundwater to which glucose has been added (mixed) by the organic matter mixing device 5 is supplied to the second well device 3, and the second Mixed groundwater is circulated to each groundwater layer from the well apparatus 3 through the third underground pipe 21 and the fourth underground pipe 22 .

The first well apparatus 2 and the second well apparatus 3 are provided with a discharge pipe G connected to the pump P, and the pumped groundwater can be discharged to the outside through the discharge pipe G. .

That is, in the first well apparatus 2, when the pumped groundwater exceeds the throughput of the gas extraction apparatus 4, it can be discharged through the discharge pipe G. As shown in FIG. Also, in the second well apparatus 3, the pump P is reversely rotated to pump up groundwater in the same manner as in the first well apparatus 2 and discharge it through the discharge pipe G, whereby the third underground pipe 21 and the fourth underground After the inside of the middle tube 22 is filled with groundwater containing almost no oxygen, the pump P is rotated forward to cause the mixed groundwater to which glucose is added (mixed) to circulate, thereby forming a third ground. The air (oxygen) existing inside the middle pipe 21 and the fourth underground pipe 22 is sent into each groundwater layer, and the activity of anaerobic hydrogen-producing bacteria and anaerobic methanogens in each groundwater layer is reduced. Alternatively, it is possible to prevent a decrease in the amount of anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria per unit volume due to partial death.

Groundwater pumped up by the first well device 2 is supplied to the gas extraction device 4, and groundwater gases such as hydrogen gas and methane gas contained in the groundwater are extracted. These groundwater gases are not isolated gases, but are mostly contained in the groundwater in a state dissolved in the groundwater. Although a device for extracting groundwater by depressurizing is used, the present invention is not limited to this, and any device using a method other than depressurization may be used as long as it can effectively extract groundwater gas. may

In addition, in the gas extracting device 4, it is not always necessary to take out the groundwater gas from the groundwater pumped up by the first well device 2. For example, when the mixed groundwater is first circulated, organic substances may be extracted without taking out the groundwater gas. A mixing device 5 can also be fed.

Next, the organic substance mixing device 5 for adding (mixing) glucose to the groundwater that has passed through the gas extraction device 4 will be described in more detail with reference to FIG. The organic substance mixing device 5 of this embodiment has an extraction tank 41, a filtering device 49, a deaeration tank 42, and a deaeration device 43, as shown in FIG.

The extraction tank 41 is a tank for extracting glucose (starch) from potato skins Z, which are food residues. A drive motor 56 is provided for rotationally driving the stirring blades. A branch pipe 44 branched from a supply pipe 7 to which groundwater that has passed through the gas extraction device 4 is supplied is connected to the upper side surface of the extraction tank 41. A supply valve 47 is provided on the branch pipe 44. Groundwater is supplied into the extraction tank 41 through the branch pipe 44 by opening the .

Note that the potato skins Z to be fed from the inlet 55 should be sterilized in advance with ultraviolet light or the like so that the adhering bacteria do not adversely affect the anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria. ing.

In addition, the extraction tank 41 is provided with a discharge port 58 for discharging the potato skins Z after the glucose has been extracted, at the center of the bottom, and on the side of the lower part, a high-concentration glucose is produced by the extraction. A discharge pipe 45 for discharging the groundwater contained in the masterbatch (hereinafter referred to as masterbatch groundwater) is connected, and the other end of the discharge pipe 45 is connected to a degassing tank 42, Groundwater is supplied to the tank 42 for degassing.

A filtration device 49 and a valve 49' are provided on the path of the discharge pipe 45, and insoluble foreign matter such as small pieces of potato skin Z contained in the masterbatch groundwater is removed by filtration. The masterbatch groundwater thus prepared is supplied to a degassing tank 42 .

A deaerator 43 is connected to the upper part of the deaeration tank 42 via connecting pipes 50 and 51, and the air (especially oxygen) contained in the masterbatch groundwater supplied into the deaeration tank 42 is removed. is removed by reducing the pressure with the valve 49' closed, nitrogen gas containing no oxygen is supplied into the degassing tank 42 to maintain a low-oxygen atmosphere. Nitrogen gas is supplied so that the masterbatch groundwater inside the degassing tank 42 flows through the supply pipe 7 even if the valve 48 is opened while the pressure in the degassing tank 42 remains reduced. This is because they cannot be well added to and mixed with groundwater.

