Search Results (57)

Biomass ashes are considered to be sustainable alternatives for fly ashes from hard coal combustion for the use as supplementary cementitious material (SCM). However, their diverse composition and properties are impeding their standardized use. This study aims to gain a better understanding of how composition affects performance. It investigates three wood ashes (one bottom ash, two fly ashes), one spelt husk ash and a mineral residue from sewage sludge ash after wet-chemical phosphorus recovery for their suitability as SCM. After characterization of the materials including the determination of environmentally relevant parameters, the reactivity was tested using the R³ test and mortar compressive strength with different substitution levels. The effect on hydration was studied in blends with Portland cement using isothermal calorimetry and X-ray diffractometry (XRD). The composition of the ashes differed significantly, also between the wood ashes. The wood ashes showed no significant reactivity (cumulative R³ heat lower than 125 J/g SCM after 7 days), while the spelt husk ash and the sewage sludge ash residue showed distinct reactivity with a cumulative R³ heat of 249 and 181 J/g SCM after 7 days, respectively. Following an initial period of unaffected hydration, the wood fly ashes were found to impede clinker reactivity. In contrast, the other materials exhibited no significant influence on the hydration process, aside from the consumption of portlandite by the reactive ones. The wood fly ashes also impaired strength development in blended mortar formulations (e.g., relative compressive strengths with a cement substitution level of 20 wt% after 28 days were <0.6), whereas the reactive spelt husk ash and the mineral residue were associated with a measurable contribution to strength gain (e.g., relative compressive strengths with a cement substitution level of 20 wt% after 28 days were >0.85). The wood bottom ash was the only material investigated which perfectly sustained mortar workability and rather acts like a nearly inert addition. The results show both the potential and the limitations of using different types of ash, which cannot be generalized due to the wide variation in raw materials and combustion conditions. Full article

Sustainable waste management is one of the most serious global challenges today. Reusing waste materials can be an effective alternative to landfill, while recovering valuable nutrients. The purpose of this six-year field study was to investigate the potential of bottom ash from combustion of bituminous coal or biomass and municipal sewage sludge, and different doses of the waste mixtures, as a micronutrient source for plants. Yield, concentration, concentration index, uptake and simplified balance of the micronutrients (manganese, iron, molybdenum, cobalt, aluminium) in plant biomass were measured. Results showed that the wastes differently affected the parameters studied, which generally increased via treatment as follows: coal ash, biomass ash < coal or biomass ash mixtures with sewage sludge < sewage sludge. Irrespective of treatment, micronutrient recovery rate followed the following trend: Mn > Mo > Fe > Co > Al, from 0.32–25.82% for Mn to 0.04–0.28% for Al. For individual elements, recovery depended on waste. For Mn, Fe and Al, the application of ash separately or in mixtures with sludge at higher doses reduced recovery (0.04–0.78%). For Mn, Fe, Al and Mo, the application of ash–sludge mixtures at lower doses increased recovery (0.11–5.82%), with the highest recoveries when sludge was used separately (0.28–25.82%). For Co, the separate application of sewage sludge and ash–sludge mixture at the lower dose increased recovery (2.41–2.52%), with the highest Co recovery following the separate application of coal ash (2.78%). Ash, sludge and their mixtures were a valuable source of micronutrients for plants. Ash–sludge mixtures improved micronutrient uptake compared to ash used separately. Application of these wastes as fertilisers aligns with the EU Action Plan on the Circular Economy and can contribute to achieving SDGs 2 and 12. Full article

