PROCESS

This application complains priority from U.S. Provisional App. No. 63/368,291, filed July 13, 2022. The entirety of all of the aforementioned applications in incorporated herein by reference.

FIELD

[0001] The present invention relates to chemotrophic carbon capture and desulfurization and concerns a combined process of bio-desulfurization and carbon capture utilizing chemotrophs to produce one or more bio-products.

[0002] Bio-desulfurization is a known process for removing sulfur/sulfides from gas streams (e.g. natural gas, associated gas, syngas, amine acid gas, flue gas, landfill gas, biogas, effluent from anaerobic digesters), and also from liquid streams such as diesel and crude oil. The primary or sole focus of conventional bio-desulfurization processes is the removal of sulfur (e.g. H2S). Such processes are not typically concerned with carbon capture - either at all or with conditions desirable for its optimization. In fact, conventional bio-desulfurization processes such as the Thiopaq O&G process generally seek to minimize the amount of biomass build-up (carbon capture) for ease of operation of the bio-desulfurization process.

BACKGROUND

[0003] US 11,091,781 and US 10,597,681 disclose systems and methods for fixing carbon using bacteria. The systems include a reaction chamber with a solution contained therein. The solution may include hydrogen, carbon dioxide, bioavailable nitrogen, and a chemolithoautotrophic bacteria. The system may also include a pair of electrodes that split water contained within the solution to form the hydrogen. Additionally, the system may be operated so that a concentration of the bioavailable nitrogen in the solution is below a threshold nitrogen concentration to cause the chemolithoautotrophic bacteria to produce a product.

[0004] US 2022/0154228 discloses compositions and methods for a hybrid biological and chemical process that captures and converts carbon dioxide and/or other forms of inorganic carbon and/or CI carbon sources and/or mixtures containing CI chemicals into organic chemicals including biofuels or other valuable biomass, chemical, industrial, or pharmaceutical products.

[0005] US 9,957,534 discloses microorganisms containing exogenous or heterologous nucleic acid sequences, wherein the microorganisms are capable of growing on gaseous carbon dioxide, gaseous hydrogen, syngas, or combinations thereof. In some embodiments the microorganisms are chemotrophic bacteria that produce or secrete at least 10% of lipid by weight. Also disclosed are methods of fixing gaseous carbon into organic carbon molecules useful for industrial processes, and methods of manufacturing chemicals or producing precursors to chemicals useful in fuels.

[0006] US 10,507,426 and US 9,764,279 disclose methods and systems to achieve clean fuel processing systems in which carbon dioxide emissions from sources may be processed in at least one processing reactor containing a plurality of chemoautotrophic bacteria which can convert the carbon dioxide emissions into biomass which may then be used for various products such as biofuels, fertilizer, or feedstocks. Sulfate-reducing bacteria may be used to supply sulfur containing compounds to the chemoautotrophic bacteria.

[0007] US 10,376,837 discloses methods and systems to achieve clean fuel processing systems in which carbon dioxide emissions from sources may be processed in at least one processing reactor containing a plurality of chemoautotrophic bacteria which can convert the carbon dioxide emissions into biomass which may then be used for various products such as biofuels, fertilizer, or feedstocks. Bacteria that reduce oxidized nitrogenous species may be used to supply reduced nitrogenous compounds to the chemoautotrophic bacteria.

[0008] US 10,543,458 discloses a process to treat a gas comprising hydrogen sulfide and mercaptans, comprising the steps: (a) contacting the hydrogen sulfide and mercaptans comprising gas with an aqueous solution comprising sulfide-oxidizing bacteria thereby obtaining a loaded aqueous solution and a gas having a lower content of hydrogen sulfide and mercaptans, (b) contacting the loaded aqueous solution with mercaptan reducing microorganisms immobilized on a carrier under anaerobic conditions, (c) separating the aqueous solution obtained in step (b) from the mercaptan reducing microorganisms to obtain a first liquid effluent, and (d) contacting the first liquid effluent with an oxidant to regenerate the sulfide-oxidizing bacteria to obtain a second liquid effluent comprising regenerated sulfide-oxidizing bacteria. The sulfide-oxidizing bacteria as present in step (a) are comprised of regenerated sulfide-oxidizing bacteria obtained in step (d).

[0009] US 10,801,045 discloses pathways, mechanisms, systems and methods to confer chemoautotrophic production of carbon-based products, such as sugars, alcohols, chemicals, amino acids, polymers, fatty acids and their derivatives, hydrocarbons, isoprenoids, and intermediates thereof, in organisms such that these organisms efficiently convert inorganic carbon to organic carbon-based products of interest using inorganic energy, such as formate, and the use of organisms for the commercial production of various carbonbased products.

[0010] WO 2014/200598 discloses methods and systems purported to achieve clean fuel processing systems in which carbon dioxide emissions are processed in a reactor containing a plurality of chemoautotrophic bacteria which can convert carbon dioxide into biomass. Bacteria hat reduce oxidized nitrogenous species may be used to supply reduced nitrogenous compounds to the chemoautotrophic bacteria.

[0011] EP 3800274 discloses a method for producing biomass comprising converting a sulfur compound to hydrogen sulfide by sulfate reducing microorganisms and subsequently converting said hydrogen sulfide into biomass by means of sulfide oxidizing bacteria, wherein said conversions are said to be mediated by electron transfer of more energy rich gases.

[0012] US 2017/0218740 discloses a method for converting carbon dioxide into biomass within subterranean formations by introducing chemolithoautotrophic microbes into the formation so as to fix carbon dioxide within the formation into biomass.

[0013] US 4,760,027 discloses a method for desulfurizing gases using chemoautotrophic bacteria of the Thiobacillus genus under aerobic conditions to convert sulfides to sulfates either as a sulfide removal process or as a process for producing biomass, and is said to be particularly suited to the disposal of hydrogen sulfide.