The masterbatch groundwater inside the deaeration tank 42, which has been deaerated by the deaerator 43 and kept in a low-oxygen atmosphere, flows down the injection pipe 46 by opening the valve 48 and is added to the groundwater passing through the supply pipe 7. be done. In addition, although not shown in FIG. 2, in order to stably add the masterbatch groundwater, a constant amount discharge device is provided on the injection pipe 46, and a constant amount of water is discharged at a constant time. A masterbatch groundwater is added to the groundwater passing through the supply pipe 7 . In addition, a constant flow of groundwater flows through the supply pipe 7 .

Next, the steps of the biogas generation method using the biogas generation system of this embodiment will be described with reference to FIG.

The biogas generation method using the biogas generation system includes, as shown in FIG. 3, a groundwater pumping process, an organic matter mixing process, a mixed groundwater circulation process, a biogas generating process, and a biogas extracting process.

In the groundwater pumping process, groundwater containing anaerobic hydrogen-producing bacteria or groundwater containing anaerobic methanogens is pumped up from each groundwater layer through the first underground pipe 11 or the second underground pipe 12 by the first well apparatus 2. and supplying it to the gas extraction device 4 . For pumping, only one of the first underground pipe 11 and the second underground pipe 12 is used. In the following description, the case of anaerobic hydrogen-producing bacteria will be described for the sake of simplicity, but in the case of anaerobic methanogens, the second underground pipe 12 and the fourth underground pipe 22 are used. The only difference is that the method is different, and the other contents are the same as in the case of anaerobic hydrogen-producing bacteria.

In addition, since these pumping steps are performed by the pump P provided in the first well apparatus 2, oxygen in the air is not mixed into the groundwater.

The organic matter mixing step is a step of adding (mixing) glucose, which is a specific organic matter, to the groundwater supplied to the organic matter mixing device 5 . In this organic substance mixing step, when the biogas generation step has not been performed, as shown in FIG. Although it is performed on groundwater, after passing through the biogas generation process, it is performed on groundwater from which biogas has been extracted by the gas extraction device 4 .

In the organic matter mixing step, as described above, potato skins Z, which are food residues, are added to groundwater and stirred, and after cellulose is extracted from the potato skins Z, the groundwater is filtered and degassed. Cellulose addition (mixing) is done using the masterbatch groundwater. In this way, by using groundwater, which originally has a significantly low oxygen concentration, as water for extracting cellulose, costs can be reduced compared to the case where water is prepared separately.

In the mixed groundwater circulation process, the groundwater to which glucose has been added (mixed) in the organic matter mixing process is passed through the second well device 3 and the third underground pipe 21 (the fourth underground pipe 22 in the case of anaerobic methanogens). Circulate to the groundwater layer. At this time, the groundwater is agitated by the pump P of the second well device 3 to homogenize the concentration of the added glucose.

At the start of the mixed groundwater circulation process, as described above, the pump P of the second well apparatus 3 is turned on so that the insides of the third underground pipe 21 and the fourth underground pipe 22 are filled with groundwater. Processing such as reverse rotation is executed.

In the biogas generation process, glucose is added (mixed) and the groundwater circulated to the groundwater layer is left in the groundwater layer for a predetermined generation period, and biogas is produced by anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria. It is a process of generating hydrogen gas and methane gas, and the period of time during which these are left to stand may be determined according to the temperature of the groundwater layer, the types of anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria contained in the groundwater, etc. , For example, the period in which glucose is added (mixed) to anaerobic hydrogen-producing bacteria and anaerobic methanogens on the ground to generate biogas. 1 to 7 days if the groundwater temperature is relatively low, 3 to 14 days if the groundwater temperature is relatively low. If the temperature is relatively low, it may be 2 weeks to 60 days.

After the generation period has passed in the biogas generation process, the groundwater pumping process is executed again to pump up the groundwater.

Then, the groundwater pumped up in the groundwater pumping process is supplied to the gas extraction device 4 to extract hydrogen gas and methane gas, which are biogases, from the groundwater (biogas extraction process).

In addition, since the groundwater from which the biogas is extracted by these biogas extraction processes contains anaerobic hydrogen-producing bacteria and anaerobic methanogens that proliferated in the biogas production process, these proliferated anaerobic hydrogen-producing bacteria and anaerobic By reusing the methanogenic bacteria, biogas can be generated effectively, so that the biogas is again supplied to the organic matter mixing device 5 and the organic matter mixing step is performed to add (mix) glucose.

