System and method for preparing green liquefied natural gas by utilizing biomass in multiple ways

Abstract

The invention discloses a system and a method for preparing green liquefied natural gas by using biomass in multiple ways, comprising a first biogas preparation system, an electric natural gas system and a second biogas preparation system, the first biogas preparation system comprises an anaerobic fermentation device, a biogas storage cabinet, a purification device and a first biogas storage tank which are communicated in sequence, and the electric natural gas system comprises a wind-solar power generation system, a water electrolysis device, a first synthesis gas compressor, a first methane synthesis device and an electric natural gas storage tank which are communicated in sequence. The second biogas preparation system comprises a gasification device, a second synthesis gas compressor, a second methane synthesis device and a second biogas storage tank which are communicated in sequence, the biogas storage cabinet and the purification device are communicated with the first synthesis gas compressor, and the anaerobic fermentation device is further communicated with the water electrolysis device and the gasification device. The method has the advantages that biomass resources are fully utilized, and resource waste and carbon emission are reduced.

Description

Technical Field

[0001] This invention relates to the field of biomass energy utilization technology, and in particular to a system and method for producing green liquefied natural gas from biomass through multiple pathways. Background Technology

[0002] my country is a major energy consumer, with natural gas consumption reaching 372.6 billion cubic meters in 2021. 3 Meanwhile, domestic production was only 207.584 billion cubic meters. 3 A significant natural gas shortage has made my country the world's largest importer of natural gas, with an import dependency exceeding 45%. Meanwhile, my country's main biomass resources have an annual output of approximately 3.494 billion tons, projected to increase to 3.795 billion tons by 2030. The biochemical or thermochemical conversion of biomass into renewable natural gas is a green and sustainable energy solution. It can not only fill my country's natural gas gap but also eliminate the environmental impact of biomass waste, demonstrating significant strategic value for energy security and environmental carbon reduction benefits.

[0003] Biomass energy, as a renewable and low-carbon energy source, is an important component of renewable energy and is internationally recognized as a zero-carbon renewable fuel with broad application prospects. my country has explicitly proposed utilizing advanced technologies to convert biomass into high-quality electricity, gas, liquid fuels, and heat. Biomass energy, with its advantages of being green, renewable, and widely distributed, has become an important energy source in the world today. Compared to coal, biomass has very low nitrogen and sulfur content, and its combustion produces SO2 and N2. x O y Biomass energy has low pollutant content and causes less environmental pollution. However, its utilization faces new challenges, including low utilization rates, slow commercial development, and low economic efficiency, all of which hinder its growth. The resource utilization of biomass waste not only facilitates the recycling of biomass and reduces its environmental impact, but also enables the conversion and utilization of carbon resources in carbon-negative biomass, which is of great significance to the "dual-carbon" strategy.

[0004] Currently, the methods for producing liquefied natural gas (LNG) from biomass are relatively limited, mainly relying on the separation and purification of biogas produced during anaerobic fermentation of biomass. This approach fails to fully utilize biomass resources. Furthermore, existing technologies cannot achieve multi-pathway LNG production from biomass, including bio-LNG and electro-LNG, resulting in low biomass resource utilization. Byproducts such as dehydrated biogas residue from anaerobic fermentation and carbon dioxide from biogas separation and purification are not effectively utilized, leading to resource waste. In addition, the carbon dioxide in the flue gas generated from biogas power generation is also not fully utilized, contributing to carbon emissions. Summary of the Invention

[0005] The purpose of this invention is to provide a system and method for producing green liquefied natural gas using multiple pathways from biomass, so as to fully utilize biomass resources and reduce resource waste and carbon emissions.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0007] A system for producing green liquefied natural gas (LNG) using biomass through multiple pathways is characterized by comprising a first biogas production system, an electro-gas production system, and a second biogas production system. The first biogas production system includes an anaerobic fermentation unit, a biogas storage tank, a purification unit, and a first biogas storage tank connected in sequence. The electro-gas production system includes a wind-solar power generation system, a water electrolysis unit, a first syngas compressor, a first methane synthesis unit, and an electro-gas storage tank connected in sequence. The second biogas production system includes a gasification unit, a second syngas compressor, a second methane synthesis unit, and a second biogas storage tank connected in sequence. The biogas storage tank and the purification unit are both connected to the first syngas compressor. The anaerobic fermentation unit is also connected to the water electrolysis unit and the gasification unit, respectively. The water electrolysis unit is also connected to the gasification unit and the second syngas compressor, respectively.

