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Biological determinants of photobioreactor design. Quarterly report No. 7, April 1, 1995--June 30, 1995

Description: The photosynthetic conversion of light energy into algal biomass in large-scale cultures is controlled by the availability of light, the photosynthetic machinery of algae, nutrients, temperature and the design characteristics of the culture system. For the situation in which light is made the growth rate limiting factor, there is an upper limit in the light conversion efficiency of a large-scale culture, which translates to a maximum potential yield of 30-40 g dry weight m-2 day-1 under ideal light conditions. The development of large-scale mass cultures involves many considerations, but the two major design parameters for optimizing yields at a particular time are the flow rate throughout the culture and the depth of the culture.
Date: April 1, 1997
Creator: Palsson, B.O. & Brown, G.G.
Partner: UNT Libraries Government Documents Department

Biological determinants of photobioreactor design. 6. quarterly report, February 1--July 31, 1995

Description: Interest has developed in using algae to fix CO{sub 2} to produce oxygen and biomass for life-support in space, and for reducing CO{sub 2} emissions from power plants. A novel photobioreactor (PBR) system using light-emitting diodes (LEDs) as a sole light source was constructed and operated with continuous medium perfusion. Direct internal illumination by 680 nm LEDs could deliver as high as 50 mW/cm{sup 2} of light into the culture medium. Gas transfer by internal sparging had the capacity to transfer 250 mmol O{sub 2}/L culture/h. Nutritional limitations could be overcome by continuous perfusion, supplying the medium components to the culture without increasing osmolarity, while removing potentially inhibitory cellular wastes. When the PBR operated in a continuous perfusion mode with a perfusion rate of 6 reactor volumes a day (6 VVD), it could support ultra high-density algal cultures up to cell concentrations of 4 {times} 10{sup 9} cells/mL and total cell volume fractions of 9.4% v/v (about 25 g dry weight/L). The oxygen production rate at its peak was 13 to 15 mmol/L culture/h. This performance represents the highest reported cell densities attained in photoautotrophic cultures. Continuous perfusion allowed for long-term stable oxygen production, while oxygen production in batch mode ceased when stationary phase was reached. The results presented suggest that PBR technology can still be significantly improved.
Date: July 7, 1995
Creator: Palsson, B.O. & Brown, G.G.
Partner: UNT Libraries Government Documents Department

Biological determinants of photobioreactor design. Final report, September 1, 1993--August 31, 1995

Description: Microalgae is being considered for the capture and sequestration of CO{sub 2} from power-plant flue-gases. High productivity of microalgae is necessary to make this process cost effective compared to the conventional methods used for reducing CO{sub 2} levels in the atmosphere. This obviates the need for large-scale cultivation technologies and proper photobioreactor technology. The physical factors that influence the performance of a photoautotrophic microalgal culture are the quality and composition of light, inlet carbon dioxide concentration, nutrients, and secondary metabolites at high cell densities. In developing photobioreactor technology, balancing of biological processes to the physical rate process becomes important. The effect of various light compositions on the culture kinetics was studied. To determine the optimal composition, six wavelengths 470, 555, 560, 570, 580 and 605 nm, each supplemented with 680 nm of red light, were used to cultivate cultures. Based on the results obtained, it is concluded that a monochromatic red light of 680 nm is sufficient to obtain maximum capacity.
Date: April 1, 1997
Creator: Palsson, B. & Brown, G.G.
Partner: UNT Libraries Government Documents Department