Diffuse Light Extended Surface Area Water-Supported Photobioreactor

• US 20080160591A1
• Filed: 10/12/2007
• Published: 07/03/2008
• Est. Priority Date: 12/28/2006
• Status: Active Grant

• Current Assignee: Colorado State University Research Foundation
• Original Assignee: Solix Biofuels Incorporated /Colorado State University Research Foundation
• Inventors: Murphy, James, Turner, Christopher, Babbitt, Guy, Weyer-Geigel, Kristina, Boczon, Amy, Ettinger, Anna, Letvin, Peter, Rancis, Nicholas, Willson, Bryan
• Granted Patent: US 9,637,714 B2
• Time in Patent Office: Days
• US Class Current: 435/132
• CPC Class Codes: C12M 21/02 Photobioreactors culturing algae A01G33/00, A01H4/001, C12N1/12
• CPC Class Codes: C12M 23/06 Tubular C12M23/08, C12M23/16 take precedence
• CPC Class Codes: C12M 23/26 flexible flexible containers for laboratory use B01L3/505
• CPC Class Codes: C12M 23/34 Internal compartments or partitions
• CPC Class Codes: C12M 23/50 Means for positioning or orientating the apparatus C12M41/08 takes precedence
• CPC Class Codes: C12M 23/58 Reaction vessels connected in series or in parallel combinations of bioreactors with other apparatus, C12M43/00
• CPC Class Codes: C12M 33/14 with filters, sieves or membranes
• CPC Class Codes: C12M 41/10 Filtering the incident radiation
• CPC Class Codes: C12M 41/22 in contact with the bioreactor walls
• CPC Class Codes: C12M 41/40 of pressure
• CPC Class Codes: C12M 43/02 Bioreactors or fermenters combined with devices for liquid fuel extraction; Biorefineries
• CPC Class Codes: C12P 7/6463 obtained from glyceride producing microorganisms, e.g. single cell oil
• CPC Class Codes: C12P 7/649 Biodiesel, i.e. fatty acid alkyl esters
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y02P 20/582 Recycling of unreacted starting or intermediate materials

Abstract

A scalable photobioreactor system for efficient production of photosynthetic microorganisms such as microalgae and cyanobacteria is described. In various embodiments, this system may include the use of extended surface area to reduce light intensity and increase photosynthetic efficiency, an external water basin to provide structure and thermal regulation at low cost, flexible plastic or composite panels that are joined together make triangular or other shapes in cross-section when partially submerged in water, use of positive gas buoyancy and pressure to maintain the structural integrity of the photobioreactor chambers and use of structure to optimize distribution of diffuse light. Other embodiments concern air tubes comprised of plastic film at the bottom of each photobioreactor chamber to provide sparging air bubbles to the chamber. The photobioreactor system design also comprises gas exchange, temperature control, air pumping, liquid pumping, filtration, media recycling and harvesting methods. For biofuels production, the photobioreactor system can comprise a separate growth photobioreactor and secondary stress reactor.

Claims

1. A closed system photobioreactor comprising one or more closed photobioreactor chambers surrounded by a water basin, said photobioreactor capable of growing photosynthetic microorganisms.

2. The photobioreactor of claim 1, wherein the photobioreactor chambers comprise a flexible, transparent plastic or composite film.

3. The photobioreactor of claim 1, wherein the photobioreactor is designed to increase photosynthetic efficiency by providing diffuse light to the photobioreactor chambers.

4. The photobioreactor of claim 1, wherein the surface area of the photobioreactor chambers that is exposed to light is greater than the surface area of land covered by the photobioreactor.

5. The photobioreactor of claim 2, wherein structural support to the photobioreactor chambers is provided by the water in the water basin, positive buoyancy air pockets in the photobioreactor chambers and/or structural heat welds in the plastic or composite film.

6. The photobioreactor of claim 1, further comprising a low-shear pump to circulate algae and growth media through the chamber.

7. The photobioreactor of claim 1, further comprising a low-shear filter.

8. The photobioreactor of claim 1, further comprising growth medium and a photosynthetic microorganism in the photobioreactor chambers.

9. The photobioreactor of claim 5, wherein the chambers are placed at an angle to each other and affixed at their tops and bottoms to neighboring chambers, to create an accordion shape from a cross-sectional view.

