阅读说明：本技术 蔗渣-糖蜜-薯蓣渣混合原料发酵乙醇联产沼气的方法 (Method for co-producing biogas by fermenting ethanol with bagasse-molasses-yam slag mixed raw material ) 是由 谢君 樊美杉 于 2019-09-16 设计创作，主要内容包括：本发明公开了一种蔗渣-糖蜜-薯蓣渣混合原料发酵乙醇联产沼气的方法,包括如下步骤：S1.甘蔗渣预处理：将甘蔗渣粉碎,加入碱,水洗、干燥,得到预处理后甘蔗渣；S2.混合发酵：取预处理后甘蔗渣、菊叶薯蓣渣和糖蜜,先将菊叶薯蓣渣糖化,再将取预处理后甘蔗渣、糖化后的菊叶薯蓣渣和糖蜜混匀,加入酵母活化液和纤维素酶,进行同步糖化发酵产乙醇；所述预处理后甘蔗渣、菊叶薯蓣渣和糖蜜的质量以固液比为12％～44％称取；S3.厌氧发酵：同步糖化发酵后,移除乙醇,接入厌氧污泥,进行沼气发酵。本发明提供的以甘蔗渣、菊叶薯蓣渣和废糖蜜为原料联产乙醇和沼气的方法,提高了乙醇的产率、有效利用废液产生沼气,糖蜜和糖化后的菊叶薯蓣渣减小了废液的粘度,菊叶薯蓣渣代替了糖蜜和甘蔗渣生产不平衡问题,多原料混合使发酵后的废液更加适于厌氧发酵产沼气。不仅解决了乙醇发酵产率不高和废液难处理的问题,而且实现了废弃物资源利用化。(The invention discloses a method for co-producing biogas by fermenting ethanol with bagasse-molasses-yam slag mixed raw materials, which comprises the following steps: s1, bagasse pretreatment: crushing bagasse, adding alkali, washing with water, and drying to obtain pretreated bagasse; s2, mixed fermentation: taking the pretreated bagasse, the dioscorea composita residue and molasses, saccharifying the dioscorea composita residue, uniformly mixing the pretreated bagasse, the saccharified dioscorea composita residue and molasses, adding yeast activation solution and cellulase, and performing synchronous saccharification and fermentation to produce ethanol; weighing the pretreated bagasse, the dioscorea composita residue and the molasses according to the solid-liquid ratio of 12-44%; s3, anaerobic fermentation: after synchronous saccharification and fermentation, removing ethanol, inoculating anaerobic sludge, and performing biogas fermentation. The method for coproducing ethanol and methane by using bagasse, dioscorea composita residues and waste molasses as raw materials improves the yield of ethanol, effectively utilizes waste liquid to generate methane, reduces the viscosity of the waste liquid by using the molasses and the saccharified dioscorea composita residues, solves the problem of unbalanced production of the molasses and the bagasse by the dioscorea composita residues, and enables the waste liquid after fermentation to be more suitable for anaerobic fermentation to generate methane by mixing multiple raw materials. Not only solves the problems of low ethanol fermentation yield and difficult waste liquid treatment, but also realizes the utilization of waste resources.)

1. A method for co-producing biogas by fermenting ethanol with bagasse-molasses-yam slag mixed raw materials is characterized by comprising the following steps:

S1, bagasse pretreatment: crushing bagasse, adding an alkali solution, washing with water, and drying to obtain pretreated bagasse;

s2, mixed fermentation: taking the pretreated bagasse, the dioscorea composita residue and molasses, saccharifying the dioscorea composita residue, uniformly mixing the pretreated bagasse, the saccharified dioscorea composita residue and molasses, adding yeast activation solution and cellulase, and performing synchronous saccharification and fermentation to produce ethanol; weighing the pretreated bagasse, the dioscorea composita residue and the molasses according to the solid-liquid ratio of 12-44%;

S3, anaerobic fermentation: after synchronous saccharification and fermentation, removing ethanol, inoculating anaerobic sludge, and performing biogas fermentation.

2. The method as claimed in claim 1, wherein the pretreated bagasse, dioscorea composita residue and molasses are weighed so that the solid-to-liquid ratio is 12-36%.

3. The method for co-producing ethanol and biogas as claimed in claim 1, wherein step S2 is mixing and fermenting the pretreated bagasse, saccharified dioscorea composita residue and molasses in fed-batch manner.

4. the method according to claim 1 or 3, wherein the mass ratio of the pretreated bagasse, the dioscorea composita residue and the molasses is (1-5): (0.5-0.9): (0.1-0.5).

