Reducing the risk of well bore leakage of CO2 using engineered biomineralization barriers

Optimization of culture medium to improve bio-cementation effect based on response surface method

The main challenge in the large-scale application of MICP lies in its low efficiency and promoting biofilm growth can effectively address this problem. In the present study, a prediction model was proposed using the response surface method. With the prediction model, optimum concentrations of nutrients in the medium can be obtained. Moreover, the optimized medium was compared with other media via bio-cementation tests. The results show that this prediction model was accurate and effective, and the predicted results were close to the measured results. By using the prediction model, the optimized culture media was determined (20.0 g/l yeast extract, 10.0 g/l polypeptone, 5.0 g/l ammonium sulfate, and 10.0 g/l NaCl). Furthermore, the optimized medium significantly promoted the growth of biofilm compared to other media. In the medium, the effect of polypeptone on biofilm growth was smaller than the effect of yeast extract and increasing the concentration of polypeptone was not beneficial in promoting biofilm growth. In addition, the sand column solidified with the optimized medium had the highest strength and the largest calcium carbonate contents. The prediction model represents a platform technology that leverages culture medium to impart novel sensing, adjustive, and responsive multifunctionality to structural materials in the civil engineering and material engineering fields.

Microfluidic study in a meter-long reactive path reveals how the medium's structural heterogeneity shapes MICP-induced biocementation

Microbially induced calcium carbonate (CaCO₃) precipitation (MICP) is one of the major sustainable alternatives to the artificial cementation of granular media. MICP consists of injecting the soil with bacterial- and calcium-rich solutions sequentially to form calcite bonds among the soil particles that improve the strength and stiffness of soils. The performance of MICP is governed by the underlying microscale processes of bacterial growth, reactive transport of solutes, reaction rates, crystal nucleation and growth. However, the impact of pore-scale heterogeneity on these processes during MICP is not well understood. This paper sheds light on the effect of pore-scale heterogeneity on the spatiotemporal evolution of MICP, overall chemical reaction efficiency and permeability evolution by combining two meter-long microfluidic devices of identical dimensions and porosity with homogeneous and heterogeneous porous networks and real-time monitoring. The two chips received, in triplicate, MICP treatment with an imposed flow and the same initial conditions, while the inlet and outlet pressures were periodically monitored. This paper proposes a comprehensive workflow destined to detect bacteria and crystals from time-lapse microscopy data at multiple positions along a microfluidic replica of porous media treated with MICP. CaCO₃ crystals were formed 1 h after the introduction of the cementation solution (CS), and crystal growth was completed 12 h later. The average crystal growth rate was overall higher in the heterogeneous porous medium, while it became slower after the first 3 h of cementation injection. It was found that the average chemical reaction efficiency presented a peak of 34% at the middle of the chip and remained above 20% before the last 90 mm of the reactive path for the heterogeneous porous network. The homogeneous porous medium presented an overall lower average reaction efficiency, which peaked at 27% 420 mm downstream of the inlet and remained lower than 12% for the rest of the microfluidic channel. These different trends of chemical efficiency in the two networks are due to a higher number of crystals of higher average diameter in the heterogeneous medium than in the homogeneous porous medium. In the interval between 480 and 900 mm, the number of crystals in the heterogeneous porous medium is more than double the number of crystals in the homogeneous porous medium. The average diameters of the crystals were 23-46 μm in the heterogeneous porous medium, compared to 17-40 μm in the homogeneous porous medium across the whole chip. The permeability of the heterogeneous porous medium was more affected than that of the homogeneous system, while the pressure sensors effectively captured a higher decrease in the permeability during the first two hours when crystals were formed and a less prominent decrease during the subsequent seeded growth of the existing crystals, as well as the nucleation and growth of new crystals.

Casein-assisted enhancement of the compressive strength of biocemented sand

As a soil biomineralization process, casein-assisted enzyme-induced carbonate precipitation (EICP) yielded biocemented specimens with significantly higher compressive strength than specimens cemented by regular or skim-milk-assisted EICP treatments. The compound concentration and curing strategy of casein-assisted EICP were experimentally optimized to maximize the compressive strength of precipitates with low calcium carbonate content. Under the optimized EICP conditions (0.893 M urea, 0.581 M CaCl₂, 2.6 g/L urease enzyme, and 38.87 g/L casein), the unconfined compressive strengths reached 2 MPa. The scanning electron micrographs of selected samples provided microscopic evidence that EICP treatments assisted using skim milk and casein impart distinctive strength-enhancement mechanisms. The ammonium ions released from urea hydrolysis created an alkaline environment that makes casein dissociated into the pore water. As the casein-containing pore water became more viscous, the increased contact area with particles facilitated the precipitation of co-bound CaCO₃ minerals and casein in the pore water. Casein was identified as a more efficient assisting agent than skim milk for low-level CaCO₃ precipitation by EICP treatment.

