Biochar, preparation method thereof and application of biochar in co-production of hydrogen and bio-fertilizer through anaerobic fermentation of bone meal

Abstract

The invention relates to biochar, a preparation method thereof and application of the biochar in coproduction of hydrogen and bio-fertilizer through anaerobic fermentation of bone meal, and the application comprises the following steps: uniformly mixing the bone meal, the biochar, an anaerobic fermentation inoculum and distilled water to construct anaerobic dark fermentation liquor, adjusting the initial pH value of the anaerobic dark fermentation liquor, fermenting under anaerobic and constant-temperature conditions to obtain the biochar. Gas generated in the fermentation process is collected, biogas with hydrogen as the main component is obtained, after fermentation is finished, solid-liquid separation is conducted on fermentation residues, and supernate is the liquid biological fertilizer. According to the method, a proper amount of biochar is added into an anaerobic dark fermentation system taking bone meal as a main fermentation substrate, so that the problems of product inhibition and acidification in the bone meal fermentation process can be effectively relieved, the yield and the yield of hydrogen are remarkably improved, degradation and mineralization of the substrate are promoted by adding the biochar, and the biochar has a good application prospect. More nitrogen and phosphorus elements are released and dissolved in the fermentation liquor, so that the value of the fermentation liquor as a liquid biological fertilizer is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of organic waste treatment and bioenergy technology, specifically relating to a biochar and its preparation method, and its application in the anaerobic fermentation of bone meal to co-produce hydrogen and bio-fertilizer. Background Technology

[0002] Bone meal is a powdered product of processed animal bones. It is one of the main solid wastes generated by slaughterhouses and meat processing plants. It is rich in organic matter such as collagen and fat, as well as inorganic salts such as calcium phosphate. If it is not disposed of properly, it will cause environmental pollution. The resource utilization of bone meal is an inevitable requirement for realizing a circular economy and sustainable development. Dark fermentation hydrogen production is a biotechnology that uses anaerobic microorganisms to convert organic substrates into hydrogen. It has the advantages of low energy consumption and environmental friendliness. Bone meal has the potential to be used as a substrate for dark fermentation hydrogen production due to its high organic matter content. However, directly using bone meal for fermentation hydrogen production faces many challenges: (1) The accumulation of volatile fatty acids (VFAs) during fermentation is easy to occur, which leads to acidification of the system and further inhibits the hydrogen production process; (2) The above factors together lead to slow hydrogen production rate, long cycle and low total output, which limits its industrial application.

[0003] Biochar is a solid product of biomass pyrolysis and carbonization under anaerobic or anoxic conditions. It has a well-developed porous structure, a large specific surface area, good electrical conductivity, and abundant oxygen-containing functional groups on its surface. In recent years, biochar has received widespread attention as a functional additive in the field of anaerobic fermentation. Studies have shown that biochar can serve as a carrier for microbial attachment, enriching functional bacterial communities; its alkalinity can buffer the pH of the system and alleviate acidification; and its electrical conductivity may promote intermediate electron transfer and improve metabolic efficiency.

[0004] However, there are currently no reports on the application of biochar in enhancing hydrogen production through anaerobic fermentation of bone meal, and on the systematic evaluation of its simultaneous impact on hydrogen production and nutrient enrichment. Therefore, there is an urgent need to develop an efficient technology that can overcome the problem of inhibiting hydrogen production during bone meal fermentation and achieve co-production of energy and fertilizer. Based on this, the present invention provides a biochar, its preparation method, and its application in the co-production of hydrogen and bio-fertilizer through anaerobic fermentation of bone meal. Summary of the Invention

[0005] The purpose of this invention is to provide a biochar and its preparation method, as well as its application in the anaerobic fermentation of bone meal to produce hydrogen and bio-fertilizer, in order to solve the above-mentioned problems.

[0006] The present invention achieves the above objectives through the following technical solutions: This invention provides a method for preparing biochar, comprising the following preparation steps: (1) Select dry, mold-free biomass materials, crush, dry, and sieve the biomass materials to obtain biomass powder; the biomass is at least one of sawdust, chestnut shells, and rice husk ash; (2) The pretreated biomass powder was subjected to thermal pyrolysis in a nitrogen atmosphere and then naturally cooled to room temperature to obtain biochar.

