WO2006127512A1

WO2006127512A1 - Biofuel production

Info

Publication number: WO2006127512A1
Application number: PCT/US2006/019560
Authority: WO
Inventors: Aharon Eyal; Ian C. Purtle
Original assignee: Cargill, Incorporated
Priority date: 2005-05-20
Filing date: 2006-05-22
Publication date: 2006-11-30

Abstract

A method for biofuel production is disclosed. The method includes providing a first photosynthesis product. The method also includes processing the first photosynthesis product to form a product mixture comprising a first biofuel and CO2. The method also includes separating CO2 from the product mixture. The method also includes growing biomass in a photosynthesis process, which biomass comprises a second photosynthesis product. The method also includes providing CO2 to the growing biomass, wherein at least part of the CO2 is consumed in the photosynthesis process. The method also includes optionally harvesting the grown biomass.

Description

BIOFUEL PRODUCTION

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and incorporates by reference U.S. Patent Application No. 60/683041 titled "Biofuel Production and Sequestration System" filed May 20, 2005.

FIELD OF THE INVENTION

The present invention generally relates to a biofuel production system. The present invention more particularly relates to a method for producing ethanol with reduced CO₂ emissions to the atmosphere.

BACKGROUND OF THE INVENTION

It is generally known to convert raw biological material (e.g. plants, cane sugar, wood pulp) to fuel (i.e. "biofuel") through fermentation. However, converting photosynthesis products to a biofuel typically forms CO₂ as a co- product, which decreases biofuel production yield and may increase CO₂ emissions to the atmosphere. Accordingly, there is a need for a biofuel production method that provides for a relatively high yield of biofuel. There is also a need for a biofuel production method that reduces the availability of CO₂ to the atmosphere. It would be advantageous to provide a biofuel production system filling any one or more of these needs or having other advantageous features.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a method for biofuel production. The method includes providing a first photosynthesis product. The method also includes processing the first photosynthesis product to form a product mixture comprising a first biofuel and CO₂. The method also includes separating CO₂ from the product mixture. The method also includes growing biomass in a photosynthesis process, which biomass comprises a second photosynthesis product. The method also includes providing CO₂ to the growing biomass, wherein at least part of the CO₂ is consumed in the photosynthesis process. The method also includes optionally harvesting the grown biomass.

The present invention also relates to a method for the production of biofuel. The method includes providing a first photosynthesis product. The method also includes processing the first photosynthesis product to form a product mixture comprising a first biofuel and CO2. The method also includes separating CO₂ from the product mixture. The method also includes growing biomass in a photosynthesis process, which biomass comprises a second photosynthesis product. The method also includes providing CO₂ from 0 the growing biomass, wherein at least part of the CO₂ is consumed in the photosynthesis process. The method also includes harvesting grown biomass. The method also includes processing at least part of the second photosynthesis product to form a product mixture comprising a second biofuel.

The invention will now be described in connection with certain preferred and alternative embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the 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 the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a flow diagram of biofuel production and CO₂ sequestration according to an exemplary embodiment of the present invention.

FIGURE 2 is a flow diagram of biofuel production and CO₂ sequestration according to an alternative embodiment of the present invention.

FIGURE 3 is a flow diagram of biofuel production and CO₂ sequestration according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED AND OTHER EXEMPLARY EMBODIMENTS An exemplary method of the present invention is described in the following with reference to figures. Referring generally to the figures, a plant material (e.g. corn) is processed to yield a first product (e.g. oil) and a second product (e.g. starch). The second product (e.g. starch) is fermented to yield a biofuel (e.g. ethanol). Fermentation creates a bi-product, specifically carbon dioxide (CO₂). In conventional systems, such CO₂ is emitted to the atmosphere. According to a preferred embodiment of the present invention, such bi-product CO₂ is used in a photosynthesis process to create a carbon sink (e.g. algae) or natural environment that absorbs and stores CO₂. Such carbon sink may be a biomass used as a fuel or energy source. According to a preferred embodiment of the invention, such biomass is used as a fermentation product to yield biofuel (e.g. ethanol).

