HK1150307B - Method and apparatus for extracting carbon dioxide from air - Google Patents

Description

From the airMiddle extraction of CO2Method and apparatus

Technical Field

One aspect of the invention relates to removing a selected gas from air. The invention is particularly useful for extracting and sequestering carbon dioxide (CO) from air₂) And are described in connection with such uses, although other uses are contemplated.

Background

There is compelling evidence that there is a strong correlation between a dramatic increase in atmospheric carbon dioxide levels and a corresponding increase in global surface temperatures. This effect is commonly referred to as global warming. CO2₂There are a large number of small, widely distributed emissions from a variety of sources, and it is impractical to mitigate them from a source. In addition, large scale emissions, such as hydrocarbon fueled power plants, are not adequately protected from exhaust CO₂And enters the atmosphere. These major sources, in combination with others, result in the occurrence of a sharp increase in atmospheric carbon dioxide concentration. Until all emissions are corrected at their source, other technologies are needed to capture the background levels of atmospheric CO that are increasing, albeit relatively low, until such time as they are corrected₂. Efforts are underway to improve existing emission reduction technologies and to develop new technologies for direct capture of ambient CO₂. These efforts require methodology to manage the CO produced thereby₂To prevent it from being reintroduced into the atmosphere.

CO₂The generation of (b) occurs in various industrial applications such as the generation of electricity from coal by electric power plants and the use of hydrocarbons, which are often the main components of fuels that are burned by combustion equipment such as engines. The exhaust gases from these combustion units contain CO₂The gas, at present, is simply released into the atmosphere. However, with increasing interest in greenhouse gases, CO from all sources₂The discharge will have to be reducedAnd (4) subtracting. For mobile sources, the best choice is likely to be to collect carbon dioxide directly from the air rather than from a mobile combustion device of an automobile or aircraft. Removal of CO from air₂Has the advantage that it is no longer necessary to convert CO into₂Stored on the mobile device.

Extraction of carbon dioxide (CO) from ambient air₂) Making it possible to utilize carbon-based fuels and to treat the associated greenhouse gas emissions afterward. Removal of CO from air is due to the fact that carbon dioxide is neither toxic nor harmful in parts per million quantities, but causes environmental problems only by accumulating in the atmosphere₂It is possible to make up for the same amount of emissions elsewhere at different times.

However, most prior art processes result in the capture of CO from air₂It is inefficient because these processes heat or cool air, or change the air pressure by a large amount. Thus CO₂The net loss is negligible because the cleaning process will be CO₂Introduced into the atmosphere as a byproduct of the power generation that powers the process.

Various methods and devices have been developed for removing CO from air₂. For example, we have recently published an efficient extraction of carbon dioxide (CO) from ambient air using a capture solvent₂) The method of (3), these solvents physically or chemically bind and remove carbon dioxide from air. Practical CO₂The trapping adsorbent comprises a strongly basic hydroxide solution, such as sodium hydroxide or potassium hydroxide, or a carbonate solution, such as sodium carbonate or potassium carbonate brine. See published PCT applications PCT/US05/29979 and PCT/US05/029238 for examples.

Sequestered CO₂There are also many uses: this includes CO₂Use in greenhouses where higher levels of CO are present₂Is helpful for promoting plant growth. CO2₂Can also be used for algae culture. Researchers have indicated that algae can enrich for CO from₂Removing up to 90% of the gaseous CO from the air stream₂Can also reduce CO in the ambient air₂The concentration of (c).

Disclosure of Invention

The present invention provides a system for extracting carbon dioxide (CO) from air₂) And extracting CO₂Methods and apparatus for delivery to a controlled environment.

In a first exemplary embodiment, the present invention extracts CO from ambient air₂And extracting CO₂And transferred to the greenhouse. Preferably, strongly basic ion exchange resins are used which have a strong moisture function, i.e.are capable of absorbing CO with decreasing moisture₂And CO release with increasing humidity₂Ion exchange resin of (2) for extracting CO from ambient air₂. Several aspects of the invention may also be used to convert CO₂From the collector medium to the air space of the greenhouse, where CO is transferred₂Is fixed again in the biomass. In a preferred embodiment of the invention, the CO is extracted using an extractor (extractor) located close to the greenhouse₂Extracting from the air to the greenhouse and extracting the CO₂Directly delivered to the interior of the greenhouse for enriching the greenhouse air with CO₂In order to promote plant growth.

In a second exemplary embodiment of the invention, the invention allows for the CO to be introduced₂Transfer from the collector medium to algae cultivation where CO₂Is immobilized in the biomass. The algal biomass can then be used to produce biochemical compounds, fertilizers, soil conditioners, health foods, biofuels, and the like, to name a few applications or end uses.

The invention also discloses CO in the gas phase₂As a transfer of bicarbonate ions. In one embodiment, limescale algae is used, which inherently produces calcium carbonate CaCO₃And CaCO₃Precipitated as limestone.

Thus, in broad concept, the present invention utilizes one of several carbon dioxide extraction techniques as described in PCT/US05/29979 and PCT/US06/029238, supraExtraction of carbon dioxide from air: wherein a carbonate/bicarbonate solution is used as the predominant CO₂Adsorbent loaded with CO₂The adsorbent of (2) can be directly used as algae feed. When extracting CO using ion exchange resin₂In the case of CO, using a secondary carbonate/bicarbonate wash, as taught for example in our aforementioned PCT/US06/029238 application₂Stripped from the resin and then used as an algae feed. In preferred further embodiments, the algae may be fed with carbonate in a light enhanced bioreactor.

Thus, the present invention provides a simple, relatively low cost capture of CO from ambient air₂CO to be captured subsequently₂A solution to the process.

Brief description of the drawings

Further features and advantages of the present invention will become apparent from the following detailed description when taken in conjunction with the drawings, in which

FIG. 1 is a block flow diagram illustrating the use of a moisture sensitive ion exchange resin according to the present invention;

FIGS. 2a and 2b are CO's according to the invention₂Schematic of extractor/greenhouse stuffer, wherein the filtration unit exterior wall;

FIGS. 3a and 3b are CO's according to the invention₂Schematic of extractor/greenhouse stuffer, wherein the filtration unit is near the greenhouse roof;

FIG. 4 is a CO showing the arrangement of the filter unit according to the invention₂Schematic of extractor/greenhouse stuffer;

FIG. 5 shows a CO with filter units arranged on a track according to an alternative embodiment of the invention₂Schematic of extractor/greenhouse stuffer;

FIG. 6 is a CO including a convection column according to an alternative embodiment of the present invention₂Schematic of extractor/greenhouse stuffer;

FIG. 7 is CO according to the invention with suitable collector medium humidity fluctuations₂Schematic of an extractor and algae culture;

FIG. 8 is CO with adaptive collector solution fluctuation according to the present invention₂Schematic of an extractor and algae culture;

FIG. 9 is a diagram of the transfer of gaseous CO by an electrodialysis process according to the invention₂CO of₂Schematic of an extractor and algae culture;

FIG. 10 is CO for bicarbonate transfer by an electrodialysis Process according to the present invention₂Schematic of an extractor and algae culture;

FIG. 11 is CO for use in algal cultivation for trap regeneration according to the present invention₂Schematic of an extractor and algae culture;

FIG. 12 is a CO similar to FIG. 11 using nutrient solution for collector regeneration₂Schematic of an extractor and algae culture;

FIG. 13 is a CO utilizing a breathable film according to the present invention₂Schematic of an extractor and algae culture;

FIG. 14 is CO utilizing an anion permeable membrane according to the present invention₂Schematic of an extractor and algae culture;

FIG. 15 is a CO similar to FIG. 14₂Schematic of an extractor and algae culture;

FIG. 16 is a CO including a shower in accordance with the present invention₂Schematic of an extractor and algae culture; and

FIG. 17 is a CO similar to FIG. 16₂Schematic of an extractor and algae cultivation.