This study describes the development and characterization of materials based on activated carbon (AC). Pellets composed of dried biomass of willow, knotweed, and maple were formed and pyrolyzed to obtain different types of AC. Nickel (Ni) nanoparticles were synthesized on these materials using a bottom-up strategy by impregnating the carbons with a nickel nitrate solution. To characterize the surface and structure of these materials, SEM, MP-AES, and DSC-TGA techniques were employed. The ash content was analyzed to determine the input of mineral components in the carbons. The DSC-TGA results showed good thermal stability for each of the carbons, even at a temperature of 800 °C. BET analysis was also conducted, and the isotherms revealed well-developed surfaces for most of the specimens. The high efficiency of the impregnation process was confirmed by the MP-AES results: 165 mg of Ni was deposited on 1 g of carbon derived from maple leaves. The adsorbed Ni was well distributed across the carbon surfaces, as demonstrated in micrographs taken with the SEM-EDS apparatus. A comparison with similar materials reported in other studies was also performed. Full article

Based on the low-carbon transition needs of coal-fired boilers, this study conducted industrial trials of direct biomass co-firing on a 620 t/h high-temperature, high-pressure circulating fluidized bed (CFB) boiler, gradually increasing the co-firing ratio. It used compressed biomass pellets, achieving stable 20 wt% (weight percent) operation. By analyzing boiler parameters and post-shutdown samples, the comprehensive impact of biomass co-firing on the boiler system was assessed. The results indicate that biomass pellets were blended with coal at the last conveyor belt section before the furnace, successfully ensuring operational continuity during co-firing. Further, co-firing biomass up rates of to 20 wt% do not significantly impact the fuel combustion efficiency (gaseous and solid phases) or boiler thermal efficiency and also have positive effects in reducing the bottom ash and SO_x and NO_x emissions and lowering the risk of low-temperature corrosion. The biomass co-firing slightly increases the combustion share in the dense phase zone and raises the bed temperature. The strong ash adhesion characteristics of the biomass were observed, which were overcome by increasing the ash blowing frequency. Under 20 wt% co-firing, the annual CO₂ emissions reductions can reach 130,000 tons. This study provides technical references and practical experience for the engineering application of direct biomass co-firing in industrial-scale CFB boilers. Full article

The forming methodology influences the physicochemical, mechanical, and microstructural properties. In this study, which aims to develop a geopolymeric material for potential insulation applications in buildings such as vertical walls, geopolymers were developed using industrial wastes from different industries: slate stone cutting sludge (SSCS) and chamotte (CH) were used as precursors, and olive stone bottom ash (OSBA) and sodium silicate (Na₂SiO₃) were used as alkaline activators. Two forming methods were evaluated: uniaxial pressing and casting of the material, varying the forming method and the liquid/solid ratio. The results showed that the pressed geopolymers achieved higher bulk densities (up to 2.13 g/cm³) and significantly higher compressive strength (28.04 MPa at 28 days), attributable to a higher compactness and degree of geopolymer reaction. In contrast, the casting geopolymers exhibited surface efflorescence, related to slower curing and higher porosity, which reduced their compressive strength (17.88 MPa). In addition, the pressed geopolymers showed better thermal stability and fire performance. These results demonstrate that the variation of the forming method has a direct influence on the material properties of geopolymers, and that the pressing process allows for a reduction of the alkaline activator content, thus reducing its environmental footprint. Full article

In this study, alkali-activated mortars were prepared using two different types of fine aggregates: natural sand and biomass bottom ash. These mortars were used as a repair material for structures constructed using old reinforced concrete structures based on Ordinary Portland cement (OPC). Experimental studies have shown that the alkali-activated slag mortar with biomass bottom ash (BBA) from the bubbling fluid bed meets the repair mortar class R1 according to EN 1504-3. The suitability of such repair mortar is determined by the good adhesion properties of the alkali-activated slag binder to old OPC concrete. The adhesion after 28 days was 0.31 MPa and the samples broke off at the repair matrix. The AAC/BBA repair mortar had a compressive strength of 18.69 MPa, the shrinkage due to drying deformations consisted of 0.1903% after 28 days. Alkali-activated slag mortars are effective in repairing, renewing and rebuilding damaged OPC concrete structures. Full article