Referring to Figure 1 ,a schematic flow diagram of an embodiment of the invention is shown. A plant material 8 (e.g. com) undergoes a processing step (operation 10) to yield a first product 12 (e.g. oil) and a fermentable product 14 (e.g. a product that is capable of being fermented such as starch, carbohydrate, glucose, sucrose, etc.) Suitable plants for the fermentable product include starch ones, such as com, wheat, potato and rice and sucrose crops such as sugar cane and sugar beet, lignocellulosics, etc. and plant materials such as various parts of the plant such as corn and wheat kernels, corn stalk, straw, etc. Known methods and their combinations are suitable for the production of the fermentable, e.g. dry milling, of corn, wet milling of corn and combinations of those, wheat milling, starch hydrolysis and saccharification, processing of sugar cane, sugar beet, processing of lignocellulosics (e.g. via hydrolysis), processing of dairy products, etc. Also suitable are products of processing such plants, e.g. products of corn dry milling and corn wet milling, such as steeped corn, corn endosperm, corn or wheat starch, debranned corn or wheat, bran, fiber, orange peel, etc.

Referring further to Figure 1 , fermentable product 14 is fermented (operation 20) to yield a fermentation product 22 (e.g. ethanol-containing aqueous stream, lactic acid, formic acid, acetic acid, hydrogen, butanediol, etc.) and a fermentation byproduct 24 (e.g. CO₂). Fermentation product 22 and fermentation byproduct 24 (e.g. CO₂) are separated (operation 20). Fermentation product 22 (e.g. ethanol-containing aqueous stream) is further treated in a separation operation (30) to yield a biofuel 32 (e.g. ethanol). Separation could use known means such as distillation. If desired, azeotropic ethanol formed by distillation is further dried, e.g. on molecular sieve.

Referring further to Figure 1 , fermentation byproduct 24 (e.g. CO₂) is provided, optionally along with additional CO₂ from other sources, such as atmospheric CO₂ and CO₂ from combustion (26), and/or irradiation (28) to a step of photosynthesis growth (operation 40). In the growth step, the CO₂ is sequestered and transformed into a carbon sink or biomass, rather than being emitted to the atmosphere. According to a preferred embodiment, the grown biomass is algal biomass, e.g. micro-algae or macro-algae. According to a preferred embodiment, the grown biomass is harvested and used, e.g. for feed. Thus, it is believed that the process of Figure 1 generates biofuel (e.g. ethanol), and possibly other products with less CO₂ emission compared to conventional ethanol-producing processes.

Figure 2 is a schematic flow diagram of an alternative embodiment of the invention. In a photosynthesis process (140) a fermentable product which is also a biomass 142 (e.g. carbohydrate-containing algal biomass) is grown, for example using CO₂ (126) and irradiation (128). The biomass 142 is harvested and processed (150), optionally together with another fermentable product or carbohydrate source, e.g. carbohydrate from a plant source (144), producing as one of the products a fermentable carbohydrate stream (152). The carbohydrate stream 152 is fermented in operation (120). Fermentation results in a fermentation byproduct 124 (e.g. CO₂) and in a fermentation product 122 (e.g. ethanol-containing aqueous solution), which are separated (operation 120). The fermentation product 122 (ethanol-containing aqueous stream) is further treated in operation (130) to separate biofuel 132 (e.g. ethanol). According to a preferred embodiment, the fermentation byproduct 124 (e.g. CO₂) is also provided to the photosynthesis process of step (140) to be converted into biomass 142. According to a preferred embodiment, the biomass is an algal biomass and fermentation of the biomass is intracellular, e.g. dark fermentation. According to a preferred embodiment, the biomass is concentrated prior to dark fermentation in order to generate a concentrated product. Optionally the biomass is reused after the dark fermentation to sequester more CO₂ and generate more carbohydrate. According to a preferred embodiment, the fermentation liquor produced during extracellular fermentation and/or intracellular fermentation to ethanol is treated for ethanol separation in operation (130) along with stream (122).

Figure 3 is a schematic flow diagram of a preferred embodiment of the invention. A fermentable product stream 214 (e.g. carbohydrate) from a plant source (208) and a fermentable product stream 252 (e.g. carbohydrate) from a carbon sink or biomass source (252) (e.g. algae) are provided and the fermentable products 214 and 252 are fermented in operation (220). The fermentation results in a fermentation byproduct 224 (e.g. CO₂) and in a fermentation product 222 (e.g. ethanol-containing aqueous solution), which are separated (operation 220). Fermentation product 222 (e.g. ethanol-containing aqueous stream) is further treated in operation (230) to separate biofuel 232 (e.g. ethanol). Separated fermentation byproduct 224 (e.g. CO₂) is provided, optionally along with additional CO₂ from another source, e.g. atmospheric CO₂ and product of combustion (226) (including flue gas), and with irradiation (228) to a step of photosynthesis growth of a carbon sink or biomass 242 (e.g. carbohydrate- containing algal biomass) in operation 240). In the growth step, the CO2 is sequestered and transformed into biomass, rather than being emitted to the atmosphere. The grown algal biomass 242 is harvested and processed (operation 240), producing as one of the products a fermentable product (252) to be used in the fermentation (operation 220).