Detailed Description

In broad terms, one aspect of the present invention utilizes the conventional CO disclosed in the above-identified patent application or disclosed herein₂Extraction process or improved CO₂The extraction method extracts carbon dioxide from ambient air and at least a portion of the extracted CO₂Is released into an enclosed environment.

In a first exemplary embodiment, the enclosed environment is a greenhouse. Preferably, but not necessarily, CO₂The extractors are located close to the greenhouse and in a preferred embodiment the extractors also provide shade for crops that are sensitive to intense light to grow in the greenhouse and/or reduce cooling requirements for the greenhouse.

In the capture of CO₂In one approach of (2), the resin media is regenerated by contact with warm, highly humid air. Humidity has been shown to stimulate CO storage in storage media₂By which CO can be released₂The concentration reaches 3% -10%, and can reach nearly 100% in an emptying/dewatering system. In this pathway, CO₂Returning to the gas phase, no liquid medium is carried into contact with the collector material.

CO₂The extractor is located in close proximity to the greenhouse and is moved out of the greenhouse to collect CO₂Moving to a greenhouse for discharging CO₂. In this embodiment, CO₂The extractor preferably comprises a moisture sensitive ion exchange resin, wherein the ion exchange resin extracts CO when dry₂CO evolution on exposure to high humidity₂. Humidity fluctuations are best suited for use in arid climates. In such an environment, the extractor is exposed to the hot, dry air outside the greenhouse, CO₂Is extracted from the air. The extractor is then moved to the warm and humid environment of the greenhouse where the ion exchange resin emits CO₂. The whole process can be completed without any direct energy input, except for the energy to move the extractor from outside to inside the greenhouse and vice versa.

Ion exchange resins are commercially available for applications such as water softening and purification. We have found that certain commercially available ionsThe sub-exchange resin is a moisture sensitive ion exchange resin, including a strong base resin, which can be advantageously used for extracting CO from air according to the invention₂. With this material, the lower the humidity, the higher the carbon balance loaded on the resin.

Thus, at high humidity levels, CO loading is shown₂And with CO₂Resins with a specific partial pressure phase equilibrium that will exhale CO if humidity is increased₂Decrease in humidity will absorb CO₂. This effect is large and it is easy to change the equilibrium partial pressure by hundreds or even thousands of ppm. The amount of carbon that is additionally absorbed or lost on the resin is also substantial if compared to its total absorption capacity.

Humidity may also have an effect on the heat transfer coefficient, i.e. the reaction kinetics may change with changes in humidity. However, the measured flow rate into and out of the resin may depend strongly on the difference between the actual partial pressure and the thermodynamically equilibrium pressure. When the equilibrium pressure changes with humidity, the flow rate is affected without actual changes in the reaction kinetics:

furthermore, the kinetics may also be affected by other problems. For example, we have found that a particularly useful ion exchange material is an anion I-200 ion exchange membrane material available from Snowpure, Inc. of Santa Clarit, Calif. Manufacturers introduce anion I-200 ion exchange membrane materials as strongly basic, type 1 functional ion exchange materials. Such materials, which may be considered to be made according to U.S. patent No.6503957 and are considered to include graphic encapsulation or-partial encapsulation-of small resins in an inactive polymer such as polypropylene. We have found that if such a material is hydrated and then dried, the material becomes porous and readily allows air to pass through. The hydration/dehydration preparation is believed to function primarily as an expanded polypropylene binder with little or no permanent effect on the resin, while subsequent humidity fluctuations have no observed effect on the polypropylene binder. We have found that these strongly basic ion exchange resin materials have the ability to extract CO from dry air₂CO release when humidity increases without further intervention₂The ability of the cell to perform. These are directly from dryingExtracting CO from air₂CO exhaled when humidity increases₂The materials of (3) have not been previously reported.

As mentioned above, it is necessary to hydrate the material and then dry it before use, whereupon the material becomes porous and readily allows air to pass through. Prior to hydration, the membrane material is substantially non-porous or at least does not allow appreciable amounts of air to pass through the membrane. However, upon hydration and drying, the material is believed to undergo irreversible deformation of the polypropylene matrix upon expansion of the resin upon hydration. Once the material has deformed, the polypropylene matrix maintains its extended shape even after the resin particles dry shrink. Therefore, for the above-mentioned substantially non-porous materials such as the Snowpure ion exchange material, it is necessary to prepare the material in advance by hydration and then drying before use.

We observed CO₂The equilibrium partial pressure on the resin changes with changes in humidity. Humidity either changes the state of the resin or alternatively the entire system, the whole system to be considered being CO₂/H₂And (3) an O resin system. While not being bound by theory, it is believed that CO₂The free energy of adhesion to the resin being H in equilibrium with the resin₂O partial pressure.

This makes it possible for the resin to absorb or exhale CO with a simple swinging movement of humidity₂Without resorting to theoretical fluctuations and/or pressure fluctuations that increase the energy cost to the total CO of the system₂The balance has an adverse effect.

The amount of water involved in this fluctuation seems to be rather small. The possibility of humidity fluctuations also allows us to recover CO from air collectors with minimal water loss involved₂。

Other strong base type 1 and type 2 functional ion exchange resins are commercially available from various suppliers including dow, dupont and roman haas and may also be advantageously used in the present invention, either obtained from the manufacturer or formed into heterogeneous ion exchange membranes following the teachings of U.S. patent No.6,503,957.