[0008] Preferably, the inlet of the anaerobic fermentation device is also connected to a first pretreatment device, the anaerobic fermentation device is connected to the biogas storage tank by a desulfurization device, and the outlet of the first biogas storage tank is connected in sequence to a first liquefaction device and a first bio-liquefied natural gas storage tank.

[0009] Preferably, the wind and solar power generation system and the water electrolysis device are also connected in parallel to an energy storage device. The water electrolysis device is respectively equipped with a first hydrogen storage tank and a second hydrogen storage tank, which are connected to a first syngas compressor and a second syngas compressor. The outlet of the electro-generated natural gas storage tank is also connected in sequence to a second liquefaction device and an electro-generated liquefied natural gas storage tank.

[0010] Preferably, the inlet of the gasification device is also connected to a second pretreatment device, the gasification device is connected to a syngas purification device, and the outlet of the second biogas storage tank is connected in sequence to a third liquefaction device and a second bio-liquefied natural gas storage tank.

[0011] Preferably, a dewatering machine and a first wastewater treatment unit are connected in sequence between the anaerobic fermentation device and the water electrolysis device, and the first wastewater treatment unit and the water electrolysis device are bidirectionally connected.

[0012] Preferably, a dewatered biogas residue storage tank and a drying machine are connected in sequence between the dewatering machine and the second pretreatment device, and the drying machine is connected to the first sewage treatment unit.

[0013] Preferably, the biogas storage tank is also connected to a biogas generator, and both the biogas generator and the purification device are connected to a carbon dioxide capture device, which is connected to the first syngas compressor.

[0014] Preferably, both the first methane synthesis unit and the second methane synthesis unit are connected to a second wastewater treatment unit, and the second wastewater treatment unit is connected to a water electrolysis unit.

[0015] A method for producing green liquefied natural gas using biomass through multiple pathways, characterized by the following steps:

[0016] Biomass is transported to the first pretreatment unit for sorting, crushing, and impurity removal. After pretreatment, the biomass enters the anaerobic fermentation unit to produce biogas. The biogas produced in the anaerobic fermentation unit enters the desulfurization unit to remove particulate matter and hydrogen sulfide. The desulfurized biogas is temporarily stored in a biogas storage tank. A portion of the biogas enters the purification unit to separate and purify it into biomethane with a methane volume fraction ≥97% and CO2 gas. Another portion of the biogas enters the biogas generator to produce green electricity for plant use. The separated and purified biomethane enters the first biomethane storage tank. Then, through the first liquefaction unit, it is liquefied into bio-liquefied natural gas at -162℃ and enters the first bio-liquefied natural gas storage tank. The carbon dioxide gas separated and removed by the purification unit and the flue gas generated by the biogas generator enter the carbon dioxide capture unit to obtain high-purity carbon dioxide gas. The residue produced by the anaerobic fermentation unit is dewatered to produce biogas slurry and biogas residue. The biogas slurry enters the first sewage treatment unit for treatment. The dewatered biogas residue enters the dewatered biogas residue storage tank for temporary storage. Then the dewatered biogas residue is transported to the dryer for drying to obtain dried biogas residue. The condensate produced by drying enters the first sewage treatment unit.

[0017] The green electricity generated by the wind and solar power system is transmitted to the water electrolysis device, where water electrolysis produces hydrogen and oxygen. Excess electricity generated by the wind and solar power system is stored through an energy storage device. The hydrogen produced by the water electrolysis device enters the first hydrogen storage tank and the second hydrogen storage tank. The first hydrogen storage tank provides the hydrogen required for the preparation of synthetic natural gas by adding carbon dioxide to hydrogen, and the second hydrogen storage tank replenishes the hydrogen required for the preparation of biogas by gasification synthesis gas.

