Carbon sequestration using fiber contactors

Abstract

A method and system for carbon sequestration includes using an immobilized carbonic anhydrase enzyme fiber contactor to catalytically sequester CO2 from a CO2-containing fluid in an aqueous sorbent. The sequestration product may include soluble bicarbonates, insoluble carbonates, or a combination thereof, which may be used as a raw material in other applications or may be a permanent sequestration medium.

Description

CARBON SEQUESTRATION USING FIBER CONTACTORSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims benefit of priority to United States Provisional Patent Application No. 63 / 783,309 filed April 4, 2025, entitled “Carbon Sequestration Using Fiber Contactors And Saline Aquifers,” and United States Provisional Patent Application No.63 / 763,637 filed February' 26, 2025, entitled “Carbon Sequestration Using Immobilized Carbonic Anhydrase, Metal Salts, and the Formation of Bicarbonates,” the disclosures of each of which are hereby incorporated by reference in their entireties.TECHNICAL FIELD OF THE DISCLOSURE

[0002] The present disclosure generally relates to carbon sequestration utilizing a fiber contactor.BACKGROUND OF THE DISCLOSURE

[0003] As the global community strives to meet ambitious climate goals, carbon dioxide (CO?) emissions from industrial fermentation processes continue to present a significant environmental challenge. Yeast fermentors, widely used in industries such as biofuel production, brewing, and pharmaceutical manufacturing, release large quantities of CO2 as a byproduct of the fermentation of sugars. The CO2 emitted during fermentation is ty pically vented into the atmosphere, contributing to the growing problem of climate change.

[0004] Current CO2 capture technologies, while effective, face limitations in terms of scalability, cost-effectiveness, and long-term efficiency. There is a need for innovative solutions that can not only capture CO2 but also transform it into stable, environmentally benign forms.

[0005] The current state of the art for post-combustion carbon dioxide (CO2) capture encompasses various technologies aimed at reducing CO2 emissions from sources such as power plants, industrial processes, and biofuel production. Post-combustion capture ty pically utilizes solvents, solid sorbents, or membrane technologies to separate CO2 from flue gases produced during the combustion of fossil fuels or biomass. In the context of ethanol fermenters, CO2 is a natural byproduct of the fermentation process, and existing systems capture this CO2 for use in applications like enhanced oil recovery (EOR), agricultural greenhouse enrichment, or underground storage. Direct air capture (DAC) is an emerging technology that extracts CO2 directly from the atmosphere using chemical processes or solid sorbents, providing a potential solution to reduce atmospheric CO2 concentrations. Once captured, CO2 is often compressedto a near supercritical state (e g., 1300 psig is common) with significant energy required to do so and then transported to deep geological formations, such as depleted oil and gas reservoirs or saline aquifers, for permanent underground storage. However, the viability of using saline aquifers for CO2 storage is contingent on the presence of a stable bedrock cap, which acts as a seal to prevent high pressure CO2 from migrating upward and re-entering the atmosphere. This requirement limits the number of suitable underground storage sites, as not all aquifers possess the necessary geological characteristics, such as impermeable caprock, to safely contain CO2 over the long term. Consequently, while carbon capture and storage (CCS) technologies hold significant potential, the availability of suitable underground storage sites remains a limiting factor, driving ongoing research to identify and develop new storage locations and improve monitoring techniques for long-term storage integrity.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The following figures illustrate embodiments of the subject matter disclosed herein. The claimed subject matter may be understood by reference to the following description taken in conjunction with the accompanying figures, in which:

[0007] FIG. 1 is a diagrammatic illustration of a fiber contactor according to an embodiment of the present disclosure.

[0008] FIG. 2 is a diagrammatic illustration of a system according to an embodiment of the present disclosure.

[0009] FIG. 3 is a diagrammatic illustration of a testing apparatus used in the Examples.

[0010] FIG. 4 is a graph of results from the Examples.

[0011] FIG. 5 is a graph of results from the Examples.

[0012] FIG. 6 is a graph of results from the Examples.

[0013] FIG. 7 is a graph of results from the Examples.DETAILED DESCRIPTION

[0014] The following disclosure provides many different embodiments or examples. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and / or letters in the various examples. This repetition is for the purpose of simplicity and clarify and does not in itself dictate a relationship between the various embodiments and / or configurations discussed.

