JP2015025172A - Circulatory bio hydrogen production facility using biomass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve, by targeting a hydrogen production method for producing, from a raw ingredient consisting of biomass such as ligneous biomass, etc., hydrogen by exploiting a microorganism function, the hydrogen generation yield and hydrogen generation speed.SOLUTION: In the case of ligneous biomass known as representative biomass, hydrogen is generated by using, as hydrogen fermentation substrates, a hemicellulose degradation product and a cellulose degradation product obtained by treating the ligneous biomass. Moreover, hydrogen is produced by using, together with a microorganism electrolytic cell, a fermentation liquid including, as main components, organic acids such as acetic acid, etc. generated as a result of hydrogen fermentation. An electrolytically modified carbon electrode rather than a platinum catalyst electrode is used as a cathode of the microorganism electrolytic cell for generating hydrogen. It accordingly becomes possible to significantly improve the hydrogen generation yield and hydrogen generation speed, to abate the hydrogen production cost, and to realize a resource-circulatory hydrogen production plant using, as a raw ingredient, recyclable ligneous biomass.

Description

The present invention relates to a circulating biohydrogen production facility that uses biomass such as woody biomass, which is a renewable resource, as a raw material.

A conventional representative method for producing biohydrogen has been a method in which organic matter such as biomass is subjected to hydrogen fermentation using microorganisms. (For example, see Document 1 and Document 2)

However, in conventional biohydrogen production, the efficiency of hydrogen production from organic acids using photosynthetic bacteria, which is indispensable in the final stage of microbial treatment, is low, and the energy conversion efficiency is far inferior to bioethanol. The development of the hydrogen production process using organic acids has been an issue.

Under such circumstances, Logan et al. Of the University of Pennsylvania have a hydrogen production yield of 3.65 in hydrogen production using a microbial electrolysis cell (synonymous with a microbial electrolysis cell, hereinafter referred to as microbial electrolysis cell) using acetic acid as a substrate
Mol H ₂ / mol acetate, a hydrogen production rate of 46 mL / L / h was reported and a great response was received (Reference 3).

The results of Logan et al. Strongly suggest that hydrogen production from woody biomass may exceed the efficiency of bioethanol as an energy production efficiency by using a system that combines a hydrogen fermentation process and a microbial electrolysis cell ( Reference 4).

However, in the microbial electrolysis cell of Logan et al., Since a platinum catalyst electrode is used as a hydrogen generation electrode, there has been a problem in terms of cost when deployed to an actual plant.

At present, biohydrogen lags behind deployment in actual plants compared to bioethanol, but hydrogen can be converted into electric energy in combination with fuel cells, so it can be used for electric vehicles and power generation. There is great expectation as a new renewable energy, and there has been a demand for the development of biohydrogen production technology that can be applied to actual plants that achieve energy conversion efficiency equivalent to or higher than that of bioethanol.

“Asian Biomass Handbook -Guide for Utilization of Biomass-” “Asia Environmental Conservation Agricultural Partnership Support Project 2007 (Project commissioned by the Ministry of Agriculture, Forestry and Fisheries)” Japan Energy Society Editorial Board Chair Shinya Yokoyama (University of Tokyo) Yukihiko Matsumura (Hiroshima University Graduate School) W. M. Alalayah et al .: “Bio-HydrogenProduction Using a Two-Stage Fermentation Process”, Pakistan Journal of Biological Sciences, 12 (22), 1462-1467 (2009). S. Cheng and B. E. Logan: “Sustainable and efficient biohydrogen production via electrohydrogenesis”, Proc. Natl. Acad. Sci. USA, 104, 18871-18873 (2007). P.-C.Maness et al .: “Fermentation and Electrohydrogenic Approaches to Hydrogen Production”, DOE Hydrogen Program FY 2010 Annual Progress Report.

The conventional biohydrogen production method is a method in which organic matter such as biomass is fermented using microorganisms, but the efficiency of hydrogen production from organic acids using photosynthetic bacteria, which is indispensable in the final stage of microbial treatment, is high. Low, improvement of hydrogen production yield and hydrogen production rate of hydrogen production process using organic acid has been a technical issue.

The improvement of the efficiency of hydrogen production process using organic acid is achieved by using a microbial electrolysis cell with an electrode on which a microorganism capable of assimilating organic acid is immobilized as an anode and a hydrogen catalyst electrode as a cathode. This is achieved by using it as an electron donor for the anode. However, in the conventional microbial electrolysis cell, since a platinum catalyst electrode is used as a hydrogen generation electrode, there has been a problem in terms of cost when deployed to an actual plant.

