WO2006100667A1

WO2006100667A1 - A method for the enhanced production of algal biomass

Info

Publication number: WO2006100667A1
Application number: PCT/IL2006/000331
Authority: WO
Inventors: Aharon Eyal; Carmi Raz
Original assignee: Cargill, Incorporated A Register Delaware Corporation Of
Priority date: 2005-03-21
Filing date: 2006-03-14
Publication date: 2006-09-28
Also published as: WO2006100667B1

Abstract

The invention provides a method for the enhanced production of algal biomass with accompanying improved sequestration of carbon dioxide through photosynthesis, comprising the steps of b) providing a gaseous CO2 source; b) contacting the source with water and with a basic compound, whereby a CO2 product is generated, which CO2 product comprises at least one CO2 component, and optionally converting the CO2 product to a different CO2 product; c) forming a medium comprising algae and at least one CO2 product in which medium the generation of algal biomass for harvesting is enhanced as a function of the availability of the product; and d) harvesting generated algal biomass, whereby the algal biomass comprises carbon atoms of the CO2 product.

Description

A METHOD FOR THE ENHANCED PRODUCTION OF ALGAL BIOMASS

The present invention relates to a method for the enhanced production of algal biomass. More particularly the present invention relates to a method for the enhanced production of algal biomass with accompanying sequestration of carbon dioxide through photosynthesis.

According to the method of the present invention, algal biomass, commercial products derived from it or both are produced. According to a preferred embodiment, the algae are selected from a group consisting of algae capable of utilizing CO₂ and electromagnetic irradiation, such as natural light, e.g. solar irradiation, artificial light, IR irradiation or a combination thereof, to form a biomass. According to a preferred embodiment, the algae comprise chlorophyll. Particularly preferred are micro-algae Optionally, said algae may also use a fermentation mechanism, whereby carbohydrates are used to form algal biomass. As used herein, the term algal biomass means and includes algae, algal cells, fractions of such cells, organic matter resulting from multiplication of algae, and organic matter resulting from growth of algae.

More specifically according to the present invention there is now provided a method for the enhanced production of algal biomass with accompanying improved sequestration of carbon dioxide through photosynthesis, comprising the steps of a. providing a gaseous CO₂ source; b. contacting said source with water and with a basic compound, whereby a CO2 product is generated, which CO₂ product comprises at least one CO₂ component, and optionally converting said CO₂ product to a different CO₂ product; c. forming a medium comprising algae and at least one CO₂ product in which medium the generation of algal biomass for harvesting is enhanced as a function of the availability of said product; and d. harvesting generated algal biomass, whereby said algal biomass comprises carbon atoms of said CO₂ product. CO₂ sequestration according to known algal-based methods is of low efficiency. In such methods CO_2-containing gas is bubbled through the algal slurry, typically in a bioreactor, CO₂ dissolves in the solution and as such is consumed by the algae. The concentration of CO₂ in the solution is a function of its concentration (or partial vapor pressure) in the gas and decreases with CO₂ depletion. As a result, the rate of photosynthesis and CO₂ sequestration decreases with depletion in CO₂. Hence, achieving high sequestration yield requires large bioreactor volumes and large surfaces, which increases the cost of the bioreactor - an important component of the overall cost. Even with such costly reactors, removal yield is limited. Furthermore, the cheapest source of energy for photosynthesis is solar energy, which is efficiently available only during the clear hours of the day, in average much less than 50% of the time in most parts of the world.