[0014] WO 2018056787 relates to a method for continuously converting carbon dioxide into a useful substance by linking a mineralization process of carbon dioxide with a metabolic reaction of a satisfactory microorganism.

[0015] WO 2011056183 discloses methods for the capture and conversion of carbon dioxide into organic chemicals utilizing chemoautotrophic microorganisms to fix inorganic carbon into organic compounds through chemosynthesis. An additional feature described are process steps whereby electron donors used for the chemosynthetic fixation of carbon are generated by chemical or electrochemical means, or are produced from inorganic or waste sources.

[0016] The prior art is primarily concerned with either removal of sulfur (e.g. EES) or CO2 capture and/or utilization. The prior art fails to provide a satisfactory process where carbon capture is linked with sulfur removal.

[0017] In a process for producing one or more bio-products comprising of capturing carbon dioxide (CO2), the removal of further impurities such as hydrogen sulfide (H2S) results in the production of an improved product. None of the prior art documents contain any satisfactory teaching as to how to optimize removal of H2S in combination with such a process where carbon capture is optimized using a microorganism.

SUMMARY

[0018] The object of the present invention is to provide an improved process for capturing carbon dioxide to produce one or more bio-products, in which sulfur (e.g. H2S) is also removed and utilized, unlike in conventional processes in the art.

[0019] An aspect of the application is a microbiological process for the conversion of CO2 into one or more bio-products, in which the energy required for the microbiological conversion is at least partially provided by the concomitant microbiological oxidation of a sulfurous feedstock.

[0020] An aspect of the application is an apparatus for the conversion of CO2 into one or more bio-products, in which the energy required for the microbiological conversion is at least partially provided by the concomitant microbiological oxidation of a sulfurous feedstock.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The invention will now be more particularly described with reference to the following examples and Figures, in which;

[0022] Figure 1 depicts a schematic diagram of a process of sequestering carbon and removing H2S according to the invention, wherein a co-mingled feed is used.

[0023] Figure 2 depicts a schematic diagram of a process of sequestering carbon and removing H2S according to the invention, wherein separate feeds are used.

[0024] Figure 3 depicts a schematic diagram of a process according to the invention in which elemental sulfur produced by the process is recycled via a sulfur reducing bioreactor to generate H2S for use in the process as the sulfurous feedstock.

[0025] Figure 4 depicts a graph depicting microbial growth (determined by Total Solids Content (TSS) as a function of time and thiosulfate concentration.

[0026] Figure 5 graphically represents total solids content (TSS) and pH of the reactor media pursuant to Example 2

[0027] Figure 6 depicts a graph showing cell density, thiosulfate and sulfate concentration over the course of about 400 hours with reference to Example 3 conducted using a continuous flow stirred tank reactor. DETAILED DESCRIPTION OF THE INVENTION

[0028] Reference will be made in detail to certain aspects and exemplary embodiments of the application, illustrating examples in the accompanying structures and figures. The aspects of the application will be described in conjunction with the exemplary embodiments, including methods, materials and examples, such description is non-limiting and the scope of the application is intended to encompass all equivalents, alternatives, and modifications, either generally known, or incorporated here. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. One of skill in the art will recognize many techniques and materials similar or equivalent to those described here, which could be used in the practice of the aspects and embodiments of the present application. The described aspects and embodiments of the application are not limited to the methods and materials described.

[0029] In this specification one or more bio-products means one or more products derived from organic material available on a renewable or recyclable basis, and may include materials, chemicals and energy. Specific examples of bio-products include, but are not limited to, biomass, biochemicals, lipids, carbohydrates, and alcohols, and include polyhydroxyalkanoates, polyhydroxybutyrates, polyhydroxyvalerates and the like.

[0030] A further object of the present invention is to provide a system for carrying out the improved process that is efficient when compared to conventional methods, that is capable of enhancing bio-product production, and that allows control of bio-product composition.

[0031] According to the present invention there is provided a microbiological process for the conversion of CO2 into one or more bio-products, in which the energy required for the microbiological conversion is at least partially provided by the concomitant microbiological oxidation of a sulfurous feedstock.

[0032] By “concomitant” is meant that the microbiological conversion of CO2 into one or more bio-products takes place in situ alongside the microbiological oxidation of the sulfurous feedstock supplied to the site of the microbiological conversion for the purpose of providing energy for the microbiological conversion. Typically the process of the invention provides contemporaneous and co-located microbiological conversion of CO2 and microbiological oxidation of sulfurous feedstock. [0033] Preferably the CO2 and the sulfurous feedstock are supplied to the process as one or more waste streams from one or more industrial processes and are contacted together in a bioreactor charged with one or more microbiological materials adapted for the microbiological conversion of CO2 into one or more bio-products and for the concomitant microbiological oxidation of the sulfurous feedstock to provide energy for the microbiological conversion of CO2.

[0034] The sulfurous waste stream from one or more industrial processes is preferably an JLS-containing waste stream, and may an H2S waste stream.

[0035] Hence, according to the present invention there is provided a microbiological process for the conversion of CO2 into one or more bio-products, in which the energy required for the microbiological conversion is at least partially provided by the concomitant microbiological oxidation of a sulfurous feedstock, the process comprising the steps of: i. contacting raw carbon dioxide and sulfur-containing feedstocks, either separately or in combination, with an absorption or dissolution medium to form a reagent stream comprising dissolved or absorbed inorganic carbon and sulfur; ii. contacting at least a portion of the reagent stream with a microbial broth in a bioreactor to oxidize sulfur and contemporaneously produce one or more bio-products from the carbon dioxide.