[0018] Hydrogen from the first hydrogen storage tank and carbon dioxide with a volume fraction of ≥99.5% generated by the carbon dioxide capture device enter the first syngas compressor, and then enter the first methane synthesis unit to react and produce electrically generated natural gas. The electrically generated natural gas produced by the first methane synthesis unit enters the electrically generated natural gas storage tank, and then enters the second liquefaction unit, where it is liquefied at -162℃ into electrically generated liquefied natural gas, which then enters the electrically generated liquefied natural gas storage tank.

[0019] After being crushed, granulated, or briquetted by the second pretreatment unit, the dried biogas residue or biomass enters the gasification unit to produce syngas. The ash residue produced by gasification is returned to the field for utilization. After being purified by the purification unit, the syngas, combined with hydrogen supplemented by the second hydrogen storage tank, enters the second syngas compressor for pressurization, and then enters the second methane synthesis unit for chemical catalytic reaction to produce biogas. The biogas produced by the second methane synthesis unit enters the second biogas storage tank, and then enters the third liquefaction unit, where it is liquefied at -162℃ into bioliquefied natural gas and enters the bioliquefied natural gas storage tank.

[0020] The biogas slurry produced by the dewatering machine and the condensate produced by the drying machine enter the first wastewater treatment unit, respectively. The treated water can be used to supply water to the water electrolysis unit. The wastewater produced by the first methane synthesis unit and the second methane synthesis unit enters the second wastewater treatment unit, respectively. The wastewater is treated and reused to supply water to the water electrolysis unit. Part of the oxygen produced by the water electrolysis unit is used for the oxygen required by the gasification unit, and the other part of the oxygen is used for the oxygen required by the biochemical treatment in the first wastewater treatment unit.

[0021] Preferably, the anaerobic fermentation temperature is controlled at 33–38°C or 52–57°C, the residence time is controlled at 20–40 days, the volume ratio of hydrogen to carbon dioxide in the first syngas compressor is 4:1, the pressure of the first syngas compressor and the first methane synthesis unit is controlled at 2–6 MPa, the temperature of the first methane synthesis unit is controlled at 250–650°C, the pressure of the gasification unit is controlled at atmospheric pressure or 1–3 MPa, and the temperature is controlled at 600–900°C, the volume ratio of syngas CO to H2 in the second syngas compressor is 1:3, the pressure of the second syngas compressor and the second methane synthesis unit is controlled at 2–4 MPa, and the temperature of the second methane synthesis unit is controlled at 250–750°C.

[0022] In summary, the present invention has the following beneficial effects:

[0023] 1. The present invention proposes a multi-pathway approach to the production of green liquefied natural gas from biomass. Through the innovation and organic synergy of multiple technologies such as anaerobic fermentation, gasification, methanation synthesis, and natural gas liquefaction, green liquefied natural gas is produced, including bio-liquefied natural gas (Bio-LNG) and electro-liquefied natural gas (e-LNG). This achieves the efficient utilization of biomass and the consumption of renewable energy, and has a very broad prospect for promotion and application.

[0024] 2. This invention captures carbon dioxide separated and purified by anaerobic fermentation of biomass and carbon dioxide generated from biogas power generation. The high-purity carbon dioxide obtained is then used to produce liquefied natural gas by electrolysis of water. This achieves the resource utilization of carbon dioxide, increases the added value of carbon dioxide, and reduces the carbon emissions of the products.

[0025] 3. In this invention, the dehydrated biogas residue after anaerobic fermentation is dried to produce dried biogas residue. The dried biogas residue is then fed into a gasification device to produce syngas, which is then methanated to produce biogas. Finally, it is liquefied to produce bio-liquefied natural gas, thereby realizing the high-value utilization of biogas residue after anaerobic fermentation.