[0015] The present disclosure provides a novel approach for CO2 sequestration by utilizing immobilized carbonic anhydrase (CA), metal salts, and the formation of insoluble carbonates in an industrial-scale process. In this process, carbonic anhydrase, which catalyzes the conversion of CO2 to bicarbonate ions, is immobilized on stainless steel fibers using silane cross-linkers within a fiber reactor. This system can efficiently capture CO2 from fermentation and convert it into a bicarbonate, such as sodium bicarbonate (NaHCOs), offering an effective and scalable solution for CO2 sequestration. Alternatively, this system can efficiently capture CO2 from fermentation and convert it into solid carbonates, such as calcium carbonate (CaCOs). Described herein is a process of appending an enzymatic fiber reactor immediately following the CO2 water scrubber at fermentation plants. Enzy matic fiber reactors have previously been described in WO 2024 / 151924, which is incorporated by reference herein in its entirety.

[0016] The present disclosure provides a system and method for capturing CO2 produced by, e g., yeast fermentors in an industrial setting by using immobilized carbonic anhydrase to catalyze the conversion of CO2 into bicarbonate followed by the subsequent trapping of CO2 as water soluble bicarbonates or as water insoluble carbonates created by the addition of metal salts. In some embodiments, the trapping of CO2 as water soluble bicarbonates provides advantages over creation of carbonates because only one of the acidic hydrogens in carbonic acid needs to be neutralized, reducing the alkaline ingredient cost of the chemical reaction. Another advantage is the lower cost and removal of unwanted CO2 emissions. In particular, calcium carbonate needs to be made from a calcium source. Sources of calcium are expensive and often made by stripping CO2 off from calcium carbonate to form a reactive calcium species. For carbon sequestration, the source of calcium will often be a difficult problem to solve. Bicarbonates need a counter cation to react with the bicarbonate anion. There are many sources of such cations that are readily available, and their manufacture does not produce CO2. Sodium chloride is a commonly available salt present in seawater and deep ground saline aquifers. Calcium carbonate and magnesium carbonate are ubiquitous in the environment.

[0017] The present disclosure further provides a system and method wherein certain chemistries are performed in a fiber contactor above ground while other chemistries described herein are available for carbon sequestration by returning carbonic acid and reacted chemistries back into either a saline aquifer or ocean by way of an above ground reactor complex.

[0018] The systems described herein may include a fiber reactor housing fibers to which carbonic anhydrase is covalently bound via silane cross-linkers. As an example, with reference to FIG. 1. the present disclosure provides a fiber contactor 100 (hereinafter an “immobilized enzyme fiber contactor’7or “IEFC”) having internal elements 120 thereof (e.g., fibers) containing immobilized enzymes. The IEFC 100 includes a hollow conduit 110 housing a plurality of the fibers 120. In some embodiments, the fibers 120 may be formed of steel, such as stainless steel or a steel composite. In other embodiments, the fibers 120 may be formed of basalt, ceramics, glass, polymers, and / or metals. The fibers 120 may extend an entire length of the conduit 110 or a portion thereof, or may extend beyond the conduit 110 into a separator 112, as shown in FIG. 2. In some embodiments, the fibers 120 may be packed into the conduit 110 at a nominal rate of less than 40%, less than 30%, less than 25%, less than 20%, 5 to 30%, about 15%, or about 25%. The IEFC 100 may include one or more inlets 132, 142 for introduction of fluids (gas and / or liquid reactants) and one or more outlets 134, 144 for removal of reaction product(s).

[0019] In some embodiments, the fibers 120 have a diameter of 1 to 500 microns, less than 200 microns, less than 150 microns, less than 100 microns, less than 75 microns, 5 to 200 microns, 5 to 150 microns, 5 to 100 microns. 5 to 75 microns. 10 to 200 microns, 10 to 150 microns, 10 to 100 microns, 10 to 75 microns, 15 to 200 microns, 15 to 150 microns, 15 to 100 microns, 15 to 75 microns, 15 to 30 microns, 20 to 25 microns, 30 to 70 microns, 40 to 60 microns, about 20 microns, or about 50 microns.

[0020] In some embodiments, one of the inlets 132. 142 may be positioned at a lower portion of the conduit 110 to allow for countercurrent flow of the reactants. For example, the inlet 132 may be positioned as shown in FIG. 1 to introduce an aqueous solution into the conduit 110 and the inlet 142 may be positioned along the conduit 110 near the separator 112 to introduce a gas into the conduit. In such embodiments, one of the outlets 134, 144 may be positioned at the top of the conduit 110 to remove the treated gas. As another example, the inlets may be 132 and 144 and the outlets may be 142 and 134 shown in FIG. 1. Further details of the IEFC 100 may include those disclosed in WO 2024 / 151924 referenced above.

