Characterisation and use of biomass fly ash in cement-based materials

Turning Waste into Greener Cementitious Building Material: Treatment Methods for Biomass Ashes-A Review

The production of biomass ash (BA) is expected to increase in the future, as biomass is generally considered a carbon-neutral fuel. BA potentially concentrates heavy metals and trace elements at high levels. With the growing production of BA, its disposal in landfills or recycling must be addressed through solid waste policies and within the framework of a circular economy. Utilizing BA as a cement substitute solves disposal issues while offering environmental benefits aligned with the circular economy. However, the varying physical and chemical properties of BA, influenced by factors such as biomass type and combustion technique, necessitate more effective utilization strategies. Consequently, researchers are developing various treatment methods to ensure that BA meet the necessary requirements and do not pose problems such as heavy metal or chlorine leaching. These treatments facilitate the production of concrete with higher compressive strength at greater cement replacement levels, supporting greener construction practices. This review consolidates existing BA data and treatment methods, focusing on their impacts and efficiency. It also explores combined treatments and potential new approaches. By providing a foundation for future research and practical applications, this study aims to improve treatment techniques, helping the industry mitigate environmental risks and advance carbon-neutral construction solutions.

3D-printing bauxite residue/fly ash-containing geopolymers as promising metal sorbents for water treatment

Herein, we demonstrate for the first time the feasibility of employing significant amounts (up to 80 wt%) of unexplored industrial wastes (red mud and biomass fly ash) in the production of highly porous 3D-printed geopolymer lattices envisioned for wastewater treatment applications. This without compromising the mechanical performance of the geopolymers relative to those obtained using commercial precursors. The impact of the fly ash incorporation content in the fresh-state (calorimetric and reological characterization) and hardened-state (porosity and mechanical strength) properties of the produced structures was evaluated. Moreover, the influence of key printing parameters, including nozzle diameter and geometry alignment, on the resulting properties of the lattices was also evaluated. The most promising compositions were then evaluated as lead sorbents under continuous flow. The waste-based 3D-printed lattices showed remarkable adsorption ability reaching >95 % removal efficiency after 2 h. This sustainable strategy is in line with the United Nations sustainable development goals and the transition to a circular economy, reducing the consumption of natural resources and simultaneously contributing to reducing water pollution.

The Effects of Phosphate Compounds on the Microstructure and Mechanical Properties of Fly Ash Geopolymer Mortars

Coal-fired power plants are a main source of energy in Poland. In the rapidly growing demand for the reduction of CO2 emission in the energy industry, the use of biomass for energy purposes has increased significantly. The combustion of biomass results in the generation of fly ash, with higher levels of CaO, K2O, P2O5, in contrast to the fly ash derived from the combustion of coal. The aim of this study was to examine the influence of phosphate compounds on fly ash-based geopolymer mortars. Geopolymers were made by mixing two types of fly ash-one from the combustion of wood biomass and the second from the combustion of coal in a heat and power station. Basic activators (NaOH and Na2SiO3) were used for the alkali activation. The maximum level of tetraphosphorus decaoxide addition was established at 5% of the total mass of the aluminosilicate precursors mass. The results showed that the phosphate oxide concentration within the specimens demonstrated a positive correlation with flexural and compressive strength across all temporal intervals (7, 28, and 56 days). The porosity, however, for samples with a 5% addition of P4O10, increased more than twofold in comparison to reference samples (from 4.26% to 9.98%).

Comparative Analysis of Woody Biomass Fly Ash and Class F Fly Ash as Supplementary Cementitious Materials in Mortar

Biomass fly ash is a sustainable, eco-friendly cement substitute with economic and performance benefits, being renewable compared to coal fly ash. This study examines using biomass fly ash (BFA) as a sustainable cement substitute, comparing it with Class F fly ash (CFA). With a water-binder ratio of 0.5 and replacement rates of 10%, 15%, 20%, 25%, and 30% (by mass), the research highlights BFA's promising applications. BFA and CFA were mixed into cement paste/mortar to analyze their reactivity and properties, with hydration products CH and C-S-H evaluated at 7, 28, and 91 days. Compressive strength, micro-pore structure, and drying shrinkage (assessed from 7 to 182 days) were tested. Results showed BFA had similar pozzolanic reactions to CFA at later stages. While compressive strength decreased with higher BFA replacement rates, early-stage performance matched CFA; growth was CFA-10 (18 MPa) and BFA-10 (17.6 MPa). BFA mortars exhibited slightly better deformation properties. BFA-30 cement had superior performance, with a lower drying shrinkage rate of 65.7% from 14 to 56 days compared to CFA-10's 73.4% and a more stable shrinkage growth rate decrease to 8.4% versus CFA-10's 6.4% after 56 days. This study concluded that BFA, usable without preprocessing, performed best at a 10-15% replacement rate.

Adsorption Efficiency of Cadmium (II) by Different Alkali-Activated Materials

The objective of this study was to demonstrate the potential utilization of fly ash (FA), wood ash (WA), and metakaolin (MK) in developing new alkali-activated materials (AAMs) for the removal of cadmium ions from waste water. The synthesis of AAMs involved the dissolution of solid precursors, FA, WA, and MK, by a liquid activator (Na2SiO3 and NaOH). In concentrated solutions of the activator, the formation of an aluminosilicate gel structure occurred. DRIFT spectroscopy of the AAMs indicated main vibration bands between 1036 cm-1 and 996 cm-1, corresponding to Si-O-Si/Si-O-Al bands. Shifting vibration bands were seen at 1028 cm-1 to 1021 cm-1, indicating that the Si-O-Si/Si-O-Al bond is elongating, and the bond angle is decreasing. Based on the X-ray diffraction results, alkali-activated samples consist of an amorphous phase and residual mineral phases. The characteristic "hump" of an amorphous phase in the range from 20 to 40° 2θ was observed in FA and in all AWAFA samples. By the XRD patterns of the AAMs obtained by the activation of a solid three-component system, a new crystalline phase, gehlenite, was identified. The efficiency of AAMs in removing cadmium ions from aqueous solutions was tested under various conditions. The highest values of adsorption capacity, 64.76 mg/g (AWAFA6), 67.02 mg/g (AWAFAMK6), and 72.84 mg/g mg/g (AWAMK6), were obtained for materials activated with a 6 M NaOH solution in the alkali activator. The Langmuir adsorption isotherm and pseudo-second kinetic order provided the best fit for all investigated AAMs.