Fig. 1 illustrates a first embodiment of the present invention. The primary ion exchange filter material 4 is placed on the recirculation cycle. When valve V1 is opened and pushed through exhaust port 2, the main pump 1 or a second pump (not shown) can be used to remove most of the air in the system. At this point valve V1 is closed and the secondary ion exchange capture resin is transferred to the system by opening valves V2 and V3. Secondary ion exchange resins may be used to provide humidity and possibly some heat. Thermal steam stimulation of CO₂Released from the primary ion exchange filter material 4, which is then captured on a secondary ion exchange resin, which is reacted with CO₂The partial pressure is still in an unbalanced state. The volume of water in the system remains small because it can be recycled and not absorbed by the secondary resin. When CO is present₂When unloaded from the primary ion exchange resin material 14 and absorbed by the secondary ion exchange resin, most of the water circulates through the device. The amount of water that can be diverted or absorbed is much less than the CO that is diverted₂Amount of the compound (A). At the end of the cycle, the primary ion exchange filter material 14 is renewed and the secondary ion exchange capture resin is loaded with CO₂。

The system can be used to transfer CO from an air capture medium, such as an ion exchange resin on a secondary resin₂Without having to wash or wet the main resin. This has two advantages. First, the primary resin is not directly exposed to chemicals such as amines used in the past and described in our above-mentioned PCT application No. PCT/US 061/029238. Second, we have seen that wet resins are not effective at absorbing carbon dioxide until dry out. It is therefore advantageous to avoid wetting of the material and thus to operate in such a way that the resin is washed with low-pressure steam. The steam pressure may be less than 100pa and thus reach saturation at temperatures of similar ambient value. However, at higher temperatures and higher steam pressures, CO₂The exchange is significantly accelerated. The disadvantage of elevated temperature is increased energy consumption.

The designs described herein are specific examples of a broader class of designs that use energy to absorb CO₂And any other adsorbent material that does not absorb water replaces the secondary resin. Such asThe adsorbent may comprise liquid amine, ionic liquid, solid CO₂Adsorbents such as lithium zirconate, lithium silicate, magnesium hydroxide or calcium hydroxide, or any of a wide variety of materials capable of absorbing moisture vapor and CO₂To absorb CO in the gas mixture₂Chemical or physical adsorbents. The central concept lies in the use of humidity fluctuations rather than pressure or temperature fluctuations to remove CO from the primary adsorbent₂Without its direct physical contact with the secondary adsorbent.

Use in greenhouses for increasing crop yield

As mentioned above, crop yield in greenhouses can be increased by increasing the level of carbon dioxide in greenhouse gases. The invention introduces carbon dioxide into the greenhouse without combusting and discharging CO, a fossil fuel, to the air₂The fuel of (2). More specifically, we have found that moisture sensitive ion exchange resins can be employed to capture CO from the outside air₂And then exposing the CO to warm humid greenhouse air by exposing the resin to the air₂Released in the greenhouse.

Greenhouse, outside CO, in warm desert climates such as found in the southwest United states₂Can be carried out at night when the temperature is cooler, so that the CO can be increased₂The absorption capacity of (1). In cooler climates, the greenhouse relies in part on radiant heating, our CO₂The load system does not need to let in cold air to replenish CO₂Thereby reducing the need for heating with fossil fuel consumption unless the temperature drop is so low that fuel heating becomes necessary.

In one embodiment, we employ several filters made of moisture sensitive ion exchange active materials. The filter is exposed to ambient air driven by natural airflow through thermal convection or a blower during a portion of the cycle. Blowers are preferably avoided as they add unnecessary energy losses. In the second part of the cycle, moist air from the greenhouse is preferably driven (e.g. by a blower) through the filter material, and then CO is released₂Into the greenhouse atmosphere. Since the climate control of a greenhouse will typically be anywayRelying on a fan system, there is little or no energy loss.

Because plants breathe at night, in some greenhouse designs, it is possible to remove CO from greenhouse air by pulling the greenhouse air through a filter₂. The filter may then be exposed to higher humidity to facilitate release of CO during the day₂Entering a greenhouse.

In one embodiment, as shown in fig. 2A and 2B, the filter unit 10 is adjacent an exterior wall 12 of the greenhouse through which outside air or greenhouse air is selectively passed, as the case may be, through a pivotally mounted wall panel 14. In addition, as shown in fig. 3A and 3B, the filter material 10 may be located outside of the greenhouse roof 18 or adjacent to the greenhouse roof 18, whereby ambient air or greenhouse air may selectively pass, as the case may be, through the pivotally mounted roof 20.

In another embodiment of the invention, as shown in fig. 4, the filter units 10 may be moved from outside the greenhouse to inside the greenhouse, where they extract CO from the air₂In greenhouses they release captured CO₂. One possible option for doing this is to mount the filter unit on a pivotally mounted wall or ceiling 22, the wall or ceiling 22 being reversible to expose the filter unit outside the greenhouse to the greenhouse and vice versa. The filter unit in the greenhouse may have air blown through it by a blower system. The external filter unit is exposed to the ambient air. In a preferred embodiment, as shown in fig. 4, the outer filter unit 10 is near the bottom end of a solar driven convection tower 24. Preferably, the inlet is mounted at the bottom end of a convection tower where cool air enters by natural convection and flows over the tower.

In another embodiment, as shown in FIG. 5, the filter unit 10 is moved into or out of the greenhouse, such as by hovering over a track 26.

Referring to fig. 6, yet another alternative for the greenhouse is to place the convection tower outside the greenhouse as a double glass wall and use the resulting convection fluid to collect external CO₂. The double wall also contributes to reducing the heat load on the interior during the day and thus the need for air exchange, which makes it possible for the greenhouse to maintain high levels of CO₂. The double wall also reduces heat loss at night.

In this example, a cover glass surface 40 may be provided to keep heat away from the main roof of the glass house 42, creating a convective flow 44 of ambient air above the roof surface. Convection of ambient air through the CO₂An absorbent filter medium 46 that can be exchanged in position with a second similar filter medium 50 by some mechanism, such as a rotating top plate 48, whereby air driven by a blower 52 inside the greenhouse passes through the filter medium, releasing captured CO when the filter medium is exposed to the ambient air outside the greenhouse₂. Since the air in the greenhouse is humid, CO₂Easily released from the filter medium and increases the CO available in the greenhouse₂。

One advantage of such a unit is that it can be used without combusting the fuel at high levels of CO₂And (4) running. Because of CO₂Transfer into the greenhouse without blowing air into the greenhouse provides the possibility of reducing the exchange of air between the inside and the outside of the greenhouse, thereby improving the thermal and moisture management of the greenhouse.

In a second exemplary embodiment of the invention, CO₂Extracted and passed to an algae or bacteria bioreactor. This can be done using conventional CO₂The extraction process may be accomplished by using an improved extraction process as disclosed in our above-mentioned PCT application or as disclosed herein, for example by humidity fluctuations. CO extraction facilitated by humidity fluctuations₂To the algae because the physical separation allows the use of any collector media without concern for compatibility between the media and the algae cultivation solution. Gaseous CO₂The transfer of (a) allows selection of any algae species, including giant and micro algae, marine or freshwater algae. Thus, the choice of algae species to be grown may depend only on environmental factors and water quality at the locus of the collector. For example, the species of algae used may be selected from algae that naturally grow in a location, which are uniqueIs suitable for local atmosphere, environment and water quality conditions.

