Search Results (224)

In this study, avocado seed (AS) waste was used as a feedstock for bacterial cellulose (BC) production. Global avocado consumption continues to rise due to its recognised health benefits, resulting in substantial amounts of waste generated by the avocado processing industry. This work proposes the efficient utilisation of avocado seed residues—rich in fermentable sugars—to enhance the economic viability of BC production while supporting responsible agro-industrial waste management. Hydrolysed avocado seeds were incorporated into a modified Hestrin–Schramm (MHS) medium for BC production using Komagataeibacter xylinus as the bacterial strain. The BC membranes obtained from the modified medium (BC-MHS) exhibited higher production (1.93 g/L) and productivity (0.19 g/L·day) compared with those produced in the standard HS medium (BC-HS). The morphology and nanofibre diameter (11–85 nm) of the resulting BC were not significantly affected; however, BC-MHS showed higher crystallinity (~78%) and a higher degradation temperature (~357 °C) than BC-HS. Conversely, the modified medium slightly reduced the mechanical performance of the BC in terms of elongation at break, tensile strength, and Young’s modulus. Overall, avocado seed waste was successfully transformed into a value-added material, demonstrating its potential for agro-industrial waste valorisation through scalable and sustainable biorefinery processes. Full article

Anaerobic digestion (AD) of ensiled orange peel waste (OPW) offers a promising pathway for the valorisation of citrus-processing residues and the generation of renewable energy. This study evaluated the impact of two carbon-based materials, biochar and granular activated carbon (GAC), on methane yield and process stability using Biochemical Methane Potential (BMP) tests. The experimental setup consisted of two consecutive cycles, the second of which was designed to examine microbial acclimation by reusing both the digestate (as the inoculum) and the previously added carbon materials. Ensiled OPW exhibited a methane yield of 578 ± 59 mL_CH4/g_VS during the initial cycle, confirming its high biodegradability. The addition of biochar and GAC resulted in comparable yields (approximately 520–560 mL_CH4/g_VS) and did not enhance the ultimate methane potential; however, both additives proved fully compatible with the process. In the subsequent cycle, a marked increase in methane production was observed, with OPW reaching approximately 730 mL_CH4/g_VS, primarily attributed to improved microbial adaptation. Kinetic analysis revealed moderate enhancements in degradation rates, which were more pronounced when higher biochar dosages were used. Overall, ensiled OPW emerges as a highly suitable substrate for AD. At the same time, biochar and GAC did not adversely affect the AD process under the tested conditions; however, their potential benefits have yet to be fully demonstrated and warrant further investigation, particularly under continuous reactor operating conditions. Full article

Important advancements in the development of novel materials and designs have led to the creation of advanced mineral membranes with high packing densities and enhanced competitiveness in relation to polymeric and classic mineral membranes. Olive juice represents an underutilised source of phenolic and secoiridoid antioxidants, in which industrial valorisation is hindered by some technical limitations, particularly the effective removal of suspended solids during processing. The efficiency of two recrystallized silicon carbide-based microfiltration membranes with an equivalent industrial filtration packing density of 782 m²/m³ was evaluated. One of them had nominal pore sizes of 500 nm and was made of mixed oxides and the other had nominal pore sizes of 200 nm and was made of α-Al₂O₃. The 500 nm membrane demonstrated superior filtration flux and faster processing compared to the 200 nm membrane, though both achieved complete removal of suspended solids. A greater workload of the 500 nm membrane resulted in a progressive irreversible fouling, caused by the smallest-sized suspended particles and macromolecular colloids. Particle size had a greater impact on fouling than particle load. Both membrane treatments induced a spontaneous increase in the concentrations of up to 24 phenolic, secoiridoid and secoiridoidyl phenylethanoid conjugates. This effect can be considered as an additional benefit of the thus clarified olive juices. Further investigations are warranted to elucidate the underlying mechanisms driving these transformations. Full article

