Search Results (297)

Bioponics is a promising agricultural system designed to integrate circular economy principles by recovering nutrients from organic waste. In this context we implemented a tri-trophic circular system, where insect larvae fed on crop residues and fruits were processed into insect meal for fish feed. The water used in fish rearing then irrigated tomato crops in an aquaponic setup, closing the nutritional loop. Tomato was cultivated in this system with the aim of thoroughly evaluating its applicability via assessing the dynamics of growth, yield, and functional responses of the crop across three treatments: coupled aquaponics (CAP), decoupled aquaponics (DCAP), and hydroponics (HP, as control). DCAP matched HP in all parameters assessed and even outperformed it in fertilizer use efficiency by 31%. In contrast, CAP showed reduced growth and yield (by 38%) and limitations in photochemical efficiency and photosynthetic performance, likely due to significant deficiencies in potassium and phosphorus (9-fold and 2-fold lower than in HP, respectively). DCAP demonstrated strong potential to achieve similar crop outcomes to conventional hydroponics with enhanced resource efficiency. Overall, adopting the DCAP variant of aquaponics in this circular nutrition system is a promising alternative to conventional hydroponics, supporting a transition toward more environmentally resilient farming practices. Full article

As the demand for more efficient energy storage solutions grows, emerging battery chemistries are being developed to complement or potentially replace conventional lithium-ion technologies. This review explores the circular economy potential of sodium (Na), magnesium (Mg), zinc (Zn), and aluminum (Al) battery systems as alternative post-lithium configurations. Through a comparative literature analysis, it identifies key barriers related to material complexity, recovery efficiency, and regulatory gaps, while highlighting opportunities for design improvements and policy alignment to enhance sustainability across battery life cycles. However, end-of-life (EoL) material recovery remains constrained by complex chemistries, low technology readiness levels, and fragmented regulatory frameworks. Embedding materials/battery design principles, transparent life cycle assessment (LCA) data (e.g., publishing LCAs in open repositories using a standard functional unit), and harmonized policy early could close material loops and transform the rising post-lithium battery stream into a circular-economy resource rather than a waste burden. Full article

The depletion of shallow coal reserves necessitates a shift from open-pit to underground mining, increasing the need for safe and efficient backfill systems. However, traditional backfill materials—especially cement—are costly and environmentally burdensome. To address this, our study explores a sustainable alternative using industrial waste, contributing to the principles of a circular economy. This research presents a novel backfill formulation that achieves full cement replacement through the use of fly ash, supplemented with nanocrystalline silica and glass fiber to enhance strength and setting dynamics. Eighteen sample sets were prepared for each composition, using consistent mixing, curing, and testing protocols. Mechanical strength was evaluated at multiple curing intervals alongside microstructural characterization using SEM and XRD. The results show that mixtures containing nanomodified silica and fiber exhibit significantly improved compressive, shear, and splitting strength—up to 40% higher than fly ash-only compositions. Microstructural analysis revealed accelerated C-S-H gel development, reduced porosity, and more uniform pore structures over time. These findings confirm the mechanical viability and economic potential of waste-based backfill systems. The proposed formulation enables safer underground operations, improved extraction efficiency, and reduced environmental impact—offering a scalable solution for modern coal mining. Full article

This study evaluates the environmental impact of swimming goggles through a Life Cycle Assessment (LCA), comparing virgin and recycled polycarbonate models. It identifies key hotspots, assesses circular economy benefits, and examines barriers to sustainable disposal, aligning with European Union’s (EU) 2050 sustainability objectives. The LCA was modeled using SimaPro, with the Environmental Footprint (EF) 3.1 method to analyze 16 impact categories (e.g., climate change, human toxicity, resource depletion). Two scenarios were assessed: (1) virgin polycarbonate production and (2) a closed-loop system (80% recycled content, 30% reintegration). Primary data from a survey of 150 competitive swimmers quantified disposal behaviors. The lens production phase (bisphenol A processing) dominated impacts, contributing to 62% of climate change and 75% of human toxicity. The recycling scenario reduced total impact by 23.1% (119 → 91.5 mPt), with significant declines in freshwater ecotoxicity (−28.6%) and marine eutrophication (−25.1%). Survey data highlighted critical gaps: low consumer participation in recycling due to lack of awareness and inadequate disposal infrastructure. Recycled polycarbonate can substantially mitigate environmental impacts, but systemic barriers (consumer behavior, collection gaps) limit progress. Future work should explore bio-based polymers and policy incentives to accelerate circularity. Full article

