CN117120623B

CN117120623B - Flexible fermentation platform for improved conversion of carbon dioxide to products

Info

Publication number: CN117120623B
Application number: CN202280026187.5A
Authority: CN
Inventors: R·J·孔拉多; S·D·辛普森; M·E·马丁; J·C·布罗姆利; D·E·扬斯; R·R·罗辛
Original assignee: Lanzatech Inc
Current assignee: Lanzatech Inc
Priority date: 2021-04-09
Filing date: 2022-04-08
Publication date: 2024-10-18
Anticipated expiration: 2042-04-08
Also published as: CN117120623A; CN117280040A

Abstract

An integrated process and system for producing at least one gaseous fermentation product from a gaseous stream has been developed. The present disclosure provides improved carbon utilization by recycling bioreactor off-gas using a variety of different flow schemes and employing a CO ₂ to CO conversion system, such as a reverse water gas shift unit. Recycling the bioreactor off-gas and employing a CO ₂ to CO conversion process provides an advantageous H ₂ to CO molar ratio of the gas fermentation bioreactor feed to enhance fermentation product production. The bypass embodiment provides the optimal size of the reverse water gas shift unit to minimize cost.

Description

Flexible fermentation platform for improved conversion of carbon dioxide to products

Cross reference to related applications

The present application claims the benefit of U.S. provisional patent application No. 63/173,243, filed on 9 at 4 months 2021, no. 63/173,247, filed on 9 at 4 months 2021, no. 63/173,255, filed on 9 at 4 months 2021, no. 63/173,262, filed on 9 at 4 months 2021, and No. 63/282,546, filed on 23 at 11 months 2021, the entirety of which is incorporated herein by reference.

Technical Field

The present disclosure relates to methods and systems that provide a flexible fermentation platform for improved conversion of CO ₂ to products. In particular, the present disclosure relates to an integrated process and system whereby improved product selectivity benefits are obtained for a gas fermentation platform.

Background

Carbon dioxide (CO ₂) accounts for about 76% of global warming emissions caused by human activity, with methane (16%), nitrous oxide (6%) and fluorinated gases (2%) accounting for the remainder (national environmental protection agency (United States Environmental Protection Agency)). Most of the CO ₂ comes from burning fossil fuels to produce energy, but industrial and forestry practices also emit CO ₂ into the atmosphere. Reduction of greenhouse gas emissions, particularly CO ₂, is critical to prevent the progression of global warming and the accompanying climate and weather changes.

It has long been recognized that catalytic processes, such as Fischer-Tropsch processes, can be used to convert gases containing carbon dioxide (CO ₂), carbon monoxide (CO), and or hydrogen (H ₂) into various fuels and chemicals. However, recently, gas fermentation has become an alternative platform for the biological fixation of such gases. In particular, anaerobic C1-immobilized microorganisms have been demonstrated to convert gases containing CO ₂, CO, and or H ₂ (such as industrial waste gas or syngas or mixtures thereof) to products such as ethanol and 2, 3-butanediol. However, the effective production of such products may be limited, for example, by slow microbial growth, limited gas absorption, sensitivity to toxins, or conversion of carbon substrates to unwanted byproducts.

Typically, the substrate and/or the C1 carbon source serves as part or the sole source of carbon, which may originate from exhaust gas obtained as a by-product of an industrial process or from another source, such as internal combustion engine exhaust gas, CO ₂ by-product gas from ammonia production of an industrial process (cement production), by-product gas from syngas cleanup, ethylene production, ethylene oxide production, methanol synthesis, exhaust gas from fermentation processes (e.g. converting sugar to ethanol), biogas, landfill gas, direct air capture, mined CO ₂ (fossil CO ₂), or from electrolysis. The substrate and or the C1 carbon source may be synthesis gas produced by pyrolysis, torrefaction, reforming or gasification. In other words, the carbon in the waste material may be recycled by pyrolysis, torrefaction, reforming, or gasification to produce syngas for use as a substrate and or a C1 carbon source. The substrate and or the C1 carbon source may be a gas comprising methane, and in certain embodiments, the substrate and or the C1 carbon source may be a non-exhaust gas.

Exhaust gases obtained from industrial processes or synthesis gas produced from a synthesis gas source may need to be treated or decomposed to be suitable for use in a gas fermentation system. It has been shown that high CO ₂ content in industrial and/or synthesis gas adversely affects the ethanol selectivity benefits of fermentation and produces higher yields of undesirable byproducts such as acetate and 2, 3-butanediol.

Thus, there remains a need for a flexible fermentation platform that can reduce the CO ₂ content of industrial gases, synthesis gas, or mixtures thereof prior to introduction into a bioreactor. Furthermore, in some embodiments, it is desirable to convert some of the CO ₂ present in the synthesis gas or industrial gas to CO prior to introduction into the bioreactor to vary and control the H ₂: CO ratio. For example, decreasing the H ₂ to CO ratio can improve microbial growth and increase growth rate, and can provide greater selectivity to fermentation products (e.g., ethanol).

Disclosure of Invention

The present disclosure relates to an integrated process for producing at least one fermentation product from a gaseous stream, the process comprising: a) Obtaining a first gaseous stream comprising hydrogen and a second gaseous stream comprising CO ₂; b) Passing at least a portion of the first gaseous stream and at least a portion of the second gaseous stream to a CO ₂ to CO conversion system operating under conditions that produce a CO-rich effluent stream; c) Passing the CO-enriched effluent stream to a bioreactor having a culture of one or more C1 immobilized bacteria and fermenting to produce at least one fermentation product stream and a bioreactor tail gas stream; d) Compressing the bioreactor off-gas stream to produce a compressed bioreactor off-gas stream; e) Passing at least a first portion of the compressed bioreactor tail gas stream in any order: a gas desulfurization and/or acid gas removal unit; or a gas component removal unit; or both a gas desulfurization and or acid gas removal unit and a gas component removal unit to produce a compressed treated bioreactor tail gas stream; f) Recycling the compressed treated bioreactor off-gas stream: to be combined with the first gaseous stream, the second gaseous stream, or a combination thereof; or recycled to the CO ₂ to CO conversion system combination; or to be combined with the CO-rich effluent stream; or any combination thereof; and g) optionally recycling a second portion of the compressed bioreactor tail gas stream for combination with a CO-rich effluent stream or for combination with the bioreactor. The method may further comprise combining at least a second portion of the first gaseous stream, at least a second portion of the second gaseous stream, or a combination thereof with the CO-rich effluent stream. the method may further comprise passing at least a second portion of the first gaseous stream, at least a second portion of the second gaseous stream, or a combination thereof to the bioreactor. The method may further comprise compressing any portion of the first gaseous stream, the second gaseous stream, or a combination thereof. The method may further include controlling a relative amount of the first portion of the compressed tail gas stream and the second portion of the compressed tail gas stream using a control valve. The method may further comprise passing at least a portion of the tail gas stream to a tail gas CO ₂ to CO conversion system selected from a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a plasma conversion unit, a gasification unit or a reforming unit to produce a CO-rich effluent stream and recycling a second CO-rich effluent stream to the bioreactor. The CO-enriched effluent stream may comprise H ₂:CO:CO₂ to a molar ratio of about 5:1:1 about 4.5:1:1, about 4.33:1:1, about 3:1:1, about 2:1:1, about 1:1:1, or about 1:3:1. The CO ₂ to CO conversion system may include at least one of: a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a reforming unit or a plasma conversion unit. The at least one fermentation product may be selected from ethanol, acetate, butanol, butyrate, 2, 3-butanediol, lactate, butene, butadiene, methyl ethyl ketone, ethylene, acetone, isopropanol, lipids, 3-hydroxypropionate, isoprene, fatty acids, 2-butanol, 1, 2-propanediol, hexanol, octanol, or 1-propanol. The first gaseous stream comprising hydrogen may be generated by a hydrogen generation source comprising at least one of: a water electrolyzer, a hydrocarbon reforming source, a hydrogen purification source, a solid biomass gasification source, a solid waste gasification source, a coal gasification source, a hydrocarbon gasification source, a methane pyrolysis source, a refinery tail gas generation source, a plasma reforming reactor, a partial oxidation reactor, or any combination thereof. The second gaseous stream comprising CO ₂ may be generated by a gas generation source comprising at least one of: a sugar-based ethanol generation source, a first generation corn ethanol generation source, a second generation corn ethanol generation source, a sugar cane ethanol generation source, a sucrose ethanol generation source, a beet ethanol generation source, a molasses ethanol generation source wheat ethanol production source, grain-based ethanol production source, starch-based ethanol production source, cellulose-based ethanol production source, cement production source, methanol synthesis source, An olefin generating source, a steel generating source, a ferroalloy generating source, a refinery off gas generating source, a post-combustion gas generating source, a biogas generating source, a landfill generating source, an ethylene oxide generating source, a methanol generating source, an ammonia generating source, a CO ₂ generating source, a natural gas processing generating source, a gasification source, an organic waste gasification source, a direct air capture, or any combination thereof. The at least one C1-immobilized bacterium may be selected from Clostridium ethanogenum (Clostridium autoethanogenum), clostridium Yankeei (Clostridium ljungdahlii) or Clostridium ramosum (Clostridium ragsdalei).

The present disclosure further relates to an integrated process for producing at least one fermentation product from a gaseous stream, the process comprising: a) Obtaining a first gaseous stream comprising hydrogen and a second gaseous stream comprising CO ₂; b) Optionally, compressing at least a portion of the first gaseous stream, at least a portion of the second gaseous stream, or any combination thereof in a first compressor to produce a compressed first gaseous stream, a compressed second gaseous stream, and or a compressed combination of the first gaseous stream and the second gaseous stream; c) The following are treated in a gas treatment zone comprising a gas component removal unit, a gas desulfurization/acid gas removal unit, or both: at least a portion of the first gaseous stream or the compressed first gaseous stream or both; And at least a portion of the second gaseous stream or the compressed second gaseous stream or both; or the compressed combination of the first gaseous stream and the second gaseous stream; to produce a processed stream; d) Converting CO ₂ in at least a first portion of the treated stream in a CO ₂ to CO conversion system to form CO, the CO ₂ to CO conversion system operating under conditions that produce a CO-rich effluent stream; e) Passing the CO-enriched effluent stream to a bioreactor having a culture of one or more C1 immobilized bacteria and fermenting to produce at least one fermentation product stream and a bioreactor tail gas stream; and f) recycling the tail gas stream to the first compressor, the gas treatment zone, the CO ₂ to CO conversion system, the first gaseous stream, the second gaseous stream, or a combination of the first gaseous stream and the second gaseous stream. The method may further comprise, in combination with the CO-rich effluent stream, at least a portion of: the processed stream; Or the first gaseous stream; or the second gaseous stream; or the combination of the first gaseous stream and the second gaseous stream; or the compressed first gaseous stream; or the compressed second gaseous stream; or the compressed combination of the first gaseous stream and the second gaseous stream; or any combination thereof. The method may further comprise passing at least a portion of the tail gas stream to a tail gas CO ₂ to CO conversion system selected from a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a plasma conversion unit, a gasification unit or a reforming unit to produce a CO-rich effluent stream and recycling a second CO-rich effluent stream to the bioreactor. The CO-rich effluent stream may further comprise hydrogen and CO ₂ and comprise H ₂:CO:CO₂ in a molar ratio of about 5:1:1, about 4.5:1:1, about 4.33:1:1, or about 3:1:1, about 2:1:1, about 1:1:1, or about 1:3:1. The CO ₂ to CO conversion system may include at least one of: a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a reforming unit or a plasma conversion unit. The gas treatment zone may further comprise a deoxygenation unit, a catalytic hydrogenation unit, an adsorption unit, a thermal oxidizer, or any combination thereof. The at least one fermentation product may be selected from ethanol, acetate, butanol, butyrate, 2, 3-butanediol, lactate, butene, butadiene, methyl ethyl ketone, ethylene, acetone, isopropanol, lipids, 3-hydroxypropionate, isoprene, fatty acids, 2-butanol, 1, 2-propanediol, hexanol, octanol, or 1-propanol. The first gaseous stream comprising hydrogen may be generated by a hydrogen generation source comprising at least one of: a water electrolyzer, a hydrocarbon reforming source, a hydrogen purification source, a solid biomass gasification source, a solid waste gasification source, a coal gasification source, a hydrocarbon gasification source, a methane pyrolysis source, a refinery tail gas generation source, a plasma reforming reactor, a partial oxidation reactor, or any combination thereof. The second gaseous stream comprising CO ₂ may be generated by a gas generation source comprising at least one of: a sugar-based ethanol generation source, a first generation corn ethanol generation source, a second generation corn ethanol generation source, a sugar cane ethanol generation source, a sucrose ethanol generation source, a beet ethanol generation source, a molasses ethanol generation source wheat ethanol production source, grain-based ethanol production source, starch-based ethanol production source, cellulose-based ethanol production source, cement production source, methanol synthesis source, An olefin generating source, a steel generating source, a ferroalloy generating source, a refinery off gas generating source, a post-combustion gas generating source, a biogas generating source, a landfill generating source, an ethylene oxide generating source, a methanol generating source, an ammonia generating source, a CO ₂ generating source, a natural gas processing generating source, a gasification source, an organic waste gasification source, a direct air capture, or any combination thereof. at least one of the C1-immobilized bacteria may be selected from clostridium ethanogenum, clostridium yang, or clostridium rakii. The CO-rich effluent stream can include hydrogen, and the method further includes separating hydrogen from the CO-rich effluent stream and recycling the separated hydrogen to be combined with the tail gas stream or recycled to the compressor. The method may further comprise compressing the remainder of the CO-rich effluent stream after hydrogen separation. The tail gas stream may include methane, and the method further includes passing a portion of the tail gas stream to a methanator to produce a methanator effluent, and combining the methanator effluent with the tail gas stream. The method may further include generating a stream comprising oxygen from an oxygen source and passing the stream comprising oxygen to the methane conversion unit. The method may further comprise passing a second gaseous stream comprising hydrogen from the hydrogen source to the bioreactor or merging with the CO-rich effluent stream, passing a second gaseous stream comprising CO ₂ from the CO ₂ source to the bioreactor or merging with the CO-rich effluent stream, or any combination thereof. combining the second gaseous stream from the hydrogen source, which may comprise hydrogen, with the CO-rich effluent stream, or combining the second gaseous stream from the CO ₂ source, which comprises CO ₂, with the CO-rich effluent stream, or both, using mixing in a mixer. The ratio of the second gaseous stream, which may include hydrogen, from the hydrogen source to the CO-rich effluent stream entering the bioreactor is from about greater than 0:1 to about 4:1. The CO ₂ to CO conversion system may include a combustion heater having a burner, and the tail gas stream is recycled to at least the burner of the combustion heater. The CO ₂ to CO conversion system may include a steam generator that produces steam, or a water separation unit that produces a water stream, or both. The method may further comprise passing a portion of the CO-rich effluent stream to an inoculator reactor, a surge tank, or both.