[0021] Carbonic anhydrase (CA) is an enzyme that catalyzes the conversion of CO2 into bicarbonate ions (HCOs ). In the systems disclosed herein, the enzyme (CA) is immobilized on the fibers 120, ensuring a stable and reusable enzyme source. The immobilization process involves the use of silane cross-linkers, such as 3-aminopropyltriethoxysilane (APTES), which covalently bond CA to the surface of the fibers120, allowing for efficient and prolonged enzyme activity in the reactor environment. The fibers 120 serve as a support matrix, maximizing the surface area available for the enzy me and facilitating continuous CO2 capture from a CCE-rich fluid.

[0022] Once immobilized on the fibers 120, CA accelerates the conversion of CO2 into bicarbonate ions (HCCh ) in solution according to the following Reaction 1:Reaction 1The CO2 is absorbed into the IEFC 100, where the enzyme (CA) catalyzes the transformation of gaseous CO2 into aqueous bicarbonate which will be collected as condensate.

[0023] The design of the IEFC 100 maximizes contact between the enzyme and the CCE-rich fluid, improving the efficiency of the CO2 conversion process while greatly reducing the back pressure experienced by other packed bed systems that would seek to utilize an immobilized enzyme strategy. In some embodiments, the CCE-rich fluid is a CCE-rich gas wherein CO2 from a fermentor or other process may be, e.g., treated by an industrial water scrubber to yield the CCE-rich gas. In other embodiments, the CCE-rich fluid is a CCE-rich liquid wherein CO2 from a fermentor or other process can be dissolved in water or other suitable solvent.

[0024] In some embodiments, the CCE-rich fluid is contacted with water (as a sorbent solution or aqueous sorbent) within the IEFC 100 to form a bicarbonate ion (HCOs ) rich condensate. In some such embodiments, the bicarbonate ion (HCCE ) rich condensate may be collected in a secondary vessel and reacted with metal salts, such as sodium chloride (NaCl), calcium carbonate (CaCCE), magnesium carbonate (MgCCE), an alkali metal salt, or a mixture of salts to form bicarbonate salts, e.g., as shown in Reaction 2 and Reaction 3 below.

[0025] Formation of calcium bicarbonate:CaCO3(s) + HCCE Ca2++ 2HCO3' Reaction 2

[0026] Formation of sodium bicarbonate:NaCl + HCO3 —>■ NaHCCE + Cl’ Reaction 3

[0027] In both of these examples the product is reasonably water soluble. The soluble bicarbonates (such as NaHCOs) may be evaporated to dryness and used in common applications utilizing those compounds, such as food applications or as a raw material in other chemical processes. Alternatively, the bicarbonates can be used as a permanent sequestration compound for CO2. In this regard, options include, but are not limited to, deep well injection or drying and above ground storage. For deep well injection, suitable wells do not need strong cap rocks, such as required for direct compressed CO2 injection because the bicarbonatesolution is not a compressible gas. For evaporation to dryness and permanent above ground storage, the storage site should be protected from moisture to avoid dissolving the salt and releasing it into the groundwater. Standard land fill applications already have suitable protection from water intrusion and could be used for this service.

[0028] To understand the potential for CO2 sequestration at an industrial scale, consider the following example for a bioethanol plant:

[0029] Assumption 1: A large bioethanol plant with a fermentation capacity of 1,400,000 liters of ethanol per day produces approximately 1.050 metric tons (MT) of CO2 daily as a byproduct of fermentation.

[0030] Assumption 2: Carbonic anhydrase in the fiber reactor system can capture up to 90% of the CO2 from the plumb gas stream.

[0031] Assumption 3: For every MT of CO2 captured, approximately 1.91 MT of NaHCCh can be produced (based on stoichiometric calculations).

[0032] Therefore, with 1,050 MT of CO2 captured daily (1,050 MT CO2 x 1.91 x 365 = 732,007 MT NaHCCh annually). This level of sequestration would result in the production of approximately 732,007 MT of sodium bicarbonate per year, which can be used in a variety of commercial applications. More importantly, 383,205 MT of CO2 would be removed from atmospheric emission if the bicarbonate is permanently sequestered, thereby reducing the CO2 concentration in the atmosphere.