The expansion of the construction sector has contributed to the depletion of raw materials and an increased demand for resources; therefore, sustainable approaches are required to satisfy the construction demand. The present study explores the development of geopolymers by utilizing industrial by-products from mining, ceramics, olive oil production, and steel manufacturing. Specifically, slate stone cutting sludge (SSCS) and chamotte (CH) are used as aluminosilicate precursors, with olive biomass bottom ash (OSBA) acting as an alkaline activator, along with sodium silicate, and steel granulated slag (SGS) incorporated as an aggregate. Novel geopolymers were prepared with consistent proportions of SSCS and OSBA while varying the CH content from 10 to 2 wt.%. The SGS proportion was adjusted from 35 to 50 wt.%, and different Na₂SiO₃/OSBA ratios (0.35, 0.31, 0.19, and 0.08) were examined. To identify the optimal mix, a series of physical and mechanical tests was conducted, complemented by FTIR and SEM analysis to evaluate the chemical and microstructural changes. The best-performing formulation achieved a compressive strength of 42.8 MPa after 28 days of curing. FTIR analysis identified quartz and carbonate phases, suggesting that quartz did not fully dissolve and that carbonates formed during the heating process. SEM examination of the optimal mixture indicated that the incorporation of SGS (up to 45 wt.%) facilitated the creation of a compact, low-porosity structure. EDX results revealed the presence of Ca-, Na-, Si-, Al-, and K-enriched phases, supporting the formation of (N, C)-A-S-H gel networks. These results demonstrate the potential of utilizing SSCS, CH, OSBA, and SGS to create geopolymer concretes, showcasing the viability of using industrial by-products as eco-friendly substitutes for traditional construction materials. Full article

Aggregates such as sand and gravel are the most mined resources on Earth and are the largest component in concrete. They are essential for construction but are becoming increasingly scarce. At the same time, large amounts of biomass ashes are produced in wood-fired power plants, offering potential as a partial substitute for decreasing sand resources. Due to the combustion technology of circulating fluidized bed boilers, their bottom ash offers high potential as a viable alternative to natural sand. This review examines previous research to assess the feasibility of replacing sand in concrete with bottom ash. Specific cementitious products are identified, where the substitution could realistically be performed in the concrete industry. Benefits and issues with partial substitution of bottom ash from wood combustion are discussed, and gaps in the research regarding sand replacements with bottom ash, notably the durability of the resulting concrete, are shown. Bottom ash has positive properties relevant for use in mortar and concrete, both regarding physical and chemical properties. Although limited research exists in the field, several researchers have demonstrated promising results when substituting sand for bottom ash in mortars. For lower substitution levels, little effect on the fresh and hardened properties is found. Full article

The sustainable development of building materials is based on reusing by-products to reduce environmental impact and promote alternatives to traditional materials. In this study, geopolymers were developed from by-products of the mining, ceramic, and thermal industries: slate stone cutting sludge (SSCS) and chamotte (CH) as aluminosilicate sources, and olive stone bottom ash (OSBA) as an alkaline activator, combined with sodium silicate (Na₂SiO₃). Eight geopolymer families were prepared with constant amounts of SSCS and CH and varying proportions of OSBA/Na₂SiO₃ (0.88–1.31). The evaluation phase included physical, chemical, mechanical, and microstructural tests. The results showed that the optimum geopolymer formulation (GP E) contained 25% SSCS, 15% CH, and 19% OSBA with a Na₂SiO₃/OSBA ratio of 1.0, achieving a compressive strength of 24.12 MPa after 28 days of curing. GP E also showed the lowest porosity (19.54%), minimal water absorption (6.86%), and favorable thermal conductivity (0.688 W/mK). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) confirmed the formation of dense and homogeneous matrices. These results demonstrate the feasibility of manufacturing geopolymers using SSCS, CH, and OSBA as substitutes for traditional binders, promoting sustainable practices, reusing industrial by-products, and reducing carbon emissions in construction. Full article