The present disclosure relates to an integrated process for producing at least one fermentation product from a gaseous stream, the process comprising: a) Obtaining a first gaseous stream comprising hydrogen and a second gaseous stream comprising CO ₂; b) Passing at least a portion of the second gaseous stream and optionally a portion of the first gaseous stream to a CO ₂ to CO conversion system operating under conditions that produce a CO-rich effluent stream; c) Passing at least a portion of the first gaseous stream comprising hydrogen and the CO-enriched effluent stream to a bioreactor having a culture of one or more C1 immobilized bacteria and fermenting to produce at least one fermentation product stream and a bioreactor tail gas stream; d) Compressing the bioreactor off-gas stream to produce a compressed bioreactor off-gas stream; e) Passing at least a first portion of the compressed bioreactor tail gas stream in any order: a gas desulfurization and/or acid gas removal unit; or a gas component removal unit; or both a gas desulfurization and or acid gas removal unit and a gas component removal unit to produce a compressed treated bioreactor tail gas stream; f) Recycling the compressed treated bioreactor off-gas stream: to be combined with the first gaseous stream, the second gaseous stream, or a combination thereof; or recycled to the CO ₂ to CO conversion system combination; or to be combined with the CO-rich effluent stream; or any combination thereof; and g) optionally recycling a second portion of the compressed bioreactor tail gas stream for combination with a CO-rich effluent stream or for combination with the bioreactor. The method may further include passing at least another portion of the first gaseous stream comprising hydrogen to the CO ₂ to a CO conversion system. The method may further comprise compressing any portion of the first gaseous stream, the second gaseous stream, or a combination thereof. The method may further include controlling a relative amount of the first portion of the compressed tail gas stream and the second portion of the compressed tail gas stream using a control valve. The method may further comprise passing at least a portion of the tail gas stream to a tail gas CO ₂ to CO conversion system selected from a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a plasma conversion unit, a gasification unit or a reforming unit to produce a CO-rich effluent stream and recycling a second CO-rich effluent stream to the bioreactor. The CO-enriched effluent stream may comprise H ₂:CO:CO₂ to a molar ratio of about 5:1:1 about 4.5:1:1, about 4.33:1:1, about 3:1:1, about 2:1:1, about 1:1:1, or about 1:3:1. The CO ₂ to CO conversion system may include at least one of: a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a reforming unit or a plasma conversion unit. The at least one fermentation product may be selected from ethanol, acetate, butanol, butyrate, 2, 3-butanediol, lactate, butene, butadiene, methyl ethyl ketone, ethylene, acetone, isopropanol, lipids, 3-hydroxypropionate, isoprene, fatty acids, 2-butanol, 1, 2-propanediol, hexanol, octanol, or 1-propanol. The first gaseous stream, which may include hydrogen, is generated by a hydrogen generation source that includes at least one of: a water electrolyzer, a hydrocarbon reforming source, a hydrogen purification source, a solid biomass gasification source, a solid waste gasification source, a coal gasification source, a hydrocarbon gasification source, a methane pyrolysis source, a refinery tail gas generation source, a plasma reforming reactor, a partial oxidation reactor, or any combination thereof. The second gaseous stream, which may include CO ₂, is generated by a gas generation source including at least one of: a sugar-based ethanol generation source, a first generation corn ethanol generation source, a second generation corn ethanol generation source, a sugar cane ethanol generation source, a sucrose ethanol generation source, a beet ethanol generation source, a molasses ethanol generation source wheat ethanol production source, grain-based ethanol production source, starch-based ethanol production source, cellulose-based ethanol production source, cement production source, methanol synthesis source, An olefin generating source, a steel generating source, a ferroalloy generating source, a refinery off gas generating source, a post-combustion gas generating source, a biogas generating source, a landfill generating source, an ethylene oxide generating source, a methanol generating source, an ammonia generating source, a CO ₂ generating source, a natural gas processing generating source, a gasification source, an organic waste gasification source, a direct air capture, or any combination thereof. the at least one C1-immobilized bacterium may be selected from clostridium ethanogenum, clostridium yang, or clostridium rakii.

The present disclosure relates to an integrated process for producing at least one fermentation product from a gaseous stream, the process comprising: obtaining a first gaseous stream comprising hydrogen and a second gaseous stream comprising CO ₂; passing at least a portion of the first gaseous stream and at least a portion of the second gaseous stream to a CO ₂ to CO conversion system operating under conditions that produce a CO-rich effluent stream; fermenting the CO-enriched effluent stream in a bioreactor having a culture of one or more C1 immobilized bacteria to produce at least one fermentation product stream and a bioreactor tail gas stream; Compressing the bioreactor off-gas stream to produce a compressed bioreactor off-gas stream; passing at least a first portion of the compressed bioreactor tail gas stream in any order to: i) A gas desulfurization and/or acid gas removal unit; or ii) a gas component removal unit; or iii) both a gas desulfurization and or acid gas removal unit and a gas component removal unit; to produce a compressed treated bioreactor tail gas stream; recycling the compressed treated bioreactor off-gas stream: a) To be combined with the first gaseous stream, the second gaseous stream, or a combination thereof; or b) recycled to the CO ₂ to CO conversion system combination; Or c) to be combined with the CO-enriched effluent stream; or d) any combination thereof; and optionally recycling a second portion of the compressed bioreactor tail gas stream for combination with a CO-rich effluent stream or for combination with the bioreactor. At least a second portion of the first gaseous stream, at least a second portion of the second gaseous stream, or a combination thereof may be combined with the CO-rich effluent stream. Any portion of the first gaseous stream, the second gaseous stream, or a combination thereof may be compressed. The relative amounts of the first portion of the compressed tail gas stream and the compressed tail gas stream being the second portion may be controlled using a control valve. at least a portion of the tail gas stream may be passed to a tail gas CO ₂ to CO conversion system selected from a reverse water gas shift unit, a thermal catalytic conversion unit, a partial combustion unit, a plasma conversion unit, a gasification unit, or a reforming unit to produce a CO-rich effluent stream and the second CO-rich effluent stream may be recycled to the bioreactor. The CO-enriched effluent stream may comprise H ₂:CO:CO₂ to a molar ratio of about 5:1:1 about 4.5:1:1, about 4.33:1:1, about 3:1:1, about 2:1:1, about 1:1:1, or about 1:3:1. The CO ₂ to CO conversion system may include at least one of: a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a reforming unit or a plasma conversion unit. The at least one fermentation product may be selected from ethanol, acetate, butanol, butyrate, 2, 3-butanediol, lactate, butene, butadiene, methyl ethyl ketone, ethylene, acetone, isopropanol, lipids, 3-hydroxypropionate, isoprene, fatty acids, 2-butanol, 1, 2-propanediol, hexanol, octanol, or 1-propanol. The first gaseous stream comprising hydrogen may be generated by a hydrogen generation source comprising at least one of: a water electrolyzer, a hydrocarbon reforming source, a hydrogen purification source, a solid biomass gasification source, a solid waste gasification source, a coal gasification source, a hydrocarbon gasification source, a methane pyrolysis source, a refinery tail gas generation source, a plasma reforming reactor, a partial oxidation reactor, or any combination thereof. The second gaseous stream comprising CO ₂ may be generated by a gas generation source comprising at least one of: a sugar-based ethanol generation source, a first generation corn ethanol generation source, a second generation corn ethanol generation source, a sugar cane ethanol generation source, a sucrose ethanol generation source, a beet ethanol generation source, a molasses ethanol generation source wheat ethanol production source, grain-based ethanol production source, starch-based ethanol production source, cellulose-based ethanol production source, cement production source, methanol synthesis source, An olefin generating source, a steel generating source, a ferroalloy generating source, a refinery off gas generating source, a post-combustion gas generating source, a biogas generating source, a landfill generating source, an ethylene oxide generating source, a methanol generating source, an ammonia generating source, a CO ₂ generating source, a natural gas processing generating source, a gasification source, an organic waste gasification source, a direct air capture, or any combination thereof. At least one of the C1-immobilized bacteria may be selected from clostridium ethanogenum, clostridium yang, or clostridium rakii.

The present disclosure also relates to an integrated process for producing at least one fermentation product from a gaseous stream, the process comprising: obtaining a first gaseous stream comprising hydrogen and a second gaseous stream comprising CO ₂; optionally, compressing at least a portion of the first gaseous stream, at least a portion of the second gaseous stream, or any combination thereof in a first compressor to produce a compressed first gaseous stream, a compressed second gaseous stream, and or a compressed combination of the first gaseous stream and the second gaseous stream; the following are treated in a gas treatment zone comprising a gas component removal unit, a gas desulfurization/acid gas removal unit, or both: i) At least a portion of the first gaseous stream or the compressed first gaseous stream or both; And at least a portion of the second gaseous stream or the compressed second gaseous stream or both; or ii) said compressed combination of a first gaseous stream and a second gaseous stream; to produce a processed stream; converting CO ₂ in at least a first portion of the treated stream in a CO ₂ to CO conversion system to form CO, the CO ₂ to CO conversion system operating under conditions that produce a CO-rich effluent stream; Fermenting the CO-enriched effluent stream in a bioreactor having a culture of one or more C1 immobilized bacteria to produce at least one fermentation product stream and a bioreactor tail gas stream; and recirculating the tail gas stream to the first compressor, the first gaseous stream, the second gaseous stream, or a combination of the first gaseous stream and the second gaseous stream. The CO-rich effluent stream may be combined with at least a portion of: the processed stream; or the first gaseous stream; or the second gaseous stream; or the combination of the first gaseous stream and the second gaseous stream; or the compressed first gaseous stream; or the compressed second gaseous stream; or the compressed combination of the first gaseous stream and the second gaseous stream; or any combination thereof. At least a portion of the tail gas stream may be passed to a tail gas CO ₂ to CO conversion system selected from a reverse water gas shift unit, a thermal catalytic conversion unit, a partial combustion unit, a plasma conversion unit, a gasification unit, or a reforming unit to produce a CO-rich effluent stream and recycling the second CO-rich effluent stream to the bioreactor. The CO-rich effluent stream may further comprise hydrogen and CO ₂ and may comprise H ₂:CO:CO₂ in a molar ratio of about 5:1:1, about 4.5:1:1, about 4.33:1:1, or about 3:1:1, about 2:1:1, about 1:1:1, about 1:3:1. The CO ₂ to CO conversion system may include at least one of: a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a reforming unit or a plasma conversion unit. the gas treatment zone may further comprise a deoxygenation unit, a catalytic hydrogenation unit, an adsorption unit, a thermal oxidizer, or any combination thereof. The at least one fermentation product may be selected from ethanol, acetate, butanol, butyrate, 2, 3-butanediol, lactate, butene, butadiene, methyl ethyl ketone, ethylene, acetone, isopropanol, lipids, 3-hydroxypropionate, isoprene, fatty acids, 2-butanol, 1, 2-propanediol, hexanol, octanol, or 1-propanol. The first gaseous stream comprising hydrogen may be generated by the hydrogen generation source discussed above and the second gaseous stream comprising CO ₂ may be generated by the gas generation source discussed above. at least one of the C1-immobilized bacteria may be selected from clostridium ethanogenum, clostridium yang, or clostridium rakii. The CO-rich effluent stream can include hydrogen, and the method can further include separating hydrogen from the CO-rich effluent stream and recycling the separated hydrogen to be combined with the tail gas stream or recycled to the compressor. The remainder of the CO-rich effluent stream may be compressed after hydrogen separation. The tail gas stream may include methane, and the method further includes passing a portion of the tail gas stream to a methanator to produce a methanator effluent, and combining the methanator effluent with the tail gas stream. A stream comprising oxygen may be generated from an oxygen source and passed to the methane conversion unit. A second gaseous stream comprising hydrogen may be passed from the hydrogen source to the bioreactor, a second gaseous stream comprising CO ₂ from the CO ₂ source may be passed to the bioreactor, or both. A second gaseous stream comprising hydrogen from the hydrogen source may be passed to the bioreactor or combined with the CO-rich effluent stream, a second gaseous stream comprising CO ₂ from the CO ₂ source may be passed to the bioreactor or combined with the CO-rich effluent stream, or any combination thereof. The combination of the second gaseous stream comprising hydrogen from the hydrogen source with the CO-rich effluent stream, or the combination of the second gaseous stream comprising CO ₂ from the CO ₂ source with the CO-rich effluent stream, or both, is achieved by mixing in a mixer. The ratio of the second gaseous stream comprising hydrogen from the hydrogen source to the CO-rich effluent stream entering the bioreactor may be from about greater than 0:1 to about 4:1. The CO ₂ -to-CO conversion system may include a combustion heater having a burner, and at least a portion of the tail gas stream may be recycled to at least the burner of the combustion heater. The CO ₂ to CO conversion system may include a steam generator that produces steam, or a water separation unit that produces a water stream, or both. A portion of the CO-rich effluent stream can be passed to an inoculant reactor, a buffer tank, or both, and the passing can be directly passed to the inoculant reactor, buffer tank, or both without an intervening unit.