[0036] Contacting of the raw carbon dioxide and sulfur-containing feedstocks, either separately or in combination, with an absorption or dissolution medium may take place in one or more fluid contactors.

[0037] The process of the invention may further comprise: iii. separating the one or more bio-products into one or more bio-products and a liquid stream; and iv. recycling at least a portion of the liquid stream to step i. of the process for use as, or part of, the absorption or dissolution medium.

[0038] In step iv of the said process the pH of the absorption or dissolution medium may be controlled to facilitate its capacity to absorb or dissolve carbon dioxide and to contribute to reaction conditions in the bioreactor conducive to production of the one or more bio-products. [0039] The pH control of the recycle stream is taught in our co-pending but currently unpublished application USSN 63364275 filed May 6, 2022 - the entire disclosure of which is hereby incorporated by reference.

[0040] The microbiological process is preferably effected by one or more chemotrophic organisms. Preferably one or more of the chemotrophic organisms are sulfur oxidizing bacteria. Preferably the sulfurous feedstock is at least partially oxidized to elemental sulfur by the sulfur oxidizing bacteria.

[0041] Chemotrophic organisms may be provided as a single genus, species and or strain. Consortia of different organisms may also be used. The organisms may be aerobic, anaerobic, facultatively or otherwise.

[0042] The invention finds utilization in any industrial process in which both sulfide (or sulfanyl - typically primarily H2S but also mercaptans/thiols etc. may be envisaged) and CO2 are present. The process of the invention can be applied in downstream facilities such as refineries and chemical plants, midstream facilities such as acid gas treatment plant and acid gas injection wells, and upstream industry such as sour oil and gas wells, biogas and landfill gas facilities. The operators of such facilities when utilizing the process of the invention may benefit from regulatory/governmental incentives with respect to carbon sequestration, and also stand to achieve effective desulfurization without resort to capital-intensive and operationally complex Claus units and processes.

[0043] The dissolved or absorbed inorganic carbon is typically provided in the form of a bicarbonate or carbonate (preferably at least mostly bicarbonate).

[0044] The dissolved or absorbed inorganic sulfur is typically provided in the form of a sulfide, sulfhydryl or sulfanyl (most commonly sulfhydryl - e.g. NaSH).

[0045] A key advantage of the present invention is combined CO2 capture and sulfur removal in a single process which can both abate greenhouse gas emissions, as well as safely remediate hazardous sulfurous streams.

[0046] Certain efforts have been made in the prior art to promote the use of combinatory bioreactors providing both sulfur-reducing microorganisms to generate sulfide (or sulfhydryl or sulfanyl) from feedstock containing sulfur in higher oxidation states than -2 or -1. However, such arrangements ultimately suffer from complexity and practical difficulties in maintaining physical and chemical conditions conducive to the thriving of multiple microbiological populations adapted for sulfur reduction on the one hand and CO2- to-biomass conversion on the other. The process of the present invention preferentially generates the required energy for CO2 conversion directly from the oxidation of industrial waste streams containing sulfur in oxidation state -2 or -1 and does not rely on the use of sulfur-reducing microorganisms.

[0047] As is well known, carbon dioxide (CO2) is a common greenhouse gas emission, produced by burning fuels. Conventional methods of carbon capture include photosynthetic approaches, and sequestration in oil deposits. Hydrogen sulfide (H2S) is a highly hazardous gas, which is toxic to humans and inhibits cellular respiration. Conventionally H2S is removed from fuel gases by amine gas treating technology, where it is converted to an ammonium salt, and subsequently to elemental sulfur.

[0048] Linking carbon capture with H2S removal has a distinct advantage in that oxidation of H2S to elemental sulfur provides the electrons and energy needed for carbon fixation, reducing the overall energy required for the process compared to conventional processes in the art, and in the process of the invention generating one or more useful bioproducts.

[0049] Preferably therefore, the process of the invention utilizes at least one industrial waste stream comprising sulfur in oxidation state -2 or -1, and at least one industrial waste stream comprising CO2 as feedstock for the process.

[0050] The required pH control may be effected by biological means (e.g. selection of suitable microbes and/or microbial digestion conditions), chemical means (e.g. by adjusting the pH of the absorption or dissolution medium or of the recycle stream which contributes to it), or by both.

[0051] The pH of the absorption or dissolution medium may for example be adjusted by the addition of make up water. Often it will be desirable to increase the pH of the recycle stream within a desired range, which can be achieved by the addition of alkaline make up water.

[0052] The recycle stream may have a pH of from about 10.5 to about 11.75. In one embodiment, the recycle stream has a pH of from about 11 to about 11.6, for example from about 11 to 11.5.

[0053] Advantageously, a pH of between about 10.5 and about 11.75 prevents unwanted or undesirable live bacteria (other than those responsible for CO2 to biomass conversion in the bioreactor) from entering in live form or from thriving in the gas contactor or absorption column.

[0054] In some embodiments, make up water or solvent may be added to the recycle stream prior to the recycle stream returning to the one or more gas contactors or absorption columns and/or to the bioreactor. [0055] Preferably, the pH of the liquid stream from the one or more gas contactor or absorption columns to the bioreactor is preferably maintained from about 8 to about 11, more preferably from about 8.5 to about 11, or from about 9 to about 11, for example from about 9 to about 10.5 or from about 9 to about 10.

[0056] If the pH of the liquid stream is not within the desired range, an alkaline compound, for example, sodium hydroxide, may be added into makeup water to maintain the pH in the desired range. Therefore, in some embodiments the makeup water comprises an alkaline compound. In some further embodiments, the makeup water comprises sodium hydroxide.

[0057] The alkaline compound, for example sodium hydroxide, may be added to the makeup water to increase the pH of the makeup water to from about 12 to about 13. Preferably, the resulting pH of the makeup water is from about 12.25 to about 12.75, for example about 12.5.

