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