Drawings

Fig. 1 shows a flow scheme of an embodiment wherein at least a portion of the tail gas from the bioreactor is passed through a gas component removal unit, compressed and then recycled to the bioreactor, the CO ₂ to CO conversion system, or both.

Fig. 2 shows a flow scheme in which at least a portion of the tail gas from the bioreactor is recycled to the bioreactor.

Fig. 3 shows a flow scheme of an embodiment wherein at least a portion of the tail gas from the bioreactor is compressed and passed through a gas desulfurization/acid gas removal unit and then recycled to the CO ₂ to CO conversion system.

Fig. 4 shows a flow scheme of an embodiment in which at least a portion of the tail gas from the bioreactor is compressed and passed to an optional controller to separate the tail gas stream and optionally recycle a portion to the bioreactor, and simultaneously passing the remaining portion of the tail gas to the gas treatment zone. The effluent from the gas treatment zone is recycled to the CO ₂ to the CO conversion system or to the CO ₂ to the upstream of the CO conversion system.

Fig. 5 shows a flow scheme similar to the embodiment of fig. 4, wherein an additional compressor is located upstream of the CO ₂ to CO conversion system.

FIG. 6 shows a flow scheme of an embodiment in which at least a portion of the tail gas stream is recycled to the gas treatment zone and to a compressor upstream of the CO ₂ to CO conversion system. The compressor operates on a combination of a first gaseous stream comprising hydrogen and a second gaseous stream comprising CO ₂.

Fig. 7 shows a flow scheme similar to the embodiment of fig. 6 except that the compressor operates only on the second gaseous stream comprising CO ₂, and not on the first gaseous stream comprising hydrogen. A first gaseous stream comprising hydrogen is added to the input stream, the effluent, or both, of the gas treatment zone.

Fig. 8 shows a flow scheme in which the compressor operates on only a portion of the second gaseous stream comprising CO ₂, and not on the first gaseous stream comprising hydrogen. The remaining portion of the second gaseous stream comprising CO ₂ is not compressed and may be combined with the first gaseous stream comprising hydrogen.

Fig. 9 shows a flow scheme similar to the embodiment shown in fig. 7 with the addition of separating a stream comprising hydrogen from the CO ₂ to the CO-rich effluent stream of the CO conversion system. The separated stream comprising hydrogen may be combined with the tail gas recycle.

Fig. 10 shows a flow scheme similar to the embodiment of fig. 9, with the addition of a second compressor that operates on the remainder of the CO-rich effluent stream after the stream comprising hydrogen has been separated from the CO-rich effluent stream.

Fig. 11 shows a flow scheme similar to the embodiment of fig. 6 with the addition of passing at least a portion of the bioreactor off-gas to the methane conversion unit and passing the effluent of the methane conversion unit to be recombined with the bioreactor off-gas. The oxygen source may optionally provide a stream comprising oxygen to the methane conversion unit. Optionally, a second stream comprising hydrogen from a hydrogen source may be passed directly to the bioreactor. Optionally, a second stream comprising CO ₂ from the CO ₂ source may be passed directly to the bioreactor.

Fig. 1-11 further depict an optional embodiment in which at least a portion of the input stream of CO ₂ to the CO conversion system bypasses the CO ₂ to the CO conversion system, rather than passing through the CO ₂ to the CO conversion system. The figures further illustrate optional embodiments in which at least a portion of the tail gas stream is passed through a second CO ₂ to CO conversion system and the resulting effluent is passed to a bioreactor. The figures further illustrate optional embodiments in which at least a portion of the first gaseous stream comprising H ₂ bypasses the CO ₂ to CO conversion system, rather than passing through the CO ₂ to CO conversion system.

Fig. 12 shows a flow scheme of an embodiment, wherein it is described in more detail when CO ₂ to CO conversion system is selected as the rWGS system.

Fig. 13 shows a flow scheme of an embodiment, wherein optionally a portion of the hydrogen bypasses the CO ₂ to the CO conversion system, and wherein optionally a portion of the hydrogen is obtained from a second hydrogen source.

Detailed Description

Integration of a CO ₂ -producing gas-producing process (such as an industrial process or a syngas process) with a CO ₂ -to-CO conversion process (particularly a reverse water gas shift process) provides substantial benefits in a gas fermentation process. Integration allows the use of CO ₂ as a feedstock even though the fermentation process requires some amount of CO. Integrating CO ₂ to CO conversion allows the CO ₂ in the feedstock or recycle to be converted to the proper amount of CO for fermentation.

In certain embodiments, the industrial process is selected from ferrous metal product production such as steel production, nonferrous metal product production, petroleum refining, power production, carbon black production, paper and pulp production, ammonia production, methanol production, coke production, petrochemical production, carbohydrate fermentation, cement production, aerobic digestion, anaerobic digestion, catalytic processes, natural gas extraction, cellulose fermentation, oil extraction, industrial processing of geological reservoirs, processing of fossil resources such as natural gas, coal, petroleum, or any combination thereof. Examples of specific processing steps within an industrial process include catalyst regeneration, fluid catalyst cracking, and catalyst regeneration. Air separation and direct air capture are other suitable industrial processes. Examples in the manufacture of steel and ferroalloys include the direct reduction of blast furnace gas, basic oxygen furnace gas, coke oven gas, iron furnace top gas and residual gases from iron smelting. Other general examples include flue gases from combustion boilers and combustion heaters, such as natural gas, oil, or coal-fired boilers or heaters, and gas turbine exhaust. In these embodiments, any known method may be used to capture the substrate and or C1 carbon source from the industrial process and then vent it to the atmosphere.

The substrate and or C1 carbon source may be a synthesis gas, known as syngas, which may be obtained from reforming, partial oxidation, plasma, or gasification processes. Examples of gasification processes include gasification of coal, gasification of refinery residues, gasification of petroleum coke, gasification of biomass, gasification of lignocellulosic material, gasification of waste wood, gasification of black liquor, gasification of municipal solid waste, gasification of municipal liquid waste, gasification of industrial solid waste, gasification of industrial liquid waste, gasification of refuse derived fuel, gasification of sewage sludge, gasification of sludge from wastewater treatment, gasification of landfill gas, gasification of biogas, such as when biogas is added to enhance gasification of another material. Examples of reforming processes include steam methane reforming, steam naphtha reforming, natural gas reforming, biogas reforming, landfill gas reforming, coke oven gas reforming, pyrolysis exhaust gas reforming, ethylene-producing exhaust gas reforming, naphtha reforming, and dry methane reforming. Examples of partial oxidation processes include thermal and catalytic partial oxidation processes, catalytic partial oxidation of natural gas, partial oxidation of hydrocarbons, partial oxidation of biogas, partial oxidation of landfill gas, or partial oxidation of pyrolysis exhaust gas. Examples of municipal solid waste include tires, plastics, refuse derived fuels, and fibers in, for example, shoes, clothing, textiles, and the like. Municipal solid waste may be a simple landfill type of waste and may or may not be classified. Examples of biomass may include lignocellulosic material and microbial biomass. The lignocellulosic material can comprise agricultural waste and forest waste.

When recirculation is discussed herein, the description of recirculation or passing a stream to a unit is meant to include introducing the stream directly to the unit independently, or combining the stream with another input to the unit.

The gas generation process that produces CO ₂ is an industrial process or a syngas process that produces industrial gas or syngas, typically with a significant proportion of CO ₂ by volume. Additionally, the industrial gas or syngas may include a quantity of CO and or CH ₄. The CO ₂ -producing gas generation process is intended to encompass any industrial process or syngas process that produces CO ₂ -containing gas as a desired end product, or as a by-product in the production of one or more desired end products. An exemplary CO ₂ -producing production process has sources comprising: ethanol, first generation corn ethanol, second generation corn ethanol, sugar cane ethanol, sucrose ethanol, sugar beet ethanol, molasses ethanol, wheat ethanol, grain based ethanol, starch based ethanol, cellulose based ethanol, cement, methanol synthesis, olefins, steel, ferroalloys, refinery tail gas, post-combustion gas, biogas, landfill, ethylene oxide, methanol, ammonia, mined CO ₂, natural gas processing, gasification, organic waste gasification, direct air capture, or any combination thereof is produced from a sugar based ethanol production source. Some examples of steel and ferroalloy generating sources include blast furnace gas, basic oxygen furnace gas, coke oven gas, iron furnace top gas, direct reduction of electric arc furnace off-gas, and residual gas from metallurgical iron. Other general examples include flue gases from combustion boilers and combustion heaters, such as natural gas, oil, or coal-fired boilers or heaters, and gas turbine exhaust.

FIG. 1 depicts an integrated system having a flexible production platform and a method for producing at least one fermentation product from a gaseous stream, according to one embodiment of the present disclosure. The method includes receiving a first gaseous stream comprising hydrogen and a second gaseous stream comprising CO ₂, and passing the streams to a CO ₂ to CO conversion system. In fig. 1, the CO ₂ to CO conversion system 125 is shown as a reverse water gas shift unit. The hydrogen-generating source 110 generates a first gaseous stream 120 comprising hydrogen. In one embodiment, the hydrogen generating source 110 is a water electrolyzer. The water stream 500 is introduced into a hydrogen generating source 110 which may receive power, for example 4.78kwh/Nm ³, from a power source (not shown) to convert the water into hydrogen and oxygen according to the following stoichiometric reaction:

H ₂ o+ electricity → 2h ₂+O₂ + heat

Water electrolysis techniques are known and exemplary processes include alkaline water electrolysis, proton Exchange Membrane (PEM) electrolysis, and solid oxide electrolysis. Suitable cells include alkaline cells, PEM cells, and solid oxide cells. The oxygen enriched stream 115 comprising oxygen produced as a by-product of water electrolysis may be used for various purposes. For example, at least a portion of the oxygen-enriched stream 115 may be introduced to the gas generation source 220, particularly if the gas generation source 220 is selected to comprise a synthesis gas generation process of an oxygen-blown gasifier. Such use of the oxygen-enriched stream 115 reduces the need for and associated costs of obtaining oxygen from an external source. As used herein, the term enriched refers to a description of having a higher concentration after a process step than before a process step.

In particular embodiments, the hydrogen generating source 110 may be selected from hydrocarbon reforming, hydrogen purification, solid biomass gasification, solid waste gasification, coal gasification, hydrocarbon gasification, methane pyrolysis, refinery tail gas generation processes, plasma reforming reactors, partial oxidation reactors, or any combination thereof.

The gas generating source 220 generates the second gaseous stream 140 comprising CO ₂ from a direct air capture, an industrial process that generates CO ₂, a syngas process, or any combination thereof. The first gaseous stream 120 comprising hydrogen and the second gaseous stream 140 comprising CO ₂ are passed to the CO ₂ to the CO conversion system 125, either alone or in combination, to produce a CO-rich effluent stream 130. The combined gas composition of the first gaseous stream 120 comprising hydrogen and the second gaseous stream 140 comprising CO ₂ comprises a molar ratio of H ₂:CO₂ of about 3:1 in one embodiment, about 2.5:1 in another embodiment, and about 3.5:1 in yet another embodiment, and the molar ratio of H ₂ to CO may be greater than about 5:1. The CO ₂ to CO conversion system 125 may be at least one selected from a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a reforming unit, or a plasma conversion unit.

In a particular embodiment, the CO ₂ to CO conversion system 125 is a reverse water gas shift unit. Reverse water gas shift (rWGS) technology is known and is used to produce carbon monoxide from carbon dioxide and hydrogen, with water being a by-product. The temperature of the rWGS process is the main driving factor for the shift. The reverse water gas shift unit may comprise a single stage reaction system or two or more reaction stages. The different stages may be carried out at different temperatures and different catalysts may be used.

