Marine Pollution Bulletin 85 (2014) 78–85
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Evaluation of CO2 solubility-trapping and mineral-trapping in microbial-mediated CO2–brine–sandstone interaction Jing Zhao a, Wei Lu a, Fengjun Zhang a, Cong Lu a,⇑, Juanjuan Du a, Rongyue Zhu b, Lei Sun c a
Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China College of Construction Engineering, Jilin University, Changchun 130021, China c Liaoning Institute of Mineral Exploration, Shenyang 110032, China b
a r t i c l e
i n f o
Article history: Available online 9 July 2014 Keywords: Carbon capture and geological storage (CCS) Indigenous microbe Chlorite Transition-state calcite Siderite
a b s t r a c t Evaluation of CO2 solubility-trapping and mineral-trapping by microbial-mediated process was investigated by lab experiments in this study. The results verified that microbes could adapt and keep relatively high activity under extreme subsurface environment (pH < 5, temperature > 50 °C, salinity > 1.0 mol/L). When microbes mediated in the CO2–brine–sandstone interaction, the CO2 solubility-trapping was enhanced. The more biomass of microbe added, the more amount of CO2 dissolved and trapped into the water. Consequently, the corrosion of feldspars and clay minerals such as chlorite was improved in relative short-term CO2–brine–sandstone interaction, providing a favorable condition for CO2 mineraltrapping. Through SEM images and EDS analyses, secondary minerals such as transition-state calcite and crystal siderite were observed, further indicating that the microbes played a positive role in CO2 mineral trapping. As such, bioaugmentation of indigenous microbes would be a promising technology to enhance the CO2 capture and storage in such deep saline aquifer like Erdos, China. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction The fourth IPCC report stated with ever-more certainty that anthropogenic emission of CO2 have been made primarily responsible for global warming (Ebigbo et al., 2010; IPCC, 2007). Thus, the reduction of potential CO2 in the atmosphere becomes obligatory to mitigate global warming (Frerichs et al., 2013). Recently, carbon capture and geological storage (CCS) is widely considered as a promising technology to reduce CO2 emission to the atmosphere (Benson and Cole, 2008; Metz et al., 2005a,b; Portier and Rochelle, 2005). Potential geological reservoirs for CCS are depleted gas and oil reservoir, un-mineable coal seam formations and deep saline aquifers (Benson and Cole, 2008; Krüger et al., 2011). Particularly, deep saline aquifers are preferred and well-documented due to its large storage capacity, ubiquity, and potential for carbonate mineral trapping (Bachu and Adams, 2003; Goldberg et al., 2010, 2008; McGrail et al., 2006; Bergman, 1995). However, it may take a thousand years or longer to undergo mineral trapping in the deep saline aquifers (Metzker, 2005). In the view of storage security, it is significant to reduce the time scale of mineral trapping (Cunningham et al., 2011; Naganuma et al., 2011). Microorganisms would be of interest, ⇑ Corresponding author. Tel./fax: +86 431 88499792. E-mail address: [email protected] (C. Lu). http://dx.doi.org/10.1016/j.marpolbul.2014.06.019 0025-326X/Ó 2014 Elsevier Ltd. All rights reserved.
because they are predominant in earth biosphere, especially in deep saline aquifers. Many important processes in geological systems are partly catalyzed by microorganisms (Whitman et al., 1998). Therefore, it’s essential to investigate the potential role of microorganisms in the CO2 sequestration. Mitchell et al. (2009) proposed that biofilms could enhance geologic sequestration of supercritical CO2 and reduce leakage of CO2 by its plugging channels among rocks. Subsequent researches also demonstrated the potential effect of biofilms on the CO2 solubility and CO2 mineral trapping (Mitchell et al., 2010; Cunningham et al., 2009; Morozova et al., 2011). Recently, the microbial community was investigated in the CO2 injection or leakage environment. The microbial community variation of anaerobic and acidophilic microorganisms was found in CO2 leakage soil environment (Oppermann et al., 2010). Then H2-oxidising bacteria (Hydrogenophaga sp., Acidovorax sp., Ralstonia sp., Pseudomonas sp.), thiosulfate-oxidizing bacteria (Diaphorobacter sp.) and biocorrosive thermophilic microorganisms were detected in depleted gas reservoir (Morozova et al., 2011) and the Chromohalobacter marismortui, Halobacillus trueperi etc. were identified in deep saline aquifers with CO2 injection (Kirk et al., 2012; Krüger et al., 2011; Naganuma et al., 2011; Wang et al., 2012). These findings proved the potential growth of microorganisms in the extreme environment with long-term exposure of high CO2 concentration, and their potential effect on the CO2 solubility and mineral trapping. However, there were still
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few researches to evaluate the contribution of the specific indigenous microorganism to the CO2 solubility and mineral trapping in the CO2-brine- rock interaction. To address some of the above-mentioned issues, experimental study focusing on the evaluation of CO2 solubility-trapping and mineral-trapping by microbial mediated process was investigated in this study. The objectives of this study are (1) to verify the potential growth of microorganisms under the extreme environment such as CO2 injection environment (pH < 5, temperature > 50 °C and salinity > 1.0 mol/L); (2) to evaluate the role of specific indigenous microorganisms in the CO2 solubility-trapping and mineral-trapping in the CO2–brine–sandstone interaction. 2. Materials and methods 2.1. Experimental set-up The experimental set-up in this study was shown in Fig. 1. Supercritical CO2 with 99.5% purity was injected into stainless steel reactors (with a volume of 1 L) via a booster pump and the samples were collected by a sample basket. The experimental condition was controlled by thermometer and pressure gauge. 2.2. Experimental materials CO2 gas: CO2 gases were provided by Jv-yang Gases Company in China. Invert the gases cylinders and take out supercritical of CO2 by a liquid boost pump in the experiment. 2.2.1. Water sample The water sample was collected from Shihezi reservoir (about 1600 m depths), a CO2 injection site in Erdos, China. One part of the water sample was for microbe isolation, the other part was for chemical analysis. Then the fluid used in the stainless steel reactor experiments was artificially prepared: CaCl2 2.9556 g, MgCl26H2O 0.0374 g, KNO3 0.1976 g, NaHCO3 0.7163 g, FeSO47H2O 0.2362 g, NaCl 5.6674 g, in 1 L deionized water.