Transfer of captured CO in gaseous form₂There are two advantages. The first advantage is that the collector media and/or collector regeneration solution will not contact the algae cultivation solution and/or algae. The second is that all kinds of algae can absorb gaseous CO₂。

CO according to specific algae₂Tolerant, continuous pumping of CO-rich gas with a pump₂Through several algae cultures in order to reduce CO₂Tolerance and enhancement of CO₂The absorption efficiency. Furthermore, air can be diluted to an optimum CO₂And (4) concentration.

Referring to FIG. 7, one embodiment of the present invention utilizes the use of humidity fluctuations to drive off gaseous CO from the collector medium₂This fact. CO that humidity fluctuation will catch₂In the gaseous state of CO₂The form is transferred from the collector 110 to the algae culture 116. Loaded with CO when subjected to increased humidity or wetting with water₂Will give off gaseous CO₂. When supplying CO₂Will absorb more gaseous CO and/or the collector medium will dry out₂。

The present invention provides a common headspace above the collector medium and the algae culture. When the collector medium and algae culture are physically separated, this exposes the algae to gaseous CO₂In (1). The humidity within the enclosed headspace volume is then increased. Furthermore, wetting of the collector medium may be chosen. The CO2 evolved from the collector medium quickly diffused throughout the headspace and contacted the surface of the algae broth.

Introducing CO into the algae culture solution by gas diffusion or bubbling headspace gas with a recirculating pump₂Transferring to algae culture. CO removal from the headspace with algae₂The collector media continues to exhaust until equilibrium is reached. The algae culture solution can be mechanically stirred. All other nutrients and lighting are provided to the algae as requiredAnd (4) class. The algae may then be collected in an algae harvester 120.

CO in the headspace above the wetted collector medium₂The concentration reaches 20 percent; or 0.2 atmosphere partial pressure. The concentration can be adjusted by the volume/volume ratio of the collector medium and the headspace. The collector media can also release 60% of the captured CO during humidity fluctuations/wetting₂。

In addition, to transfer CO₂It is also possible to pump air from the collector medium volume into the algae culture. If the algae pond is warm and moist, the moisture from the algae pond is again sufficient to stimulate CO through the mechanism of humidity fluctuation₂Release from the dry resin.

Referring to FIG. 8, in another embodiment of the present invention, CO in ambient air₂The concentration can make the ion exchange medium full of CO₂To CO₂Is bound to the level of bicarbonate ions. The present invention provides regeneration of the collector media using an alkaline solution. During regeneration, the anionic component in the solution becomes nearly 100% bicarbonate. The aqueous bicarbonate solution is unstable under atmospheric conditions and releases gaseous CO₂. Gaseous CO enhancement by bubbling top air into solution with recirculation pump₂And (5) discharging.

An alternative embodiment provides a common headspace above the collector regeneration solution and the algae cultivation solution. When the regeneration solution and the algae culture solution are separated, the algae are exposed to gaseous CO₂In (1). In other respects, the headspace operates similarly to the collector media headspace discussed above.

Referring to fig. 9, another alternative embodiment of the present invention uses an Electrodialysis (ED) process to release gaseous CO from a supported collector solution₂. CO released thereafter₂Is transferred to the algae culture 216. Gaseous CO₂An advantage of transferring from the collector 210 to the algae culture by the Electrodialysis (ED) process is that the collector solution or adsorbent is physically associated with the algae broth at all stages of the processAre separated from each other. This prevents mixing of the two solutions and also prevents ion exchange between the solutions. The ED method is the same as the humidity fluctuation method. And in the humidity process, the physical separation allows the use of any collector media and any algae regardless of the compatibility between the media and the algae broth.

An alternative embodiment of the invention utilizes the available ED process to convert gaseous CO into gaseous CO₂The fact that the collector regeneration solution is drained. In the ED process, the loaded collector regeneration solution is split into two streams into ED cells (ED cells) 214. Protons are added to the first stream across the secondary membrane 236, inorganic carbon as CO₂The forms are discharged and sodium ions are transferred across the cationic membrane 234 into the second stream. In addition to sodium ions, hydroxide ions are also added to the second stream across another secondary membrane 236, thereby neutralizing the bicarbonate in this stream to carbonate.

The first stream exits the ED unit as water or dilute sodium bicarbonate solution, while the second stream exits as concentrated sodium carbonate solution. The two streams were combined to form a fresh collector solution. Gaseous CO discharged from the first stream₂Bubbled into the algae culture and fixed to biomass.

As inorganic carbon is removed from the brine, the solution becomes more basic, requiring the addition of additional bicarbonate to maintain the pH. Filtration allows us to recover some of the fluid and thereby recover water and sodium from the bioreactor. In one particular practice, an electrochemical cell (electrochemical cell) will operate between two separate fluid cycles, one being fairly alkaline, between the collector and the alkaline side of the electrochemical cell, and the other at near neutral pH between the algae reactor and the acidic side of the cell. The carbonic acid is transferred from the basic side of the unit to the acidic side. This step regenerates the scrubbing liquid and uses CO₂The fluid is reloaded.

CO can be added by adding bicarbonate adsorbent to algae₂Removing from the adsorbent without first having to remove CO₂Conversion back to CO₂A gas. And, by being emptyThe gas capture side selects a suitable adsorbent material, the pH of the wash liquor can be kept relatively low, and if algae that can tolerate relatively high pH are used, the pH difference created by electrodialysis needs to be made relatively small, and in some implementations the dialysis unit can be completely removed.

Referring to fig. 10, another embodiment of the present invention uses the ED method to reduce the bicarbonate concentration in the collector solution and increase the bicarbonate concentration in the algae broth. The collector solution enters the ED unit 214 in bicarbonate form, while the algae broth enters the ED unit in carbonate form. When these fluids exit the ED unit, the collector solution is in carbonate form and the algae broth is in bicarbonate form.

The algae solution is reduced to about half its normal state due to the transfer of cations from the algae broth to the collector solution; and the collector solution is approximately twice its normal state. To compensate for the sodium imbalance, half of the loaded collector solution (bicarbonate form) is transferred directly from the collector to the algae culture.

In the process version according to the invention, cations are transferred from the algae solution to the collector solution across the cation exchange membrane 234. The algae culture broth contains mainly sodium ions, but also potassium, magnesium and calcium ions and traces of other metal ions. The potential transfer of magnesium and calcium should be of concern because these two ions form rather insoluble carbonates and hydroxides. The formation of these salts, also known as ocular barriers (scaling), can damage the membrane and/or the collector medium of the ED unit.

Calcium and magnesium are added to the algae culture as mineral nutrients at the beginning of the algae growth cycle. As the algae biomass increases, calcium and magnesium are absorbed into the biomass and their concentrations in the algae broth decrease. Meanwhile, the broth pH increases as the bicarbonate solution is converted to carbonate solution. If the magnesium, calcium and carbonate ions are present beyond their solubility product, chemical precipitation will further reduce the magnesium and calcium ion concentration.

Spent culture broth with reduced calcium and magnesium concentrations and high pH is fed into the ED unit. The broth is there converted from carbonate to bicarbonate solution and its pH is reduced accordingly. As the carbonate ion concentration decreases, the solution can retain more calcium and magnesium. It is less likely that an eye-obstruction will occur in this portion of the ED unit.