[0007] As a further optimization of the present invention, in step (1), the biomass is pulverized and dried at a temperature of 60-80℃ for 12-24 hours to make the moisture content <10%, and then the biomass powder is obtained after passing through a 20-mesh sieve.

[0008] As a further optimization of the present invention, in step (2), the thermal decomposition treatment specifically involves heating to 500-700°C at a heating rate of 5-10°C / min under a nitrogen atmosphere and holding for 1-3 hours.

[0009] The present invention also provides biochar prepared by the method described above.

[0010] This invention also provides an application of the biochar described above in the anaerobic fermentation of bone meal to co-produce hydrogen and bio-fertilizer. Bone meal is used as the main fermentation substrate, and biochar is used as a promoter. The biochar is mixed evenly with anaerobic fermentation inoculum and distilled water to construct an anaerobic dark fermentation broth. The initial pH is adjusted, and fermentation is carried out under anaerobic and constant temperature conditions. The gas produced during fermentation is collected to obtain biogas with hydrogen as the main component. After fermentation, the fermentation residue is separated into solid and liquid components, and the resulting supernatant is a liquid bio-fertilizer rich in phosphorus and nitrogen.

[0011] As a further optimization of the present invention, the amount of biochar added is 5-20 g / L of anaerobic dark fermentation broth.

[0012] As a further optimization of the present invention, the amount of bone meal added, calculated on a volatile solids basis, is 4-12 g-VS / L of anaerobic dark fermentation broth.

[0013] As a further optimization of the present invention, the initial pH is 6.5-7.5, and the constant temperature is 35-40℃.

[0014] The beneficial effects of this invention are as follows: 1) This invention, by adding an appropriate amount of biochar to an anaerobic dark fermentation system with bone meal as the main fermentation substrate, can effectively alleviate the product inhibition and acidification problems during bone meal fermentation, providing a superior microenvironment for hydrogen-producing microorganisms, thereby significantly increasing the yield and efficiency of hydrogen. Furthermore, the addition of biochar promotes the degradation and mineralization of the substrate, allowing more nitrogen and phosphorus elements to be released and dissolved in the fermentation broth, significantly increasing the concentration of ammonium ions and phosphate ions in the fermentation broth, and enhancing its value as a liquid bio-fertilizer. 2) Through experimental verification, this invention found that when the compound formula of sawdust and chestnut shells is used as biomass material, the biochar prepared under the 500℃ pyrolysis treatment condition is added to the anaerobic dark fermentation system at an addition amount of 10g / L, which can significantly increase the hydrogen production and the concentration of nutrients in the bio-fertilizer. 3) This invention only requires adding a biochar addition step to the existing fermentation process. It is simple to operate and easy to implement, and achieves synergistic effects among the treatment of organic solid waste, production of clean energy and preparation of high-efficiency liquid bio-fertilizer, resulting in significant economic and environmental benefits. Attached Figure Description

[0015] Figure 1 This is a graph showing the changes in biological hydrogen accumulation under different substrate loading and biochar (biochar prepared in Experiment 6 of this invention) addition conditions.

[0016] Figure 2 This is a graph showing the changes in ammonium ion accumulation under different substrate loading and biochar (biochar prepared in Experiment 6 of this invention) addition conditions.

[0017] Figure 3 This is a graph showing the changes in phosphate ion accumulation under different substrate loading and biochar (biochar prepared in Experiment 6 of this invention) addition conditions. Detailed Implementation

[0018] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0019] I. Materials 1. Bone meal: Purchased from Shandong Xianglanding Environmental Protection Technology Co., Ltd., the VS (volatile solids) content of the bone meal is 93%; 2. Anaerobic fermentation inoculum: Hydrogen-producing activated sludge obtained by anaerobic digestion sludge from a wastewater treatment plant through hydrogen production acclimation and cultivation. 3. pH adjuster: 1 mol / L hydrochloric acid and sodium hydroxide solution.

[0020] Unless otherwise specified, all methods used in this application are conventional methods known to those skilled in the art, and all reagents and materials used are commercially available products unless otherwise specified.