According to the method of the present invention, CO₂ from the gaseous source is preferably concentrated several times in the CO₂ product. Hence, a given concentration of CO₂ in the algal medium according to the method of the present invention represents a much greater yield of CO₂ consumption by the algae compared with such concentration in presently known methods. As a result of increased CO₂ concentration in the CO₂ product, the rate of CO₂ consumption by the algae increases and the amount of CO₂ sequestered per reactor unit volume increases, whereby more CO₂ is removed in a less expensive bioreactor. In addition, contrary to the conventional method of CO₂ sequestration in algal suspension, in the method of the present invention CO₂ is absorbed in step (b) by reaction or interaction with a basic compound, which enables reducing CO₂ in the gaseous source to lower levels using smaller contactors or scrubbers. Furthermore, the method of the present invention enables sequestration of CO₂ during hours with insufficient solar irradiation, storing it in a concentrated form and making it available to the algae during light hours. The overall effect is a marked reduction of CO₂ emissions and lower costs. The same is true for the removal of NO_x, if present in the CO₂ source, where the improvement over the alternative algal sequestration is even greater than that for CO₂. NO_x removed from the source, as such or after oxidation, presents an important source of nutritional nitrogen for the algae. The method of the present invention provides maximal room for optimization and adjustment. Thus, according to a variant, step (b) is operated during hours with insufficient irradiation at lower rate, e.g. less base and, optionally, also less water. At those conditions, NO_x removal from the gaseous source (and if desired also that of SO₂) can still approach completion, while CO₂ collection and storage is adjusted to the total available irradiation. This mode of operation is particularly useful for treating flue gases in a highly populated area. According to another variant, the amount of base used during daytime is optimized to CO₂ sequestering requirements, while still maintaining high efficiency on NO_x removal. According to still another variant, CO₂ absorption in step (b) is adjusted to a desired level of CO₂ removal from the gaseous source, even if that desired level is higher than the photosynthetic capacity of the algae during most or even during any time in the year. In that case, CO₂ in the CO₂ product is used for other applications, e.g. as a source of concentrated CO₂.

The high concentration of CO₂ in the CO₂ product enables generation of algal biomass at much higher rate, thereby saving on the cost of bioreactor per unit of biomass formed.

The high concentration of CO₂ in the CO₂ product has additional advantages, such as lower pumping cost. The distance between the gaseous source, typically an energy generator, and the algal suspension could be quite large since photosynthetic algal require much area of exposure to solar irradiation for efficient photosynthetic consumption of the CO₂. In the alternative algal CO₂ sequestration method, large volumes need to be pumped. In contradistinction, in the method of the present invention, CO₂ is provided to the algae in a gaseous form, which is much more concentrated or in a form of a solution, suspension or solid absorbent, which is even more concentrated.

Still another important advantage is obviating the need to introduce (e.g. by pumping) large volumes of compounds that have no or very little contribution, mainly nitrogen, into the algae-containing medium. This difference contributes again to decreasing the cost of the bioreactor and saving on its cost per sequestration capacity and algal biomass generation capability. Water evaporation is also reduced. Additional benefits of avoiding or minimizing gaseous bubbles in the bioreactor is higher transparency of the medium, which again improves photosynthesis capacity per a given bioreactor cost.

According to a preferred embodiment, the basic compound used in step (b) is practically not consumed, apart from the cases where it forms a low-cost nutrient for growing algal biomass. In any of the alternatives of conducting the method of the present invention, after the consumption of CO₂ by the algae, the basic compound is regenerated and could be used as such, or after adjustment, again in step (b) or in any other application.

The method is characterized in that said algal biomass comprises carbon atoms present originally in said CO₂ product. The carbon atoms resulting from said CO₂ product could be present in at least one component of said algal biomass, for example cell membrane, algal organelles, hydrophilic components of the algal biomass, lipophilic components of the algal biomass, etc.

According to one embodiment, the harvested algal biomass is used as such or after some treatment such as drying, e.g. as food or feed ingredient. According to an alternative embodiment, the algal biomass comprises commercial products and those products are separated from the algal biomass. According to a preferred embodiment, said commercial product comprises carbon atoms present originally in said CO₂ product.

According to a preferred embodiment, the gaseous source contains nitrogen oxides, such as NO, NO₂ and N₂Os, referred to in the following as NO_x and said CO₂ product comprises nitrogen compounds resulting from said NO_x. Optionally, said gaseous source is oxidized prior to said contacting of step (b) or simultaneously therewith.