[0026] 4. This invention treats the biogas slurry produced by anaerobic fermentation, the condensate produced by drying biogas residue, and the wastewater produced by methane synthesis, and then uses the treated wastewater to supply water to the water electrolysis device, achieving efficient reuse of water resources. At the same time, the oxygen produced by the water electrolysis device can be used not only to supply the oxygen required by the gasification device, but also to supply the oxygen required for the biochemical treatment of wastewater, which can effectively improve the efficiency of wastewater treatment. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structural flow of a system and method for preparing green liquefied natural gas using biomass through multiple pathways according to the present invention;

[0028] Wherein: 1 is the first pretreatment unit, 2 is the anaerobic fermentation unit, 3 is the desulfurization unit, 4 is the biogas storage tank, 5 is the purification unit, 6 is the first biogas storage tank, 7 is the first liquefaction unit, 8 is the first bio-liquefied natural gas storage tank, 9 is the dehydrator, 10 is the first sewage treatment unit, 11 is the dehydrated biogas residue storage pond, 12 is the drying machine, 13 is the biogas generator, 14 is the carbon dioxide capture unit, 15 is the first hydrogen storage tank, 16 is the first syngas compressor, 17 is the first methane synthesis unit, 18 is... 19 is an electric natural gas storage tank, 20 is an electric liquefied natural gas storage tank, 21 is a wind and solar power generation system, 22 is an energy storage device, 23 is a water electrolysis device, 24 is a second wastewater treatment unit, 25 is a second pretreatment device, 26 is a gasification device, 27 is a syngas purification device, 28 is a second hydrogen storage tank, 29 is a second syngas compressor, 30 is a second methane synthesis device, 31 is a second biogas storage tank, 32 is a third liquefaction device, and 33 is a second bio-liquefied natural gas storage tank. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. These embodiments do not constitute a limitation on the present invention.

[0030] like Figure 1The system shown is a multi-pathway system for producing green liquefied natural gas using biomass, comprising a first biogas production system, an electro-gas production system, and a second biogas production system. The first biogas production system includes an anaerobic fermentation unit 2, a biogas storage tank 4, a purification unit 5, and a first biogas storage tank 6 connected in sequence. The electro-gas production system includes a wind-solar power generation system 21, a water electrolysis unit 23, a first syngas compressor 16, a first methane synthesis unit 17, and an electro-gas storage tank 18 connected in sequence. The second biogas production system includes a gasification unit 26, a second syngas compressor 29, a second methane synthesis unit 30, and a second biogas storage tank 31 connected in sequence. The biogas storage tank 4 and the purification unit 5 are both connected to the first syngas compressor 16. The anaerobic fermentation unit 2 is also connected to the water electrolysis unit 23 and the gasification unit 26, respectively. The water electrolysis unit 23 is also connected to the gasification unit 26 and the second syngas compressor 29, respectively.

[0031] The inlet of the anaerobic fermentation device 2 is also connected to the first pretreatment device 1, and the anaerobic fermentation device 2 is connected to the biogas storage tank 4 by a desulfurization device 3. The outlet of the first biogas storage tank 6 is also connected to the first liquefaction device 7 and the first bio-liquefied natural gas storage tank 8 in sequence.

[0032] The wind and solar power generation system 21 and the water electrolysis device 23 are also connected in parallel to an energy storage device 22. The water electrolysis device 23 is equipped with a first hydrogen storage tank 15, a second hydrogen storage tank 28, and is connected to a first syngas compressor 16 and a second syngas compressor 29. The outlet of the electric natural gas storage tank 18 is also connected to a second liquefaction device 19 and an electric liquefied natural gas storage tank 18 in sequence.

[0033] The inlet of the gasification unit 26 is also connected to the second pretreatment unit 25, and the gasification unit 26 and the second syngas compressor 29 are connected to the syngas purification unit 27. The outlet of the second biogas storage tank 31 is also connected to the third liquefaction unit 32 and the second bio-liquefied natural gas storage tank 33 in sequence.