[0033] In some embodiments, the bicarbonate ion (HCO3 ) rich condensate may be collected in the secondary vessel and reacted with metal salts, such as calcium chloride (CaCb) or magnesium sulfate (MgSCh), an alkaline earth metal salt, or a mixture of salts to form insoluble carbonates, e.g., as shown in Reaction 4 and Reaction 5 below.

[0034] Formation of calcium carbonate:Ca2+ 2HCO3 CaCO3(s) + CO2 + H2O Reaction 4

[0035] Formation of magnesium carbonate:Mg2++ 2HCO3 MgCO3(s) + CO2+H2O Reaction 5

[0036] In these examples, the insoluble carbonates precipitate out of the solution, trapping the CO2 in a stable, solid form. The solid carbonates (such as CaCCh) can then be separated by a variety of techniques known to those of ordinary skill in the art and used for various applications, including construction, water treatment, and as a raw material in other chemical processes.

[0037] To understand the potential for CO2 sequestration at an industrial scale, consider the following example for a bioethanol plant:

[0038] Using Assumption 1 and Assumption 2 above, for every' MT of CO2 captured, approximately 2.27 MT of CaCOs can be produced (based on stoichiometric calculations).

[0039] Therefore, with 1,050 MT of CO2 captured daily (1,050 MT CO2 x 2.27 x 365 = 881,593 MT CaCCT annually). This level of sequestration would result in the production of approximately 881,593 MT of solid calcium carbonate per year, which can be used in a variety of commercial applications, such as construction materials or water treatment, effectively transforming waste CO2 into a valuable byproduct. More importantly, 383,205 MT of CO2 would be removed from atmospheric emission, thereby reducing the CO2 concentration in the atmosphere.

[0040] In some embodiments, the sorbent solution includes one or more salts dissolved in water. For example, in some embodiments, the sorbent solution is a saline solution from a saline aquifer, or the sorbent solution is ocean or sea water. In some embodiments, the one or more salts may include any of those described above for forming carbonates and / or bicarbonates.

[0041] Turning to FIG. 2, a system 1000 is provided wherein a CO2 source 10 is in communication with a reactor complex 30 and configured to supply CO2 (as the CCF-rich liquid) to the reactor complex 30 via line 12. In some embodiments, the reactor complex 30 may be integral with the CO2 source. In some embodiments, the reactor complex 30 may be separate and the line 12 may include a direct connection (e.g., piping, tubing, valves, etc.), an indirect connection (e.g., the CO2 may be packaged into containers and transported via truck or train), or a combination of these connections.

[0042] In the system 1000, water is drawn from a saline aquifer 20 (via uptake well 22) and plumbed into the reactor complex 30 that contains one or more fiber reactors (such as the IEFC 100 described in FIG. 1) and a water storage tank where adjustments favorable to immobilized carbonic anhydrase can be made. Example adjustments include changing the temperature of the water and / or changing the pH / buffering capacity of the water. The reactor complex 30 may also contain a system that compresses and stores CO2 for inline sequestration uses. In addition, the reactor complex 30 may also encompass equipment to concentrate or dilute the cations relative to the ground water. For example, the water supply may be repurposed by a reverse osmosis (RO) system in which water is provided to the CO2 source 10 and the concentrated discharge becomes the cation feed for carbon sequestration (via line 12).An example for dilution is to add additional fresh water with lower cation concentration to the water from the saline aquifer 20. The dilution or concentration of cations may produce the optimal performance of the specific carbonic anhydrase enzyme immobilized. The source of CO2 is not particularly limited and the present system 1000 may be used with any CO2 source 10 at which carbon dioxide is either generated or concentrated.

[0043] Following sequestration in the one or more fiber reactors (e.g., the IEFC 100), complexes including, but not limited to, carbonic acid, carbonates, and bicarbonates will form relative to the ionic composition of the saline aquifer 20. This discharge may then be returned into the saline aquifer 20 via line 32 and injection well 24. The line 32 may include any of the direct or indirect connections disclosed herein to transport the CCh-containing discharge to the injection well 24 and into the saline aquifer 20. The position of the injection well 24 may be close to the uptake well 22 or may be many miles away from the uptake well 22. In some embodiments, a distance between the uptake well 22 and the injection well 24 (distance measured laterally and / or by respective depths) is sufficient to prevent cross-contamination. In some embodiments, the nature of the saline aquifer 20 may dictate the distance (e.g., permeability and / or formations within the saline aquifer 20). In some embodiments, the saline aquifer 20 used for the uptake well 22 may be distinct and discrete from the saline aquifer (not shown) used for the injection well 24. It is appreciated that in addition to horizontal distance, the well penetrations can be into different vertical distances to avoid processed water from entering the source well.