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rock samples were partly processed into 10 mm 10 mm 1 mm slice, and partly processed into uniform crushed stones for the microbial-mediated CO2–brine–sandstone interaction experiments.
3. Experimental 3.1. Potential growth of microorganisms under the extreme environments Three experimental sets (temperature, pH and salinity) were conducted in flasks to investigate the potential growth of indigenous microorganisms under the extreme environments. Certain quantity of microorganism in the logarithmic growth phase was inoculated into each flask with CO2 filled headspace and cultured in thermostatic incubator for 68 h. Then the biomass was measured by spread-plate method.
3.2. CO2 solubility-trapping and mineral-trapping in microbial mediated CO2–brine–sandstone interaction The experiments with different microbial biomass of 0, 2.3 106, 7.0 106 and 11.7 107 CFU/mL (experimental set No. was denoted as B0, B1, B2 and B3, respectively) were conducted in stainless steel reactors to evaluate the contribution of microbes to the CO2 solubility-trapping. Microbes were inoculated into the sterilized artificially water with solid–liquid ratio of 1:20 (g/mL). The rock sample includes a slice and a few crushed stones. The system continuously run at 50 °C, 10 MPa and 16 r/min for 60 days. The water and sandstone samples were collected periodically in a stainless steel reactor and depressurized to atmospheric pressure at a rate of 0.01 MPa/min (Kaszuba et al., 2005). To prevent precipitation, the fluid samples for cation analysis were directly filtered with 0.22 lm filter membrane and acidified to pH 2 (Kaszuba et al., 2005).
3.3. Analysis 2.2.2. Microbial samples Three isolated anoxic strains (Klebsiella, Clostridium and Plesiomonas sp.) used in this study were enriched and isolated from the water sample collected from field site in a relative anoxic environment at 50 °C, atmospheric pressure in the lab. 2.2.3. Rock samples The core samples were collected at about 1600 m below surface (m.b.s), Shihezi reservoir. Quantitative X-ray diffraction and X-rayfluorescence results demonstrated that the rock sample was sandstone consisting of 66% quartz, 15% illite, 7% smectite layer-mixed minerals, 6% plagioclase, 3% dolomite and 3% calcite. Besides, the
The pH of fluid sample was measured by pH meter. Dissolved Ca2+, Mg2+, Na+, K+, Al3+ in fluid samples were determined by Atomic Absorption Spectrometry (AAS, Shimadzu, AA-6300CF), and dissolved Fe, Si were determined by Inductively Coupled Plasma using Mass Spectroscopy (ICP-MS 7500A, Agilent, Santa Clara, CA, USA) (Carey et al., 2007). Anions were analyzed by chemical titration. The corrosion and precipitation of minerals were analyzed by Scanning Electron Microscopy (SEM, JEOL, Tokyo, Japan) and Energy Dispersive Spectrometry (EDS, Oxford, UK) (Carey et al., 2007). Microbe biomass was measured by spread-plate method (Metz et al., 2005a,b).
Fig. 1. Experimental setup.
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4. Results and discussions 4.1. Potential growth of microbes under extreme environment The pH of deep aquifer water could reach 4–5 when suddenly exposed to large amount of supercritical carbon dioxide (scCO2), consequently affecting the metabolic activity of microorganisms in the deep saline aquifers (Cunningham et al., 1997; Kirk et al., 2012). Afterwards, the pH in CO2 injected deep aquifer gradually increased up to 6–7 during long-term CO2–brine–sandstone interaction. In this study, the best pH for the growth of microorganisms was 5, verifying that the three isolated microbes can grow well under the acid environment. Moreover, they could grow well at a wide range of pH (Fig. 2a), demonstrating their great adaptability to the pH variation in CO2–brine–sandstone interaction. Besides, high temperature could affect enzymes activity and consequently affect the growth of microorganisms (Cunningham et al., 2009). The results in this study showed that microbes can grow well at 20–60 °C (Fig. 2b), except for 70 °C (enzymes destroyed), further supporting that microorganisms could adapt and keep relative high activity at relative high temperature (50– 60 °C) of a deep aquifer with CO2 injection. High salinity (>1.00 mol/L) was a typical characteristic of a deep aquifer which may change cell permeability and thus affect the growth of microorganisms. The microbes investigated in this study were expected to grow well in high salinity (Fig. 2c). Results showed that salinity had little effect on the growth of them in the experimental scale (0.00–1.50 mol/L). Multiple regression of OD600, pH, temperature and salinity confirmed that salinity had less effect on the growth of microorganisms than that of pH and temperature (Table S1 in Supplementary Material-SM). In general, findings in this study proved that microbes could adapt and keep relatively high activity under extreme environment like a deep saline aquifer with CO2 injection. 4.2. Microbial mediated CO2–brine–sandstone system
4.2.1. CO2 solubility-trapping Normally, the injected CO2 was at supercritical state, inducing a condition of two phases. One immiscibly displaced the in situ aqueous phase may be called as ‘‘gas’’ (Pruess and García, 2002). The other had the limited solubility in aqueous phase, contributing to the CO2 solubility-trapping in CO2–brine–sandstone interaction (Bachu et al., 2007; Wigand et al., 2008). After CO2 dissolution into the water, carbonic acid was rapidly produced and then dissociated into hydrogen ion and bicarbonates, causing a significant decrease
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of pH. Subsequently, a complex series of reactions (fluid–rock interaction) occurred (Eqs. 1–6 in SM) (Harvey et al., 2013). In this study, the results showed that the bicarbonate of water in the CO2–brine–sandstone interaction with different biomass (Fig. 3b–d) was much higher than that of without biomass (Fig. 3a), and correspondingly lower pH was observed. It can be concluded that the microbes added to the CO2–brine–sandstone interaction system promoted the CO2 solubility trapping at a certain pressure. Moreover, the more biomass of microbe, the more amount of CO2 dissolved and trapped in water (Fig. 3). As such, the highest biomass of microbe (11.7 107 CFU/mL) was taken for the following experiments. 