Method for promoting two-phase anaerobic digestion to produce hydrogen and methane and application

Abstract

The invention discloses a method for promoting two-phase anaerobic digestion to produce hydrogen and methane and application, and relates to the field of organic solid waste energy regeneration. According to the method, a two-phase anaerobic digestion system is adopted, and acetivibrio thermocellulus DSM 1313 and anaerobic digestion sludge are inoculated into a hydrolytic acidification phase, so that the hydrolysis of organic solid waste and the generation of hydrogen are promoted; a part of the generated leachate is refluxed into the hydrolytic acidification phase, and the rest leachate is transferred to the methanogenesis phase as a substrate for anaerobic digestion methanogenesis. According to the method disclosed by the invention, the hydrolysis and hydrogen production metabolism of the organic solid waste are regulated and controlled by utilizing the vibrio thermocellum, the inhibition effect of a high-load substrate is relieved, the hydrolysis hydrogen production efficiency is improved, meanwhile, more metabolic precursors are provided for a methanogenesis phase, and the anaerobic digestion methanogenesis efficiency is promoted. The process is simple, the hydrolytic acidification efficiency of the kitchen waste can be remarkably improved, and the hydrogen and methane yield of a two-phase anaerobic digestion system is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of organic solid waste energy conversion, and specifically to a method and application of promoting two-phase anaerobic digestion to produce hydrogen and methane. Background Art

[0002] Food waste includes grains, vegetables, meat and other ingredients. It is a perishable substance with high organic matter content, high water content and high oil content. Therefore, improper management and disposal of food waste will have multiple negative impacts on the ecological environment and even endanger human health. Usually, food waste is disposed of by landfill and incineration. The landfill cost is about 300 yuan / ton, which not only occupies a large area, but also produces high-concentration chemical oxygen demand leachate, leading to groundwater pollution and bringing secondary impacts to the environment. The incineration cost is about 450 yuan / ton, which will produce carcinogens such as dioxins. According to the World Bank's forecast, by 2050, global urban food waste will reach 3.4 billion tons / year. If the resource utilization rate is less than 30%, it will trigger a systemic ecological crisis.

[0003] Anaerobic digestion is a green and promising technology and one of the most effective ways to treat food waste. However, the traditional single-phase anaerobic digestion system has low methane production and energy recovery efficiency due to low substrate degradation efficiency and accumulation of volatile fatty acids. The two-phase anaerobic digestion system separates the hydrolysis and acidification phase from the methanogenesis phase, so that the microorganisms involved in hydrolysis / acidification and methanogens are distributed in two independent reaction systems. The two reaction systems can be independently controlled, which can effectively shorten the hydraulic retention time and enhance the stability of the system. However, the hydrolysis of food waste is still the main rate-limiting step.

[0004] In order to solve the inhibitory effect of high-load food waste hydrolysis and acidification, bioaugmentation is an effective measure to overcome this problem. At present, there is no report on the regulation of food waste directional hydrolysis and hydrogen production by Acetovibrio thermocellum, nor is there any research on its application in two-phase anaerobic digestion system. Summary of the invention

[0005] The object of the present invention is to provide a method and application for promoting hydrogen and methane production by two-phase anaerobic digestion, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions: A method for promoting two-phase anaerobic digestion to produce hydrogen and methane, characterized by comprising the following steps: Step 1: placing the organic solid waste in a hydrolysis and acid-producing phase, adding water and inoculating anaerobic digestion sludge and thermoacetovibrio to produce leachate and hydrogen; Step 2: The leachate produced in step 1 is split, and part of the leachate is refluxed to the hydrolysis acid-producing phase after adding water and adjusting the pH; the remaining leachate is transferred to the methanogenic phase as a substrate after adjusting the pH to produce methane.

[0007] Preferably, the hydrolysis acid-generating phase is a percolation bed reactor; Preferably, the methanogenic phase is an upflow anaerobic sludge blanket reactor.