10. The photobioreactor of claim 1, further comprising a perimeter wall surrounding the water basin, a bottom liner below the water basin and a top layer of plastic above the water basin to decrease water loss from the water basin.

11. The photobioreactor of claim 10, wherein the water in the water basin provides a thermal mass to decrease fluctuations in temperature of the photobioreactor chambers.

12. The photobioreactor of claim 8, wherein the photosynthetic microorganism is a microalgae or cyanobacterium selected from the group consisting of, Nannochloropsis oculata, Nannochloropsis salina, Nannochloropsis sp., Tetraselmis suecica, Tetraselmis chuii, Botrycoccus braunii, Chlorella sp., Chlorella ellipsoidea, Chlorella emersonii, Chlorella minutissima, Chlorella protothecoides, Chlorella pyrenoidosa, Chlorella salina, Chlorella sorokiniana, Chlorella vulgaris, Chroomonas salina, Cyclotella cryptica, Cyclotella sp., Dunaliella salina, Dunaliella bardawil, Dunaliella tertiolecta, Euglena gracilis, Gymnodinium nelsoni, Haematococcus pluvialis, Isochrysis galbana, Monoraphidium minutum, Monoraphidium sp., Nannochloris sp., Neochloris oleoabundans, Nitzschia laevis, Onoraphidium sp., Pavlova lutheri, Phaeodactylum tricornutum, Porphyridium cruentum, Scenedesmus obliquus, Scenedesmus quadricaula Scenedesmus sp., Skeletonema, Stichococcus bacillaris, Spirulina platensis, and Thalassiosira sp.

13. The photobioreactor of claim 2, wherein the photobioreactor chamber comprises a bottom layer and a top layer of plastic film that are joined together, with an air pocket at the top of the chamber to provide positive buoyancy, wherein the shape of the photobioreactor chamber is maintained by structural tension.

14. The photobioreactor of claim 5, wherein the air pocket collects oxygen produced by photosynthesis and wherein the oxygen enriched air is collected to provide increased efficiency of combustion in a power plant or combustion chamber.

15. The photobioreactor of claim 10, wherein the top layer of plastic contains a dye, coating or additive to block the transmission of some or all ultraviolet or infrared light, while allowing transmission of visible light to support photosynthesis.

16. The photobioreactor of claim 1, further comprising one or more sensor ports, each sensor port comprising one or more sensors selected from the group consisting of a dissolved carbon dioxide sensor, a dissolved oxygen sensor, a pH sensor, a temperature sensor, a turbidity sensor, a dissolved solids sensor and a fluorometric sensor, wherein signals from the one or more sensors are fed to a central control unit.

17. The photobioreactor of claim 16, wherein the central control unit regulates the function of one or more control units to control one or more environmental conditions within the photobioreactor chambers in response to the sensor signals.

18. The photobioreactor of claim 1, further comprising a secondary bioreactor into which harvested microorganisms can be transferred and subjected to conditions to enhance lipid production.

19. The photobioreactor of claim 1, wherein volume of fluid in the the photobioreactor chamber can increase or decrease when the chamber is inoculated with a new culture.

20. The photobioreactor of claim 12, wherein multiple species of algae are maintained within the photobioreactor chamber.

21. The photobioreactor of claim 2, wherein the pressure within the photobioreactor chambers can be regulated to control the size and shape of the photobioreactor chamber.

22. A closed system photobioreactor comprising one or more closed photobioreactor chambers comprised of a flexible, transparent plastic or composite film, with an air tube comprised of plastic film at the bottom of each photobioreactor chamber to provide sparging air bubbles to the chamber.

23. The photobioreactor of claim 22, wherein the air provided to the air tube contains carbon dioxide from a source selected from atmospheric carbon dioxide, a carbon dioxide canister, the exhaust gas of a power plant or the exhaust gas of a combustion chamber.

24. The photobioreactor of claim 22, wherein the air tube is provided with a gas with an oxygen content between zero and two percent by volume, to remove dissolved oxygen from growth medium in the photobioreactor.

25. The photobioreactor of claim 23, wherein the carbon dioxide concentration can be controlled to regulate the pH of growth medium in the photobioreactor chambers.