The urgent need to reduce greenhouse gas emissions and enhance resource circularity is driving the cement and construction industry to explore alternatives to clinker-based binders. Electric arc furnace slag (EAFS), a major steelmaking by-product, is currently underutilised as a binder due to its low intrinsic reactivity. This study provides a comparative evaluation of three distinct valorisation pathways for the same EAFS—use as a supplementary cementitious material (SCM), as a precursor for alkali-activated binders, and as a component in accelerated carbonation systems—thereby highlighting its multifunctional and more ecological binding potential. A comprehensive physicochemical characterisation was conducted, followed by mechanical performance assessment under different curing regimes. When used as an SCM, partial cement replacement resulted in no loss of mechanical performance and a compressive strength increase of up to 8.9% at 10% replacement, demonstrating its suitability for structural applications. Under accelerated carbonation, specimens with 50% replacement of cement and sand achieved compressive strengths of 46.7 MPa, comparable to the non-carbonated reference (47 MPa), indicating full strength recovery despite high substitution levels. Full replacement systems based on alkali activation or carbonation of EAFS achieved moderate compressive strengths (~10 MPa), suitable for non-structural applications, with clear potential for improvement through optimisation of activation and curing conditions. Overall, this work demonstrates that EAFS can be effectively valorised through multiple reaction routes, supporting its role as a versatile and low-carbon resource for sustainable cementitious materials. Full article

The food industry generates large volumes of nutrient-rich by-products that remain underutilised despite their considerable biochemical potential. These materials originate predominantly from the fruit and vegetable, dairy, meat, and fish and seafood sectors and represent a substantial opportunity for sustainable valorisation. Fermentation has emerged as a powerful platform for converting such by-products into high-value ingredients, including bioactive compounds, functional metabolites, enzymes, antimicrobials, and nutritionally enriched fractions. This review synthesises recent advances in microbial fermentation strategies—spanning lactic acid bacteria, filamentous fungi, yeasts, and mixed microbial consortia—and highlights their capacity to enhance the bioavailability, stability, and functionality of recovered compounds across diverse substrate streams. Key technological enablers, including substrate pre-treatments, precision fermentation, omics-guided strain selection and improvement, and bioprocess optimisation, are examined within the broader framework of circular bioeconomy integration. Despite significant scientific progress, major challenges remain, particularly related to substrate heterogeneity, process scalability, regulatory alignment, safety assessment, and consumer acceptance. The review identifies critical research gaps and future directions, emphasising the need for standardised analytical frameworks, harmonised compositional databases, AI-driven fermentation control, integrated biorefinery concepts, and pilot-scale validation. Overall, the evidence indicates that integrated fermentation-based approaches—especially those combining complementary by-product streams, tailored microbial consortia, and system-level process integration—represent the most promising pathway toward the scalable, sustainable, and economically viable valorisation of food industry by-products. Full article

This study investigates a sustainable and efficient approach to valorising barley straw by producing nanocellulose via an integrated subcritical alkaline hydrolysis and HDES-assisted processing pathway. Subcritical alkaline pretreatment under best processing conditions (150 bar, 200 °C, 125 min) enabled effective biomass fractionation, achieving average hemicellulose and lignin solubilisation of 57.72% and 82.69%, respectively. Subsequent purification of the pretreated solid fraction yielded cellulose fibres with an average cellulose yield of 41.97% and a purity of 87.87%. Nanocellulose was then obtained using a sequential HDES treatment followed by high-intensity ultrasound (HIUS), producing a sample (NC-BTW-3) in which 66% of particles exhibited diameters below 100 nm, 15.2% were between 100 and 200 nm, and 19% were within the 200–1000 nm range. The resulting nanocellulose demonstrated good colloidal stability, with an average zeta potential of −33.0 mV. Overall, the work highlights a green and effective processing strategy for the valorisation of agricultural residues into high-value nanocellulose suitable for bio-based material applications. Full article

