JP5334077B2 - Method for producing hydrogen from biomass - Google Patents

Description

  The present invention relates to a technique for producing hydrogen gas using biomass. Technology that uses the heat resistance inherent in hydrogen-producing bacteria and suppresses hydrogen decomposition and consumption by hydrogen-utilizing bacteria such as methane-producing bacteria that inhibit hydrogen production, and stably obtains hydrogen by simple means and equipment Related to.

  From the viewpoint of resource recycling, wastes such as livestock excrement and food residues are effectively used as biomass resources, and in addition to recovering them as valuable resources, there is a need for efficient use as energy. It is growing. In recent years, as a raw material for producing ethanol and biodiesel, there has been an increase in the cultivation of crops called energy crops such as sugar cane and rapeseed.

  It has been well known that methane is produced from these biomasses by treating them with methane fermentation. However, since methane gas changes to carbon dioxide and carbon monoxide during combustion, it is treated as an unfavorable substance as a cause of global warming today. In contrast, hydrogen that does not pollute the air during combustion is not only concerned about global warming, but is also attracting attention as a next-generation energy with a low load on the environment.

  However, in the prior art, recovering methane from discarded organic substances is the fundamental method of resource recovery, and it was not intended to produce hydrogen. And the idea of producing hydrogen from biomass with high efficiency in anticipation of environmental problems, especially global warming, is extremely modern.

  Therefore, it can be said that it is a request of the times to produce hydrogen gas instead of the classic technology that focuses on obtaining methane gas from waste such as livestock excreta.

  As a means of producing hydrogen using anaerobic microorganisms, a method that uses pure hydrogen-producing bacteria alone and a mixed microorganism group as it is without purification of microorganism groups contained in activated sludge, compost, etc. There is a method to use as. Means using pure bacteria require substrate sterilization and heat sterilization of biomass as a raw material, a large amount of energy must be input, and it is difficult to apply to waste such as livestock excrement. On the other hand, the latter method using the mixed microorganism group does not require substrate restrictions or sterilization of raw materials, and has an advantage of wide application range.

Livestock excrement, compost, activated sludge and anaerobic treatment tank sludge contain a wide variety of microorganisms such as hydrogen producing bacteria and methane bacteria. Furthermore, since the microorganisms contained in them are difficult to culture alone, they are composed of many unknown microorganisms that have not yet been identified. Since fermentation such as methane fermentation and hydrogen fermentation requires anaerobic conditions, among the various microorganism groups contained in livestock excrement, compost, activated sludge and anaerobic treatment tank sludge, the microorganism group related to fermentation is a complex anaerobic It can be said that it is a sex microorganism group.
It has been found that hydrogen is temporarily produced in the initial stage of methane fermentation. However, when methane fermentation is continued, hydrogen is eaten by methane-producing bacteria, and it has been known that it is actually very difficult to recover hydrogen gas.

  Naturally, as anaerobic microorganisms, there are both hydrogen-utilizing bacteria such as methane producing bacteria and hydrogen producing bacteria, which act on biomass. A considerable amount of hydrogen is produced at the beginning of the fermentation, but the generated hydrogen is eaten one after another by hydrogen-utilizing bacteria. In other words, the methane-producing bacteria carried in the anaerobic bioreactor coexist with the hydrogen-producing bacteria, and methane is efficiently produced from hydrogen.

  Methane is not the only hydrogen-utilizing bacterium that decomposes and consumes hydrogen. Homoacetic bacteria also eat hydrogen. Therefore, if conditions that suppress the action of consuming hydrogen of these hydrogen-assimilating bacteria can be maintained, hydrogen should be stably extracted.

  From this point of view, a technique is disclosed in which an agent that inhibits the methyl reductase enzyme possessed by methane-producing bacteria is added so that hydrogen is not consumed (Japanese Patent Laid-Open No. 4-346788).

  In addition, focusing on the fact that hydrogen-producing bacteria are active in the initial stage of methane fermentation, a technique is disclosed that can obtain a certain amount of hydrogen by quickly separating hydrogen outside the bioreactor device. (Unexamined-Japanese-Patent No. 2002-272491).

  However, unsolved problems remain in the described technique. For example, even if an additive that inhibits the methyl reductase enzyme of a methane-producing bacterium is added, if a homoacetic acid bacterium is present, hydrogen is consumed by the hydrogen-assimilating bacterium. Preparing each enzyme-inhibiting additive for each hydrogen-consuming bacterium is not a good idea and increases production costs.