Therefore, the present invention solves the above-mentioned problems, and by constructing a novel microbial electrolysis cell using an electromodified carbon electrode having a hydrogen generation catalytic ability instead of a platinum catalyst electrode at the cathode of the microbial electrolysis cell, the cost is reduced. The first object is to overcome the problems described above and dramatically improve the hydrogen production yield and hydrogen production rate compared to the hydrogen conversion of organic acids using photosynthetic bacteria.

In addition, the present invention solves the above-mentioned problem, and by combining hydrogen production by microorganisms with hydrogen production by microbial electrolysis cells, a circulating biohydrogen production facility using renewable resources such as woody biomass as a raw material is provided. This is the second purpose.

The present invention achieves the above first object as follows. The invention described in claim 1 is characterized in that an electrolytically modified carbon electrode having a hydrogen generation catalytic ability is used as a cathode of a microbial electrolysis cell.

The electrolytically modified carbon electrode is produced by covalently bonding a nitrogen-containing functional group such as an amino group to a carbon atom on the surface of carbon, and subjecting this to an electrolytic reduction treatment in a strong acid such as sulfuric acid.

The present invention also achieves the above second object as follows. A circulatory hydrogen production facility is realized by using the microbial electrolysis cell according to claim 1 and the organic material supplied to the anode using the treated biomass as a renewable resource according to claim 2. It is.

A method for treating biomass utilizes hydrogen fermentation of microorganisms according to claim 3 to produce biohydrogen from biomass and to generate an organic acid that is a main component of the fermentation liquid after hydrogen fermentation. This organic acid is supplied to the anode of the microbial electrolysis cell, and hydrogen is generated at the cathode.

The processing method in the case of using the woody biomass according to claim 4 uses high-temperature and high-pressure water treatment, enzyme treatment and microbial treatment to convert the woody biomass into sugar and organic acid, and the sugar is biodegradable by hydrogen fermentation according to claim 4. It is converted to hydrogen and an organic acid, and the organic acid is converted to hydrogen by a microbial electrolysis cell.

The organic acid produced by the high-temperature and high-pressure water treatment of the woody biomass is converted into hydrogen by the microbial electrolyzer as described in claim 5.

The insoluble component that cannot be converted into a solubilized component of sugar and organic acid by high-temperature and high-pressure water treatment of woody biomass is a substrate for microbial hydrogen fermentation by solubilizing it as a sugar by treatment with cellulase as described in claim 6. It becomes possible.

Moreover, the said insoluble component can be used as a raw material of a hydrogen fermentation means using the hydrogen producing microbe which has a cellulolytic enzyme as described in Claim 7.

According to the present invention, a hydrogen generation yield is achieved by a novel system in which a hydrogen fermentation by microorganisms and a microbial electrolysis cell using an electro-modified carbon electrode as a cathode are combined using a renewable resource such as woody biomass as a raw material. In addition, the hydrogen generation rate has been dramatically improved, and a recycling-type hydrogen production facility that can produce biohydrogen with higher energy conversion efficiency than bioethanol has become possible.

As described above, in the present invention, in the case of biomass hydrogen fermentation and microbial electrolysis cell treatment, in the case of woody biomass, a combination of a high temperature / high pressure water treatment process and hydrogen fermentation and microbial electrolysis cell treatment, each treatment process By optimizing the above, there is an effect that biohydrogen production can be realized with higher energy conversion efficiency than bioethanol.

Furthermore, the use of an electrolytically modified carbon electrode as the hydrogen generation electrode of the microbial electrolysis cell eliminates the need for an expensive platinum catalyst electrode, thereby overcoming the cost issues essential for actual plant development. effective.

Furthermore, by connecting the circulating biohydrogen production facility of the present invention with a fuel cell power generation system, there is an effect that natural energy power generation using a renewable resource called biomass becomes possible.

Furthermore, it is possible to effectively utilize the thermal energy in the integrated facility by integrating the heat and power generation between the electricity and thermal cogeneration facility using woody biomass and the circulating biohydrogen production facility using woody biomass. effective.

        The configuration of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a cell configuration and electrode electron transfer reaction of a microbial electrolysis cell according to the present invention.

An electrolytically modified carbon electrode according to the present invention was used for the cathode of the microbial electrolysis cell, and an aminated carbon electrode having a positive charge on the electrode surface was used for the anode in order to promote microbial immobilization.

Electrogenic bacteria capable of electron transfer with the electrode were immobilized on the anode. Electrogenic
Various microorganisms are known as bacteria, but here, representative Electrogenic
The bacteria Geobacter sulfurreducens was used.

The substrate that serves as the electron donor for the anode of the microbial electrolysis cell can be a wide variety of organic substances as long as it is an organic substance that can be assimilated by Electrogenic bacteria. An electrode electron transfer reaction was shown using an acetic acid as an example. Eight electrons from 1 mole of acetic acid are passed to the anode, producing 2 moles of CO ₂ . On the other hand, at the cathode, the generated eight electrons are transferred to protons, which are electron acceptors, to produce hydrogen. In this hydrogen-generating electron transfer reaction, the reaction rate is determined by the potential difference between the cathode potential and the redox potential of the proton that is the electron acceptor, so the net energy conversion efficiency of the electrode electron transfer reaction that generates hydrogen from acetic acid is maximized. In order to perform efficient electron transfer, it is necessary to apply a voltage between the power source and the electrode. In the case of acetic acid, a voltage application of 0.6 V is optimal.

FIG. 2 shows a biohydrogen production process in a circulating biohydrogen production facility using woody biomass as a raw material.

The components produced by the high-temperature / high-pressure water treatment step 1 in the circulating biohydrogen production facility are hemicellulose degradation products, the main components are xylose and its oligosaccharides, and microorganisms capable of hydrogen fermentation of xylose compounds with high efficiency ( For example Thermoanaerobacterium
thermosaccharolyticum or Thermotoga
neapolitana etc.) to produce biohydrogen through hydrogen fermentation. The fermented liquid after hydrogen fermentation is mainly composed of organic acids such as acetic acid and lactic acid, and is supplied as an electron donor for the anode of the microbial electrolysis cell, and biohydrogen is produced from the cathode.

The component produced by the high temperature / high pressure water treatment step 2 in the circulating biohydrogen production facility is a cellulose degradation product, and the main component is cellulose remaining as an insoluble matter without being solubilized with glucose and its oligosaccharide. In order to use the components produced in this high-temperature / high-pressure water treatment step 2 as a substrate for hydrogen fermentation, a hydrogen-producing bacterium having an enzyme that decomposes cellulose (for example, Costridium).
thermocellum and Thermoanaerobacterium
thermosaccharolyticum etc.) is used to saccharify cellulose, which is an insoluble matter, and biohydrogen is produced by subsequent hydrogen fermentation. Organic acids such as acetic acid and lactic acid contained in the fermentation liquid after hydrogen fermentation are supplied as an electron donor for the anode of the microbial electrolysis cell, and biohydrogen is produced from the cathode.

The treatment conditions for high temperature / high pressure water treatment step 1 are 140-230 ° C, temperature and pressure conditions of 0.1-10MPa, and the treatment conditions for high temperature / high pressure water treatment step 2 are temperatures of 230-270 ° C, 0.1-10MPa. -Pressure conditions. The treatment time for high temperature / high pressure water treatment is in the range of 2-60 minutes.

As described above, in the circulating biohydrogen production facility shown in FIG. 2, hemicellulose components (xylose and its oligosaccharides are the main components) and cellulose are obtained by using high-temperature and high-pressure water treatment using woody biomass as a starting material and temperature and pressure as basic parameters. Ingredients (glucose and its oligosaccharides and cellulose remaining as insoluble components) are produced. This process is a cascade process and consists of two steps. As a first step, a hemicellulose component is extracted, and as a second step, a cellulose component is produced. Glucose and xylose are converted to hydrogen by a microbial fermentation process. Fermentation liquid mainly composed of organic acid such as acetic acid produced in hydrogen fermentation process is used as an electron donor for microorganism-immobilized electrode (anode) of microbial electrolysis cell, and hydrogen is produced at the cathode by electrode electron transfer reaction. Is done.

A platinum catalyst electrode is not used as the cathode for generating hydrogen in the microbial electrolysis cell, but an electrolytically modified carbon electrode is used. This realizes a dramatic improvement in hydrogen production yield and hydrogen production rate compared to hydrogen conversion of organic acids using photosynthetic bacteria, which is due to the problem of cost and carbon monoxide when using platinum catalyst electrodes. The problem of electrode poisoning was solved at the same time.

