Search Results (491)

Efficient and clean utilization remains a pivotal development focus within the coal industry. Nevertheless, the application of weakly caking coal results in energy loss due to the caking property, thereby leading to a waste of resources. This paper, therefore, concentrates on the caking property, offering insights into the relevant caking mechanism, evaluation indexes, and regulation technologies associated with it. The caking mechanism delineates the transformation process of coal into coke. During pyrolysis, the active component generates the plastic mass in which gas, liquid, and solid phases coexist. With an increase in temperature, the liquid phase is diminished gradually, causing the inert components to bond. Based on the caking mechanism, evaluation indexes such as that characteristic of char residue, the caking index, and the maximal thickness of the plastic layer are proposed. These indexes are used to distinguish the strength of the caking property. However, they frequently exhibit a poor differentiation ability and high subjectivity. Additionally, some technologies have been demonstrated to regulate the caking property. Technologies such as rapid heating treatment and hydrogenation modification increase the amount of plastic mass generated, thereby improving the caking property. Meanwhile, technologies such as mechanical breaking and pre-oxidation reduce the caking property by destroying agglomerates or consuming plastic mass. Full article

Coffee silverskin (CS), a by-product generated during coffee roasting, contains high levels of xylan hemicellulose and protein, making it a promising substrate for functional ingredient production. This study developed an integrated bioprocess to simultaneously produce bioactive peptides and xylooligosaccharides (CS-XOS) from CS. Conventional alkaline extraction (CAE) under optimized conditions (1.0 M NaOH, 90 °C, 30 min) yielded 80.64 mg of protein per gram of CS and rendered the solid residue suitable for XOS production. Enzymatic hydrolysis of the extracted protein using protease_SE5 generated low-molecular-weight peptides (0.302 ± 0.01 mg/mL), including FLGY, FYDTYY, and FDYGKY. These peptides were non-toxic, exhibited in vitro antioxidant activity (0–50%), and showed ACE-inhibitory activities of 60%, 26%, and 79%, and DPP-IV-inhibitory activities of 19%, 18%, and 0%, respectively. Concurrently, the alkaline-treated CS solid residue (ACSS) was hydrolyzed using recombinant endo-xylanase, yielding 52.5 ± 0.08 mg of CS-XOS per gram of ACSS. The CS-XOS exhibited prebiotic effects by enhancing the growth of probiotic lactic acid bacteria (μ_max 0.100–0.122 h⁻¹), comparable to commercial XOS. This integrated bioprocess eliminates the need for separate processing lines, enhances resource efficiency, and provides a sustainable strategy for valorizing agro-industrial waste. The co-produced peptides and CS-XOS offer significant potential as functional food ingredients and nutraceuticals. Full article

This paper presents a comprehensive review of dealuminated metakaolin (DK), a hazardous industrial by-product generated by the aluminium sulphate (alum) industry and evaluates its potential as a component in cementitious systems for the partial or full replacement of Portland cement (PC). Positioned within the context of waste valorisation in concrete, the review aims to establish a critical understanding of DK formation, properties, and reactivity, particularly its pozzolanic potential, to assess its suitability for use as a supplementary cementitious material (SCM), or as a precursor in alkali-activated cement (AAC) systems for concrete. A systematic methodology is used to extract and synthesise relevant data from existing literature concerning DK and its potential applications in cement and concrete. The collected information is organised into thematic sections exploring key aspects of DK, beginning with its formation from kaolinite ores, followed by studies on its pozzolanic reactivity. Applications of DK are then reviewed, focusing on its integration into SCMs and alkali-activated cement (AAC) systems. The review consolidates existing knowledge related to DK, identifying scientific gaps and practical challenges that limit its broader adoption for cement and concrete applications, and outlines future research directions to provide a solid foundation for future studies. Overall, this review highlights the potential of DK as a low-carbon, circular-economy material and promotes its integration into efforts to enhance the sustainability of construction practices. The findings aim to support researchers’ and industry stakeholders’ strategies to reduce cement clinker content and mitigate the environmental footprint of concrete in a circular-economy context. Full article