This paper innovatively constructs a comprehensive material cycle network framework for the circular economy system of the coal industry and evaluates the circular economy efficiency of China’s provincial coal industry from 2011 to 2021 using a comprehensive evaluation model that integrates emergy analysis and dynamic network data envelopment analysis (DEA). The research delves into the evolutionary characteristics of the coal industry’s circular economy and identifies the underlying causes of inefficiency. The results reveal that the circular economy in China’s coal industry has gone through three stages: the transformation period, the reinforcement period, and the growth period, with the inefficiency of waste reutilization being the key factor restricting the overall improvement in efficiency. The circular economy model in the production phase is gradually shifting from an extensive linear model to a clean, closed-loop model, while a significant gap remains between the high-emission linear model and the low-pollution closed-loop model in the utilization phase. Furthermore, regional heterogeneity mainly arises from imbalances in the operational efficiency of the circular economy system. This study not only reveals the deep-seated reasons for the low efficiency of circular economy in China’s coal industry but also provides strategies and directions for achieving a more efficient circular economy and carbon mitigation goals. Full article

Circular agriculture reclaims nutrients from waste streams to reduce fertilizer imports, mitigate environmental impacts, and close material loops. This review evaluates the agronomic performance of nitrogen, phosphorus, and potassium products recovered from wastewater, crop residues, and manure compared with conventional fertilizers. A structured literature survey identified 85 pot and field trials published between 2010 and 2024, covering ammonium salts, struvite, ashes, compost, digestate, biochar, hydrochar, and biostimulants. Ammonium sulfate and nitrate consistently matched synthetic yields (95–105%) due to their solubility and immediate N availability, while aqueous ammonia showed variable results depending on application timing and soil pH. Struvite and phosphorus-rich ashes performed best (90–100%) in neutral to slightly acidic soils, whereas organo-mineral phosphate fertilizers (85–95%) were less effective in alkaline soils. Potassium-rich ashes and waste mica were effective (80–95%) in soils with moderate cation exchange, though mica underperformed (60–75%) in coarse soils. Biochars and hydrochars improved soil water retention and nutrient exchange, yielding 90–110% of synthetic performance, while biostimulants increased yields by 8–20%. Recovered products demonstrate agronomic equivalence while offering co-benefits for soil health, waste management, and circular economy goals. Future work should prioritize long-term field validation, techno-economic analysis, and regulatory integration to enable large-scale adoption. Full article

The processing of freshly cut fruits and vegetables represents an important niche for implementing circular economy principles, particularly through the reuse of washing water. This is especially relevant as post-wash water is often treated as wastewater and discarded without reuse. One promising research avenue is the use of plant-derived extracts in water sanitation processes. Their antimicrobial properties offer a natural alternative to conventional disinfectants while reducing the formation of harmful disinfection by-products. The aim of this study was to evaluate the effectiveness of different filter bed configurations in removing pathogens from water. These configurations included a hydrogel saturated with natural plant extracts, an ion exchange resin layer, and an activated carbon layer. The most effective composite was also tested using real process water from a fruit washing line. The test materials included concentrated extracts from oak bark (Quercus robur), willow (Salix alba), birch (Betula pendula), raspberry shoots (Rubus idaeus), tea leaves (Camellia sinensis), and linden flowers (Tilia cordata), all immobilized in hydrogel, along with activated carbon and ion-exchange resin. Water samples were artificially inoculated with six opportunistic pathogens and collected process water was also used. Samples were analyzed microbiologically at six time intervals. The composite filter (hydrogel–resin–carbon) achieved a reduction of over 2 log₁₀ in heavily inoculated water (~10⁸ CFU mL⁻¹) and maintained at least a 1 log₁₀ reduction in real process effluents. The proposed solution supports blue water footprint reduction strategies (as the system aims to decrease the demand for freshwater resources through the reuse of treated wastewater) and aligns with the principles of green processing. Full article