4.2.2. The corrosion of feldspars The feldspar is one of the typical mineral of sandstone in saline aquifer of CO2 injection site, in Erdos, China. So in this study the feldspar (chemical components include Na+, K+ and Al3+) was selected as one of the represented minerals to investigate the influence of microbes on the CO2 solubility and mineral trapping. When injected CO2 dissolved in water, carbonic acid formed and proton enriched in the aqueous phase, resulting in the corrosion of host rocks (Harvey et al., 2013) (Eqs. 1, 7–9 in SM). In this study, the results showed that the concentrations of Na+, K+ and Al3+in the water generally increased during the reaction. Compared with the reaction without microbe, the concentrations of Na+, K+ and Al3+ were generally higher (Fig 4a–c). Therefore, it suggested that the corrosion of feldspar enhanced, resulting from the microbe mediated in the CO2–brine–sandstone interaction. Besides, some elements (e.g. Na+, K+ and Al3+) released from the feldspar corrosion process may react with other minerals and consequently new minerals were produced. The pH in the CO2–brine–sandstone interaction in this study was decreased to a range of 5.5–7.0, where the feldspar corrosion was dominated by proton adsorption and exchange reaction (Blake and Walter, 1996). So, the more feldspar corrosion was observed in the lower pH of microbial-mediated CO2–brine–sandstone interaction (Fig. 4e). Conversely, the more feldspar corrosion accelerated, the more CO2 dissolved into brine to produce protons. Moreover, the SEM images (Fig. 4d and e) and corresponding EDS analyses (Fig. S1a and b) provided conclusive evidence of corrosion of feldspar rich in Al, Si and K after 60 days of reaction. Therefore, the findings in this study proved that microbes enhanced the corrosion of host rocks such as feldspars in the process of CO2–brine–sandstone interaction, and subsequently facilitating CO2 mineral-trapping. 4.2.3. The corrosion of chlorite After CO2 injection, the pH decreased significantly, which may result in the corrosion of clay minerals such as chlorite (Wigand et al., 2008). Thus, Mg2+ was selected as one typical element of chlorite to investigate the potential corrosion of chlorite in the CO2–brine–sandstone interaction mediated by microbial. The results showed that Mg2+ in the water significantly increased during the reaction (Fig. 5a), indicating that chlorite was probably eroded during CO2–brine–sandstone interaction. Particularly, it can be found that the concentration of Mg2+ in CO2–brine–sandstone interaction with microbes was significantly higher than that in CO2–brine–sandstone interaction, indicating that microbes could promote the corrosion of chlorite. Then the SEM images (Fig. 5b, c) and corresponding EDS analyses (Fig. S2a and b) further proved the corrosion of chlorite rich in Mg, Si, Fe and Al after 60 days of reaction. Additionally, it can be seen that the Mg2+ in the water was increased signally at the first 30 days and then slightly increased at last 30 days (Fig. 5a). This could be explained that the corrosion of clay minerals may firstly be carried out during the
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Fig. 3. CO2 solubility-trapping in microbial mediated CO2–brine–sandstone interaction with biomass (a) 0, (b) 2.3 106, (c) 7.0 106, (d) 11.7 107 CFU/mL.
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Time/ d Fig. 4. The erosion of feldspars in CO2–brine–sandstone interaction by microbial-mediated process. Concentration variation of (a) Na+, (b) K+ and (c) Al3+ in the CO2–brine– sandstone interaction without/with microbial-mediated process; SEM images of feldspars after 60 days of reaction (d) without and (e) with microbial-mediated process.
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Fig. 5. The erosion of chlorite in CO2–brine–sandstone interaction by microbial-mediated process. Concentration variation of (a) Mg2+ in the CO2–brine–sandstone interaction without/with microbial-mediated process; SEM images of chlorite after 60 days of reaction (b) without or with (c) microbial-mediated process.
CO2–brine–sandstone interaction and then followed the corrosion of feldspar (Wigand et al., 2008). At the beginning of reaction, high concentration of H+ contributed to the corrosion of the chlorite. Then the corrosion of feldspar was occurred to compete the H+ with that of chlorite, which led to the less increasing of corrosion of chlorite at the last step of CO2 -brine-sandstone interaction (Fig 5a). Roberts et al. (2013) reported that Mg2+ was a complex and dewatered by surface-bound carboxyl groups, thus decreasing the required energy for carbonation. And microbial biomass could control carboxyl group density on carbon surface to promote the precipitation of carbonate mineral, due to its high density of carboxyl groups, sharp biogeochemical interfaces and high salinity. However, there was no magnesite observed in this study, in spite of a lot of Mg2+ dissolved and microbes participated in CO2-brine-rock reaction system. That was probably attributed to the much higher solubility product constant Ksp of magnesite (6.82 10 6) than that of calcite (3.36 10 9) and siderite (3.13 10 11), acting as a tough reactive barrier that microbial biomass could hardly overcome. Therefore, some carbonate minerals such as magnesite could not readily precipitate due to the reaction kinetics restriction, especially at relatively low temperature (Arvidson and Mackenzie, 1999; Saldi et al., 2009).
4.2.4. Secondary mineral–calcite formation Calcite was one of the typical carbonate minerals precipitated in the CO2–brine–sandstone interaction. So, Ca2+ was selected as one represented element of calcite to evaluate the CO2 mineral-trapping in microbial mediated CO2–brine–sandstone interaction process. The results showed that rapid dissolution of Ca2+ obtained (Fig. 6a and b) at the beginning of the CO2–brine–sandstone interaction (5 days), probably resulting from corrosion of minerals such as calcite, feldspar or clay minerals (Harvey et al., 2013; Matter et al., 2007; Rosenbauer et al., 2005) (Eqs. 10 and 11 in SM). And then the dissolution rate of Ca2+ was signally decreased with the increasing of pH, which was consistent with the findings of (Dupraz et al., 2009).
During 5–10 days of CO2–brine–sandstone interaction, the concentration of Ca2+ was sharply decreased, indicating that secondary mineral (e.g. calcite) may be formed after dissolution of Ca2+ from corrosion of minerals such as calcite, feldspar or clay minerals. However, no calcite but spherical mineral only rich in C was observed by SEM image (Fig. 6c) and corresponding EDS data (Fig. S3a). Additionally, the lower concentration of Ca2+ was detected in the CO2–brine–sandstone interaction by microbial mediated process (Fig. 6a), further suggesting that microbes may promote the calcite precipitation. When calcite precipitation occurred, the microbes in the CO2–brine–sandstone system had a rapid growth and consequently biofilms communities formed, contributing to the active precipitation of calcium carbonate minerals from the Ca2+ and HCO3 in the water (Cunningham et al., 2009). However, no crystal calcite but transition-state calcite rich in C and Ca was formed and observed through the SEM images (Fig. 6d) and EDS analyses (Fig. S3b), due to the relatively low temperature (50 °C) and short-term reaction (60 days) in this study. Overall, it can be concluded that the microbes could enhance the formation of secondary mineral-calcite, as a result, facilitating CO2 mineral-trapping.