[0008] Preferably, in step 1, anaerobic digestion sludge and thermoacetovibrio are used as total inoculum, and inoculated according to total inoculum: organic solid waste = (0.5-1.5) mL: 5 g; Preferably, the organic solid waste is at least one of agricultural and forestry waste, straw, livestock manure, municipal sludge, and food waste; more preferably, it is food waste; Preferably, water is added in step 1 until the total solid content in the hydrolysis acid-generating phase is 12.5-17.5% (w / w); Preferably, the proportion of Acetovibrio thermocellum in the total inoculum is 20-80% (v / v), and the inoculation concentration is 4-6 × 10 8 CFU / mL; Preferably, in step 2, the leachate is refluxed into the hydrolysis acid-generating phase at a volume ratio of 25-75%, the volume ratio of the added water to the refluxed part of the leachate is 1:1, and the pH is adjusted to 6.0±0.2; Preferably, the remaining leachate is adjusted to a pH of 7.2 ± 0.2; Preferably, the reaction temperature of the hydrolysis acid-generating phase is 52-58°C; Preferably, the reaction temperature of the methanogenic phase is 35-39°C; The two-phase anaerobic digestion system used in the above method comprises a hydrolysis acidogenic phase and a methanogenic phase; The two-phase anaerobic digestion system is suitable for batch, semi-continuous and continuous operation modes.

[0009] The above method for promoting two-phase anaerobic digestion to produce hydrogen and methane is applied in the resource utilization of organic solid waste.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention selects Acetovibrio thermocellum, which is easy to culture and can not only improve the hydrolysis efficiency of kitchen waste, but also promote hydrogen production metabolism, thereby realizing the resource utilization of kitchen waste.

[0011] 2. The present invention adopts a partial reflux process of the leachate to further alleviate the substrate inhibition of the kitchen waste, promote the hydrolysis and acid production of the substrate, provide more reaction precursors for the methanogenic phase, and improve the methanogenic efficiency and potential.

[0012] 3. The process steps of the present invention are simple, easy to operate, low in cost, high in gas yield, and simultaneous recovery of hydrogen and methane is achieved. The method of the present invention can achieve a hydrogen yield of up to 26.29-39.07 liters / kg of volatile solids and a methane yield of up to 58.75-127.63 liters / kg of volatile solids from kitchen waste in application. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the two-phase anaerobic digestion system of the present invention; Figure 2 The daily percolate volume diagram of the hydrolysis acid-generating phase of Examples 1-5 and the comparative example of the present invention; Figure 3 The daily chemical oxygen demand concentration diagram of the hydrolysis acid production phase of Examples 1-5 and the comparative example of the present invention; Figure 4 The daily hydrogen production graph of the hydrolysis acid generation phase of Examples 1-5 and the comparative example of the present invention; Figure 5 It is a graph of daily methane production in the methanogenic phase of Examples 1-5 and the comparative example of the present invention. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] In the experiment, Acetivibrio thermocellus DSM 1313 was inoculated at a concentration of 5 × 10 8 CFU / mL.

[0016] Example 1: This example provides a method for promoting hydrogen and methane production by two-phase anaerobic digestion. Figure 1 The two-phase anaerobic digestion system, the specific method is as follows: 2.0 kg of food waste was placed in the hydrolysis and acid production phase of the two-phase anaerobic digestion system, and water was added until the total solid content of the percolation bed reactor was 15%. The total inoculum: food waste = 1 mL: 5 g was inoculated into the hydrolysis and acid production phase, and mixed evenly to produce leachate and hydrogen; wherein, the proportion of Acetovibrio thermocellum in the total inoculum was 50% (v / v), and the proportion of anaerobic digestion sludge was 50% (v / v); The leachate produced in the hydrolysis and acidogenesis phase was collected daily, 50% of the leachate was mixed with the same volume of water, the pH was adjusted to 6.0±0.2, and then refluxed to the hydrolysis and acidogenesis phase of the leachate bed reactor; the remaining 50% of the leachate was adjusted to pH 7.2±0.2, and then transferred to the methanogenesis phase of the upflow anaerobic sludge blanket reactor as a substrate to produce methane; wherein, the reaction temperature of the hydrolysis and acidogenesis phase was 55°C, and the reaction temperature of the methanogenesis phase was 37°C.