Any carbohydrate-producing algae are suitable for the purpose of the present invention. Many algae convert in a photosynthesis process water and CO₂ into starch. The starch is a storage carbohydrate and is stored in the algae in the form of granules. Those granules are similar in nature to those in starchy crops, such as corn. Biomass processing (operations 150 and 250 in Figures 2 and 3, respectively) may involve extraction of starch granules, optionally liberating it from cell membrane by sonication or solvent treatment. The starch granules are hydrolyzed chemically (acid catalyzed), enzymatically (e.g. using amylase and/or glucoamylase) or a combination of those to form a carbohydrate solution to be fermented. According to a preferred embodiment, processing of algal-biomass- resulting starch is combined with processing of plant starch. In a particularly preferred embodiment, operation 10 or 210 involves processing of corn, wheat or another starch crop, which generates starch granules from the plant material and that starch is hydrolyzed along with algal starch granules to form the carbohydrate stream for fermentation.

According to alternative embodiments, the biomass produced according to the present invention, e.g. algal biomass, can be processed to generate commercial products in addition to (or instead of) carbohydrate streams for fermentation to ethanol (and/or to other products). Those commercial products could be separated from the algal biomass prior to processing into a carbohydrate stream, simultaneously with that processing or from a residue left after carbohydrate separation. According to a preferred embodiment, biofuel is produced. Such biofuel may include products such biodiesel (e.g. fatty acid methyl esters produced from oil content of the biomass), biohydrogen and biofuel produced via pyrolysis of biomass fractions. Alternatively, or in addition, fractions of the algae are burned for thermal energy. Such thermal energy and optionally also thermal energy produced by combusting plant material and generated biofuel is used, according to a preferred embodiment, to provide processing energy. Processing energy could be used in operations such as processing of plant material to form carbohydrate stream, processing biomass, separation of ethanol, etc. CO₂ formed in such combustion is preferably provided to the photosynthesis (operations 40, 140 and 240 in Figures 1 , 2, and 3, respectively).

According to another preferred embodiment, the algal biomass comprises a commercial product selected from a group consisting of oil, glycerol, fatty acids, unsaturated fatty acids, omega3 fatty acids, arachidonic acid, xanthophylls, carotenoids, beta-carotene and astaxanthin. According to a preferred embodiment, at least one of those commercial products is separated from the algal biomass. Separation may use known methods and be conducted prior to the production of a carbohydrate stream, simultaneously with it or after such production.

According to a preferred embodiment, algal biomass is grown in a bioreactor into which CO₂ is provided. Also introduced into the bioreactor is irradiation, which could be solar irradiation, artificial irradiation, irradiation from combustion, selected fractions of those and/or irradiation from any other source with irradiation wavelength suitable for the selected algae. According to another preferred embodiment, suitable nutrients are provided to the growing algal biomass, including e.g. nitrogen and phosphorous sources. Complex nutrients such as steep liquor and yeast extract might be desired for some of the algae. According to a preferred embodiment, those are supplied from internal sources, such as ashes from in combustion of algal residues or other plant material, corn- steep liquor (particularly in cases where the process is run next to corn milling plant and residues of ethanol distillation). Such nutrients are used, according to another preferred embodiment in the fermentation process. The algae biomass produced in the photosynthesis process is typically harvested prior to processing. Harvesting uses known methods for separation of microalgae or microalgae from aqueous growth medium, such as filtration and centrifugation.

According to an exemplary process of the present invention, the CO₂ formed in the fermentation (49% of the weight of the fermented glucose) will be consumed in the photosynthesis process and partially converted to carbohydrate in an algal biomass. That biomass is processed for carbohydrate recovery and the recovered carbohydrate is fermented to ethanol. Furthermore, the algal carbohydrate yield could be further increased by providing to the photosynthesis step CO₂ from other sources, including CO₂ produced in combustion. In a particularly preferred embodiment, the process of the present invention is operated next to processing plant material. Such processing and the ethanol separation require energy, which could be obtained by burning fuel such as natural gas and plant parts. The CO₂ produced in such burning of fuel is provided to the growth of the carbohydrate-containing algal biomass. According to a preferred embodiment, algae biomass, e.g. fractions that do not end up in the carbohydrate stream, and optionally also some of the ethanol provide such fuel. Algal biomass could be burned for that purpose or biologically digested to form methane, which is then used.