[0021] II. Methods 2.1 Investigating the effects of biochar made from different biomass on hydrogen production and nutrient concentrations in liquid bio-fertilizers. 2.1.1 This invention provides a method for preparing biochar, specifically including the following steps: 1) Select dry, mold-free biomass materials. Crush the biomass materials (Experiment 1: sawdust; Experiment 2: chestnut shells; Experiment 3: rice husk ash; Experiment 4: sawdust and chestnut shells in a 1:1 mass ratio; Experiment 5: sawdust and rice husk ash in a 1:1 mass ratio) and dry them in an oven at 60-80℃ for 12-24 hours (preferably 68±2℃, 18 hours) until the moisture content is <10% (preferably 7.2%). Pass the powder through a 20-mesh sieve to remove large particles and impurities to obtain biomass powder. 2) Purge the tube furnace with nitrogen (50 mL / min flow rate for 10 min), then place the dried biomass powder into the tube furnace, using nitrogen as a protective gas at a flow rate of 5-15 mL / min (preferably 8 mL / min), heat to 300℃ at a heating rate of 5-10℃ / min (preferably 6℃ / min), hold at this temperature for 1-3 h (2 h) for thermal pyrolysis, and then allow to cool naturally to room temperature to obtain biochar.

[0022] 2.1.2 This invention provides an application of biochar in the anaerobic fermentation of bone meal to co-produce hydrogen and bio-fertilizer, as detailed below: 1) Bone meal was used as the main fermentation substrate (the amount of bone meal added, based on volatile solids, was 12 g-VS / L of anaerobic dark fermentation broth), and biochar (the amount of biochar added was 5 g / L of anaerobic dark fermentation broth) was used as a promoter. The mixture was combined with 10% v / v of anaerobic fermentation inoculum and distilled water to construct the anaerobic dark fermentation broth. 2) The anaerobic dark fermentation broth is fermented under anaerobic conditions (the reactor is sealed, high-purity nitrogen is introduced into the top space, and the vacuum and gas are repeatedly pumped out 3 times to completely remove oxygen from the reactor and ensure a strict anaerobic environment) and a constant temperature of 35-40℃ (preferably 37±1℃). 3) Collect the gas produced during fermentation using a gas collection device to obtain biogas with hydrogen as the main component, and measure and analyze the cumulative hydrogen production of each group. 4) After fermentation is completed (fermentation ends when gas production stops, usually a cycle of 20-30 days), the fermentation residue is separated into solid and liquid components. The resulting supernatant is a liquid bio-fertilizer rich in phosphorus and nitrogen, and the concentration of nutrients in the liquid bio-fertilizer is measured.

[0023] The experimental design schemes for Experiments 1-5, the cumulative hydrogen production, and the statistical data on the concentration of nutrients in the liquid bio-fertilizer are shown in Table 1. Table 1. Experimental design schemes (biomass materials) and data statistics for Experiments 1-5 ; Note: When there are two types of biomass, the mass ratio of the two types of biomass is 1:1.

[0024] Experimental Conclusion: Analysis of the data in Table 1 shows that when sawdust and chestnut shells are used as biomass, the cumulative hydrogen production and nutrient elements in the liquid bio-fertilizer remain at high levels. This indicates that biochar made from sawdust and chestnut shells has excellent performance. Through their synergistic effect, it can significantly improve the product inhibition and acidification problems in the anaerobic fermentation process of bone meal, providing a superior microenvironment for hydrogen-producing microorganisms, thereby significantly increasing hydrogen production. At the same time, it can also increase the concentration of ammonium ions and phosphate ions in the liquid bio-fertilizer, enhancing the application value of the liquid bio-fertilizer.

[0025] 2.2. Investigating the effects of biochar produced at different pyrolysis temperatures on hydrogen production and nutrient concentrations in liquid bio-fertilizer. The only difference between this experiment and the experimental group 4 in step 2.1 above is the different pyrolysis temperature of the biochar. The experimental design schemes for the following experimental groups 6-7 are shown in Table 2: Table 2. Experimental design schemes (pyrolysis temperature) and data statistics for Experiments 4 and 6-7. ; Experimental conclusion: By comparing the effects of biochar produced at different pyrolysis temperatures on hydrogen production and nutrient concentrations in liquid bio-fertilizer, the results show that 500℃ is the optimal pyrolysis temperature.