4.2.5. Secondary mineral–siderite formation Siderite was another kind of carbonate minerals which might be precipitated in the CO2–brine–sandstone interaction. Therefore, total Fe (TFe) was measured to evaluate the siderite precipitation in CO2–brine–sandstone interaction without and with microbial mediated process. The results showed that the concentration of TFe significantly increased at first 10 days of the CO2–brine–sandstone interaction (Fig. 7a), suggesting that the dissolution of Fe2+ was carried out by the corrosion of minerals. And then the concentration of TFe decreased greatly and kept relatively stable at the end of CO2–brine–sandstone interaction. This suggested that the dissolution of Fe2+ performed, meanwhile, the precipitation of secondary minerals contained Fe (e.g. siderite) occurred, resulting in the decreasing
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Time/ d Fig. 6. The formation of secondary mineral-calcite in CO2–brine–sandstone interaction by microbial-mediated process. Concentration variation of (a) Ca2+ and (b) H+ in the CO2–brine–sandstone interaction without/with microbial-mediated process; SEM images of calcite after 60 days of reaction (c) without or (d) with microbial-mediated process.
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Fig. 7. The formation of secondary mineral-siderite in CO2–brine–sandstone interaction by microbial-mediated process. Concentration variation of (a) TFe in the CO2–brine– sandstone interaction without/with microbial-mediated process; SEM images of siderite after reaction (b) without or (c) with microbial-mediated process.
amount of TFe in water. In addition, the SEM images (Fig. 7b) and EDS analyses (Fig. S4a) verified that new granular mineral contained Fe and C was precipitated on the sandstone surface. Kaszuba et al., (2003) reported that microbes could decline the kinetic barriers and lower the forming temperature of siderite, as a
result, accelerating the precipitation of siderite. In this study, the lower concentration of TFe was observed in the microbial-mediated CO2–brine–sandstone interaction (Fig. 7a), demonstrating that microbes may promote the formation of siderite. Then SEM images (Fig. 7c) and EDS analysis (Fig. S4b) further proved the
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formation of crystallized siderite on the sandstone surface. Therefore, it can be concluded that the microbes investigated in this study had a great potential to promote the formation of secondary mineral such as siderite, consequently enhancing the CO2 mineral trapping. 5. Conclusions From our experiments, we can conclude that indigenous microbes isolated from a deep saline aquifer could adapt and keep relatively high activity under extreme environment. When microbes mediated in the CO2–brine–sandstone interaction, the CO2 solubility-trapping was enhanced to some extent. Correspondingly, the corrosion of feldspars and clay minerals such as chlorite was accelerated, providing a favorable condition for CO2 mineraltrapping. Secondary minerals such as transition-state calcite and crystal siderite except for magnesite were observed to form after relative short-term (60 days) of CO2–brine–sandstone interaction by microbial-mediated process. This could be explained that the microbes’ activity decreased the kinetic barriers and lowered the forming temperature of carbonates (e.g. calcite and siderite), consequently shortening the time of CO2 mineral trapping and improving the amount of the CO2 mineral trapping. Therefore, microbes presented a great potential for enhancing the CO2 solubility trapping and mineral trapping. Also, microbes could limit the transport of CO2 fluids in the reservoir, consequently reducing the risk of CO2 leakage from the cap rock through plugging pore channels by biofilms. In addition, it was recommended that bioaugmentation of indigenous microbes would be a promising technology to enhance the CO2 storage and trapping in such deep saline aquifer like Erdos, China. However, there are still many challenges, such as the growth (biomass, metabolic activity) and transport of microbes, the efficient contact of microbes with nutrient, CO2 fluid and host rock in such low permeable subsurface like CO2 deep saline aquifer, etc. Acknowledgements The present work was funded by China Geological Survey working Project (Grant No. 12120113006300), National Natural Science Foundation of China (Grant No. 41302182) and National Key Technology R&D Program - China (Grant No. 2012BAJ25B10). Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.marpolbul.2014. 06.019. References Mitchell, Andrew C., Lee, K., Spangler, H., Cunningham, Alfred B., Gerlach, Robin, 2010. Microbially enhanced carbon capture and storage by mineral-trapping and solubility-trapping. Environ. Sci. Technol. 44, 5270–5276. Arvidson, R.S., Mackenzie, F.T., 1999. The dolomite problem; control of precipitation kinetics by temperature and saturation state. Am. J. Sci. 299, 257–288. Bachu, S., Adams, J.J., 2003. Sequestration of CO2 in geological media in response to climate change: capacity of deep saline aquifers to sequester CO2 in solution. Energy Convers. Manage. 44, 3151–3175. Bachu, S., Bonijoly, D., Bradshaw, J., Burruss, R., Holloway, S., Christensen, N.P., Mathiassen, O.M., 2007. CO2 storage capacity estimation: methodology and gaps. Int. J. Greenhouse Gas Control 1, 430–443. Benson, S.M., Cole, D.R., 2008. CO2 sequestration in deep sedimentary formations. Elements 4, 325–331. Blake, R.E., Walter, L.M., 1996. Effects of organic acids on the dissolution of orthoclase at 80°C and pH 6. Chem. Geol. 132, 91–102.