In another embodiment, the CO ₂ to CO conversion system 125 involves thermocatalytic conversion that involves breaking stable atomic and molecular bonds of CO ₂ and other reactants on the catalyst by using thermal energy as the driving force for the CO-producing reaction. Since the CO ₂ molecule is thermodynamically and chemically stable, a large amount of energy is required if CO ₂ is used as a single reactant. Therefore, other substances such as hydrogen are often used as co-reactants to make the thermodynamic process easier. Many catalysts are known for this process, such as metals and metal oxides and nano-sized catalyst metal organic frameworks. Various carbon materials have been used as carriers for catalysts.

In another embodiment, the CO ₂ -to-CO conversion system 125 includes partial combustion, wherein oxygen provides at least a portion of the oxidant required for partial oxidation, and the reactants carbon dioxide and water are substantially converted to carbon monoxide and hydrogen.

In yet another embodiment, the CO ₂ to CO conversion system 125 involves plasma conversion, which is a combination of plasma and catalyst, also referred to as plasma catalysis. A plasma is an ionized gas consisting of electrons, various types of ions, radicals, excited atoms and molecules, and neutral ground state molecules. The three most common plasma types for CO ₂ to CO conversion include Dielectric Barrier Discharge (DBD), microwave (MW) plasma, and sliding arc (GA) plasma. Advantages of selecting plasma conversion for CO ₂ to CO conversion include (i) high process versatility, allowing different kinds of reactions to be performed, such as pure CO ₂ cracking, and CO ₂ conversion in the presence of a hydrogen source (e.g., CH ₄、H₂ or H ₂ O); (ii) low investment and operating costs; (iii) no requirement for rare earth metals; (iv) A convenient modular arrangement, as the plasma reactor increases linearly with plant throughput; and (v) it can be very easily combined with various renewable power.

The figure depicts the case where the CO ₂ to CO conversion system 125 is selected to contain at least one rWGS unit. The rWGS reaction is a reversible hydrogenation of CO ₂ to produce CO and H ₂ O. Due to its chemical stability, CO ₂ is a relatively non-reactive molecule and thus the reaction to convert it to more reactive CO is energy intensive.

Because the rWGS reaction is endothermic, it is thermodynamically favored at higher temperatures. Generally, a temperature of about 500 ℃ is ideal for producing significant amounts of CO. In embodiments employing higher temperatures, iron-based catalysts are generally considered one of the most successful active metals for higher temperatures due to their thermal stability and high oxygen mobility. In embodiments employing lower temperatures, copper is generally considered successful because it enhances adsorption of the reaction intermediates. In some other embodiments, the rWGS catalyst selection comprises Fe/Al₂O₃、Fe-Cu/Al₂O₃、Fe-Cs/Al₂O₃、Fe-Cu-Cs/Al₂O₃ or a combination thereof.

The CO ₂ to CO conversion system 125 employing, for example, rWGS technology, produces a CO-rich effluent stream 130. In some embodiments, the H ₂ to CO molar ratio of the CO-enriched effluent stream 130 can be greater than about 3:1. The molar ratio of H ₂:CO:CO₂ of the CO-enriched effluent stream 130 may be about 5:1:1 based on the stoichiometry of ethanol as product and the molar ratio of CO ₂ to CO being 1:1.

In some examples, the rWGS reaction operates at a level such that the H ₂ to CO molar ratio in the CO-enriched effluent stream 130 is less than or equal to a predetermined ratio, such as about 3:1. Such CO levels may exceed the CO levels required for gas fermentation. Higher than desired CO conversion from CO ₂ to CO conversion system 125 may result in suboptimal performance. Thus, the size of the CO ₂ to CO conversion system 125 will be designed to be larger than necessary. Such large systems are expensive. Thus, to avoid such large systems, at least a portion of the first gaseous stream comprising hydrogen is directed to bypass 520 and does not pass into CO ₂ to CO conversion system 125. The bypass stream 520 is combined with the CO-rich effluent stream 130. Thus, the H ₂ to CO ratio in line 130 delivered for fermentation can be adjusted to be greater than a predetermined ratio by optimizing the size of CO ₂ to the CO conversion system 125. Similarly, a portion of the second gaseous stream 140 including CO ₂ may be diverted to bypass CO ₂ to CO conversion system 125 using second bypass stream 525. In this way, the amount of CO produced can be controlled without over-designing the capacity of the CO ₂ to the CO conversion system 125.

If ethanol is not the intended fermentation product, the stoichiometry will be different as discussed above. For example, if 2, 3-butanediol (2, 3-BDO) is the desired fermentation product, the H ₂:CO:CO₂ molar ratio of the CO-rich effluent stream 130 can be about 4.5:1:1 based on the stoichiometry of 2,3-BDO and the CO ₂:co molar ratio is 1:1.

9H₂+2CO+2CO₂→C₄H₁₀O₂+4H₂O

If acetone is the desired fermentation product, the H ₂:CO:CO₂ molar ratio of the CO-enriched effluent stream 130 may be about 4.33:1:1 and the CO ₂:CO molar ratio is 1:1, based on the stoichiometry of the acetone.

6.5H₂+1.5CO+1.5CO₂→C₃H₆O+3.5H₂O

If acetate is the desired fermentation product, the H ₂:CO:CO₂ molar ratio of the CO-enriched effluent stream 130 may be about 3:1:1 and the CO ₂:CO molar ratio is 1:1, based on the stoichiometry of acetate.

3H₂+1CO+1CO₂→C₂H₄O₂+1H₂O

If isopropanol is the desired fermentation product, the H ₂:CO:CO₂ molar ratio of the CO-enriched effluent stream 130 may be about 5:1:1 and the CO ₂:CO molar ratio 1:1, based on the stoichiometry of the isopropanol.

H₂+1.5CO+1.5CO₂→C₃H₈O+3.5H₂O

The CO-rich effluent stream 130 is passed to a bioreactor 142 comprising a culture of one or more C1 immobilized bacteria. Bioreactor 142 may be a fermentation system comprised of one or more vessels and or columns or piping arrangements. Examples of bioreactors include Continuous Stirred Tank Reactors (CSTR), immobilized Cell Reactors (ICR), trickle Bed Reactors (TBR), bubble columns, gas lift fermenters, static mixers, circulating loop reactors, membrane reactors such as hollow fiber membrane bioreactors (HFM-BR), or other devices suitable for gas-liquid contacting. Bioreactor 142 may comprise a plurality of reactors or stages in parallel or in series. Bioreactor 142 may be a production reactor in which a majority of the fermentation product is produced.

Bioreactor 142 includes a culture of one or more C1-immobilized microorganisms having the ability to produce one or more products from a C1 carbon source. "C1" refers to a single carbon molecule, e.g., CO or CO ₂. "C1 carbon source" refers to a single carbon molecule that serves as part of or the sole carbon source for a microorganism. For example, the C1 carbon source may include one or more of CO, CO ₂, or CH ₂O₂. In some embodiments, the C1 carbon source may include one or both of CO and CO ₂. Typically, the C1-immobilized microorganism is a C1-immobilized bacterium. In an example, the microorganism is derived from a C1-immobilized microorganism identified in table 1. Microorganisms may be classified based on functional characteristics. For example, the microorganism may be derived from a C1-immobilized microorganism, an anaerobic bacterium, an acetogenic bacterium (acetogen), an ethanologenic bacterium (ethanologen), and or a carboxydotrophic bacterium (carboxydotroph). Table 1 provides a representative list of microorganisms and identifies their functional properties.

"Anaerobic bacteria" are microorganisms that grow without the need for oxygen. Anaerobic bacteria may produce adverse reactions or even die if oxygen is present above a certain threshold. Typically, the microorganism is an anaerobic bacterium. In a preferred embodiment, the microorganism is or is derived from an anaerobic bacterium identified in table 1.

An "acetogenic bacteria" is a microorganism that produces or is capable of producing acetate or acetic acid as a product of anaerobic respiration. Generally, acetogens are obligate anaerobes that use the Wood-Ljungdahl pathway as their primary mechanism for energy conservation and synthesis of acetyl-CoA and acetyl-CoA derived products (e.g., acetate) (Ragsdale, biochemical and biophysical report (Biochim Biophys Acta), 1784:1873-1898,2008). Acetogenic bacteria use The acetyl-CoA pathway in cellular carbon synthesis as (1) a mechanism for The reductive synthesis of acetyl-CoA from CO ₂, (2) a terminal electron accepting and energy conserving process, (3) a mechanism for CO ₂ immobilization (i.e., assimilation) (Drake, "prokaryote (Acetogenic Prokaryotes)", see: (The Prokaryotes), 3 rd edition, page 354, new York, N.Y., 2006). All naturally occurring acetogens are C1-fixed, anaerobic, autotrophic and non-methane oxidising. In one embodiment, the microorganisms in bioreactor 142 are acetogens. In other embodiments, the microorganism is derived from acetogenic bacteria identified in table 1.

The microorganism may be a member of the genus clostridium (genus Clostridium). In one embodiment, the microorganism is obtained from a clostridium cluster comprising the species clostridium ethanogenum, clostridium yangenum, and clostridium rakii. These species were originally reported and characterized by: abrini, microbiology literature set (Arch Microbiol), 161:345-351,1994 (clostridium ethanogenum); tanner, journal of International System bacteriology (Int J System Bacteriol), 43:232-236,1993 (Clostridium Yankee); and Huhnke, WO 2008/028055 (Clostridium radicum). The microorganism may also be derived from an isolate or mutant of clostridium ethanogenum, clostridium yang or clostridium lansium. Isolates and mutants of Clostridium ethanologenic bacteria comprise JA1-1 (DSM 10061) (Abrini, microbiology literature set 161:345-351,1994), LBS1560 (DSM 19630) (WO 2009/064200) and LZ1561 (DSM 23693). Isolates and mutants of Clostridium Yankeei include ATCC 49587 (Tanner, J.International System bacteriology, 43:232-236,1993), PETCT (DSM 13528, ATCC 55383), ERI-2 (ATCC 55380) (U.S. Pat. No. 5,593,886), C-01 (ATCC 55988) (U.S. Pat. No. 6,368,819), 0-52 (ATCC 55989) (U.S. Pat. No. 6,368,819) and OTA-1 (Tirado-Acevedo, bioethanol production from syngas using Clostridium Yankeei (Production of bioethanol from SYNTHESIS GAS using Clostridium ljungdahlii), doctor's paper, north Carolina state university (North Carolina State University), 2010). Isolates and mutants of Clostridium lanuginosum contained PI 1 (ATCC BAA-622, ATCC PTA-7826) (WO 2008/028055).

The microorganisms of the present disclosure may be cultured to produce one or more products. For example, clostridium ethanologens produce or can be engineered to produce ethanol (WO 2007/117157), acetate (WO 2007/117157), butanol (WO 2008/115080 and WO 2012/053905), butyrate (WO 2008/115080), 2, 3-butanediol (WO 2009/151342), lactate (WO 2011/112103), butene (WO 2012/024522), butadiene (WO 2012/024522), methyl ethyl ketone (2-butanone) (WO 2012/024522 and WO 2013/185123), ethylene (WO 2012/026833), acetone (WO 2012/115527), isopropanol (WO 2012/115527), lipids (WO 2013/036147), 3-hydroxypropionates (3-HP) (WO 2013/180581), isoprene (WO 2013/180584), fatty acids (WO 2013/191567), 2-butanol (WO 2013/185123), 1, 2-propanediol (WO 2014/0369152) and 1-propanol (WO 2014/0369152). In addition to one or more target products, the microorganisms of the present disclosure may produce ethanol, acetate, and/or 2, 3-butanediol. In certain embodiments, the microbial biomass itself may be considered a product.

The culture is typically maintained in an aqueous medium containing sufficient nutrients, vitamins and or minerals to allow the growth of the microorganism. The aqueous medium may be an anaerobic microorganism growth medium, such as a minimal anaerobic microorganism growth medium. Suitable media are well known in the art.

The culturing and/or fermentation may be carried out under suitable conditions to produce the desired product. The cultivation/fermentation is usually carried out under anaerobic conditions. The reaction conditions to be considered include pressure (or partial pressure), temperature, gas flow rate, liquid flow rate, medium pH, medium redox potential, agitation rate (if a continuously stirred tank reactor is used), inoculum level, maximum gas matrix concentration to ensure that the gas in the liquid phase does not become limiting, and maximum product concentration to avoid product inhibition. In particular, the rate of introduction of the matrix may be controlled to ensure that the concentration of gas in the liquid phase does not become limiting, as under gas limiting conditions the product may be consumed by the culture.

Operating the bioreactor at elevated pressure allows for an increased rate of gas mass transfer from the gas phase to the liquid phase. Therefore, it is generally preferable to perform the cultivation/fermentation at a pressure higher than the atmospheric pressure. Furthermore, since the given gas conversion is in part a function of the matrix retention time, the conversion determines the volume required for the bioreactor. The use of a pressurized system can greatly reduce the volume of the bioreactor required and thus reduce the capital cost of the cultivation/fermentation equipment. Thus, when the bioreactor is maintained at high pressure rather than atmospheric pressure, the retention time, defined as the volume of liquid in the bioreactor divided by the input gas flow rate, can be reduced. The optimal reaction conditions will depend in part on the particular microorganism used. In general, however, it is preferred to perform the fermentation at a pressure above atmospheric pressure.