The sugarcane industry plays a crucial economic role worldwide, with sucrose and ethanol as its main products. However, its processing generates large volumes of by-products—such as bagasse, molasses, vinasse, and straw—that contain valuable components for biotechnological valorization. This review integrates approximately 100 original research articles published in JCR-indexed journals between 2015 and 2025, of which over 50% focus specifically on sugarcane-derived agroindustrial residues. The biotechnological approaches discussed include submerged fermentation, solid-state fermentation, enzymatic biocatalysis, and anaerobic digestion, highlighting their potential for the production of biofuels, enzymes, and high-value bioproducts. In addition to identifying current advances, this review addresses key technical challenges such as (i) the need for efficient pretreatment to release fermentable sugars from lignocellulosic biomass; (ii) the compositional variability of by-products like vinasse and molasses; (iii) the generation of metabolic inhibitors—such as furfural and hydroxymethylfurfural—during thermochemical processes; and (iv) the high costs related to inputs like hydrolytic enzymes. Special attention is given to detoxification strategies for inhibitory compounds and to the integration of multifunctional processes to improve overall system efficiency. The final section outlines emerging trends (2024–2025) such as the use of CRISPR-engineered microbial consortia, advanced pretreatments, and immobilization systems to enhance the productivity and sustainability of bioprocesses. In conclusion, the valorization of sugarcane by-products through biotechnology not only contributes to waste reduction but also supports circular economy principles and the development of sustainable production models. Full article

The food industry consumes large amounts of water across various processes, and generates wastewater characterized by parameters like biochemical oxygen demand, chemical oxygen demand, pH, suspended solids, and nutrients. To meet environmental standards and enable reuse or valorization, treatment methods such as physicochemical, biological, and membrane-based processes are applied. This review focuses on the valorization of food industry wastewater in the biotechnological production of high-value products, with an emphasis on starch-rich wastewater, wineries and confectionery industry wastewater, and with a focus on new technologies for reduces environmental burden but also supports circular economy principles. Starch-rich wastewaters, particularly those generated by the potato processing industry, offer considerable potential for biotechnological valorization due to their high content of soluble starch, proteins, organic acids, minerals, and lipids. These effluents can be efficiently converted by various fungi (e.g., Aspergillus, Trichoderma) and yeasts (e.g., Rhodotorula, Candida) into value-added products such as lipids for biodiesel, organic acids, microbial proteins, carotenoids, and biofungicides. Similarly, winery wastewaters, characterized by elevated concentrations of sugars and polyphenols, have been successfully utilized as medium for microbial cultivation and product synthesis. Microorganisms belonging to the genera Aspergillus, Trichoderma, Chlorella, Klebsiella, and Xanthomonas have demonstrated the ability to transform these effluents into biofuels, microbial biomass, biopolymers, and proteins, contributing to sustainable bioprocess development. Additionally, wastewater from the confectionery industry, rich in sugars, proteins, and lipids, serves as a favorable fermentation medium for the production of xanthan gum, bioethanol, biopesticides, and bioplastics (e.g., PHA and PHB). Microorganisms of the genera Xanthomonas, Bacillus, Zymomonas, and Cupriavidus are commonly employed in these processes. Although there are still certain regulatory issues, research gaps, and the need for more detailed economic analysis and kinetics of such production, we can conclude that this type of biotechnological production on waste streams has great potential, contributing to environmental sustainability and advancing the principles of the circular economy. Full article

Gasification of municipal solid waste and other biogenic residues (e.g., biomass and biowaste) is increasingly recognized as a promising thermochemical pathway for converting non-recyclable fractions into valuable energy carriers, with applications in electricity generation, district heating, hydrogen production, and synthetic fuels. This paper provides a comprehensive analysis of major gasification technologies, including fixed bed, fluidized bed, entrained flow, plasma, supercritical water, microwave-assisted, high-temperature steam, and rotary kiln systems. Key aspects such as feedstock compatibility, operating parameters, technology readiness level, and integration within circular economy frameworks are critically evaluated. A comparative assessment of incineration and pyrolysis highlights the environmental and energetic advantages of gasification. The valorization pathways for main product (syngas) and by-products (syngas, ash, tar, and biochar) are also explored, emphasizing their reuse in environmental, agricultural, and industrial applications. Despite progress, large-scale adoption in Europe is constrained by economic, legislative, and technical barriers. Future research should prioritize scaling emerging systems, optimizing by-product recovery, and improving integration with carbon capture and circular energy infrastructures. Supported by recent European policy frameworks, gasification is positioned to play a key role in sustainable waste-to-energy strategies, biomass valorization, and the transition to a low-emission economy. Full article