According to a preferred embodiment, said algal biomass, said commercial products or both comprise nitrogen atoms present originally in said CO₂ product.

According to another embodiment, the gaseous source contains SO₂ and said CO₂ product comprises sulfur compounds resulting from said SO₂. Optionally, said gaseous source is oxidized prior to said contacting of step (b) or simultaneously therewith. According to a preferred embodiment, said algal biomass, said commercial products or both comprise sulfur atoms present originally in said CO₂ product. Any gaseous CO₂ source is suitable. According to a preferred embodiment, the source is formed in a process of oxidation, e.g. burning or combusting an energy-rich material. Such oxidation preferably uses oxygen formed in algal photosynthesis, e.g. in step (c) of the method. Examples for such energy-rich material are, wood, agricultural waste, algal biomass, products of algal biomass, fossil fuel, biofuel, coal, gasoline, natural gas, mineral oil, ethanol, vegetable oil, products of such oil, fatty acids, fatty acid products, such as fatty acid methyl esters and biodiesel. According to another preferred embodiment, the gaseous CO₂ source results from a biological process, e.g. a fermentation process, such as production of ethanol. Another example of such biological process is the biological production of hydrogen from plant materials such as carbohydrates, oligosaccharides and polysaccharides. According to another preferred embodiment, the gaseous CO₂ source results from reforming of organic material. According to a preferred embodiment, the gaseous CO₂ source is formed in a process using a chemical catalyst, a biological catalyst, or both.

Optionally, if desired, the gaseous source is treated prior to said contacting in step (b), e.g. for the removal of ash particles. Another optional pretreatment is the removal of SO₂, if not desired in the CO₂ product. Such SO₂ removal may use known methods, such as contacting with a solution or a suspension of a basic material. According to a preferred embodiment of such SO₂ removal, the contacting in step (b) is conducted in two stages. In the first, SO₂ is adsorbed to form an SO₂-containing medium and an SO₂-depleted gaseous source. The latter is then contacted with water and a basic compound to form said CO₂ product.

According to a preferred embodiment, said basic compound is selected from a group consisting of basic compounds, such as carbonates, bases, such as hydroxides of alkali and alkaline-earth metals, ammonia, amines, urea, basic resins, basic zeolites, anion exchangers, basic amino acids and proteins containing basic amino acids. According to a particularly preferred embodiment, the basic compound is selected from a group consisting of ammonia, ammonium carbonate and sodium carbonate. Preferably, the basic compound has a pKa of at least 5. According to another preferred embodiment, the basic compound comprises a basic moiety, e.g. a free amino function on a protein, and said basic moiety has a pKa of at least 5. Suitable basic compounds could be water soluble, water insoluble or lipophilic. In case of water-soluble basic compounds, those compounds are preferably selected so that they may form aqueous solutions of pH greater than 5. According to another preferred embodiment, the used basic compound are ones that are less soluble or more volatile than the products of their interaction with CO₂.

According to another preferred embodiment, said CO₂ component is at least partially negatively charged. Examples of charged components are carbonates and bicarbonates. Also suitable are CO₂ products wherein said CO₂ component is only partially negatively charged, such as the product of CO₂ interaction with a relatively weak base or electron donor.

Any water is suitable for use in said step (b), including any aqueous solution. According to a preferred embodiment, the water used is an aqueous solution resulting from another step, including a recycled stream, such as a co-product of algae harvesting. Such recycled stream may comprise unutilized CO₂ component. Recycling of the CO₂ -containing stream to step (b) without loss in total CO₂ sequestration yield and thereby gaining in biomass generation rate is another advantage resulting from the contacting with a basic compound of step (b).

According to another embodiment, the water used is from a stream generated in a distillation process.