An overview of technologies related to hydrogen production
(A) A pure culture system in which biomass as a raw material is heat-sterilized and inoculated with a purified hydrogen-producing bacterium, and the fermentation temperature is usually 50 to 60 ° C. and the fermentation temperature is 20 to 40 ° C. And high temperature fermentation.
(B) A complex culture system using a group of microorganisms composed of various microorganisms (hereinafter, sometimes referred to as a complex anaerobic microorganism group), wherein the hydrogen-producing bacteria are heat-resistant, and the fermentation temperature Is a high-temperature hydrogen fermentation that is carried out at 50 to 60 ° C. In this case, there is an advantage that sterilization of the raw material is not necessary.
(C) Pretreatment by heat treatment (60-90 ° C) or boiling to the complex anaerobic microorganism group to sterilize and suppress heat-sensitive hydrogen-assimilating bacteria and concentrate and use the heat-resistant hydrogen-producing bacteria group There is a technique to do. In this technique, after the pretreatment, the culture solution is maintained at a medium temperature of fermentation at 20 to 40 ° C. or at a high temperature of 50 to 60 ° C. to carry out hydrogen production. In this method, the purpose of heating the raw material to 60 to 90 ° C. is merely a pretreatment, and does not generate hydrogen at this temperature.
JP 08-305991 A JP 08-294396 A JP 08-252089 A JP 07-031484 A JP 2002-272491 A JP 2005-013045 A JP 2003-135089 A

  In order to realize stable hydrogen fermentation from biomass, the activity of hydrogen-producing bacteria such as methane-producing bacteria that consume hydrogen generated by some method is maintained while maintaining the activity of hydrogen-producing bacteria that produce hydrogen. Must be suppressed. In consideration of adaptation to actual hydrogen production, it is an extremely important requirement that the method, operation and equipment of hydrogen fermentation are simple. In the method (A), there is no concern about hydrogen consumption by hydrogen-assimilating bacteria, but the raw materials used for fermentation must be sterilized, which increases costs and is difficult to apply in practice. Next, in the vicinity of the fermentation temperature of 50 to 60 ° C. in the method (B), it cannot be said that suppression of hydrogen-utilizing bacteria is complete. Further, the method (C) requires pre-processing, and there is a problem that the operation / device becomes complicated and complicated.

  The present invention solves the above-described problems, and produces hydrogen by a simple means and recovers it from biomass such as excrement such as manure of livestock and food residue.

The present inventor conducted a hydrogen fermentation experiment by using a slurry obtained by diluting livestock manure in water as a raw material and using the complex anaerobic microorganism group contained in the slurry as it is as a seed for fermentation. As a result, when it was heated to a high temperature of 70 to 90 ° C. beyond the conventionally known hydrogen fermentation temperature of 60 ° C., the second hydrogen production peak was surprisingly around the hydrogen fermentation temperature of 75 ° C. I found out that there exists.
Through this experiment, it has been clarified through experiments that hydrogen-utilizing bacteria such as methane bacteria no longer have the activity at this high temperature, and the generated hydrogen, which is an inhibiting factor of hydrogen fermentation, is not consumed. And when it reached 85 degreeC, it turned out that a hydrogen producing microbe also loses activity.

  In other words, the present invention allows hydrogen-producing bacteria, which have better heat resistance than hydrogen-utilizing bacteria, to function at a critical high temperature that can maintain the activity, and reduces and inactivates the activity of hydrogen-utilizing bacteria, It can be said that it is a technology to acquire.

  The specific solution is as follows.

The invention according to claim 1 uses organic matter as a raw material, and heats the raw material in anaerobic conditions for at least two days in the temperature range of 71 ° C. to 79 ° C. in the presence of a complex anaerobic microorganism group contained in livestock dung. This is a method for producing hydrogen using hydrogen fermentation.
When the raw material is animal dung, a complex anaerobic microorganism group derived from the digestive tract of livestock can be used as an inoculum for hydrogen fermentation. In the prior art, a hydrogen fermentation temperature of 60 ° C. or lower is used, but in the case of this temperature range, since the amount of hydrogen generation is large, the present invention seems to be disadvantageous at first glance. However, at a fermentation temperature of 60 ° C. or lower according to the prior art, once produced hydrogen is eaten and lost by hydrogen-utilizing bacteria, stable hydrogen production and recovery of generated hydrogen are difficult.

  The invention according to claim 2 exemplifies that in the hydrogen production method according to claim 1, the complex anaerobic microorganism group is any one of animal dung, compost, activated sludge and anaerobic treatment tank sludge. Yes.