The accelerated industrialization in China has precipitated a dramatic surge in solid waste generation, causing severe land resource depletion and posing substantial environmental contamination risks. Simultaneously, the cement industry has become characterized by the intensive consumption of natural resources and high carbon emissions. This review aims to investigate the current technological advances in utilizing industrial solid waste for cement production, with a focus on promoting resource recycling, phase transformations during hydration, and environmental management. The feasibility of incorporating coal-based solid waste, metallurgical slags, tailings, industrial byproduct gypsum, and municipal solid waste incineration into active mixed material for cement is discussed. This waste is utilized by replacing conventional raw materials or serving as active mixed material due to their content of oxygenated salt minerals and oxide minerals. The results indicate that the formation of hydration products can be increased, the mechanical strength of cement can be improved, and a notable reduction in CO₂ emissions can be achieved through the appropriate selection and proportioning of mineral components in industrial solid waste. Further research is recommended to explore the synergistic effects of multi-waste combinations and to develop economically efficient pretreatment methods, with an emphasis on balancing the strength, durability, and environmental performance of cement. This study provides practical insights into the environmentally friendly and efficient recycling of industrial solid waste and supports the realization of carbon peak and carbon neutrality goals. Full article

The utilization of steel slag (SS), fly ash (FA), and ground granulated blast furnace slag (GGBFS) as soil additives in construction represents a critical approach to achieving resource recycling of these industrial by-products. This study aims to activate the SS-FA-GGBFS composite with a NaOH solution and Na₂CO₃ and employ the activated solid waste blend as an admixture for lateritic clay modification. By varying the concentration of the NaOH solution and the dosage of Na₂CO₃ relative to the SS-FA-GGBFS composite, the effects of these parameters on the activation efficiency of the composite as a lateritic clay additive were investigated. Results indicate that the NaOH solution activates the SS-FA-GGBFS composite more effectively than Na₂CO₃. The NaOH solution significantly promotes the depolymerization of aluminosilicates in the solid waste materials and the generation of Calcium-Silicate-Hydrate and Calcium-Aluminate-Hydrate gels. In contrast, Na₂CO₃ relies on its carbonate ions to react with calcium ions in the materials, forming calcium carbonate precipitates. As a rigid cementing phase, calcium carbonate exhibits a weaker cementing effect on soil compared to Calcium-Silicate-Hydrate and Calcium-Aluminate-Hydrate gels. However, excessive NaOH leads to inefficient dissolution of the solid waste and induces a transformation of hydration products in the modified lateritic clay from Calcium-Silicate-Hydrate and Calcium-Aluminate-Hydrate to Sodium-Silicate-Hydrate and Sodium-Aluminate-Hydrate, which negatively impacts the strength and microstructural compactness of the alkali-activated solid waste composite-modified lateritic clay. Full article

This study evaluated the viability of using the solid residues (bagasse) of the mezcal industry produced with Agave durangensis as a substrate for biogas production, using two chemical pretreatments, acid (HCl) and alkaline (KOH + Ca(OH)₂), to enhance its biodegradability and improve the anaerobic digestion (AD) process. The chemical composition of bagasse was analyzed before and after the chemical pretreatments and then AD experiments were conducted in anaerobic sequential batch reactors (A-SBR) to analyze the effect of pretreatments on biogas production performance. The results showed that acid pretreatment increased cellulose content to 0.606 g, which represented an increase of 34%, and significantly reduced hemicellulose. In contrast, alkaline pretreatment did not show significant changes in cellulose composition, although it caused a swelling of the Agave durangensis mezcal bagasse (Ad-MB) fibers. In terms of biogas production, Ad-MB pretreated with acid (Ad-MB-acid) increased cumulative production by 76% compared to the Agave durangensis mezcal bagasse that was not pretreated (Ad-MB-not pretreated) and by 135% compared to Agave durangensis mezcal bagasse pretreated with an alkaline solution (Ad-MB-alkaline). These results confirmed that Agave durangensis solid waste from the mezcal industry that receives acidic chemical pretreatment has the potential to generate biogas as a sustainable biofuel that can be used to reduce the ecological footprint of this industry. Full article