The desired product may be separated from the fermentation broth using any method or combination of methods known in the art, including, for example, fractional distillation, evaporation, pervaporation, gas stripping, phase separation, extraction separation (including, for example, liquid-liquid extraction). In certain embodiments, the target product is recovered from the fermentation broth by continuously removing a portion of the broth from the bioreactor, first separating the microbial cells from the broth, and then separating the target product from the aqueous residue. The alcohol and/or acetone may be recovered, for example, by distillation. The acid may be recovered, for example, by adsorption to activated carbon. The separated microbial biomass may be recycled to the bioreactor. The solution remaining after removal of the target product may also be recycled to the bioreactor. Additional nutrients may be added to the recycled solution to replenish the medium, which is then returned to the bioreactor.

The CO-rich effluent stream 130 is introduced to a bioreactor 142 and fermented to produce an off-gas stream 160 and a fermentation product stream 150, which may include any of the above-described products. The term off-gas refers to gases and vapors that are typically released from the industrial process to the atmosphere after all reactors and treatments are completed. The tail gas stream 160 is ultimately recycled in combination with the second gaseous stream 140 comprising CO ₂ for introduction to the CO ₂ to the CO conversion system 125. The tail gas stream 160 may contain an amount of CO ₂ generated during the fermentation process, for example, by the following reaction:

6CO+3H ₂O→C₂H₅OH+4CO₂ (ΔG= -224.90kJ/mol ethanol)

Recycling the CO ₂ present in the tail gas stream 160 from the bioreactor 142 to the CO ₂ to the CO conversion system 125 increases the carbon capture efficiency of the overall process. The CO-lean tail gas stream 160 may comprise less than about 5 mole% CO. In some embodiments, the molar ratio of H ₂:CO₂ of the tail gas stream 160 is equal to or less than about 3:1.

The tail gas stream 160 may contain various components that are preferably removed prior to further processing. In these examples, the tail gas stream 160 is treated to remove one or more components and produce a sweetened and or acid gas treated tail gas stream 340, which may be combined with the second gaseous stream 140 comprising CO ₂. One or more components that may be removed from the tail gas stream 160 may include sulfur-containing compounds including, but not limited to, hydrogen sulfide (H ₂ S), carbon disulfide, and or sulfur dioxide, aromatic compounds, alkynes, olefins, alkanes, alkenes (olefin), nitrogen compounds, phosphorous compounds, particulates, solids, oxygen, oxygenates, halogenated compounds, silicon-containing compounds, carbonyls, metals, alcohols, esters, ketones, peroxides, aldehydes, ethers, tars, methyl mercaptan, ammonia, diethylamine, triethylammonium, acetic acid, methanol, ethanol, propanol, butanol, and higher alcohols, naphthalene, or combinations thereof. These components may be removed by conventional removal modules known in the art, such as hydrolysis modules, acid gas removal modules, deoxygenation modules, catalytic hydrogenation modules, particulate removal modules, chloride removal modules, tar removal modules, and/or hydrogen cyanide removal modules, and combinations thereof. In certain examples, at least one component removed from the tail gas stream comprises sulfur-containing compounds, such as hydrogen sulfide, that may be produced, introduced, and or concentrated by a fermentation process. The hydrogen sulfide may be a catalyst inhibitor in the CO ₂ -to-CO system 125 using rWGS technology and catalysts.

The tail gas stream 160 passes through a gas component removal unit 170. The gas component removal unit 170 removes components other than sulfur-containing compounds or acid gas components. In some embodiments, the component removed is water. Since the water gas shift reaction produces water, it is advantageous to limit the amount of water fed to the water gas shift reactor. Removal of water may achieve better water balance throughout the process. In some embodiments, the component removed is a hydrocarbon. The gas component removal unit 170 may include a plurality of sub-modules in order to remove various components other than the sulfur-containing compound. In some embodiments, a liquid scrubber is used to remove ethanol containing other soluble components and higher alcohols. In these embodiments, the gas component removal unit 170 may be operable to capture and recover fermentation products contained in the tail gas stream 160. Volatile organic compounds may also be removed in the gas component removal unit 170. Other components that may be removed in the gas component removal unit 170 include, for example, mono-nitrogen species such as Hydrogen Cyanide (HCN), ammonia (NH ₃), nitrogen oxides (NO _x), and other known enzyme inhibiting gases such as acetylene (C ₂H₂), ethylene (C ₂H₄), ethane (C ₂H₆), BTEX (benzene, toluene, ethylbenzene, xylenes), and or oxygen (O ₂).

The resulting treated tail gas stream 185 is passed to a first compressor 190 to produce a compressed treated gas stream 200 that is passed to a gas desulfurization/acid gas removal unit 180. In some embodiments, a compressor 190 may be positioned upstream of the gas component removal unit 170 between the bioreactor 142 and the gas component removal unit 170 to compress the tail gas stream 160 prior to passing into the gas component removal unit 170. Typically, compressor 190 is operated at a pressure of about 3 bar to about 10 bar. The compressed treated tail gas stream 200 is passed to a gas desulfurization/acid gas removal unit 180 to produce a desulfurized and/or acid gas treated tail gas stream 340. A gas desulfurization/acid gas removal unit 180. Sulfur-containing compounds and or acid gases are removed as inhibitors in the CO ₂ -to-CO conversion system 125 using the rWGS technology by poisoning the rWGS catalyst. Many commercial desulfurization techniques are not effective in removing sulfur in the form of COS, but are better able to handle sulfur in the form of hydrogen sulfide. In one embodiment, gas desulfurization/acid gas removal unit 180 operates to convert a compound, such as carbonyl sulfide COS, to hydrogen sulfide H ₂ S by hydrolysis according to the following reaction:

Hydrolysis may be performed by a metal oxide catalyst or an alumina catalyst to convert COS to H ₂ S. In some embodiments, two or more desulfurization operations, such as sponge iron, followed by a metal oxide catalyst, may be employed. In certain other embodiments, the gas desulfurization/acid gas removal unit 180 can employ a zinc oxide (ZnO) catalyst to remove hydrogen sulfide. In other embodiments, pressure Swing Adsorption (PSA) is utilized to remove the sour gas by adsorption through a suitable adsorbent in a fixed bed contained in a vessel at high pressure. In yet other embodiments, caustic scrubbing is used for gas desulfurization. The caustic scrubbing may comprise passing the compressed treated tail gas stream 200 through a caustic solution (e.g., naOH) to remove sulfur-containing compounds. The removal of hydrogen sulfide by alkaline washing can be expressed as follows:

h ₂ S (gas) +NaOH (water-based) →NaHS (water-based) +H ₂ O

NaHS (aqueous) +NaOH (aqueous) +Na ₂ S (aqueous) +H ₂ O

The sweetened and/or acid gas treated tail gas stream 340 exiting the gas desulfurization/acid gas removal unit 180 may be combined with the second gaseous stream 140 comprising CO ₂ and recycled to the CO ₂ to CO conversion system 125. Alternatively, instead of the sweetened and or acid gas treated tail gas stream 340 being passed to combine with the second gaseous stream 140 comprising CO ₂, the alternative sweetened and or acid gas treated tail gas stream 345 is combined with the first gaseous stream 120 comprising hydrogen.

A portion of the compressed treated tail gas stream 200 may be combined with the CO-rich effluent stream 130 and passed to the bioreactor 142 instead of the gas desulfurization/acid gas removal unit 180. Such recycling is beneficial for the growth of microorganisms because the microorganisms consume sulfur to produce amino acids such as methionine and cysteine. Thus, the sulfur feed requirements to bioreactor 142 are reduced as sulfur is recycled as part of compressed treated tail gas stream 200.

In an optional embodiment where the gas generation source 220 involves biogas generation, a portion of the second gaseous stream 140 comprising CO ₂ is passed to an optional biogas reformer 230. Biogas refers to gases produced by anaerobic digestion of organic matter, such as manure, sewage sludge, municipal solid waste, biodegradable waste, or any other biodegradable feedstock. Biogas is composed mainly of methane and carbon dioxide. Typically, in a biogas reformer, CO ₂ and steam reforming of methane are performed to produce a synthesis gas stream.

With respect to fig. 1, a biogas reformer effluent stream 240 comprising CO and H ₂ produced in a biogas reformer 230 is combined with the CO-rich effluent stream 130 and can be operated to increase the H ₂: CO ratio of many fermentation processes.

In one embodiment, at least a portion of the tail gas stream 160 is passed through an optional second CO ₂ to a CO conversion system 510, which may be a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a plasma conversion unit, a gasification unit, or a reforming unit. The tail gas stream 160 is lean in CO, but may have residual H ₂ and CO ₂. Recycling at least a portion of the tail gas stream 160 through the optional second CO ₂ to the CO conversion system 510 and the second CO ₂ to the CO conversion system effluent 512 to the bioreactor 142 may reduce the H ₂ to CO ratio in the bioreactor 142. Such a reduction in the H ₂ to CO ratio in bioreactor 142 may facilitate product selectivity and increased or faster microbial growth. Note that the second CO ₂ to CO conversion system effluent 512 may be recycled to be combined with stream 130 rather than being separately passed to bioreactor 142 (not shown).

In one embodiment, an optional additional stream 430 comprising hydrogen generated from the hydrogen generating source 110 is passed to the bioreactor 142 or the CO-rich effluent stream 130, thereby bypassing the CO ₂ to the CO conversion system 125. An additional stream 430 comprising hydrogen may be passed without an intervening processing unit. Microbial fermentation of CO in the presence of H ₂ can result in substantially complete carbon transfer into a product, such as an alcohol, but in the absence of sufficient H ₂, only a portion of the available CO is converted to product, while another portion is converted to CO ₂, as shown in the following equation: 6CO+3H ₂O→C₂H₅OH+4CO₂. Thus, in some embodiments, it may be beneficial to provide sufficient hydrogen to bioreactor 142. The use of a bypass to pass additional hydrogen-comprising stream 430 to bioreactor 142 or to CO-enriched effluent stream 130 allows for control of the amount of hydrogen directed to the unit at different times during the overall process run without going through CO ₂ to CO conversion system 125. For example, during start-up, less hydrogen may be required in the bioreactor, including any inoculators, thereby benefiting from a CO-rich feed at start-up. However, near the end of the run, less CO may be required in the bioreactor and a greater relative amount of H ₂ may be employed. This may be particularly beneficial in the conditioning or seeding stage (where the main bioreactor receives less CO than the seeding bioreactor) or when a buffer tank is employed. The bypass enables control of changing the H ₂: CO ratio of the feed to the CO ₂ to the CO conversion system 125, to the bioreactor 142, or both. The bypass also allows control to change H ₂: C (hydrogen: carbon) to CO ₂ to CO conversion system 125, bioreactor 142, or both.

The product selectivity of those products having increased productivity in gaseous environments having higher proportions of CO may be beneficial by providing a CO-rich environment in bioreactor 142 using CO ₂ to CO conversion system 125 and recycling CO ₂ from bioreactor 142 to CO ₂ to CO conversion system 125. One such example is the production of ethanol. Another benefit is that microbial growth of specific microorganisms having the Wood-Long Daer pathway (Wood-Ljungdahl pathway) may be increased because biological water gas shift in the Wood-Long Daer pathway is improved when these microorganisms consume higher concentrations of CO.

FIG. 2 illustrates an integrated system for producing at least one fermentation product from a gaseous stream according to another embodiment of the present disclosure. The hydrogen generating source 110 produces a first gaseous stream 120 comprising hydrogen and the gas generating source 220, which may be a direct air capture or CO ₂ producing industrial process, produces a second gaseous stream 140 comprising CO ₂. The first gaseous stream 120 comprising hydrogen and the second gaseous stream 140 comprising CO ₂ are combined to form a combined feed stream 250 and passed to CO ₂ to CO conversion system 125. The gas composition in the combined feed stream 250 comprises a molar ratio of H ₂:CO₂ to 1 in one embodiment, about 2.5 to 1 in another embodiment, about 3.5 to 1 in yet another embodiment, and greater than about 5 to 1 in yet another embodiment.

In one embodiment, the CO ₂ to CO conversion system 125 employs rWGS technology. In the CO ₂ to CO conversion system 125, CO ₂ is reacted to produce a CO-rich effluent stream 130. The moles of components in the stream are as discussed in fig. 1. As shown in fig. 2, in an embodiment, at least a portion of the feed stream 250 is optionally diverted in a bypass stream 520 around CO ₂ to the CO conversion system 125. The bypass stream 520 is combined with the CO-rich effluent stream 130. The benefits of bypass flow 520 are described in fig. 1. The CO-rich effluent stream 130 is passed to a bioreactor 142 having one or more C1 immobilized microorganism-site cultures. The culture is fermented to produce one or more fermentation products 150 and an off-gas stream 160. The CO-depleted tail gas stream 160 may comprise less than about 5mol% CO. In some embodiments, the molar ratio of H ₂:CO₂ of the tail gas stream 160 is less than or equal to about 3:1.