[0034] The anaerobic fermentation device 2 and the water electrolysis device 23 are also connected in sequence to a dewatering machine 9 and a first sewage treatment unit 10, and the first sewage treatment unit 10 and the water electrolysis device 23 are bidirectionally connected.

[0035] The dewatering machine 9 and the second pretreatment device 25 are also connected in sequence to the dewatering biogas residue storage tank 11 and the drying machine 12, and the drying machine 12 is connected to the first sewage treatment unit 10.

[0036] The biogas storage tank 4 is also connected to the biogas generator 13. The biogas generator 13 and the purification device 5 are both connected to the carbon dioxide capture device 14. The carbon dioxide capture device 14 is connected to the first syngas compressor 16.

[0037] Both the first methane synthesis unit 17 and the second methane synthesis unit 30 are connected to a second wastewater treatment unit 24, which is connected to a water electrolysis unit 23.

[0038] A method for producing green liquefied natural gas using biomass through multiple pathways specifically includes the following steps:

[0039] Biomass is transported to the first pretreatment unit 1 for sorting, crushing, and impurity removal. After pretreatment, the biomass enters the anaerobic fermentation unit 2 to produce biogas. The temperature of the anaerobic fermentation is controlled at 33–38℃ or 52–57℃, and the residence time is controlled at 20–40 days. The biogas produced by the anaerobic fermentation unit enters the desulfurization unit 3 to remove particulate matter and hydrogen sulfide. The desulfurized biogas is temporarily stored in the biogas storage tank 4. A portion of the biogas enters the purification unit 5 to separate and purify the biogas into biomethane with a methane volume fraction ≥97% and CO2 gas. A portion of the biogas enters the biogas generator 13 to generate green electricity for plant use. Natural gas enters the first biogas storage tank 6, and then passes through the first liquefaction unit 7, where it is liquefied into bio-liquefied natural gas at -162℃ and enters the first bio-liquefied natural gas storage tank 8. The carbon dioxide gas separated and removed by the purification unit 5 and the flue gas generated by the biogas generator 13 enter the carbon dioxide capture unit 14 to obtain high-purity carbon dioxide gas. The residue produced by the anaerobic fermentation unit 2 passes through the dewatering machine 9 to produce biogas slurry and biogas residue. The biogas slurry enters the first sewage treatment unit 10 for treatment, and the dewatered biogas residue enters the dewatered biogas residue storage tank 11 for temporary storage. Then, the dewatered biogas residue is transported to the drying machine 12 for drying to obtain dried biogas residue. The condensate produced during drying enters the first sewage treatment unit 10.

[0040] The green electricity generated by the wind and solar power generation system 21 is transmitted to the water electrolysis device 23. The water electrolysis produces hydrogen and oxygen. Excess electricity generated by the wind and solar power generation system 21 is stored through the energy storage device 22. When the electricity output by the wind and solar power generation system 21 exceeds the electricity required by the water electrolysis device 23, the excess electricity is stored through the energy storage device 22 or output to the external power grid. When the electricity output by the wind and solar power generation system 21 is insufficient, the energy storage device 22 supplements the electricity required by the water electrolysis device 23. The electricity generated by the wind and solar power generation system 21 can basically meet the electricity required by the water electrolysis device 23. The hydrogen produced by the water electrolysis device 23 enters the first hydrogen storage tank 15 and the second hydrogen storage tank 28 for downstream methane synthesis. The first hydrogen storage tank 15 provides the hydrogen required for the synthesis of synthetic natural gas from carbon dioxide hydrogenation, and the second hydrogen storage tank 28 supplements the hydrogen required for the synthesis of biogas from gasification syngas.

