Search Results (14,845)

The global demand for biodiesel production is steadily increasing. Conventional homogeneous basic catalysts, while widely used in the industry, face significant drawbacks, such as the requirement for high-quality feedstock, excessive waste generation, and multiple purification steps. In this study, an acidic silane (IM-CPTMS-BS-H₂SO₄) containing imidazolium and sulfonic groups was synthesized. Heterogeneous catalysts were then prepared by anchoring varying proportions of the silane onto SBA-15 mesoporous solids. These materials were characterized by FTIR, ¹³C and ²⁹Si NMR, TGA, XRD, CHNS and acidity measurements. The catalysts were evaluated in the transesterification of methyl acetate with ethanol, with increasing catalytic conversions with the amount of grafted IM-CPTMS-BS-H₂SO₄. Furthermore, increasing the catalyst loading (from 2% to 5% wt.) and the reaction temperature (from 50 °C to 65 °C) led to higher methyl acetate conversion rates. Full article

Masonry bricks and blocks are among the most widely used construction materials worldwide; however, their conventional production relies on energy-intensive firing processes and virgin raw materials, leading to significant environmental impacts. In response to increasing sustainability and decarbonization demands in the construction sector, numerous novel ceramic and refractory materials have been proposed for masonry applications. This systematic review provides a comprehensive assessment of recent advances in ceramic and refractory materials for masonry bricks and blocks, focusing on material classification, processing routes, microstructure–property relationships, and sustainability performance. Following the PRISMA 2020 guidelines, the peer-reviewed literature published between 2018 and 2025 was systematically identified, screened, and analyzed. An analytical framework based on well-established relationships from ceramic science was adopted to support consistent comparison of mechanical, thermal, acoustic, durability, and sustainability-related properties across heterogeneous material systems. Conventional fired ceramics, waste-derived ceramics, lightweight and porous systems, alkali-activated and unfired materials, and advanced engineered ceramics were comparatively evaluated. The results reveal a clear shift from dense traditional fired ceramics toward materials incorporating industrial and agricultural residues, engineered porosity, and low-temperature or unfired processing routes. Waste-derived and geopolymer-based systems demonstrate significant potential for reducing CO${}_2$ emissions and energy consumption while maintaining functional performance suitable for masonry applications. Lightweight and porous ceramics exhibit enhanced thermal and acoustic behavior, often accompanied by reduced mechanical strength, highlighting application-dependent trade-offs. Overall, this review provides an integrated perspective linking composition, processing, microstructure, performance, and environmental impact, identifying key research trends and knowledge gaps relevant to sustainable masonry construction. Full article

The circular economy is built on minimizing waste and maximizing the use of resources. The goal is to protect the environment and ensure the supply of limited raw materials in accordance with sustainability. The circular economy enhances natural capital and thus helps to increase the competitiveness of the country. The main objective of the work is to determine whether higher support for research and development affects the development of the circular economy and the associated waste generation. Despite persistent geographical differences in innovation between EU 27 countries in R&D spending, this study demonstrates that high investment does not always equal sectoral efficiency. Using a comparative analysis including R&D expenditure, circular economy investment, and waste generation indicators, the research highlights that specific priorities often outweigh general economic strength. Furthermore, the findings revealed no direct link between agricultural R&D funding and waste generation, suggesting that waste levels are influenced by industry intensity and local legislation rather than the volume of research. Economic sustainability ultimately depends on the efficient conversion of resources into value through policy management and eco-innovation, not just the volume of spending itself. Full article