At the same time, however, cations containing calcium and magnesium are transferred from the algae broth 216 to the ED half-cell collector solution. In this half-cell, the bicarbonate solution from the collector is converted into a carbonate solution: carbonate concentration and pH increase. In addition, excess water may be removed from the bicarbonate solution with the reverse osmosis unit 224.

The process is designed so that the pH of the exiting collector solution is close to the pH of the entering algae solution. Thus, everything that remains balanced should not happen. However, maintaining a perfect balance may not always be practical on a macro scale, nor on a micro scale within the ED unit. It is possible to form micro-layers or capsules (layers) with increased hydroxide or cation concentrations on the membrane surface. The increased concentration of the membrane surface may cause an eye-block in the collector solution half-cell.

To minimize the obstruction, the flux of calcium and magnesium cations must be minimized. This is a well-known problem in the production of salt from seawater, in the production of sodium hydroxide, and in the treatment of skim milk by electrodialysis (t.sata, 1972; t.sata et al, 1979, 2001; j.balster, 2006). To minimize flux, the cationic membrane separating the two half-cells must be a selectable monovalent ion. In general, strongly acidic cation exchange membranes exhibit greater transport numbers of divalent than monovalent ions. This is presumably due to the higher electrostatic attraction of the negatively charged fixed ion exchange sites. The prior art shows that the number of transport of divalent cations decreases as the charge density on the membrane decreases.

Two commercially available highly monovalent cation selective membranes have been identified as being particularly suitable for use in this regardAnd (4) a process. One film is manufactured by Asahi Glass under the tradename Selemion CSV. The second is manufactured by Deshan Soda company (Tokuyama Soda) under the trade name ofAnd (3) CIMS. The transport number (t) of the Selemion CSV is: t (Na) < 0.92 and t (Ca, Mg) < 0.04. The transport number of Neosepta CIMS was t (Na, K) ═ 0.92 and t (Ca, Mg) ═ 0.10. The transport quantity is defined as the equivalent flow rate of cations divided by the total equivalent flow rate during electrodialysis.

This aspect of the invention uses a monovalent cation selective membrane to minimize the transfer of multivalent cations from the algae broth to the collector regeneration solution. Any obstructions that may have formed over time will be removed with the acid solution.

Both the algae broth and the collector solution are filtered to avoid contamination of the membranes with particles before entering the ED unit. The organic molecules will be removed from the algae culture by the organic scavenging ion exchange resin.

Referring to FIG. 11, in another embodiment of the present invention, CO is captured from air by adding a loaded collector solution 310 to the algae₂Is also transferred to algae. The loaded collector solution was rich in sodium bicarbonate. The nutrients are added into the collector solution, and become the raw material of the algae. In this embodiment of the invention the solution feed cannot be recycled, making the collector solution a consumable.

In this process, the algae broth 316 will increase in salt content as more and more sodium bicarbonate is added. Sodium bicarbonate is converted to carbonate during the growth of the algae. To reduce carbonate concentration and slow salinization, some of the remaining nutrients may be added as an acid rather than as a sodium salt, which will convert carbonate ions to bicarbonate and minimize sodium increase.

In addition, sodium bicarbonate sorbent can be added directly to the algae reactor to provide CO for the algae₂With carbonThe sodium salts are returned to the air extraction station and the algae are removed in further processing.

Many algae can utilize sodium bicarbonate as a carbon source. In addition, compared with CO₂Some algae prefer bicarbonate as a carbon source. These are typically algae produced in alkaline lakes where inorganic carbon is present primarily as bicarbonate. These algae can tolerate large fluctuations in pH 8.5-11. Other algae can be used HCO3^-As a carbon source, a pH range lower than pH 9 is required, which requires bubbling CO₂The bicarbonate/carbonate solution was passed in.

Algae use carbon sources to produce biomass through photosynthesis. Because photosynthesis requires CO₂Rather than bicarbonate, algae therefore catalyses the following reaction:

HCO₃ ^-→CO₂+OH^-

in HCO₃ ^-In the presence, it will become:

HCO₃ ^-+OH^-→CO₃ ^-2+H₂O

the growth of algae in bicarbonate solution causes the following changes to the solution: (1) HCO₃ ^-A decrease in concentration; (2) CO2₃ ^-2A decrease in concentration; and (3) an increase in pH.

Another embodiment of the invention uses the algae broth for collector regeneration. The collector medium in the form of a carbonate can absorb gaseous CO from the surrounding air₂Until the anionic component of the medium is approximately 100% bicarbonate. In this state, the collector medium is fully loaded and the CO is₂Absorption is about to stop. The carbonate solution can be used in regeneration to return the loaded collector media to the carbonate form by ion exchange. The ionic component of the regeneration solution can be changed from 100% carbonate to nearly 100% bicarbonate by ion exchange with a fully loaded collector medium. In the process of the counter-current regeneration,the collector media may be charged with the carbonate form when the carbonate regeneration solution is converted to a bicarbonate solution. When the regeneration solution is a bicarbonate solution it is fully loaded because it cannot remove any bicarbonate from the collector medium.

Algae are introduced into the process to remove captured CO from the loaded regeneration solution by bicarbonate dehydration and neutralization (see above)₂. CO the algae will release₂For biomass growth. The regeneration solution changes from bicarbonate to carbonate solution.

In this process, the carbonate regeneration solution and the collector medium are reused, while the CO of the ambient air is reused₂And changed into algal biomass as shown in fig. 11.

The method provides for the absorption of air CO by an ion exchange collector medium₂The cycle of (2). During absorption, the collector medium changes from the carbonate to the bicarbonate form. The regeneration solution then withdraws CO from the loaded collector medium₂. In this exchange, the collector media is switched back to its carbonate form and the regeneration solution is changed from carbonate to bicarbonate. Finally, by introducing CO₂Fixed in biomass, algae remove gaseous CO from loaded regeneration solution₂. In this step, the algae catalyses the conversion of bicarbonate to CO₂And a carbonate salt. CO2₂Is bound into the algal biomass. The carbonate remains in solution. The regenerated solution thus produced then becomes in the form of carbonate.

In another embodiment of the present invention, the algae broth is used as a collector regeneration solution. This means that the collector regeneration solution will contain other nutrients required by the algae in addition to the carbonate. Wherein the nutrient is a cation that competes with the carbonate anion during ion exchange with the collector medium.

Diatoms will not be used in this process because they require silica, which cannot be adequately removed from the collector medium by the carbonate wash.

Other typical anionic nutrients found in algal culture media are: nitrate radical (NO)₃ ^-) Sulfate radical (SO)₄ ^-2) And phosphate radical (PO)₄ ^-3). Phosphorus may also be dibasic depending on pH (HPO 4)^-) Or one (H)₂PO₄ ^-) Phosphate is present.