Influence of Culture Medium on Cementation of Coarse Grains Based on Microbially Induced Carbonate Precipitation

A main challenge in the large-scale application of the microbially induced carbonate precipitation (MICP) technique includes the low efficiency of the cementation of coarse grains. Actually, in the MICP treatment process, the cementation effect of the bonding points was more important than pore filling due to the large porosity for coarse grains. To achieve a better cementation effect at bonding points between coarse particles, the quick formation and growth of a biofilm is necessary. In this study, an optimized medium was proposed to improve the cementation effects for coarse materials. The optimized medium and other different media were used for bio-cementation tests with MICP. The viable cell concentrations, strengths, microscopic characteristics, biofilm contents, and calcium carbonate (CaCO3) contents were used to evaluate the bio-cementation and its effects. In bio-cementation tests, the optimized medium led to increased CaCO3 precipitation at the bonding points and better cementation effects compared to other media. Indeed, the strength of the sample treated with the optimized medium was more than 1.2–4 times higher that of the values for other media. The advantages of the optimized medium were demonstrated via bio-cementation tests.

Controlling the Distribution of Microbially Precipitated Calcium Carbonate in Radial Flow Environments

Bacterially driven reactions such as ureolysis can induce calcium carbonate precipitation, a well-studied process called microbially induced calcium carbonate precipitation (MICP). MICP is of interest in subsurface applications such as sealing leaks around wells. For effective field deployment, it is important to study MICP under radial flow conditions, which are relevant to near-well environments. In this study, a laboratory-scale radial flow reactor of 23 cm diameter, with a 1 mm glass bead monolayer serving as a porous medium, was used to investigate the effects of fluid flow rates and calcium concentrations on the mass and distribution of MICP by the ureolytic bacterium Sporosarcina pasteurii. Experiments were performed at hydraulic residence times of 14, 7, and 3.5 min and calcium to urea molar ratios of 0.5:1, 1:1, and 2:1. The total amount of CaCO₃ precipitated in the reactor increased with increasing residence time and with decreasing Ca²⁺ to urea molar ratios. Increased bacterial attachment and increased CaCO₃ precipitation were observed with distance from the center inlet of the reactor in all experiments. More uniform calcium distribution was achieved at lower flow rates. The relationship between reaction and transport rate (i.e., the Damköhler number) is identified as a useful parameter for the prediction of MICP in radial flow environments.

Towards a low CO2 emission building material employing bacterial metabolism (2/2): Prospects for global warming potential reduction in the concrete industry

The production of concrete is one of the most significant contributors to global greenhouse gas emissions. This work focuses on bio-cementation-based products and their potential to reduce global warming potential (GWP). In particular, we address a proposed bio-cementation method employing bacterial metabolism in a two-step process of limestone dissolution and recrystallisation (BioZEment). A scenario-based techno-economic analysis (TEA) is combined with a life cycle assessment (LCA), a market model and a literature review of consumers' willingness to pay, to compute the expected reduction of global GWP. Based on the LCA, the GWP of 1 ton of BioZEment is found to be 70-83% lower than conventional concrete. In the TEA, three scenarios are investigated: brick, precast and onsite production. The results indicate that brick production may be the easiest way to implement the products, but that due to high cost, the impact on global GWP will be marginal. For precast production the expected 10% higher material cost of BioZEment only produces a marginal increase in total cost. Thus, precast production has the potential to reduce global GWP from concrete production by 0-20%. Significant technological hurdles remain before BioZEment-based products can be used in onsite construction scenarios, but in this scenario, the potential GWP reduction ranges from 1 to 26%. While the potential to reduce global GWP is substantial, significant efforts need to be made both in regard to public acceptance and production methods for this potential to be unlocked.

Towards a low CO2 emission building material employing bacterial metabolism (1/2): The bacterial system and prototype production

The production of concrete for construction purposes is a major source of anthropogenic CO₂ emissions. One promising avenue towards a more sustainable construction industry is to make use of naturally occurring mineral-microbe interactions, such as microbial-induced carbonate precipitation (MICP), to produce solid materials. In this paper, we present a new process where calcium carbonate in the form of powdered limestone is transformed to a binder material (termed BioZEment) through microbial dissolution and recrystallization. For the dissolution step, a suitable bacterial strain, closely related to Bacillus pumilus, was isolated from soil near a limestone quarry. We show that this strain produces organic acids from glucose, inducing the dissolution of calcium carbonate in an aqueous slurry of powdered limestone. In the second step, the dissolved limestone solution is used as the calcium source for MICP in sand packed syringe moulds. The amounts of acid produced and calcium carbonate dissolved are shown to depend on the amount of available oxygen as well as the degree of mixing. Precipitation is induced through the pH increase caused by the hydrolysis of urea, mediated by the enzyme urease, which is produced in situ by the bacterium Sporosarcina pasteurii DSM33. The degree of successful consolidation of sand by BioZEment was found to depend on both the amount of urea and the amount of glucose available in the dissolution reaction.