Ashes from challenging fuels in the circular economy

In line with the objectives of the circular economy, the conversion of waste streams to useful and valuable side streams is a central goal. Ash represents one of the main industrial side-products, and using ashes in other than the present landfilling applications is, therefore, a high priority. This paper reviews the properties and utilization of ashes of different biomass power plants and waste incinerations, with a focus on the past decade. Possibilities for ash utilization are of uttermost importance in terms of circular economy and disposal of landfills. However, considering its applicability, ash originating from the heat treatment of chemically complex fuels, such as biomass and waste poses several challenges such as high heavy metal content and the presence of toxic and/or corrosive species. Furthermore, the physical properties of the ash might limit its usability. Nevertheless, numerous studies addressing the utilization possibilities of challenging ash in various applications have been carried out over the past decade. This review, with over 300 references, surveys the field of research, focusing on the utilization of biomass and municipal solid waste (MSW) ashes. Also, metal and phosphorus recovery from different ashes is addressed. It can be concluded that the key beneficial properties of the ash types addressed in this review are based on their i) alkaline nature suitable for neutralization reactions, ii) high adsorption capabilities to be used in CO2 capture and waste treatment, and iii) large surface area and appropriate chemical composition for the catalyst industry. Especially, ashes rich in Al2O3 and SiO2 have proven to be promising alternative catalysts in various industrial processes and as precursors for synthetic zeolites.

Wood fly ash and blast furnace slag management by alkali-activation: Trace elements solidification and composite application

Wood and biomass are burned in many industries as a sustainable energy source. The large quantities of fly ash produced must be landfilled, leading to environmental concerns. Precipitator wood fly ash (PFA) and ground granulated blast furnace slag (BFS) have been used in this study to prepare alkali-activated composites to manage and recycle the fly ash. After an essential characterization, the influence of parameters such as PFA and BFS content, alkaline activator content (silica moduli of 0, 0.82, 1.32), curing method, and curing duration on the mechanical, chemical, and microstructural properties of the samples have been studied through compressive strength, density, FTIR, and SEM-EDS investigations. The environmental safety and influence of polycondensation on heavy metal stabilization have been examined through ICP-MS. The results prove that oven and hydrothermal curing obtain the early age strength. Despite the variations of strength with duration and type of curing, the compressive strength of samples after 28 days of curing tends to close values for a constant PFA/BFS ratio, due to which the need for energy-intensive curing methods is addressed. ICP-MS shows that the composites can suitably solidify As, Cd, Ba, Cr, Pb, Mo, Se, Hg, Sr, Cu, and Zn. On the other hand, the composites were almost incapable of stabilizing Co and V. Unlike the case for mechanical properties; higher PFA content favours hazardous metal stabilization through polycondensation.

Experimental and numerical techniques to evaluate coal/biomass fly ash blend characteristics and potentials

Fossil and renewable fuels are used by industrial units that produce energy-intensive products. Competitive fuel pricing encourages these fuel sources' usage globally, particularly in developing nations, which leads to large volumes of byproducts like fly ash among thermal power plant operators. The elements and compounds found in coal fly ash (CFA) and biomass fly ash (BFA) can be utilized through several engineering applications. This study aims to assess typical CFA and BFA samples quantitatively and qualitatively via techniques such as ultimate analysis (CH-S), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray fluorescence (XRF) elemental analysis, and ash fusion temperature (AFT), to anticipate the ideal ratios of coal to biomass blends for combustion applications while adhering to environmental regulations. The optimal blend, consisting of 75 % CFA and 25 % BFA, exhibited improved carbon (C%) and hydrogen (H%) percentages, increasing from 2.5 % to 4.67 % and from 0 % to 0.12 %, respectively. These improvements were further confirmed by the observed functional groups in FTIR, indicating a rising trend in both carbon and hydroxyl groups from BFA to CFA. XRF and XRD also confirmed it and TGA also showed optimum mass loss (ML%) behavior of 14.55 % for 75CFA + 25BFA. According to slagging and fouling indices, the values of RB/A, Rs, and Fu indicate a reduction in slagging and fouling issues through the blending of CFA with BFA. Simultaneously, the fusion temperature increased from 1181 °C to 1207 °C. CFA was found to increase the AFT of the BFA from 1197 °C to 1247 °C, mitigating their propensity. This suggests that a blend of 75CFA + 25BFA results in lower to medium range of slagging and fouling. However, AFI and BAI indicate a slightly higher range. AFT analysis further validates the conclusions drawn from the indices. The ternary phase diagram shows that the ash's melting point increases in the optimum blend. This is attributed to a reduced content of K2O (<15 %) and increased proportions of >50 % CaO and SiO2, effectively inhibiting slagging, agglomeration, and deposition. Meanwhile, the blend maintains a medium level of acidity and susceptively to corrosion, as observed in the case of 75CFA + 25BFA. The identification of optimal blend ratios can be anticipated to offer essential solutions for future research, aiming to ensure smooth industrial operations and regulatory compliance in power plants.

The Effects of Partial Replacement of Ground Granulated Blast Furnace Slag by Ground Wood Ash on Alkali-Activated Binder Systems

Cement production contributes significantly to carbon dioxide emissions. Alkali-activated materials offer an environmentally friendly alternative due to their comparable strength, durability and low-carbon emissions while utilizing wastes and industrial by-products. Wood ash is a waste material that shows promising results as a partial replacement for Portland cement and precursors in alkali-activated systems. The aim of this study was to examine the effect of ground wood ash on the mechanical properties of alkali-activated mortars. Wood ash was incorporated as a 0 wt%, 10 wt% and 20 wt% partial replacement for ground granulated blast furnace slag (GGBFS). The wood ashes were ground in a planetary ball mill for 10 and 20 min. Sodium silicate (Na2SiO3), sodium carbonate (Na2CO3), and sodium hydroxide (NaOH) were used as alkali activators. The results demonstrated that ground wood ash improved the mechanical properties of alkali-activated systems compared to untreated wood ash. However, the incorporation of wood ash increased the porosity of the binder matrix.

Strength and Microstructure Assessment of Partially Replaced Ordinary Portland Cement and Calcium Sulfoaluminate Cement with Pozzolans and Spent Coffee Grounds

Supplementary cementitious materials are considered a viable and affordable way to reduce CO₂ emissions from the cement industry's perspective since they can partially or nearly entirely replace ordinary Portland cement (OPC). This study compared the impact of adding spent coffee grounds (SCGs), fly ash (FA), and volcanic ash (VA) to two types of cement: OPC and calcium sulfoaluminate cement (CSA). Cement samples were characterized using compressive strength measurements (up to 210 days of curing), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), attenuated total reflection infrared spectroscopy, and hydration temperature measurements. In all the studied systems, the presence of SCGs reduced compressive strength and delayed the hydration process. CSA composite cement containing 3.5% SCGs, 30% FA, and 30% VA showed compressive strength values of 20.4 MPa and 20.3 MPa, respectively, meeting the minimum requirement for non-structural applications. Additionally, the results indicate a formation of cementitious gel, calcium silicate hydrate (C-S-H) in the OPC-based composite cements, and calcium alumino-silicate hydrate (C-A-S-H) as well as ettringite in the CSA-based composite cements.

Presence of aromatic-rich organic matter and its characterization in grout materials: Implications for radionuclide immobilization

Grout materials are commonly used to immobilize low-level radioactive waste. Organic moieties can be unintentionally present in common ingredients used to make these grout waste forms, which may result in the formation of organo-radionuclide species. These species can positively or negatively affect the immobilization efficiency. However, the presence of organic carbon compounds is rarely considered in models or characterized chemically. Here, we quantify the organic pool of grout formulations with and without slag, as well as the individual dry ingredients used to make the grout samples (ordinary Portland cement (OPC), slag and fly ash), including total organic carbon (TOC) and black carbon, followed by aromaticity evaluation and molecular characterization via Electro Spray Ionization Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FTICRMS). All dry grout ingredients contained significant amounts of organic carbon, ranging from 550 mg/kg to 6250 mg/kg for the TOC pool, with an averaged abundance of 2933 ± 2537 mg/kg, of which 60 ± 29% was composed of black carbon. The significant abundance of a black carbon pool implies the presence of the aromatic-like compounds, which was further identified by both phosphate buffer-assisted aromaticity evaluation (e.g., >1000 mg-C/kg as aromatic-like carbon in the OPC) and dichloromethane (DCM) extraction with ESI-FTICRMS analysis. Besides aromatic-like compounds, other organic moieties were also detected in the OPC, such as carboxyl-containing aliphatic molecules. While the organic compound only consists of minor fractions of the grout materials investigated, our observations of the presence of various radionuclide-binding organic moieties suggests the potential formation of organo-radionuclides, such as radioiodine, which might be present at lower molar concentrations than TOC. Evaluating the role of organic carbon complexation in controlling the disposed radionuclides, especially for those radionuclides with strong association with organic carbon, has important implications for the long-term immobilization of radioactive waste in grout systems.

Wood Ash as Sustainable Alternative Raw Material for the Production of Concrete-A Review

Different ecological binders have been used to minimize the negative effects of cement production and use on the environment. Wood ash is one of these alternative binders, and there has been increasing research related to this topic recently. The wood ash utilized in the literature primarily originates from power plants and local bakeries, and predominantly wood fly ash is used. This review paper examines the use of wood ash as an ecological binder in two different applications: as a cement replacement and as an alkali-activated material. Studies have shown that while increased wood ash content in concrete and mortars can have negative effects on strength and durability, it is still a promising and developable material. Depending on the chemical composition of the wood ash, the strength and durability properties of concrete might be slightly improved by utilizing wood ash as a replacement for cement, with an optimal replacement level of 10-20%. However, there is a need for more research regarding the effects of wood ash on the durability of cement-based materials and its use in alkali-activated materials. Overall, this review provides a comprehensive overview of the properties of wood ash and its potential applications in conventional concrete and mortars, as well as in alkali-activated materials.

The use of polymer compounds in the deposits from the combustion of briquettes in domestic heating as an identifier of fuel quality

The utilisation of waste wood from furniture production brings new problems connected with an incomplete thermochemical decomposition of additives (chemicals for improving properties of plastics) in small heating with the addition of sources. Unique organic compounds produced by the combustion of waste wood allow the identification of the type of fuel. The organic compounds contained in the char deposits were analysed by pyrolysis gas chromatography with mass spectrometry. The deposits from the combustion of briquettes from furniture production contain organic compounds originating by decomposition of phenolic resins, aminoplasts (urea-formaldehyde, resorcinol-formaldehyde and melamine), polyurethanes and wood glue. Additives contained in the deposits include plasticisers such as phthalates (DEHP, dibutyl phthalate and diisobutyl phthalate), flame retardants (2-propanol, 1-chlorophosphate (3:1) and p-terphenyl). Deposits from the combustion of briquettes from virgin wood do not contain these compounds. The total amount of compounds identified in the deposits from the boiler, which do not come from virgin wood combustion, varies in the range between 4.25 and 6.25 g/kg. Phthalates (55.5%) and PVAc adhesives (18.6%) are the main anthropogenic compounds in the deposits from domestic boilers.

Evaluation of Fly Ash from Co-Combustion of Paper Mill Wastes and Coal as Supplementary Cementitious Materials

The applications of waste-derived fuel from paper mills in industrial boilers benefit the reduction of carbon emissions. However, the co-combustion of waste-derived fuel and coal causes significant changes in the characteristics of the ash and brings about the need to find possible means of the utilization of the ash produced. In this work fly, ash samples were collected from circulating fluidized bed (CFB) boilers co-combusting paper mill wastes with coal and analyzed in detail. The chemical, physical, and thermal characteristics of two different co-combustion fly ashes (CCFA) were investigated using X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetry (TG), and scanning electron microscope (SEM). The chemical composition of CCFA is largely affected by the fuel source type. Thermal analyses of CCFA show that the type of desulfurization system used by the boiler influences the form of sulfate present in the fly ash. The presence of calcium sulfite hemihydrate can cause a high loss in the ignition of CCFA. By comparing the physical requirements specified in the ASTM standard for coal fly ash to be used in concrete, the CCFA produced from paper mill wastes was found to show good potential as supplementary cementitious materials.

A Review on Strength and Durability Properties of Wooden Ash Based Concrete

The partial replacement of cement in concrete with other building materials has come to light because of research on industrial waste and sustainable building practices. Concrete is made more affordable by using such components, and it also helps to ease disposal worries. Ash made by burning wood and other wood products is one example of such a substance. Many researchers focused on the utilization of wooden ash (WA) as a construction material. However, information is scattered, and no one can easily judge the impact of WA on concrete properties which restrict its use. Therefore, a details review is required which collect the past and current progress on WA as a construction material. relevant information. This review aims to collect all the relevant information including the general back of WA, physical and chemical aspects of WA, the impact of WA on concrete fresh properties, strength properties, and durability aspects in addition to microstructure analysis. The results indicate the WA decreased the slump and increased the setting time. Strength and durability properties improved with the substitution of WA due to pozzolanic reaction and micro-filling effects. However, the optimum dose is important. Different research recommends different optimum doses depending on source mix design etc. However, the majority of researcher suggests a 10% optimum substitution of WA. The review also concludes that, although WA has the potential to be used as a concrete ingredient but less researchers focused on WA as compared to other waste materials such as fly ash and silica fume etc.

Boiler ash utilization in the Canadian pulp and paper industry

Pulp and paper mill biomass boilers generate large quantities of ash in Canada with British Columbia (BC) being the highest ash generating province followed closely by Quebec. Generally, the generated ash is landfilled, particularly in BC, with only a small amount being used beneficially. It is anticipated that the difficulty associated with the management of ash will worsen over time as the industry increases its reliance on green fuel. Thus, there is a strong need to identify beneficial uses of pulp and paper boiler ash for the sake of environmental and economic sustainability. The purpose of this report is to provide the first step in this direction, a review of proposed or implemented uses for coal and hog (or wood) ash around the world. Considering both the properties of the ash and local opportunities, this could be the first step toward screening the applications that may apply to individual mills. Several large-scale practices use ash, such as land application (as a nutrient source or as a liming agent), use in the construction industry (as a replacement for cement or as a fill material), and reclamation of mine sites and stabilization of unpaved forest roads. In some cases, relatively small-scale applications have been used which included uses such as a compost component, agent for pH adjustment of liquid streams and slurries, blasting abrasive, and source of quartz for glass manufacturing to name a few. It is important to note that the chemical nature of both fly and bottom ashes can be quite variable due to the type of wood residues combusted as well as combustion equipment used and must be considered in identifying beneficial applications.

Biomass conversion of agricultural waste residues for different applications: a comprehensive review

Agricultural waste residues (agro-waste) are the source of carbohydrates that generally go in vain or remain unused despite their interesting morphological, chemical, and mechanical properties. With rapid urbanization, there is a need to valorize this waste due to limited non-renewable resources. Utilizing agro-waste also prevents the problems like burning and inefficient disposal that otherwise lead to immense pollution worldwide. In addition, conversion of biomass to value-added products like earthen cups, weaving baskets, and bricks is equally beneficial for the rural population as it provides secondary income, creates jobs, and improves rural people's lifestyles. This review paper will discuss an overview of different applications utilizing agro-waste residues. In particular, agro-wastes used as construction material, bio-fertilizers, pulp and paper products, packaging products, tableware, heating applications, biocomposites, nano-cellulosic materials, soil stabilizers, bioplastics, fire-retardant additive, dye removal, and biofuels will be summarized. Finally, several commercially available agro-waste products will also be discussed, emphasizing the circular economy.

Comparative Study of Experimental and Modeling of Fly Ash-Based Concrete

The application of supplementary cementitious materials (SCMs) in concrete has been reported as the sustainable approach toward the appropriate development. This research aims to compare the result of compressive strength (C-S) obtained from the experimental method and results estimated by employing the various modeling techniques for the fly-ash-based concrete. Although this study covers two aspects, an experimental approach and modeling techniques for predictions, the emphasis of this research is on the application of modeling methods. The physical and chemical properties of the cement and fly ash, water absorption and specific gravity of the aggregate used, surface area of the cement, and gradation of the aggregate were analyzed in the laboratory. The four predictive machine learning (PML) algorithms, such as decision tree (DT), multi-linear perceptron (MLP), random forest (RF), and bagging regressor (BR), were investigated to anticipate the C-S of concrete. Results reveal that the RF model was observed more exact in investigating the C-S of concrete containing fly ash (FA), as opposed to other employed PML techniques. The high R2 value (0.96) for the RF model indicates the high precision level for forecasting the required output as compared to DT, MLP, and BR model R² results equal 0.88, 0.90, and 0.93, respectively. The statistical results and cross-validation (C-V) method also confirm the high predictive accuracy of the RF model. The highest contribution level of the cement towards the prediction was also reported in the sensitivity analysis and showed a 31.24% contribution. These PML methods can be effectively employed to anticipate the mechanical properties of concretes.

Deciphering van der Waals interaction between polypropylene and carbonated fly ash from experimental and molecular simulation

Pollution emitted from power plants, including a considerable amount of fly ash (FA) and carbon dioxide (CO₂), annually increases and is challenging from an environmentally friendly and sustainable point of view. To date, laboratory-scaled approaches cannot efficiently replace the FA-landfilling and mitigate the stress from CO₂ emission. Here, a practically operatable fundamental work by combining carbonated FA (C-FA)-immobilizing CO₂ in FA-and polypropylene (PP) matrix is reported and reveals abnormal mechanical and thermal features clarified by calculating van der Waals (vdW) interaction from an atomic scale. This is the first study wherein the interaction between instantaneous dipole moment-induced PP and fillers is simulated and examined. The vdW interactions at the (hetero)interfaces are -59.66, -82.30, and -224.39 kJ mol^-1 Å^-2 for PP, calcium oxide (CaO; before carbonation), and calcium carbonate (CaCO₃; after carbonation), respectively, which provides concrete theoretical support for interesting findings such as the independence of tensile strength on filler loadings and "well-grown" interface-induced higher conductivity characteristics of the composites. Therefore, this work can offer practical solutions to mitigate pollution, provide a new perspective on fundamental physical interactions, and guide the development of practical next-generation composite materials.

Influence of Wood Fly Ash on Concrete Properties through Filling Effect Mechanism

This paper presents the results of an experimental study aimed at determining the influence of wood fly ash (WFA) from three Croatian power plants on the properties of concrete. First, the chemical and physical properties of WFA’s were determined. It was found that these properties are highly influenced by combustion technology, the type and parts of wood used as fuel, and the local operating conditions. Subsequently, workability, heat of hydration, stiffness development, 28-day compressive strength, apparent porosity, and capillary absorption were determined on concrete mixes prepared with WFA as cement replacement from 5–45% by weight. Cement replacement up to 15% with the finest WFA accelerated hydration, stiffness development, and increased compressive strength of concrete up to 18%, while replacement with coarser WFA’s led to a decrease in compressive strength of up to 5% and had more gradual heat liberation. The dominant effect that could explain these findings is attributed to the filler and filling effect mechanisms. At the same time replacement content of up to 45% had very little effect on capillary absorption and could give concrete with sufficiently high compressive strength to be suitable for construction purposes.

Assessment of the Possibility of Using Fly Ash from Biomass Combustion for Concrete

This article analyses the possibility of using fly ash from the combustion of wood–sunflower biomass in a fluidized bed boiler as an additive to concrete. The research shows that fly ash applied in an amount of 10–30% can be added as a sand substitute for the production of concrete, without reducing quality (compression strength and low-temperature resistance) compared to control concrete. The 28-day compressive strength of concrete with fly ash increases with the amount of ash added (up to 30%), giving a strength 28% higher than the control concrete sample. The addition of fly ash reduces the extent to which the compression strength of concrete is lowered after low-temperature resistance tests by 22–82%. The addition of fly ash in the range of 10–30% causes a slight increase in the water absorption of concrete. Concretes containing the addition of fly ash from biomass combustion do not have a negative environmental impact with respect to the leaching of heavy metal ions into the environment.

Influence of Mechanical and Mineralogical Activation of Biomass Fly Ash on the Compressive Strength Development of Cement Mortars

Biomass combustion is a significant new source of green energy in the European Union. The adequate utilization of byproducts created during that process is a growing challenge for the energy industry. Biomass fly ash could be used in cement composite production after appropriate activation of that material. This study had been conducted to assess the usefulness of mechanical and physical activation methods (grinding and sieving), as well as activation through the addition of active silica in the form of silica fume, as potential methods with which to activate biomass fly ash. Setting time, compressive strength, water absorption and bulk density tests were performed on fresh and hardened mortar. While all activation methods influenced the compressive strength development of cement mortar with fly ash, sieving of the biomass fly ash enhanced the early compressive strength of cement mortar. The use of active silica in the form of silica fume ensured higher compressive strength results than those of control specimens throughout the entire measurement period.

Pilot Scale Production of Precast Concrete Elements with Wood Biomass Ash

Downsizing fossil fuel dependence and greenhouse gas emissions is at the forefront of a sustainable future. The expansion of renewable energy while striving to minimize dependence on fossil fuels has led to biomass taking the lead among renewable energy sources, with wood having the broadest application. Along with the growing trend of using biomass as a renewable energy source, the combustion of wood biomass results in wood biomass ash (WBA), leading to compelling amounts of waste. In this study, the technical feasibility of fly WBA from different Croatian power plants was analyzed to evaluate its potential use in precast concrete drainage elements and curb units. By implementing a performance-based design, the influence of various factors in thermal processing of wood biomass was investigated, together with a detailed characterization of WBA in order to assess the feasibility of using WBA as a secondary raw material in a large-scale industrial batching plant. The compressive strength and durability properties (water absorption, permeability, and freeze–thaw resistance) of concrete mixtures with WBA as a replacement for 15 wt% cement were evaluated and compared with the precast concrete manufacturer’s technical requirements. The main concerns identified were compositional inconsistency of WBA, workability downturn, delay in initial reactivity rate, and increased water absorption. Concrete with WBA based on a circular design has been found to be a viable solution to cement depletion, stepping up from recycling to reuse of industrial waste.

Phase changes during various treatment processes for incineration bottom ash from municipal solid wastes: A review in the application-environment nexus

Incineration technology has been widely employed, as an effective method to decrease the volume of waste disposal. In this review, relationships between municipal solid waste (MSW) inputs and residues after combustion-specifically, the incineration bottom ashes (IBA) of MSW, were discussed, with an emphasis on the geoenvironmental impacts of IBA associated with the complex crystal and amorphous phase reactions and changes during combustion and from their downstream treatments, whereas, their influences on IBA leaching behaviors are considered as another focus. This review summarizes the IBA leaching behaviors based on literature, showing the leaching variabilities induced by natural weathering and artificial intervention conditions, such as accelerated carbonation, washing treatment, stabilization/solidification, and thermal treatments, all of which can be attributed to changes of mineral phases and microstructure. It helps to understand IBA characteristics and transitions in application-environment nexus, and better reuse it for multiple applications.

Characterisation of Industrial Side Streams and Their Application for the Production of Geopolymer Composites

This study focuses on characterisation of side streams including biomass fly ash, biomass bottom ash, coal fly ash, green liquor dregs, limestone mine tailings, and electric arc furnace steel slag from different industrial locations in Finland. It was found that the fly ash samples contained the highest Al2O3 and SiO2 concentrations, a large number of spherical particles of small sizes and high specific surface areas. Fly ashes and steel slag were observed to contain higher amounts of amorphous phases compared to the other side streams. The high loss on ignition value of the coal fly ash and green liquor dregs was found to exceed the limitations for their application in geopolymer composites. Despite their relatively high concentrations in ashes and steel slag, the leaching tests have shown that no hazardous metal leached out from the streams. Finally, test specimens of geopolymer composites (GP2) were prepared by the application of biomass fly ash, bottom ash, and limestone mine tailings without any pre-treatment process, in addition to the ordinary Portland cement-(R) and metakaolin-based geopolymer composites (GP1). The measured compressive (14.1 MPa) and flexural strength (3.5 MPa) of GP2 suggest that it could be used in concrete kerbs and paving flags. The data has also shown that over 500% of the compressive strength was developed between 7 and 28 days in GP2, whereas in the case of reference concrete (R) and the metakaolin-based geopolymer composite (GP1) it was developed in the first 7 days.

An Influence of the Fuel Type on Element Behaviour in Domestic Boilers with Respect to the Circular Economy

The use of waste from the regional production of waste wood, waste paper, and cardboard in the form of briquettes may be causing an increase in local emissions, both of major elements and trace elements. When burning paper and cardboard briquettes, more than 70% of Mn, Zn, As, and Pb is released into the air from the total content of trace elements in the fuel. The largest amounts of major and trace elements are released when burning paper briquettes (56 g/kg of fuel); half of these amounts are released from burning briquettes from waste wood and coal (23 g/kg of fuel). The pursuit of alternative uses for those cardboard components that are not suitable for recycling cannot be directed to the production of briquettes for residential combustion in the framework of the application of the principles of the circular economy. In particular, the high concentrations of undesirable elements in the emissions released in the gas phase into the atmosphere are an obstacle existing even when the parameters of the PM10 emissions of a boiler are met. This is related to the high ash content of the cardboard (13.5%). Waste paper or cardboard could be added to waste wood at a maximum of 10% to make the pollution produced comparable to the burning of coal briquettes.

Study of the Incorporation of Biomass Bottom Ash as a Filler for Discontinuous Grading Bituminous Mixtures with Bitumen Emulsion

Energy consumption, because of population development, is progressively increasing. For this reason, new sources of energy are being developed, such as that produced from the combustion of biomass. However, this type of renewable energy has one main disadvantage, the production of waste. Biomass bottom ash is a residue of this industry that currently has not much use. For this reason, this research evaluates its use as a filler in bituminous mixtures, since this sector also has a significant impact on the environment, as it requires large quantities of raw materials. With this objective, first, the physical and chemical properties of biomass bottom ashes were evaluated, verifying their characteristics for their use as filler. Subsequently, bituminous mixtures were conformed with biomass bottom ash as filler, and their physical and mechanical properties were analyzed through particle loss and Marshall tests. The results of these tests were compared with those obtained with the same type of mixture but with conventional and ophite aggregates. This study confirmed that biomass bottom ash was viable for use as a filler, creating mixtures with a higher percentage of bitumen, better mechanical behavior, and similar physical properties. In short, more sustainable material for roads was obtained with waste currently condemned to landfill.

Evaluation of Physical, Chemical, and Environmental Properties of Biomass Bottom Ash for Use as a Filler in Bituminous Mixtures

The road construction sector is one of the most raw material-intensive sectors in existence. As a result, it has a significant impact on the environment. For this reason, there are several research projects in which industrial by-products are used as raw materials. In turn, energy production from biomass combustion is considered to be one of the most promising energy sources. However, this type of energy produces a number of wastes that need to be treated, such as biomass bottom ash. This research evaluates the properties of biomass bottom ash for use as a filler in bituminous mixtures and quantifies the environmental advantages of its use. For this purpose, the chemical composition of the ashes was analysed and their properties were physically characterised to confirm their suitability as a filler. Subsequently, the advantages of its processing compared to limestone filler, lime, or cement were calculated with SimaPro software. The results showed acceptable properties of biomass bottom ash for use as a filler, as well as a drastic reduction in the environmental impact of its processing. In short, this research presents the basis for the development of further bituminous mixtures with biomass bottom ash, reducing the extraction of raw materials and avoiding landfill disposal.

Removal of Cadmium from Contaminated Groundwater Using a Novel Silicon/Aluminum Nanomaterial: An Experimental Study

Cadmium (Cd) is a harmful element to human health and biodiversity. The removal of Cd from groundwater is of great significance to maintain the environmental sustainability and biodiversity. In this work, a novel low-temperature roasting associated with alkali was applied to synthesize an eco-friendly adsorbent using coal fly ash. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray fluorescence, and X-ray photoelectron spectroscopy were applied to analyze the physical and chemical characteristics of the adsorbent. The experiments show that a significant improvement in specific surface area and activity of adsorbent was observed in this study. The functional groups of Na-O and Fe-O were verified to be beneficial in the removal of Cd²⁺. The material capacity to adsorb Cd²⁺ was considerably improved, and the maximum uptake capacity was 61.8 mg g^-1 for Cd²⁺ at 25 °C. Furthermore, pH and ionic strength play critical roles in the adsorption process. The Langmuir and pseudo-second-order models can appropriately describe the adsorption behavior, and the enhanced adsorption ability of Cd²⁺ by modified coal fly ash was attributed to ion-exchange, co-precipitation, and complexation. Higher sorption efficiency was maintained after two regeneration cycles. These results offer valuable insights to develop high-performance adsorbent for Cd²⁺ removal.

Evaluation of the permeability of high strength concrete using metakaolin and wood ash as partial replacement for cement

The present study is aimed to develop a high strength concrete by using mineral admixtures of wood ash (WA), metakaolin (MK), and chemical admixture. In order to check the compatibility, physical and chemical properties of the materials are studied. The specific gravity, bulk density and fineness of the ordinary Portland cement, wood ash and metakaolin have been studied. When compare to other materials, metakaolin has a more fineness and it implies the more reactivity than the wood ash. Similarly, the physical properties of the fine aggregate and coarse aggregates are also studies. And compressive strength, water absorption test, rapid chloride penetration test is also conducted. From the test report, it can be noted that the maximum compressive strength is achieved 83 N/mm2 in 10% WA + 20% MK blended concrete. The lowest water absorption and chloride permeability were obtained as 2.5% and 348 C respectively in 10% WA + 20% MK blended concrete. At the end of the experimental works, all obtained results were correlated with each other. The water absorption is well correlated with compressive strength (R2 = 84.9%) and charge passed (R2 = 91.5%). Finally, the cost analysis was carried out to understand the cost benefits of using the wood ash and metakaolin in high strength concrete.

A Mineral By-Product from Gasification of Poultry Feathers for Removing Cd from Highly Contaminated Synthetic Wastewater

Ash from poultry feather gasification was investigated as an adsorbent for Cd removal from synthetic wastewater under a range of operational conditions: initial pH (2–8) and salinity (8–38 mS/cm) of wastewater, ash dosage (2.5–50 g/L), Cd concentration (25–800 mg/L) and contact time (5–720 min). The ash was highly alkaline and had low surface area and micropores averaging 1.12 nm in diameter. Chemical/mineralogical analysis revealed a high content of P2O5 (39.9 wt %) and CaO (35.5 wt %), and the presence of calcium phosphate, hydroxyapatite and calcium. It contained only trace amounts of heavy metals, BTEX, PAHs and PCBs, making it a safe mineral by-product. Cd adsorption was described best with Langmuir and pseudo-second order models. At pH 5, an ash dosage of 5 g/L, 40 min contact time and 100 mg Cd/L, 99% of Cd was removed from wastewater. The salinity did not affect Cd sorption. The maximum adsorption capacity of Cd was very high (126.6 mg/g). Surface precipitation was the main mechanism of Cd removal, possibly accompanied by ion exchange between Cd and Ca, coprecipitation of Cd with Ca-mineral components and Cd complexation with phosphate surface sites. Poultry ash effectively removes high concentrations of toxic Cd from wastewater.

Distribution of PAHs in coal ashes from the thermal power plant and fluidized bed combustion system; estimation of environmental risk of ash disposal

The comparison of fly ash generated from lignite combustion in a thermal power plant Kolubara A (Veliki Crljeni) and bottom and fly ash from coal waste combustion in a semi-industrial fluidized bed boiler (Vinča) was performed as the function of particle size. The average total concentrations of the 16 EPA priority PAHs in ash fractions are 0.49 mg kg^-1 of ash (thermal power plant) and 17.48 mg kg^-1 of ash (fluidized bed boiler). The sum of 3- and 4-ring PAHs accounts for more than 93% of overall PAHs concentration, and the most abundant among them is fluoranthene. The portions of PAHs groups defined based on their physico-chemical properties, as obtained from quantitative structure-activity relationship (QSAR) models included in the Vega platform, were determined. These portions, emission factors, and benzo[a]pyrene equivalence concentrations were further on used to estimate the potential environmental impact of ash disposal. The PAHs emission factors are higher compared to values in the air pollutant emission inventory guidebook of the cooperative program for monitoring and evaluation of the long-range transmission of air pollutants in Europe (EMEP/EEA). The overall emission factors of 16 PAHs for combustion of lignite and coal waste are determined to be 0.15 and 249.97 mg kg^-1 of fuel, respectively. Based on the ratios of benzo[a]pyrene equivalence concentrations of each ash and correspondent fuel, the disposal of fly ash from the cyclone of fluidized bed boiler represents the highest risk to the environment among tested ashes.

Waste Recovery through Thermochemical Conversion Technologies: A Case Study with Several Portuguese Agroforestry By-Products

Agroforestry waste stores a considerable amount of energy that can be used. Portugal has great potential to produce bioenergy. The waste generated during agricultural production and forestry operation processes can be used for energy generation, and it can be used either in the form in which it is collected, or it can be processed using thermochemical conversion technologies, such as torrefaction. This work aimed to characterize the properties of a set of residues from agroforestry activities, namely rice husk, almond husk, kiwi pruning, vine pruning, olive pomace, and pine woodchips. To characterize the different materials, both as-collected and after being subjected to a torrefaction process at 300 °C, thermogravimetric analyses were carried out to determine the moisture content, ash content, fixed carbon content, and the content of volatile substances; elementary analyses were performed to determine the levels of carbon, nitrogen, hydrogen, and oxygen, and the high and low heating values were determined. With these assumptions, it was observed that each form of residual biomass had different characteristics, which are important to know when adapting to conversion technology, and they also had different degrees of efficiency, that is, the amount of energy generated and potentially used when analyzing all factors.

Evaluation of Alternative Home-Produced Concrete Strength with Economic Analysis

Ready-mix concrete is not always affordable because it is less economical for small projects. This study shows an effort to introduce alternative home-produced concrete for small paving areas such as sidewalks, backyards, or fixing the existing concrete and discusses the economic evaluation of the alternative concrete for home purpose. The materials being used in this study are available locally or are easily purchased. The primary objective of the study is to analyze the compressive strength and conduct economic analysis of alternative home-produced concrete with different mix designs. Wood ash, fly ash, and recycled aggregate concretes are the alternative concrete types discussed in this study. Fly ash can replace Portland cement up to 30% without losing significant compressive strength of the concrete. Furthermore, fly ash is less expensive than Portland cement and can reduce the cost of concrete by saving approximately 15%. Wood ash can be used up to 25% in concrete without losing considerable strength which saves approximately 13% of cement cost. The use of recycled concrete aggregates saves only about 1% CO2 emission compared to regular concrete while fly ash saves more than 28.5% and wood ash saves almost 24.5%. They can replace natural aggregates up to 100%, but there is only a 5% saving. In addition, an equivalent cost of USD 13.47 for one cubic yard of concrete could be saved by using 30% fly ash concrete when considering reduced emitted CO2eq from the material production.

Torrefied Biomass as an Alternative in Coal-Fueled Power Plants: A Case Study on Grindability of Agroforestry Waste Forms

The use of biomass as a renewable energy source is currently a reality, mainly due to the role it can play in replacing fossil energy sources. Within this possibility, coal substitution in the production of electric energy presents itself as a strong alternative with high potential, mostly due to the possibility of contributing to the decarbonization of energy production while, at the same time, contributing to the circularization of energy generation processes. This can be achieved through the use of biomass waste forms, which have undergone a process of improving their properties, such as torrefaction. However, for this to be viable, it is necessary that the biomass has a set of characteristics similar to those of coal, such that its use may occur in previously installed systems. In particular, with respect to grindability, which is associated with one of the core equipment technologies of coal-fired power plants—the coal mill. The objective of the present study is to determine the potential of certain residues with agroforestry origins as a replacement for coal in power generation by using empirical methods. Selected materials—namely, almond shells, kiwifruit pruning, vine pruning, olive pomace, pine woodchips, and eucalyptus woodchips—are characterized in this regard. The materials were characterized in the laboratory and submitted to a torrefaction process at 300 °C. Then, the Statistical Grindability Index and the Hardgrove Grindability Index were determined, using empirical methods derived from coal analysis. The results obtained indicate the good potential of the studied biomasses for use in large-scale torrefaction processes and as replacements for coal in the generation of electrical energy. However, further tests are still needed, particularly relating to the definition of the ideal parameters of the torrefaction process, in order to optimize the grindability of the materials.

Preparation of ultrafine fly ash by wet grinding and its utilization for immobilizing chloride ions in cement paste

In this study, to promote the chloride binding capacity of coal fired fly ash (RFA) in cementitious materials, wet grinding was employed and ultrafine fly ash (UFA) with D50 = 2.1 μm was prepared; SEM, XRD, TG, FTIR, and XPS were used to evaluate the chemical and physical change in the process of wet grinding. Then, two kinds of binders composed of cement and FA were designed, and the chloride immobilization was comparatively studied in terms of chemical binding, physical binding, and migration resistance. The hydration behavior and hydrates were investigated in terms of TGA, XRD, NMR, and MIP. Results revealed that UFA exhibited higher pozzolanic reactivity due to the increase of specific surface area, destruction of original molecular structure, and exposure of active reaction sites. And chloride immobilization in cement-UFA system was much greater than that in cement-RFA system at ages of 7 d and 28 d. The mechanism behind was discussed in three aspects: (a) chemical binding was promoted because of the more produced chloroaluminates facilitated by the release of aluminum from UFA; (b) physical adsorption was strengthened at 7 d but weakened at 28 d, resulting from the opposite influence on the amount of C-S-H gel at different ages; (c) migration resistance was improved by the reduction of pore volume and the increase in the complexity of pore structure. This investigation provided one new method for processing FA to promote the chloride immobilization of cement-FA system.

Use of biomass ash from different sources and processes in cement

Substitution of cement clinker with suitable excess materials from other processes is an effective way to reduce CO2 emissions of cement production. Moreover, specific properties of the resulting mortar or concrete can be designed with different clinker replacement materials and their mixing ratios. In this study, bottom and fly ashes from six biomass power plants with different power scales and various flue-gas treatment strategies were admixed to mortars, whose properties (influence of water requirement and final compressive strength) were then assessed in the laboratory by following industrial standard procedures. Results reveal that fly ash from a cyclone of a medium-scale combustor burning Miscanthus straw amended with 2 wt % Ca(OH)2 (to prevent slagging during combustion) turned out to be well suited as a clinker replacement material, even boosting final compressive strength of the mortar. Wood-chip bottom ashes and fly ash from a cyclone exhibited acceptable results, whereas fly ash from electrostatic precipitators (ESPs) and baghouse filters lowered final compressive strength of the mortar when admixed. The scale of the power plant is positively correlated with final compressive strength in the case of ESPs. Cenospheres, typical fly ash particles present in cyclone ash, seem to have a positive effect on water-to-binder ratio and final compressive strength. In contrast, potassium salts, which are most abundant in ash from ESPs and baghouse filters, appear to have a negative influence on these properties. Grinding of the biomass ashes to a typical Portland cement fineness had a positive effect on mortar quality. All fly ashes had high contents of Cd, and baghouse filter ash contained As in amounts about four times the Swiss limit value for cement of 30 ppm; only bottom ash and cyclone ash from Miscanthus exhibited concentrations below respective limit values for all critical trace elements. To assess the immobilization potential of contaminating elements during the cement hardening process, blended mortars were crushed and subjected to multistep leaching, followed by subsequent analysis of the leachates by atomic absorption spectroscopy. Immobilization of Cd by the mortar was particularly effective. Our results indicate that fly ash from wood-chip combustion is most suitable as an amendment to cement when it was trapped by a cyclone rather than by the ESPs or baghouse filters.

Study of the Incorporation of Biomass Bottom Ashes in Ceramic Materials for the Manufacture of Bricks and Evaluation of Their Leachates

Scarcity of raw materials, reduction of greenhouse gas emissions and reduction of waste disposal in landfills are leading to the development of more sustainable building materials. Based on these lines, this work studies the incorporation of biomass bottom ashes into ceramic materials for brick manufacture, in order to reuse this currently unused waste and reduce clay extraction operations. To this end, different groups of samples were made with different combinations of clay and biomass bottom ashes, from 100% clay to 100% biomass bottom ashes. These samples were shaped, sintered and subjected to the usual physical tests in ceramics. In turn, the mechanical resistance, color and leaching of the contaminating elements present were studied. The physical and mechanical tests showed that the results of all the families were adequate, achieving compressive strengths of over 20 MPa and leaching of the contaminating elements acceptable by the regulations. Therefore, a sustainable range of ceramics was developed, with specific properties (porosity, density, resistance and color), with a waste that is currently unused and sustainable with the environment.

Utilization of Fly Ashes from Fluidized Bed Combustion: A Review

Traditionally fly ash is thought to be glassy, spherical particle originating from pulverized coal combustion (PCC) at temperature up to 1700 °C. However, nowadays fluidized bed combustion (FBC) technology is spreading quickly around the world as it is an efficient and environmentally friendly method. FBC is also able to utilize mixtures of low-grade solid fuels (e.g., coal, lignite, biomass, and waste) that have fluctuating quality, composition, and moisture contents. However, this leads to a high variation in the produced fly ash quality, unlike PCC fly ash, and hence challenges when attempting to utilize this fly ash. In this study, the utilization of fluidized bed combustion fly ash (FBCFA) was reviewed using the Scopus database. The most promising utilization target for FBCFA from biomass combustion is as a fertilizer and soil amendment. In construction, the FBCFA from various fuels is utilized as cement replacement material, in non-cement binders, as lightweight aggregates and cast-concrete products. Other types of construction applications include mine backfilling material, soil stabilizer, and road construction material. There are also other promising applications for FBCFA utilization, such as catalysts support material and utilization in waste stabilization.

Wood Bottom Ash and GeoSilex: A By-Product of the Acetylene Industry as Alternative Raw Materials in Calcium Silicate Units

The main objective of this research was to obtain calcium silicate units from alternative raw materials, such as the bottom ashes from the combustion of wooden boards (WBA), as a source of silica, and GeoSilex (G), a by-product with low energy and environmental costs generated in the manufacture of acetylene, as a source of lime. Once the raw materials were physically, mineralogically and chemically characterized, calcium silicate units were obtained by mixing different amounts of WBA residue (90–20 wt%) and G by-product (10–80 wt%). The mixtures were compressed at 10 MPa and cured in water for 28 days. The calcium silicate units were subjected to a wide experimental program that included the determination of physical properties (bulk density, apparent porosity and water absorption), mechanical properties (compressive strength), and thermal properties (thermal conductivity). Optimum values are obtained for calcium silicate units that contain a 1/1 WBA/G weight ratio, which have an optimal amount of SiO₂ and CaO for the cementation reaction. The 50WBA-50g units have compressive strength values of 46.9 MPa and a thermal conductivity value of 0.40 W/mK. However, all calcium silicate units obtained comply with the European Standard EN 771-2: 2011 to be used as structural building materials.

A RADIATION DOSIMETRY ASSESSMENT OF WORKERS IN GREEK STYLE ROTISSERIES THAT USE PELLETS CONTAMINATED BY 137Cs AND 90Sr

This work evaluates the 137Cs and 90Sr content of wood pellets of the Greek energy market and additionally calculates worker exposure in Greek catering establishments (rotisseries). Wood pellets and ash samples were analysed through high resolution gamma-ray spectroscopy and liquid scintillation. Imported pellets had higher 137Cs concentrations, especially pellets that were imported in bulk. Greek pellets had very smaller 137Cs amounts. Despite the high variation in 137Cs content the 137Cs exemption levels were not exceeded in any case. However, if an enrichment factor of 300 is assumed, some ashes samples may exceed 13000 Bq/kg. The highest amounts of 90Sr were measured in ashes from pellets manufactured abroad in 2015, with up to 1060 Bq/kg. A linear regression model of the ratio of 137Cs to 90Sr activity followed our data well, and other sets of data partially. A dosimetry assessment of kitchen employees revealed that maximum possible dose intake reached 400 nSv/year.

Physicochemical and mineralogical characterization of biomass ash from different power plants in the Upper Rhine Region

Bottom and fly ash samples from six biomass power plants with different power scales and various flue gas treatment strategies were collected and analyzed in regard to their mineralogical composition, and their bulk major and trace element contents, all of which are of concern for regulations on biomass ash for further utilization. Furthermore, individual ash particles were investigated by scanning electron microscopy to characterize their physicochemical microstructures. Thermal behavior of wood-pellet ash, i.e. decomposition processes and mineral transformations during combustion, was indicated by thermogravimetric analysis and X-ray diffraction. Results reveal extensive variation of physicochemical features across the different ash types: wood-chip fly ash from electrostatic precipitators mainly consisted of water-soluble salts, whereas wood-chip fly ash from cyclones contained predominantly cenospheres (hollow spherical fly ash particles) and higher heavy metal concentrations. In addition, the fuel type and admixture had influences on ash compositions; some fuels like Miscanthus straw require a liming agent such as calcium hydroxide to be admixed to prevent fouling, which is then predominantly found in the ash. Furthermore, boiler size had an influence on fly ash composition. Cadmium concentrations were elevated in some fly ash samples at levels of concern for further utilization, whereas concentrations of troublesome Cr(VI) were below the detection limit for all investigated ash samples. Other contaminating elements such as Ni, Pb and Zn were variable but below limit values. Results clearly show that the nature of biomass ash calls for careful analyses prior to further application as, e.g., cement clinker replacement material.

Effect of Dry-Wet Ratio on Properties of Concrete Under Sulfate Attack

In order to explore the drying–wetting cycle test method of concrete under sulfate accelerating erosion, the influence of dry–wet time ratio on concrete sulfate erosion was studied. Under the condition of 7 days for one cycle, five different dry–wet time ratios were designed: 1:3, 1:1, 3:1, 5:1, and 10:1. The basic properties such as compressive strength, splitting tensile strength and dynamic elastic modulus of concrete were tested. Scanning electron microscopy (SEM) was used to analyze the microstructure of concrete before and after erosion. The test results show that under the environment of sulfate drying–wetting cycle erosion, the change of mechanical properties of concrete are divided into three stages: ascending period, fluctuating period and rapid descending period. Concrete is subjected to periodic damage process of initial damage followed by filling compaction, cracking, further filling, and cracking again, in that order. Dry–wet ratio has a significant effect on concrete sulfate attack. Under the same drying–wetting cycle period, as the dry–wet ratio increases, the degree of deterioration of concrete by sulfate attack increases first and then decreases. When the dry–wet ratio is 5:1, the deterioration is the most serious.

Comparison of the Characteristics of Fly Ash Generated from Bio and Municipal Waste: Fluidized Bed Incinerators

European solid waste incinerator plants still primarily use grate furnace technology, although circulating fluidized bed (CFB) technology is steadily expanding. Therefore, few investigations have reported on the environmental assessment of fly ash from fluidized incinerators. This research project aims to integrate information on fly ash derived from the combustion of municipal solid waste (FA1) and biomass (FA2) in fluidized bed incinerator facilities. Fly ash samples were comparatively analyzed by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES) to study the mineralogy, morphology, total heavy metal content, and leaching behavior, respectively. The analysis revealed that the two types of fly ash differ in their characteristics and leaching behavior. The concentration of most of the heavy metals in both is low compared to the literature values, but higher than the regulatory limits for use as a soil conditioner, whereas the high contents of Fe, Cu, and Al suggest good potential for metal recovery. The leaching ability of most elements is within the inert waste category, except for Hg, which is slightly above the non-hazardous waste limit.