[0041] Hydrogen from the first hydrogen storage tank 15 and high-purity carbon dioxide (≥99.5% by volume) generated by the carbon dioxide capture device 14 enter the first syngas compressor 16 at a volume ratio of 4:1. The syngas is pressurized to 2-6 MPa and enters the first methane synthesis unit 17 to produce electrically generated natural gas. The main chemical reaction is: CO2 + 4H2 → CH4 + 2H2O. The pressure of the first methane synthesis unit 17 is controlled at 2-6 MPa and the temperature is controlled at 250-650℃. The steam recovered from the first methane synthesis unit 17 is used as plant steam to supply the anaerobic fermentation unit 2 for heat preservation and the gasification unit 26 for syngas production. It can also be used as steam for the drying machine 12 to dry biogas residue. The electrically generated natural gas produced by the first methane synthesis unit 17 enters the electrically generated natural gas storage tank 18, and then enters the second liquefaction unit 19, where it is liquefied at -162℃ into electrically generated liquefied natural gas, which then enters the electrically generated liquefied natural gas storage tank 18.

[0042] Dried biogas residue or biomass is crushed, granulated, or briquetted in the second pretreatment unit 25 before entering the gasification unit 26 to produce syngas. The reaction pressure in the gasification unit 26 is controlled at atmospheric pressure or 1-3 MPa, and the temperature is controlled at 600-900℃. The ash residue produced by gasification is returned to the field for utilization. After purification by the purification unit, the syngas, combined with hydrogen supplemented by the second hydrogen storage tank 28, enters the second syngas compressor 29 at a syngas CO:H2 volume ratio of 1:3 and is pressurized to 2-4 MPa. Then it enters the second methane synthesis unit 30 for chemical catalytic reaction to produce biogas. The main chemical reaction formula is... CO + 3H2 → CH4 + H2O. The pressure of the second methane synthesis unit 30 is controlled at 2-4 MPa, and the temperature is controlled at 250-700℃. The steam generated by the second methane synthesis unit 30 can be used as plant steam to supply the anaerobic fermentation unit 2 for heat preservation and the gasification unit 26 for the preparation of syngas. It can also be used as steam for the drying machine 12 to dry the biogas residue. The biogas produced by the second methane synthesis unit 30 enters the second biogas storage tank 31, and then the biogas enters the third liquefaction unit 32, where it is liquefied into bio-liquefied natural gas at -162℃ and enters the bio-liquefied natural gas storage tank.

[0043] The biogas slurry produced by the dewatering machine 9 and the condensate produced by the drying machine 12 enter the first wastewater treatment unit 10, respectively. The treated water can be used to supply water to the water electrolysis device 23. The wastewater produced by the first methane synthesis device 17 and the second methane synthesis device 30 enters the second wastewater treatment unit 24, respectively. The wastewater is treated and reused to supply water to the water electrolysis device 23. Part of the oxygen produced by the water electrolysis device 23 is used for the oxygen required by the gasification device 26, and the other part of the oxygen is used for the oxygen required for biochemical treatment in the first wastewater treatment unit 10.

[0044] The invention proposes a multi-pathway approach to producing green liquefied natural gas from biomass. Through the innovation and organic synergy of multiple technologies such as anaerobic fermentation, gasification, methanation synthesis, and natural gas liquefaction, green liquefied natural gas is produced, including bio-liquefied natural gas (Bio-LNG) and electro-liquefied natural gas (e-LNG). This achieves efficient utilization of biomass and consumption of renewable energy, and has a very broad prospect for promotion and application.

[0045] This invention captures carbon dioxide separated and purified from biomass anaerobic fermentation and carbon dioxide generated from biogas power generation. The high-purity carbon dioxide obtained is then used to produce electrolytic liquefied natural gas with hydrogen generated from water electrolysis. This achieves the resource utilization of carbon dioxide, increases the added value of carbon dioxide, and reduces the carbon emissions of the products.

[0046] In this invention, the dehydrated biogas residue after anaerobic fermentation is dried to produce dried biogas residue. The dried biogas residue is then fed into a gasification device to produce syngas, which is then methanated to produce biogas. Finally, it is liquefied to produce bio-liquefied natural gas, thereby achieving high-value utilization of biogas residue after anaerobic fermentation.