[0026] 2.3. Investigating the effects of different biochar addition amounts on hydrogen production and nutrient concentrations in liquid bio-fertilizer. The only difference between this experiment and the experimental group 6 in step 2.2 above is the amount of biochar added, resulting in the experimental designs for groups 8-10 as shown in Table 3: Table 3. Experimental design schemes (biochar addition amount) and data statistics for groups 6 and 8-10. ; Experimental conclusion: By comparing the effects of different biochar addition amounts on hydrogen production and nutrient concentrations in liquid bio-fertilizer, the results showed that adding 10 g / L of biochar to the anaerobic dark fermentation broth with bone meal as the main fermentation substrate was the optimal addition amount.

[0027] 2.4. Investigating the effects of biochar on hydrogen production and nutrient concentrations in liquid bio-fertilizer under high and low substrate loading conditions. Under high substrate loading: Bone meal dosage, calculated as volatile solids, is 12 g-VS / L of anaerobic dark fermentation broth; Under high substrate loading: Bone meal dosage, calculated as volatile solids, is 12 g-VS / L of anaerobic dark fermentation broth; The only difference between this experiment and group 8 in step 2.3 above is the substrate (bone meal) concentration. This yields the experimental design for group 11 below. Furthermore, based on groups 8 and 11, control group experiments without biochar were designed, resulting in the experimental designs for control groups 1-2 below, as shown in Table 4. Table 4 Experimental designs (substrate concentration, biochar addition amount) for Experiments 8 and 11 and Control Groups 1-2 and data statistics table ; Experimental conclusions: Based on the analysis in Table 4, it can be seen that under low substrate loading, biochar has a significant promoting effect on hydrogen production and nutrient enrichment. Under high substrate loading, adding biochar as a promoter can effectively overcome potential fermentation inhibition and achieve a significant increase in hydrogen production and the quality of liquid bio-fertilizer.

[0028] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing biochar, characterized in that: The preparation steps include the following: (1) Select dry, mold-free biomass materials, crush, dry, and sieve the biomass materials to obtain biomass powder; the biomass is at least one of sawdust, chestnut shells, and rice husk ash; (2) Biochar was prepared by thermally decomposing biomass powder in a nitrogen atmosphere and then naturally cooling it to room temperature.

2. The method for preparing biochar according to claim 1, characterized in that: In step (1), specifically, the biomass is pulverized and dried at a temperature of 60-80℃ for 12-24 hours to make the moisture content <10%, and then passed through a 20-mesh sieve to obtain biomass powder.

3. The method for preparing biochar according to claim 1, characterized in that: In step (2), the thermal decomposition treatment specifically involves heating the temperature to 500-700℃ at a heating rate of 5-10℃ / min under a nitrogen atmosphere and holding it at that temperature for 1-3 hours.

4. A type of biochar, characterized in that: It is prepared by any one of the preparation methods described in claims 1-3.

5. An application of biochar as described in claim 4 in the anaerobic fermentation of bone meal to co-produce hydrogen and bio-fertilizer, characterized in that, Bone meal was used as the main fermentation substrate, and biochar was used as a promoter. The mixture was homogenized with anaerobic fermentation inoculum and distilled water to construct an anaerobic dark fermentation broth. The initial pH was adjusted, and fermentation was carried out under anaerobic and constant temperature conditions. The gas produced during fermentation was collected to obtain biogas with hydrogen as the main component. After fermentation, the fermentation residue was separated into solid and liquid components. The supernatant obtained was a liquid bio-fertilizer rich in phosphorus and nitrogen.

6. The application according to claim 5, characterized in that: The biochar addition amount is 5-20 g / L of anaerobic dark fermentation broth.

7. The method according to claim 5, characterized in that: The amount of bone meal added, calculated as volatile solids, is 4-12 g-VS / L of anaerobic dark fermentation broth.

8. The method according to claim 5, characterized in that: The initial pH is 6.5-7.5, and the constant temperature is 35-40℃.

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