The contacting in step (b) may utilize known equipment, means, contactors and scrubbers for efficient contacting of gaseous streams with aqueous solutions, e.g. of the type used for steam treatment or steam heating of solutions. Particularly suitable are equipment and means used in removing components of flue gases, e.g., flue-gas desulfurization. According to a preferred embodiment, contacting in step (b) is conducted so that at least 10% of the CO₂ present originally in said gaseous source ends up in said CO₂ product, more preferably at least 40%, most preferably at least 60%.

According to an embodiment of the method, a gaseous stream is formed after said contacting of step (b) and is emitted to the atmosphere and said emitted stream presents reduced CO₂ emission compared with the gaseous source. According to another preferred embodiment, the gaseous source comprises NO_x and contacting in step (b) is conducted so that at least 20% of the NO_x present originally in said gaseous source forms nitrogen compounds in said CO₂ product, more preferably at least 50%, most preferably at least 70%. According to a preferred embodiment said emitted stream presents reduced NO_x emission.

According to still another preferred embodiment, the gaseous source comprises SO₂ and contacting in step (b) is conducted so that at least 30% of the SO₂ present originally in said gaseous ends up in said CO₂ product, more preferably at least 50%, most preferably at least 80%. According to a preferred embodiment said emitted stream presents reduced SO₂ emission.

In particular cases, the CO₂ product of step (b) is preferably converted to a different CO₂ product. In such cases, the CO₂ component of the CO₂ product is preferably converted to a different CO₂ component. An example for such conversion is the case where the CO₂ product comprises sodium bicarbonate and said CO₂ product is thermally treated. Said thermal treatment converts sodium bicarbonate to sodium carbonate and concentrated gaseous CO₂. Another example is reacting a CO₂ product comprising ammonium bicarbonate with a strong acid, such as phosphoric acid, whereby an ammonium salt of the acid (e.g. ammonium phosphate) and concentrated gaseous CO₂ are formed.

According to a preferred embodiment, said CO₂ product presents a concentrated source of a CO₂ component. Thus, the concentration of the CO₂ component of said CO₂ product is greater than the concentration of the CO₂ component in said gaseous source, e.g., in terms of weight per volume, by at least a factor of 1.5, preferably at least 3, more preferably at least 5.

In a further preferred embodiment the concentration of the CO₂ component of said CO₂ product is greater than the CO₂ concentration in CO₂-saturated distilled water at 2O⁰C by at least a factor of 1.5, preferably at least 3, more preferably at least 5.

The term CO₂ component as used herein, is intended to denote and include CO₂, the products of CO₂ reactions, the products of CO₂ complexation, and the products of CO₂ adsorption. Being a concentrated source of CO₂ component, said CO₂ product is a suitable means for supplying CO₂ component to growing algae. Said product provides other nutrients according to a preferred embodiment. A medium is formed, which medium comprises algae, and said CO₂ product.

According to a preferred embodiment, the medium formation involves contacting at least one of said CO₂ product with an algae-comprising aqueous system. For example, in cases where the basic compound is ammonia or ammonium carbonate, the CO₂ product may comprise an aqueous solution of ammonium bicarbonate or a mixture of ammonium carbonate and ammonium bicarbonate. Such solution could be added as such or after some treatment, e.g. concentration by reverse osmosis or by other means, to an algal suspension. That formed medium consists, in addition to a CO₂ source, a nitrogen source for the algae. Alternatively, algae are added into the aqueous solution of ammonium bicarbonate or its mixture with ammonium carbonate.

Alternative methods of forming the medium that are feasible include generating an aqueous suspension containing algae and a solid carrier of CO₂, such as the product of CO₂ adsorption on a basic carrier such as resin, cation exchanger or zeolite. According to a preferred embodiment, such carrier also serves as a medium for growing algae.

Products of CO₂ interaction with amino acids, particularly basic amino acids and products of CO₂ interaction with proteins carrying free amino functions are combined with algae according to another preferred embodiment.

Alternatively to using the CO₂ product as such, it could be modified or converted prior to the formation of the medium to a modified or a different CO₂ product. Such modification could involve purification, concentration or both, if required.