The reuse of by-products as alternative raw materials to traditional construction materials is required in order to ensure sustainable development in the construction sector and is a significant and important focus in the fields of materials science. This study developed geopolymers using by-products from mining, ceramics, and olive industries, including slate stone cutting sludge (SSCS) and chamotte (CH) as aluminosilicate sources, and olive biomass bottom ash (OSBA) as an alkaline activator with sodium silicate. A key novelty of the research lies in the use of SSCS, an underexplored by-product in geopolymerization studies, as a viable aluminosilicate source. The geopolymers were prepared with varying weight ratios of SSCS, CH, and OSBA/Na₂SiO₃ (1.7, 1.9, 2.2, and 2.4). Physical and mechanical tests determined the optimal formulation, while FTIR and SEM analyses revealed the material’s chemical and structural evolution. The FTIR analysis detected the quartz and carbonate phases, indicating incomplete quartz dissolution and carbonate formation during calcination. The SEM analysis revealed a dense microstructure with reduced porosity and enhanced geopolymerization in samples with higher OSBA content. The optimal geopolymer (60% OSBA, 30% CH, OSBA/Na₂SiO₃ ratio of 2.2) achieved a compressive strength of 33.1 MPa after 28 days. These findings demonstrate the feasibility of producing geopolymers using SSCS, CH, and OSBA, promoting the reuse of industrial by-products as sustainable alternatives to conventional binders. Full article

This study provides a cost-effective method for using bottom ash from biomass combustion, which would otherwise constitute waste, to remove cadmium from acidic industrial wastewater. The X-ray powder diffraction method was used to identify the crystal forms, i.e., the arrangement of atoms in the crystal lattice, and to determine the composition of bottom ash, and the X-ray fluorescence method was used to obtain information on the elemental composition of bottom ash. The Fourier Transform Infrared method was used to analyse and identify the different functional groups occurring in bottom ash. Scanning Electron Microscopy with energy-dispersive X-ray was used to obtain detailed information on the bottom ash surface. The effect of various factors on Cd removal was studied, and optimal experimental conditions were found. The kinetic and thermodynamic equations showed that the removal of Cd²⁺ using bottom ash from biomass combustion was a single-layer chemical adsorption meeting the requirements of pseudo-second-order kinetics. The limiting parameter for the effective adsorption of Cd²⁺ using bottom ash from biomass combustion is its alkaline nature. It can only be used for solutions with pH < 2, which, on the other hand, is its advantage in practical application, namely, in the final treatment of acidic industrial wastewater. Full article

Industrial solid residual waste (ISRW) generated during and/or due to the making of energy, heat, and raw materials poses a major threat to a sustainable future due to its large production quantities and complex characteristics. Especially improper disposal of ISRW (e.g., coal ashes, municipal waste residue, and biomass ashes) not only threatens human health but can also cause environmental hazards such as water, soil, and air pollution, upsetting the global balance. Given the environmental impacts as well as increasingly stringent disposal regulations, lack of landfills, and economic constraints, more sustainable and naturally friendly management strategies are being adopted for ISRW. While numerous studies in the literature have considered various characteristics of ISRW, a complete appraisal of the entire practice, from making to disposal, is still lacking. This paper presents an overview of the making, features, and traditional and innovative managing tactics of ISRW within the context of a general legal framework. This paper provides a scientific review of the various production types, global production quantities, and characteristics of ISRW. Additionally, the orthodox management strategies of ISRWs are scrutinized from a sociological and ecological standpoint, and diverse techniques for more viable and secure management are elucidated. This review culminates in an examination of the global impact and advantages of ISRW management policies based on legislation and regulations. Consequently, this paper seeks to elucidate the extant practices and a few recent advancements pertaining to ISRWs. Additionally, it underscores the ecological, sociological, and economic issues engendered by ISRWs and proposes innovative applications and production technologies. Full article

