• What are the mechanics by which bacteria and microbes could influence the weathering of silicate minerals? Do they tend to help break up larger mineral structures?

  • In nitrogen-containing minerals, can nitrifying bacteria cause weathering?

  • What is the potential increase in reactivity of the weathered rock?

  • Are there biological mechanisms for extracting and/or liberating free or complexed metal ions from the silicate (i.e., serpentine) minerals?

MICROBIAL FIXATION OF CO2 TO FORM CARBONATE MINERALS

Cyanobacteria are known to use their photosynthetic energy to generate small quantities of calcium carbonate (CaCO3). In the Green Lake in Fayetteville, New York, species of synecococcus have been shown to deposit significant amounts of CaCO3 at the bottom of the lake in summer months. As noted, silicate minerals could be utilized as the source of Mg2+ or Ca2+ ions. It is not known whether any microbes are able to utilize Mg2+ to form magnesium carbonate (MgCO3). Selective techniques could be used for developing cyanobacterial strains that will be able to effectively utilize free Mg2+ ions to form MgCO3.

The carbonate formation ability of biological systems is not well understood. Further understanding of this process can help enhance the carbonation reaction once a suitable source of alkalinity is present. Microbial carbonate formation can be coupled to biologically mediated metal ion extraction from silicate minerals to provide one possible pathway for CO2 immobilization. Potential benefits to microbial carbonation reactions include increasing carbonation reaction rates as well as increasing the presence of chemical factors that could help solubilize the carbonate after formation, so that the microbes can keep the surface of the silicate minerals free for further weathering reactions. These reactions could be carried out in industrial-scale bioreactors, large leaching piles, or in situ underground.

Research Areas

Research is needed to understand the biochemistry and regulatory aspects involved in the carbonation reaction in bacteria and microbes and how it might help us increase the rate and/or lower the cost of forming magnesium carbonates.

Following are specific questions that need to be addressed:

  • What is the role of CaCO3 formation in microbes?

  • Can cyanobacteria that can utilize Mg2+ to form MgCO3 be found, isolated, and engineered?

  • What are the characteristics of the genes and enzymes involved in this process, and what are the factors that influence their regulation?

  • What chemical means are utilized to keep carbonate minerals in solution to prevent blocking or inactivating the surface area with carbonates?

  • What is known about side reactions?



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