Sporosarcina pasteurii can clog and strengthen a porous medium mimic

The bacterium Sporosarcina pasteurii can produce significant volumes of solid precipitation in the presence of specific chemical environments. These solid precipitate particles can enter a network of microscale pores and cause long-range clogging. As a result, the medium gains strength and exhibits superior mechanical properties. This concept is also known as Microbiologically Induced Calcite Precipitation (MICP). In this study, we have used sponge blocks as surrogate porous media mimics and analyzed several aspects of MICP. A synergistic approach involving electron microscopy (SEM), computerized X-Ray tomography (μCT), quasi-static compressive load testing and chemical characterization (EDX) has been used to understand several physical and chemical aspects of MICP.

Rational Control of Calcium Carbonate Precipitation by Engineered Escherichia coli

Ureolytic bacteria ( e.g., Sporosarcina pasteurii) can produce calcium carbonate (CaCO₃). Tailoring the size and shape of biogenic CaCO₃ may increase the range of useful applications for these crystals. However, wild type Sporosarcina pasteurii is difficult to genetically engineer, limiting control of the organism and its crystal precipitates. Therefore, we designed, constructed, and compared different urease operons and expression levels for CaCO₃ production in engineered Escherichia coli strains. We quantified urease expression and calcium uptake and characterized CaCO₃ crystal phase and morphology for 13 engineered strains. There was a weak relationship between urease expression and crystal size, suggesting that genes surrounding the urease gene cluster affect crystal size. However, when evaluating strains with a wider range of urease expression levels, there was a negative relationship between urease activity and polycrystal size (e.g., larger crystals with lower activity). The resulting range of crystal morphologies created by the rationally designed strains demonstrates the potential for controlling biogenic CaCO₃ precipitation.

Applications of Microbial Processes in Geotechnical Engineering

Over the last 10-15 years, a new field of "biogeotechnics" has emerged as geotechnical engineers seek to find ground improvement technologies which have the potential to be lower carbon, more ecologically friendly, and more cost-effective than existing practices. This review summarizes the developments which have occurred in this new field, outlining in particular the microbial processes which have been shown to be most promising for altering the hydraulic and mechanical responses of soils and rocks. Much of the research effort in this new field has been focused on microbially induced carbonate precipitation (MICP) via ureolysis, while a comprehensive review of MICP is presented here, the developments which have been made regarding other microbial processes, including MICP via denitrification and biogenic gas generation are also presented. Furthermore, this review outlines a new area of study: the potential deployment of fungi in geotechnical applications which has until now been unexplored.

Microbially induced calcium carbonate precipitation driven by ureolysis to enhance oil recovery

Microbially induced calcium carbonate precipitation was used to improve poor volumetric sweep efficiency of water and enhance oil recovery.

Metabolism-Induced CaCO3 Biomineralization During Reactive Transport in a Micromodel: Implications for Porosity Alteration

The ability of Pseudomonas stutzeri strain DCP-Ps1 to drive CaCO3 biomineralization has been investigated in a microfluidic flowcell (i.e., micromodel) that simulates subsurface porous media. Results indicate that CaCO3 precipitation occurs during NO3(-) reduction with a maximum saturation index (SIcalcite) of ∼1.56, but not when NO3(-) was removed, inactive biomass remained, and pH and alkalinity were adjusted to SIcalcite ∼ 1.56. CaCO3 precipitation was promoted by metabolically active cultures of strain DCP-Ps1, which at similar values of SIcalcite, have a more negative surface charge than inactive strain DCP-Ps1. A two-stage NO3(-) reduction (NO3(-) → NO2(-) → N2) pore-scale reactive transport model was used to evaluate denitrification kinetics, which was observed in the micromodel as upper (NO3(-) reduction) and lower (NO2(-) reduction) horizontal zones of biomass growth with CaCO3 precipitation exclusively in the lower zone. Model results are consistent with two biomass growth regions and indicate that precipitation occurred in the lower zone because the largest increase in pH and alkalinity is associated with NO2(-) reduction. CaCO3 precipitates typically occupied the entire vertical depth of pores and impacted porosity, permeability, and flow. This study provides a framework for incorporating microbial activity in biogeochemistry models, which often base biomineralization only on SI (caused by biotic or abiotic reactions) and, thereby, underpredict the extent of this complex process. These results have wide-ranging implications for understanding reactive transport in relevance to groundwater remediation, CO2 sequestration, and enhanced oil recovery.

