Resources, conservation & recycling advances最新文献

Small island developing states (SIDS) face persistent challenges in managing household solid waste due to inadequate waste management infrastructure. This study investigates the existing solid waste management practices in Nasinu Town Council, Fiji, through waste characterization survey (WACS) and life cycle assessment (LCA), accompanied by geographic information system (GIS) analysis to evaluate potential waste treatment facilities. Various strategies are explored, including recycling inorganic waste and converting organic waste into energy. Landfill gas recovery is identified as a significant contributor to reducing toxic gases like carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄) emissions. Furthermore, treating organic waste reduces landfill volume and minimizes the release of pollutants. The study emphasizes the importance of supportive policies for effective solid waste management and highlights how organic waste treatment can improve waste management in Nasinu Town. This research, unique among SIDS studies, provides valuable insights and replicable technologies applicable to the study area and the broader Pacific Region, with the potential to significantly improve solid waste management practices.

Along food supply chains, one-third of global food production is wasted annually: circular economy can be applied to prevent and recover food waste. The literature has explored food waste from many perspectives; however, no attention has been devoted to understanding how the intrinsic characteristics of food products influence food waste generation and valorization. This study proposes a classification of food products based on circular economy principles derived from a systematic literature review. The classification sheds light on how the intrinsic variability of food products influences food waste generation and recovery along the supply chain. The characteristics that drive differences in terms of food waste are identified by defining two product groups for each step of the chain (primary production: plant origin and animal origin; manufacturing: minimally processed and processed; distribution: ambient temperature and controlled temperature; retail: short shelf life and long shelf life). This stresses the intertwining of food waste with supply chain operations. Moreover, within the same supply chain stage, food waste causes and circular economy actions vary greatly depending on the product characteristics. The review also reveals how the most relevant causes within each product category correspond to a high relevance of practices addressing these causes. The adopted perspective represents a novel contribution to knowledge, providing a clear discussion of the variability of food waste along the supply chain and unveiling aspects requiring further research. From a practical standpoint, the classification can empower food industry actors to develop circular economy actions through an appropriate understanding of product characteristics.

Ethylene propylene diene rubbers (EPDM) have gained substantial attention in automotive and industrial applications owing to their exceptional resistance against weathering and heat. Despite their advantages, the elastomeric nature of EPDM poses challenges in its recycling due to the presence of crosslinks in their chemical structure, preventing them from melting. To overcome this issue, devulcanized EPDM (EPDMd) has been developed, characterized by the effective breaking of these crosslinks. Our study focuses on common composites that include Styrene Butadiene Rubber (SBR), EPDM and silica, but with the incorporation of devulcanized EPDM (EPDMd).

We have studied the mechanical, thermal, structural and dielectric properties of SBR composites containing EPDMd at variable compositions (0, 20, 40, 50, 60 phr). Employing techniques such as Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectropy (FTIR), and Scanning Electronic Microscopy (SEM), we have explored the microstructural changes driving the macroscopic effects on the measured properties.

The results show that incorporating EPDMd improves the crosslinking degree and, at optimal 40 phr loading, significantly increases the mechanical properties of SBR matrix. The addition of SiO₂, in general, reduce tensile strength and elongation, while increasing the Young's modulus, except for compositions around 40 phr EPDMd. The dielectric measurements are in concordance with the previous data, showing a moderation of the Maxwell–Wagner–Sillars (MWS) effect due to SiO2 in highly filled EPDMd composites at 40 phr EPDMd.

