Method for anaerobically fermenting organic solid waste

Abstract

Provided herein is a method for anaerobically fermenting an organic solid waste, including: subjecting the organic solid waste to anaerobic fermentation under catalysis of a zirconium-based metal organic framework (MOF) material.

Claims

1. A method for anaerobically fermenting an organic solid waste, comprising: blending the organic solid waste, an anaerobic microorganism and a zirconium-based metal-organic framework (MOF) material uniformly to obtain a mixture; and subjecting the mixture to a closed anaerobic fermentation in an anaerobic fermentation tank to collect biogas produced during the closed anaerobic fermentation; wherein a weight ratio of the organic solid waste to the anaerobic microorganism is 0.5-2:1; an amount of the zirconium-based MOF material is 0.5 g/L; and a solid content of the mixture is less than 10%; and the zirconium-based MOF material is MOF-808 Zr; and the organic solid waste is wet waste, a sludge from a sewage treatment plant, an agricultural straw, a bacterial residue or a combination thereof.

2. The method of claim 1, wherein the anaerobic microorganism is derived from a biogas residue discharged from the anaerobic fermentation tank.

3. The method of claim 1, wherein in an initial operation of the anaerobic fermentation tank, the anaerobic microorganism is a sludge from an anaerobic fermentation tank of a sewage treatment plant or an animal rumen fluid.

4. The method of claim 1, wherein the closed anaerobic fermentation is performed at 37-55° C. under stirring at 80 rpm for 30 days.

5. The method of claim 1, wherein an anaerobic fermentation residue obtained after ending the anaerobic fermentation is subjected to slurry-water separation to collect a biogas residue as an inoculation microorganism for subsequent anaerobic fermentation.

6. The method of claim 5, wherein the slurry-water separation is performed by standing for 12 hours, centrifugal dewatering or plate-frame filter pressing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically illustrates a structure of a system for zirconium-based MOF material-catalyzed anaerobic fermentation of an organic solid waste according to Example 1 of the present disclosure; and

(2) FIG. 2 illustrates comparison of biogas production between the anaerobic fermentation in the presence of the zirconium-based MOF material (Example 1) and the anaerobic fermentation in the absence of the zirconium-based MOF material (Comparative Example 1).

(3) In the drawings: 1, mixing tank; 2, first stirring system; 3, delivery pump; 4, pipeline; 5, feeding port; 6, anaerobic fermentation tank; 7, second stirring system; 8, gas outlet; and 9, mud discharge port.

DETAILED DESCRIPTION OF EMBODIMENTS

(4) The disclosure will be described completely and clearly below with reference to the accompanying drawings and embodiments to make the object, technical solutions, and beneficial effects of the present disclosure clearer. The embodiments provided herein are merely illustrative, and are not intended to limit the scope of the present disclosure.

(5) It should be understood that the terms used herein are only used to describe specific embodiments and are not intend to limit the present disclosure. In addition, as used herein, the numerical range contains any intermediate value between the upper limit and the lower limit of the range. Each smaller range between any stated value or intermediate value within the stated range and any other stated value or intermediate value within the stated range also fall into the scope of the present disclosure. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

(6) Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although the present disclosure only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or test of the present disclosure. All documents mentioned herein are incorporated by reference to disclose and describe methods and/or materials related to the documents.

(7) It should be understood that various improvements and changes made by those skilled in the art without departing from the scope and spirit of the present disclosure shall fall within the scope of the disclosure.

(8) As used herein, terms “comprise”, “include”, “have” and “contain” all represent a non-exclusive inclusion, which means “including but not limited to”.

Example 1

(9) FIG. 1 depicts a schematic structural diagram of anaerobic fermentation of an organic solid waste under catalysis of a zirconium-based metal-organic framework (MOF) material in Example 1, where 1, mixing tank; 2, first stirring system; 3, delivery pump; 4, pipeline; 5, feeding port; 6, anaerobic fermentation tank; 7, second stirring system; 8, gas outlet; and 9, mud discharge port.

(10) The method includes the following steps.

