Method for producing hydrogen by fermentation of rumen microorganisms

Abstract

The invention discloses a method for producing hydrogen through rumen microorganism fermentation, and relates to the technical field of resources and environment. Comprising the following steps: inoculating fresh rumen fluid into a fermentation tank filled with a buffer solution according to a volume ratio of 5-10%, and after 24-36 hours, adding 10-30 g / L of biomass waste to start a fermentation reaction. When the content of H2 in a gas production component reaches 20%, the fermentation temperature is controlled to be 37-40 DEG C, the HRT is controlled to be 50-90 h, the SRT is controlled to be 6-10 d, the pH is controlled to be 5.5-6.0, biomass waste is added according to 1-3 g / L.d, the headspace pressure is kept to be 95 + / -5 kPa, and the system starts to continuously feed and discharge materials and feed and discharge water to produce hydrogen through fermentation. According to the method, cellulose biomass is used as a substrate, the hydrogen production amount is increased by 50-100% compared with that of a traditional anaerobic biological dark hydrogen production method, the retention time is shortened by 3-10 days, the hydrolysis, saccharification and hydrogen production processes can be achieved in the same reactor, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of resource and environmental technology, and in particular to a method for producing hydrogen by fermenting rumen microorganisms. Background Art

[0002] As a pollution-free and renewable fuel, hydrogen energy is regarded as one of the most promising renewable energy sources in the future. At present, the methods of hydrogen production include chemical methods, such as solar hydrogen production, water electrolysis hydrogen production, water gas reforming hydrogen production, and methane hydrogen production. Although many advances have been made in electrode research and industrial applications in recent years, these methods still face problems such as high production costs and the need for additional energy supply, so there is still a long way to go in future exploration. On the other hand, biological hydrogen production, especially photofermentation hydrogen production and anaerobic biological dark fermentation hydrogen production, is regarded as one of the most promising hydrogen production technologies due to its simple process, wide substrate sources and mild reaction conditions.

[0003] Rumen microorganisms are a general term for the microbial community in the rumen of ruminants, and they have excellent cellulosic biomass hydrolysis capabilities. These microorganisms can hydrolyze complex carbohydrates such as cellulose and hemicellulose into reducing sugars, and further convert reducing sugars into pyruvate through EMP, HMP or ED pathways, and then into substances such as volatile fatty acids. Due to differences between microbial communities, the degradation pathways of pyruvate are also different, among which butyrate fermentation, mixed fermentation and ethanol fermentation are the main pathways for anaerobic biohydrogen production. Studies have shown that among rumen microorganisms, Clostridium, as the main participant in butyrate fermentation, has a high hydrogen production capacity, while Ruminococcus and Bacteroides also show good hydrogen production potential. Therefore, the development of a hydrogen production method with rumen microorganisms as the core and the use of anaerobic biological dark fermentation technology is expected to effectively increase the reaction rate of the biohydrogen production system and enhance the potential for hydrogen production. Summary of the invention

[0004] The purpose of the present invention is to provide a method for producing hydrogen by fermentation of rumen microorganisms, which can convert cellulose biomass waste into hydrogen, improve the efficiency of biological hydrogen production, and reduce the cost of hydrogen production.

[0005] To achieve the above purpose, the technical solution of the present application is: a method for producing hydrogen by fermentation of rumen microorganisms, comprising:

[0006] Fresh rumen fluid is inoculated into a fermentation tank filled with a buffer solution. After a period of time, biomass waste is added to start the fermentation reaction. When the H2 content in the gas-producing component reaches the set value, the fermentation temperature, HRT, SRT, and pH range are controlled, and biomass waste is added to maintain the headspace pressure, and continuous material and water in and out fermentation and hydrogen production begins.

[0007] In one embodiment, fresh rumen fluid is inoculated into a fermenter containing a buffer solution at a volume ratio of 5-10%.

[0008] In one embodiment, after 24-36 hours, 10-30 g / L of biomass waste is added to start the fermentation reaction.

[0009] In one embodiment, when the H2 content in the gas-producing component reaches 20%, the fermentation temperature is controlled to be 37-40°C, HRT to be 50-90h, SRT to be 6-10d, and pH to be 5.5-6.0.

[0010] In one embodiment, biomass waste is added at 1-3 g / L·d, and the headspace pressure is maintained at 95±5 kPa.

[0011] In one embodiment, the buffer solution is prepared according to NaHCO3 5-10 mg / L, NaH2PO4 2-5 mg / L, KCl 0.3-0.5 mg / L, MgCl2 0.05-0.1 mg / L and CaCl2 0.3-0.5 mg / L, and after dissolution, it is exposed to CO2 gas for 3-5 minutes, and the pH of the buffer solution is adjusted to 5-6 using hydrochloric acid.

[0012] In one embodiment, the fresh rumen fluid is taken from the rumen of ruminants and contains microorganisms such as bacteria, fungi, archaea and bacteriophages.

[0013] In one embodiment, the biomass waste includes crop straw and vines such as corn, wheat, and reeds.