[0058] The inventors of the present invention have found that by increasing pH of the make-up water, optimization of the overall process is achieved. Firstly, the increase in pH can sterilize the recycle stream. Sterilization of the recycle stream can further be achieved by any methods known in the art, including, but not limited to, raising the pH of the recycle stream to prevent growth, adding biocide, adding bleaching agent(s), UV sterilization, gamma irradiation or increasing temperature.

[0059] Additionally, increasing the pH may improve carbon dioxide absorption and prevent unwanted microbial growth in the gas contactor or absorption column. It may also help avoid sulfuric acid formation in the bioreactor.

[0060] The process of the invention is particularly effective in reducing the energy required for carbon capture and utilization, and removing harmful contaminants from the bioproducts (for example biomass used to produce fuels). In conventional chemical processes a large part of energy required for carbon capture is consumed in regenerating the solvent used for the CO2 and H2S absorption. In the present invention, biological systems are used to consume the dissolved CO2 present in the form of bicarbonate in solution, and the H2S present in the form of elemental sulfur, thereby producing the recyclable solvent and saving the energy conventionally needed for regeneration of solvent.

[0061] The source of the fluid feedstock stream may for example be flue gas, ambient air, and/or any other process gas stream(s) containing carbon dioxide and sulfurous material (such as hydrogen sulfide) - the raw feedstock(s). The use of such sources advantageously aids in reducing otherwise detrimental carbon dioxide and sulfurous emissions. The raw feedstock may be provided as a single stream comprising a mixture of CO2 and sulfurous material (e.g. H2S), or as two separate streams individually comprising CO2 and sulfurous material (e.g. H2S).

[0062] The contacting of the raw feedstock(s) with an absorption or dissolution medium to form a reagent stream comprising dissolved inorganic carbon and sulfur is effected in a vessel suitable for dissolving or absorbing a fluid feedstock in the absorption or dissolution medium. We use the term “gas contactor or absorption column” to indicate such a suitable vessel (and, as will be apparent, more than one gas contactor or absorption column may be provided). The absorption/dissolution medium typically has a relatively low carbon dioxide and sulfurous content, which is substantially increased by contact with the raw feedstock. Thus, the process may further comprise increasing the carbonaceous and sulfurous content of the recycle stream by dissolving or absorbing CO2 and sulfurous feedstock into the reagent stream, for example with the aid of one or more gas contactors or absorption columns.

[0063] As mentioned, the process may utilize two (or more) separate gas contactors or absorption columns, especially when there are separate streams of CO2 and sulfurous feedstock to the process. A system comprising two (or more) gas contactors or absorption columns provides a greater degree of operational flexibility - for example by making it easier to control the C/S ratio in the reagent stream. The C/S ratio may be important in controlling the specification of the end bio-product(s). When the sulfurous stream is H2S in that case w/w CO2/H2S ratio in the (combined) feedstock may be from about 0.1 : 1 to about 100: 1, for example from about 1 : 1 to about 50: 1, preferably from about 2: 1 to about 25: 1, more preferably from about 3: 1 to about 15: 1, for example about 6 or 7: 1, in particular about 6.5: 1.

[0064] The C/S ratio may also be expressed in molar terms (and it will be noted that H2S is not necessarily the sulfurous feedstock). The molar ratio C/S is preferably around 10: 1 to about 0.05: 1, for instance from about 5: 1 to about 0.05: 1 or from about 2: 1 to about 0.05: 1, or from about 1 : 1 to about 0.05: 1. A molar ratio of from about 0.2: 1 to about 0.01 : 1 or from about 0.17: 1 to about 0.1 : 1 may sometimes be desirable.

[0065] The ratio of C/S can have important consequences in the process of the invention - for example when the bioreactor is charged with a consortia of microbiological organisms, the selection of C/S ratio will cause some of those organisms to respond preferentially, thereby impacting the nature of the end product. For example, when the end product is biomass - and it is desired to produce biomass with high lipid content - the C/S ratio may be selected accordingly to favor those microorganisms which yield the desired biomass compositional characteristic.

[0066] There are various types of commercially available gas contactors or absorption columns known in the art. The gas contactor or absorption column suitable for use in the present invention may be dependent on the composition of the inlet fluid stream. Known commercially available contactors my include, but are not limited to, absorption columns with unstructured packing, absorption columns with structured packing or absorption columns with trays.

[0067] The packing of the gas contactor or absorption columns or trays utilized are specifically designs to improve gas and/or liquid mass transfer. Such designs are known and can be found, for example from Perry's Chemical Engineers' Handbook. New York: McGraw- Hill, 1984.

[0068] The raw feedstock may be pre-supplied to such a gas contactor or absorption column before entering the bioreactor. The gas contactor or absorption column and the bioreactor may therefore be provided as separate zones. Alternatively, the gas contactor or absorption column and bioreactor may be provided as a single hybrid zone. In this case, it will be understood that in the process of the present invention the gas contactor or absorption column and the bioreactor may be a single vessel, for example a tubular plug flow reactor. In this case, the recycle stream would be fed directly into the bioreactor in addition to the fluid stream comprising carbon dioxide and hydrogen sulfide.

[0069] The raw feedstock may be treated within the gas contactor or absorption column to produce a carbon-rich feedstock liquid (the reagent stream comprising dissolved or absorbed inorganic carbon) and an off-gas substantially free of carbon dioxide. For example the gas contactor or absorption column may be configured to absorb carbon dioxide from the raw feedstock (for example, ambient air, flue gas or any other process gas stream containing CO2) to produce a concentrated carbon liquid stream (as reagent stream) and an off-gas substantially free of carbon dioxide.