According to a preferred embodiment, at least one of the provided (first) photosynthesis products and the biomass-contained (second) photosynthesis product comprises at least one of simple carbohydrates, such as glucose, xylose, arabinose and sucrose, oligosaccharides and poly saccharides, such as starch, cellulose and hemicellulose, lignin, pectin, natural polymeric compounds, triglycerides, phospholipids, their combinations, products of their processing and products of their degradation, processing and/or hydrolysis.

According to a preferred embodiment, providing a photosynthesis product comprises processing a lignocellulosic material and/or biomass, such as wood, straw, stalk, corn cobs, switch grass, recycled paper, byproducts of food/feed production, etc. The main components of such lignocellulosic material are cellulose, hemicellulose and lignin. Processing could involve hydrolysis of the hemicellulose and cellulose fractions.

According to a preferred embodiment, processing at least one of the provided (first) photosynthesis products and the biomass-contained (second) photosynthesis product comprises at least one of chemically-catalyzed reactions, biologically-catalyzed reactions, enzymatically-catalyzed reaction, biological processing, fermentation, anaerobic fermentation, pyrolysis, reforming and trans- esterification.

According to a preferred embodiment, at least one of the first biofuel and the second biofuel is selected from a group consisting of ethanol, methane, hydrogen, biodiesel and a combination thereof.

According to a preferred embodiment, the second biofuel is ethanol. According to another preferred embodiment, both reaction products comprise ethanol.

According to a preferred embodiment, the second biofuel is similar to the first biofuel. According to a variant of this preferred embodiment, processing at least part of the first carbohydrate and processing at least part of the second photosynthesis product are combined.

Alternatively, the first biofuel comprises methane, e.g. as formed in anaerobic fermentation, and the second biofuel comprises ethanol. According to another alternative the first biofuel comprises hydrogen, e.g. as formed by fermentation, reforming, etc., and the second biofuel comprises ethanol. According to still another alternative, the second biofuel comprises biodiesel, such as fatty acid methyl esters, e.g. as formed by a trans-esterification reaction between triglycerides and methanol.

According to a preferred embodiment, CO≥ formed in processing the second photosynthesis product is also consumed by the grown biomass. It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by 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 biofuel production, comprising the steps of: a. providing a first photosynthesis product; b. processing the first photosynthesis product to form a product mixture comprising a first biofuel and CO₂; c. separating CO₂ from the product mixture; d. growing biomass in a photosynthesis process, which biomass comprises a second photosynthesis product; e. providing CO₂ from step (c) to the growing biomass, wherein at least part of the CO₂ is consumed in the photosynthesis process; and f. optionally harvesting the grown biomass.

2. The method of Claim 1 , further comprising the step of processing the second photosynthesis product to form a product mixture comprising a commercial product.

3. The method of Claim 2, wherein at least one of the processing of the first photosynthesis product and processing the second photosynthesis product comprises at least one processing step involving chemical catalysis, biological catalysis, enzymatic catalysis, biological processing, fermentation, anaerobic fermentation, pyrolysis and reforming.

4. The method of Claim 2, wherein the commercial product comprises at least one of ethanol, formic acid, acetic acid, lactic acid, hydrogen, butanediol and their combinations.

5. A method for the production of biofuel, comprising the steps of: a. providing a first photosynthesis product; b. processing the first photosynthesis product to form a product mixture comprising a first biofuel and CO₂-, c. separating CO₂ from the product mixture; d. growing biomass in a photosynthesis process, which biomass comprises a second photosynthesis product; e. providing CO₂ from step (c) to the growing biomass, wherein at least part of the CO₂ is consumed in the photosynthesis process; f. harvesting grown biomass; and g. processing at least part of the second photosynthesis product to form a product mixture comprising a second biofuel.

6. The method of claim 5, wherein at least one of the first biofuel and the second biofuel comprises at least one of ethanol, methane, hydrogen, biodiesel and a combination thereof.