The present invention does not add a specific hydrogen-producing bacterium and does not perform pretreatment. It does not increase or decrease the activity of specific hydrogen-producing bacteria in advance. In the present invention, it is not necessary to add a specific hydrogen-producing bacterium, and there is an advantage that the operation / device can be simplified. By only selecting the fermentation temperature, it is advantageous to have conditions that allow hydrogen-producing bacteria to be active relative to other anaerobic microorganisms. Therefore, hydrogen can be produced with extremely simple operation and equipment.
The invention according to claim 2 is a method for producing hydrogen, wherein the complex anaerobic microorganism group is any one of livestock excrement, compost, activated sludge and anaerobic treatment tank sludge.
The invention according to claim 3 is the method for producing hydrogen according to claim 1, wherein the organic material used as a raw material is a food residue such as livestock excrement, garbage, or an organic matter discharged from a food processing factory or a food handling workplace. This is a method for producing hydrogen, which is one of a group of energy crops including waste or waste liquid containing sugarcane.
The invention according to claim 4 uses animal feces as a raw material without adding an inoculum of hydrogen fermentation from the outside, and uses the complex anaerobic microorganism group contained in the animal feces as an inoculum as it is, more than 70 ° C. and less than 85 ° C. In this temperature range, the raw material is heated under anaerobic conditions for at least 2 days to promote hydrogen fermentation . In this case, since there are inoculums that promote hydrogen fermentation in the raw material, it is not necessary to add an inoculum for hydrogen fermentation. By heating to a predetermined temperature in a natural state, hydrogen can be produced and recovered.

The present invention will be described in detail.
Prior art hydrogen fermentation temperatures include medium temperature fermentation (20-40 ° C.) using pure bacteria and high temperature hydrogen fermentation (50-60 ° C.) using complex bacteria. The present inventor used a complex anaerobic microorganism group contained in livestock excrement as an inoculum of hydrogen fermentation to ferment the excrement raw material with hydrogen. As a result, the first hydrogen production was performed at a fermentation temperature of 50 to 60 ° C. Through experiments, it was found that there was a peak of hydrogen and that there was a maximum point of hydrogen production near 75 ° C. Therefore, the peak of this second hydrogen production activity was named “high-temperature high-temperature hydrogen fermentation (phenomenon)”. The results of this experiment are shown in the graph of FIG. The horizontal axis is the temperature of hydrogen fermentation, the vertical axis is the maximum hydrogen generation amount, and shows the fermentation temperature dependency of the hydrogen fermentation phenomenon. Although hydrogen consumption by hydrogen-utilizing bacteria is observed at the fermentation temperature of 50 to 60 ° C., which is a conventional technique, it has also been found that hydrogen consumption does not occur in advanced high-temperature hydrogen fermentation near the fermentation temperature of 75 ° C. (see FIG. 2 described later). ). As a result, it is possible to promote stable hydrogen production in 75 ° C. fermentation. In producing hydrogen, the present invention can omit the pretreatment of raw materials (treatment such as heat sterilization), and has a great advantage that hydrogen can be produced even with simple equipment.

  Fig. 1 uses cattle manure slurry as a raw material, a complex anaerobic microorganism group contained in the slurry as an inoculum, and these are used as they are without any modification at a fermentation temperature in the range of 37 to 85 ° C. It is the example which implemented hydrogen fermentation.

  Moreover, FIG. 2 is the graph which illustrated the generation amount of the production | generation hydrogen in hydrogen fermentation when 55 degreeC and 75 degreeC were selected as fermentation temperature as a time-dependent change. In short, this is a comparison of the hydrogen production behavior of the present invention (fermentation temperature 75 ° C.) and the prior art (55 ° C.). It was found that the hydrogen once generated was eaten by the hydrogen-assimilating bacteria. On the other hand, it is clear that culture at 75 ° C. impairs the activity of hydrogen-utilizing bacteria and does not lose the generated hydrogen. The generated hydrogen can be easily recovered and enables stable hydrogen production.

  In the hydrogen production method of the present invention, by suppressing the activity of hydrogen-utilizing bacteria such as methane-producing bacteria, it is advantageous in hydrogen production when biomass containing a large amount of hydrogen-utilizing bacteria such as livestock excreta is used as a raw material. Works. Further, in the method of the present invention, since a high fermentation temperature is adopted, when weed seeds or pathogenic microorganisms are contained in the biomass as a raw material, these harmful substances are sterilized by higher fermentation temperature than the conventional technology. Inactivation can be promoted. Therefore, it becomes advantageous for reuse of the liquid fertilizer etc. of the processing liquid after fermentation.