[0044] It should be noted that multiple geological formations also exist internal to a saline aquifer for which little to no aqueous dissociation takes place. As such, there may be certain aquifers in which it would be beneficial for varying amounts of carbonic acid to be returned into the water table to utilize both the water soluble and water insoluble structures unique to any particular saline aquifer. For example, limestone dissociation increases in the presence of carbonic acid. This event lends to the creation of bicarbonate and the subsequent release of calcium that can in turn form calcium carbonate. Similar dissociation kinetics are known to take place for silicates in which the presence of carbonic acid lends to the formations of novel silicates that sequester carbon dioxide.

[0045] Although the examples provided above have focused on saline aquifers, it should be noted that the processes described herein also extend to coastal regions where access to saline ocean w ater is more readily available.

[0046] Benefits of the process and system disclosed herein over existing approaches manifest themselves in the broadening of available sites for which carbon capture is feasible. The process outlined herein removes the need for an impermeable bedrock overlying the saline aquifer. In doing so. this process removes the current 100-year monitoring mandate placed upon other less available sites that seek to trap gaseous carbon dioxide as opposed to dissolved carbonic acid, carbonates, bicarbonates, and other reactants. Furthermore, the process outlined herein is less energy intensive as it eliminates the need to compress carbon dioxide into a liquid prior to transport into the ground.

[0047] In some embodiments, the system 1000 and process disclosed herein may be used for the capture of CO2 from ethanol fermenters. Ethanol fermenters as the CO2 source 10 may uniquely offer an ideal source of nearly pure CO2. In addition, many of the aquifers underlying ethanol plants in the United States are not suitable for carbon storage given the absence of an impermeable cap rock overlying the aquifer. Thus, converting carbon dioxide into carbonic acid and performing the carbon capture chemistries above ground, and in a liquid context, increases available sites and reduces the pipeline costs necessary for adoption. Furthermore, saline aquifers in these regions contain geological complexes with poor dissociation kinetics as described above. Such repositories have until now been unable to act as a sequestration reservoir as they cannot support gaseous carbon dioxide under high pressure.

[0048] The greatest potential reservoir for carbon dioxide sequestration exists in the world’s oceans. With sodium making up approximately 30% of the dissolved ions in seawater, and an estimated global salt content of 5 * 1019kg, ocean water describes the single largest potential carbon sequestration reservoir in terms of its capacity to produce and solubilize bicarbonate. This resource is virtually unavailable to carbon dioxide unless it is first converted into carbonic acid.

[0049] EXAMPLES

[0050] A series of experiments were conducted to assess the rate of reaction for a fiber reactor system containing either none, free, or immobilized carbonic anhydrase enzyme. The enzyme used for all experiments was commercially available carbonic anhydrase from bovine ery throcytes (available from SIGMA ALDRICH), referred to herein as BCA.

[0051] The fiber reactor system consisted of a 2-ft long column having an internal diameter of 0.5 inches which was packed to a particular density with fiber media. Three different fiber packings were explored. In all cases, the fiber packing consisted of thousands of fibers that extend unbroken from end to end of the column. Three different fiber diameterswere explored including: 203pm, 50pm and 22pm. All fibers were composed of stainless steel. As fiber diameter decreases, overall surface area of the fiber packing increases, which effects the total concentration of BCA enzyme that may be immobilized.

[0052] The testing apparatus (shown in FIG. 3) consisted of the fiber column which has an inlet at the top where a 50mM K2CO3 sorbent solution was allowed to enter and exit at the bottom of the column into a beaker that contained the excess sorbent solution and a pH probe to record pH change over time. The sorbent was recirculated with a peristaltic pump through the column and beaker at 8ml / min. The bottom of the column had an inlet to introduce a CCh / air gas mixture metered by a mass flow controller which flows counter current to the sorbent solution. The top of the column was left open to allow the excess input gasses to outflow. The experiments were conducted at room temperature (23°C±0.5).