[0017] Example 2: Referring to Example 1, the proportion of Acetovibrio thermocellum was adjusted to 25% (v / v), and the specific method is as follows: 2.0 kg of food waste was placed in the hydrolysis and acid production phase of the two-phase anaerobic digestion system, and water was added until the total solid content of the percolation bed reactor was 15%. The total inoculum: food waste = 1 mL: 5 g was inoculated into the hydrolysis and acid production phase, and mixed evenly to produce leachate and hydrogen; among which, the proportion of Thermocellar Acetovibrio in the total inoculum was 25% (v / v), and the proportion of anaerobic digestion sludge was 75% (v / v); The leachate produced in the hydrolysis and acidogenesis phase was collected daily, 50% of the leachate was mixed with the same volume of water, the pH was adjusted to 6.0±0.2, and then refluxed to the hydrolysis and acidogenesis phase of the leachate bed reactor; the remaining 50% of the leachate was adjusted to pH 7.2±0.2, and then transferred to the methanogenesis phase of the upflow anaerobic sludge blanket reactor as a substrate to produce methane; wherein, the reaction temperature of the hydrolysis and acidogenesis phase was 55°C, and the reaction temperature of the methanogenesis phase was 37°C.

[0018] Example 3: Referring to Example 1, the proportion of Acetovibrio thermocellum was adjusted to 75% (v / v), and the specific method is as follows: 2.0 kg of food waste was placed in the hydrolysis and acid production phase of the two-phase anaerobic digestion system, and water was added until the total solid content of the percolation bed reactor was 15%. The total inoculum: food waste = 1 mL: 5 g was inoculated into the hydrolysis and acid production phase, and mixed evenly to produce leachate and hydrogen; among which, the proportion of Acetovibrio thermocellum in the total inoculum was 75% (v / v), and the proportion of anaerobic digestion sludge was 25% (v / v); The leachate produced in the hydrolysis and acidogenesis phase was collected daily, 50% of the leachate was mixed with the same volume of water, the pH was adjusted to 6.0±0.2, and then refluxed to the hydrolysis and acidogenesis phase of the leachate bed reactor; the remaining 50% of the leachate was adjusted to pH 7.2±0.2, and then transferred to the methanogenesis phase of the upflow anaerobic sludge blanket reactor as a substrate to produce methane; wherein, the reaction temperature of the hydrolysis and acidogenesis phase was 55°C, and the reaction temperature of the methanogenesis phase was 37°C.

[0019] Example 4: Referring to Example 1, the leachate was adjusted to 25% reflux, and the specific method is as follows: 2.0 kg of food waste was placed in the hydrolysis and acid production phase of the two-phase anaerobic digestion system, and water was added until the total solid content of the percolation bed reactor was 15%. The total inoculum: food waste = 0.5 mL: 5 g was inoculated into the hydrolysis and acid production phase, and mixed evenly to produce leachate and hydrogen; wherein, the proportion of Thermocellar Acetovibrio in the total inoculum was 50% (v / v), and the proportion of anaerobic digestion sludge was 50% (v / v); The leachate produced in the hydrolysis and acidogenesis phase was collected daily, 25% of the leachate was mixed with the same volume of water, the pH was adjusted to 6.0±0.2, and then refluxed to the hydrolysis and acidogenesis phase of the leachate bed reactor; the remaining 75% of the leachate was adjusted to pH 7.2±0.2, and then transferred to the methanogenesis phase of the upflow anaerobic sludge blanket reactor as a substrate to produce methane; wherein, the reaction temperature of the hydrolysis and acidogenesis phase was 55°C, and the reaction temperature of the methanogenesis phase was 37°C.

[0020] Example 5: Referring to Example 1, the leachate was adjusted to reflux at 75%, and the specific method is as follows: 2.0 kg of food waste was placed in the hydrolysis and acid production phase of the two-phase anaerobic digestion system, and water was added until the total solid content of the percolation bed reactor was 15%. The total inoculum: food waste = 1.5 mL: 5 g was inoculated into the hydrolysis and acid production phase, and mixed evenly to produce leachate and hydrogen; wherein, the proportion of Acetovibrio thermocellum in the total inoculum was 50% (v / v), and the proportion of anaerobic digestion sludge was 50% (v / v); The leachate produced in the hydrolysis and acidogenesis phase was collected daily, 75% of the leachate was mixed with the same volume of water, the pH was adjusted to 6.0±0.2, and then refluxed to the hydrolysis and acidogenesis phase of the leachate bed reactor; the remaining 25% of the leachate was adjusted to pH 7.2±0.2, and then transferred to the methanogenesis phase of the upflow anaerobic sludge blanket reactor as a substrate to produce methane; wherein, the reaction temperature of the hydrolysis and acidogenesis phase was 55°C, and the reaction temperature of the methanogenesis phase was 37°C.

[0021] Comparative Example 1: As a control experiment of Example 1, the two-phase anaerobic digestion system of Example 1 was used, except that the thermocellum acetovibrio was not inoculated. The specific method is as follows: 2.0 kg of food waste was placed in the hydrolysis and acid production phase of the two-phase anaerobic digestion system, water was added until the total solid content of the percolation bed reactor was 15%, and the hydrolysis and acid production phase was inoculated according to the anaerobic digestion sludge: food waste = 1 mL: 5 g, and mixed evenly to produce leachate and hydrogen; The leachate produced in the hydrolysis and acidogenesis phase was collected daily, 50% of the leachate was mixed with the same volume of water, the pH was adjusted to 6.0±0.2, and then refluxed to the hydrolysis and acidogenesis phase of the leachate bed reactor; the remaining 50% of the leachate was adjusted to pH 7.2±0.2, and then transferred to the methanogenesis phase of the upflow anaerobic sludge blanket reactor as a substrate to produce methane; wherein, the reaction temperature of the hydrolysis and acidogenesis phase was 55°C, and the reaction temperature of the methanogenesis phase was 37°C.

[0022] Detection test For the two-phase anaerobic digestion system of kitchen waste in Examples 1 to 5 and the comparative example, the daily leachate volume, chemical oxygen demand concentration, hydrogen production produced by the hydrolysis acid production phase, and methane production produced by the methane production phase were measured, the removal rate of volatile solids was analyzed, and the cumulative chemical oxygen demand, hydrogen yield, and methane yield were calculated and tabulated and plotted, as shown in Table 1. Figure 2 , 3 , 4, 5.

[0023] Table 1 Hydrogen and methane production performance of two-phase anaerobic digestion system of food waste Regarding the daily filtrate volume determination of Examples 1 to 5 and Comparative Example 1, by Figure 2 It can be seen that the daily leachate volume produced by the hydrolysis acid-producing phase in Examples 1 to 5 is higher than that in Comparative Example 1 from the 9th day onwards, indicating that the addition of Acetovibrio thermocellum to the inoculum significantly improves the hydrolysis efficiency of food waste, which can relieve the substrate inhibition of high-load food waste.

[0024] Regarding the daily chemical oxygen demand concentration determination of Examples 1 to 5 and Comparative Example 1, Figure 3 It can be seen that before 9 days of reaction, the chemical oxygen demand concentration of the daily leachate produced by the hydrolysis acid production phase in Examples 1 to 5 was higher than that in Comparative Example 1, indicating that the addition of Thermoacetovibrio cellulosa to the inoculum promoted the acid production process. In addition, the daily chemical oxygen demand concentration of Examples 1 to 5 and Comparative Example 1 gradually decreased with the extension of the reaction time, indicating that the daily leachate reflux rinsed the substrate, diluted the metabolites produced during the reaction process, and alleviated the acid inhibition effect caused by acid accumulation.

[0025] The daily hydrogen production of Examples 1 to 5 and Comparative Example 1 was determined by Figure 4 It can be seen that the daily hydrogen production increased after adding Thermoacetovibrio to the inoculum, especially before 7 days of reaction, the hydrogen production rate in the hydrolysis acidification phase was significantly improved, and the peak daily hydrogen production of Example 1 was 3.23 times that of Example 1, indicating that inoculating Thermoacetovibrio in the hydrolysis acidification phase can promote hydrogen production metabolism and improve the efficiency of converting food waste into hydrogen.

[0026] Regarding the daily methane production determination of Examples 1 to 5 and Comparative Example 1, Figure 5 It can be seen that before the 8th day, the daily methane production of the methanogenic phase in Examples 1 to 5 was higher than that of Comparative Example 1, and the maximum daily methane production of Example 5 was 7.53 liters, which was 1.97 times the 3.82 liters of Comparative Example 1. Since the thermoacetovibrio cellulosa promoted the hydrolysis and acidification process of the kitchen waste, there were more volatile fatty acids in the leachate, which provided sufficient precursor substances for the methanogenic metabolism, thereby promoting the methanogenic efficiency of the methanogenic phase.

