ENHANCED PRACTICAL PHOTOSYNTHETIC CO2 MITIGATION (2002)

This report documents significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation project during the period from 10/2/2001 through 10/01/2002. This report marks the end of year 2 of a three-year project as well as the milestone date for completion of Phase I activities. This report includes our current status and defines the steps being taken to ensure that we meet the project goals by the end of year 3. As indicated in the list of accomplishments below our current efforts are focused on evaluating candidate organisms and growth surfaces, preparing to conduct long-term tests in the bench-scale bioreactor test systems, and scaling-up the test facilities from bench scale to pilot scale. Specific results and accomplishments for the third quarter of 2002 include: Organisms and Growth Surfaces: (1) Test results continue to indicate that thermophilic cyanobacteria have significant advantages as agents for practical photosynthetic CO{sub 2} mitigation before mesophilic forms. (2) Additional thermal features with developed cyanobacterial mats, which might be calcium resistant, were found in YNP. (3) Back to back tests show that there is no detectable difference in the growth of isolate 1.2 s.c. (2) in standard and Ca-modified BG-11 medium. The doubling time for both cases was about 12 hours. (4) The cultivation of cyanobacteria in Ca-BG medium should proceed in the pH range between 7 and 7.4, but this suggestion requires additional experiments. (5) Cyanobacteria can be grown in media where sodium is present at trace levels. (6) Ca{sup 2+} enriched medium can be used as a sink for CO{sub 2} under alkaline conditions. (7) Cyanobacteria are able to generate cones of filaments on travertine surfaces. [Travertine is a mixture of CaCO{sub 3} and CaSO{sub 4}]. We hypothesize that SO{sub 4}{sup 2-} stimulates the generation of such cones, because they are not almost generated on CaCO3 surface. On the other hand, we know that plant gas contains elevated concentrations of SO{sub 4}{sup 2-}. We may speculate that the introduction of 11.2 isolate in CRF might significantly increase the productivity of such facility. It is possible that a higher colonization potential for the screens may allow a higher surface productivity than some of the other isolates. (8) The colonization of Omnisil surface is an auto-inducible and time-requiring process. (9) Omnisil coupons should be treated under pH control, preferably using KOH. Bioreactor support systems and test facilities: (1) The pilot-scale bioreactor construction and debugging is continuing on schedule. Tests of the ''natural'' lighting system have shown acceptable levels of illumination for the bioreactor screens using only collected sunlight. (2) Flow control inserts have been designed for the CRF-2 screens, which require header pipes for flow distribution and control. A staggered drilled-hole design and a thick shim design have both shown acceptable performance results (little to no clogging, uniform flow, ability to load algae on to the screen). They will both be tested in the CRF-2 to see which performs the best over long durations, and the best performing design will be used for the pilot scale bioreactor screens.