 |
| Titel |
Novel biological approaches to carbon mineralization |
| VerfasserIn |
Ian Power, Paul Kenward, Anna Harrison, Gregory Dipple, Mati Raudsepp, Siobhan Wilson, Gordon Southam |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104707
|
| Publikation (Nr.) |
 EGU/EGU2015-4140.pdf |
|
|
|
|
|
| Zusammenfassung |
| Innovative approaches for accelerating and manipulating fundamental geochemical processes
are necessary to develop carbon mineralization as a viable strategy for the mitigation
of greenhouse gas emissions. Mg-carbonate formation is of interest for both ex
situ and in situ CO2 sequestration strategies1. Accordingly, we have investigated
approaches to accelerate these water-rock reactions that produce Mg-carbonate
minerals using biological approaches. For instance, CO2-limited conditions are
encountered in many systems relevant to CO2 sequestration and represent a severe
limitation on carbon mineralization. In carbonation experiments, the supply of CO2 was
increased with the use of carbonic anhydrase, an enzyme that catalyzes the hydration
of aqueous CO2. The presence of carbonic anhydrase had a dramatic impact on
carbonation rates of brucite [Mg(OH)2]2, a mineral of interest for carbon sequestration3.
In a CO2-rich aqueous environment, cyanobacteria were able to induce hydrated
Mg-carbonate precipitation in microcosm experiments through the alkalinization of their
microenvironment and concentration of cations on their cell membranes, which
also provide regularly spaced, chemically identical sites for mineral nucleation4.
In both lines of investigation, the resulting precipitates were metastable hydrated
Mg-carbonate minerals rather then magnesite [MgCO3], the most stable Mg-carbonate
and therefore the preferred product forsequestering CO2. Consequently, we have
investigated approaches to improve magnesite precipitation rate in these low temperature
environments.
Inopportunely, rates of magnesite precipitation are severely limited at temperatures
below 60 Ë C due to the strong hydration of Mg2+ ions in solution5. Yet, carboxyl
functional groups (R-COOH) are able to cause desolvation of Mg2+ ions6,7. In
microcosm experiments using polystyrene microspheres with a high density of carboxyl
groups, we were able to precipitate magnesite at room temperature from slightly
supersaturated solutions in tens of days. Precipitates were positively identified as magnesite
using transmission electron microscopy and selected area electron diffraction of a
thin section produced by focus ion beam milling. These experiments represent an
acceleration in magnesite formation of several orders of magnitude in comparison to
naturally occurring magnesite at near-surface conditions and without requiring energy
input (e.g., high temperature reactions). Our current focus is to further elucidate
this reaction pathway and upscale precipitation for sequestering anthropogenic
CO2.
[1] Power et al. (2013) Rev. Mineral. Geochem. 77: 305-360. [2] Power et al. (2013) Int.
J. Greenh. Gas Control. 16: 145-155. [3] Harrison et al. (2013) Environ. Sci. Technol.
47: 126-134. [4] Power et al. (2007) Geochem. Trans. 8, 13. [5] Hänchen et al.
(2008) Chem. Eng. Sci. 63: 1012-1028. [6] Roberts et al. (2013) Proc. Natl. Acad.
Sci. U.S.A.. 110: 14540-14545. [7] Kenward et al. (2009) Geobiology 7: 556-565. |
|
|
|
|
|
|