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Metz, B., Davidson, O., Coninck, H.D., Loos, M., Meyer, L., 2005b. Carbon Dioxide Capture and Storage-Special Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge. Metzker, M.L., 2005. Emerging technologies in DNA sequencing. Genome Res. 15, 1767–1776. Mitchell, A.C., Phillips, A.J., Hiebert, R., Gerlach, R., Spangler, L.H., Cunningham, A.B., 2009. Biofilm enhanced geologic sequestration of supercritical CO2. Int. J. Greenhouse Gas Control 3, 90–99. Morozova, D., Alawi, M., Shaheed, M., Krüger, M., Kock, D., Würdemann, H., 2011. The influence of microbial activity on rock fluid interaction: Baseline characterization of deep biosphere for Enhanced Gas Recovery in the Altmark natural gas reservoir. Energy Procedia 4, 4633–4640. Naganuma, T., Yukimura, K., Todaka, N., Ajima, S., 2011. Concept and experimental study for a new enhanced mineral trapping system by means of microbially mediated processes. Energy Procedia 4, 5079–5084. Oppermann, B.I., Michaelis, W., Blumenberg, M., Frerichs, J., Schulz, H.M., Schippers, A., Beaubien, S.E., Krüger, M., 2010. Soil microbial community changes as a result of long-term exposure to a natural CO2 vent. Geochim. Cosmochim. Acta 74, 2697–2716. Bergman, Perry D., Winter, E.M., 1995. Disposal of carbon dioxide in aquifers in the US. Energy Convers. Manage., 523–526. Portier, S., Rochelle, C., 2005. Modelling CO2 solubility in pure water and NaCl-type waters from 0 to 300 °C and from 1 to 300 bar. Chem. Geol. 217, 187–199. Pruess, K., García, J., 2002. Multiphase flow dynamics during CO2 disposal into saline aquifers. Environ. Geol. 42, 282–295. Roberts, J.A., Kenward, P.A., Fowle, D.A., Goldstein, R.H., Gonzalez, L.A., Moore, D.S., 2013. Surface chemistry allows for abiotic precipitation of dolomite at low temperature. Proc. Natl. Acad. Sci. USA 110, 14540–14545.
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Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul
Evaluation of CO2 solubility-trapping and mineral-trapping in microbial-mediated CO2–brine–sandstone interaction Jing Zhao a, Wei Lu a, Fengjun Zhang a, Cong Lu a,⇑, Juanjuan Du a, Rongyue Zhu b, Lei Sun c a
Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China College of Construction Engineering, Jilin University, Changchun 130021, China c Liaoning Institute of Mineral Exploration, Shenyang 110032, China b
a r t i c l e
i n f o
Article history: Available online 9 July 2014 Keywords: Carbon capture and geological storage (CCS) Indigenous microbe Chlorite Transition-state calcite Siderite
a b s t r a c t Evaluation of CO2 solubility-trapping and mineral-trapping by microbial-mediated process was investigated by lab experiments in this study. The results verified that microbes could adapt and keep relatively high activity under extreme subsurface environment (pH < 5, temperature > 50 °C, salinity > 1.0 mol/L). When microbes mediated in the CO2–brine–sandstone interaction, the CO2 solubility-trapping was enhanced. The more biomass of microbe added, the more amount of CO2 dissolved and trapped into the water. Consequently, the corrosion of feldspars and clay minerals such as chlorite was improved in relative short-term CO2–brine–sandstone interaction, providing a favorable condition for CO2 mineraltrapping. Through SEM images and EDS analyses, secondary minerals such as transition-state calcite and crystal siderite were observed, further indicating that the microbes played a positive role in CO2 mineral trapping. As such, bioaugmentation of indigenous microbes would be a promising technology to enhance the CO2 capture and storage in such deep saline aquifer like Erdos, China. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction The fourth IPCC report stated with ever-more certainty that anthropogenic emission of CO2 have been made primarily responsible for global warming (Ebigbo et al., 2010; IPCC, 2007). Thus, the reduction of potential CO2 in the atmosphere becomes obligatory to mitigate global warming (Frerichs et al., 2013). Recently, carbon capture and geological storage (CCS) is widely considered as a promising technology to reduce CO2 emission to the atmosphere (Benson and Cole, 2008; Metz et al., 2005a,b; Portier and Rochelle, 2005). Potential geological reservoirs for CCS are depleted gas and oil reservoir, un-mineable coal seam formations and deep saline aquifers (Benson and Cole, 2008; Krüger et al., 2011). Particularly, deep saline aquifers are preferred and well-documented due to its large storage capacity, ubiquity, and potential for carbonate mineral trapping (Bachu and Adams, 2003; Goldberg et al., 2010, 2008; McGrail et al., 2006; Bergman, 1995). However, it may take a thousand years or longer to undergo mineral trapping in the deep saline aquifers (Metzker, 2005). In the view of storage security, it is significant to reduce the time scale of mineral trapping (Cunningham et al., 2011; Naganuma et al., 2011). Microorganisms would be of interest, ⇑ Corresponding author. Tel./fax: +86 431 88499792. E-mail address: [email protected] (C. Lu). http://dx.doi.org/10.1016/j.marpolbul.2014.06.019 0025-326X/Ó 2014 Elsevier Ltd. All rights reserved.