5. The method according to claim 3, wherein the fed-batch mode is that 1/3 of the pretreated bagasse and the dioscorea composita residue are added into the fermentation vessel at the beginning of the reaction; when the reaction is carried out for 12 hours, 1/3 of pretreated bagasse is added into a fermentation container; at the time of 24 hours of reaction, 1/3 of the pretreated bagasse, molasses and the mixture were added into a fermentation vessel.

6. the method as claimed in claim 5, wherein tween80 is added simultaneously at the initial feeding of the reaction in an amount of 10% by mass based on the total mass of the pretreated bagasse, the dioscorea composita residue and the molasses.

7. the method for co-producing ethanol and biogas as recited in claim 1, wherein the yeast activation solution is a saccharomyces cerevisiae activation solution.

8. the method for co-producing ethanol and biogas as claimed in claim 1, wherein the cellulase is 10-30 FPU/g pretreated bagasse.

9. The method for co-producing ethanol and biogas as claimed in claim 1, wherein the temperature of the simultaneous saccharification and fermentation is 30-38 ℃, the rotation speed is 100-200 rpm, and the time is 48-144 h.

10. The method for co-producing ethanol and biogas as recited in claim 1, wherein the anaerobic sludge is introduced in a ratio of (1-2) to 1 of inoculum to volatile solids in the substrate.

Technical Field

The invention relates to the field of biomass energy, in particular to a method for jointly producing ethanol and methane by using bagasse, molasses and yam slag as mixed raw materials.

Background

Bioethanol is a very considerable renewable energy source as an additive or a substitute for gasoline. The biogas is an ideal clean biofuel, and the biogas replaces the traditional fossil fuel to effectively avoid the problem of environmental pollution. Bioethanol and biogas can be used as automotive fuel, electricity or thermal energy, replacing fossil fuels. Currently, the method commonly used for producing bioethanol mainly uses lignocellulose biomass as raw material, and improves the concentration and yield of ethanol by mixing and fermenting with starch substances such as corn flour or wheat flour. In this process, food-type substances on which humans depend for survival are used.

Bagasse and molasses are by-products of the sugar industry. Bagasse is fibrous residue of sugarcane stalks obtained after sugarcane juice is extracted from sugarcane through crushing and squeezing, belongs to agricultural solid waste, and contains a large amount of cellulose, hemicellulose, lignin and the like. Molasses contains a large amount of fermentable sugars and is a good fermentation raw material.

When lignocellulose such as bagasse and the like is used alone for fermentation, mass transfer is limited along with the increase of the concentration of a substrate, so that the stirring is difficult, the ethanol yield is not high, the viscosity of the fermented waste liquid is high, the subsequent waste liquid fermentation cannot be utilized to produce methane, and the utilization of waste resources is realized. In addition, high load fermentation raises ethanol concentration while also presenting technical challenges such as stirring and mixing difficulties, mass transfer limitations, prolonged fermentation time, and the like.

Therefore, there is a need for a method for improving ethanol yield, efficiently utilizing waste liquid after fermentation to produce biogas, and efficiently producing ethanol under a high load condition of fermentation raw material.

Disclosure of Invention

The invention aims to overcome the defects that the ethanol yield is not high when bagasse is used for fermentation to produce ethanol and waste liquid is difficult to treat under a high-load state, and the ethanol and methane are difficult to produce efficiently in the prior art, and provides a method for jointly producing ethanol and methane by taking bagasse, molasses and yam slag as mixed raw materials.

in order to solve the technical problems, the invention adopts the technical scheme that:

A method for co-producing biogas by fermenting ethanol with bagasse-molasses-yam slag mixed raw materials comprises the following steps:

S1, bagasse pretreatment: crushing bagasse, adding an alkali solution, washing with water, and drying to obtain pretreated bagasse;

S2, mixed fermentation: taking the pretreated bagasse, the dioscorea composita residue and molasses, saccharifying the dioscorea composita residue, uniformly mixing the pretreated bagasse, the saccharified dioscorea composita residue and molasses, adding yeast activation solution and cellulase, and performing synchronous saccharification and fermentation to produce ethanol; weighing the pretreated bagasse, the dioscorea composita residue and the molasses according to the solid-liquid ratio of 12-44%;

S3, anaerobic fermentation: after synchronous saccharification and fermentation, removing ethanol, inoculating anaerobic sludge, and performing biogas fermentation.