Municipal solid waste (MSW) and refuse-derived fuel (RDF) incineration generate over 20 million tons of residues annually in the EU. These include bottom ash (IBA), fly ash (FA), and air pollution control residues (APCr), which pose significant environmental challenges due to their leaching potential and hazardous properties. While these residues contain valuable metals and reactive mineral phases suitable for carbonation or alkaline activation, chemical, techno-economic, and policy barriers have hindered the implementation of sustainable, full-scale management solutions. Accelerated carbonation technology (ACT) offers a promising approach to simultaneously sequester CO₂ and enhance residue stability. This review provides a comprehensive assessment of waste incineration residue carbonation, covering 227 documents ranging from laboratory studies to field applications. The analysis examines reactor designs and process layouts, with a detailed classification based on material characteristics, operating conditions, investigated parameters, and the resulting pollutant stabilization, CO₂ uptake, or product performance. In conclusion, carbonation-based approaches must be seamlessly integrated into broader waste management strategies, including metal recovery and material repurposing. Carbonation should be recognized not only as a CO₂ sequestration process, but also as a binding and stabilization strategy. The most critical barrier remains chemical: the persistent leaching of sulfates, chromium(VI), and antimony(V). We highlight what we refer to as the antimony problem, as this element can become mobilized by up to three orders of magnitude in leachate concentrations. The most pressing research gap hindering industrial deployment is the need to design stabilization approaches specifically tailored to critical anionic species, particularly Sb(V), Cr(VI), and SO₄²⁻. Full article

Globally, phosphogypsum (PG) is the primary by-product of the phosphorus industry. Aspergillus niger (A. niger), one of the most powerful types of phosphate-solubilizing fungi (PSF), can secrete organic acids to dissolve the phosphates in PG. This study investigated heavy metal (HM) remediation by PG and A. niger under the co-existence of Pb and Cd. It demonstrated that 1 mmol/L Pb²⁺ stimulated the bioactivity of A. niger during incubation, based on the CO₂ emission rate. PG successfully functioned as P source for the fungus, and promoted the growth of the fungal cells. Meanwhile, it also provided sulfates to immobilize Pb in the solution. The subsequently generated anglesite was confirmed using SEM imaging. The immobilization rate of Pb reached over 95%. Under co-existence, Pb²⁺ and 0.01 mmol/L Cd²⁺ maximized the stimulating effect of A. niger. However, the biotoxicity of Pb²⁺ and elevated Cd²⁺ (0.1 mmol/L) counterbalanced the stimulating effect. Finally, 1 mmol/L Cd²⁺ dramatically reduced the fungal activity. In addition, organic matters from the debris of A. niger could still bind Pb²⁺ and Cd²⁺ according to the significantly lowered water-soluble Pb and Cd concentrations. In all treatments with the addition of Cd²⁺, the relatively high biotoxicity of Cd²⁺ induced A. niger to absorb more Pb²⁺ to minimize the sorption of Cd²⁺ based on the XRD results. The functional group analysis of ATR-IR also confirmed the phenomenon. This pathway maintained the stability of Pb²⁺ immobilization using the fungus and PG. This study, hence, shed light on the application of A. niger and solid waste PG to remediate the pollution of Pb and Cd. Full article

Red mud, a highly alkaline industrial by-product generated during aluminum smelting, poses serious environmental risks such as soil alkalization and ecological degradation. In this study, response surface methodology (RSM) was integrated with advanced microstructural characterization techniques to optimize the performance of red mud–slag composite cementitious materials through multi-factor analysis. By constructing a four-factor interaction model—including red mud content, steel fiber content, alkali activator dosage, and calcination temperature—a systematic mix design and performance prediction framework was established, overcoming the limitations of traditional single-factor experimental approaches. The optimal ratio was determined via multi-factor RSM analysis as follows: the 28-day flexural strength and compressive strength of the specimens reached 12.26 MPa and 69.83 MPa, respectively. Furthermore, XRD and SEM-EDS analyses revealed the synergistic formation of C-S-H and C-A-S-H gels, and their strengthening effects at the fiber–matrix interfacial transition zone (ITZ), elucidating the micro-mechanism pathway of “gel densification–rack filling–strength enhancement.” This work not only enriches the theoretical foundation for the design of red mud-based binders but also offers practical insights and empirical evidence for their engineering applications, highlighting substantial potential in the development of sustainable building materials and high-value utilization of industrial solid waste. Full article