Nitrate, sulfate and phosphate concentrations for a typical algae medium are:

nutrient	Bold Medium molarity (M)	Molar concentration of Zarouk Medium (M)
			NaHCO3		0.2
NaNO3	0.00882	0.029
			MgSO4-7H2O FeSO4-7H2O K2SO4Total S	0.0003 ∑＝0.003	0.0008 0.0018 0.0058 ∑＝0.0084
K2HPO4 KH2PO4Total P	0.00043 0.00129 ∑＝0.00172	0.0029 ∑＝0.0029

However, the prior art has shown that algae can grow in much lower nutrient concentrations than typical media contain.

To eliminate the effect of nutrient concentration on the collector media, the nutrient-containing regeneration solution was mixed as follows: 0.14M CO₃ ^-2，0.04M NO₃ ^-，0.0017M S0₄ ^-2And 0.0017M H₂PO₄ ^-1. These represent the highest concentrations found in the algae medium and are therefore the worst case.

The collector media is then flushed with this "worst case" solution until equilibrium is reached between the solution and the collector media. At the pH of the carbonate solution, phosphorus is present as a dibasic phosphate (HPO)₄ ^-2) The form exists. The dibasic phosphate is sufficiently basic to absorb CO₂. Thus, the presence of the dibasic phosphate anion on the collector medium will not reduce the CO of the medium₂The absorption capacity of (1). It was determined that at equilibrium about 50% of the total exchange sites of the collector media were occupied by carbonate and phosphate ions, while the other 50% were occupied by nitrate and sulfate. While other nutrients exceed the carbonate, they do not completely replace it; instead, a negative ion balance is achieved, which would not change the collector media with additional solution volume.

Experiments have shown that in the worst case, the collector medium absorbs CO₂About 50% of the capacity of (c). However, as determined by the studies cited above, the concentration of nutrients in the solution can be greatly depleted during the growth of the algae. For example, nitrate is by far the most abundant nutrient behind inorganic carbon, reaching 0.002M, only 5% of the worst case concentration used in the experiment. Phosphate is reduced to worst caseMoreover, 45 percent.

In addition, the collector media washed with nutrient depleted solution will lose about 20% of the absorbed CO₂The ability of the cell to perform. It is therefore possible to use the collector medium and wash it with a carbonate solution from the algae growth medium.

During metabolism or failure, the algae will secrete or release organic compounds into solution. These organics will be removed from the solution before the solution is used in the collector media. Organic removal may be by treatment with an ion exchange resin of the adsorption type or other means.

This method does not use diatoms because they require silica, which cannot be adequately removed from the collector medium with carbonate wash.

Algae preferred for the embodiments of the present invention have the following characteristics: they are compatible with high ionic strength liquids; they are capable of growing at a pH in the range of about 8.5 to 11; they are able to tolerate progressive pH changes; they can use bicarbonate as their carbon source; they require very little silica as a nutrient; they are capable of changing the solution pH from 8.5 to 11 or above; they can reduce the nutrient concentration to low levels; they can be used in biochemistry, agriculture, aquaculture, food, biofuel, etc.

Good candidates are, but not limited to: algae living in alkaline water, such as Spirulina platensis (Spirulina platensis), Spirulina fusiformis (Spirulina fusiformis), Spirulina sp. (Spirulina sp.), Tetradinium minimus (Tetraedron minium), etc.

There are many other options for this embodiment. Adding the loaded collector medium (nutrient depleted bicarbonate solution) to the algae culture along with fresh nutrients; algae culture utilizes bicarbonate as its inorganic carbon source by absorbing about 50% of the bicarbonate's carbon into its biomass and changing the remaining 50% to carbonate anions. At the same time, the algae culture is depleted of nutrient concentration in the solution. The culture broth is filtered, biomass is harvested and fed to CO₂CollectorThe nutrient depleted solution is shunted. The nutrient depleted solution is purged of organics and other materials that are harmful to the collector media. The solution now enriched in carbon can be used to regenerate the collector. In this process each carbonate anion is replaced by two bicarbonate anions until the collector solution has been loaded. The loaded collector solution is added to the algae broth along with the fresh nutrients described above.

The process can be run as a continuous loop or batch process, which is more practical considering location, algae type, etc. The method can adopt the already used and proven algae culture technology or new technology. For example, it has been demonstrated that spirulina, chlorella, branheimia and other species can be successfully cultured in open-air ponds in the state of california, hawaii, philippines and mexico, as well as elsewhere. Open ponds such as the so-called "race ponds" are the most economical method of growing large quantities of algal biomass according to the National Renewable Energy Laboratory (NREL).

The cultivation may use solar energy, artificial lighting, or both, depending on the algae species and the operating site. The algae broth can be stirred to return the algae to the strongest light entry zone. Or light may be brought into the algae culture by mirrors, optical fibers, or other means.

The algae may be suspended in solution or immobilized. When suspended, the algae follow their own growth pattern: single cells, clusters, etc. The natural growth pattern may not be an optimal match to the technique used. For example, small unicellular algae may require elaborate harvesting methods.

If attached to a surface, algae can naturally set up, such as giant algae. Or the algae may also be immobilized: beaded with k-carrageenan or sodium alginate, on polyurethane foam, on filter material, or immobilized as a biofilm on column packing, or other means.

In the immobilized state, the algae can still be suspended, such as in the form of beads, and flow with the solution. Further, the immobilized algae may be stationary in a cylinder or other device as the solution permeates therethrough.

In another embodiment of the invention, the collector medium is submerged in an algae culture (algamculture). This can be done in a batch process or a continuous process. In a batch process, the collector medium is alternately immersed in the algae culture and exposed to ambient air in batches. In a continuous process, the collector medium is continuously moved along a path on which it is alternately immersed in the algae culture or exposed to air. The simplest practice would be a disk of collector media that continuously rotates about its center. The disk is submerged in the algae culture to its central point so that at any time, half of the collector medium is submerged in the liquid and the other half is exposed to the air.

In this embodiment of the invention, the collector medium can potentially be submerged in the algae broth at high nutrient content and low nutrient content. Thus, the CO of the collector medium₂The capacity is 50-80% of its total capacity. The air exposure time may be adjusted to account for the reduction in capacity.

Referring to fig. 12, another embodiment of the present invention discloses sodium bicarbonate transferred from the collector solution to the algae by washing the algae in the loaded collector medium. But no nutrients were added to the collector solution. Alternatively, the nutrients are provided to the algae by a two-separation wash cycle consisting of a solution rich in nutrients and lacking carbon.

During this process, the algae will be alternately immersed in a nutrient-deficient bicarbonate solution (loaded collector solution) and a nutrient-deficient solution 326 that is devoid of inorganic carbon. Short rinse cycles will be used between washes. Rinsing will be added to the pre-wash of the solution.

The wash cycle of the nutrients and sodium bicarbonate will be optimized for the algae species used. One or more algae species may also be mixed or used sequentially in sequence to optimize the conversion of bicarbonate solution (loaded collector solution) to carbonate solution (fresh collector solution). The fresh collector solution may be filtered to remove particles and to remove organic molecules or other harmful contents prior to application to the collector media.