The invention provides a method for co-producing biofuel ethanol and biogas by mixing and utilizing bagasse, dioscorea composita residue and molasses. In the bagasse enzymatic hydrolysate, except sugar and a small amount of inorganic salt, the components are single; the molasses contains rich nutrient components such as nitrogen, phosphorus, vitamins and the like, so that an enough nutrient source can be provided for yeast fermentation, the molasses and the saccharified dioscorea composita residues improve the flowability of a system, the yield of ethanol is improved, the viscosity of waste liquid is reduced, the dioscorea composita residues replace the problem of unbalanced production of the molasses and bagasse, and the waste liquid after fermentation is more suitable for producing methane through anaerobic fermentation due to the mixing of multiple raw materials. After the ethanol in the mixed fermentation waste liquid is recovered, the fermented concentrated grains are continuously subjected to anaerobic fermentation to produce the methane, so that the problem of difficulty in treatment of the waste liquid is solved, and the utilization of waste resources is realized. In addition, the molasses fermentation does not need pretreatment and pre-saccharification, so that the process flow of producing ethanol by mixed fermentation is reduced, and the production cost is reduced.

Preferably, the pretreated bagasse, dioscorea composita residue and molasses in step S2 are weighed according to the solid-to-liquid ratio of 12-36%; for example, 12% to 24%, 24% to 36%.

More preferably, the mass of the bagasse and the molasses after pretreatment in step S2 is weighed so that the solid-to-liquid ratio is 12%.

Preferably, the mass ratio of the bagasse after pretreatment, the dioscorea composita residue and the molasses in the step S2 is (1-5): (0.5-0.9): (0.1 to 0.5); for example: (1-5): 0.5:0.5, 1:0.5: 05.

Preferably, step S2 is to perform mixed fermentation on the pretreated bagasse, saccharified dioscorea composita residue and molasses in a fed-batch manner. The problems of difficult stirring and mixing, limited mass transfer, prolonged fermentation time and the like during ethanol production by high-load fermentation can be well solved by utilizing fed-batch fermentation; the concentration and yield of the ethanol are improved by improving the fluidity of the fermentation system.

Preferably, the fed-batch mode is that 1/3 of pretreated bagasse, dioscorea composita residue and 1/2 of water are added into a fermentation vessel at the beginning of the reaction; when the reaction is carried out for 12 hours, 1/3 of pretreated bagasse is added into a fermentation container; at the time of 24 hours of reaction, 1/3 of the pretreated bagasse, molasses and 1/2 of the water were added to a fermentation vessel.

More preferably, tween80, which is 10% of the total mass of the bagasse, the dioscorea composita residue and the molasses after the pretreatment, is simultaneously added at the time of initial feeding of the reaction. The fed batch was carried out at high load, the fluidity of the system was increased due to the batch addition of the material at different time periods, and the cellulase contact with the material was increased after the addition of tween80, and the concentration and yield of ethanol were increased accordingly.

preferably, when fed-batch is adopted, the pretreated bagasse, the dioscorea composita residue and the molasses in the step S2 are weighed according to the solid-liquid ratio of 36-44%.

preferably, the molasses in the step S2 is waste molasses in sugar industry.

Preferably, the yeast activation solution in step S2 is a saccharomyces cerevisiae activation solution.

Preferably, the yeast concentration of the saccharomyces cerevisiae activation solution in the step S2 is 2.5-5 g/L.

More preferably, the yeast concentration of the saccharomyces cerevisiae activation solution in the step S2 is 3.3 g/L.

Preferably, the cellulase in the step S2 is 10-30 FPU/g pretreated bagasse.

More preferably, the cellulase enzyme in step S2 is 15FPU/g pretreated bagasse.

Preferably, the temperature of the simultaneous saccharification and fermentation in the step S2 is 30-38 ℃, the rotation speed is 100-200 rpm, and the time is 48-144 h.

More preferably, the temperature of the simultaneous saccharification and fermentation in the step S2 is 34 ℃, the rotation speed is 120rpm, and the time is 120 h.

Preferably, the mass of the bagasse and the molasses after the pretreatment in the step S3 is weighed with the solid-to-liquid ratio of 12% -44%.

More preferably, the mass ratio of the bagasse after pretreatment, the dioscorea composita residue and the molasses in the step S3 is 1:0.5: 0.5.

Preferably, the mass of the bagasse and the molasses after pretreatment in the step S4 is weighed with the solid-to-liquid ratio of 36-44%.

More preferably, the mass ratio of the bagasse after pretreatment, the dioscorea composita residue and the molasses in the step S3 is 1:0.5: 0.5.

Preferably, the anaerobic fermentation in step S5 is performed after the high load simultaneous saccharification and fermentation.

Preferably, the anaerobic sludge in the step S5 is inoculated according to the ratio of the inoculum to the volatile solid in the substrate being (1-2) to 1.

More preferably, the anaerobic sludge in step S5 is inoculated at a ratio of inoculum to volatile solids in the substrate of 1: 1.

Preferably, the water washing in step S1 is water washing to neutral.

Preferably, the drying in step S1 is drying to a constant weight.

Preferably, the molasses in step S2 is waste molasses.

Preferably, the alkali solution in step S1 is a NaOH solution.

Preferably, the concentration of the NaOH solution in step S1 is 2%.