Evaluation of CO₂ solubility-trapping and mineral-trapping in microbial-mediated CO₂-brine-sandstone interaction

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 mineral-trapping. 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.

Monitoring bacterially induced calcite precipitation in porous media using magnetic resonance imaging and flow measurements

A range of nuclear magnetic resonance (NMR) techniques are employed to provide novel, non-invasive measurements of both the structure and transport properties of porous media following a biologically mediated calcite precipitation reaction. Both a model glass bead pack and a sandstone rock core were considered. Structure was probed using magnetic resonance imaging (MRI) via a combination of quantitative one-dimensional profiles and three-dimensional images, applied before and after the formation of calcite in order to characterise the spatial distribution of the precipitate. It was shown through modification and variations of the calcite precipitation treatment that differences in the calcite fill would occur but all methods were successful in partially blocking the different porous media. Precipitation was seen to occur predominantly at the inlet of the bead pack, whereas precipitation occurred almost uniformly along the sandstone core. Transport properties are quantified using pulse field gradient (PFG) NMR measurements which provide probability distributions of molecular displacement over a set observation time (propagators), supplementing conventional permeability measurements. Propagators quantify the local effect of calcite formation on system hydrodynamics and the extent of stagnant region formation. Collectively, the combination of NMR measurements utilised here provides a toolkit for determining the efficacy of a biological-precipitation reaction for partially blocking porous materials.

Carbonate precipitation under pressure for bioengineering in the anaerobic subsurface via denitrification

A number of bioengineering techniques are being developed using microbially catalyzed hydrolysis of urea to precipitate calcium carbonate for soil and sand strengthening in the subsurface. In this study, we evaluate denitrification as an alternative microbial metabolism to induce carbonate precipitation for bioengineering under anaerobic conditions and at high pressure. In anaerobic batch culture, the halophile Halomonas halodenitrificans is shown to be able to precipitate calcium carbonate at high salinity and at a pressure of 8 MPa, with results comparable to those observed when grown at ambient pressure. A larger scale proof-of-concept experiment shows that, as well as sand, coarse gravel can also be cemented with calcium carbonate using this technique. Possible practical applications in the subsurface are discussed, including sealing of improperly abandoned wells and remediation of hydraulic fracturing during shale gas extraction.

Potential CO2 leakage reduction through biofilm-induced calcium carbonate precipitation

Mitigation strategies for sealing high permeability regions in cap rocks, such as fractures or improperly abandoned wells, are important considerations in the long term security of geologically stored carbon dioxide (CO(2)). Sealing technologies using low-viscosity fluids are advantageous in this context since they potentially reduce the necessary injection pressures and increase the radius of influence around injection wells. Using aqueous solutions and suspensions that can effectively promote microbially induced mineral precipitation is one such technology. Here we describe a strategy to homogenously distribute biofilm-induced calcium carbonate (CaCO(3)) precipitates in a 61 cm long sand-filled column and to seal a hydraulically fractured, 74 cm diameter Boyles Sandstone core. Sporosarcina pasteurii biofilms were established and an injection strategy developed to optimize CaCO(3) precipitation induced via microbial urea hydrolysis. Over the duration of the experiments, permeability decreased between 2 and 4 orders of magnitude in sand column and fractured core experiments, respectively. Additionally, after fracture sealing, the sandstone core withstood three times higher well bore pressure than during the initial fracturing event, which occurred prior to biofilm-induced CaCO(3) mineralization. These studies suggest biofilm-induced CaCO(3) precipitation technologies may potentially seal and strengthen fractures to mitigate CO(2) leakage potential.

Engineered applications of ureolytic biomineralization: a review

Microbially-induced calcium carbonate (CaCO3) precipitation (MICP) is a widely explored and promising technology for use in various engineering applications. In this review, CaCO3 precipitation induced via urea hydrolysis (ureolysis) is examined for improving construction materials, cementing porous media, hydraulic control, and remediating environmental concerns. The control of MICP is explored through the manipulation of three factors: (1) the ureolytic activity (of microorganisms), (2) the reaction and transport rates of substrates, and (3) the saturation conditions of carbonate minerals. Many combinations of these factors have been researched to spatially and temporally control precipitation. This review discusses how optimization of MICP is attempted for different engineering applications in an effort to highlight the key research and development questions necessary to move MICP technologies toward commercial scale applications.