because they are predominant in earth biosphere, especially in deep saline aquifers. Many important processes in geological systems are partly catalyzed by microorganisms (Whitman et al., 1998). Therefore, it’s essential to investigate the potential role of microorganisms in the CO2 sequestration. Mitchell et al. (2009) proposed that biofilms could enhance geologic sequestration of supercritical CO2 and reduce leakage of CO2 by its plugging channels among rocks. Subsequent researches also demonstrated the potential effect of biofilms on the CO2 solubility and CO2 mineral trapping (Mitchell et al., 2010; Cunningham et al., 2009; Morozova et al., 2011). Recently, the microbial community was investigated in the CO2 injection or leakage environment. The microbial community variation of anaerobic and acidophilic microorganisms was found in CO2 leakage soil environment (Oppermann et al., 2010). Then H2-oxidising bacteria (Hydrogenophaga sp., Acidovorax sp., Ralstonia sp., Pseudomonas sp.), thiosulfate-oxidizing bacteria (Diaphorobacter sp.) and biocorrosive thermophilic microorganisms were detected in depleted gas reservoir (Morozova et al., 2011) and the Chromohalobacter marismortui, Halobacillus trueperi etc. were identified in deep saline aquifers with CO2 injection (Kirk et al., 2012; Krüger et al., 2011; Naganuma et al., 2011; Wang et al., 2012). These findings proved the potential growth of microorganisms in the extreme environment with long-term exposure of high CO2 concentration, and their potential effect on the CO2 solubility and mineral trapping. However, there were still
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few researches to evaluate the contribution of the specific indigenous microorganism to the CO2 solubility and mineral trapping in the CO2-brine- rock interaction. To address some of the above-mentioned issues, experimental study focusing on the evaluation of CO2 solubility-trapping and mineral-trapping by microbial mediated process was investigated in this study. The objectives of this study are (1) to verify the potential growth of microorganisms under the extreme environment such as CO2 injection environment (pH < 5, temperature > 50 °C and salinity > 1.0 mol/L); (2) to evaluate the role of specific indigenous microorganisms in the CO2 solubility-trapping and mineral-trapping in the CO2–brine–sandstone interaction. 2. Materials and methods 2.1. Experimental set-up The experimental set-up in this study was shown in Fig. 1. Supercritical CO2 with 99.5% purity was injected into stainless steel reactors (with a volume of 1 L) via a booster pump and the samples were collected by a sample basket. The experimental condition was controlled by thermometer and pressure gauge. 2.2. Experimental materials CO2 gas: CO2 gases were provided by Jv-yang Gases Company in China. Invert the gases cylinders and take out supercritical of CO2 by a liquid boost pump in the experiment. 2.2.1. Water sample The water sample was collected from Shihezi reservoir (about 1600 m depths), a CO2 injection site in Erdos, China. One part of the water sample was for microbe isolation, the other part was for chemical analysis. Then the fluid used in the stainless steel reactor experiments was artificially prepared: CaCl2 2.9556 g, MgCl26H2O 0.0374 g, KNO3 0.1976 g, NaHCO3 0.7163 g, FeSO47H2O 0.2362 g, NaCl 5.6674 g, in 1 L deionized water.
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rock samples were partly processed into 10 mm 10 mm 1 mm slice, and partly processed into uniform crushed stones for the microbial-mediated CO2–brine–sandstone interaction experiments.
3. Experimental 3.1. Potential growth of microorganisms under the extreme environments Three experimental sets (temperature, pH and salinity) were conducted in flasks to investigate the potential growth of indigenous microorganisms under the extreme environments. Certain quantity of microorganism in the logarithmic growth phase was inoculated into each flask with CO2 filled headspace and cultured in thermostatic incubator for 68 h. Then the biomass was measured by spread-plate method.
3.2. CO2 solubility-trapping and mineral-trapping in microbial mediated CO2–brine–sandstone interaction The experiments with different microbial biomass of 0, 2.3 106, 7.0 106 and 11.7 107 CFU/mL (experimental set No. was denoted as B0, B1, B2 and B3, respectively) were conducted in stainless steel reactors to evaluate the contribution of microbes to the CO2 solubility-trapping. Microbes were inoculated into the sterilized artificially water with solid–liquid ratio of 1:20 (g/mL). The rock sample includes a slice and a few crushed stones. The system continuously run at 50 °C, 10 MPa and 16 r/min for 60 days. The water and sandstone samples were collected periodically in a stainless steel reactor and depressurized to atmospheric pressure at a rate of 0.01 MPa/min (Kaszuba et al., 2005). To prevent precipitation, the fluid samples for cation analysis were directly filtered with 0.22 lm filter membrane and acidified to pH 2 (Kaszuba et al., 2005).
3.3. Analysis 2.2.2. Microbial samples Three isolated anoxic strains (Klebsiella, Clostridium and Plesiomonas sp.) used in this study were enriched and isolated from the water sample collected from field site in a relative anoxic environment at 50 °C, atmospheric pressure in the lab. 2.2.3. Rock samples The core samples were collected at about 1600 m below surface (m.b.s), Shihezi reservoir. Quantitative X-ray diffraction and X-rayfluorescence results demonstrated that the rock sample was sandstone consisting of 66% quartz, 15% illite, 7% smectite layer-mixed minerals, 6% plagioclase, 3% dolomite and 3% calcite. Besides, the
The pH of fluid sample was measured by pH meter. Dissolved Ca2+, Mg2+, Na+, K+, Al3+ in fluid samples were determined by Atomic Absorption Spectrometry (AAS, Shimadzu, AA-6300CF), and dissolved Fe, Si were determined by Inductively Coupled Plasma using Mass Spectroscopy (ICP-MS 7500A, Agilent, Santa Clara, CA, USA) (Carey et al., 2007). Anions were analyzed by chemical titration. The corrosion and precipitation of minerals were analyzed by Scanning Electron Microscopy (SEM, JEOL, Tokyo, Japan) and Energy Dispersive Spectrometry (EDS, Oxford, UK) (Carey et al., 2007). Microbe biomass was measured by spread-plate method (Metz et al., 2005a,b).
Fig. 1. Experimental setup.