Preferably, the NaOH solution is added in step S1 according to a solid-to-liquid ratio of 1: 20.

Preferably, the NaOH solution is added in step S1 and then placed at 80 ℃ for 2 h.

Preferably, the crushing in step S1 is to crush the bagasse to 40-60 mesh.

The method for co-producing the ethanol and the methane comprises the following specific steps:

(1) Pretreatment of bagasse raw materials: weighing absolutely dry bagasse raw materials, adding 2% NaOH solution according to a solid-liquid ratio of 1: 20, processing at 80 ℃ for 2h, and then washing with water to be neutral to obtain pretreated bagasse;

(2) Mixing and fermenting: according to the solid-liquid ratio of 12-44% (W/V), the ratio of (1-5): (0.5-0.9): (0.1-0.5) weighing pretreated bagasse, dioscorea composita residue and waste molasses according to the proportion; sterilizing Dioscorea composita residue at 121 deg.C for 20min, adding deionized water at 250g/L, adjusting pH to 5.5 with NaOH, pre-gelatinizing at 85 deg.C for 30min, adding liquefying enzyme (150U/g), and liquefying at 85 deg.C for 2 hr; h₂SO₄Adjusting pH to 4.5, adding saccharifying enzyme (20U/g), and saccharifying in 60 deg.C water bath for 2 hr; uniformly mixing the pretreated bagasse, saccharified dioscorea composita residue and molasses, adding yeast activation solution with initial yeast cell concentration of 3.3g/L and 15FPU (fermented cellulose) of cellulase according to the amount of the pretreated bagasse per gram, controlling the temperature of a reaction system to be 34 ℃ and the rotating speed to be 120rpm, and performing synchronous saccharification and fermentation in a batch mode, a batch mode and a batch + tween80 mode respectively;

(3) Anaerobic fermentation to produce methane: after the synchronous saccharification and fermentation is finished, removing ethanol, and inoculating anaerobic sludge according to the ratio of 1:1 of the inoculum to volatile solids in the substrate for biogas fermentation.

Compared with the prior art, the invention has the beneficial effects that:

the method for co-producing ethanol and methane by taking bagasse, dioscorea composita residue and molasses as raw materials improves the yield of ethanol and effectively utilizes waste liquid to produce methane. The molasses and the saccharified dioscorea composita residue reduce the viscosity of the waste liquid, so that the waste liquid after mixed fermentation can be subjected to anaerobic fermentation to produce methane, meanwhile, the dioscorea composita residue replaces the problem of unbalanced production of molasses and bagasse, and the waste liquid after fermentation is more suitable for anaerobic fermentation to produce methane by mixing multiple raw materials, so that methane can be efficiently produced, and VS and COD can be effectively removed. In addition, the invention utilizes fed-batch to solve the problems of difficult stirring and mixing, limited mass transfer, prolonged fermentation time and the like when ethanol is produced by high-load fermentation; the concentration and yield of the ethanol are improved by improving the fluidity of the fermentation system. The invention not only solves the problems of low ethanol fermentation yield and difficult waste liquid treatment, but also realizes the utilization of waste resources.

Detailed Description

The present invention will be further described with reference to specific embodiments, but the embodiments of the present invention are not limited thereto. The raw materials in the examples are all commercially available; reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Bagasse pretreatment: weighing absolutely dry bagasse raw materials, adding 2% NaOH solution according to a solid-liquid ratio of 1: 20, processing at 80 ℃ for 2h, and then washing with water to be neutral to obtain the pretreated bagasse.

The molasses is waste molasses, the cellulase is obtained from Shanghai leaf Biotechnology GmbH, the Saccharomyces cerevisiae is obtained from Angel Yeast GmbH, the ethanol content in the reaction solution is analyzed by high performance liquid chromatography, and the methane content is analyzed by AMPTS-II-full-automatic methane potential testing system.

Saccharifying the dioscorea composita residues: weighing a certain amount of dioscorea composita residues, placing into an autoclave for sterilization at 121 ℃ for 20min, adding deionized water at a ratio of 250g/L on a clean bench, adjusting pH to 5.5 with NaOH, pre-gelatinizing in a water bath kettle at 85 ℃ for 30min, adding liquefying enzyme (150U/g), and liquefying in the water bath kettle at 85 ℃ for 2 h; h₂SO₄Adjusting pH to 4.5, adding saccharifying enzyme (20U/g), and saccharifying in water bath at 60 deg.C for 2 hr.

preparation of yeast activation liquid: weighing 2g of glucose, dissolving in 100mL of deionized water, inoculating 6.6g of yeast powder, and activating on a shaker at 160 rpm: firstly, 36 ℃ for 10 min; ② 34 ℃ and 1 h.

The ethanol yield was calculated as follows: