It is essential to predict the mining-induced subsidence for sustainable mine management. The maximum observed subsidence having a noticeable areal extent due to Northern Upper Panels (NUP) and Southern Lower Panels (SLP) at the Barapukuria longwall coal mine is 5.8 m and 4.2 m, respectively, after the extraction of a 10 m thick coal seam. The mining-induced subsidence was simulated by the Displacement Discontinuity Method. The numerical model considered the effects of the ground surface, mining panels, faults, and the dyke. The predicted and the observed subsidence due to the mining of NUP and SLP were compared by varying Young's modulus, and the 0.10 GPa Young's modulus was found to be the best match in the geo-environmental condition. The effects of the faults and the dyke in the calculation were negligible. Future subsidence was predicted by considering 30 m extraction of the thick coal seam as 15.7-17.5 m in NUP and 8.7-10.5 m in SLP. The vulnerable areas demarcated considering the tilt angle and extensile strain might extend up to the coal mine office area and some villages.
The carbon dioxide emissions from Portland cement production have increased significantly, and Portland cement is the main binder used in self-compacting concrete, so there is an urgent need to find environmentally friendly materials as alternative resources. In most developing countries, the availability of huge amounts of agricultural waste has paved the way for studying how these materials can be processed into self-compacting concrete as binders and aggregate compositions. Therefore, this experimental program was carried out to study the properties of self-compacting concrete (SCC) made with local metakaolin and coal bottom ash separately and combined. Total 25 mixes were prepared with four mixes as 5, 10, 15, and 20% replacement of cement with metakaolin; four mixes as 10, 20, 30, and 40% of coal bottom ash as partial replacement of fine aggregates separately; and 16 mixes prepared combined with metakaolin and coal bottom ash. The fresh properties were explored by slump flow, T50 flow, V-funnel, L-box, and J-ring sieve segregation test. Moreover, the hardened properties of concrete were performed for compressive, splitting tensile and flexural strength and permeability of SCC mixtures. Fresh concrete test results show that even if no viscosity modifier is required, satisfactory fresh concrete properties of SCC can be obtained by replacing the fine aggregate with coal bottom ash content. At 15% replacement of cement with local metakaolin is optimum and gave better results as compared to control SCC. At 30% replacement of fine aggregate is optimum and gave better results as compared to control SCC. In the combined mix, 10% replacement of cement with metakaolin combined with 30% replacement of fine aggregate with coal bottom ash is optimum and gave better results as compared to control SCC.
Catalytic steam gasification of palm kernel shell is investigated to optimize operating parameters for hydrogen and syngas production using TGA-MS setup. RSM is used for experimental design and evaluating the effect of temperature, particle size, CaO/biomass ratio, and coal bottom ash wt% on hydrogen and syngas. Hydrogen production appears highly sensitive to all factors, especially temperature and coal bottom ash wt%. In case of syngas, the order of parametric influence is: CaO/biomass>coal bottom ash wt%>temperature>particle size. The significant catalytic effect of coal bottom ash is due to the presence of Fe2O3, MgO, Al2O3, and CaO. A temperature of 692°C, coal bottom ash wt% of 0.07, CaO/biomass of 1.42, and particle size of 0.75mm are the optimum conditions for augmented yield of hydrogen and syngas. The production of hydrogen and syngas is 1.5% higher in the pilot scale gasifier as compared to TGA-MS setup.
Biomass co-firing with coal can be adopted in the electricity sector to promote greenhouse gas reduction, renewable energy production, and resource efficiency improvement toward environmental sustainability. This realization, however, requires effective management of supply chain issues, such as the collection of biomass feedstock, the transportation of biomass, and the localization of biomass processing plants to deliver the co-firing scales needed. This work addresses these issues by providing a techno-economic assessment conducted in a spatially-explicit manner to investigate the opportunity for scaling up the co-firing deployment at the national scale. The modeling approach is applied to the case of Malaysia's coal and palm oil biomass industries. The number of cases involving the impact of energy decarbonization targets, economic policy instrument, and supply chain cost parameter variations on the co-firing scales deployed are assessed. The findings show that densified biomass feedstock can substitute significant shares of coal capacities to deliver up to 29 MtCO2/year of carbon dioxide reduction. Nevertheless, this would cause a surge in the electricity system cost by up to 2 billion USD/year due to the substitution of up to 40% of the coal plant capacities. In facilitating the maximal deployment of co-firing at the national scale, more than 100 solid biofuel production plants would need to be built to support a maximum of 41 TWh/year of co-firing capacity. Actions to minimize the specific cost elements of the biomass co-firing supply chain are thus needed in the near term to increase the effectiveness of economic policy instrument to promote co-firing and reduce environmental emissions.
Various environmental samples (seawater, TSS, sediment, rainwater and fly ash) from eight different stations near Kapar coastal area were analyzed. The 210 Po activity concentrations in liquid samples (seawater and rainwater) varied between 0.34 ± 0.03 mBq L-1 to 22.44 ± 0.53 mBq L-1 . Whereas the concentrations in particulate samples (TSS, sediment and fly ash) varied between 43.79 ± 2.31 Bqkg-1 to 364.48 ± 5.43 Bqkg-1 . Results also showed the radioactivity in Kapar coastal is higher than most of Malaysian coast, reaching a factor of seven. This condition is mainly due to the operation of a coal-fired power plant nearby. This study also clarify the variability of 210 Po in environment was strongly influenced from rainfall events especially during wet seasons.
The thermochemical processes such as gasification and co-gasification of biomass and coal are promising route for producing hydrogen-rich syngas. However, the process is characterized with complex reactions that pose a tremendous challenge in terms of controlling the process variables. This challenge can be overcome using appropriate machine learning algorithm to model the nonlinear complex relationship between the predictors and the targeted response. Hence, this study aimed to employ various machine learning algorithms such as regression models, support vector machine regression (SVM), gaussian processing regression (GPR), and artificial neural networks (ANN) for modeling hydrogen-rich syngas production by gasification and co-gasification of biomass and coal. A total of 12 machine learning algorithms which comprises the regression models, SVM, GPR, and ANN were configured, trained using 124 datasets. The performances of the algorithms were evaluated using the coefficient of determination (R2), root mean square error (RMSE), mean square error (MSE), and mean absolute error (MAE). In all cases, the ANN algorithms offer superior performances and displayed robust predictions of the hydrogen-rich syngas from the co-gasification processes. The R2 of both the Levenberg-Marquardt- and Bayesian Regularization-trained ANN obtained from the prediction of the hydrogen-rich syngas was found to be within 0.857-0.998 with low prediction errors. The sensitivity analysis to determine the effect of the process parameters on the model output revealed that all the parameters showed a varying level of influence. In most of the processes, the gasification temperature was found to have the most significant influence on the model output.
Humic acid (HA) is a complex organic compound made up of small molecules. A variety of raw materials are used to manufacture HA, due to which the structure and composition of HA vary widely. In this study, nitric acid oxidation of two coal samples from Lakhra (Pakistan) was followed by HA extraction using 2.5, 3.0 and 3.5% KOH solutions. The impact of different operating parameters such as; the effect of KOH concentrations, KOH-coal proportion, extraction time and pH range influencing the HA extraction efficiency was optimally investigated. Commercial HA applications possess numerous challenges, including valuable applications and sub-optimal extraction techniques. A significant limitation of conventional experimental methods is that they can only investigate one component at a time. It is necessary to improve the current processing conditions, this can only be achieved by modelling and optimization of the process conditions to meet market demands. A comprehensive evaluation and prediction of HA extraction using Response Surface Methodology (RSM) are also being reported for the first time in this study. The maximum HA extraction efficiency of 89.32% and 87.04% for coal samples 1 and 2 respectively was achieved with the lowest possible pH of 1.09 (coal sample 1) and 1(coal sample 2), which is remarkably lower as compared to those reported in the literature for conventional alkaline extraction process. The model was evaluated for two coal samples through the coefficient of determination (R2), Root Means Square Error (RMSE), and Mean Average Error (MEE). The results of RSM for coal sample 1 (R2 = 0.9795, RMSE = 4.784) and coal sample 2 (R2 = 0.9758, RMSE = 4.907) showed that the model is well suited for HA extraction efficiency predictions. The derived humic acid from lignite coal was analyzed using elemental analysis, UV-Visible spectrophotometry and Fourier-transformed infrared (FTIR) spectroscopy techniques. Scanning Electron Microscopy (SEM) was applied to analyze the morphological modifications of the extracted HA after treatment with 3.5% KOH solution. For agricultural objectives, such as soil enrichment, enhancing plant growth conditions, and creating green energy solutions, this acquired HA can be made bioactive. This study not only establishes a basis for research into the optimized extraction of HA from lignite coal, but it also creates a new avenue for the efficient and clean use of lignite.
CO2 sequestration into coalbed seams is one of the practical routes for mitigating CO2 emissions. The adsorption mechanisms of CO2 onto Malaysian coals, however, are not yet investigated. In this research CO2 adsorption isotherms were first performed on dry and wet Mukah-Balingian coal samples at temperatures ranging from 300 to 348 K and pressures up to 6 MPa using volumetric technique. The dry S1 coal showed the highest CO2 adsorption capacity of 1.3 mmol g-1, at 300 K and 6 MPa among the other coal samples. The experimental results of CO2 adsorption were investigated using adsorption isotherms, thermodynamics, and kinetic models. Nonlinear analysis has been employed to investigate the data of CO2 adsorption onto coal samples via three parameter isotherm equilibrium models, namely Redlich Peterson, Koble Corrigan, Toth, Sips, and Hill, and four parameter equilibrium model, namely Jensen Seaton. The results of adsorption isotherm suggested that the Jensen Seaton model described the experimental data well. Gibb's free energy change values are negative, suggesting that CO2 adsorption onto the coal occurred randomly. Enthalpy change values in the negative range established that CO2 adsorption onto coal is an exothermic mechanism. Webber's pore-diffusion model, in particular, demonstrated that pore-diffusion was the main controlling stage in CO2 adsorption onto coal matrix. The activation energy of the coals was calculated to be below -13 kJ mol-1, indicating that adsorption of CO2 onto coals occurred through physisorption. The results demonstrate that CO2 adsorption onto coal matrix is favorable, spontaneous, and the adsorbed CO2 molecules accumulate more onto coal matrix. The observations of this investigation have significant implications for a more accurate measurement of CO2 injection into Malaysian coalbed seams.
The performance of Cu/TiO2/FA composite, a hybrid adsorbent-photocatalyst consisting of copper-doped titania particles supported on fly ash, was optimized, under visible light irradiation, for the removal of the model dye pollutant methyl orange (MO) by using a response surface methodology and Box-Behnken experimental design. Three independent variables were considered for the optimization study: catalyst/solvent dosage (0.5 - 2.0 g/L), irradiation time (30-120 min), and the initial concentration (5- 25 ppm) of the dye. A 99.91% rate of removal was achieved using 2 g/L dosage, 5 ppm initial concentration, and 100 min of irradiation time as the optimal operating conditions. The recorded trends support the hypothesis of a combined and synergic adsorption-photocatalytic degradation process which fully exploits the "capture and destroy" approach for pollutant removal.
Rapid urbanization and 'concretization' have increased the use of concrete as the preferred building material. However, the production of cement and other concrete-related activities, contribute significantly to both the carbon dioxide emissions and climate change. Agro-industrial wastes such as Palm Oil Fuel Ash (POFA) and Eggshell Powder (ESP) have been utilized in concrete as supplementary cementitious materials, to reduce the cement content, in order to minimize the carbon footprint and the environmental pollution associated with the dumping of waste. Both POFA and ESP have been utilized in ternary binder foamed concrete; however, higher content of cement replacement tends to reduce the concrete's strength significantly. Therefore, this research was conducted to study the influence of ternary binder foamed concrete, incorporating 30% POFA and 5-15% ESP by weight of the total binder, when reinforced with polypropylene (PP) fibres. Based on the results, the ternary binder foamed concrete showed better strength than the control foamed concrete due to the pozzolanic reaction and the addition of PP fibres slightly improved the strength. Furthermore, ternary binder foamed concrete can reduce up to 33.79% of the total CO2 emissions. In terms of cost, all ternary binder foamed concrete mixes reduced the overall cost of the mix. The lowest cost per 1 MPa was achieved by ternary binder foamed concrete mix which incorporated 30% POFA, 5% ESP and 0.20% PP fibres. However, the optimum S5 ternary binder foamed concrete mix, which incorporated 30% POFA, 10% ESP and 0.20% PP fibres, exhibited a cost of $3.74 per 1 MPa strength, which was $1.1 lower than the control foamed concrete. PP reinforced ternary binder foamed concrete is an eco-efficient and cost-effective concrete that can be used in numerous civil engineering applications, mitigating the environmental and the emissions generated by agro-industrial waste.
The borehole coal samples of Dhulia North Block from the Rajmahal Basin, Eastern India, were systematically analyzed based on the chemical composition and concentration of major and trace elements (including rare earth elements, REEs) to assess the distribution of REEs and their environmental implications with utilization potential. The Dhulia North Block coals are characterized by the predominant major oxides of SiO2, Al2O3, and Fe2O3, accounting for 94% of the total ash composition, indicating the presence of quartz, clay-rich minerals, and pyrite. Compared with the average world coal ash, the total REE content in the analyzed samples ranged from 341.0 to 810.4 ppm, which is substantially higher. Hot humid climate conditions with intermediate igneous source rocks of the basin were demonstrated by the major oxide ratios (Al2O3/TiO2 < 20) and plots of TiO2 with Al2O3 and Zr. The redox-sensitive elements such as V, Ni, Cr, and Co found in the Dhulia North Block coal indicate that an oxic sedimentary environment existed in the basin when coal was formed. The low sulfur content (1% in most samples) indicates freshwater conditions in the basin at the time of organic matter deposition. The outlook coefficient (Coutl) varies between 0.7 and 1.6, indicating that the Dhulia North Block coals are a prospective source of REEs. The Dhulia North Block coals are characterized by low H/C and O/C atomic ratios ranging from 0.56 to 0.90 and 0.10 to 0.22, respectively, and contain type-III kerogens, indicating gas-prone source rock. Further, the basic-to-acid oxide ratio suggested that Dhulia North Block coals were suitable for utilization during combustion processes.
The rapidly increasing generation of municipal solid waste (MSW) threatens the environmental integrity and well-being of humans at a global level. Incineration is regarded as a technically sound technology for the management of MSW. However, the effective management of the municipal solid waste incineration (MSWI) ashes remains a challenge. This article presents the global dynamics of MSWI ashes research from 1994 to 2018 based on a bibliometric analysis of 1810 publications (research articles and conference proceedings) extracted from the Web of Science database, followed by a comprehensive summary on the research developments in the field. The results indicate the rapid growth of annual publications on MSWI ashes research, with China observed as the most productive country within the study period. Waste Management, Journal of Hazardous Materials, Chemosphere and Waste Management & Research, which accounted for 35.42% of documents on MSWI research, are the most prominent journals in the field. The most critical thematic areas on this topic are MSWI ashes characterisation, dioxin emissions from fly ash, valorisation of bottom ash and heavy metal removal. The evolution of MSWI ashes treatment technologies is also discussed, together with the challenges and future research directions. This is the first bibliometric analysis on global MSWI ashes research based on a sufficiently large dataset, which could provide new insights for researchers to initiate further research with leading institutions/authors and ultimately advance this research field.
Current study concerns measurement of radioactivity levels in areas surrounding a 2420 MW thermal power plant fueled predominantly by bituminous coal. The concentrations of (226)Ra, (232)Th and (40)K in onsite bottom-ash were found to be 139 Bq/kg, 108 Bq/kg and 291 Bq/kg, respectively, the levels for these radiolnuclides in soil decreasing with distance from the power plant. At the plant perimeter the respective radionuclide concentrations were 87 Bq/kg, 74 Bq/kg and 297 Bq/kg. In a nearby town, the corresponding concentrations were 104 Bq/kg, 52 Bq/kg and 358 Bq/kg, suggestive of use of TENORM affected soils. The mean radium equivalent activities (Raeq) in soil and ash sample in the town were 205 Bq/kg and 316 Bq/kg, respectively. The Kapar plant ash/slag appears to contain a higher level of TENORM than the world average. The degree of contamination is much higher inside the town where slag has been mixed with topsoil as landfill or as simple domestic waste. For the prevailing levels of exposure and a worst case senario, the predicted committed effective dose due to ingestion and inhalation for intake durations of 1- and 30 years would be 4.2 μSv and 220 μSv, respectively.
Research for alternative binders has become a necessity due to cement's embodied carbon, climate change, and depletion of natural resources. These binders could potentially reduce our reliance on cement as the sole binder for concrete while simultaneously enhancing the functional characteristics of concrete. Theoretically, the use of finer particles in the cement matrix densifies the pore structure of concrete and results in improved properties. To validate this hypothesis, current research was designed to investigate how the value-added benefits of nano-silica (NS) and metakaolin (MK) in fly ash (FA)-blended cement affect the mechanical and durability characteristics of concrete when used as ternary and quaternary blends. Additionally, the cost-benefit analysis and environmental impact assessment were conducted. It was observed that the synergy of MK and NS used in FA-blended cement had a greater impact on enhancing the functional characteristics of concrete, while 10% MK as ordinary Portland cement (OPC) replacement and 1% NS as an additive in FA-blended OPC concrete was the optimum combination which achieved 94-MPa compressive strength at the age of 91 days and showed more than 25% increment in the flexural and splitting tensile strengths compared to the control mix (MS00). The ultrasonic pulse velocity and dynamic modulus of elasticity were significantly improved, while a significant reduction in chloride migration of 50% was observed. In terms of environmental impact, MS100 (30% FA and 10% MK) exhibited the least embodied CO2 emissions of 319.89 kgCO2/m3, while the highest eco-strength efficiency of 0.268 MPa/kgCO2·m-3 with respect to 28-day compressive strength was exhibited by MS101. In terms of cost-benefit, MS00 was determined the cheapest, while the addition of MK and NS increased the cost. The lowest cost of producing 1 MPa was exhibited by MS01 with a merely 0.04-$/MPa/m3 reduction compared to MS00.
The production of cement releases an enormous amount of CO2 into the environment. Besides, industrial wastes like silica fume and fly ash need effective utilization to reduce their impacts on the environment. This research aims to explore the influence of silica fume (SF) and fly ash (FA) individually and combine them as binary cementitious material (BCM) on the hardened properties and embodied carbon of roller compacted concrete (RCC). A total of ten mixes were prepared with 1:2:4 mix ratio at the different water-cement ratios to keep the zero slump of roller compacted concrete. However, the replacement proportions for SF were 5%-15%, and FA were 5%-15% by the weight of cement individually and combine in roller compacted concrete for determining the hardened properties and embodied carbon. In this regard, several numbers of concrete specimens (cubes and cylinders) were cast and cured for 7 and 28 days correspondingly. It was observed that the compressive strength of RCC is boosted by 33.6 MPa and 30.6 MPa while using 10% of cement replaced with SF and FA individually at 28 days, respectively. Similarly, the splitting tensile strength of RCC is enhanced by 3.5 MPa at 10% cement replaced with SF and FA on 28 days, respectively. The compressive and splitting tensile strength of RCC is increased by 34.2 MPa and 3.8 MPa at SF7.5FA7.5 as BCM after 28 days consistently. In addition, the water absorption of RCC decreased while using SF and FA as cementitious material individually and together at 28 days. Besides, the embodied carbon of RCC decreased with increasing the replacement level of SF and FA by the mass of cement individually and combined.
The quest for eco-sustainable binders like agro-wastes in concrete to reduce the carbon footprint caused by cement production has been ongoing among researchers recently. The application of agro-waste-based cementitious materials in binary concrete has been said to improve concrete performance lately. Coconut and groundnut shells are available in abundant quantities and disposed of as waste in many world regions. Therefore, the use of coconut shell ash (CSA) and groundnut shell ash (GSA) in a ternary blend provides synergistic benefits with Portland cement (PC) and may be sustainably utilized in concrete as ternary cementitious material (TCM). Therefore, this study presents concrete performance with CSA and GSA in a grade 30 ternary concrete. Two hundred ten numbers of standard concrete samples were cast for checking the fresh and mechanical properties of concrete at curing ages of 7, 28, and 90 days. After 28-day curing, the experimental results show an increment in compressive, tensile, and flexural strength by 11.62%, 8.39%, and 9.46% at 10% TCM cement replacement, respectively. The concrete density and permeability coefficient reduce as TCM's content increases. The modulus of elasticity after 90 days improved with the addition of TCM. The concrete's sustainability assessment indicated that the emitted carbon for concrete decreased by around 16% using 20% TCM in concrete. However, the workability of fresh concrete declines as TCM content increases.
Over the last three decades, the world has been facing the phenomenon of the ecological deficit as the ecological footprint is continuously rising due to the persistent decline of the per-capita bio-capacity. Moreover, there is a substantial increase in globalization and electricity consumption for the same period, and transportation is contributing to economic prosperity at the cost of environmental sustainability. Understanding the determinants of ecological footprint is thus critical for suggesting appropriate policies for environmental sustainability. As a result, this study analyzes the impacts of economic globalization, transportation, coal rents, and electricity consumption in ecological footprint in the context of the USA over the period 1995 to 2018. The data have been extracted from "Global Footprint Network," "Swiss Economic Institute," and "World Development Indicators." The current study has also applied the flexible Fourier form nonlinear unit root test to examine the stationarity among variables. For the empirical estimation, a novel technique, the "quantile auto-regressive distributive lag model," is applied in the study to deal with the nonlinear associations of the variables and to evaluate the long-term stability of variables across quantiles. The study's findings indicate that coal rents, transportation, and globalization significantly and positively contribute to the deterioration of ecological footprints at different quantile ranges in the short and long run. Electricity consumption is found to have a positive and significant impact at lower quantile ranges in the long run but not have a significant impact in the short run. The study suggested that lowering the dependence of the transport sector on fossil fuels, more use of hydroelectricity, and stringent strategies to curb coal consumption would be helpful to reduce the positive influence of these variables on ecological footprints in the USA.
Grog is an additive material that plays important roles in ceramic making. It improves the fabrication process of green bodies as well as the physical properties of fired bodies. Few low-cost materials and wastes have found their application as grog in recent years, thus encouraging the replacement of commercial grogs with cost-saving materials. Coal fly ash, a combustion waste produced by coal-fired power plant, has the potential to be converted into grog owing to its small particle sizes and high content of silica and alumina. In this study, grog was derived from coal fly ash and mixed with kaolin clay to produce ceramics. Effects of the grog addition on the resultant ceramics were investigated. It was found that, to a certain extent, the grog addition reduced the firing shrinkage and increased the total porosity of the ceramics. The dimensional stability of the ceramics at a firing temperature of 1200 °C was also not noticeably affected by the grog. However, the grog addition in general had negative effects on the biaxial flexural strength and refractoriness of the ceramics.
Fly ash (PFA) is a complex material produced after combustion in coal-fired power plants. About half of this fly ash is disposed as solid wastes. A possible alternative to disposal of the fly ash is the synthesis of zeolite. Zeolite Boggsite (Na37Ca74Al185Si775O192 7H2O) was synthesized from fly ash by hydrothermal treatment with NaOH solutions as identified by x-ray diffraction. The zeolite type and degree of crystallization were found to be dependent on the reaction conditions and mineralogy of the raw material, particularly in terms of the relative concentrations of SiO2 and Al2O3.
Characterisation of the leaching behaviour of coal fly ash from Tenaga Nasional Berhad (TNB) by using tank leaching test method has been reported. The leachability of the constituents such as major elements and toxic metals in the coal fly ash was studied. Eight renewed leachant solutions after 6 hours, 1, 2, 5, 8, 21, 36 and 64 days were investigated after filtration. The parameters namely pH, cumulative release regarding the major elements and toxic metals to duration were presented. The results showed that the pH solutions increased from pH 4 to neutral and remained stable during the test. It might have resulted from the large buffering capacity of the coal fly ashes. Five major elements namely Al, Ca, K, Mg and Na were detected with Ca concentration in the leachant solutions was the highest for all samples. Toxic metals such as As, Ba, Co, Cr, Mn, Ni, Pb, Se and Zn were found and the test showed consistent results on the As, Ba, Mn, Se and Zn in leachant solutions. The findings also showed that some of the toxic metal concentrations namely As, Ba, Cr, Pb and Se exceeded the maximum allowance of the guideline of drinking water quality in Malaysia and WHO. Obviously, proper waste management has to be applied in this scenario.