Ground improvement and its role in carbon dioxide reduction: a review

Experimental study on characterization of lime-based mineral carbonation reaction and CO2 sequestration

This paper reports for the first time the use and application of a novel technique in the characterization of mineral carbonation reaction and CO2 sequestration in soil stabilization using flow meters. Soils based on SiO2 with two different sizes were tested. Lime (Ca(OH)2) was used as the reactant. Instant CO2 flow rate (L/min), total CO2 volume (L), temperature (°C), and absolute pressure (kPa) were monitored and recorded for 1 h by flow meters connected to the mold inlet and outlet. It was determined that the mineral carbonation reaction started in the first seconds and ended before the 5th minute. The mineral carbonation is a short-term and potential reaction, and it is not a time-dependent reaction. It is separated from other carbonation reactions with these characteristics. The highest CO2 captured value was obtained in the soil mixed with 5% lime, where fines were not used. The second highest CO2 captured value was obtained in soil mixed with 1% lime, where fines were not used. CO2 captured with 1% lime is more than CO2 captured with 5% lime in the soil containing fines. Accordingly, 1-5% lime can be used in soil carbonation studies. According to the soil properties, the highest CO2 captured and the CO2 efficiency was achieved with the use of 6-7% water by weight.

Exploring the roles of green finance and environmental regulations on CO2es: defining the roles of social and economic globalization in the next eleven nations

Achieving sustainable environmental growth and preventing further environmental degradation are challenging goals for policymakers. This study looks at environmental laws and green finance's role in fostering a more sustainable environment. The literature still needs to empirically or theoretically investigate how environmental laws and green financing affect carbon dioxide (CO2) emissions, particularly when combined with moderating factors such as social and economic globalization. As a result, this study investigates how environmental laws and green funding can help the N-11 nations cut their CO2 emissions. Our research uses empirical data from a group of the N-11 nations that span the years 2000 to 2019. To handle issues with panel data analysis, such as cross-sectional dependence and slope heterogeneity, we use advanced panel approaches (CIPS and CADF unit root and cointegration test and cross-sectional augmented ARDL). This research demonstrates that green financing (GFI) and environmental laws (ENV) have a negative but significant effect on CO2 emissions. While social globalization moderates the causal relationship between energy consumption and GDP while negatively and significantly causing GFI and ENV with CO2 emissions among the N-11 countries, economic growth has had a positive and significant effect on CO2 emissions in the N-11 countries. According to our research, nations could achieve the SDG-7 and SDG-13 goals if they adopted green financial and environmental policies.

Utilization of bottom ash waste as a granular column to enhance the lateral load capacity of soft kaolin clay soil

Implementation of industrial wastes such as bottom ash in ground improvement can be cost-effective and environment-friendly. Ground improvement is an effective method of mitigation to improve problematic soils including soft kaolin clay soils as the problematic soils always expose to the severe settlements, low shear strength, immoderate plasticity, greater compressibility, dispersivity, bulging, erodibility, and susceptibility to climatic variables. Several studies conducted on the granular column using the bottom ash column. However, only a few studies have reported findings coherent with the statistical analysis. In this study, the lateral load capacity of bottom ash column-kaolin clay has been conducted. Coherently, the reinforced kaolin clay samples were tested via particle size distribution, Atterberg limit test, relative density, compaction test, permeability test, unconfined compression test, and unconsolidated undrained triaxial test with the single and group of encapsulated bottom ash columns with the geotextile encasement and a prediction model was developed. The effect of a number of columns, column diameter, column height, area replacement ratio, height penetration ratio, height-diameter column ratio, volume replacement ratio, and confining pressures on the shear strength of the single and group of encapsulated bottom ash columns have been investigated. The findings showed the effectiveness of using the bottom ash columns at various number of column, column diameter, column height, area replacement ratio, height penetration ratio, height-diameter column ratio, volume replacement ratio, and confining pressures can enhance the shear strength of the soil up to 77.00% at the optimal utilization of single encapsulated bottom ash column of 10-mm diameter and 80-mm height. Therefore, the study proved that the utilization of bottom ash waste as a granular column can significantly enhance the lateral load capacity of soft kaolin clay soil.

Mineralogy, morphology, and reaction kinetics of ureolytic bio-cementation in the presence of seawater ions and varying soil materials

Microbially-induced calcium carbonate precipitation (MICP) is a bio-cementation process that can improve the engineering properties of granular soils through the precipitation of calcium carbonate (CaCO₃) minerals on soil particle surfaces and contacts. The technology has advanced rapidly as an environmentally conscious soil improvement method, however, our understanding of the effect of changes in field-representative environmental conditions on the physical and chemical properties of resulting precipitates has remained limited. An improved understanding of the effect of subsurface geochemical and soil conditions on process reaction kinetics and the morphology and mineralogy of bio-cementation may be critical towards enabling successful field-scale deployment of the technology and improving our understanding of the long-term chemical permanence of bio-cemented soils in different environments. In this study, thirty-five batch experiments were performed to specifically investigate the influence of seawater ions and varying soil materials on the mineralogy, morphology, and reaction kinetics of ureolytic bio-cementation. During experiments, differences in reaction kinetics were quantified to identify conditions inhibiting CaCO₃ precipitation and ureolysis. Following experiments, scanning electron microscopy, x-ray diffraction, and chemical composition analyses were employed to quantify differences in mineralogical compositions and material morphology. Ions present in seawater and variations in soil materials were shown to significantly influence ureolytic activity and precipitate mineralogy and morphology, however, calcite remained the predominant CaCO₃ polymorph in all experiments with relative percentages exceeding 80% by mass in all precipitates.

Production and characterization of bamboo-based activated carbon through single-step H3PO4 activation for CO2 capture

Bamboo is the fastest-growing plant and is abundant in Malaysia. It is employed as a starting material for activated carbon production and evaluated for its potential in CO₂ capture. A single-stage phosphoric acid (H₃PO₄) activation is adopted by varying the concentrations of H₃PO₄ between 50 and 70 wt.% at a constant temperature and holding time of 500°C and 120 min, respectively. The bamboo-based activated carbons are characterized in terms of product yield, surface area, and porosity, as well as surface chemistry properties. Referring to the experimental findings, the prepared activated carbons have BET surface area of >1000 m² g^-1, which implies the effectiveness of the single-stage H₃PO₄ activation. Furthermore, the prepared activated carbon via 50 wt.% H₃PO₄ activation shows the highest BET surface area and carbon dioxide (CO₂) adsorption capacity of 1.45 mmol g^-1 at 25°C/1 bar and 9.0 mmol g^-1 at 25°C/30 bar. With respect to both the characterization analysis and CO₂ adsorption performance, it is concluded that bamboo waste conversion to activated carbon through H₃PO₄ activation method is indeed promising.