In this case, the amount (weight) of glucose to be added (mixed) to a unit volume (1 liter) of groundwater, that is, the concentration (volumetric concentration) of glucose in the groundwater after addition (mixing) is the amount of glucose initially added. Make the concentration higher than the concentration corresponding to (weight). In other words, the number of anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria per unit volume in the groundwater pumped up for the first time is relatively small because there is no growth due to the addition of glucose. Therefore, even if a large amount of glucose is added to groundwater with a relatively small number of bacteria per unit volume to increase the concentration, the bacteria cannot decompose the glucose, and surplus undecomposed glucose is generated. There is a fear that this glucose will lead to the growth of other bacteria and reduce the activity of anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria. Therefore, at first, the glucose concentration (volume concentration) is relatively low, for example, 1 to 3 g / L, and the glucose concentration (volume concentration) is gradually increased according to the number of times the biogas generation process has passed, for example, By increasing it to about twice the previous level, it becomes possible to efficiently generate biogas by the grown anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria while suppressing the influence of undecomposed glucose.

The generation period of the biogas generation process can be shortened as the number of anaerobic hydrogen-producing bacteria and anaerobic methanogen-producing bacteria per unit volume increases.

As described above, according to the present embodiment, groundwater containing anaerobic hydrogen-producing bacteria and anaerobic methanogens, which are biogas-producing bacteria, is pumped up from the groundwater layer. Anaerobic hydrogen generation by returning groundwater mixed with organic matter to the original groundwater layer in a low-oxygen atmosphere so that the anaerobic hydrogen-producing bacteria and anaerobic methanogens do not die or decrease Since hydrogen gas and methane gas, which are biogases, are generated by bacteria and anaerobic methanogens, the temperature and low-oxygen environment where anaerobic hydrogen-producing bacteria and anaerobic methanogens can generate hydrogen gas and methane gas on the ground are required. Since the cost for maintaining the can be reduced, hydrogen gas and methane gas, which are biogases, can be produced at low cost.

Further, according to the present embodiment, since the masterbatch groundwater containing a high concentration of glucose, which is a specific organic substance, is degassed and glucose is added (mixed) to the groundwater, by mixing glucose containing oxygen, It is possible to prevent anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria from dying out or decreasing.

Further, according to the present embodiment, the groundwater that has been pumped up in the groundwater pumping step and subjected to the biogas extraction step is mixed with glucose again in the organic substance mixing step, and then circulated to the groundwater layer in the mixed groundwater circulation step. is repeated, and the volume concentration of the specific organic matter is gradually increased with each repetition. Therefore, by mixing a high concentration of glucose (specific organic matter) at once, anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria are generated. Glucose (specific organic matter) that cannot be processed causes bacteria other than anaerobic hydrogen-producing bacteria and anaerobic methanogens to grow in the groundwater layer, reducing the activity of anaerobic hydrogen-producing bacteria and anaerobic methanogens. It is possible to prevent the generation of hydrogen gas and methane gas from being adversely affected by the addition of glucose (specific organic matter), and to reuse anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria that have grown due to the addition of glucose (specific organic substances). It can also produce gas and methane gas.

In addition, according to the present embodiment, since glucose (specific organic matter) is extracted from potato skin Z, which is food residue, high-quality glucose (specific organic matter) necessary for generating hydrogen gas and methane gas can be obtained at low cost. can do.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and any changes or additions within the scope of the present invention are included in the present invention. be

For example, in the above-described embodiment, glucose (specified organic substance) is added again to the groundwater from which the biogas has been extracted, and the biogas-producing bacteria can be effectively used by circulating the groundwater into the groundwater layer. However, the present invention is not limited to this, and the groundwater from which these biogases have been extracted may be circulated to the groundwater layer without adding glucose (specific organic matter).

Further, in the above embodiment, the groundwater pumping process, the organic matter mixing process, and the mixed groundwater circulation process are performed only once before the biogas generation process, but the present invention is limited to this. Instead, for example, before the biogas generation step, the groundwater pumping step, the organic matter mixing step, and the mixed groundwater circulation step may be performed in multiple steps. It is preferable to gradually increase the concentration of organic matter) such that the first time < the second time < the third time, and so on.

In addition, in the above embodiment, cellulose is extracted from potato skin Z, which is food residue, but the present invention is not limited to this, and the cellulose is extracted from other food residue It may be extracted from other than food residue.