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4. Results and discussions 4.1. Potential growth of microbes under extreme environment The pH of deep aquifer water could reach 4–5 when suddenly exposed to large amount of supercritical carbon dioxide (scCO2), consequently affecting the metabolic activity of microorganisms in the deep saline aquifers (Cunningham et al., 1997; Kirk et al., 2012). Afterwards, the pH in CO2 injected deep aquifer gradually increased up to 6–7 during long-term CO2–brine–sandstone interaction. In this study, the best pH for the growth of microorganisms was 5, verifying that the three isolated microbes can grow well under the acid environment. Moreover, they could grow well at a wide range of pH (Fig. 2a), demonstrating their great adaptability to the pH variation in CO2–brine–sandstone interaction. Besides, high temperature could affect enzymes activity and consequently affect the growth of microorganisms (Cunningham et al., 2009). The results in this study showed that microbes can grow well at 20–60 °C (Fig. 2b), except for 70 °C (enzymes destroyed), further supporting that microorganisms could adapt and keep relative high activity at relative high temperature (50– 60 °C) of a deep aquifer with CO2 injection. High salinity (>1.00 mol/L) was a typical characteristic of a deep aquifer which may change cell permeability and thus affect the growth of microorganisms. The microbes investigated in this study were expected to grow well in high salinity (Fig. 2c). Results showed that salinity had little effect on the growth of them in the experimental scale (0.00–1.50 mol/L). Multiple regression of OD600, pH, temperature and salinity confirmed that salinity had less effect on the growth of microorganisms than that of pH and temperature (Table S1 in Supplementary Material-SM). In general, findings in this study proved that microbes could adapt and keep relatively high activity under extreme environment like a deep saline aquifer with CO2 injection. 4.2. Microbial mediated CO2–brine–sandstone system
4.2.1. CO2 solubility-trapping Normally, the injected CO2 was at supercritical state, inducing a condition of two phases. One immiscibly displaced the in situ aqueous phase may be called as ‘‘gas’’ (Pruess and García, 2002). The other had the limited solubility in aqueous phase, contributing to the CO2 solubility-trapping in CO2–brine–sandstone interaction (Bachu et al., 2007; Wigand et al., 2008). After CO2 dissolution into the water, carbonic acid was rapidly produced and then dissociated into hydrogen ion and bicarbonates, causing a significant decrease
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of pH. Subsequently, a complex series of reactions (fluid–rock interaction) occurred (Eqs. 1–6 in SM) (Harvey et al., 2013). In this study, the results showed that the bicarbonate of water in the CO2–brine–sandstone interaction with different biomass (Fig. 3b–d) was much higher than that of without biomass (Fig. 3a), and correspondingly lower pH was observed. It can be concluded that the microbes added to the CO2–brine–sandstone interaction system promoted the CO2 solubility trapping at a certain pressure. Moreover, the more biomass of microbe, the more amount of CO2 dissolved and trapped in water (Fig. 3). As such, the highest biomass of microbe (11.7 107 CFU/mL) was taken for the following experiments. 4.2.2. The corrosion of feldspars The feldspar is one of the typical mineral of sandstone in saline aquifer of CO2 injection site, in Erdos, China. So in this study the feldspar (chemical components include Na+, K+ and Al3+) was selected as one of the represented minerals to investigate the influence of microbes on the CO2 solubility and mineral trapping. When injected CO2 dissolved in water, carbonic acid formed and proton enriched in the aqueous phase, resulting in the corrosion of host rocks (Harvey et al., 2013) (Eqs. 1, 7–9 in SM). In this study, the results showed that the concentrations of Na+, K+ and Al3+in the water generally increased during the reaction. Compared with the reaction without microbe, the concentrations of Na+, K+ and Al3+ were generally higher (Fig 4a–c). Therefore, it suggested that the corrosion of feldspar enhanced, resulting from the microbe mediated in the CO2–brine–sandstone interaction. Besides, some elements (e.g. Na+, K+ and Al3+) released from the feldspar corrosion process may react with other minerals and consequently new minerals were produced. The pH in the CO2–brine–sandstone interaction in this study was decreased to a range of 5.5–7.0, where the feldspar corrosion was dominated by proton adsorption and exchange reaction (Blake and Walter, 1996). So, the more feldspar corrosion was observed in the lower pH of microbial-mediated CO2–brine–sandstone interaction (Fig. 4e). Conversely, the more feldspar corrosion accelerated, the more CO2 dissolved into brine to produce protons. Moreover, the SEM images (Fig. 4d and e) and corresponding EDS analyses (Fig. S1a and b) provided conclusive evidence of corrosion of feldspar rich in Al, Si and K after 60 days of reaction. Therefore, the findings in this study proved that microbes enhanced the corrosion of host rocks such as feldspars in the process of CO2–brine–sandstone interaction, and subsequently facilitating CO2 mineral-trapping. 4.2.3. The corrosion of chlorite After CO2 injection, the pH decreased significantly, which may result in the corrosion of clay minerals such as chlorite (Wigand et al., 2008). Thus, Mg2+ was selected as one typical element of chlorite to investigate the potential corrosion of chlorite in the CO2–brine–sandstone interaction mediated by microbial. The results showed that Mg2+ in the water significantly increased during the reaction (Fig. 5a), indicating that chlorite was probably eroded during CO2–brine–sandstone interaction. Particularly, it can be found that the concentration of Mg2+ in CO2–brine–sandstone interaction with microbes was significantly higher than that in CO2–brine–sandstone interaction, indicating that microbes could promote the corrosion of chlorite. Then the SEM images (Fig. 5b, c) and corresponding EDS analyses (Fig. S2a and b) further proved the corrosion of chlorite rich in Mg, Si, Fe and Al after 60 days of reaction. Additionally, it can be seen that the Mg2+ in the water was increased signally at the first 30 days and then slightly increased at last 30 days (Fig. 5a). This could be explained that the corrosion of clay minerals may firstly be carried out during the
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Fig. 3. CO2 solubility-trapping in microbial mediated CO2–brine–sandstone interaction with biomass (a) 0, (b) 2.3 106, (c) 7.0 106, (d) 11.7 107 CFU/mL.
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Fig. 5. The erosion of chlorite in CO2–brine–sandstone interaction by microbial-mediated process. Concentration variation of (a) Mg2+ in the CO2–brine–sandstone interaction without/with microbial-mediated process; SEM images of chlorite after 60 days of reaction (b) without or with (c) microbial-mediated process.
CO2–brine–sandstone interaction and then followed the corrosion of feldspar (Wigand et al., 2008). At the beginning of reaction, high concentration of H+ contributed to the corrosion of the chlorite. Then the corrosion of feldspar was occurred to compete the H+ with that of chlorite, which led to the less increasing of corrosion of chlorite at the last step of CO2 -brine-sandstone interaction (Fig 5a). Roberts et al. (2013) reported that Mg2+ was a complex and dewatered by surface-bound carboxyl groups, thus decreasing the required energy for carbonation. And microbial biomass could control carboxyl group density on carbon surface to promote the precipitation of carbonate mineral, due to its high density of carboxyl groups, sharp biogeochemical interfaces and high salinity. However, there was no magnesite observed in this study, in spite of a lot of Mg2+ dissolved and microbes participated in CO2-brine-rock reaction system. That was probably attributed to the much higher solubility product constant Ksp of magnesite (6.82 10 6) than that of calcite (3.36 10 9) and siderite (3.13 10 11), acting as a tough reactive barrier that microbial biomass could hardly overcome. Therefore, some carbonate minerals such as magnesite could not readily precipitate due to the reaction kinetics restriction, especially at relatively low temperature (Arvidson and Mackenzie, 1999; Saldi et al., 2009).