Flexible polyurethane foams (PUFs) are widely used materials whose crosslinked chemical structure hinders conventional recycling, leading to significant environmental challenges. This study presents a selective and scalable depolymerization strategy for polyurethane foam waste (PUFW), utilizing a combination of 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) as water-miscible ionic liquid (IL) and a strong organic base to enable hydrolytic cleavage of urethane bonds under mild reaction conditions (98 °C, atmospheric pressure). The approach was evaluated across different PUFW formulations and successfully scaled up to a 1 kg reaction mass, maintaining high efficiency in both the depolymerization and separation steps. The recovered polyols exhibited high purity and structural fidelity, comparable to those of virgin polyols. The recycled products were integrated into a new foam formulation, resulting in a PUF with mechanical and morphological properties, as revelated by scanning electron microscopy (SEM), which closely resemble those of virgin polyol-based references and surpass those of foams produced using commercially recycled polyols. These findings support the feasibility of closed-loop polyurethane recycling and represent the transition towards circular polymer economy strategies. Full article

The integration of digital twin (DT) technology into circular economy (CE) frameworks has emerged as a critical pathway for achieving sustainable and intelligent manufacturing under the Industry 4.0 paradigm. This study addresses the lack of structured guidance for DT adoption in CE strategies by proposing two interrelated frameworks: the Sustainable Digital Twin Maturity Path (SDT-MP) and the Digital Twin Nexus. The SDT-MP outlines progressive stages of DT deployment—from data acquisition and real-time monitoring to AI-enabled decision-making—aligned with CE principles and Industry 4.0 capabilities. The DT Nexus complements this maturity model by structuring the integration of enabling technologies such as AI, IoT, and edge/cloud computing to support closed-loop control, resource optimization, and predictive analytics. Through a mixed-methods approach combining literature analysis and real-world case validation, this research demonstrates how DTs can facilitate lifecycle intelligence, enhance operational efficiency, and drive sustainable transformation in manufacturing. The proposed frameworks offer a scalable roadmap for intelligent circular systems, addressing implementation challenges while supporting Sustainable Development Goal 9 (Industry, Innovation, and Infrastructure) by promoting digital infrastructure, innovation-driven manufacturing, and environmentally responsible industrial growth. This study contributes to the advancement of digital infrastructure and sustainable circular supply chains in the context of smart, connected industrial ecosystems. Full article

The recycling rate of silage and stretch films is low. The low degree of recycling of polymer films used in agriculture results from the high contamination of films and technological problems in their processing. Material recycling of haylage preservation films is conditioned by the possibility of their effective and cost-effective cleaning. Thus, the study focuses on designing a new generation material for wrapping hay-silage bales that meet the closed-loop material cycle condition while at the same time guaranteeing the desired operating conditions. The developed new generation silage films made it possible to achieve 100% recycling, while this indicator for traditional films did not exceed 50%. The concept is based on the notion of circular economy. The study compared four types of film—one that is commonly used for feed preservation and three types of new generation film. The nanosilver-containing film and the film containing a microbiological additive of zinc provided a high quality of silage and, due to the low contamination, facilitated the recycling of the burdensome waste. The 8% microcellulose film had too little viscosity, which was why it did not cut off the atmospheric air penetration into the bale. Hence, the biodegradable film with the addition of microcellulose does not comply with the technological regime for feed preservation. Full article

This study aims to evaluate eco-innovative solutions in the fertilizer industry that allow for waste valorization in the context of a resource-efficient circular economy. A comprehensive reuse strategy was developed for low-rank peat and post-cultivation horticultural mineral wool, involving the extraction of valuable humic substances from peat and residual nutrients from used mineral wool, followed by the use of both post-extraction residues to produce organic–mineral substrates. The resulting products/semifinished products were characterized in terms of their composition and properties, which met the requirements necessary to obtain the admission of this type of product to the market in accordance with the Regulation of the Minister for Agriculture and Rural Development of 18 June 2008 on the implementation of certain provisions of the Act on fertilizers and fertilization (Journal of Laws No 119, item 765). Elemental analysis, FTIR spectroscopy, and solid-state CP-MAS ¹³C NMR spectroscopy suggest that post-extraction peat has a relatively condensed structure with a high C content (47.4%) and a reduced O/C atomic ratio and is rich in alkyl-like matter (63.2%) but devoid of some functional groups in favor of extracted fulvic acids. Therefore, it remains a valuable organic biowaste, which, in combination with post-extraction waste mineral wool in a ratio of 60:40 and possibly the addition of mineral nutrients, allows us to obtain a completely new substrate with a bulk density of 264 g/m³, a salinity of 7.8 g/dm³ and a pH of 5.3, with an appropriate content of heavy metals and with no impurities, meeting the requirements of this type of product. A liquid fertilizer based on an extract containing previously recovered nutrients also meets the criteria in terms of quality and content of impurities and can potentially be used as a fertilizing product suitable for agricultural crops. This study demonstrates a feasible pathway for transforming specific waste streams into valuable agricultural inputs, contributing to environmental protection and sustainable production. The production of a new liquid fertilizer using nutrients recovered from post-cultivation mineral wool and the preparation of an organic–mineral substrate using post-extraction solid residue is a rational strategy for recycling hard-to-biodegrade end-of-life products. Full article