[0027] By measuring the daily leachate volume, chemical oxygen demand concentration, hydrogen production and methane production, and analyzing the volatile solid removal rate, the cumulative chemical oxygen demand, hydrogen and methane yields can be calculated, and the results are shown in Table 1. The cumulative hydrogen yields of Examples 1 to 5 are 39.07 L / kg volatile solids, 28.83 L / kg volatile solids, 29.08 L / kg volatile solids, 26.29 L / kg volatile solids, and 25.58 L / kg volatile solids, respectively, which are all higher than 21.63 L / kg volatile solids of Comparative Example 1; in addition, the cumulative methane yields of Examples 1 to 5 reach 100.04 L / kg volatile solids, respectively. The content of volatile solids in the comparative example 1 was 70.07 L / kg, volatile solids in the comparative example 1 was 80.75 L / kg, 58.75 L / kg, and 127.63 L / kg, which was also greater than 58.71 L / kg volatile solids in comparative example 1. This once again verified that the two-phase anaerobic digestion of food waste was regulated by inoculating Vibrio thermocellum, which promoted the hydrogen production and methane production metabolic pathways, demonstrating the great advantages of bioaugmentation.

[0028] In summary, it can be seen that it is feasible to use thermocellar acetovibrio to bioenhance the two-phase anaerobic digestion system of food waste, which not only alleviates the substrate inhibition of high-load food waste, promotes the hydrolysis and acidification of the substrate, but also enhances the metabolic conversion efficiency of hydrogen production and methane production. The two-phase anaerobic digestion system of the present invention is simple to operate, has low energy consumption, and has excellent effects.

[0029] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for promoting hydrogen and methane production by two-phase anaerobic digestion, characterized in that: The following steps are involved: Step 1: adding organic solid waste to the hydrolysis acid-producing phase, supplementing water and inoculating anaerobic digestion sludge and thermoacetovibrio to produce leachate and hydrogen; Step 2: The leachate produced in step 1 is split, and part of the leachate is refluxed to the hydrolysis acid-producing phase after adding water and adjusting the pH; the remaining leachate is transferred to the methanogenic phase as a substrate after adjusting the pH to produce methane.

2. A method for promoting hydrogen and methane production by two-phase anaerobic digestion according to claim 1, characterized in that: The hydrolysis acid-producing phase is a percolation bed reactor; the methanogenic phase is an upflow anaerobic sludge blanket reactor.

3. The method for promoting hydrogen and methane production by two-phase anaerobic digestion according to claim 1, characterized in that: In step 1, anaerobic digestion sludge and Thermoacetovibrio cellulosae were used as the total inoculum, and the inoculation was carried out according to the total inoculum: organic solid waste = (0.5-1.5) mL: 5 g; wherein, Thermoacetovibrio cellulosae accounted for 20-80% (v / v) of the total inoculum, and the inoculation concentration was 4-6 × 10 8 CFU / mL.

4. The method for promoting hydrogen and methane production by two-phase anaerobic digestion according to claim 1, characterized in that: The organic solid waste is at least one of agricultural and forestry waste, straw, livestock manure, municipal sludge, and food waste; step 1 adds water until the total solid content in the hydrolysis acid-producing phase is 12.5-17.5% (w / w).

5. The method for promoting hydrogen and methane production by two-phase anaerobic digestion according to claim 1, characterized in that: The reaction temperature of the hydrolysis acid-producing phase is 52-58°C, and the reaction temperature of the methanogenic phase is 35-39°C.

6. The method for promoting hydrogen and methane production by two-phase anaerobic digestion according to claim 1, characterized in that: In step 2, the leachate is refluxed to the hydrolysis acid-generating phase at a volume ratio of 25-75%, the volume ratio of the added water to the refluxed part of the leachate is 1:1, and the pH is adjusted to 6.0±0.

2.

7. The method for promoting hydrogen and methane production by two-phase anaerobic digestion according to claim 1, characterized in that: The remaining leachate was adjusted to pH 7.2 ± 0.

2.

8. A two-phase anaerobic digestion system used by the method according to any one of claims 1 to 7, characterized in that: The two-phase anaerobic digestion system comprises a hydrolysis acidogenic phase and a methanogenic phase.

9. Use of the method according to any one of claims 1 to 7 in the resource recovery of organic solid waste.

Images