Search Results (438)

Anaerobic digestion (AD) is increasingly recognized as a key technology for renewable energy generation and sustainable waste management within the circular economy. However, its performance is highly sensitive to feedstock variability and environmental fluctuations, making stable operation and high methane yields difficult to sustain. Conventional monitoring and control systems, based on limited sensors and mechanistic models, often fail to anticipate disturbances or optimize process performance. This review discusses recent progress in electrochemical, optical, spectroscopic, microbial, and hybrid sensors, highlighting their advantages and limitations in artificial intelligence (AI)-assisted monitoring. The role of soft sensors, data preprocessing, feature engineering, and explainable AI is emphasized to enable predictive and adaptive process control. Various machine learning (ML) techniques, including neural networks, support vector machines, ensemble methods, and hybrid gray-box models, are evaluated for yield forecasting, anomaly detection, and operational optimization. Persistent challenges include sensor fouling, calibration drift, and the lack of standardized open datasets. Emerging strategies such as digital twins, data augmentation, and automated optimization frameworks are proposed to address these issues. Future progress will rely on more robust sensors, shared datasets, and interpretable AI tools to achieve predictive, transparent, and efficient biogas production supporting the energy transition. Full article

This review comprehensively examines the advancements and challenges in anaerobic digestion (AD) for biogas production, emphasising technological, microbial, and policy perspectives. It highlights the AD significant potential for valorising diverse organic substrates, including manure, food waste, and microalgae, thereby contributing to renewable energy generation and greenhouse gas mitigation. Key operational factors influencing biogas yield include substrate composition, temperature (preferably mesophilic conditions), pH (6.5–7.5), and the substrate-to-inoculum ratio (SIR), all of which significantly affect microbial activity and process stability. Co-digestion strategies and pretreatments are examined for their roles in enhancing biodegradability and methane yield, respectively. Microbial community dynamics, particularly responses to feedstock heterogeneity and operational parameters, are integral to process optimisation. Advances in metagenomics have provided insights into microbial resilience and adaptation to conditions such as high ammonium levels. This review also discusses various modelling approaches, including kinetic models and machine learning techniques, for predicting and optimising biogas production. Additionally, policy frameworks within regions such as the European Union and Brazil, along with economic incentives and regulatory hurdles, are also considered crucial for scaling up deployment. Challenges such as digestate management and high capital costs persist, underscoring the need for integrated strategies to enhance the sustainability and viability of AD-based biogas projects. Full article

Recycling water treatment sludge (WTS) offers a sustainable solution to reduce environmental waste and enhance soil stabilisation in geotechnical applications. This study investigates the mechanical performance of soil-sludge-cement-lime mixtures through an extensive experimental program and focuses on compaction characteristics and California Bearing Ratio (CBR) values. Mixtures containing 40% soil, 50% sludge, and 10% lime achieved a CBR value of 58.7% and represented a 550% increase compared to untreated soil. Additionally, advanced predictive modelling using symbolic metaheuristic-based genetic programming (GP) techniques, including the Dingo Optimisation Algorithm (DOA), Osprey Optimisation Algorithm (OOA), and Rime-Ice Optimisation Algorithm (RIME), demonstrated exceptional accuracy in predicting CBR values. The GP-RIME model achieved an R² of 0.991 and a mean absolute error (MAE) of 1.02 in predicting CBR values, significantly outperforming traditional regression methods. Four formulas are proposed to predict CBR values. This research highlights the dual benefits of sustainable WTS recycling and advanced modelling techniques, providing scalable solutions for environmentally friendly infrastructure development. This research aligns with global sustainability goals by valorising waste streams from water treatment plants. The reuse of sludge not only reduces landfill disposal but also lowers demand for energy-intensive binders, contributing to circular economy practice and sustainable infrastructure development. Full article