The tail gas stream 160 is passed to a first compressor 190 to produce a compressed tail gas stream 202. The compressed tail gas stream 202 is recycled to be combined with the CO-rich effluent stream 130. Optionally, a small first purge stream 204 of the tail gas stream 160 or a small second purge stream 206 of the compressed tail gas stream 202 may be removed to control the accumulation of nitrogen, methane, argon, helium, or other inert components.

As shown in fig. 1, in one embodiment, at least a portion of the tail gas stream 160 is passed through an optional second CO ₂ to CO conversion system 510 and a second CO ₂ to CO conversion system effluent 512 is recycled to the bioreactor 142 or the CO-rich effluent stream. Further, as shown in fig. 1, the second CO ₂ to CO conversion system effluent 512 may be recycled to be combined with stream 130 rather than separately passed to bioreactor 142 (not shown).

FIG. 3 illustrates another embodiment similar to FIG. 2, except that the compressed tail gas stream 202 is passed to a gas desulfurization/acid gas removal unit 180, and the resulting desulfurized and/or acid gas treated tail gas stream 340 is passed to the CO ₂ to the CO conversion system 125. The gas compositions in the combined feed stream 250, CO-rich effluent stream 130, and tail gas stream 160 are as described in fig. 1 and 2. An optional bypass related embodiment is depicted in fig. 2.

Fig. 4 shows another embodiment similar to fig. 2 and 3. The tail gas stream 160 is passed to a first compressor 190 and the resulting compressed tail gas stream 202 is passed to an optional control valve 550. An optional control valve 550 is used to control the relative portion of the compressed tail gas stream 202 that is directed to the gas treatment zone 182 or combined with the CO-rich effluent stream 130. The gas treatment zone 182 is shown as containing a gas component removal unit 170 and a gas desulfurization/acid gas removal unit 180. However, both units may not be required in all embodiments, and the gas treatment zone 182 may contain only one of the gas component removal unit 170 or the gas desulfurization/acid gas removal unit 180. Furthermore, the units in the gas treatment zone 182 may be in any order. The treated tail gas stream 185 produced from the gas treatment zone 182 is added to the combined feed stream 250 and passed to the CO ₂ to the CO conversion system 125. An optional control valve 550 can be adjusted to distribute the compressed tail gas stream 202 in different proportions based on the fermentation stage that occurs at the time. For example, during the start-up fermentation phase, the increased CO demand in the bioreactor 142 can be met by adjusting the control valve 550 such that more of the compressed tail gas stream 202 is combined with the CO-rich effluent stream 130 than with the gas treatment zone 182. On the other hand, when fermentation in bioreactor 142 transitions to a steady stage, the reduced CO demand of bioreactor 142 can be met by adjusting control valve 550 to flow less of compressed tail gas stream 202 than to gas treatment zone 182 to combine with CO-rich effluent stream 130. In other examples, if H ₂ utilization during fermentation is low, e.g., below 70%, the control valve 550 can be adjusted to flow more of the compressed tail gas stream 202 to combine with the CO-rich effluent stream 130 than to the gas treatment zone 182. As shown, the control valve 550 is used to achieve dynamic control of the ratio of H ₂ to CO provided to the bioreactor 142 based on CO and or H ₂ requirements during the fermentation process.

The gas composition is as described with respect to fig. 2 and 3, and an optional bypass embodiment is described with respect to fig. 2.

Fig. 5 is similar to fig. 4 with the addition of a second compressor 192. The combined feed stream 250 is passed to a second compressor 192 to produce a compressed combined feed stream 260. The gas composition of the combined feed stream 260 is as discussed above. The compressed combined feed stream 260 is combined with the treated tail gas stream 185 and passed to the CO ₂ to the CO conversion system 125 to produce the CO-rich effluent stream 130. The gas composition of the CO-rich effluent stream 120 and the tail gas stream 160 is as described above. Optional control valve 550 and bypass embodiments are discussed above.

Fig. 6 illustrates an embodiment wherein both the combined feed stream 250 and the tail gas stream 160 are passed to a first compressor 190. The first compressor 192 provides a compressed stream 270 that is passed to the gas treatment zone 182. The gas treatment zone is as described above. It should be appreciated that some gas treatment modules may be added or removed to the gas treatment zone 182 based on the actual gas composition. For example, in some embodiments, the compressed stream 270 may comprise acetylene (C ₂H₂), which may act as a microbial inhibitor in fermentation. To remove acetylene, a catalytic hydrogenation module may be included in the gas treatment zone 182. Catalytic hydrogenation involves the addition of hydrogen in the presence of hydrogenation catalysts such as those comprising nickel, palladium, platinum. The choice of hydrogenation catalyst depends on the specific gas composition and operating conditions of the system. In a particular embodiment, palladium on alumina (Pd/Al ₂O₃) is used as a catalyst. An example of such a catalyst is BASF ^TM R0-20/47. In other embodiments, the gas composition of the compressed stream 270 may comprise benzene, ethylbenzene, toluene, and xylenes (BETX) that may inhibit fermentation. Accordingly, BETX removal modules may be added to the gassing zone 182. An exemplary BETX removal module may involve the adsorption of BETX components using one or more activated carbon beds. Another exemplary BTEX removal module involves exhaust gas incineration, a thermal oxidation process in which BTEX components are burned at temperatures in excess of about 650 ℃. The treated stream 290 is passed to a CO ₂ to a CO conversion system 125. The gas composition of the various streams is presented above. The bypass embodiment is described above.

Fig. 7 is similar to fig. 6 except that the first gaseous stream 120 comprising hydrogen may have been pressurized by the hydrogen source 110 and thus does not require passage into the first compressor 190. The first gaseous stream 120 comprising hydrogen may be combined with the second gaseous stream 140 comprising CO ₂ before, after, or both before and after the gas treatment zone 182 without passing through the first compressor 190. The gas composition in the gas stream 290, prior to introduction to the CO ₂ to CO conversion system 125, includes in one embodiment an H ₂:CO₂ molar ratio of about 3:1, in another embodiment about 2.5:1, in yet another embodiment about 3.5:1, and in yet another embodiment greater than about 5:1. The gas composition in the CO-rich effluent stream 130 and the tail gas stream 160 is as described above.

Fig. 7 also illustrates an embodiment in which the first gaseous stream 120 comprising hydrogen is optional regardless of the pressure provided by the hydrogen source 110, and may not be employed, but rather a stream 430 comprising hydrogen produced by the hydrogen generating source 110 that does not pass through the CO ₂ to the CO conversion system 125. Additional stream 430 comprising hydrogen may be passed to bioreactor 142 or combined with CO-rich effluent stream 130. If desired, the stream 430 including hydrogen gas generated from the hydrogen-generating source 110 may be compressed to a target pressure. Maintaining the supply of CO ₂ separate from the supply of H ₂ allows for increased control of the amount of hydrogen directed to bioreactor 142 at different times during the overall process run. For example, during start-up, less hydrogen may be required in the bioreactor, including any inoculators, thereby benefiting from a CO-rich feed at start-up. However, near the end of the run, less CO may be required in the bioreactor and a greater relative amount of H ₂ may be employed. This may be particularly beneficial in the conditioning or seeding stage (where the main bioreactor receives less CO than the seeding bioreactor) or when a buffer tank is employed. The bypass enables control of changing the H ₂: CO ratio of the feed to the CO ₂ to the CO conversion system 125, to the bioreactor 142, or both. One target H ₂:CO:CO₂ ratio for the bioreactor may be 1:3:1.

In fig. 8, a portion of the second gaseous stream 140 comprising CO ₂ is passed to the first compressor 190, while another portion of the second gaseous stream 140 comprising CO ₂ is combined with the first gaseous stream 120 comprising hydrogen and passed to the gas treatment zone 182, thereby bypassing the first compressor 190. Some gas generating sources 220 may provide oxygen as a component of the second gaseous stream 140 that includes CO ₂. However, for some microorganisms, oxygen may be a microbial inhibitor, and the oxygen content in the second gaseous stream 140 comprising CO ₂ may need to be reduced to an acceptable level. In these cases, the gas treatment zone 182 may further include a deoxygenation module. The deoxygenation module may employ a catalytic process in which oxygen is reduced to CO ₂ or water. In certain embodiments, the catalyst used in the deoxygenation module comprises copper. Examples of such catalysts are BASF PURISTAR ^TM R3.15 or BASF CU 0226S. The deoxygenation process is exothermic and the heat generated can be used throughout the process, such as preheating the gas prior to the endothermic reaction in the CO ₂ to CO conversion system 125 involving the rWGS technology. The gas composition of the various streams is described above. Bypass embodiments are described above.

Fig. 9 shows an embodiment in which the CO-rich effluent stream 130 from the CO ₂ to the CO conversion system 125 passes through a hydrogen separation unit 330 before passing to the bioreactor 142. The hydrogen separation unit 330 may involve a membrane separation technique or a pressure swing adsorption technique. Separating hydrogen from the CO-rich effluent stream 130 increases the amount of CO in the H ₂ to CO ratio of the hydrogen separation unit effluent 350 that is passed to the bioreactor 142. The separated hydrogen stream 344 produced in the hydrogen separation unit 330 is recycled to the first compressor 190 alone (not shown) or combined with the tail gas stream 160 that is also recycled to the first compressor 190. Fig. 9 illustrates an embodiment in which the first gaseous stream 120 comprising hydrogen is already at a sufficient pressure and thus bypasses the first compressor 190 to combine with the compressed stream 270 prior to the gassing zone 182. If the first gaseous stream 120 comprising hydrogen is not already under pressure, at least a portion of the first gaseous stream 120 comprising hydrogen may pass through the first compressor 190. The gas composition of the treated stream 290, prior to introduction to the CO ₂ to CO conversion system 125, includes in one embodiment an H ₂:CO₂ molar ratio of about 3:1, in another embodiment about 2.5:1, in yet another embodiment about 3.5:1, and in yet another embodiment greater than about 5:1. The composition of the H ₂: CO gas in the CO-enriched effluent stream 130 is as described above. In one embodiment, the gas composition in the hydrogen separation zone effluent 350 comprises a molar ratio of H ₂ to CO of greater than about 1:1 but no more than about 5:1 and a molar ratio of H ₂:CO:CO₂ of about 5:1:1, wherein ethanol is the product as described above and further as described above for other products. The gas composition of the tail gas stream 160 is as described above. The bypass embodiment is generally described above.

Fig. 10 is similar to fig. 9 with the addition of a hydrogen separation unit effluent compressor 370. When pressure swing adsorption is employed in the hydrogen separation unit 330, the hydrogen separation unit effluent 350 is typically below the pressure required for the bioreactor 142. The hydrogen separation unit effluent compressor 370 provides further compression of the hydrogen separation unit effluent to achieve the desired pressure for introduction into the bioreactor 142. The gas composition of the treated stream 290 prior to introduction into the CO ₂ to the CO conversion system 125 and in the CO-rich effluent stream 130 is as described above. The gas composition of the hydrogen separation unit effluent includes a molar ratio of H ₂ to CO that is greater than about 1:1 but no more than about 5:1 prior to introduction to the hydrogen effluent zone effluent compressor 370, and the molar ratio of H ₂:CO:CO₂ of the gas stream 365 may be about 5:1:1 for ethanol as a product as described above, and further as described above for other products. The composition of the gases in the tail gas stream 160 is as described above. The bypass embodiment is described above.

Fig. 11 is similar to fig. 6 except that the CO-rich effluent stream 130 from the CO ₂ to CO conversion system 125 further comprises methane from the hydrogen source 110 or methane as a byproduct of the CO ₂ to CO conversion system 125 involving rWGS technology. Over time, methane from one or both of these sources may accumulate in the bioreactor off-gas stream 160. When the methane concentration of the bioreactor off-gas stream 160 increases to, for example, more than 10 mole percent, and possibly more than a 50 mole percent threshold limit, at least a portion of the off-gas stream 160 is passed as an off-gas purge 390 to the methane conversion unit 400. An optional oxygen source 410 may provide an optional stream comprising oxygen 420 to the methane conversion unit 400. In some embodiments, the oxygen source 410 for the methane conversion unit 400 may be a water electrolyzer, wherein oxygen is a byproduct. The methanating unit 400 produces at least CO ₂ by oxidation of methane according to reaction CH ₄+2O₂→CO₂+2H₂ O and produces a methanated effluent stream 421 comprising at least CO ₂ and possibly additionally CO and H ₂, which may be combined with the tail gas stream 160 and passed to the first compressor 190. The methane reforming unit 400 may be a methane reforming unit, a methane steam reforming unit, a partial oxidation unit, an autothermal reforming unit, an oxidation unit, a combustion unit, a biogas reforming unit, or a gasification unit. When the methane conversion unit 400 involves steam reforming of methane represented by the following equation:

CH ₄+H₂ O (steam) →CO+3H ₂ (endothermic)

The stream comprising oxygen 420 may also be combusted in a burner of a heater to produce steam or heat a methane conversion unit. The methane conversion unit may involve autothermal reforming (ATR) which uses oxygen or carbon dioxide as a reactant to form a synthesis gas with methane. The reaction may be carried out in a single reactor in which methane is partially oxidized. The reaction can be described in the following equation:

CH ₄+O₂+CO₂→3H₂+3CO+H₂ O (using CO ₂)

C ₄+O₂+2H₂O→10H₂ +4CO% using steam

The gas composition of the treated stream 290 and the CO-rich effluent stream 130 is as described above. The gas composition in the tail gas stream 160 or tail gas sweep 390 typically comprises less than about 5 mole% co. In some embodiments, the molar ratio of H ₂:CO₂ of the tail gas stream 160 or tail gas purge 390 is equal to or less than about 3:1, and the accumulated methane is greater than about 5mol%. The bypass embodiment is as previously discussed.