[0053] The basis of the experiment relies on the reaction below:CO2+ H2O <-» H2CO3(carbonic acid)H2CO3(carbonic acid) HCO3(bicarbonate) H2- +HCO3(bicarbonate) « CO3(carbonate ion)+ H

[0054] In the present experiments, when the CO2 / air gas mixture entered the column, a portion of the CO2 was converted to carbonic acid. The carbonic anhydrase enzyme catalyzes this reaction. The rate of pH decrease was compared between systems containing BCA and those which do not.

[0055] The three fiber packings were compared at a single flow rate wherein CO2 was 20% of the overall 20 standard cubic centimeters per minute (seem) flow. Additionally, for the 22pm fiber column, a flow rate of 10 seem CO2 / 40 seem air was explored. The total surface area of the 203 pm, 50 pm and 22 pm fiber columns were 6476 cm2, 26,293 cm2and 43,080 cm2, respectively. The theoretical BCA monolayer enzyme loadings on the 203 pm, 50 pm and 22 pm fiber columns were 0.30 mg, 1.23 mg and 1.96 mg, respectively. For all the free BCA comparative experiments, the concentration of enzyme was kept constant at 0.03 mg / ml. In the case of the 203 pm fiber column, a total of 50 ml 50 mM potassium carbonate solution was recirculated through the column and receiving beaker during testing. In the case of the 50 pm and 22 pm fiber columns, a total of 70 ml 50 mM potassium carbonate solution was recirculated. The reason for this increase in sorbent volume for the higher surface area fiber columns was that as a function of increased surface area, the sorbent solution moves more slowly through these columns because of increased surface tension between the liquid and thefiber. Therefore, an extra 20ml of sorbent solution was added to ensure that enough liquid remained in the receiving beaker to keep the pH probe tip submerged during testing. The transit time through the 203 pm, 50 pm and 22 pm fiber columns were approximately 150, 180 and 210 seconds respectively. The enzyme concentrations for the immobilized BCA 203 pm. 50 pm and 22 pm fiber columns during testing were 0.006 mg / ml, 0.017 mg / ml and 0.028 mg / ml respectively. Therefore, the only immobilized column which approached the 0.03 mg / ml BCA enzyme used in the free enzyme experiments was the 22pm fiber column.

[0056] The transit time through the column had a noticeable effect on the performance of the free enzyme relative to the null condition for the 4sccm CO2 16sccm AIR gas flow. For the 203 pm fiber column, the free enzyme pH rate of change was 1.863 times higher than that of the null condition, as show n in FIG. 4 and Table 1 below.

[0057] TABLE 10058] For the 50 pm fiber column, the free enzyme pH rate of change was 1.536 times higher than that of the null condition, as show n in FIG. 5 and Table 2 below.

[0059] TABLE 20060] But for the 22 pm fiber column, the null condition was 1.074 times higher than the free enzy me condition, as shown in FIG. 6 and Table 3 below.

[0061] TABLE 3

[0062] The reason the performance gap lessens at the 4 seem CO2 / 16sccm air gas flow is that as residence time of the sorbent solution in the column before reaching the collection / measurement beaker increases, the null condition is allowed more time to convert CO2 to carbonic acid (a natural process for CO2 in water) and therefore the rate improvement provided by the free BCA enzyme is diminished. However, in the 22 pm fiber column experiment, conducted at higher gas flow rate and increased CO2 (10 seem CO2 / 40 seem air), the free enzyme condition once again outperformed the null condition due to the increase in available reactant (CO2) having a rate 1.209 times that of the null condition, as shown in FIG.7 and Table 4 below.

[0063] TABLE 40064] In the case of the immobilized enzyme for the 203 pm column (FIG. 4), the nul condition was slightly higher than that of the immobilized condition, but they are essentially the same rate which may be explained by the low enzyme concentration of 0.006 mg / ml for the immobilized column (compared to 0.03 mg / ml for the free enzyme). However, when the 50 pm fiber column is assessed (FIG. 5), the immobilized condition now outperforms the null condition -0.004175 versus -0.002843 ApH s'1and is very close to the free enzyme condition -0.004366 ApH s'1. This is consistent with the increase in immobilized enzyme concentration for this experiment at 0.017mg / ml versus 0.03 mg / ml for the free enz me condition.