The growing global demand for clean energy and sustainability has increased interest in lignocellulosic biomass as a viable alternative to conventional fossil fuels. Among the various biomass resources, sugarcane bagasse, an abundant agro-industrial by-product, has emerged as a promising feedstock to produce renewable fuels and value-added chemicals. Its high carbohydrate content offers significant potential for bioconversion. However, its complex and recalcitrant lignocellulosic matrix presents significant challenges that necessitate advanced pretreatment techniques to improve enzymatic digestibility and fermentation efficiency. This review consolidates recent developments in the valorization of sugarcane bagasse focusing on innovative pretreatment and fermentation strategies for sustainable bioethanol production. It emphasizes the synergistic benefits of integrating various pretreatment and fermentation methods to improve bioethanol yields, reduce processing costs and enhance overall process sustainability. This review further explores recent technological advancements, the impact of fermentation inhibitor, and emerging strategies to overcome these challenges through microbial strains and innovative fermentation methods. Additionally, it highlights the multi-faceted advantages of bagasse valorization, including waste minimization, renewable energy production and the promotion of sustainable agricultural practices. By evaluating the current state of research and outlining future perspectives, this paper serves as a comprehensive guide to advancing the valorization of sugarcane bagasse in the transition towards a low-carbon economy. The novelty of this review lies in its holistic integration of technological, economic, and policy perspectives, uniquely addressing the scalability of integrated pretreatment and fermentation processes for sugarcane bagasse, and outlining practical pathways for their translation from laboratory to sustainable industrial biorefineries within the circular bioeconomy framework. Full article

The fashion and textile industry (FTI) is a significant contributor to greenhouse gas emissions, resource consumption, and waste generation, necessitating sustainable alternatives. Chitosan, a biodegradable and renewable biopolymer, has shown potential in reducing environmental impact throughout the textile lifecycle. However, existing studies often focus on isolated applications rather than its broader role in industrial sustainability. This review synthesises findings from 142 academic studies to assess chitosan’s applications in textile production, dyeing, finishing, and waste management, emphasising its impact on energy efficiency, carbon reduction, and resource circularity. Chitosan’s biodegradability, antimicrobial properties, and affinity for sustainable dyeing offer a viable alternative to synthetic materials while also enhancing wastewater treatment and eco-friendly finishing techniques. By evaluating its contributions to sustainable manufacturing, this review highlights its potential in supporting decarbonisation and circular economy transitions within the textile sector, while also identifying challenges for future research. Full article

Seawater desalination has emerged as a crucial solution for addressing global freshwater scarcity. However, it generates significant volumes of concentrated brine waste. This brine is rich in dissolved salts and minerals, primarily, chloride (55%), sodium (30%), sulfate (8%), magnesium (4%), calcium (1%), potassium (1%), bicarbonate (0.4%), and bromide (0.2%), which are often discharged into marine environments, posing ecological challenges. This study presents a comprehensive global review of innovative technologies for recovering these constituents as valuable products, thereby enhancing the sustainability and economic viability of desalination. The paper evaluates a range of proven and emerging recovery methods, including membrane separation, nanofiltration, electrodialysis, thermal crystallization, solar evaporation, chemical precipitation, and electrochemical extraction. Each technique is analyzed for its effectiveness in isolating salts (NaCl, KCl, and CaSO₄) and minerals (Mg(OH)₂ and Br₂), with a discussion of process-specific constraints, recovery efficiencies, and product purities. Furthermore, the study incorporates a detailed techno-economic assessment, highlighting revenue potential, capital and operational expenditures, and breakeven timelines. Simulated case studies of a 100,000 m³/day seawater reverse osmosis (SWRO) facility demonstrates that a sequential brine recovery process and associated energy balances, supported by pilot-scale data from ongoing global initiatives, can achieve over 90% total salt recovery while producing marketable products such as NaCl, Mg(OH)₂, and Br₂. The estimated revenue from recovered materials ranges between USD 4.5 and 6.8 million per year, offsetting 65–90% of annual desalination operating costs. The analysis indicates a payback period of 3–5 years, depending on recovery efficiency and product pricing, underscoring the economic viability of large-scale brine valorization alongside its environmental benefits. By transforming waste brine into a source of commercial commodities, desalination facilities can move toward circular economy models and achieve greater sustainability. A practical integration framework is proposed for both new and existing SWRO plants, with a focus on aligning with the principles of a circular economy. By transforming waste brine into a resource stream for commercial products, desalination facilities can reduce environmental discharge and generate additional revenue. The study concludes with actionable recommendations and insights to guide policymakers, engineers, and investors in advancing brine mining toward full-scale implementation. Full article

