High yield algal biomass production without concentrated CO
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 CO 2 , and no concentrated source of CO 2 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.
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 CO 2 into the open pond medium; and
incorporating into the open pond medium an inorganic carbon buffer, wherein the inorganic carbon buffer comprises HCO 3 − 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 CO 2 , and no concentrated source of CO 2 is used to supply carbon for culturing the alkaliphilic algae.
2. The method of claim 1 , wherein the inorganic carbon buffer comprises either a NaHCO 3 /Na 2 CO 3 mixture or a KHCO 3 /K 2 CO 3 mixture.
3. The method of claim 2 , wherein the NaHCO 3 /Na 2 CO 3 mixture or the KHCO 3 /K 2 CO 3 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 CO 2 into the open pond medium; and
incorporating into the open pond medium an inorganic carbon buffer, wherein the inorganic carbon buffer comprises HCO 3 − 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 CO 2 , and no concentrated source of CO 2 is used to supply carbon for culturing the alkaliphilic algae, the method using atmospheric CO 2 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 CO 2 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 CO 2 , and no concentrated source of CO 2 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.