In one embodiment, the optional additional hydrogen-comprising stream 430 generated from the hydrogen-generating source 110 is directly fed into the bioreactor 142, as discussed above. Microbial fermentation of CO in the presence of H ₂ can result in substantially complete carbon transfer into a product such as an alcohol, but in the absence of sufficient H ₂ only a portion of the available CO is converted to product and another portion is converted to CO ₂ as shown in the following equation: 6CO+3H ₂O→C₂H₅OH+4CO₂. Thus, in some embodiments, it may be beneficial to provide sufficient hydrogen to bioreactor 142. In another embodiment, an optional additional stream comprising CO ₂ 440 generated from gas generation source 220 is directly fed into bioreactor 142. Such an arrangement may be advantageous to maintain the partial pressure of CO ₂ in the CO ₂ depleted zone of bioreactor 142.

Fig. 12 relates to an embodiment in which the CO ₂ -to-CO conversion system 125 is selected as the rWGS system, and in particular depicts additional equipment for rWGS. The hydrogen generating source 110 and the first gaseous stream 120, as well as the gas generating source 220 and the second gaseous stream comprising CO ₂, and the combined feed stream 250 are all as described above. The gas treatment zone 182 and treated stream 290, plus bioreactor 142, fermentation product stream 150, and tail gas stream 160 are as described above.

The treated stream 290 is introduced into a preheater 560 where it is heated by indirect heat exchange with the rWGS reactor effluent 588 to provide a preheated stream 562. The preheated stream 562 is passed to an electric heater 564 for further heating to produce an electrically heated stream 566, which in turn is further heated in a combustion heater 568 to produce a fully heated stream 570. Different heating modes are employed to best utilize the available energy to achieve the target temperature of the rWGS reactor. The heat in the stream requiring cooling is transferred to the stream requiring heating and the spent combustible components are combusted in a burner, thereby generating heat to heat the stream requiring elevated temperature.

The fully heated stream 570 is introduced into an rWGS reactor 571, which may be a single stage or a multi-stage reactor system. In the rWGS reactor 571, at least a portion of the CO ₂ present in the fully heated stream 570 is converted to CO. Thus, the rWGS reactor effluent 588 is rich in CO as compared to the fully heated stream 570. Because the rWGS reactor effluent is at the temperature of the rWGS reactor 571, it contains available heat that can be used to heat another stream, and thus passes to the preheater 560 to indirectly exchange heat with the treated stream 290. The heat exchanged rWGS reactor effluent 563 is then passed from the preheater 560 to a heat recovery/steam generator 572 to further recover the available heat. The cold water stream 574 is passed to a heat recovery/steam generator 572 to receive an exchange of available heat from the heat exchanged rWGS reactor effluent 563 and to produce a steam stream 576 that may be used elsewhere in the overall process or in another process. The resulting lean heat stream 578 is passed to a water separation unit 580 to produce a stream comprising water 584 and lean water stream 582. Steam including water 584 may be directed to any portion of the process or another process requiring water. Lean water stream 582 is passed to air cooler 586 to provide CO-rich effluent stream 130.

The CO-rich effluent stream 130 can be divided into multiple portions, a first portion can be passed to optional mixer 590, or when optional mixer 590 is not present, the first portion can be passed to bioreactor 142. A second portion of the optional CO-rich effluent stream 130 may be passed to another unit, such as a buffer tank (not shown), or to an inoculant reactor, which may or may not be part of bioreactor 142. For periods of reduced supply of gaseous streams including CO ₂, it is advantageous to have a stored amount of CO-rich effluent stream 130. In the case of an inoculant reactor having a lower hydrogen requirement than a bioreactor, it may be advantageous to pass a second portion of the CO-enriched effluent stream 130 to the inoculant before adding any additional hydrogen to the CO-enriched effluent stream 130. An optional third portion of the CO-rich effluent stream 130 can be recycled to the combustion heater 568 to combust and provide heat in the burner of the combustion heater 568. This embodiment is particularly advantageous at start-up when the bioreactor 142 has not been operated to consume CO in the CO-rich effluent stream 130.

In some embodiments, it may be advantageous to regulate and control the amount of hydrogen provided to bioreactor 142 by providing an additional stream 430 comprising hydrogen from hydrogen generating source 110, which additional stream is passed to mixer 590. In mixer 590, the CO-rich effluent stream 130 is mixed with an additional stream 430 comprising hydrogen to produce a bioreactor feed stream 592. The ratio of the additional hydrogen-comprising stream 430 from the hydrogen source to the CO-rich effluent stream 130 is from about greater than 0:1 to about 4:1. The bioreactor feed stream is provided to bioreactor 142 and a fermentation product stream 150 is produced, as well as a bioreactor tail gas stream 160. The bioreactor tail gas stream 160 may be split into multiple portions and recycled to different locations within the process. The path of the bioreactor off-gas is typically dependent on the current state of operation of the process. For example, when the bioreactor 142 is operated in a mode that produces a substantial amount of CO ₂, the bioreactor off-gas 160 can have at least a portion recycled to the gas treatment zone 182 or to the CO-to-CO ₂ conversion system 125 for converting CO ₂ to CO. At any time, a portion of the bioreactor off-gas 160 may be supplied to the burner of the combustion heater 568 for combustion and heat generation. In embodiments where the bioreactor off-gas 160 contains methane, it is particularly advantageous to use at least a portion of the bioreactor off-gas 160 for combustion. It is contemplated that biogas from the wastewater treatment system may be combined with the bioreactor off-gas 160 and used for combustion and heating in the combustion heater 568. It is further contemplated that biogas from the wastewater treatment system may be recycled, or recycled directly to the bioreactor.

Fig. 13 relates to an embodiment wherein the separate hydrogen streams do not pass through the CO-to-CO ₂ conversion system, but are mixed downstream of the CO-to-CO ₂ conversion system to form the feed stream to the bioreactor. The separate hydrogen stream 602 may be obtained from a separate second hydrogen source 600 (as shown) or may be obtained from the hydrogen source 110. A separate hydrogen stream 602 comprising hydrogen may be passed to an optional hydrogen stream gas treatment zone 603 to produce a treated hydrogen stream 604 comprising hydrogen. The hydrogen stream gas treatment zone 603 may comprise a gas component removal unit and/or a gas desulfurization/acid gas removal unit. These two units may not be required in all embodiments and the hydrogen treatment zone 603 may contain only one of the gas component removal units or the gas desulfurization/acid gas removal units. Furthermore, the units in the hydrogen stream gas treatment zone 603 may be in any order. The treated hydrogen stream 604 produced from the hydrogen stream gas treatment zone 603 is passed to a mixer 590 and mixed with the treated CO-rich effluent stream 186 to produce a bioreactor feed stream 592.

The hydrogen generating source 110, the first gaseous stream 120 comprising hydrogen, the gas generating source 220, the second gaseous stream 140 comprising CO ₂, and the combined feed stream 250 are all as described above. The gas treatment zone 182 and treated stream 290 are described above, plus the CO to CO ₂ conversion system 125, CO-rich effluent stream 130, mixer 590, mixed stream 592, bioreactor 142, fermentation product stream 150, and tail gas stream 160, but the ratio of H ₂ to CO ₂ may be different. The second gas treatment zone 183 and the third gas treatment zone 187 are as described for the gas treatment zone 182.

Turning to the first gaseous stream 120 comprising hydrogen from the hydrogen generating source 110 and the second gaseous stream 140 comprising CO ₂ from the gas generating source 220, different ratios of hydrogen and CO ₂ in the streams are useful at different points throughout the operation of the process. In one embodiment, for example, the molar ratio of H ₂ in the first gaseous stream 120 comprising hydrogen to CO ₂ in the second gaseous stream 140 comprising CO ₂, i.e., H ₂:CO₂, In another embodiment about 2:1, and in yet another embodiment about 3:1. in an embodiment of a 1:1h ₂:CO₂ molar ratio, the volume of the first gaseous stream 120 comprising hydrogen may be twice the volume of the separate hydrogen stream 602 obtained from the separate second hydrogen source 600. In embodiments with a 2:1h ₂:CO₂ molar ratio, the volume of the first gaseous stream 120 comprising hydrogen may be half the volume of the separate hydrogen stream 602 obtained from the separate second hydrogen source 600. In the 3:1H ₂:CO₂ molar ratio embodiment, the first gaseous stream 120 comprising hydrogen provides all of the hydrogen needed and the separate hydrogen stream 602 obtained from the separate second hydrogen source 600 is not employed. Effectively, different amounts of hydrogen may bypass the CO to CO ₂ conversion system 125 by using the hydrogen stream 602/treated hydrogen stream 604. In one embodiment, the sum of the hydrogen in the first gaseous stream 120 comprising hydrogen plus the hydrogen in the separate hydrogen stream 602 provides enough hydrogen to produce a 3:1 molar ratio of H ₂:CO₂, where CO ₂ is measured in the second gaseous stream 140 comprising CO ₂.

The tail gas stream 160 may be recycled to the bioreactor 142 or to the CO-to-CO ₂ conversion system 125. Optionally, the tail gas stream 160 can be passed through a third gas treatment zone 187 to produce a treated tail gas stream 185, which is then passed to the CO ₂ conversion system 125. The second gas treatment zone 183 can optionally separate a portion of the CO-rich effluent stream 130, which can be recycled as stream 181 to the CO-to-CO ₂ conversion system 125.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference in their entirety as if each reference were individually indicated to be incorporated by reference. The reference to the present specification is not an admission that the reference forms a part of the common general knowledge in the field of endeavour in any country.

Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. For example, unless otherwise indicated, any concentration range, percentage range, ratio range, integer range, size range, or thickness range should be understood to include any integer value within the recited range and to include fractions thereof (e.g., tenths and hundredths of integers) where appropriate. Unless indicated otherwise, ratios are molar ratios and percentages are by weight.

All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the disclosure and does not pose a limitation on the scope of the disclosure unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosure.

Embodiments of the present disclosure are described herein. Variations of those embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description and, where appropriate, use of such variations is intended to be within the scope of the present disclosure that may be practiced otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

1. An integrated process for producing at least one fermentation product from a gaseous stream, the process comprising:

a) Obtaining a first gaseous stream comprising hydrogen and a second gaseous stream comprising CO ₂;

b) Passing at least a portion of the first gaseous stream and at least a portion of the second gaseous stream to a CO ₂ to CO conversion system operating under conditions that produce a CO-rich effluent stream;

c) Passing the CO-enriched effluent stream to a bioreactor having a culture of one or more C1 immobilized bacteria and fermenting to produce at least one fermentation product stream and a bioreactor tail gas stream;

d) Compressing the bioreactor off-gas stream to produce a compressed bioreactor off-gas stream;

e) Passing at least a first portion of the compressed bioreactor tail gas stream in any order to:

i) A gas desulfurization and/or acid gas removal unit; or (b)

Ii) a gas component removal unit; or (b)

Iii) Both the gas desulfurization and or acid gas removal unit and the gas component removal unit;

To produce a compressed treated bioreactor tail gas stream;

f) Recycling the compressed treated bioreactor off-gas stream:

i) To be combined with the first gaseous stream, the second gaseous stream, or a combination thereof; or (b)

Ii) to be recycled to the CO ₂ to CO conversion system; or (b)

Iii) To be combined with the CO-rich effluent stream; or (b)

Iv) any combination thereof; and

G) Optionally recycling a second portion of the compressed bioreactor tail gas stream to be combined with the CO-rich effluent stream or recycled to the bioreactor and to the bioreactor

The method further comprises:

i) Combining at least a second portion of the first gaseous stream, at least a second portion of the second gaseous stream, or a combination thereof with the CO-rich effluent stream; or (b)

Ii) passing at least a second portion of the first gaseous stream, at least a second portion of the second gaseous stream, or a combination thereof to the bioreactor.

2. The method of claim 1, further comprising compressing any portion of the first gaseous stream, the second gaseous stream, or a combination thereof.

3. The method of claim 1, further comprising controlling a relative amount of the first portion of the compressed tail gas stream and the second portion of the compressed tail gas stream using a control valve.

4. The method of claim 1, further comprising passing at least a portion of the tail gas stream to a tail gas CO ₂ to CO conversion system selected from a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a plasma conversion unit, a gasification unit, or a reforming unit to produce a CO-rich effluent stream and recycling a second CO-rich effluent stream to the bioreactor.

5. The method of claim 1, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ to 1.

6. The method of claim 1, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ to 1.

7. The method of claim 1, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ of 4.33:1:1.

8. The method of claim 1, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ of 3:1:1.

9. The method of claim 1, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ of 2:1:1.

10. The method of claim 1, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ of 1:1:1.

11. The method of claim 1, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ to 1:3:1.

12. The method of claim 1, wherein the CO ₂ -to-CO conversion system comprises at least one of: a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a reforming unit or a plasma conversion unit.

