High yield algal biomass production without concentrated CO2 supply under open pond conditions

• US 10,457,909 B2
• Filed: 04/27/2017
• Issued: 10/29/2019
• Est. Priority Date: 04/27/2016
• Status: Active Grant

• Current Assignee: University of Toledo
• Original Assignee: University of Toledo
• Inventors: Pendyala, Brahmaiah, Vadlamani, Agasteswar, Viamajala, Sridhar, Varanasi, Sasidhar, Hanifzadeh, Mohammadmatin
• Primary Examiner(s): Ware, Deborah K
• Application Number:
  US15/498,621
• Publication Number:
  US 20170313972A1
• Time in Patent Office: 915 Days
• CPC Class Codes: A01G 33/00 Cultivation of seaweed or algae
• CPC Class Codes: C10L 1/02 essentially based on components consisting of carbon, hydrogen, and oxygen only
• CPC Class Codes: C10L 2200/0469 Renewables or materials of biological origin
• CPC Class Codes: C10L 2290/04 Gasification
• CPC Class Codes: C10L 2290/06 Heat exchange, direct or indirect
• CPC Class Codes: C10L 2290/26 Composting, fermenting or anaerobic digestion fuel components or materials from which fuels are prepared
• CPC Class Codes: C12M 21/02 Photobioreactors culturing algae A01G33/00, A01H4/001, C12N1/12
• CPC Class Codes: C12M 23/18 Open ponds; Greenhouse type or underground installations
• CPC Class Codes: C12N 1/12 Unicellular algae; Culture media therefor as new plants A01H13/00
• CPC Class Codes: Y02A 40/80 in fisheries management
• CPC Class Codes: Y02P 60/20 Reduction of greenhouse gas [GHG] emissions in agriculture, e.g. CO2

Abstract

Methods and systems for efficient culturing of algae in open ponds. Further, the methods include a method for culturing algae in an open pond medium that is free of any concentrated supply of CO₂, and no concentrated source of CO₂ is used to supply carbon for culturing the algae. Also, the algae are cultured in the open pond which has a pH above 9.5. In addition, the open pond medium has incorporated therein an inorganic carbon buffer at a specified concentration under conditions for obtaining an increased biomass. Also, the pH above 9.5 permits sufficient increased fixation of atmospheric CO2 into the open pond medium.

Claims

1. A method for culturing algae, the method comprising:

culturing alkaliphilic algae in an open pond medium having a pH above 9.5, sufficient to allow increased fixation of atmospheric CO₂ into the open pond medium; and

incorporating into the open pond medium an inorganic carbon buffer, wherein the inorganic carbon buffer comprises HCO₃⁻

present at a concentration ranging from 4.5 mM to 60 mM and the open pond medium has a salinity in the range of from about 10 g/L to about 30 g/L and an alkalinity of up to about 1 M;

wherein the open pond medium is free of any concentrated supply of CO₂, and no concentrated source of CO₂ is used to supply carbon for culturing the alkaliphilic algae.

2. The method of claim 1, wherein the inorganic carbon buffer comprises either a NaHCO₃/Na₂CO₃ mixture or a KHCO₃/K₂CO₃ mixture.

3. The method of claim 2, wherein the NaHCO₃/Na₂CO₃ mixture or the KHCO₃/K₂CO₃ mixture is incorporated into the open pond medium at a concentration ranging from about 7 mM to about 60 mM.

4. The method of claim 1, wherein the pH of the open pond medium is at least about 9.9.

5. The method of claim 1, further comprising incorporating glucose or other sugars or carboxylic acids into the open pond medium.

6. The method of claim 1, wherein the algae comprise a Chlorella sp., Dunaliella sp., Synechocystic sp., Cyanothece sp., Microcoleus sp., Euhalothece sp., or Spirulina sp. strain.

7. The method of claim 1, further comprising incorporating Ca and/or Mg into the open pond medium at a concentration of less than 7 mg/L.

8. The method of claim 7, wherein the Ca is incorporated into the open pond medium at a concentration of less than 1.5 mg Ca/L.

9. The method of claim 7, wherein the Mg is incorporated into the open pond medium at a concentration of less than 0.5 mg Mg/L.

10. The method of claim 1, further comprising circulating the algae within the open pond medium.

11. The method of claim 1, further comprising harvesting biomass from the cultured algae and recovering remnant media.

12. The method of claim 11, further comprising recycling the remnant media in a second open pond medium.

13. The method of claim 11, further comprising converting the harvested biomass to one or more fuels.

14. The method of claim 13, wherein the converting comprises hydrothermal liquefaction to produce biocrude having a N content of less than 4%.

15. The method of claim 1, further comprising regulating nitrogen input in the open pond medium, in a range from about 5 mg/L to about 27 mg/L, so as to modulate the biochemical composition of the algae.

16. The method of claim 1, wherein the pH of the open pond medium is greater than 10.0.

17. The method of claim 1, wherein the alkaliphilic algae comprise eukaryotic microalgae.

18. A method for culturing algae, the method comprising:

culturing alkaliphilic algae in an open pond medium having a pH above 9.5, sufficient to allow increased fixation of atmospheric CO₂ into the open pond medium; and

incorporating into the open pond medium an inorganic carbon buffer, wherein the inorganic carbon buffer comprises HCO₃⁻

present at a concentration ranging from 4.5 mM to 60 mM and the open pond medium has a salinity in the range of from about 10 g/L to about 30 g/L and an alkalinity of up to about 1 M;

wherein the open pond medium is free of any concentrated supply of CO₂, and no concentrated source of CO₂ is used to supply carbon for culturing the alkaliphilic algae, the method using atmospheric CO₂ alone.

19. A method for culturing an alkaliphilic algal strain, the method comprising:

culturing the alkaliphilic algal strain, the algal strain comprising microalgae or cyanobacteria, in an open pond medium having a pH above 9.5, sufficient to allow increased fixation of atmospheric CO₂ into the open pond medium, and a salinity in the range of from about 10 g/L to about 30 g/L, free of any concentrated supply of CO₂, and no concentrated source of CO₂ is used to supply carbon for culturing the alkaliphilic algal strain;

incorporating into the open pond medium an inorganic carbon buffer at a total alkalinity ranging from about 3 mM to about 1 M;

regulating nitrogen input in the open pond medium, in a range from about 5 mg/L to about 25 mg/L; and

recovering the cultured algal strain.