This review examines the current status and future potential of plasma-induced acidification (PIA) as a sustainable method for managing nitrogen-rich organic waste streams such as livestock slurry and digestate. Conventional acidification using sulfuric or nitric acid reduces ammonia (NH₃) emissions but raises concerns related to safety, cost, and environmental impacts. Plasma-assisted systems offer an alternative by generating reactive nitrogen and oxygen species (RNS/ROS) in situ, lowering pH and stabilizing ammonia (NH₃), as ammonium (NH₄⁺), thereby enhancing fertiliser value and reducing emissions of NH₃, methane (CH₄), and odours. Key technologies such as dielectric barrier discharge (DBD), corona discharge, and gliding arc reactors show promise in laboratory-scale studies, but barriers like energy consumption, scalability, and N₂O trade-offs limit commercial adoption. The paper reviews the mechanisms behind PIA, compares it to conventional approaches, and assesses its agronomic and environmental benefits. Valorisation opportunities, including the recovery of nitrate-rich fractions and integration with biogas systems, align plasma treatment with circular economy goals. However, challenges remain, including reactor design, energy efficiency, and lack of recognition as a Best Available Technique (BAT). A roadmap is proposed for transitioning from lab to farm-scale application, involving cross-sector collaboration, lifecycle assessments, and policy support to accelerate adoption and realise environmental and economic gains. Full article

Thorium has emerged as a promising alternative to uranium in nuclear energy systems due to its higher natural abundance, favorable conversion to fissile ²³³U, and reduced generation of long-lived transuranic waste. This review provides a comprehensive overview of advanced techniques for thorium recovery from primary ores and secondary resources. The main mineralogical carriers—including monazite, thorianite, thorite, and cheralite as well as industrial by-products such as rare-earth processing tailings—are critically examined with respect to their occurrence and processing potential. Physical enrichment methods (gravity, magnetic, and electrostatic separation) and hydrometallurgical approaches (acidic and alkaline leaching) are analyzed in detail, highlighting their efficiencies, limitations, and environmental implications. Particular emphasis is placed on modern separation strategies such as solvent extraction with organophosphorus reagents, diglycolamides, and ionic liquids, as well as extraction chromatography, nanocomposite sorbents, ion-imprinted polymers, and electrosorption on carbon-based electrodes. These techniques demonstrate significant progress in enhancing selectivity, reducing reagent consumption, and enabling recovery from low-grade and secondary feedstocks. Environmental and radiological aspects, including waste minimization, immobilization, and regulatory frameworks, are discussed as integral components of sustainable thorium management. Finally, perspectives on hybrid technologies, digital process optimization, and economic feasibility are outlined, underscoring the need for interdisciplinary approaches that combine chemistry, materials science, and environmental engineering. Collectively, the analysis highlights the transition from conventional practices to integrated, scalable, and environmentally responsible technologies for thorium recovery. Full article

Bio-waste from potato shell agro-waste-based photocatalyst is introduced using potato shell integrated with Fe₃O₄ nanoparticles as a novel photocatalyst for photo-Fenton oxidation reaction. The catalyst was prepared via thermal activation of biochar, followed by co-precipitation of magnetite nanoparticles, resulting in a stable and reusable material. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques augmented with the energy dispersive X-ray spectroscopy (EDX) analysis with elemental mapping were used to assess the prepared sample. The prepared material, PtS200–Fe₃O₄, is then applied for oxidizing Procion Blue dye using biochar-supported magnetite catalyst. The oxidation process was evaluated under varying operational parameters, including pH, temperature, catalyst loading, oxidant dosage, and dye concentration. Results revealed that the system achieved complete dye removal within 20 min at 60 °C and pH 3, demonstrating the strong catalytic activity of the composite. Furthermore, the kinetic modeling is evaluated and the data confirmed that the degradation followed first-order kinetics. Also, the thermodynamic parameters indicated low activation energy with PtS200–Fe₃O₄ composite in advanced oxidation processes. The system sustainability is also assessed, and the reusability test verified that the catalyst retained over 70% efficiency after six consecutive cycles, highlighting its durability. The study confirms the feasibility of using biochar-supported magnetite as a cost-effective, eco-friendly, and efficient catalyst for the treatment of textile effluents and other dye-contaminated wastewater. Full article