Mycelium-based composites (MBCs) are gaining attention as sustainable alternatives to conventional materials because they are grown biologically rather than produced through resource-intensive extraction and processing. This study evaluates MBCs for non-load-bearing wall panels and environmentally responsible substitutes for traditional building materials. A reproducible manufacturing process is presented, and heat-pressed panels are characterised for physical, mechanical, and chemical performance. Novelty lies in species-driven evaluation using rice-husk waste as the sole lignocellulosic substrate and a Queensland-native Amauroderma species. Five fungal species, Trametes hirsuta, Ganoderma sp., Amauroderma sp., Pycnoporus coccineus and Trametes versicolor, were cultivated on rice husks and compared under identical processing conditions. Statistical analysis showed species selection significantly influenced tensile strength, whereas flexural and compressive performance showed no significant interspecies differences. Panels achieved tensile, compressive, and flexural strengths up to approximately 0.47, 0.35, and 1.35 MPa, respectively, with Amauroderma exhibiting the highest stiffness and compressive performance. Composites from four of the five species showed low moisture sensitivity and favourable thermal behaviour relative to previously reported mycelium materials. These results demonstrate that fungal species selection is a key design lever and supports rice-husk-derived MBCs as sustainable insulation and non-load-bearing construction materials. Full article

This study examines how 3D-printing orientation affects the mechanical behavior and environmental impact of polymer materials and heterogeneous PLA/TPU composites. Tensile properties of PLA, TPU, and PLA/TPU heterogeneous samples were systematically compared in horizontal and vertical printing orientations. Results show that printing orientation governs mechanical performance: vertical printing generally reduces ductility and exhibits unstable post-peak behavior, with heterogeneous samples performing worse than their single-material counterparts. In contrast, horizontal printing enhances strength, ductility, and energy absorption due to continuous load transfer along the filament path, improved interlayer adhesion, and larger effective contact areas. Specifically, TPU demonstrates higher ductility and energy absorption in the horizontal orientation, while PLA achieves higher strength but lower ductility; both materials degrade substantially in the vertical orientation. For heterogeneous composites, vertical printing yields the poorest outcomes due to load transfer across multiple perpendicular interfaces and thermal shrinkage mismatch, which promote crack initiation and propagation. Horizontal printing delivers an optimal balance of strength and toughness via stronger interface bonding. Life cycle assessment (LCA) indicates that horizontal printing reduces environmental burdens by lowering energy consumption and waste, whereas vertical printing amplifies these impacts, particularly for TPU and composite systems. Based on these findings, we recommend employing horizontally printed PLA/TPU heterogeneous composites to achieve favorable load paths and interface integrity while prioritizing bio-based PLA to enhance sustainability. Full article

Activated carbons are usually prepared from natural precursors (e.g., fruit stones or nutshells) by carbonization and activation processes carried out at 400–1000 °C. They exhibit well-developed porosity, and chemical activation introduces hydrophilic functional groups on their surface, providing excellent sorption properties. However, the high temperatures required during thermal treatment increase production costs. In this work, cost-reducing methods for preparing carbon sorbents are proposed. Carbonization of H₃PO₄ activated waste pistachio nutshells was performed using classical pyrolysis (500 or 550 °C, 30 min, N₂ atmosphere) and microwave treatment (power 1000 W, 20 min). The properties of the synthesized carbons were characterized using thermogravimetry and spectroscopic techniques including infrared (ATR), Raman, photoelectron (XPS) spectroscopies, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). Porous structure parameters were determined using nitrogen adsorption experiments. The efficiency of Pb²⁺ removal from spiked ultrapure, tap and river water was evaluated by batch sorption experiments and inductively coupled plasma–mass spectrometry. The most porous carbons were those prepared at 500 and 550 °C, with specific surface areas of 910 and 256 m²/g, respectively. Surface phosphates increased the Pb²⁺ sorption efficiency to 99% from ultrapure water, at an initial concentration of 300 µg Pb²⁺/L. The material obtained with the microwave method was not fully carbonized and remained nonporous, but it also exhibited 99% Pb²⁺ uptake from ultrapure water due to the presence of oxygen-containing surface groups. The Pb²⁺ removal from spiked tap and river water reached up to 84% and 94%, respectively, at the spiking level of 300 µg Pb²⁺/L. Full article