13. The method according to claim 1, wherein:

a) The at least one fermentation product is selected from ethanol, acetate, butanol, butyrate, 2, 3-butanediol, lactate, butene, butadiene, methyl ethyl ketone, ethylene, acetone, isopropanol, lipids, 3-hydroxypropionate, isoprene, fatty acids, 2-butanol, 1, 2-propanediol, hexanol, octanol, or 1-propanol; or (b)

B) The first gaseous stream comprising hydrogen is generated by a hydrogen generation source comprising at least one of: a water electrolyzer, a hydrocarbon reforming source, a hydrogen purification source, a solid biomass gasification source, a solid waste gasification source, a coal gasification source, a hydrocarbon gasification source, a methane pyrolysis source, a refinery tail gas generation source, a plasma reforming reactor, a partial oxidation reactor, or any combination thereof; or alternatively

C) Wherein the second gaseous stream comprising CO ₂ is generated by a gas generation source comprising at least one of: a sugar-based ethanol production source, a first generation corn ethanol production source, a second generation corn ethanol production source, a sugar cane ethanol production source, a sucrose ethanol production source, a beet ethanol production source, a molasses ethanol production source, a wheat ethanol production source, a grain-based ethanol production source, a starch-based ethanol production source, a cellulose-based ethanol production source, a cement production source, a methanol synthesis source, an olefin production source, a steel production source, an iron alloy production source, a refinery tail gas production source, a post-combustion gas production source, a biogas production source, a landfill production source, an ethylene oxide production source, a methanol production source, an ammonia production source, a mined CO ₂ production source, a natural gas processing production source, a gasification source, an organic waste gasification source, a direct air capture, or any combination thereof; or (b)

D) Any combination thereof.

14. The method of claim 1, wherein the at least one C1-immobilized bacterium is selected from clostridium ethanogenum (Clostridium autoethanogenum), clostridium yangenum (Clostridium ljungdahlii), or clostridium rahnii (Clostridium ragsdalei).

15. An integrated process for producing at least one fermentation product from a gaseous stream, the process comprising:

b) Optionally, compressing at least a portion of the first gaseous stream, at least a portion of the second gaseous stream, or any combination thereof in a first compressor to produce a compressed first gaseous stream, a compressed second gaseous stream, and or a compressed combination of the first gaseous stream and the second gaseous stream;

c) The following are treated in a gas treatment zone comprising a gas component removal unit, a gas desulfurization/acid gas removal unit, or both:

i) At least a portion of the first gaseous stream or the compressed first gaseous stream or both; and at least a portion of the second gaseous stream or the compressed second gaseous stream or both; or (b)

Ii) said compressed combination of the first gaseous stream and the second gaseous stream;

to produce a processed stream;

d) Converting CO ₂ in at least a first portion of the treated stream in a CO ₂ to CO conversion system operating under conditions that produce a CO-rich effluent stream to form CO;

e) Passing the CO-enriched effluent stream to a bioreactor having a culture of one or more C1 immobilized bacteria and fermenting to produce at least one fermentation product stream and a bioreactor tail gas stream; and

F) Recycling the tail gas stream to the first compressor, the gas treatment zone, the CO ₂ to CO conversion system, the first gaseous stream, the second gaseous stream, or a combination of the first gaseous stream and the second gaseous stream,

The method further comprises:

i) A second gaseous stream comprising hydrogen is passed from the hydrogen source to the bioreactor or combined with the CO-rich effluent stream, and a second gaseous stream comprising CO ₂ is passed from the CO ₂ source to the bioreactor or combined with the CO-rich effluent stream, or any combination thereof.

16. The method of claim 15, further comprising combining the CO-rich effluent stream with at least a portion of:

a) The processed stream; or (b)

B) The first gaseous stream; or (b)

C) Said second gaseous stream; or (b)

D) Said combination of said first gaseous stream and said second gaseous stream; or (b)

E) Said compressed first gaseous stream; or (b)

F) Said compressed second gaseous stream; or (b)

G) Said compressed combination of first gaseous stream and second gaseous stream; or (b)

H) Any combination thereof.

17. The method of claim 15, further comprising passing at least a portion of the tail gas stream to a tail gas CO ₂ to CO conversion system selected from a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a plasma conversion unit, a gasification unit, or a reforming unit to produce a CO-rich effluent stream and recycling a second CO-rich effluent stream to the bioreactor.

18. The method of claim 15, wherein the CO-rich effluent stream further comprises hydrogen and CO ₂ and comprises H ₂:CO:CO₂ in a 5:1:1 molar ratio.

19. The method of claim 15, wherein the CO-rich effluent stream further comprises hydrogen and CO ₂ and comprises H ₂:CO:CO₂ in a 4.5:1:1 molar ratio.

20. The method of claim 15, wherein the CO-rich effluent stream further comprises hydrogen and CO ₂ and comprises H ₂:CO:CO₂ in a 4.33:1:1 molar ratio.

21. The method of claim 15, wherein the CO-rich effluent stream further comprises hydrogen and CO ₂ and comprises H ₂:CO:CO₂ in a 3:1:1 molar ratio.

22. The method of claim 15, wherein the CO-rich effluent stream further comprises hydrogen and CO ₂ and comprises H ₂:CO:CO₂ in a 2:1:1 molar ratio.

23. The method of claim 15, wherein the CO-rich effluent stream further comprises hydrogen and CO ₂ and comprises H ₂:CO:CO₂ in a 1:1:1 molar ratio.

24. The method of claim 15, wherein the CO-rich effluent stream further comprises hydrogen and CO ₂ and comprises H ₂:CO:CO₂ in a 1:3:1 molar ratio.

25. The method of claim 15, wherein the CO ₂ -to-CO conversion system comprises at least one of: a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a reforming unit or a plasma conversion unit.

26. The method of claim 15, wherein the gas treatment zone further comprises a deoxygenation unit, a catalytic hydrogenation unit, an adsorption unit, a thermal oxidizer, or any combination thereof.

27. The method of claim 15, wherein the at least one fermentation product is selected from ethanol, acetate, butanol, butyrate, 2, 3-butanediol, lactate, butene, butadiene, methyl ethyl ketone, ethylene, acetone, isopropanol, lipid, 3-hydroxypropionate, isoprene, fatty acids, 2-butanol, 1, 2-propanediol, hexanol, octanol, or 1-propanol.

28. The method according to claim 15, wherein:

a) The first gaseous stream comprising hydrogen is generated by a hydrogen generation source comprising at least one of: a water electrolyzer, a hydrocarbon reforming source, a hydrogen purification source, a solid biomass gasification source, a solid waste gasification source, a coal gasification source, a hydrocarbon gasification source, a methane pyrolysis source, a refinery tail gas generation source, a plasma reforming reactor, a partial oxidation reactor, or any combination thereof; or (b)

B) The second gaseous stream comprising CO ₂ is generated by a gas generation source comprising at least one of: a sugar-based ethanol production source, a first generation corn ethanol production source, a second generation corn ethanol production source, a sugar cane ethanol production source, a sucrose ethanol production source, a beet ethanol production source, a molasses ethanol production source, a wheat ethanol production source, a grain-based ethanol production source, a starch-based ethanol production source, a cellulose-based ethanol production source, a cement production source, a methanol synthesis source, an olefin production source, a steel production source, an iron alloy production source, a refinery tail gas production source, a post-combustion gas production source, a biogas production source, a landfill production source, an ethylene oxide production source, a methanol production source, an ammonia production source, a mined CO ₂ production source, a natural gas processing production source, a gasification source, an organic waste gasification source, a direct air capture, or any combination thereof; or alternatively

C) Wherein at least one of the C1-immobilized bacteria is selected from clostridium ethanogenum, clostridium yang, or clostridium rakii; or (b)

D) Any combination thereof.

29. The method of claim 15, further wherein the CO-rich effluent stream comprises hydrogen, and the method further comprises separating hydrogen from the CO-rich effluent stream and recycling the separated hydrogen to be combined with the tail gas stream or recycled to the compressor.

30. The method of claim 29, further comprising compressing a remaining portion of the CO-rich effluent stream after the hydrogen separation.

31. The method of claim 15, wherein the tail gas stream comprises methane, the method further comprising passing a portion of the tail gas stream to a methane conversion unit to produce a methane conversion unit effluent, and combining the methane conversion unit effluent with the tail gas stream.

32. The method of claim 31, further comprising generating a stream comprising oxygen from an oxygen source and passing the stream comprising oxygen to the methane conversion unit.

33. The method of claim 15, wherein the second gaseous stream comprising hydrogen from the hydrogen source is combined with the CO-rich effluent stream or the second gaseous stream comprising CO ₂ from the CO ₂ source is combined with the CO-rich effluent stream or both are utilized in a mixer.

34. The method of claim 15, wherein a ratio of the second gaseous stream comprising hydrogen from the hydrogen source to the CO-rich effluent stream entering the bioreactor is greater than 0:1 to 4:1.

35. The method of claim 15, wherein the CO ₂ -to-CO conversion system includes a combustion heater having a burner, and the tail gas stream is recycled to at least the burner of the combustion heater.

36. The method of claim 15, wherein the CO ₂ -to-CO conversion system comprises a steam generator that produces steam, or a water separation unit that produces a water stream, or both.

37. The method of claim 15, further comprising passing a portion of the CO-rich effluent stream to an inoculator reactor, a buffer tank, or both.

38. An integrated process for producing at least one fermentation product from a gaseous stream, the process comprising:

b) Passing at least a portion of the second gaseous stream and a portion of the first gaseous stream to a CO ₂ to CO conversion system operating under conditions that produce a CO-rich effluent stream;

c) Passing at least a portion of the first gaseous stream comprising hydrogen and the CO-enriched effluent stream to a bioreactor having a culture of one or more C1 immobilized bacteria and fermenting to produce at least one fermentation product stream and a bioreactor tail gas stream;

i) A gas desulfurization and/or acid gas removal unit; or (b)

Ii) a gas component removal unit; or (b)

To produce a compressed treated bioreactor tail gas stream;

f) Recycling the compressed treated bioreactor off-gas stream:

Ii) to be recycled to the CO ₂ to CO conversion system; or (b)

Iii) To be combined with the CO-rich effluent stream; or (b)

Iv) any combination thereof; and

G) A second portion of the compressed bioreactor tail gas stream is optionally recycled to be combined with the CO-rich effluent stream or recycled to the bioreactor.

39. The method of claim 38, further comprising passing at least another portion of the first gaseous stream comprising hydrogen to the CO ₂ to a CO conversion system.

40. The method of claim 38, further comprising compressing any portion of the first gaseous stream, the second gaseous stream, or a combination thereof.

41. The method of claim 38, further comprising controlling a relative amount of the first portion of the compressed tail gas stream and the second portion of the compressed tail gas stream using a control valve.

42. The method of claim 38, further comprising passing at least a portion of the tail gas stream to a tail gas CO ₂ to CO conversion system selected from a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a plasma conversion unit, a gasification unit, or a reforming unit to produce a CO-rich effluent stream and recycling a second CO-rich effluent stream to the bioreactor.

43. The method of claim 38, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ to 1.

44. The method of claim 38, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ to 1.

45. The method of claim 38, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ of 4.33:1:1.

46. The method of claim 38, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ of 3:1:1.

47. The method of claim 38, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ of 2:1:1.

48. The method of claim 38, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ of 1:1:1.

49. The method of claim 38, wherein the CO-rich effluent stream comprises a molar ratio of H ₂:CO:CO₂ to 1:3:1.

50. The method of claim 38, wherein the CO ₂ -to-CO conversion system comprises at least one of: a reverse water gas shift unit, a thermocatalytic conversion unit, a partial combustion unit, a reforming unit or a plasma conversion unit.

51. The method according to claim 38, wherein:

B) The first gaseous stream comprising hydrogen is generated by a hydrogen generation source comprising at least one of: a water electrolyzer, a hydrocarbon reforming source, a hydrogen purification source, a solid biomass gasification source, a solid waste gasification source, a coal gasification source, a hydrocarbon gasification source, a methane pyrolysis source, a refinery tail gas generation source, a plasma reforming reactor, a partial oxidation reactor, or any combination thereof; or (b)

C) The second gaseous stream comprising CO ₂ is generated by a gas generation source comprising at least one of: a sugar-based ethanol production source, a first generation corn ethanol production source, a second generation corn ethanol production source, a sugar cane ethanol production source, a sucrose ethanol production source, a beet ethanol production source, a molasses ethanol production source, a wheat ethanol production source, a grain-based ethanol production source, a starch-based ethanol production source, a cellulose-based ethanol production source, a cement production source, a methanol synthesis source, an olefin production source, a steel production source, an iron alloy production source, a refinery tail gas production source, a post-combustion gas production source, a biogas production source, a landfill production source, an ethylene oxide production source, a methanol production source, an ammonia production source, a mined CO ₂ production source, a natural gas processing production source, a gasification source, an organic waste gasification source, a direct air capture, or any combination thereof; or alternatively

D) Wherein the at least one C1-immobilized bacterium is selected from Clostridium ethanogenum, clostridium Yankeei or Clostridium ramosum; or (b)

E) Any combination thereof.