Biofuels represent a sustainable alternative that supports global energy development without compromising environmental balance. This work introduces a novel hardware–software platform for the experimental characterization of biomass solid yield during the slow pyrolysis process, integrating physical experimentation with advanced computational modeling. The hardware consists of a custom-designed pyrolizer equipped with temperature and weight sensors, a dedicated control unit, and a user-friendly interface. On the software side, a two-step kinetic model was implemented and coupled with three optimization algorithms, i.e., Particle Swarm Optimization (PSO), Genetic Algorithm (GA), and Nelder–Mead (N-M), to estimate the Arrhenius kinetic parameters governing biomass degradation. Slow pyrolysis experiments were performed on wheat straw (WS), pruning waste (PW), and biosolids (BS) at a heating rate of 20 °C/min within 250–500 °C, with a 120 min residence time favoring biochar production. The comparative analysis shows that the N-M method achieved the highest accuracy (100% fit in estimating solid yield), with a convergence time of 4.282 min, while GA converged faster (1.675 min), with a fit of 99.972%, and PSO had the slowest convergence time at 6.409 min and a fit of 99.943%. These results highlight both the versatility of the system and the potential of optimization techniques to provide accurate predictive models of biomass decomposition as a function of time and temperature. Overall, the main contributions of this work are the development of a low-cost, custom MATLAB-based experimental platform and the tailored implementation of optimization algorithms for kinetic parameter estimation across different biomasses, together providing a robust framework for biomass pyrolysis characterization. Full article

The olive tree (Olea europaea L.) has been cultivated for millennia, with olive oil representing both a cornerstone of the Mediterranean diet and a major agricultural commodity. Its composition, rich in monounsaturated fatty acids, polyphenols, tocopherols and squalene, supports well-documented cardioprotective, antioxidant and anti-inflammatory benefits. Olive oil production generates substantial secondary streams, including pomace, leaves, pits and mill wastewater, which are rich in phenols, triterpenes and fibers. This review consolidates recent advances in their phytochemical characterization, innovative extraction technologies and health-promoting effects, while highlighting the economic and regulatory prospects for industrial adoption. Comparative analysis shows that olive leaves can produce up to 16,674.0–50,594.3 mg/kg total phenolics; oleuropein 4570.0–27,547.7 mg/kg, pomace retains 2.24 g GAE/100 g dried matrix (DM)total phenolics; oil 13.66% DM; protein 6.64% DM, and wastewater contains high concentration of phenolics content of olives. Innovative extraction techniques, such as ultrasound and microwave-assisted methods, allow for a recovery, while reducing solvent use and energy input. The analysis highlights opportunities for integrating these by-products into circular bioeconomy models, supporting the development of functional foods, nutraceutical applications and sustainable waste management. Future research should address techno-economic feasibility, regulatory harmonization and large-scale clinical validation to accelerate market translation. Full article

Wind power is integral to the transformation of energy systems towards sustainability. However, the increasing number of wind turbines approaching the end of their service life presents significant challenges in terms of waste management and environmental sustainability. Rotor blades, typically composed of thermoset polymer composites reinforced with glass or carbon fibres, are particularly problematic due to their low recyclability and complex material structure. The aim of this article is to provide a system-level review of current end-of-life strategies for wind turbine components, with particular emphasis on blade recycling and decision-oriented comparison, and its integration into circular economy frameworks. The paper explores three main pathways: operational life extension through predictive maintenance and design optimisation; upcycling and second-life applications; and advanced recycling techniques, including mechanical, thermal, and chemical methods, and reports qualitative/quantitative indicators together with an indicative Technology Readiness Level (TRL). Recent innovations, such as solvolysis, microwave-assisted pyrolysis, and supercritical fluid treatment, offer promising recovery rates but face technological and economic as well as environmental compliance limitations. In parallel, the review considers deployment maturity and economics, including an indicative mapping of cost and deployment status to support decision-making. Simultaneously, reuse applications in the construction and infrastructure sectors—such as concrete additives or repurposed structural elements—demonstrate viable low-energy alternatives to full material recovery, although regulatory barriers remain. The study also highlights the importance of systemic approaches, including Extended Producer Responsibility (EPR), Digital Product Passports and EU-aligned policy/finance instruments, and cross-sectoral collaboration. These instruments are essential for enhancing material traceability and fostering industrial symbiosis. In conclusion, there is no universal solution for wind turbine blade recycling. Effective integration of circular principles will require tailored strategies, interdisciplinary research, and bankable policy support. Addressing these challenges is crucial for minimising the environmental footprint of the wind energy sector. Full article