[0070] The off-gas substantially free from carbon dioxide may be utilized in any commonly known process. For example, the off-gas free from carbon dioxide may be used in processes such as hot air regeneration of adsorbents or used as a compressed air feed.

[0071] The raw feedstock may optionally be fed through a pressure booster prior to entering the gas contactor or absorption column and/or the bioreactor. Optionally the raw feedstock may be pre-treated prior to entering the process, for example by clean-up or concentration. [0072] The raw carbonaceous feedstock may comprise up to about 100% v/v carbon dioxide, but may comprise various other materials, such as are typically found in industrial effluents, flue gases, off-gases and/or ambient air.

[0073] The raw sulfurous feedstock may comprise up to about 100% v/v H2S, but may comprise various other materials, such as are typically found in industrial effluents, flue gases and/or off-gases.

[0074] The amount of carbon dioxide may be balanced mainly by nitrogen, water and oxygen. Additional trace amounts of SOx, NOx, H2S, particulate matter, CO and other compounds typically present in industrial gas, petrochemical, or other heavy industrial operations may be present.

[0075] The microbial broth comprises a solvent selected from at least one of amine, alkaline solution (for example, sodium hydroxide or potassium hydroxide), using wastewater for bioremediation of organic stream, ammonia and/or enzyme (for example, carbonic anhydrase) .

[0076] The inventors have found that such an environment in the bioreactor provides a controlled environment that achieves optimal microbial growth.

[0077] In embodiments of the invention, microbiological oxidation of a sulfurous feedstock may be effected by sulfur oxidising microorganisms, including bacteria, archaea, fungus or the like. The sulfur oxidizing bacteria (SOB) can be found in prior art descriptions or may be identified by those skilled in the art using routine screening approaches. Examples of sulfur oxidising bacteria include those belonging to the family Ectothiorhodospiraceae and / or the genera Natronohydrobacter (e.g. Natronohydrobacter thiooxidans), Thiomicrospira, (e.g. Thiomicrospira cyclica), Thioalbus, Bradyrhizobum, Beggiatoa, Thioalkalimicrobium, Acidithiobacillus (e.g. Acidithiobacillus thiooxidans), Thiomonas, Thioalkalivibrio, Thiobacillus, Alkalilimnicola, Guyparkeria, Halomonas, Alkali spirillum, Vibrio, Thiomicrospira, Guyparkeria, Thioalkalispira (formerly Thioalkalimicrobium), Ectothiorhodospiraceae, Rhodobacteraceae, Roseinatrobacter, Alkalilimnicola, Guyparkeria, Desulfuromusa, Desulfuri spirillum. Exemplary species and certain strains are identified in Table 1 below.

[0078] In some embodiments, the process uses a single strain of a sulfur oxidising microorganism to microbially oxidate a sulfurous feedstock. In other embodiments, a consortium of microorganisms may be employed, optionally comprising 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more microorganisms. In some embodiments, the consortium of microorganisms may comprise 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more microorganisms belonging to the genera detailed above.

[0079] The bio-product composition or conversion efficiency may be optionally improved through genetic engineering and enhanced reactor design.

[0080] The biological means used in the present invention may be dependent on the final bio-product.

[0081] The bioreactor conditions may be controlled through in-line monitoring to determine the C/S ratio and carbon speciation. This information can be used to optimize the operating pH and gas flow rates to maximize CO2 capture and system performance.

[0082] The nutrient supply to the process of the invention is controlled to maximise bio-product formation. Preferably the nutrient supply to the bioreactor is above 2mg(N)/l and/or 2mg(P)/l, preferably above 2.5, more preferably above 3 mg(N or P)/l, and is manipulated to maximise the amount of bio-product (e.g. biomass) produced. This nutrient concentration is typically higher than is conventional in current bio-desulfurisation technology - in fact, in such conventional technology the nutrient supply is deliberately maintained below these ranges.

[0083] The process of the invention yields one or more bio-products, such as biomass, PHA/B, 1,4-butanediol, amongst others, with desirably high lipid, carbohydrate and/or protein contents. In one aspect, the process may be adapted to preferentially to produce lipids in preference to protein and carbohydrates. This may be achieved by operating the bioreactor in a time-limited nutrient starved environment (i.e. with low N or P bioavailability) in order temporarily to stress the microorganisms and encourage lipid production.

[0084] It may also be desirable to limit the amount of oxygen supplied to the bioreactor in order to avoid the formation of sulfur dioxide. Running the bioreactor “oxygenlean” in this way helps maximise elemental sulfur production by the sulfur oxidising bacteria.

[0085] Advantageously, the process according to the present invention can be used to produce biomass with different characteristics.

[0086] When the one or more bio-products comprises biomass, it may in some circumstances be desirable to maximise lipid content - in which case the biomass may comprise at least about 40%w/w lipid content, for example at least about 50%w/w lipid content, e.g. 60%w/w or 70%w/w lipid content. [0087] Alternatively, where for example PHA/PHB or BDO is targeted as the end product the lipid content may be lower - for example 40%w/w or less, for instance 30%w/w or less.

[0088] The one or more bio-products produced from the process according to the present invention may be used, by way of non-limiting example, as an energy source, a final product, an intermediate product in a different process, or a carbon storage medium. Preferable end uses may be dependent on the product composition. In the instance that the one or more bio-products is biomass with a high lipid content will be desirable for biofuel production, such as biodiesel. Conversely, high carbohydrate content is more favourable for production of ethanol, and high protein biomass is suited for the production of protein supplements for agricultural feed or nutraceuticals.

[0089] In one embodiment, there may be a method of separating the reduced elemental sulfur from biomass. Depending on the location and end product, this may include centrifugation, solvent extraction, hydro cyclone, or any other separation method known in the art.