The method can be designed to utilize suspended algae or fixed algae. If the algae is suspended, the process must be run as a batch process and the algae must be filtered from the solution. For ease of filtration, the algae can be "fixed" on the suspended beads to increase the particle size.

The method involving fixing algae may use naturally growing fixed algae such as giant algae attaching themselves to the surface, or micro algae forming a biofilm, etc.

In addition to other methods disclosed herein, the algae may be immobilized within a column, inclined conduit, pond, or other vessel. These containers may be positioned to allow gravity fluid flow. The fixing may take place on the container wall and bottom and/or on structures mounted therein, such as plates, bags, etc. Light can be brought into the container by natural light, artificial light, a mirror, an optical fiber and the like as required.

Referring to FIG. 13, another embodiment of the present invention converts gaseous CO₂From the loaded collector solution 410, the algae broth 416 is transferred through the hydrophobic microporous membrane 434. Gaseous CO₂Can be transferred from the bicarbonate solution into the carbonate solution through the hydrophobic membrane; and CO between two liquid streams₂The partial pressure difference is sufficient to drive the transfer. It may be noted that the transfer of water is from a more dilute solution to a more concentrated solution. Since the membrane is hydrophobic, gaseous water molecules are transferred.

For simplicity, the method can be described as two half units separated by a microporous hydrophobic membrane. The first half unit 438 has a loaded collector solution (sodium bicarbonate solution); while the second half cell 418 has an algae culture (sodium bicarbonate solution with nutrients and algae)

The collector solution half-cell reaction is defined as follows:

2HCO₃ ^-(aq)→CO₂(g)+CO₃ ^-2(aq)+H₂O

then, CO₂(g) Diffuses through the membrane into the algae cultivation half-unit. The reaction in the algae cultivation half-unit will follow one of two ways:

algae consume CO₂(g)

Or

CO₃ ^-2(aq)+CO₂(g)+H₂O→2HCO₃ ^-(aq)

And

HCO₃ ^-(aq)+OH-→CO₃ ^-2(aq)+H₂O

as can be seen from the half-cell reaction, gaseous CO is released as the bicarbonate passes₂Carbonate is generated by the reaction, and the pH value of the solution in the collector is increased continuously. In an equilibrium system, gaseous CO is grown by algae₂When fixed in the biomass, the algae broth will not change its pH. The algae culture will preferably be in proximity to a carbonate solution. The conditions will be such that gaseous CO is between the collector solution and the algae culture₂The partial pressure difference is maximized.

The physical arrangement of the two half units may take a variety of forms including, but not limited to, the several arrangements described herein. Each arrangement will optimize the ratio of liquid film contact area to solution volume. In general, it is advantageous for the collector solution to run through membrane channels submerged in the algae culture, as this will provide light for the algae culture. In the case of a membrane tube containing algae culture, there will be illumination supplied within the tube.

The membrane conduits can have a variety of shapes. For example, they may be parallel membranes forming a sheet flow of solution sandwiched between the membranes. Or they may be tubular, with the tube cross-section taking on various forms, such as circular, square, rectangular, wavy, etc. The tubes may be formed into a spiral or other shape to increase their path length through the solution.

The process may be run as a batch procedure, a continuous loop process, or a combination thereof. Light and nutrients will be provided as needed.

In a pure batch process, a batch of loaded collector solution brought into the membrane is contacted and removed from a batch of algae culture to reach equilibrium.

In a purely continuous loop process, both solutions flow in a continuous loop. The loaded collector solution will flow along the membrane path through which the gaseous CO will pass₂Transferring into algae solution; from there it enters a regeneration system of the collector medium, where it is loaded with CO₂And then into the membrane conduit. The algae solution will fix gaseous CO with the algae₂Flowing through the membrane pathway; from there it will go to the harvest system 420 where some or all of the algae is removed from the solution and then to the membrane system for new CO₂Fixation and algae growth. Continuous flow or loop procedures may use parallel flow or counter-current flow of the two fluids.

Transfer of CO₂The main advantage of passing through a hydrophobic membrane is that ions cannot cross the algae culture into the collector solution. Cations contained in the algae solution include alkaline earth metals, which can create an eye-barrier along the collector solution path as the pH increases. Anions contained in the algae solution, such as nitrate and sulfate, compete with carbonate on the collector media, thereby reducing the CO of the collector media₂Capacity. Therefore, it is advantageous to prevent ions from entering the collector solution. Because the ions that make up the algae nutrients cannot cross the boundary into the collector solution, the nutrient content of the algae culture can be permanently maintained at an optimal concentration for algae growth.

In addition, the prior art discloses hydrophobic membranes, which are also organophilic and hinder the transfer of organic molecules from the algae solution to the collector solution. Any organic matter that may be transferred to the collector solution will be removed from the collector solution before it enters the collector medium. This can be accomplished, for example, by scavenging organic compounds that fall onto the ion exchange resin.

The membrane is hydrophobic, CO₂Permeability, organophobicity, and water breakthrough pressure were selected. Preferred algae for use in the process are those that grow vigorously in a carbonate solution and are able to utilize gaseous CO₂And bicarbonate. However, other algae may be used to optimize the overall process.

Referring to fig. 14, another embodiment of the present invention transfers bicarbonate across an anion permeable membrane from the collector solution 410 into the algae broth 418. The collector solution is in contact with one side of the anion permeable membrane 434 and the algae broth is in contact with the other side of the membrane.

The solution exchanges anions along a concentration gradient. To optimize the anion exchange, the solution may be run through the membrane in a counter current. The solution can also be run co-currently to optimize other parts of the system. Furthermore, the process may be configured as a batch process rather than a continuous flow process.

The algae culture solution can be fed to an anion exchange process with or without algae suspended in the solution. See fig. 15. Dissolved organic compounds can be removed from the algae cultivation solution before entering the membrane chamber.

As mentioned above, nutrients affect the application. If the entire algae culture, including algae, is fed into the membrane exchange, the nutrient concentration will be high and the collector solution will achieve a high nutrient concentration. This may lead to CO of the collector medium₂The absorption capacity is reduced by 50%. If the culture without algae is sent to the membrane exchange, the process can be set to send a nutrient depleted solution, in which case the collector capacity may be reduced by up to 20%.

The cations in the two solutions are not exchanged, which greatly reduces the possibility of creating an ocular barrier.

Furthermore, we can capture CO₂A production unit for directly injecting the algae-bib reactor synthetic fuel. One particularly simple design is to provide a paddle wheel or disc or the like carrying a moisture sensitive ion exchange resin, which is first exposed above the water surface where the CO is extracted from the air₂Then slowly rotated to partially submerge below water surface where CO is released₂To be CO₂Providing a high air/water transfer ratio.

Referring to fig. 16, in another embodiment, it is possible to spray the ion exchange resin with weakly basic wash water at the extraction station 140; similar to the first embodiment, to compensate for evaporation or production loss of water from the bioreactor. As the wash water runs down the top of the main resin, it will carry bound CO₂And dripped into the bioreactor system 142.