Ti-bearing blast furnace slag (TBS), a byproduct of vanadium–titanium magnetite smelting, serves as an important secondary resource for titanium recovery. However, the complex mineralogical composition and finely dispersed nature of titanium in TBS present significant challenges for efficient extraction. This review systematically examines four major titanium extraction routes: hydrometallurgical leaching, pyrometallurgical smelting, molten salt electrolysis, and selective precipitation, focusing on their limitations and recent improvements. For instance, conventional acid leaching suffers from acid mist release, a colloidal formation that hinders titanium recovery, and waste acid pollution. The adoption of concentrated sulfuric acid roasting activation effectively suppresses acid mist emission and prevents colloidal generation. Pyrometallurgical approaches are hampered by high energy consumption and substantial carbon emissions, which can be alleviated through the use of gaseous reductants to enhance reaction efficiency and reduce environmental impact. Molten electrolysis faces issues such as polarization and undesirable dendritic deposition; these are mitigated by employing liquid metal cathodes integrated with vacuum distillation to achieve high-purity titanium products. Selective precipitation struggles with strict crystallization conditions and low separation efficiency, though advanced techniques like supergravity separation show improved extraction performance. We propose an integrated technical strategy termed “Online conditioning driven by waste heat-mineral phase reconstruction-directional crystallization-optimized liberation.” This approach utilizes the inherent waste heat of slag combined with electromagnetic stirring to enhance homogeneity and promote efficient titanium recovery, offering a sustainable and scalable solution for industrial TBS treatment. Full article

In Mexico, 95% of the population has access to drinking water sources, but only about 65% of domestic waste water is treated to safe levels. This study analyzes forty years of Mexican scientific production on water and waste water treatment through a bibliometric and conceptual approach, evaluating its contribution Sustainable Development Goal (SDG) 6. The analysis identified three major research clusters: (1) biological processes for water treatment, (2) development and optimization of physical–chemical processes, and (3) water quality and management. These themes reflect the evolution of biological approaches for identifying and removing organic contaminants, the application of advanced techniques for improving water quality, and the promotion of sustainable water use. The study also highlights the growing attention to emerging contaminants, nanotechnology, integrated water resource management, and persistent challenges in sanitation. With respect to SDG 6, Mexican research has mainly focused on targets 6.1 (universal and equitable access to drinking water), 6.3 (water quality), and 6.5 (water resources management), while targets 6.2 (sanitation), 6.a (international cooperation), and 6.b (community participation) remain underrepresented compared with the international benchmarks, where the research trend is on water management, resources, and the water–food–energy nexus. Finally, the findings also show synergies with SDGs 11 (sustainable cities and communities), 9 (industry, innovation, and infrastructure), and 3 (good health and well-being), although gaps persist in addressing equitable access to water and society participation. Full article

Due to the regulated nature and purity standards of the bioprocess and biotechnology industries, the sector has seen comparatively less sustainable practices than other chemical industries have. The achievement of sustainability in microbial fermenter design requires that quantitative tools with links between process parameters and end-environmental outcomes are employed. This review begins with environmentally friendly metrics such as process mass intensity, water and energy intensity, and related indicators that act as a template for resource usage and waste generation assessment. The objective of this paper is to highlight the primary focus on computational fluid dynamics (CFD) applied to bioprocesses in aerated stirred bioreactors using Escherichia coli (E. coli). Second, the objective of this paper is to explore state-of-the-art CFD models and methods documented in the existing literature, providing a fundamental foundation for researchers to incorporate CFD modelling into biotechnological process development, while making these concepts accessible to non-specialists and addressing the research gap of linking CFD outputs with sustainability metrics and life cycle assessment techniques. Impeller rotational models such as sliding mesh are an accurate and commonly used method of modelling the rotation of stirring. Multiple different turbulence models are applied for the purpose of stirred bioreactors, with the family of k-ε models being the most used. Multiphase models such as Euler-Euler models in combination with population balance models and gas dispersion models to model bubble size distribution and bubble characteristics are typically used. Full article