Methods for harvesting microalgae
View Patent ↗Methods for harvesting microalgae, comprise providing water containing microalgae, providing flocculant in an amount to form flocs of microalgae when mixed with the water, generating a mixture of the water and the flocculant and separating the flocs from the mixture.
1. A method for harvesting microalgae, the method comprising
providing water comprising microalgae,
wherein the water has a pH between about 6.0 and about 10.0 and has a salinity between about 0.01% and about 5%;
providing chitosan in an amount sufficient to form flocs of microalgae when mixed with the water;
generating a mixture of the water and the chitosan, wherein the mixture is acidic; and
separating the flocs from the mixture, thereby harvesting the microalgae.
2. The method of claim 1 , wherein the water has a pH between about 8.0 and about 9.0.
3. The method of claim 1 , wherein the water has a salinity of about 2.2%.
4. The method of claim 1 , wherein the water comprises sodium hydrogen carbonate at a concentration between about 0.01 g/L and about 0.5 g/L.
5. The method of claim 4 , wherein the water comprises sodium hydrogen carbonate at a concentration between about 0.1 g/L and about 0.2 g/L.
6. The method of claim 1 , wherein the water is at a temperature between about 10° C. and about 38° C.
7. The method of claim 1 , wherein the chitosan is provided at a concentration between about 0.08% and about 3.5% of the weight of the microalgae in the mixture.
8. The method of claim 1 , wherein the chitosan is provided at about 2% of the weight of the microalgae in the mixture.
9. The method of claim 1 , wherein the method comprises adding flue gas or wherein the water is mixed with flue gas.
10. The method of claim 9 , wherein the flue gas comprises carbon dioxide.
11. The method of claim 9 , wherein the flue gas has less than 5 ppm of sulfur oxide.
12. The method of claim 9 , wherein the flue gas comprises carbon dioxide at a concentration between about 4% and about 20%.
13. The method of claim 9 , wherein the flue gas comprises carbon dioxide at a concentration between about 10% and about 14%.
14. The method of claim 1 , wherein the mixture has a pH between about 4.5 and about 6.5.
15. The method of claim 14 , wherein the mixture has a pH of about 5.5.
16. The method of claim 1 , wherein the microalgae can produce eicosapentaenoic acid (EPA) at temperatures above 32° C.
17. The method of claim 1 , wherein the microalgae is Nannochloropsis.
18. A method for preparing a crude microalgal extract, the method comprising
providing water comprising microalgae,
wherein the water has a pH between about 6.0 and about 10.0 and has a salinity between about 0.01% and about 5%;
providing chitosan in an amount sufficient to form flocs of microalgae when mixed with the water;
generating a mixture of the water and the chitosan, wherein the mixture is acidic; and
separating the flocs from the mixture, thereby preparing a crude microalgal extract.
19. A method for preparing a microalgal lipid extract, the method comprising
providing water comprising microalgae,
wherein the water has a pH between about 6.0 and about 10.0 and has a salinity between about 0.01% and about 5%;
providing chitosan in an amount sufficient to form flocs of microalgae when mixed with the water;
generating a mixture of the water and the chitosan, wherein the mixture is acidic;
separating the flocs from the mixture, thereby harvesting the microalgae; and
extracting lipid from the microalgae, thereby preparing a microalgal lipid extract.
20. The method of claim 1 , wherein the water has a salinity selected from the group consisting of between about 0.5% and about 1.0%, between about 1.0% and about 1.5%, between about 1.5% and about 2.0%, between about 2.0% and about 2.5%, between about 2.5% and about 3.0%, between about 3.0% and about 3.5%, between about 3.5% and about 4.0%, and between about 4.0% and about 4.5%.