ENHANCED PRACTICAL PHOTOSYNTHETIC CO2 MITIGATION (2002)

This quarterly report documents significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation project during the period from 4/2/2001 through 7/01/2002. Most of the achievements are milestones in our efforts to complete the tasks and subtasks that constitute the project objectives, and we are currently on schedule to complete Phase I activities by 10/2002, the milestone date from the original project timeline. As indicated in the list of accomplishments below, our efforts are focused on improving the design of the bioreactor test system, evaluating candidate organisms and growth surfaces, and scaling-up the test facilities from bench scale to pilot scale. Specific results and accomplishments for the second quarter of 2002 include: Organisms and Growth Surfaces: (1) Our collection of cyanobacteria, isolated in YNP was increased to 15 unialgal cultures. (2) Illumination rate about 50 {micro}E/m{sup 2}/sec is not saturated for the growth of 1.2 s.c. (2) isolate. The decrease of illumination rate led to the decrease of doubling time of this isolate. (3) The positive effect of Ca{sup 2+} on the growth of isolate 1.2 s.c. (2) without Omnisil was revealed, though Ca{sup 2+} addition was indifferent for the growth of this isolate at the presence of Omnisil. (4) Calcium addition had a positive effect on the generation of cyanobacterial biofilm on Omnisil surface. (5) The survivability problems with the Tr9.4 organism on Omnisil screens in the CRF2 model-scale bioreactor have been solved. The problems were related to the method used to populate the growth surfaces. When pre-populated screens were placed in the bioreactor the microalgae died within 72 hours, but when the microalgae were cultured while in place in the bioreactor using a continuous-population method they grew well inside of the CRF2 test system and survived for the full 7-day test duration. CRF2 tests will continue as soon as the new combined drip system/harvesting system header pipe design is refined. Bioreactor support systems and test facilities: (1) A solar collector, fiber optic light cables, and 8 light distribution panels have been installed at the pilot-scale bioreactor site. The ''natural'' lighting system is ready for the pilot-scale bioreactor system-level debugging tests scheduled for early to mid July. (2) CO{sub 2} scrubbing tests were carried out to understand the CO{sub 2} scrubbing capability of translating slug flow under various conditions. Within experimental error, for liquid velocities of 0.6 m/s and 1m/s it was shown that different gas velocities (including 4.8, 6.6 and 9m/s) cause no significant change in CO{sub 2} concentration. (3) The harvesting tests were put on hold while an alternative loading method was developed and to concentrate our resources on the design of the new combined drip system/harvesting system header pipe. A new header pipe design has been completed and proof-of-concept tests have shown good performance in the drip loading mode. Tests have also shown that we can create preferable conditions for harvesting with this design, and actual harvesting tests will be run as soon as screens are available that have achieved a sufficiently ''thick'' growth state such that harvesting is desired.