MICROBIAL CALCIFICATION IN
SUBSURFACE ENVIRONMENTS
Sookie S. Bang
Department of Chemistry and Chemical Engineering
South Dakota School of Mines and Technology
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
Calcification
Ca2+ + HCO3- CaCO3 + H+
Microbial Urease
• Intracellular Enzyme
• Urea hydrolysisUREASE
NH2-CO-NH2 + H2O —— 2NH3 + CO2
NH3 + H+ NH4+ (pH )
• Microorganisms: Eubacteria - Bacillus pasteurii, Proteus vulgaris,
Pseudomonas spp., etc.
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
Time (hr)
0 10 20 30 40 50 60
Cel
ls m
l-1
106
107
108
NH
4+ (
mM
)
200
300
400
500
600
700
800
900
Inso
lubl
e C
a2+
(m
M)
2
3
4
5
6789
20
30
10
pH
8
9
10
Microbiologically InducedCalcite Precipitation (MICP)
At higher pH : in medium containing Urea, CaCl2 and NaHCO3
Ca2+ + Cell Cell–Ca2+
Cl- + HCO3- + NH3 NH4Cl + CO3
2-
Cell–Ca2+ + CO32- Cell-CaCO3
Calcification in Aquatic Environments
• Photosynthetic microorganisms:
Ca2+ + HCO3- CaCO3 + H+
H+ + HCO3- CH2O + O2
• Ureolytic microorganisms:
Ca2+ + HCO3- CaCO3 + H+
NH3 + H+ NH4+
Potential Applications of MICP
• Microbial plugging in porous media:(NSF/CMS-9412942)
• Remediation of cracks and fissures in Remediation of cracks and fissures in granite and concretegranite and concrete
• Subsurface stabilization in highways Subsurface stabilization in highways with urease enzymewith urease enzyme
• Dust control for surface soils Dust control for surface soils • Carbon sink in ecosystemsCarbon sink in ecosystems
Potential Applications of MICP
• Microbial plugging in porous mediaMicrobial plugging in porous media• Remediation of cracks and fissures in
granite and concrete:(NSF/CMS-9412942; CMS-9802127 )
• Subsurface stabilization in highways Subsurface stabilization in highways with urease enzymewith urease enzyme
• Dust control for surface soils Dust control for surface soils • Carbon sink in ecosystemsCarbon sink in ecosystems
Potential Applications of MICP
• Microbial plugging in porous mediaMicrobial plugging in porous media
• Remediation of cracks and fissures in Remediation of cracks and fissures in granite and concretegranite and concrete
• Subsurface stabilization in highways with urease enzyme: (NSF/INT-0002608)
• Dust control for surface soils Dust control for surface soils
• Carbon sink in ecosystemsCarbon sink in ecosystems
Potential Applications of MICP
• Microbial plugging in porous mediaMicrobial plugging in porous media
• Remediation of cracks and fissures in Remediation of cracks and fissures in granite and concretegranite and concrete
• Subsurface stabilization in highways Subsurface stabilization in highways with urease enzymewith urease enzyme
• Dust control for surface soils
• Carbon sink in ecosystemsCarbon sink in ecosystems
Potential Applications of MICP
• Microbial plugging in porous mediaMicrobial plugging in porous media
• Remediation of cracks and fissures in Remediation of cracks and fissures in granite and concretegranite and concrete
• Subsurface stabilization in highways Subsurface stabilization in highways with urease enzymewith urease enzyme
• Dust control for surface soilsDust control for surface soils
• Carbon sink in ecosystems
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
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.
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