The study comprises an in-depth characterization of compositional groups of the liquid by-products obtained from the pyrolysis of swine manure at 500 °C, with the aim of providing an alternative and efficient approach for the valorisation of this waste stream, alongside with the production of biogas and char, the latter of which can be further converted into activated carbon. Two samples were considered: de-watered cake and solid product from anaerobic digestion of swine manure. Biocrude oils were fractionated into weak acidic, strong acidic, alkaline and neutral oil fractions. Subsequently, the neutral oil fraction was separated into paraffinic–naphthenic, slightly polar and polar fractions. All fractions were analyzed by GC–MS. The major identified compositional groups were: (i) for de-watered cake: steroids (40.7%), fatty acids, FAs (23.7%) and n-alkenes/n-alkanes (23.3%); (ii) for solid product from anaerobic digestion: FAs (31.0%), phenols/methoxy phenols (26.6%), n-alkenes/n-alkanes (10.8%) and steroids (10.6%). A variety of short-chain FAs (i.e., linear saturated, mono- and di-unsaturated, cis (i-), trans (ai-), isoprenoid, phenyl alkanoic, amongst others) and methyl esters (FAMEs) were identified as well. FA distribution, nC₁₂–nC₂₀, was similar for both manures studied with nC₁₆ and nC₁₈ as major compounds. FAMEs (nC₁₄–nC₂₈, with even carbon number dominance) in the slightly polar fraction of both samples were accompanied by considerable amounts of oleic (nC_18:1) and linoleic (nC_18:2) acids, and corresponding methyl esters. Hydrocarbons, i.e., n-alkenes/n-alkanes, were in the range of nC₁₅–nC₃₄, with nC₁₈ maximizing. Anaerobically digested manure has resulted in (i) an increase in the portion of longer homologues of hydrocarbons and FAMEs and (ii) the appearance of new FAs series of long chain members nC_22:1–nC_26:1, ω-9. The comprehensive analysis of the biocrude oils obtained from the slow pyrolysis of swine manure indicates their potential for use as biodiesel additives or as feedstock to produce value-added materials. Full article

Sheep wool is a low-value agricultural by-product with potential to contribute to more sustainable cementitious materials. This study investigates Segureña sheep wool fibres as reinforcement in cement mortars, comparing washed wool (W) and cement-encapsulated wool (E) at the same oven-dry raw wool dosages (0.5, 1.0, and 3.0 g per batch), and benchmarking against polypropylene (PP) fibres. Flexural and compressive strength were evaluated at 1, 7, and 28 days, whereas apparent density, water absorption, and thermal conductivity were assessed at 28 days. An intermediate dosage (1.0 g per batch) provided the most favourable mechanical response, while the highest dosage (3.0 g per batch) reduced performance, plausibly due to dispersion limitations and void formation. At 28 days, W-1 reached 9.65 ± 0.50 MPa in flexure (very close to PP-1) and 59.70 ± 1.05 MPa in compression, exceeding PP-1 in compression. Wool incorporation also reduced apparent density and yielded an observed reduction in thermal conductivity of up to ~18% at the highest dosage (single specimen per series). Overall, optimally dosed washed wool can deliver competitive mechanical performance while improving thermal behaviour, supporting circular-economy valorisation of waste wool in eco-mortars. Full article

This study investigates the valorisation of mixed municipal waste glass (MMWG; EWC 20 01 02) as a sustainable supplementary material in cement mortars. In contrast to most existing studies, which focus almost exclusively on homogeneous container glass, this work addresses a heterogeneous waste stream derived from municipal selective collection, containing flat glass, mirrors, ceramics, porcelain, and metallic residues. Such mixed household glass has not previously been systematically evaluated in cement mortars, thereby addressing a clear research gap. The MMWG was washed, dried, and ground in a Los Angeles drum with corundum abrasives to obtain a fine glass powder (FGP < 63 µm) with a median particle size of approximately 20 µm and a Blaine fineness of 360 m²/kg. Microstructural and chemical characterisation of the milled glass confirmed its highly amorphous nature and angular particle morphology resulting from grinding. In addition, coarse glass granules (0–4 mm) were used as partial replacements for natural sand in mortar mixtures. The incorporation of FGP led to a 4–12% reduction in flowability, attributable to the angular shape and increased specific surface area of the ground-glass particles. At 28 days, mortars containing 5–10% FGP exhibited mechanical properties comparable to the reference mix, while at 56 days their compressive strength increased by up to 8%, indicating delayed pozzolanic activity typical of finely milled, amorphous glass. Mortars containing coarse glass primarily reflected a filler and aggregate-replacement effect. Leaching tests conducted in accordance with PN-EN 12457-4 demonstrated that all mortars, both reference and MMWG-modified, complied with the non-hazardous waste limits defined in Council Decision 2003/33/EC. Minor exceedances of Ba and Cr relative to inert-waste thresholds were observed; however, these values remained within the permissible range for non-hazardous classification and were attributed to ceramic and metallic contaminants inherently present in the mixed glass fraction. Overall, this study demonstrates that mixed municipal waste glass—a widely available yet rarely valorised heterogeneous waste stream—can be effectively utilised as a finely ground supplementary material and as a partial aggregate replacement in cement mortars, provided that particle fineness is adequately controlled and durability-related effects are monitored. The findings extend the applicability of glass waste beyond container cullet and support the development of circular-economy solutions in construction materials. Full article

