Systems and methods for delivery of gases to algal cultures
Photobioreactors according to embodiments of the present invention deliver nutrient gas intermittently to the photobioreactor media. In some embodiments, one or more gases are delivered according to a duty cycle or timing pattern. According to some embodiments, algae is grown in a photobioreactor using intermittent introduction of carbon dioxide. In other embodiments, carbon dioxide is supplied to algae grown in a photobioreactor in whole or in part from a head space above the media of the photobioreactor.
1. A method for regulating carbon dioxide introduction in a closed photobioreactor having a media, a culture of microorganisms in the media, and a head space adjacent to the media, the method comprising:
determining a carbon dioxide deficiency in the media by determining pH of the media using a pH sensing device; and
based on the pH of the media, delivering carbon dioxide into the photobioreactor according to a duty cycle, wherein the duty cycle consists of ON times and OFF times, wherein during the ON times a supply of carbon dioxide is delivered to the photobioreactor and at least a portion of gas already in the head space is exhausted, and wherein during the OFF times the supply of carbon dioxide is not delivered to the photobioreactor and carbon dioxide residing in the head space diffuses into the media, wherein the duty cycle is set to achieve a desired pH range, and wherein the desired pH range facilitates growth of the culture of microorganisms.
2. The method of claim 1 , further comprising storing the gas from the head space after it has been exhausted from the photobioreactor.
3. The method of claim 2 , further comprising reusing the stored gas from the head space by reintroducing the stored gas into the head space.
4. The method of claim 3 , further comprising separating carbon dioxide from the stored gas, and wherein reintroducing the stored gas into the head space comprises reintroducing the separated carbon dioxide into the head space.
5. The method of claim 1 , wherein delivering carbon dioxide into the photobioreactor comprises introducing the carbon dioxide directly into the head space.
6. The method of claim 5 , further comprising agitating the media with a mechanism other than sparging.
7. The method of claim 1 , wherein the carbon dioxide is a nutrient for the culture.
8. The method of claim 7 , wherein the culture of microorganisms comprises algae.
9. The method of claim 7 , wherein delivering carbon dioxide into the photobioreactor comprises introducing one or more gases by sparging the one or more gases into the culture of microorganisms.
10. The method of claim 9 , wherein the one or more gases comprise one or more of carbon dioxide, air, and inert gas.
11. The method of claim 1 , wherein determining the carbon dioxide deficiency is performed with a feedback system, and wherein the delivering of the carbon dioxide into the photobioreactor is performed with a controller system based on feedback from the feedback system.
12. The method of claim 1 , wherein carbon dioxide flow rate is set based upon the desired pH range.
13. The method of claim 1 , wherein flow rate and duration of carbon dioxide flow into the closed photobioreactor is based on an algorithm.
14. The method of claim 1 , wherein the desired pH range is determined by a desired growth stage of the culture of microorganisms.