High Yield Algal Biomass Production Without Concentrated CO2 Supply Under Open Pond Conditions

• US 20170313972A1
• Filed: 04/27/2017
• Published: 11/02/2017
• 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
• Granted Patent: US 10,457,909 B2
• Time in Patent Office: 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 are described.

Claims

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

culturing alkaliphilic algae in an open pond medium having a pH above 9.5; and

incorporating into the open pond medium an inorganic carbon buffer sufficient to allow increased fixation of atmospheric CO₂ into the open pond medium;

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

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 1 M.

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 microalgae.

16. The method of claim 1, wherein the open pond medium has a salinity in the range of from about 10 g/L to about 30 g/L, a pH greater than 10.0, and an alkalinity of up to about 1 M.

17. The method of claim 1, further comprising improving phycocyanin production by increasing one or more of biomass concentration, nitrogen concentration, and salinity in the open pond medium.

18. An open pond system comprising:

a medium having a pH above 9.5 and exposed to solar radiation;

an inorganic carbon buffer in the medium; and

alkaliphilic algae in the medium;

wherein the open pond system is free from any unnatural or concentrated CO₂ supply.

19. The open pond system of claim 18, further comprising an organic substrate comprising glucose or other sugars or carboxylic acids in the medium.

20. The open pond system of claim 18, wherein the inorganic carbon buffer comprises either a NaHCO₃/Na₂CO₃ mixture or a KHCO₃/K₂CO₃ mixture present at a concentration ranging from about 7 mM to about 1 M.

21. The open pond system of claim 18, wherein the alkaliphilic algae comprises a Chlorella sp., Dunaliella sp., Synechocystic sp., Cyanothece sp., Microcoleus sp., Euhalothece sp., or Spirulina sp. strain.

22. The open pond system of claim 18, further comprising a water-moving device configured to circulate the medium within the open pond system.

23. The open pond system of claim 18, wherein the medium further comprises Ca and/or Mg at a concentration of less than 7 mg/L.

24. The open pond system of claim 18, wherein the medium further comprises one or more nutrients selected from the group consisting of:

NaNO₃, MgSO₄, CaCl₂, NaCl, ferric ammonium citrate, H₃BO₃, MnCl₂, ZnCl₂, CuCl₂, Na₂MoO₄, CoCl₂, NiCl₂, V₂O₅, and KBr.