[0047] This invention treats the biogas slurry from anaerobic fermentation, the condensate from the drying of biogas residue, and the wastewater from methane synthesis, and then uses the treated wastewater to supply water to an electrolysis water device, achieving efficient water resource reuse. At the same time, the oxygen generated by the electrolysis water device can be used not only to supply the oxygen required by the gasification device, but also to supply the oxygen required for the biochemical treatment of wastewater, which can effectively improve the efficiency of wastewater treatment.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within the scope of its essence and protection. Such modifications or equivalent substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A system for producing green liquefied natural gas using multiple pathways from biomass, characterized in that, The system includes a first biogas production system, an electro-gas production system, and a second biogas production system. The first biogas production system comprises an anaerobic fermentation unit, a biogas storage tank, a purification unit, and a first biogas storage tank connected in sequence. The electro-gas production system comprises a wind and solar power generation system, a water electrolysis unit, a first syngas compressor, a first methane synthesis unit, and an electro-gas storage tank connected in sequence. The second biogas production system comprises a gasification unit, a second syngas compressor, a second methane synthesis unit, and a second biogas storage tank connected in sequence. The biogas storage tank and the purification unit are both connected to the first syngas compressor. The anaerobic fermentation unit is also connected to the water electrolysis unit and the gasification unit, respectively. The water electrolysis unit is also connected to the gasification unit and the second syngas compressor, respectively.

2. The system for producing green liquefied natural gas using multiple pathways from biomass according to claim 1, characterized in that: The inlet of the anaerobic fermentation device is also connected to a first pretreatment device, and a desulfurization device is connected between the anaerobic fermentation device and the biogas storage tank. The outlet of the first biogas storage tank is also connected in sequence to a first liquefaction device and a first bio-liquefied natural gas storage tank.

3. The system for producing green liquefied natural gas using biomass through multiple pathways according to claim 1, characterized in that: The wind and solar power generation system and the water electrolysis device are also connected in parallel to an energy storage device. The water electrolysis device is equipped with a first hydrogen storage tank, a second hydrogen storage tank, and a first syngas compressor and a second syngas compressor, respectively. The outlet of the electric natural gas storage tank is also connected in sequence to a second liquefaction device and an electric liquefied natural gas storage tank.

4. A system for producing green liquefied natural gas using biomass through multiple pathways according to claim 1, characterized in that: The inlet of the gasification device is also connected to a second pretreatment device, and a syngas purification device is connected between the gasification device and the second syngas compressor. The outlet of the second biogas storage tank is also connected in sequence to a third liquefaction device and a second bio-liquefied natural gas storage tank.

5. A system for producing green liquefied natural gas using biomass through multiple pathways according to claim 4, characterized in that: The anaerobic fermentation device and the water electrolysis device are also connected in sequence to a dewatering machine and a first wastewater treatment unit, and the first wastewater treatment unit and the water electrolysis device are bidirectionally connected.

6. A system for producing green liquefied natural gas using biomass through multiple pathways according to claim 5, characterized in that: The dewatering machine and the second pretreatment device are also connected in sequence to a dewatered biogas residue storage tank and a drying machine, and the drying machine is connected to the first sewage treatment unit.

7. A system for producing green liquefied natural gas using biomass through multiple pathways according to claim 1, characterized in that: The biogas storage tank is also connected to a biogas generator, and both the biogas generator and the purification device are connected to a carbon dioxide capture device, which is connected to the first syngas compressor.

8. A system for producing green liquefied natural gas using multiple pathways from biomass according to claim 1, characterized in that: Both the first methane synthesis unit and the second methane synthesis unit are connected to a second wastewater treatment unit, which is connected to a water electrolysis unit.