The stretch film production is highly energy intensive. The components of the technological line are powered by electrical energy, and the heat is used to change the physical state of the raw material (granules). The raw material is poured into FCR (the first calender roller). To solidify the liquid raw material, the calendar must be cooled. The low-temperature heat, treated as waste heat, has dissipated in the atmosphere. Technological innovations were proposed: (a) the raw material comprises raw material (primary) and up to 80% recyclate (waste originating mainly from agriculture), (b) the use of low-temperature waste heat (the cooling of FCR in the process of foil stretch production). A heat recovery line based on two compressor heat pumps (HP, hydraulically coupled) was designed. The waste heat (by low-temperature HP) was transformed into high-temperature heat (by high-temperature HP) and used to prepare the raw material. The proposed technological line enables the management of difficult-to-manage post-production waste (i.e., agriculture and other economic sectors). It reduces energy consumption and raw materials from non-renewable sources (CO₂ and other greenhouse gas emissions are reducing). It implements a closed-loop economy based on renewable energy sources (according to the European Green Deal). Full article

In response to growing environmental pressures and material constraints, circular economy principles are gaining traction across manufacturing sectors. However, most existing frameworks emphasize design and supply chain considerations, with limited focus on how circularity can be operationalized within internal manufacturing systems. This paper proposes a conceptual model that embeds circular operations at the core of production strategy. Grounded in circular economy theory, operations management, and socio-technical systems thinking, the model identifies four key operational pillars: circular input management, looping process and waste valorization, product-life extension, and reverse logistics. These are supported by enabling factors—digital infrastructure, organizational culture, and leadership—and mediated by operational flexibility, which facilitates adaptive, closed-loop performance. The model aims to align internal processes with long-term sustainability outcomes, specifically resource efficiency and operational resilience. Practical implications are outlined for resource-intensive industries such as automotive, electronics, and FMCG, along with a readiness assessment framework for guiding implementation. This study offers a pathway for future empirical research and policy development by integrating circular logic into the structural and behavioral dimensions of operations. The model contributes to advancing the Sustainable Development Goals (SDGs), particularly SDG 9 and SDG 12, by positioning circularity as a regenerative operational strategy rather than a peripheral initiative. Full article

This study extends our prior blockchain-based traceability framework, WEave, for application to a furniture supply chain scenario, while using the original multi-tier apparel supply chain as an anchoring use case. We integrate circular economy principles such as product reuse, recycling traceability, and full lifecycle transparency to bolster sustainability and resilience in supply chains by enabling data-driven accountability and tracking for closed-loop resource flows. The enhanced approach can track post-consumer returns, use of recycled materials, and second-life goods, all represented using a closed-loop supply chain topology. We describe the extended network architecture and smart contract logic needed to capture circular lifecycle events, while proposing new metrics for evaluating lifecycle traceability and reuse auditability. To validate the extended framework, we outline simulation experiments that incorporate circular flows and cross-industry scenarios. Results from these simulations indicate improved transparency on recycled content, audit trails for returned products, and acceptable performance overhead when scaling to different product domains. Finally, we offer conclusions and recommendations for implementing WEave functionality into real-world settings consistent with the goals of digital, resilient, and sustainable supply chains. Full article

This paper introduces sustainable engineering systems built using digital twin technology and circular economy principles. This research presents a framework for monitoring, modeling, and making decisions in real timusing virtual replicas of physical products, processes, and systems in product lifecycles. A digital twin was used to show that through a digital twin, waste was reduced by 27%, energy consumption was reduced by 32%, and the resource recovery rate increased to 45%. The proposed approach under the framework employs various machine learning algorithms, IoT sensor networks, and advanced data analytics to support closed-loop flows of materials. The results show how digital twins can enhance progress toward the goals the circular economy sets to identify inefficiencies, predict maintenance needs, and optimize the use of resources. This integration is a promising industry approach that will introduce more sustainable operations and maintain economic viability. Full article