The management of spent foundry sand (SFS) presents environmental and operational challenges for foundries. According to the European Union, European foundries generate approximately 9 million tonnes of SFS annually, mainly from the production of ferrous castings (iron and steel). Nowadays, around 25% of the spent foundry sand in Europe is recycled for specific applications, primarily in the cement industry. However, the presence of chemical residues limits the application of this solution. A possible alternative for reusing the spent foundry sand is its employment as a raw material in the production of compost. Studies in the literature indicate that the amount of chemical residue present in the sand can be reduced through the composting process, making the final product suitable for different purposes. However, information about the implementation of this technology in industrial contexts is lacking. To address this issue, this paper proposes a techno-economic analysis to assess the feasibility of composting SFS on a large scale, using information gathered during the testing phase of the Green Foundry LIFE project. This project explored the reuse of sand from organic and inorganic binder processes to create compost for construction purposes, which allowed for the final product. Since the new BREF (Best Available Techniques Reference Document) introduced by the European Union at the start of 2025 recommends composting SFS as a way to reduce solid waste from foundries, this initial study can represent practical guidance for both researchers and companies evaluating the adoption of this technology. Full article

In the silk production process, cocoons from Bombyx mori worm are degummed and separated from their components. This step generates large residual quantities of an aqueous solution containing various chemical substances, including sericin—a protein that, when discarded improperly, negatively impacts the environment. Sodium bicarbonate and coconut soap are commonly used in the degumming process. The phosphates in the soap and the sodium bicarbonate increase the biological oxygen demand (BOD) and chemical oxygen demand (COD), leading to water contamination. In this study, a Box–Behnken experimental design was used to maximize the extraction of sericin through a conventional extraction under chemical-free conditions. From a total of 45 experiments, the optimal extraction conditions were identified as a solid-to-liquid ratio of 1:20 w/v, a temperature of 120 °C, and 90 min of extraction time. Sericin yields ranged from 9% to 18%. Infrared spectroscopic characterization of the extracted sericin confirmed the presence of protein-specific functional groups and common interactions associated with β-sheet structures. Fractions of high molecular weight (50 kDa to 200 kDa), identified by means of Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) analysis, demonstrate the potential functionality of extracted sericin for the development of biopolymer films useful in biomedical and food industry applications. The optimized methodology is a good alternative to recycle the waste of sericulture chain for obtaining extracts enriched in sericin, as well as to promote the mechanization of artisanal production processes. Full article

Spent coffee grounds are the most abundant waste generated during the preparation of coffee beverages, amounting to 60 million tons per year worldwide. Excessive food waste production has become a global issue, emphasizing the need for waste valorization through the bioprocess of solid-state fermentation (SSF) for high added-value compounds. This work aims to identify the operational conditions for optimizing the solid-state fermentation process of spent coffee grounds to recover bioactive compounds (as polyphenols). An SSF process was performed using two filamentous fungi (Trichoderma harzianum and Rhizopus oryzae). An exploratory design based on the Hunter & Hunter method was applied to analyze the effects of key parameters such as inoculum size (spores/mL), humidity (%), and temperature (°C). Subsequently, a Box–Behnken experimental design was carried out to recovery of total polyphenols. DPPH, ABTS, and FRAP assays evaluated antioxidant activity. The maximum concentration of polyphenols was observed in treatment T3 (0.279 ± 0.002 TPC mg/g SCG) using T. harzianum, and a similar result was obtained with R. oryzae in the same treatment (0.250 ± 0.011 TPC mg/g SCG). In the Box–Behnken design, the most efficient treatment for T. harzianum was T12 (0.511 ± 0.017 TPC mg/g SCG), and for R. oryzae, T9 (0.636 ± 0.003 TPC mg/g SCG). These extracts could have applications in the food industry to improve preservation and functionality. Full article