[0090] In another embodiment, once the sulfur is extracted and the target molecules removed from the one or more bio-products, there will be a portion of waste biomass or biomass debris. This debris can be used as a feed into anaerobic digester for biogas generation. The debris can also be utilized to feed a secondary bioreactor. The secondary bioreactor can optionally be a reactor with sulfate reducing bacteria (SRBs) which may produce H2S to be fed back into the first reactor to improve carbon capture. This will be useful where sites are lacking sufficient H2S for complete carbon capture. This second reactor may also be specifically designed to produce a number of other biologic chemicals, such as PHA/B, 1,4-butanediol, or other.

[0091] According to a second aspect of the present invention there is provided apparatus for the conversion of CO2 into one or more bio-products, in which the energy required for the microbiological conversion is at least partially provided by the concomitant microbiological oxidation of a sulfurous feedstock.

[0092] The apparatus may comprise: i. means for contacting raw carbon dioxide and sulfur-containing feedstocks, either separately or in combination with an absorption or dissolution medium to form a reagent stream comprising dissolved or absorbed inorganic carbon and sulfur; and ii. means for contacting at least a portion of the reagent stream with a microbial broth in a bioreactor to oxidize sulfur and produce one or more bio-products from the carbon dioxide.

[0093] The means for contacting the raw carbon dioxide and sulfur-containing feedstocks may be provided by one or more fluid contactors.

[0094] The apparatus may comprise:

[0095] iii. means for separating the one or more bio-products into one or more bio-products and a liquid stream; and

[0096] iv. means for recycling at least a portion of the liquid stream to component i. of the apparatus for use as, or part of, the absorption or dissolution medium.

[0097] Means may be provided for the pH of the absorption or dissolution medium to be controlled to facilitate its capacity to absorb or dissolve carbon dioxide and to contribute to reaction conditions in the bioreactor conducive to production of the one or more bioproducts.

[0098] The apparatus according to the present invention may further comprise at least one further gas contactor or absorption column to concentrate the fluid stream with high carbon content, and/or a second bioreactor for producing H2S to be recycled and improve carbon capture.

[0099] The process according to the present invention may optionally further comprise at least one downstream process.

[0100] The downstream process may comprise a process that produces a gas comprising carbon dioxide, for example a biofuels production process.

[0101] The downstream process may comprise a process that converts elemental sulfur into a useful end product such as a fertiliser or commodity chemical.

[0102] By-products or products from the downstream process may advantageously be recycled and used in the process according to the present invention, thereby improving the environmental impact of the overall process and reducing the need for the introduction of external means.

[0103] The following examples are offered by way of illustration of certain embodiments of aspects of the application herein. None of the examples should be considered limiting on the scope of the application. EXAMPLES

[0104] In the process of the invention schematically represented by Figure 1 the feedstock gas comprising CO2 and H2S is supplied in line 201 at atmospheric pressure to a pressure booster 10 which increases the pressure of the feedstock gas to an extent so the flue gas overcomes hydraulic head in gas contactor 11. Pressurized gas passes through line 202 to gas contactor 11, which is also supplied by line 203 with a liquid recycle stream from the process, in combination with make-up water from line 204. In gas contactor 11, CO2 and H2S in the feedstock stream is dissolved in the liquid recycle stream and is supplied on in line 205 to bioreactor 12. A substantially carbon dioxide free and hydrogen sulfide free off-gas is vented in line 206.

[0105] Stream B in line 205 enters bioreactor 12 charged with a microbial broth and maintained under conditions of temperature/pressure/pH effective to ensure consumption by the microbial broth of the stream B to generate a biomass product and a liquid vehicle. Bioreactor 12 is supplied with air (oxygen) through line 207. The one or more bio-products and a liquid vehicle are supplied on in line 209 to biomass separator 13, and vent gas leaves the bioreactor through line 208. The biomass separator 13 separates the one or more bioproducts, which is removed through line 210, and a recycle stream A which is recycled to gas contactor 11 in line 203 after combination with make-up water in line 204.

[0106] The fluid feedstock stream supplied in line 201 is (in this example) flue gas from a chemical plant - but other sources such as power plant or other industrial process could be used.

[0107] The feedstock gas is supplied in line 201 at atmospheric pressure to a pressure booster 10 which increases the pressure of the feedstock gas to an extent so the flue gas overcomes hydraulic head in gas contactor 11. Gas contactor 11 is supplied in line 203 with a liquid recycle stream from the process, in combination with make-up water from line 204.

[0108] In gas contactor 11 carbon dioxide and H2S in the feedstock stream are dissolved in the alkaline liquid recycle stream and supplied on in line 205 to bioreactor 12. A substantially carbon dioxide-free and hydrogen sulfide-free off-gas is vented in line 206.

[0109] Stream B in line 205 enters bioreactor 12 charged with a microbial broth and maintained under conditions of temperature/pressure/pH effective to ensure consumption by the microbial broth of the stream B to generate one or more bio-products and a liquid vehicle. Both are supplied on in line 207 to biomass separator 13, from which is recovered in line one or more bio-products and, in line 208, a recycle stream A which is recycled to gas contactor 11 in line 203 after combination with make-up water in line 204.

EXAMPLE 1

[0110] In the process of the invention schematically represented by Figure 2 the feedstock gas comprising CO2 is supplied in line 301 at atmospheric pressure to a pressure booster 10 which increases the pressure of the feedstock gas to an extent so the flue gas overcomes hydraulic head in gas contactor 11. Pressurized gas passes through line 302 to gas contactor 11, which is also supplied by line 303 with a liquid recycle stream from the process, in combination with make-up water from line 304. The gas contactor or absorption column is also supplied with a separate stream containing H2S from line 305. In gas contactor 11, CO2 and H2S are dissolved in the liquid recycle stream and is supplied on in line 307 to bioreactor 12. A substantially carbon dioxide free and hydrogen sulfide free off-gas is vented in line 306.