According to an alternative embodiment, the CO₂ product is treated to liberate CO₂ in a concentrated form, which concentrated form is used as a CO₂ component source for the algae. According to a preferred embodiment, the CO₂ product is contacted with an acidic compound, which contact liberates the CO₂. Any acidic compound is suitable, particularity acids with pKa smaller than about 6, such as mineral and carboxylic acids. Also suitable are acidic salts of strong acids, such as ammonium sulfate, ammonium bisulfate and ammonium nitrate. A byproduct of contacting is a salt of the basic compound used in step (b). That byproduct has a commercial value as such or after some treatment. According to a preferred embodiment, the basic compound is ammonia and the CO₂ product comprises a solution of ammonium carbonate or ammonium bicarbonate. That solution is contacted with nitric acid, phosphoric, sulfuric acid or their combination to liberate CO₂ and to form a solution of ammonium nitrate, ammonium phosphate, ammonium sulfate or a combination of those, which products are desired fertilizers. Alternatively, said CO₂ product is reacted with these or other acids to liberate CO₂ and form an ammonium salt of the reacted acid. Said salt is decomposed, according to a preferred embodiment, to regenerate ammonia for use as a basic compound in step (b) and an acid to be used for CO₂ liberation.

According to another preferred embodiment, the CO₂ product is heated to liberate CO₂. Thus, in case the basic compound used in step (b) is ammonia, ammonium carbonate, sodium carbonate or a combination thereof, the CO₂ product, which contains ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, sodium carbonate or a mixture thereof is heated, according to a preferred embodiment, to liberate CO₂ and reform a basic compound. Such reformed basic compound could be reused in step (b).

The liberated CO₂ formed by such treatments of CO₂ product is a concentrated form of CO₂, at least 1.5 times more concentrated than in the gaseous source of step (b), preferably at least 3 times, most preferably at least 5 times.

According to another embodiment, the liberated CO₂ is obtained at a pressure greater than atmospheric. Said concentrated (and optionally compressed) form of CO₂ generated from the CO₂ product is used to facilitate the generation of biomass. According to a preferred embodiment, said pressurized CO₂ product facilitates an operation selected from a group consisting of mixing, pumping, condensing and pressing. According to a particularly preferred embodiment, the pressurized CO₂ product provides for mixing in the bioreactor.

According to a preferred embodiment, the medium with the algae is formed in a bioreactor or is introduced into a bioreactor after formation. Thus, in case of generating a concentrated form of gaseous CO_2, that concentrated form is preferably bubbled into a bioreactor containing an algal suspension.

Ammonium carbonate, ammonium bicarbonate, sodium bicarbonate, sodium carbonate, their mixture or a solution thereof is preferably added to a bioreactor containing algal suspension.

According to a preferred embodiment, algae in the bioreactor are exposed to irradiation, such as UV, visible or IR irradiation. For that purpose, at least part of the bioreactor preferably consists of a transparent material, such as glass or polycarbonate. In the bioreactor a photosynthetic process takes place, using the irradiation and CO_2. As a result, algal biomass is formed.

When the amount and concentration of algae, also referred to as algal biomass, reaches a desired level, the biomass is harvested. The term harvesting as used herein refers to separation of biomass from at least part of the aqueous medium where it forms. Harvesting can use any known method, such as filtration and centrifugation. The harvesting method is preferably adjusted to the needs and characteristics of the specific algae, e.g. it is such that it maintains intact fragile cells, such as those of Dunaliella.

Algal biomass could be used as such, e.g. as a food or feed component. The algae are preferably ones which generate commercial products of higher values. According to a preferred embodiment those commercial products are selected from a group consisting of carotenoids, β-carotene astaxanthin, xanthophylls, unsaturated fatty acids, arachidonic acid, omega 3 fatty acids, glycerol and Co-Enzyme Q10.