(11) (S1) Preparation of MOF-808 (Zr)

(12) Trimesic acid and zirconium chloride tetrahydrate were weighed to dissolve in a flask containing N,N-dimethylamide/formic acid (volume ratio 1:1), and stirred for 1 h, and then a mixed solution obtained was microwaved at 400 KW for 20 min, and cooled to room temperature to obtain an solid. The solid was filtered, washed, dried, and grounded to obtain a MOF-808 (Zr) powder. In which, a molar ratio of the trimellitic acid to the zirconium chloride tetrahydrate was 1:2.

(13) A chemical formula of the MOF-808 (Zr) was Zr.sub.6O.sub.5(OH).sub.3(BTC).sub.2(HCOO).sub.5(H.sub.2O).sub.2, and the MOF-808 has a particle diameter of 1-1.5 μm, a pore size of 14-18 Å and a specific surface area of 1000±200 m.sup.2/g.

(14) (S2) Anaerobic Fermentation

(15) The organic solid waste (wet waste) to be treated and an anaerobic microorganism (a sludge from an anaerobic fermentation tank of a sewage treatment plant) were added to the mixing tank 1 according to a weight ratio of 1:2, and 0.5 g/L of the MOF-808 (Zr) powder was added to the mixing tank 1. The first stirring system 2 was turned on to stir the organic solid waste to be treated, the MOF-808 (Zr) powder and the anaerobic microorganism uniformly, and water was added to adjust a solid content in the mixing tank 1 to be less than 10% to obtain a mixture. The delivery pump 3 was turned on, and the mixture was injected into the anaerobic fermentation tank 6 through the pipeline 4 through the feeding port 5. The mixture was subjected to a closed anaerobic fermentation in the anaerobic fermentation tank 6 at 50-55° C. for 30 days. The second stirring system 7 of the anaerobic fermentation tank with a stirring rate of 80 rpm was arranged on a top of the anaerobic fermentation tank 6 to fully mix the mixture in the anaerobic fermentation tank 6. The gas outlet 8 was arranged on an upper part of the anaerobic fermentation tank 6 for collecting biogas and detecting the biogas during the closed anaerobic fermentation.

(16) (S3): An anaerobic fermentation residue obtained after the closed anaerobic fermentation was discharged through the mud discharge port 9, and subjected to slurry-water separation to collect a biogas residue as an inoculation microorganism for subsequent anaerobic fermentation. The slurry-water separation is performed by 12-h standing.

Comparative Example 1

(17) Same as Example 1, the difference is that a MOF-808 (Zr) powder is not added in anaerobic fermentation.

(18) FIG. 2 illustrates comparison of biogas production between the anaerobic fermentation in the presence of the zirconium-based MOF material (Example 1) and the anaerobic fermentation in the absence of the zirconium-based MOF material (Comparative Example 1).

(19) It can be clearly seen from FIG. 2 that after adding 0.5 g/L of the zirconium-based MOF material in the anaerobic fermentation, the net cumulative biogas production is 442.47 mL (g.Math.VS) after anaerobic fermentation for 700 h, and a methane content in a headspace after anaerobic digestion is 57.77±5.67; the net cumulative biogas production after anaerobic fermentation without MOF for 700 h is 316.35 mL (g.Math.VS), and a methane content in a headspace after anaerobic digestion is 50.06±6.28. Therefore, the zirconium-based MOF material can significantly improve an efficiency of anaerobic fermentation and increase a production of biogas. The zirconium-based MOF material with biocompatibility is an ideal catalyst to replace biological enzymes. The selected zirconium-based MOF material MOF-808 (Zr) is a rare type of MOFs material that has a high catalytic activity in neutral environment. The MOF-808 (Zr) material in the system catalyzes and accelerates a biological reaction process of anaerobic digestion, which can promote a liquefaction process and a decomposition process of the organic solid waste, and simultaneously promote a methane production activity, increase a methane production and a gas production rate.

(20) Described above are only preferred embodiments of the present disclosure and are not intended to limit the present disclosure. It should be understood that any modifications, replacements and improvements made by those skilled in the art without departing from the spirit and scope of the present disclosure should fall within the scope of the present disclosure defined by the appended claims.