4.2.4. Secondary mineral–calcite formation Calcite was one of the typical carbonate minerals precipitated in the CO2–brine–sandstone interaction. So, Ca2+ was selected as one represented element of calcite to evaluate the CO2 mineral-trapping in microbial mediated CO2–brine–sandstone interaction process. The results showed that rapid dissolution of Ca2+ obtained (Fig. 6a and b) at the beginning of the CO2–brine–sandstone interaction (5 days), probably resulting from corrosion of minerals such as calcite, feldspar or clay minerals (Harvey et al., 2013; Matter et al., 2007; Rosenbauer et al., 2005) (Eqs. 10 and 11 in SM). And then the dissolution rate of Ca2+ was signally decreased with the increasing of pH, which was consistent with the findings of (Dupraz et al., 2009).
During 5–10 days of CO2–brine–sandstone interaction, the concentration of Ca2+ was sharply decreased, indicating that secondary mineral (e.g. calcite) may be formed after dissolution of Ca2+ from corrosion of minerals such as calcite, feldspar or clay minerals. However, no calcite but spherical mineral only rich in C was observed by SEM image (Fig. 6c) and corresponding EDS data (Fig. S3a). Additionally, the lower concentration of Ca2+ was detected in the CO2–brine–sandstone interaction by microbial mediated process (Fig. 6a), further suggesting that microbes may promote the calcite precipitation. When calcite precipitation occurred, the microbes in the CO2–brine–sandstone system had a rapid growth and consequently biofilms communities formed, contributing to the active precipitation of calcium carbonate minerals from the Ca2+ and HCO3 in the water (Cunningham et al., 2009). However, no crystal calcite but transition-state calcite rich in C and Ca was formed and observed through the SEM images (Fig. 6d) and EDS analyses (Fig. S3b), due to the relatively low temperature (50 °C) and short-term reaction (60 days) in this study. Overall, it can be concluded that the microbes could enhance the formation of secondary mineral-calcite, as a result, facilitating CO2 mineral-trapping.
4.2.5. Secondary mineral–siderite formation Siderite was another kind of carbonate minerals which might be precipitated in the CO2–brine–sandstone interaction. Therefore, total Fe (TFe) was measured to evaluate the siderite precipitation in CO2–brine–sandstone interaction without and with microbial mediated process. The results showed that the concentration of TFe significantly increased at first 10 days of the CO2–brine–sandstone interaction (Fig. 7a), suggesting that the dissolution of Fe2+ was carried out by the corrosion of minerals. And then the concentration of TFe decreased greatly and kept relatively stable at the end of CO2–brine–sandstone interaction. This suggested that the dissolution of Fe2+ performed, meanwhile, the precipitation of secondary minerals contained Fe (e.g. siderite) occurred, resulting in the decreasing
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amount of TFe in water. In addition, the SEM images (Fig. 7b) and EDS analyses (Fig. S4a) verified that new granular mineral contained Fe and C was precipitated on the sandstone surface. Kaszuba et al., (2003) reported that microbes could decline the kinetic barriers and lower the forming temperature of siderite, as a
result, accelerating the precipitation of siderite. In this study, the lower concentration of TFe was observed in the microbial-mediated CO2–brine–sandstone interaction (Fig. 7a), demonstrating that microbes may promote the formation of siderite. Then SEM images (Fig. 7c) and EDS analysis (Fig. S4b) further proved the
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formation of crystallized siderite on the sandstone surface. Therefore, it can be concluded that the microbes investigated in this study had a great potential to promote the formation of secondary mineral such as siderite, consequently enhancing the CO2 mineral trapping. 5. Conclusions From our experiments, we can conclude that indigenous microbes isolated from a deep saline aquifer could adapt and keep relatively high activity under extreme environment. When microbes mediated in the CO2–brine–sandstone interaction, the CO2 solubility-trapping was enhanced to some extent. Correspondingly, the corrosion of feldspars and clay minerals such as chlorite was accelerated, providing a favorable condition for CO2 mineraltrapping. Secondary minerals such as transition-state calcite and crystal siderite except for magnesite were observed to form after relative short-term (60 days) of CO2–brine–sandstone interaction by microbial-mediated process. This could be explained that the microbes’ activity decreased the kinetic barriers and lowered the forming temperature of carbonates (e.g. calcite and siderite), consequently shortening the time of CO2 mineral trapping and improving the amount of the CO2 mineral trapping. Therefore, microbes presented a great potential for enhancing the CO2 solubility trapping and mineral trapping. Also, microbes could limit the transport of CO2 fluids in the reservoir, consequently reducing the risk of CO2 leakage from the cap rock through plugging pore channels by biofilms. In addition, it was recommended that bioaugmentation of indigenous microbes would be a promising technology to enhance the CO2 storage and trapping in such deep saline aquifer like Erdos, China. However, there are still many challenges, such as the growth (biomass, metabolic activity) and transport of microbes, the efficient contact of microbes with nutrient, CO2 fluid and host rock in such low permeable subsurface like CO2 deep saline aquifer, etc. Acknowledgements The present work was funded by China Geological Survey working Project (Grant No. 12120113006300), National Natural Science Foundation of China (Grant No. 41302182) and National Key Technology R&D Program - China (Grant No. 2012BAJ25B10). Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.marpolbul.2014. 06.019. References Mitchell, Andrew C., Lee, K., Spangler, H., Cunningham, Alfred B., Gerlach, Robin, 2010. Microbially enhanced carbon capture and storage by mineral-trapping and solubility-trapping. Environ. Sci. Technol. 44, 5270–5276. Arvidson, R.S., Mackenzie, F.T., 1999. The dolomite problem; control of precipitation kinetics by temperature and saturation state. Am. J. Sci. 299, 257–288. Bachu, S., Adams, J.J., 2003. Sequestration of CO2 in geological media in response to climate change: capacity of deep saline aquifers to sequester CO2 in solution. Energy Convers. Manage. 44, 3151–3175. Bachu, S., Bonijoly, D., Bradshaw, J., Burruss, R., Holloway, S., Christensen, N.P., Mathiassen, O.M., 2007. CO2 storage capacity estimation: methodology and gaps. Int. J. Greenhouse Gas Control 1, 430–443. Benson, S.M., Cole, D.R., 2008. CO2 sequestration in deep sedimentary formations. Elements 4, 325–331. Blake, R.E., Walter, L.M., 1996. Effects of organic acids on the dissolution of orthoclase at 80°C and pH 6. Chem. Geol. 132, 91–102.
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