[0014] By adopting the above technical scheme, the present invention can achieve the following technical effects: using cellulose biomass as a substrate, the hydrogen production is increased by 50-100% compared with the traditional anaerobic biological dark hydrogen production method, the residence time is shortened by 3-10 days, the hydrolysis, saccharification and hydrogen production processes can be realized in the same reactor, and the production cost is reduced. DETAILED DESCRIPTION

[0015] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0016] Example 1: Prepare a buffer solution of 10 mg / L NaHCO3, 5 mg / L NaH2PO4, 0.5 mg / L KCl, 0.08 mg / L MgCl2 and 0.5 mg / L CaCl2, expose to CO2 gas for 5 minutes, and add hydrochloric acid to adjust the pH of the buffer solution to 5.5. Add 4700 mL of buffer solution to a 5L effective volume reactor, preheat to 37°C, add 300 mL of fresh rumen fluid, and simmer for 24 hours. Add 50 g of crushed yellow corn stalks and start stirring. The gas produced by fermentation was collected and the gas composition was continuously measured. When the H2 content reached 20%, corn straw was added at 12 g / d. The system fermentation temperature was controlled at 37°C, HRT was 80 h, SRT was 8 d, and pH was 5.5-6.0. The gas produced by fermentation was extracted using a vacuum pump to maintain the headspace pressure at 95±5 kPa. After about 25 days, the system was stable, the hydrogen production was stable at about 1600 mL / d, and the hydrogen production per gram weight reached about 150 mL / g·VS.

[0017] Example 2: Prepare NaHCO3 5 mg / L, NaH2PO4 2.5 mg / L, KCl 0.35 mg / L, MgCl2 0.05 mg / L and CaCl2 0.35 mg / L buffer solution, expose to CO2 gas for 3 minutes, add hydrochloric acid to adjust the pH of the buffer solution to 5.5. Add 50L of fresh rumen fluid and 450L of buffer solution to a 500L anaerobic fermentation tank at a volume ratio of 10%, heat to 39°C, and simmer for 30 hours. 7.5 kg of crushed reed straw was added at one time, the gas produced by fermentation was collected and the gas composition was continuously measured. When the H2 content reached 20%, crushed reed straw was added at 0.5 kg / d, the fermentation temperature of the system was controlled to be 39°C, HRT was 60 h, SRT was 6 d, and pH was 5.5-6.0. The gas produced by fermentation was extracted by a vacuum pump to maintain the headspace pressure at 95±5 kPa. After about 22 days, the system was stable, the hydrogen production was stable at about 90 L / d, and the hydrogen production per gram weight reached about 190 mL / g·VS.

[0018] Comparative Example 1: First, the straw was pretreated by the ammonia method, specifically: 40g of urea was dissolved in 400mL of water to prepare a 100g / L urea aqueous solution, evenly sprayed on 1kg of crushed corn straw, and placed in a closed pretreatment at 25°C for 60 days. The activated sludge from the anaerobic hydrolysis section of the anaerobic digestion project of a farm in Dalian was inoculated into a 5L anaerobic dark fermentation hydrogen production reactor at a sludge concentration of 6000mg / L, and the pretreated corn straw was added at 12g / d, and the system fermentation temperature was controlled to 37°C. When the residence time was controlled at 80h, the system was stable after about 40 days, the hydrogen production was stable at about 800mL / d, and the hydrogen production per gram weight reached about 80mL / g·VS. When the residence time was controlled at 240h, the system was stable after about 20 days, the hydrogen volume was stable at about 1000mL / d, and the hydrogen production per gram weight reached about 95mL / g·VS.

[0019] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for producing hydrogen by fermentation of rumen microorganisms, characterized in that: include: Fresh rumen fluid is inoculated into a fermentation tank filled with a buffer solution. After a period of time, biomass waste is added to start the fermentation reaction. When the H2 content in the gas-producing component reaches the set value, the fermentation temperature, HRT, SRT, and pH range are controlled, and biomass waste is added to maintain the headspace pressure, and continuous material and water in and out fermentation and hydrogen production begins.

2. A method for producing hydrogen by fermentation of rumen microorganisms according to claim 1, characterized in that: After 24-36 hours, 10-30 g / L of biomass waste is added to start the fermentation reaction.

3. The method for producing hydrogen by fermentation of rumen microorganisms according to claim 1, characterized in that: When the H2 content in the gas-producing components reaches 20%, the fermentation temperature is controlled at 37-40°C, HRT 50-90h, SRT 6-10d, and pH 5.5-6.

0.

4. The method for producing hydrogen by fermentation of rumen microorganisms according to claim 1, characterized in that: Biomass waste was added at 1-3 g / L·d, and the headspace pressure was maintained at 95±5 kPa.

5. The method for producing hydrogen by fermentation of rumen microorganisms according to claim 1, characterized in that: After the buffer solution is dissolved, it is exposed to CO2 gas for 3-5 minutes, and the pH of the buffer solution is adjusted to 5-6 with hydrochloric acid.