According to a preferred embodiment, such algae are selected from a group capable of producing commercial products such as Dunaliella and Haemtococcus.

Other commercial products of interest are oil and fatty acids. Said products can be used as such, and/or are converted into fuel, such as biodiesel fuel.

As stated in some cases, the biomass with the commercial products is used as such or after some treatment, such as washing, drying or both. In other cases, the commercial products are separated from the algal biomass by methods known per se, such as extraction. While the invention will now be described in connection with certain preferred embodiments in the following examples so that aspects thereof may be more fully understood and appreciated, it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the scope of the invention as defined by the appended claims. Thus, the following examples which include preferred embodiments will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purposes of illustrative discussion of preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of formulation procedures as well as of the principles and conceptual aspects of the invention. EXAMPLES Example 1

Burning natural gas forms a gas stream containing about 15% CO₂. After cooling, the gas stream is bubbled through a column containing warm solution of about 20% sodium carbonate. More than 80% of the CO₂ in the gas stream is adsorbed in the solution converting sodium carbonate there into sodium bicarbonate. The CO₂-depleted gas stream is emitted. The sodium bicarbonate solution is heated indirectly with hot gas stream to 85⁰C. As a result, an aqueous solution of sodium carbonate and gaseous CO₂ stream are formed. The concentration of CO₂ in the formed gaseous stream is greater than 80%. The formed gaseous stream is introduced into a polycarbonate bioreactor containing micro-algae and nutrients. The bioreactor is exposed to sunlight and photosynthesis takes place. As a result, more than 80% of the CO₂ in the introduced gaseous stream is consumed and the total amount of biomass increases. Then algae suspension is pumped out of the bioreactor and biomass is separated by centrifugation. Example 2

Burning natural gas forms a gas stream containing about 15% CO₂. After cooling, the gas stream is bubbled through a column containing a 30% solution of ammonia. More than 85% of the CO₂ in the gas stream is adsorbed in the solution forming there ammonium bicarbonate. The Cθ₂-depleted gas stream is emitted. The ammonium bicarbonate solution is transferred into a pressure vessel and 50% nitric acid is added in an amount that presents 10% molar excess over the ammonium carbonate. As a result an ammonium nitrate solution is formed and CO₂ is liberated. The liberated CO₂ is separated as a gaseous stream of super-atmospheric pressure and CO2 concentration greater than 90%. The formed pressurized gaseous stream is introduced into a polycarbonate bioreactor containing micro-algae and nutrients. The bioreactor is exposed to sunlight, the pressurized CO₂ provides for mixing and photosynthesis takes place. As a result, more than 80% of the CO₂ in the introduced gaseous stream is consumed and the total amount of biomass increases. Then algae suspension is pumped out of the bioreactor and biomass is separated by centrifugation.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative examples and that the present invention may be embodied in other specific forms without departing from the essential attributes thereof, and it is therefore desired that the present embodiments and examples be considered in all respects as illustrative and not restrictive, reference being made to the appended claims, rather than to the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

WHAT IS CLAIMED IS:

1. A method for the enhanced production of algal biomass with accompanying improved sequestration of carbon dioxide through photosynthesis, comprising the steps of a) providing a gaseous CO₂ source; b) contacting said source with water and with a basic compound, whereby a CO₂ product is generated, which CO₂ product comprises at least one CO₂ component, and optionally converting said CO₂ product to a different CO₂ product; c) forming a medium comprising algae and at least one CO₂ product in which medium the generation of algal biomass for harvesting is enhanced as a function of the availability of said product; and d) harvesting generated algal biomass, whereby said algal biomass comprises carbon atoms of said CO₂ product.

2. The method of claim 1 , wherein CO₂ in said gaseous source is a product of processing a material, wherein said material is selected from a group consisting of fossil fuel, biofuel, coal, gasoline, natural gas, mineral oil, vegetable oil, ethanol, fatty acid products, biodiesel, algal biomass, products of algal biomass carbohydrates, oligosaccharides and polysaccharides.