[0065] This trend continued for the 22pm fiber column experiment at the 4 seem CO2 and 16 seem air gas flow (FIG. 6). In this experiment, the immobilized reactor had a rate of -0.01035 ApH s-1whereas the null achieved -0.006869 ApH s'1and the free enzyme condition at rate reached -0.006395 ApH s'1. The immobilized enzyme concentration was at 0.028mg / ml compared to 0.03mg / ml for the free enzyme concentration, which suggests that the immobilized enzyme reactor is more effective than the free enzyme when tested at similar enzyme concentrations. As the gas flow was increased to 10 seem CO2 and 40sccm air (FIG.7), the immobilized enzy me rate increased to a rate of -0.01224 ApH s'1compared to the null condition with a rate of -0.007673 ApH s'1and the free enzyme condition rate of -0.009277 ApH s'1.

[0066] A method is provided herein. The method includes providing a fiber contactor comprising a conduit having a plurality of fibers disposed therein, wherein the plurality' of fibers comprise a carbonic anhydrase enzyme immobilized on surfaces thereof; and simultaneously introducing an aqueous sorbent and a CCh-containing fluid into the fiber contactor to catalytically sequester CO2 from the CCh-containing fluid in the aqueous sorbent. The method may include any one or more of the following features:

[0067] wherein the aqueous sorbent is water; and wherein catalytically sequestering CO2 from the CCh-containing fluid in the aqueous sorbent forms a bicarbonate ion-containing solution;

[0068] further comprising reacting the bicarbonate ion-containing solution with an alkali metal salt to form a bicarbonate salt solution;

[0069] further comprising drying the bicarbonate salt solution to yield a solid bicarbonate salt;

[0070] further comprising injecting the bicarbonate salt solution into a subterranean well;

[0071] further comprising reacting the bicarbonate ion-containing solution with an alkaline earth metal salt to form a water-insoluble carbonate salt;

[0072] wherein the aqueous sorbent is a saline solution comprising an alkali metal salt, an alkaline earth metal salt, or a combination thereof; and wherein catalytically sequestering CO2 from the CCh-containing fluid in the aqueous sorbent forms an aqueous reaction product comprising a water-soluble bicarbonate salt, a water-insoluble carbonate salt, or a combination thereof;

[0073] wherein the saline solution is from a saline aquifer; and wherein the method further comprises withdrawing the saline solution from the saline aquifer through an uptake well;

[0074] further comprising transferring the aqueous reaction product to the saline aquifer through an injection well, wherein the injection well is laterally spaced from the uptake well;

[0075] further comprising transferring the aqueous reaction product to a second saline aquifer that is isolated from the saline aquifer;

[0076] wherein the saline solution is from a saline body of surface water;

[0077] further comprising transferring the aqueous reaction product to the saline body of surface water;

[0078] wherein the conduit comprises a first end and a second end opposite the first end, the plurality of fibers extending between the first end and the second end; wherein the CCh-containing fluid is a gas; and wherein simultaneously introducing the aqueous sorbent and the CCh-containing fluid into the fiber contactor comprises: introducing the aqueous sorbent through a first inlet proximate the first end of the conduit; and introducing the CCh-containing fluid through a second inlet proximate the second end of the conduit such that a flow of the CCh-containing fluid is countercurrent to a flow of the aqueous sorbent; and / or

[0079] wherein the CCh-containing fluid is a liquid.

[0080] A system has been described herein. The system includes a CO2 source configured to produce a CCh-containing fluid; a saline source comprising a saline solution; and a reactor complex configured to receive the CCh-containing fluid from the CO2 source and the saline solution from the saline source, the reactor complex including a fiber contactor comprising a conduit having a plurality of fibers disposed therein, wherein the plurality of fibers comprise a carbonic anhydrase enzyme immobilized on surfaces thereof; wherein, through contact of the CCh-containing fluid and the saline solution within the fiber contactor, the reactor complex is configured to sequester at least a portion of the CO2 from the CCh-containing fluid in an aqueous reaction product comprising a water-soluble bicarbonate salt, a water-insoluble carbonate salt, or a combination thereof. The system may include any one or more of the following features:

[0081] wherein the CO2 source is a fermenter;

[0082] wherein the saline source is a saline body of surface water;

[0083] wherein the system is further configured to direct the aqueous reaction product from the reactor complex to a saline aquifer or the saline body of surface water;

[0084] wherein the saline source is a saline aquifer; and / or

[0085] wherein the system is further configured to direct the aqueous reaction product from the reactor complex to the saline aquifer, a second saline aquifer, or a saline body of surface water.