[0111] The fluid feedstock stream supplied in line 301 is (in this example) flue gas from a chemical plant - but other sources such as power plant or other industrial process could be used.

[0112] The fluid feedstock stream supplied in line 305 is (in this example) an H2S stream - but other sources such as chemical or power plant or other industrial process could be used.

[0113] Stream B in line 307 enters bioreactor 12 charged with a microbial broth and maintained under conditions of temperature/pressure/pH effective to ensure consumption by the microbial broth of the stream B to generate a biomass product and a liquid vehicle. Bioreactor 12 is supplied with air (oxygen) through line 308. The one or more bio-products and a liquid vehicle are supplied on in line 310 to biomass separator 13, and vent gas leaves the bioreactor through line 309. The biomass separator 13 separates the one or more bioproducts, which is removed through line 311, and a recycle stream A which is recycled to gas contactor 11 in line 303 after combination with make-up water in line 304.

EXAMPLE 2

[0114] In the process of the invention schematically represented in Figure 2 a carbon containing feedstock stream (flue gas) and an EES feedstock stream (EES gas) are supplied to a Gas contactor 11.

The composition of the Flue gas is as follows:

[0115] The flue gas may be supplied at atmospheric pressure or elevated pressure. If supplied at atmospheric pressure, a pressure booster may be used to increase pressure of the flue gas to overcome hydraulic head in gas contactor 11. Gas contactor 11 is also supplied by H2S containing stream. Gas contactor 11 is also supplied a liquid recycle stream from the process. In gas contactor 11 carbon dioxide and hydrogen sulfide are dissolved into the liquid stream and supplied to bioreactor 12. A substantially carbon dioxide free and hydrogen sulfide free off gas is vented as off gas.

The composition of the H2S containing stream is as follows:

The composition of the liquid stream fed into bioreactor 12 (adjusted to pH 9-10*) is as follows:

*With reference to the liquid stream fed into the bioreactor, there is a need to balance the optimum pH to ensure that there is enough bicarbonate in the process to feed microbes in the bioreactor, but also for optimal carbon dioxide adsorption. This aspect of the invention is further referenced in Example 3 below. The composition of the off gas vented from gas contactor 11 is as follows:

[0116] Bioreactor 12 is fed with the liquid stream from gas contactor 11 and with compressed air as an oxygen source.

[0117] Bioreactor 12 is charged with a microbial broth and maintained under conditions of temperature/pressure/pH effective to ensure consumption by the microbial broth of the liquid stream fed from gas contactor 11 to generate a sulfur-containing biomass product and a liquid vehicle. The sulfur-containing biomass and the liquid vehicle are supplied to Biomass Separator 13. A concentrated sulfur-containing biomass and a substantially biomass- free liquid are produced. The biomass-free liquid is returned pH adjusted to from 9-10 to the gas contactor 11 via line 303. In some embodiments, the concentrated sulfur-containing biomass can be processed further to separate elemental sulfur from the biomass. In other embodiments, the concentrated sulfur-containing biomass is used directly as a feedstock for further bioreactors.

[0118] In certain embodiments, the bioreactor 12 operating parameters are optimized to promote biomass growth. In other embodiments, the bioreactor operating parameters are optimized to promote lipid buildup. In still more embodiments, the bioreactor operating parameters are optimized to promote carbohydrate accumulation

[0119] The above described flue gas and H2S containing gas stream can be processed according to the invention substantially to remove the hydrogen sulfide and capture the carbon dioxide.

[0120] In the process of the invention schematically represented by Figure 3 elemental sulfur product from the process of the invention is recycled via an H2S bioreactor to provide a sulfurous stream for the process of the invention.

[0121] Flue gas is supplied to CO2 absorber 20 through line 401. In CO2 absorber 20 the carbon dioxide is absorbed by a recycled liquid stream, passing through line 402 to a H2S absorber 21. H2S absorber 21 is also supplied by a stream 403 from H2S bioreactor 22. In H2S absorber 21, the hydrogen sulfide is absorbed into the recycled liquid stream. [0122] The fluid feedstock stream supplied in line 401 is (in this example) flue gas from a chemical plant - but other sources such as power plant or other industrial process could be used.

[0123] The feedstock gas may be supplied at atmospheric pressure or elevated pressure. If supplied at atmospheric pressure, a pressure booster may be used to increase pressure of the sour gas to overcome hydraulic head in gas absorber 20.

[0124] The carbon and sulfur containing reagent stream passes from through line 404 to aerobic bioreactor 23 charged with a microbial broth and maintained under conditions of temperature/pressure/pH effective to ensure consumption by the microbial broth of the stream to generate one or more bio-products and a liquid vehicle. Bioreactor 23 is supplied with nutrients, sodium hydroxide and water through line 406, which also contains recycled liquid vehicle. The one or more bio-products and a liquid vehicle are supplied on in line 407 to settler 24, from which is recovered one or more bio-products. In line 408, a recycle stream of CO2 is recycled to CO2 absorber 20.

[0125] The mixture of one or more bio-products and a liquid vehicle pass from settler 24 through line 409, firstly to centrifuge 25, which is operated under conditions to separate elemental sulfur through line 411. The substantially sulfur-free product mixture passes from centrifuge 25, through line 410, to centrifuge 26, which operates under conditions to separate the bio-products from the liquid vehicle. The desired bioproduct is collected through line 412 and the recycled liquid vehicle is removed through line 406 and recycled to the aerobic bioreactor, being combined with nutrients, sodium hydroxide and water supplied through line 413. Ableed outlet 414 is also present to allow the removal of excess liquid vehicle.