The energy utilization of residual woody biomass is a relevant strategy for the decentralized energy transition and local waste management in rural areas. The objective of this study was to characterize (physically, chemically, and energetically) five types of residual biomass: pine branches, huinumo (this material refers to the long, thin pine needles that, after drying and falling, form a layer on the forest floor), cherry branches and leaves, and grass waste generated in the community of San Francisco Pichátaro, Michoacán, Mexico, in order to evaluate its viability for the production of densified solid biofuels. A comprehensive analysis was conducted, including moisture content, higher heating value, proximate characterization, structural chemical analysis (using the Van Soest method), elemental CHONS analysis, ash microanalysis (by ICP-OES), and a multicriteria analysis with normalized energy and compositional indicators. The results showed that huinumo and cherry leaves were the most outstanding biomasses, presenting the highest heating values (20.7 MJ/kg) and low moisture and ash contents. Pine branches obtained the most balanced results, characterized by their equilibrium in fixed carbon and lignin, as well as their low potassium content. The multicriteria analysis showed that there is no absolute optimal biomass; however, it indicates that pine branches and huinumo are the most robust feedstocks for the production of briquettes or pellets. The results confirm the significant technical and environmental potential of local lignocellulosic residues for the production of solid biofuels and for contributing to sustainable energy solutions at the local scale. Full article

The recycling of technical textile waste represents a major challenge due to the complex and multilayered structure of these materials. Firefighter protective clothing, mainly composed of high-performance aramid fibers combined with polymeric membranes and auxiliary textile components, is commonly landfilled or incinerated at the end of its service life, resulting in a significant environmental impact. This work utilized recycled aramid-rich textile waste obtained from end-of-life firefighter protective clothing as reinforcement for polyamide 6 to develop high-performance thermoplastic composites within a circular economy framework. Composites containing 15, 30, 45, and 60 wt.% of recycled textile waste were manufactured by melt compounding followed by injection molding. In addition, a selected formulation containing 30 wt.% reinforcement was compatibilized using an amino-functional silane to improve interfacial adhesion. The materials were systematically characterized in terms of tensile properties, thermal behavior, thermomechanical performance, water uptake, flammability, colorimetric properties, and fracture morphology by field emission scanning electron microscopy. The results revealed a pronounced increase in stiffness and thermomechanical stability, with tensile strength increasing from approximately 65 MPa for neat PA6 up to 78 MPa at 30 wt.% reinforcement, and elastic modulus exceeding 5000 MPa at high reinforcement contents. An optimal balance between mechanical performance and ductility was achieved at 30 wt.% reinforcement, while higher contents enabled a substantial extension of the service temperature range, with HDT values increasing from 55 °C for neat PA6 up to 173 °C for highly reinforced systems. FESEM analysis confirmed improved interfacial adhesion in silane-compatibilized systems, explaining the enhanced mechanical and thermomechanical behavior. Furthermore, the incorporation of recycled aramid-rich textile waste led to a significant improvement in flame retardancy, enabling UL-94 V-0 classification at 30 wt.% reinforcement and above, without the use of additional flame-retardant additives, enabling UL-94 V-0 classification without additional flame-retardant additives. Overall, this study demonstrates the technical feasibility and high added-value potential of valorizing firefighter protective clothing waste into advanced PA6-based composites with enhanced mechanical, thermal, and fire-resistant properties, providing a sustainable route for the valorization of high-performance textile waste. Full article