In addition, as shown in fig. 17, resin 142 may be added to water at night to retain CO that may be lost from algae due to respiration₂. Thereby preventing nighttime CO₂From the bioreactor release, we can improve the algae CO₂The absorption efficiency. In this embodiment, the secondary resin acts as a carbon buffer in the system. This buffer stores CO released by algae during the night₂While during the day it provides CO to the algae₂And its CO₂The content of CO collected by the air collector₂To supplement it. Once captured, CO₂The transfer to the resin is from the denser wash used in regenerating the main resin. Water filtration to keep the algae out of the air trap is generally not a problem because the main resin at the air end is designed to dry out completely between cycles.

This transfer to the secondary resin can also be accomplished without direct contact in a closed wet system, as shown in fig. 1, by performing humidity fluctuations that avoid direct contact with water. Although such systems lose the above-mentioned CO₂Bringing back to the gas phase, but it has the other advantage of buffering the algae pond at a constant pH without using chemicalsAnd (4) point.

In a preferred embodiment of the present invention, as shown in FIG. 18, to reduce water loss, increase yield and better limit algae, we employ a bioreactor 150 with a light concentrator 152. Such a system can be built up from a glass tube surrounded by a mirror or mirror system that feeds a fiber optic light pipe that can distribute light through a large liquid volume. The advantage of using bioreactors with illumination concentrators is that they greatly reduce the water surface and thus the water loss. Therefore, CO can be collected nearby₂Without directly intervening in the algae reactor. Actual air collectors may utilize mirror image systems to direct the air flow.

Algae usually fix CO during light concentration₂Breathing CO during dark periods₂. CO is added to the system at critical times by adding additional collector media₂And (4) capturing. For example, the collector media may be submerged in the algae culture. In this case, it will store bicarbonate and release carbonate as the broth pH decreases upon respiration, and it will release bicarbonate and store carbonate as the broth pH increases upon photosynthesis.

The collector medium can also be placed in the air space near the algae culture to absorb CO released from the culture solution₂. This will be particularly effective in closed configurations. The collector media placed in proximity to the culture medium can be regenerated using the methods described above.

The present application is intended to include any combination of the inorganic carbon transfer methods described in this patent, with any combination of algae cultures being utilized to optimize the method as desired. Optimization includes, but is not limited to, optimizing carbon transfer efficiency, carbon transfer rate, market value of biomass (e.g., oil content, starch content, etc.), algae production efficiency, and algae growth rate under any or controllable climate conditions.

Although moisture sensitive ion exchange resin materials have been used in combination for extracting CO from ambient air₂And through humidity fluctuation willExtracted CO₂The invention has been described in relation to a preferred embodiment for transportation to a greenhouse, and the advantages of the invention can be achieved according to several protocols described in our above-mentioned PCT applications PCT/US05/29979 and PCT/LTS06/029238 (Attore Docket Global 05.02PCT), by extracting carbon dioxide from air with an adsorbent and appropriately manipulating the adsorbent to extract CO₂Release to the greenhouse.

Claims (26)

1. A method of removing carbon dioxide from ambient air comprising the steps of contacting the ambient air with an adsorbent to absorb carbon dioxide from the air, wherein the adsorbent has a carbon dioxide retention capacity that is dependent on humidity, and releasing carbon dioxide from the adsorbent by subjecting the adsorbent to wetting or humidity fluctuations, and delivering the released carbon dioxide to a controlled environment.

2. The method of claim 1, wherein the adsorbent comprises a strongly basic, moisture sensitive ion exchange resin.

3. The method of claim 1, wherein the controlled environment is a greenhouse or a bioreactor containing an algae culture.

4. The method of claim 2 wherein the ion exchange resin is a component of a heterogeneous ion exchange membrane.

5. A process as claimed in claim 4 comprising the step of pre-treating the ion exchange membrane prior to use by first hydrating and then drying the membrane.

6. The process of claim 5 wherein the ion exchange resin comprises a strongly basic type 1 or type 2 functional ion exchange resin.

7. The method of claim 3, wherein the bioreactor has a diafiltration mechanism for entraining the released carbon dioxide into contact with the algae culture.

8. The method of claim 3, wherein the bioreactor has a headspace for carrying the released carbon dioxide into contact with the algae culture.

9. The method of claim 8, wherein the sorbent releases carbon dioxide when submerged in the algal culture.

10. The method of claim 9, wherein the algae is subsequently immersed in a nutrient solution.

11. The method of claim 1, wherein a carbon integral is generated for the removed carbon dioxide.

12. A method of extracting carbon dioxide from air comprising:

a reservoir of a first moisture sensitive adsorbent is provided,

introducing air into the first H₂Contact with the first adsorbent at partial pressure of O, at which time carbon dioxide is absorbed on the first adsorbent, and

increase H₂O partial pressure at which carbon dioxide is expelled by the first adsorbent.

13. The process of claim 12 wherein the adsorbent comprises a strongly basic type 1 or type 2 functional ion exchange resin.

14. The method of claim 12, further comprising:

allowing the first adsorbent to interact with the second adsorbent while carbon dioxide is being absorbed from the first adsorbent onto the second adsorbent; and

increase H₂O partial pressure, at which point carbon dioxide is expelled by the second adsorbent.

15. The method of claim 14, wherein the first adsorbent and the second adsorbent each comprise strongly basic type 1 and type 2 functional ion exchange resins.

16. The method of claim 14, wherein the first adsorbent and the second adsorbent are in a selectively closed loop recirculation system.

17. An apparatus for extracting carbon dioxide from ambient air comprising a reservoir of sorbent exposed to ambient air and having a humidity dependent carbon dioxide retention capacity, and means for wetting or humidity fluctuating the sorbent to release carbon dioxide from the sorbent.

18. The device of claim 17, wherein the adsorbent comprises a heterogeneous ion exchange membrane.

19. The device of claim 18, wherein the ion exchange resin of the membrane comprises a moisture sensitive ion exchange resin.

20. The device of claim 19, wherein the ion exchange resin comprises a strongly basic type 1 or type 2 functional ion exchange resin.

21. The apparatus of claim 17, further comprising means to deliver the released carbon dioxide into a greenhouse or into a bioreactor containing an algae culture.

22. The apparatus of claim 21, wherein the adsorbent is mounted on a movable fixture built into a wall of the greenhouse.

23. The apparatus of claim 21, wherein the adsorbent is near the lower end of the convection tower near the greenhouse.

24. An apparatus for removing carbon dioxide from ambient air, comprising:

an extractor comprising a humidity sensitive adsorbent for removing carbon dioxide from air;

a separation station for separating carbon dioxide and adsorbent; and

a transfer system for transferring the carbon dioxide from the extractor to the bioreactor containing the algae.

25. The apparatus of claim 24, wherein the separation station utilizes humidity fluctuations to separate the carbon dioxide and the adsorbent.

26. The apparatus of claim 24, further comprising a harvester for harvesting algae.