[0086] It is understood that variations may be made in the foregoing without departing from the scope of the present disclosure. In several example embodiments, the elements and teachings of the various illustrative example embodiments may be combined in whole or in part in some or all of the illustrative example embodiments. In addition, one or more of the elements and teachings of the various illustrative example embodiments may be omitted, atleast in part, and / or combined, at least in part, with one or more of the other elements and teachings of the various illustrative embodiments.

Claims

CLAIMSWhat is claimed is:

1. A method comprising:providing a fiber contactor comprising a conduit having a plurality of fibers disposed therein, wherein the plurality of fibers comprise a carbonic anhydrase enzyme immobilized on surfaces thereof; andsimultaneously introducing an aqueous sorbent and a CCh-containing fluid into the fiber contactor to catalytically sequester CO2 from the CCh-containing fluid in the aqueous sorbent.

2. The method of claim 1, wherein the aqueous sorbent is water; andwherein catalytically sequestering CO2 from the CCh-containing fluid in the aqueous sorbent forms a bicarbonate ion-containing solution.

3. The method of claim 2, further comprising reacting the bicarbonate ion-containing solution with an alkali metal salt to form a bicarbonate salt solution.

4. The method of claim 3, further comprising drying the bicarbonate salt solution to yield a solid bicarbonate salt.

5. The method of claim 3, further comprising injecting the bicarbonate salt solution into a subterranean well.

6. The method of claim 2, further comprising reacting the bicarbonate ion-containing solution with an alkaline earth metal salt to form a water-insoluble carbonate salt.

7. The method of claim 1, wherein the aqueous sorbent is a saline solution comprising an alkali metal salt, an alkaline earth metal salt, or a combination thereof; and wherein catalytically sequestering CO2 from the CCh-containing fluid in the aqueous sorbent forms an aqueous reaction product comprising a water-soluble bicarbonate salt, a water-insoluble carbonate salt, or a combination thereof.

8. The method of claim 7, wherein the saline solution is from a saline aquifer; andwherein the method further comprises withdrawing the saline solution from the saline aquifer through an uptake well.

9. The method of claim 8, further comprising transferring the aqueous reaction product to the saline aquifer through an injection well, wherein the injection well is laterally spaced from the uptake well.

10. The method of claim 8, further comprising transferring the aqueous reaction product to a second saline aquifer that is isolated from the saline aquifer.

11. The method of claim 7, wherein the saline solution is from a saline body of surface water.

12. The method of claim 11, further comprising transferring the aqueous reaction product to the saline body of surface water.

13. The method of claim 1, wherein the conduit comprises a first end and a second end opposite the first end, the plurality of fibers extending between the first end and the second end;wherein the CCh-containing fluid is a gas; andwherein simultaneously introducing the aqueous sorbent and the CCh-containing fluid into the fiber contactor comprises:introducing the aqueous sorbent through a first inlet proximate the first end of the conduit; andintroducing the CCh-containing fluid through a second inlet proximate the second end of the conduit such that a flow of the CCh-containing fluid is countercurrent to a flow of the aqueous sorbent.

14. The method of claim 1, wherein the CCh-containing fluid is a liquid.

15. A sy stem compri sing :a CCh source configured to produce a CCh-containing fluid;a saline source comprising a saline solution; anda reactor complex configured to receive the CCh-containing fluid from the CO2 source and the saline solution from the saline source, the reactor complex including a fiber contactor comprising a conduit having a plurality of fibers disposed therein, wherein the plurality of fibers comprise a carbonic anhydrase enzyme immobilized on surfaces thereof; andwherein, through contact of the CCh-containing fluid and the saline solution within the fiber contactor, the reactor complex is configured to sequester at least a portion of the CO2 from the CCh-containing fluid in an aqueous reaction product comprising a water-soluble bicarbonate salt, a water-insoluble carbonate salt, or a combination thereof.

16. The system of claim 15, wherein the CO2 source is a fermenter.

17. The system of claim 15, wherein the saline source is a saline body of surface water.

18. The system of claim 17, wherein the system is further configured to direct the aqueous reaction product from the reactor complex to a saline aquifer or the saline body of surface water.

19. The system of claim 15, wherein the saline source is a saline aquifer.

20. The system of claim 19, wherein the system is further configured to direct the aqueous reaction product from the reactor complex to the saline aquifer, a second saline aquifer, or a saline body of surface water.

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