This study presents a source-specific experimental evaluation of particle board waste sludge (PBWS), a sludge-type industrial by-product from the wood-based panel industry, as a partial cement replacement in Portland cement paste systems. The hydration-related behavior of cement pastes containing 0%, 5%, 10%, and 20% PBWS at 7, 28, and 90 days was investigated using Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD), and Thermogravimetry/Derivative Thermogravimetry (TG/DTG). The results showed that PBWS affected phase development and thermal decomposition behavior depending on replacement level and curing age. In the TG/DTG analysis, mass losses in the 30–230 °C region were generally higher in the PBWS-containing mixtures than in the reference paste, particularly at 28 and 90 days, suggesting differences in dehydration-related phase development. FT-IR and XRD results further showed that PBWS modified the evolution of hydration-related phases in the blended systems. From an environmental perspective, increasing PBWS replacement reduced the calculated energy intensity, CO₂ emissions, and production cost; at 20% replacement, these values decreased from 3300 to 2654 MJ/t, from 830 to 706.77 kg/t, and from 3400 to 2867.16 TL/t, respectively. Overall, the results indicate that PBWS has the potential to improve the environmental profile of cement-based production while influencing hydration-related phase evolution in blended paste systems. Full article

This study presents the results of research on the modification of gypsum with bio-waste to improve its thermal insulation properties and to evaluate the influence of the type and amount of the additive on the physical, mechanical, and microstructural properties of the composite. Various fractions of plant-based bio-waste were used in amounts ranging from 0.75 to 10% by weight. The thermal conductivity coefficient and thermal diffusivity were determined. Additionally, analyses of dimensional stability over time, visual appearance, and phase distribution uniformity were conducted. Mechanical tests included surface hardness measurements. In order to determine the material’s durability, water absorption and frost resistance tests were performed, and structural changes and properties after these cycles were analyzed. It was found that selecting the appropriate type and proportion of additive makes it possible to obtain composites with a favorable balance between thermal insulation, dimensional stability, and mechanical performance. The conducted research confirms the potential for effective use of bio-waste as a gypsum-modifying raw material, contributing to the development of sustainable building materials with a reduced environmental footprint and improved functional parameters. Full article

This study investigated whether cooked green beans, a discarded agro-industrial material, can partially replace commercial chicken feed to improve the performance of the edible cricket Gryllus madagascarensis, while accounting for the strong effects of rearing density. A two-by-two factorial experiment was conducted in which crickets were reared at low (500 individuals per box) or high density (2500 individuals per box) and fed either standard chicken feed or the same feed supplemented with cooked green beans, with twenty replicates per treatment. Survival, chicken feed consumption, biomass yield, frass production, efficiency of conversion of ingested feed, and approximate digestibility were measured over the rearing period. Survival increased from 30.0% to 32.9% at low density and from 11.7% to 13.2% at high density, while biomass yield increased from 117.2 g to 129.7 g and from 194.4 g to 231.2 g, respectively. Frass production also increased under supplementation. In contrast, individual body weight was not improved, indicating that higher biomass production resulted mainly from increased survival rather than faster growth. Rearing density remained a major determinant of performance, with low density favoring individual size and survival, and high density maximizing total biomass. Overall, partial replacement of commercial feed with cooked green beans improved survival, biomass yield, and frass production, supporting the use of plant-based wastes to enhance the sustainability of cricket farming. Full article

Biochar (BC) and hydrochar (HC) are carbon-rich materials derived from organic wastes through pyrolysis/gasification and hydrothermal carbonization (HTC), respectively, offering promising pathways for waste valorization and resource recovery within a circular economy framework. Owing to their porous structure and surface functionality, these materials have gained attention as additives in anaerobic digestion (AD), where they may enhance the microbial activity, improve the buffering capacity, and facilitate direct interspecies electron transfer (DIET), resulting in greater process stability and higher methane (CH₄) yields. This study evaluated the effect of BC and HC derived from aloe vera leaves and algae on methane production during the AD of food waste (FW). Batch experiments were conducted under mesophilic conditions (37 °C) for 60 days, using a 1:1 inoculum-to-substrate ratio and a dosage of 10 g L⁻¹ of each carbonaceous material. The results show that adding BC increased cumulative biogas production by 10–14%, while HC led to an 18–35% increase compared with the control. Additionally, dissolved chemical oxygen demand (d-COD) removal improved by up to 30%, and volatile solids (VSs) removal rose by 31% in the FW and aloe HC reactors, highlighting the greater enhancement potential of HCs in methane production. Overall, the findings demonstrate that integrating carbonaceous materials derived from organic residues into AD systems can enhance bioenergy recovery while reducing environmental impacts, supporting more sustainable and circular waste-to-energy processes. Full article