In addition, in the above-described embodiment, a form in which cellulose is used as the specific organic substance is exemplified, but the present invention is not limited to this. may be a single organic matter extracted from sewage sludge, or a mixture of cellulose and organic matter extracted from sewage sludge, in which biogas-producing bacteria are capable of producing biogas and are not dissolved or precipitated in groundwater. , and one or more of them can be selected as appropriate. However, since various germs are attached to the organic matter extracted from the sewage treatment sludge, it is preferable to remove these germs before adding (mixing) it to the groundwater.

In the above embodiment, hydrogen gas-producing bacteria or methane gas-producing bacteria are exemplified, but the present invention is not limited to these, and biogas-producing bacteria other than these hydrogen gas-producing bacteria or methane gas-producing bacteria are used. There may be.

In addition, in the above-described embodiments, measuring devices such as a flow meter and a concentration meter are not shown in FIG. 1 and FIG. Needless to say, the adjustment and control may be performed while measuring the concentration of the specific organic matter.
In the above embodiment, the first well apparatus 2 pumps up either groundwater containing anaerobic hydrogen-producing bacteria or groundwater containing anaerobic methanogens, but the present invention is limited to this. For example, by providing a fifth underground pipe extending to a groundwater layer containing neither anaerobic hydrogen-producing bacteria nor anaerobic methanogens and having a low oxygen concentration, By pumping up the layer, for example, anaerobic hydrogen-producing bacteria and anaerobic methanogens collected from the ground, anaerobic hydrogen-producing bacteria and anaerobic methanogens cultured on the ground, etc. are added to these, You may make it circulate in the ground.

In the above embodiment, the specific organic matter is added (mixed) to the pumped groundwater in a low-oxygen atmosphere, and then immediately circulated to the groundwater layer, but the present invention is not limited to this. Groundwater to which organic matter has been added (mixed) is temporarily cultured and grown in a culture tank, and then the groundwater in which anaerobic hydrogen-producing bacteria and anaerobic methanogenic bacteria have increased is circulated to each groundwater layer. may

In addition, in the above-described embodiment, only the specific organic matter is added to the groundwater, but the present invention is not limited to this, and biogas can be generated from the specific organic matter together with these specific organic matter. anaerobic biogas-producing bacteria may be added together, and these anaerobic biogas-producing bacteria may be cultured in advance on the ground. In this way, the anaerobic biogas-producing bacteria pre-cultured on the ground are added (mixed) to the groundwater in addition to the anaerobic biogas-producing bacteria temporarily cultured in the above-described culture tank. good too.

1 biogas generation system 2 first well device 3 second well device 4 gas extraction device 5 organic substance mixing device 41 extraction tank 42 deaeration tank 43 deaeration device 49 filtration device P pump

Claims (6)

A method for producing biogas using biogas-producing bacteria that produce biogas in an anaerobic atmosphere,
a pumping step of pumping up the groundwater of the groundwater layer containing the biogas-producing bacteria so as not to mix oxygen in the air;
The groundwater pumped up in the pumping step is mixed with a specific organic substance capable of generating gas by decomposition by biogas-producing bacteria contained in the groundwater in a low-oxygen atmosphere with a predetermined oxygen concentration lower than the oxygen concentration in the air. a mixing step of
A circulation step of returning the groundwater mixed with the specific organic matter in the mixing step to the groundwater layer so as not to mix with oxygen in the air;
a biogas extracting step of extracting biogas from the groundwater layer after a predetermined generation period corresponding to the biogas-producing bacteria has passed since the circulation step;
A method for producing biogas, comprising: A degassing step of degassing a high-concentration liquid mixed with the specific organic matter at a concentration higher than the concentration of the specific organic matter in groundwater after the mixing step,
2. The biogas generation method according to claim 1, wherein in the mixing step, the specific organic matter is mixed using the high-concentration liquid degassed in the degassing step. The pumping step, the mixing step, and the reflux step are repeatedly performed at predetermined intervals,
3. The method for generating biogas according to claim 1, wherein the concentration of the specific organic matter mixed in the mixing step is gradually increased for each repetition. The biogas generation method according to any one of claims 1 to 3, wherein the groundwater from which the biogas is taken out by pumping in the pumping step is reprocessed by the mixing step and the reflux step. The method for producing biogas according to any one of claims 1 to 4, wherein the biogas-producing bacteria are hydrogen gas-producing bacteria or methane gas-producing bacteria. The method for producing biogas according to any one of claims 1 to 5, wherein the specific organic matter is glucose extracted from food residue.

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