This study focuses on preparing mullite grogs derived from selected waste materials and kaolin treated with advanced technologies to achieve high thermal resistance and low thermal expansion. The investigated waste materials include dust removal RON, slurry DE, feldspar dust removal from Halamky, and waste generated during the feldspar grinding at the Halamky I deposit. These materials (Red kaolin from Vidnava, Slurry DE, Dust-off RON, Feldspar dust-off Halamky) were processed into grogs and subsequently applied for the production of high-mullite ceramics. The influence of cristobalite admixture was also assessed. The chemical composition was determined by X-ray fluorescence (XRF), while the phase composition was analysed by X-ray diffraction (XRD). Amorphous mullite grogs with mullite contents greater than 40% were successfully prepared. Despite the relatively high iron content, the resulting products exhibited the desired white colour after firing and demonstrated properties that make them promising candidates for advanced refractory applications. The study highlights the potential to valorise industrial waste materials for high-value ceramic applications. Full article

Waste valorisation has become a key strategy for applying circular economy principles in the agro-industrial field. This study investigated the territorial implementation of the waste composting on a territorial scale. The wastes considered were the post-processing orange waste, spent olive oil pomace, and spent wine grape pomace. Their potential use as soil amendments across the provinces of Sicily was assessed through a GIS-based analysis, taking into account nitrogen (N) application constraints. Moreover, a cascade valorisation scheme was also evaluated: post-processing orange waste was first used as animal feed, and the remaining fraction was directed to composting; olive pomace was first sent to pomace oil extraction mills, and the residual material was subsequently used for composting. Results indicate that N inputs derived from composted residues remain below legal thresholds in all provinces, with relative contributions ranging from 38% to 92% of the regulatory limits. Spatial variability in nitrogen availability reflects the territorial distribution of agro-industrial activities, highlighting the importance of localised management strategies. These findings demonstrate that composting, combined with cascade valorisation, is an effective pathway to close nutrient cycles, reduce waste generation, and support sustainable biomass management in regional agri-food systems. Full article

This study assessed the production and characterisation of biochars derived from the pyrolysis and co-pyrolysis of urban biosolids (BSs) combined with two lignocellulosic biomasses: rice husk (RH) and pruning waste (PW). The treatments were conducted at 300, 400, and 500 °C to evaluate the influence of temperature and mass ratio on the physicochemical, structural, and biological properties of the material. Co-pyrolysis significantly improved the material’s properties, enhancing carbon content, surface area, porosity, and pH, while reducing ash and heavy metal concentrations. RH promoted greater porosity and alkalinity, whereas PW increased carbon content and improved maize germination. Biochars produced at 400–500 °C met the stability criterion (H/C < 0.7) set by the International Biochar Initiative (IBI) and the European Biochar Certificate (EBC). However, zinc (Zn) remained the most limiting element for certification. Overall, the findings demonstrate that the co-pyrolysis of BSs with agroforestry biomasses is an effective and sustainable strategy for generating stable and environmentally safe biochars, suitable for use as soil amendments and for the sustainable valorisation of BSs. Full article