Karst pile foundation cavity treatment requires grouting materials with suitable flowability, stability, strength, and cost-effectiveness, while large quantities of waste mudstone generated by tunnel excavation in Guangxi, China, also require sustainable valorization. In this study, tunnel-excavated mudstone from a tunnel project in Guangxi, China, was used as the primary raw material to develop a solidified grouting material for karst pile foundation cavity treatment. Uniform experimental design, stepwise nonlinear regression, response surface analysis, and multi-objective optimization were employed to evaluate the effects of key mix parameters and determine the optimal formulation. The results showed that the optimal slurry was obtained at a cementitious material-to-mudstone ratio of 0.16, an admixture-to-cementitious material ratio of 0.06, a water-to-solid ratio of 0.63, and the slag powder content-to-cementitious materials ratio of 0.34. In addition, the anti-dispersion performance improved by 87.78%, and compared with conventional cement-soil, C25 concrete, and C30 concrete, the CO₂ emissions were reduced by 37%, 67.4%, and 68.6%, respectively, with the material cost being 73.8% lower than that of traditional cement mortar. These results indicate that the proposed material has promising engineering applicability and demonstrates significant economic and environmental benefits, as well as the valorization potential of tunnel-excavated mudstone. Full article

The management of end-of-life photovoltaic panels has become a focal point for circular economy initiatives, given the significant waste volumes generated by the global energy transition. This study addressed the challenge of identifying optimal recycling solutions characterized by conflicting objectives, such as material recovery efficiency, economic feasibility, and environmental impact. Given that photovoltaic waste contains valuable materials alongside elements requiring specialized handling, the selection of appropriate processing technologies has been prioritized by research and industrial sectors. To resolve these trade-offs, a hybrid Multi-Criteria Decision-Making (MCDM) framework was implemented, combining the Best–Worst Method (BWM) with the Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE II). The BWM was employed to determine criteria weights based on expert evaluations, focusing on the relationships between the most and least significant factors to ensure mathematical consistency. Subsequently, the PROMETHEE II facilitated a complete ranking of technological alternatives by calculating net preference flows, allowing for a nuanced comparative analysis of diverse recovery processes. Through this approach, the research established a clear performance hierarchy among established and emerging recycling pathways. These findings provided a structured quantitative basis for decision-makers to identify balanced solutions for industrial implementation, supporting long-term sustainability goals and the preservation of secondary raw materials. Full article

Biochars derived from post-consumer coffee residues were synthesized using NaCl and NaHCO₃ as impregnation agents, which were pyrolyzed at 500 and 1000 °C. Structural characterization revealed that NaHCO₃ treatment at 1000 °C generated a highly interconnected porous network, with a surface area of 1353.22 m² g⁻¹, pore volume of 0.83 cm³ g⁻¹, and average pore size of 2.6 nm. These features, confirmed by nitrogen physisorption and SEM, favor Na⁺ accessibility and insertion. XRD and Raman analyses indicated a predominantly amorphous carbon, with graphitic domains and an interplanar distance of ≈0.34 nm, providing both adsorption capacity and electrical conductivity. Electrochemical evaluation showed that BC_{NaHCO3-1000°C} achieved an initial capacity of 34 mAh g⁻¹, stable for more than 15 cycles, outperforming NaCl-treated biochars. However, despite the favorable morphology, the high surface area may also promote side reactions and irreversible capacity loss, limiting overall efficiency. These findings demonstrate the feasibility of valorizing coffee waste into carbonaceous materials for sodium-ion battery anodes, while highlighting the need for further optimization of porosity, graphitization, and compositional modifications to enhance energy storage performance. Full article