[0126] The sulfur removed through line 411 is provided to H2S bioreactor 22, which is also supplied with biomass debris from line 415. H2S bioreactor is charged with sulfate reducing bacteria producing a stream of H2S that is fed back into the H2S absorber 21 through line 403 to improve carbon capture.

[0127] For the avoidance of doubt, all features relating to process for sequestering carbon dioxide also relate, where appropriate to the apparatus for sequestering carbon dioxide and vice versa. EXAMPLE 3

[0128] Microorganisms identified as candidates for the described process are set out in Table 1, each proprietary strain (Isolate ID) having 16S homology with the commercially available strain as indicated:

Table 1

[0129] 1000 liters of exemplificatory feedstock media were prepared according to the concentrations set out in Table 2:

Table 2 - exemplificatory feedstock media - composition

[0130] In the above table, thiosulfate is used as the electron donor as an analogue for H2S for experimental safety reasons. Once prepared, 800L of the media was charged into a stirred tank bioreactor with micro aeration sparged with air. Inoculant containing a consortia containing strains identified (by greatest % 16S sequence identity) as belonging to the Ectothiorhodospiraceae family (the consortia identified as Cem561 in Example 4 below) was charged to the reactor such that the final optical density of the bioreactor at 600nm was 0.1. The pH inside the reactor was maintained from 9-10 and the reactor temperature was maintained at 100°F (37.78°C). On Day 3 of the experiment, the bioreactor was charged with additional thiosulfate.

[0131] During the growth of the microbes, the thiosulfate concentration and sulfate concentration was monitored as was the total suspended solids (TSS). The measurement of TSS can be used as in indirect measurement of microbial productivity. As shown in Figure 4 below, the addition of thiosulfate on Day 3 corresponds to an increase in thiosulfate concentration, followed by rapid increase in the microbial growth, as evidenced by the increase in TSS. As the thiosulfate is oxidized, an increase in sulfate concentration is also shown. As the concentration of thiosulfate reduces to zero, microbial death is observed as a decrease in TSS.

[0132] Also during the growth of the microbes, the reactor pH was monitored. The results are graphically represented in Figure 5 which shows that the maximum productivity, as measured by TSS, occurs at a pH of from 9 to 10, with its peak at pH~9.4.

EXAMPLE 4 - Recycle stream pH Control

[0133] The plant of Figure 1 was configured to control the pH of the recycle stream by coupling the pH control with a biomass dewatering step. Effluent from the bioreactor is passed to a filtration unit (not shown). Before filtration, additional CO2 is injected into the effluent steam. After filtration, pressure is released from the recycle stream, resulting in a slight increase in pH. The resulting stream is passed on in line 203 to gas contactor 11. Modelled results are shown in Table 3 below. The pH of the effluent stream is raised from 9.5 to 9.9 in the process. Further adjustment of recycle stream pH may be effected by the provision of alkaline make-up in line 204. Table 3 - modelled data

EXAMPLE 5

Growing conditions and OD measurement

[0134] The Cem561 consortium was grown to a maximum density of 0.26 g/L on a mixture of Sodium thiosulfate and sodium bicarbonate sole source of energy and carbon for growth.

[0135] The following protocol was followed for experiments performed using a continuous-flow stirred-tank bioreactor.

Apparatus:

[0136] Culture was grown in continuous-flow mode in an Eppendorf IL glass fermenter with Eppendorf Biofl o 115 controller for controlling the temperature and pH. pH was maintained between 9-10 with continuous addition of fresh culture medium prepared to maintain this pH as described in Table 2 above.

[0137] A combination of Rushton impeller at 200 RPM and continuous liquid recycle were used for mixing. Recycle was withdrawn from the bottom of the liquid section of the reactor and returned to the headspace. Air was supplied at a flow rate of 240 ml/min using a mass-flow controller (Alicat Scientific MC500SCCM). Liquid medium was supplied at a rate of approximately 36 ml/hr using a peristaltic pump (Watson-Marlow 120U) and culture was constantly removed from the reactor through a dip-tube to maintain a constant volume of 240 ml. The weight of the media reservoir was continuously monitored using a balance (Ohaus MB90) connected to the computer to calculate the exact flow rate. The culture from the reactor outlet was collected twice daily for biomass measurement.

Medium: [0138] The medium used for this experiment was based on DSMZ 925 medium (www.dsmz.de) with the concentrations of sodium thiosulfate, potassium nitrate and trace elements modified.

Autotrophic inoculum:

[0139] Cem561 inoculum was taken from culture grown on thiosulfate and bicarbonate.. The flasks were incubated at 30°C and 200 RPM. The inoculum had an OD ~0.3. The fermenter was inoculated to give an initial OD -0.03. In other words, the culture was diluted in the bioreactor at a 1 : 10 ratio. Inoculum was transferred from flask to the bioreactor using a 60 mL syringe. After inoculation, an initial OD was taken. Generally, all OD measurements were performed with a Thermo Scientific UV/Vis spectrophotometer.

[0140] Figure 6 gives an example of the cell density, thiosulfate and sulfate concentrations over the course of about 400 hours. These data demonstrate the maintenance of steady state production of biomass over time in a continuous flow type reactor.

[0141] The above description is for the purpose of teaching the person of ordinary skill in the art how to practice the object of the present application, and it is not intended to detail all those obvious modifications and variations of it which will become apparent to the skilled worker upon reading the description. It is intended, however, that all such obvious modifications and variations be included within the scope of the present application, which is defined by the following claims. The aspects and embodiments are intended to cover the components and steps in any sequence, which is effective to meet the objectives there intended, unless the context specifically indicates the contrary.