The construction sector faces pressure to decarbonise while addressing rising resource demands and agricultural waste. Ordinary Portland cement (OPC) is a major CO₂ emitter, yet biomass residues are often open-burned or landfilled. This study explores corncob ash (CCA) as a sustainable supplementary cementitious material (SCM), examining how calcination conditions influence pozzolanic potential and support circular economy and climate goals, which have not been adequately explored in literature. Ten CCA samples were produced via open-air burning (2–3.5 h) and electric-furnace calcination (400–1000 °C, 2 h), alongside a reference OPC. Mass yield, colour, XRD, XRF, LOI, and LOD were analysed within a process–structure–property–performance–sustainability framework. CCA produced in a 400–700 °C furnace window consistently achieved high amorphous contents (typically ≥80%) and combined pozzolanic oxides (SiO₂ + Al₂O₃ + Fe₂O₃) above the 70% ASTM C618 threshold, with 700 °C for 2 h emerging as an optimal condition. At 1000 °C, extensive crystallisation reduced the expected reactivity despite high total silica. Extended open-air burning (3–3.5 h) yielded chemically acceptable but more variable ashes, with lower amorphous content and higher alkalis than furnace-processed CCA. Simple industrial ecology calculations indicate that valorising a fraction of global CC residues and deploying optimally processed CCA at only 20% OPC replacement could displace 180 million tonnes CC waste and clinker avoidance on the order of 5–6 Mt CO₂ per year, while reducing uncontrolled residue burning and primary raw material extraction. The study provides an experimentally validated calcination window and quality indicators for producing reactive CCA, alongside a clear link from laboratory processing to clinker substitution, circular resource use, and alignment with SDGs 9, 12, and 13. The findings establish a materials science foundation for standardised CCA production protocols and future life cycle and performance evaluations of low-carbon CCA binders. Full article

The re-valorisation of oyster-shell waste offers a sustainable pathway for producing eco-efficient construction materials. This study investigates the physical, mechanical, and durability performance of natural hydraulic lime (NHL) mortars incorporating oyster shells (OSs), applied to solid bricks representative of historical masonry. Two formulations were developed: one with 24% replacement of NHL by oyster-shell powder (OSP, <150 µm) and another with 30% substitution of sand by oyster-shell aggregate (OSA, 0–4 mm), both compared with a control mortar. Mortars were tested in standard molds and directly applied to bricks, including under accelerated aging conditions (temperature and humidity cycles). Results revealed that shell-incorporated mortars applied to bricks exhibited higher bulk density and compressive strength, and lower porosity, capillary water absorption, and water vapor permeability, compared with mold-cast samples. The performance for the shell-based mortars highlights the substrate–mortar interaction, consistent with the behavior of traditional lime-based systems, and the microscope characterization (poro-Hg and X-ray tomography). Shell-incorporated mortars retained stable properties after aging, with variations below 10% compared to unaged mortars. These findings demonstrate the feasibility of oyster shells as partial replacements for lime and sand, confirming its potential as an eco-efficient strategy for sustainable mortars in conserving and rehabilitating historic masonry buildings. Full article

The global production of electronic waste (e-waste) has increased due to the quick turnover of electronic devices, creating urgent problems for resource management and environmental sustainability. As a result, e-waste-derived materials (EWDMs) are being explored in pavement engineering research as sustainable substitutes in line with Sustainable Development Goals (SDGs), specifically SDG 9 (Industry, Innovation, and Infrastructure), 11 (Sustainable Cities and Communities), 12 (Responsible Consumption and Production), and 13 (Climate Action). Therefore, to assess global research production and the effectiveness of EWDMs in asphalt applications, this review combines scientometric mapping and systematic evidence synthesis. A total of 276 relevant publications were identified via a thorough search of Web of Science, Scopus, and ScienceDirect (2010–2025). These were examined via coauthorship structures, keyword networks, and contributions at the national level. The review revealed that China, India, and the United States are prominent research hubs. Additionally, experimental studies have shown that EWDMs, such as printed circuit board powder, fluorescent lamp waste glass, high-impact polystyrene, and acrylonitrile–butadiene–styrene, improve the fatigue life, Marshall stability, rutting resistance (up to 35%), and stiffness (up to 28%). However, issues with long-term field durability, microplastic release, heavy metal leaching, and chemical compatibility still exist. These restrictions highlight the necessity for standardised toxicity testing, harmonised mixed-design frameworks, and performance standards unique to EWDMs. Overall, the review shows that e-waste valorisation can lower carbon emissions, landfill build-up, and virgin material extraction, highlighting its potential in the circular pavement industry and promoting sustainable paving practices in accordance with SDGs 9, 11, 12, and 13. This review suggests that further studies on large-scale field trials, life cycles, and technoeconomic assessments are needed to guarantee the safe, long-lasting integration of EWDMs in pavements. It also advocates for coordinated research, supportive policies, and standardised methods. Full article