In Example 2 shown in FIG. 2, although it is the structure which performs two types of hydrogen fermentation using different microorganisms corresponding to each of the component produced | generated by two steps of high temperature / high pressure water treatment, It is also possible to produce biohydrogen by hydrogen fermentation using a hydrogen producing bacterium having an enzyme that decomposes cellulose by introducing components produced in one step together into one hydrogen fermentation tank.

Fig. 3 shows the high-temperature and high-pressure water treatment process flow and thermal energy flow (black arrows) when the circulating biohydrogen production facility is in thermal cooperation with an electric / thermal cogeneration facility that uses woody biomass as a raw material. .

As shown in the figure, in a circulating biohydrogen production facility, there is a process of treating raw materials at high temperature and high pressure water, and a large amount of heat energy is required. This thermal energy is supplied by the flow of hot water from heat exchangers A and B as indicated by the black arrows in the figure. Since the required temperature conditions are different in each process of the circulating biohydrogen production facility, the flow of high-temperature water is not shown in the figure, but a predetermined temperature required in each process by the temperature controller. Supplied by adjusting the temperature.

In the figure, soluble component 1 is mainly a hemicellulose degradation product, insoluble component 1 is mainly cellulose and lignin, soluble component 2 is mainly a cellulose degradation product, and insoluble component 2 is mainly Cellulose and lignin.

The figure shows the process of wood biomass in the circulating biohydrogen production facility that is largely related to the thermal cooperation with the electric / thermal cogeneration facility. There are a plurality of hydrogen fermentation facilities that require this heat, and the heat energy required in these facilities is supplied by high-temperature water indicated by black arrows in the figure. The high-temperature water supplied in this way is used after being adjusted to a predetermined temperature by a temperature controller.

Electrobium Electron Transfer Reaction Using Microbial Electrolyzer Configuration and Acetic Acid as Anode Substrate Showing Embodiment of the Present Invention Overall configuration diagram of a circulating biohydrogen production facility showing an embodiment of the present invention Thermal energy flow between an electrical / thermal cogeneration facility and a refinery facility for hydrogen production in a circulating biohydrogen production facility showing an embodiment of the present invention (black arrow)

Claims (9)

In an electrolytic cell having a functional structure in which an organic substance such as glucose or acetic acid that can be metabolized by microorganisms is used as an anode for an anode of an electrolytic cell that generates hydrogen, and an immobilized microorganism electrode on which microorganisms are immobilized. A microbial electrolyzer characterized by using an electrolytically modified carbon electrode having hydrogen-catalyzing ability. A circulation type hydrogen production facility comprising means for supplying an organic substance to be supplied to an anode of a microbial electrolytic cell according to claim 1 from biomass, and producing hydrogen from biomass. A circulating hydrogen production facility characterized in that hydrogen fermentation using a microbial function is used as means for converting biomass into organic matter according to claim 2. Means for separating and extracting the hemicellulose component and the cellulose component from the woody biomass, and first and second hydrogen fermentation means for producing hydrogen using a catalytic function derived from a microorganism using each component extracted from the separation and extraction means, And comprising the microbial electrolyzer according to claim 1, wherein hydrogen is produced from woody biomass by supplying a fermentation solution produced from the first and second hydrogen fermentation means to the anode of the microbial electrolyzer. Circulating hydrogen production facility. 5. The circulating hydrogen production facility according to claim 4, wherein an organic substance separated and extracted from the separation and extraction means in addition to the fermentation liquid produced in the first and second hydrogen fermentation means as an organic substance of the anode of the microbial electrolysis tank. A recycling-type hydrogen production facility characterized by using an acid. 5. The circulating hydrogen production facility according to claim 4, wherein an insoluble component mainly composed of cellulose separated and extracted from the separation and extraction means is solubilized using cellulase and used as a raw material for the second hydrogen fermentation means. A recycling-type hydrogen production facility characterized by 5. The circulating hydrogen production facility according to claim 4, wherein an insoluble component mainly composed of cellulose separated and extracted from the separation and extraction means is used as a raw material for the second hydrogen fermentation means using hydrogen-producing bacteria having cellulolytic enzymes. A recycling-type hydrogen production facility characterized by the use. A circulating hydrogen production facility characterized in that the first and second hydrogen fermentation means according to claim 4 are the same hydrogen fermentation means. The circulating hydrogen production facility according to claim 8, wherein the hemicellulose component and the cellulose component are integrally extracted without being separated and extracted and supplied to the same hydrogen fermentation means.