CARBON DIOXIDE MITIGATION THROUGH CONTROLLED PHOTOSYNTHESIS
This research was undertaken to meet the need for a robust portfolio of carbon management options to ensure continued use of coal in electrical power generation. In response to this need, the Ohio Coal Research Center at Ohio University developed a novel technique to control the emissions of CO{sub 2} from fossil-fired power plants by growing organisms capable of converting CO{sub 2} to complex sugars through the process of photosynthesis. Once harvested, the organisms could be used in the production of fertilizer, as a biomass fuel, or fermented to produce alcohols. In this work, a mesophilic organism, Nostoc 86-3, was examined with respect to the use of thermophilic algae to recycle CO{sub 2} from scrubbed stack gases. The organisms were grown on stationary surfaces to facilitate algal stability and promote light distribution. The testing done throughout the year examined properties of CO{sub 2} concentration, temperature, light intensity, and light duration on process viability and the growth of the Nostoc. The results indicate that the Nostoc species is suitable only in a temperature range below 125 F, which may be practical given flue gas cooling. Further, results indicate that high lighting levels are not suitable for this organism, as bleaching occurs and growth rates are inhibited. Similarly, the organisms do not respond well to extended lighting durations, requiring a significant (greater than eight hour) dark cycle on a consistent basis. Other results indicate a relative insensitivity to CO{sub 2} levels between 7-12% and CO levels as high as 800 ppm. Other significant results alluded to previously, relate to the development of the overall process. Two processes developed during the year offer tremendous potential to enhance process viability. First, integration of solar collection and distribution technology from Oak Ridge laboratories could provide a significant space savings and enhanced use of solar energy. Second, the use of translating slug flow technology to cool the gas stream and enhance bicarbonate concentrations could both enhance organism growth rates and make the process one that could be applied at any fossil-fired power generation unit. These results were augmented by measurements of CO{sub 2} loss from the bioreactor test section. The corresponding mass balance was resolved to within 2%, which is remarkable for the low level of CO{sub 2} actually absorbed by the cyanobacteria. The net result was approximately 10.2 g of CO{sub 2} absorbed of the original 2.97 m{sup 3} of circulating flue gas, (or about 19% of the original CO{sub 2}). While this result in no way predicts the ability of the system to remove CO{sub 2} over the long term in a full-scale operating system, it appears to give credence to the workability of the system.
- Research Organization:
- National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- FG26-99FT40592
- OSTI ID:
- 795267
- Report Number(s):
- FG26-99FT40592-01; TRN: US200212%%28
- Resource Relation:
- Other Information: PBD: 1 Oct 2000
- Country of Publication:
- United States
- Language:
- English
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