Biomass bottom ash (BBA) is a by-product of the energy industry and is produced from biomass-fired thermal power plants. They represent the coarsest fraction of the recovered ash and are mostly landfilled. Several researchers have investigated the feasibility of the use of BBA as a replacement for natural aggregates in cementitious material. The utilisation of BBA in the manufacturing of concrete provides an economic and ecological way to upcycle it. At the same time, its use conserves natural resources and promotes sustainability. This review article first presents the chemical, mineralogical and physical properties of BBA, to highlight the possible effects on cementitious materials and the interest in valorising them as a building material. Secondly, the focus is on the utilisation of BBA incorporated in place of natural aggregates used in the manufacturing of concrete. This review investigates the multi-physical properties of concrete manufactured with the partial incorporation of BBA. This substitution leads to decreased workability, which can be limited by the use of admixtures. In the hardened state, a reduction in the mechanical properties is shown with BBA replacement. However, many experimental works show that BBA can be used in appropriate proportions to maintain the specified properties of the concrete. Full article

The development of new building elements, such as concrete and mortar with sustainable materials, which produce a lower carbon footprint, is an achievable milestone in the short term. The need to reduce the environmental impact of the production of cement-based materials is of vital importance. This work focuses on the evaluation of the life-cycle assessment, production costs, mechanical performance, and durability of three mortars and three concrete mixtures in which mixed recycled aggregates (MRAs) and biomass bottom ash from olive waste (oBBA) were included to replace cement and aggregates. Powdered MRA and oBBA were also applied as complementary cementitious materials with a reduced environmental footprint. Chemical and physical tests were performed on the materials, and mechanical performance properties, life-cycle assessment, and life-cycle cost analysis were applied to demonstrate the technical and environmental benefits of using these materials in mortar and concrete mixtures. This research showed that the application of MRA and oBBA produced a small reduction in mechanical strength but a significant benefit in terms of life-cycle population and environmental costs. The results demonstrated that finding long-term mechanical strength decreases between 2.7% and 14% for mortar mixes and between 1.7% and 10.4% for concrete mixes. Although there were small reductions in mechanical performance, the savings in environmental and monetary terms make the feasibility of manufacturing these cement-based materials feasible and interesting for both society and the business world. CO₂ emissions are reduced by 25% for mortar mixes and 12% for concrete mixes with recycled materials, and it is possible to reduce the cost per cubic meter of mortar production by 20%, and the savings in the cost of production of a cubic meter of concrete is 13.8%. Full article

Biodiesel, an eco-friendly alternative to conventional fossil fuels, offers reduced emissions like carbon dioxide, sulfur oxides, and soot. This study explores biodiesel production from a blend of waste oils using a novel biomass-based catalyst derived from the bottom ash of a biomass boiler. Catalyst synthesis involved wet impregnation, a unique approach using previously unreported bottom ash. Characterization via SEM-EDS, BET, FTIR, and XRD revealed its composition and structure. Optimization of biodiesel production involved assessing alcohol molar ratio, catalyst concentration, and reaction time, achieving a maximum FAME concentration of 95% under specific conditions. Blending residual palm oil with waste frying oil enhanced biodiesel properties, demonstrating a maximum FAME concentration at specific catalyst concentration (8%), molar ratio (1:10), and reaction time (2 h). Catalyst reusability, up to three cycles without significant yield variation, showcased its sustainability. The catalyst, primarily composed of calcium, a characteristic biomass bottom ash component, exhibited mesoporous features. Impregnation with eggshells not only altered composition but also ensured a uniform particle size distribution. FTIR and XRD analyses indicated calcium in hydroxide and crystallized forms. Effective catalyst separation methods included decanting or water washing, with optimal biodiesel purity achieved through 3% phosphoric acid washing at 60 °C. Various recovery methods were assessed, highlighting hexane washing as the most efficient, enabling up to three catalyst reuse cycles without substantial efficiency loss. Full article