1. MICROBIAL CALCIFICATION IN SUBSURFACE ENVIRONMENTS
Sookie S. Bang
Department of Chemistry and Chemical Engineering
South Dakota School of Mines and Technology

2. Microbial Calcification
Microorganisms
Soil bacteria (Urease-positive)
Phototrophs
Occurs in
Terrestrial environments: alkaline soil
e.g., plugging of porous media
Aquatic environments: marine and freshwaters
e.g., whitings, calcareous mats

3. Calcification
Ca2+ + HCO3-  CaCO3 + H+

4. Microbial Urease Intracellular Enzyme Urea hydrolysis
NH2-CO-NH2 + H2O —— 2NH3 + CO2
NH3 + H+  NH4+ (pH )
Microorganisms: Eubacteria - Bacillus pasteurii, Proteus vulgaris,
Pseudomonas spp., etc.

5. CaCO3 Precipitation Experiments
Microorganism: Bacillus pasteurii ATCC11859
Medium:
3 g Nutrient broth, 20 g Urea, 2.8 g CaCl2, and 2.12 g NaHCO3, pH 7.8 – 8.0

11. Microbiologically Induced Calcite Precipitation (MICP)
At higher pH : in medium containing Urea, CaCl2 and NaHCO3
Ca2+ + Cell  Cell–Ca2+
Cl- + HCO3- + NH NH4Cl + CO32-
Cell–Ca2+ + CO32-  Cell-CaCO3

12. Calcification in Aquatic Environments
Photosynthetic microorganisms:
Ca2+ + HCO3-  CaCO3 + H+
H+ + HCO3-  CH2O + O2
Ureolytic microorganisms:
NH3 + H+  NH4+

16. Potential Applications of MICP
Microbial plugging in porous media:
(NSF/CMS )
Remediation of cracks and fissures in granite and concrete
Subsurface stabilization in highways with urease enzyme
Dust control for surface soils
Carbon sink in ecosystems

18. Potential Applications of MICP
Microbial plugging in porous media
Remediation of cracks and fissures in granite and concrete:
(NSF/CMS ; CMS )
Subsurface stabilization in highways with urease enzyme
Dust control for surface soils
Carbon sink in ecosystems

21. Potential Applications of MICP
Microbial plugging in porous media
Remediation of cracks and fissures in granite and concrete
Subsurface stabilization in highways with urease enzyme: (NSF/INT )
Dust control for surface soils
Carbon sink in ecosystems

22. Potential Applications of MICP
Microbial plugging in porous media
Remediation of cracks and fissures in granite and concrete
Subsurface stabilization in highways with urease enzyme
Dust control for surface soils
Carbon sink in ecosystems

23. Potential Applications of MICP
Microbial plugging in porous media
Remediation of cracks and fissures in granite and concrete
Subsurface stabilization in highways with urease enzyme
Dust control for surface soils
Carbon sink in ecosystems

24. Proposed Research Experiments at NeSS
Identification of diversity in microorganisms that participate in CaCO3 precipitation:
DNA extraction / PCR amplification / phylogenetic analysis
 MICP in subsurface environments:
Effects of pressure, temperature, and CO2 concentration on CaCO3 precipitation kinetics
Measurement of CO2 sequestration rates:
CO2 flux using the eddy covariance methods

25. Hypotheses/Possibilities
CaCO3 at Homestake has percolated from the surface.
Surface soil microbial populations may have been introduced to the subsurface.
Ecological interactions among microbes in the subsurface result in phyogenetic diversity.
Subsurface environmental factors will influence kinetics of CaCO3 precipitation and CO2 flux.

26. Significance of Proposed Research
Phylogenetic diversity of microbial communities involved in subsurface calcification
Effects of MICP on subsurface hydrology
Application of MICP in subsurface bioremediation
Evaluation of the range of carbon sequestration in deep subsurface