7. The method of claim 5, where the second biofuel comprises ethanol.

8. The method of claim 5, where both the first biofuel and the second biofuel comprises ethanol.

9. The method of claim 5, where the first biofuel comprises methane and the second biofuel comprises ethanol.

10. The method of claim 5, where the first biofuel comprises hydrogen and the second biofuel comprises ethanol.

11. The method of claim 5, where the second biofuel comprises biodiesel.

12. The method of Claim 5, wherein the product mixture formed from processing the second photosynthesis product comprises CO₂, and the method further comprises the steps of separating the CO₂ and providing it to the growing biomass, wherein at least part of the provided CO₂ is consumed in the photosynthesis process.

13. The method of Claim 5, wherein the grown biomass comprises algal biomass.

14. The method of Claim 5, wherein the provided first photosynthesis product comprises at least one of plant material, algal biomass, their combinations, products of their processing and product of their degradation.

15. The method of Claim 5, wherein at least one of the first photosynthesis products and the second photosynthesis products comprises at least one of carbohydrates, starch, hemicellulose, cellulose, triglycerides, phospholipids, their combinations and degradation products thereof.

16. A method for ethanol production, comprising the steps of: a. processing plant material to generate a carbohydrate stream; b. processing carbohydrate-containing algal biomass to generate a carbohydrate stream; c. providing a combined carbohydrate stream comprising carbohydrate from both the plant source of step (a) and the algal source of step

(b); d. fermenting carbohydrates resulting from the combined carbohydrate stream to form a product mixture comprising ethanol and CO₂; and e. separating CO₂ from the product mixture.

17. A method for ethanol production, comprising the steps of: a. providing a carbohydrate stream; b. fermenting carbohydrates resulting from the carbohydrate stream to form a product mixture comprising ethanol and CO₂; c. separating CO₂ from the product mixture of step (b); d. growing biomass in a photosynthesis process; e. providing CO₂ from step (c) to the growing biomass wherein at least a portion of the CO₂ is consumed in the photosynthesis process; wherein providing the carbohydrate stream of step (a) comprises the steps of: f. harvesting biomass from step (e); and g. processing harvested biomass from step (f).

18. The method of Claim 17, wherein the grown biomass comprises algal biomass.

19. The method of Claim 17 wherein the provided carbohydrate stream comprises carbohydrate from a plant source.

20. A method for CO₂ sequestration and ethanol production, comprising the steps of: a. processing plant material to generate a carbohydrate stream; b. processing carbohydrate-containing algal biomass to generate a carbohydrate stream; c. providing a combined carbohydrate stream comprising carbohydrate from both the plant source of step (a) and the algal source of step (b); d. fermenting carbohydrate resulting from the stream provided in (c) to form a product mixture comprising ethanol and CO_2; e. separating CO₂ from the product mixture of step (d); f. growing carbohydrate containing algal-biomass in a photosynthesis process; g. providing CO₂ from step (e) to the growing algal-biomass wherein at least a portion of the CO₂ is consumed in the photosynthesis process; h. harvesting algal biomass grown in step (g); and wherein the carbohydrate-containing algal biomass processed in step (b) results at least partially from the harvested biomass of step (h).

21. The method of claim 20, wherein the plant is selected from starchy plants, sugar cane and sugar beet.

22. The method of claim 21 , wherein the starchy plant comprises at least one of com, wheat, rice, and potatoes.

23. The method of Claim 20, further comprising a step of processing harvested biomass to generate at least one of biofuel, thermal energy, nutrients, CO₂ and commercial products.

24. The method of claim 23, wherein a generated nutrient is used in at least one of growing biomass, growing algal biomass and fermenting.

25. The method of Claim 20, wherein ethanol is produced, and further comprising the step of separating ethanol from the product mixture.

26. The method of claim 23, wherein the generated thermal energy is used in at least one of providing a carbohydrate stream, processing a plant material, processing of biomass and separating ethanol.

27. The method of claim 20, wherein the generated CO₂ is used in growing biomass.

28. A method for CO2 sequestration and for the production of biofuel and a commercial product, comprising the steps of: o a. providing a first photosynthesis product; b. processing the first photosynthesis product to form a product mixture comprising a biofuel and CO2; c. separating CO2 from the product mixture; d. growing biomass in a photosynthetic process, which biomass comprises s a second photosynthesis product; e. providing CO2 from step (c) to the growing biomass wherein at least part of the CO2 is consumed in said photosynthesis process; f. harvesting grown biomass; and g. processing at least part of said second photosynthesis product to form a o product mixture comprising a commercial product.

29. The method of Claim 29, wherein the biofuel is ethanol.