3. The method of claim 2, wherein said processing is selected from a group consisting of oxidation, burning, combustion, fermentation and reforming.

4. The method of claim 1 , wherein said basic compound has a pKa of at least 5.

5. The method of claim 1 , wherein said basic compound is water soluble and may form aqueous solutions of pH greater than 5.

6. The method of claim 1 , wherein said CO₂ component is at least partially negatively charged.

7. The method of claim 1 , wherein the concentration of the CO₂ component of said CO₂ product is greater than the concentration of the CO₂ component in said gaseous source.

8. The method of claim 1, wherein the concentration of the CO₂ component of said CO2 product is greater than the concentration of the CO₂ component in CO₂- saturated distilled water at 2O⁰C.

9. The method of claim 1 , wherein said forming a medium comprises combining said at least one CO₂ product with an algae-comprising aqueous system.

10. The method of claim 1 , wherein said forming a medium comprises introducing algae into an aqueous system containing said at least one CO₂ product.

11. The method of claim 1 wherein said medium is formed in a bioreactor comprising at least one transparent section.

12. The method of claim 1 , wherein said algae are of photosynthetic nature.

13. The method of claim 1 , wherein said harvested algal biomass comprises a commercial product selected from a group consisting of oil, glycerol, fatty acids, unsaturated fatty acids, Omega 3 fatty acids, arachidonic acid, xanthophylls, carotenoids, β carotene and astaxanthin.

14. The method of claim 13, wherein said harvested algal biomass is processed to separate said commercial product.

15. The method of claim 13, wherein said commercial product comprises carbon atoms of said CO₂ product.

16. The method of claim 1 wherein said gaseous source further contains at least one nitrogen oxide and said CO₂ product comprises nitrogen compounds resulting therefrom.

17. The method of claim 16, wherein said algal biomass comprises nitrogen atoms originally present in said CO₂ product.

18. The method of claim 1 wherein said gaseous source further contains SO₂ and said CO₂ product comprises sulfur compounds resulting therefrom.

19. The method of claim 18, wherein said algal biomass comprises sulfur atoms originally present in said CO₂ product.

20. The method according to claim 1 wherein at least 10% of the CO₂ component originally present in said gaseous source ends up in said CO₂ product

21. The method according to claim 1 wherein at least 40% of the CO₂ component originally present in said gaseous source ends up in said CO₂ product.

22. The method according to claim 1 wherein at least 60% of the CO₂ component originally present in said gaseous source ends up in said CO₂ product.

23. The method according to claim 16 wherein at least 20% of the nitrogen compounds originally present in said gaseous source ends up in said CO₂ product.

24. The method according to claim 16 wherein at least 50% of the nitrogen compounds originally present in said gaseous source ends up in said CO₂ product.

25. The method according to claim 18 wherein at least 30% of the SO₂ originally present in said gaseous source ends up in said CO₂ product.

26. The method according to claim 18 wherein at least 50% of the SO₂ originally present in said gaseous source ends up in said CO₂ product.

27. The method according to claim 18 wherein at least 80% of the SO₂ originally present in said gaseous source ends up in said CO₂ product.

28. The method according to claim 1 wherein said basic component is selected from a group consisting of ammonia, ammonium carbonate and sodium carbonate.

29. The method according to claim 1 wherein said basic component is selected from a group consisting of ammonia, ammonium carbonate and sodium carbonate.

30. The method according to claim 1 comprising the step of converting said CO₂ product to a different CO₂ product, wherein said gaseous source is hot and wherein converting is facilitated by heating with said gaseous source.

31. The method according to claim 1 , wherein said different CO₂ product is obtained at a pressurized form.

32. The method according to claim 30, wherein said pressurized CO₂ product facilitates an operation selected from a group consisting of mixing, pumping, condensing and pressing.

33. The method according to claim 30, wherein said pressurized CO₂ product provides for mixing in that formed medium of step (c).