26. A method of producing a biofuel comprising:

a. growing photosynthetic microorganisms in growth medium in a closed system photobioreactor, the photobioreactor comprising one or more closed photobioreactor chambers surrounded by a water basin;

b. harvesting the photosynthetic microorganisms in a continuous, semi-continuous or batch mode process; and

c. converting lipids or carbohydrates from the photosynthetic microorganisms into a biofuel.

27. The method of claim 26, wherein the photosynthetic microorganisms are algae.

28. The method of claim 27, wherein the algae are subjected to an environmental stress to increase lipid production.

29. The method of claim 28, wherein the algae are subjected to a combination of two or more different environmental stresses to increase lipid production.

30. The method of claim 28, wherein the environmental stress is carbon dioxide depletion.

31. The method of claim 29, wherein no carbon dioxide is provided to the photobioreactor chambers.

32. The method of claim 28, wherein the environmental stress is nitrogen depletion.

33. The method of claim 28, wherein the environmental stress is reduced or increased exposure to light.

34. The method of claim 26, further comprising providing diffuse light to the photobioreactor chambers to increase photosynthetic efficiency.

35. The method of claim 26, wherein the photosynthetic microorganism is a microalgae or cyanobacterium selected from the group consisting of, Nannochloropsis oculata, Nannochloropsis salina, Nannochloropsis sp., Tetraselmis suecica, Tetraselmis chuii, Botrycoccus braunii, Chlorella sp., Chlorella ellipsoidea, Chlorella emersonii, Chlorella minutissima, Chlorella protothecoides, Chlorella pyrenoidosa, Chlorella salina, Chlorella sorokiniana, Chlorella vulgaris, Chroomonas salina, Cyclotella cryptica, Cyclotella sp., Dunaliella salina, Dunaliella bardawil, Dunaliella tertiolecta, Euglena gracilis, Gymnodinium nelsoni, Haematococcus pluvialis, Isochrysis galbana, Monoraphidium minutum, Monoraphidium sp., Nannochloris sp., Neochloris oleoabundans, Nitzschia laevis, Onoraphidium sp., Pavlova lutheri, Phaeodactylum tricornutum, Porphyridium cruentum, Scenedesmus obliquus, Scenedesmus quadricaula Scenedesmus sp., Skeletonema, Stichococcus bacillaris, Spirulina platensis, and Thalassiosira sp.

36. The method of claim 26, wherein the photosynthetic microorganisms is Chlorella protothecoides or Tetraselmis suecica.

37. The method of claim 27, wherein multiple species of algae are maintained within the photobioreactor chamber.

38. The method of claim 26, wherein the photobioreactor chambers comprise a flexible, transparent plastic or composite film.

39. The method of claim 38, wherein the photobioreactor chambers comprise an air tube comprised of plastic film at the bottom of each photobioreactor chamber to provide sparging air bubbles to the chamber.

40. The method of claim 37, wherein the air provided to the air tube contains carbon dioxide from a source selected from atmospheric carbon dioxide, a carbon dioxide canister, the exhaust gas of a power plant or the exhaust gas of a combustion chamber.

41. The method of claim 40, wherein the carbon dioxide concentration can be controlled to regulate the pH of growth medium in the photobioreactor chambers.

42. The method of claim 26, wherein the water in the water basin provides a thermal mass to decrease fluctuations in temperature of the photobioreactor chambers.

43. The method of claim 42, further comprising providing an external source of heating or cooling to the closed system photobioreactor.

44. The method of claim 39, wherein excess gas from the air tubes and oxygen generated by photosynthesis collects in air pockets at the tops of the photobioreactor chambers.

45. The method of claim 44, further comprising removing the oxygen enriched gas from the air pockets to improve the efficiency of combustion in a power plant or combustion chamber.

46. The method of claim 44, further comprising venting the gas from the air pockets at one end of the closed system photobioreactor.

47. The method of claim 44, further comprising venting the gas from the air pockets along the length of the closed system photobioreactor to reduce oxygen concentration in the growth medium.

48. The method of claim 46, wherein the exhaust gas is vented under water.

49. The method of claim 48, further comprising regulating the gas pressure in the closed photobioreactor chambers by the depth below the water surface of the exhaust gas vent.

50. The method of claim 26, further comprising pumping growth medium through the photobioreactor chambers, wherein the growth medium leaves the photobioreactor at one end and is pumped to the other end of the photobioreactor to create a unidirectional current through the photobioreactor chambers.