9. A method for producing green liquefied natural gas using biomass through multiple pathways, characterized in that, Specifically, the steps include the following: Biomass is transported to the first pretreatment unit for sorting, crushing, and impurity removal. After pretreatment, the biomass enters the anaerobic fermentation unit to produce biogas. The biogas produced in the anaerobic fermentation unit enters the desulfurization unit to remove particulate matter and hydrogen sulfide. The desulfurized biogas is temporarily stored in a biogas storage tank. A portion of the biogas enters the purification unit to separate and purify it into biomethane with a methane volume fraction ≥97% and CO2 gas. Another portion of the biogas enters the biogas generator to produce green electricity for plant use. The separated and purified biomethane enters the first biomethane storage tank. Then, through the first liquefaction unit, it is liquefied into bio-liquefied natural gas at -162℃ and enters the first bio-liquefied natural gas storage tank. The carbon dioxide gas separated and removed by the purification unit and the flue gas generated by the biogas generator enter the carbon dioxide capture unit to obtain high-purity carbon dioxide gas. The residue produced by the anaerobic fermentation unit is dewatered to produce biogas slurry and biogas residue. The biogas slurry enters the first sewage treatment unit for treatment. The dewatered biogas residue enters the dewatered biogas residue storage tank for temporary storage. Then the dewatered biogas residue is transported to the dryer for drying to obtain dried biogas residue. The condensate produced by drying enters the first sewage treatment unit. The green electricity generated by the wind and solar power system is transmitted to the water electrolysis device, where water electrolysis produces hydrogen and oxygen. Excess electricity generated by the wind and solar power system is stored through an energy storage device. The hydrogen produced by the water electrolysis device enters the first hydrogen storage tank and the second hydrogen storage tank. The first hydrogen storage tank provides the hydrogen required for the preparation of synthetic natural gas by adding carbon dioxide to hydrogen, and the second hydrogen storage tank replenishes the hydrogen required for the preparation of biogas by gasification synthesis gas. Hydrogen from the first hydrogen storage tank and carbon dioxide with a volume fraction of ≥99.5% generated by the carbon dioxide capture device enter the first syngas compressor, and then enter the first methane synthesis unit to react and produce electrically generated natural gas. The electrically generated natural gas produced by the first methane synthesis unit enters the electrically generated natural gas storage tank, and then enters the second liquefaction unit, where it is liquefied at -162℃ into electrically generated liquefied natural gas, which then enters the electrically generated liquefied natural gas storage tank. After being crushed, granulated, or briquetted by the second pretreatment unit, the dried biogas residue or biomass enters the gasification unit to produce syngas. The ash residue produced by gasification is returned to the field for utilization. After being purified by the purification unit, the syngas, combined with hydrogen supplemented by the second hydrogen storage tank, enters the second syngas compressor for pressurization, and then enters the second methane synthesis unit for chemical catalytic reaction to produce biogas. The biogas produced by the second methane synthesis unit enters the second biogas storage tank, and then enters the third liquefaction unit, where it is liquefied at -162℃ into bioliquefied natural gas and enters the bioliquefied natural gas storage tank. The biogas slurry produced by the dewatering machine and the condensate produced by the drying machine enter the first wastewater treatment unit, respectively. The treated water can be used to supply water to the water electrolysis unit. The wastewater produced by the first methane synthesis unit and the second methane synthesis unit enters the second wastewater treatment unit, respectively. The wastewater is treated and reused to supply water to the water electrolysis unit. Part of the oxygen produced by the water electrolysis unit is used for the oxygen required by the gasification unit, and the other part of the oxygen is used for the oxygen required by the biochemical treatment in the first wastewater treatment unit.

10. A method for preparing green liquefied natural gas using biomass through multiple pathways according to claim 1, characterized in that: The anaerobic fermentation temperature is controlled at 33–38°C or 52–57°C, and the residence time is controlled at 20–40 days. The volume ratio of hydrogen to carbon dioxide in the first syngas compressor is 4:

1. The pressure of the first syngas compressor and the first methane synthesis unit is controlled at 2–6 MPa. The temperature of the first methane synthesis unit is controlled at 250–650°C. The pressure of the gasification unit is controlled at atmospheric pressure or 1–3 MPa, and the temperature is controlled at 600–900°C. The volume ratio of syngas CO to H2 in the second syngas compressor is 1:

3. The pressure of the second syngas compressor and the second methane synthesis unit is controlled at 2–4 MPa. The temperature of the second methane synthesis unit is controlled at 250–750°C.

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