The method of the present invention utilizes “high-temperature high-temperature hydrogen fermentation (phenomenon)” of 71 ° C. to 79 ° C. as the fermentation temperature in the above configuration. From activated sludge, compost, digested sludge from anaerobic treatment tanks, or livestock manure, which are mixed with various microorganisms, from excreta including livestock manure, food residue, other waste, energy crops such as sugarcane It produces hydrogen.
In the prior art, a hydrogen fermentation temperature of 60 ° C. or lower is used. In this temperature range, although the amount of hydrogen produced is large at the beginning of fermentation, the generated hydrogen is eaten by hydrogen-utilizing bacteria such as methane producing bacteria. Therefore, it is apparent that the method of the present invention using “high-temperature high-temperature hydrogen fermentation (phenomenon)” is excellent.
In the present invention, a specific hydrogen-producing bacterium is not added, and no pretreatment is performed. It does not increase or decrease the activity of specific hydrogen-producing bacteria in advance. In the present invention, there is no need to add a specific hydrogen-producing bacterium, and there is an advantage that the operation / device can be simplified. By only selecting the fermentation temperature, it is advantageous to have conditions that allow hydrogen-producing bacteria to be active relative to other anaerobic microorganisms. Therefore, hydrogen can be produced with extremely simple operation and equipment.
When a complex anaerobic microorganism group originally exists in the raw material, such as animal manure, hydrogen can be easily produced and recovered by heating to a predetermined temperature in a natural state.

A complex anaerobic microorganism group consisting of various microorganisms is added from biomass such as livestock excrement and food residue. When a complex anaerobic microorganism group originally exists in the raw material, such as animal manure, the addition of the complex anaerobic microorganism group may be unnecessary.
When the raw material slurry mixed with this complex anaerobic microorganism group is heated under anaerobic conditions in a temperature range of 71 ° C. to 79 ° C. (particularly preferably about 75 ° C.), hydrogen fermentation occurs and hydrogen can be produced.

  When any one of livestock excrement, compost, activated sludge and anaerobic treatment tank sludge is used as the complex anaerobic microorganism group, hydrogen fermentation occurs.

  As raw materials, livestock excrement, food residues such as food waste, waste or waste liquid containing organic matter discharged from food processing factories or food handling workplaces, energy crops including sugar cane, etc. are applicable. Already contains a complex anaerobic microorganism group, so that hydrogen fermentation can be promoted by heating the raw material under anaerobic conditions in a temperature range of more than 70 ° C and not more than 85 ° C, so that hydrogen can be produced. .

<Example 1>
Using a bioreactor equipped with the simple heating device (including temperature control means) 42 shown in FIG. 3, using animal dung slurry as a raw material, a complex anaerobic microorganism group contained in the animal dung is used as a seed fungus at 75 ° C. The generation state of hydrogen gas was observed at the fermentation temperature.
In the bioreactor, a raw material slurry 40 containing a composite anaerobic microorganism group is input to the lower stage of the bioreactor 30 from a raw material input port 34, and the raw material slurry and the composite anaerobic microorganism group 40 are sufficiently stirred by a stirring means 32. The upper stage of the container main body has a configuration in which gas phase hydrogen gas can be stored in the hydrogen recovery gas holder 38 as soon as it accumulates. The raw slurry 40 can be discharged from the discharge port 36.
These observation results are as shown in FIG.
<Comparative Example 1>
The relationship between the incubation time and the amount of hydrogen produced was observed under the same conditions as in Example 1 except that the temperature was set to 55 ° C., which is the fermentation temperature of the prior art. The observation results are shown in FIG. It turned out that the amount of hydrogen was decreasing at the peak on the 4th day, which is a hydrogen-consuming bacterium consuming hydrogen.

It is a graph which shows the relationship between the fermentation temperature of hydrogen fermentation which used cattle manure slurry as a raw material, and the amount of hydrogen production. It is a graph which shows the relationship between the culture | cultivation time of hydrogen fermentation which used cattle manure slurry as a raw material, and the amount of hydrogen generation. It is a schematic diagram of the high temperature hydrogen fermentation apparatus used as the Example of this invention.

Explanation of symbols

30 Bioreactor 32 Stirring means 34 Raw material input port 36 Outlet port 38 Hydrogen recovery gas holder 40 Raw material slurry and complex anaerobic microorganism group 42 Heating device

Claims (4)

Utilizing an organic material as a raw material, utilizing hydrogen fermentation, comprising heating the raw material under anaerobic conditions for at least two days in the temperature range of 71 ° C. to 79 ° C. in the presence of complex anaerobic microorganisms contained in livestock dung Hydrogen production method.   The method for producing hydrogen according to claim 1, wherein the complex anaerobic microorganism group is any one of livestock excrement, compost, activated sludge, and sludge in an anaerobic treatment tank.   2. The organic material as a raw material is any one of a group of energy crops including waste or waste liquid containing organic matter discharged from a food processing factory or food residue such as livestock excrement, food waste, and sugarcane. How to produce hydrogen.   Without adding an inoculum of hydrogen fermentation from the outside, the animal dung is used as a raw material, the complex anaerobic microorganism group contained in the animal dung is used as a seed bacteria as it is, and the raw material is anaerobic in a temperature range of 70 ° C. to 85 ° C. A method for producing hydrogen comprising heating at least 2 days under conditions to promote hydrogen fermentation.

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