Whitings as a Potential Mechanism for Controlling Atmospheric Carbon Dioxide Concentrations – Final Project Report

Lee, Brady D. ; Apel, William A. ; Walton, Michelle R.

Idaho National Laboratory

关键词: Removal;    Cyanobacteria;    Power Generation;    Microcosms;    Carbon Dioxide;   

DOI  :  10.2172/911640
RP-ID  :  INL/EXT-06-01351
RP-ID  :  DE-AC07-99ID-13727
RP-ID  :  911640

美国|英语

来源: UNT Digital Library

【 摘 要 】

Species of cyanobacteria in the genera Synechococcus and Synechocystis are known to be the catalysts of a phenomenon called "whitings", which is the formation and precipitation of fine-grained CaCO3 particles. Whitings occur when the cyanobacteria fix atmospheric CO2 through the formation of CaCO3 on their cell surfaces which leads to precipitation to the ocean floor and subsequent entombment in mud. Whitings represent one potential mechanism for CO2 sequestration. Research was performed to determine the ability of various strains of Synechocystis and Synechococcus to calcify when grown in microcosms amended with 2.5 mM HCO3- and 3.4 mM Ca2+. Results indicated that while all strains tested have the ability to calcify, only two, Synechococcus species, strains PCC 8806 and PCC 8807, were able to calcify to the extent that CaCO3 was precipitated. Enumeration of the cyanobacterial cultures during testing indicated that cell density did not appear to have an effect on calcification. Factors that had the greatest effect on calcification were CO2 removal and subsequent generation of alkaline pH. As CO2 was removed, growth medium pH increased and soluble Ca2+ was removed from solution. The largest increases in growth medium pH occurred when CO2 levels dropped below 400 ppmv. Precipitation of CaCO3 catalyzed by the growth and physiology of cyanobacteria in the Genus Synechococcus represents a potential mechanism for sequestration of atmospheric CO2 produced during the burning of coal for power generation. Synechococcus sp. strain PCC 8806 and Synechococcus sp. strain PCC 8807 were tested in microcosm experiments for their ability to calcify when exposed to a fixed calcium concentration of 3.4 mM and dissolved inorganic carbon concentrations of 0.5, 1.25 and 2.5 mM. Synechococcus sp. strain PCC 8806 removed calcium continuously over the duration of the experiment producing approximately 18.6 mg of solid-phase calcium. Calcium removal occurred over a two-day time period when Synechococcus sp. strain PCC 8807 was tested and only 8.9 mg of solid phase calcium was produced. The ability of the cyanobacteria to create an alkaline growth environment appeared to be the primary factor responsible for CaCO3 precipitation in these experiments. These research results demonstrate the potential of using cyanobacterial catalyzed “whitings” as a method to sequester CO2 from the atmosphere.