Estimating the operating conditions using conventional process analysis techniques for the maximum metal extraction from the wasted printed circuit boards (WPCB) can provide sub-optimal solutions leading to the low yield of the process. In this paper, we present a closed-loop methodological framework built on machine learning and robust mathematical optimization technique, that offers the mathematical rigour, to determine the optimum operating conditions for the maximum Cu and Ni recovery from the WPCB. Alkali leaching based novel metals recovery process from the WPCB is designed, and the experiments are conducted to collect the data on the percentage recovery of Cu and Ni against the operating levels of the process input variables (ammonia concentration (NH₃ conc. (g/L)), ammonium sulfate concentration ((NH₄)₂SO₄ conc. (g/L)), H₂O₂ concentration (H₂O₂ conc. (M)), time (h), liquid to solid ratio (L/S ratio, (mL/g)), temperature (Temp. (°C)), and stirring speed (rpm)). The experimental data is deployed to construct the functional mapping between the nonlinear output variables of metals recovery process with the hyperdimensional input space through artificial neural network (ANN) based modelling algorithm – a powerful universal function approximator. Well-predictive ANN models for Cu and Ni recovery are developed having co-efficient of determination (R²) value more than 0.90. Partial derivative-based sensitivity analysis is then carried out to establish the order of the significance of the input variables that is backed by the domain knowledge, thus promotes the interpretability of the trained ANN models. The hybridization of ANN with NLP (nonlinear programming) framework is implemented for the determination of optimized operating conditions to extract maximum Cu and Ni under separate and combined model of metal extraction. The robustness of the determined solutions is verified, the determined optimized solutions for the metal recovery are validated in the lab, and the maximum metal recovery, i.e., 100 % Cu and 90 % Ni is extracted from the WPCB. This research demonstrates the effective utilization of ANN model-based robust optimization approach for the metal recovery from the WPCB that supports the circular economy for the metal extraction industry.

The reduction of iron oxide-bearing ores necessitates the exploration of alternatives. Recycling iron oxide-enriched metallurgical dust could serve as secondary raw material for metallurgical processes. Implementing environmentally friendly technologies utilizing hydrogen has prompted the concept of hydrogen reduction of metallurgical dust to recycle secondary steel production products. The present study investigates the characteristics of hydrogen reduction of briquettes and pellets produced from basic oxygen furnace dust and reduced at the temperature of 850 °C. Experimental results revealed that the reduction degree for pellets was approximately 1.5 times higher compared to briquettes. The reduction swelling index of pellets was noticeable lower compared to literature data of reduction swelling index for iron ore pellets. Scanning electron microscopy/energy-dispersive X-ray spectroscopy was carried out to detect changes in the microstructure and chemical composition of the samples. Subsequent melting of the reduced samples unveiled non-metallic inclusions within the iron alloy and the impact of slag on their distribution between the alloy and slag.

At the current stage of development, the transition to a circular economy is a single option to achieve sustainable mining. Purpose was to identify a direction for mining tailings usage based on the circular waste management. The novelty of the author's approach lies in regulation of mechanical treatment of slag to optimize the backfill composition. The methodology involved a study of mining waste (slag) obtained from major (eight) metallurgical plants in Russia. For mathematical processing primary data, smoothing and deterministic three-dimensional interpolation methods were used. As a result, for the first time it has been established that the ultimate uniaxial compressive strength after mechanical treatment of slag increases by logarithmic laws. As the curing time increases from 10 days to 90 days (with the addition of Ca or Si) the strength increases by 21 % (7 % and 23 %). The possibility of completely replacing the traditional cement binder with metallurgical slag in the backfill composite has been proven. It has been established that the use of activation treatment (both mechanical and chemical) makes it possible to increase the strength characteristics of backfill samples after their curing. The principle of organizing mining production has been implemented, which provides for the use of intermediate products (blast furnace granulated slag), previously classified as technogenic waste, in a closed production cycle. The introduction of this principle will eliminate (minimize) the formation of man-made waste. The scientific merit of replacing traditional cement binder with technogenic waste (blast furnace granulated slag) allows implementation of circular economy in mining.

Aviation plays a crucial role in global economic growth and can be influenced by events like COVID-19 and climate change. The aviation sector has a significant carbon footprint that can be correlated with extreme weather conditions, outlining challenges faced by airports and proposing strategies such as environmental management, advanced fuels, and retirement of older aircraft. This review analyzes 107 scientific papers and reports to explore the opportunities to integrate a circular economy (CE) within the aviation sector, emphasizing on waste management and circular aviation practices. It highlights the sector's initiatives on in-cabin waste reduction, waste tracking systems, and plastic-free flights. Moreover, it covers the industry's efforts to adopt circular economy principles to convert waste (in-cabin and end-of-use) into Sustainable Aviation Fuels (SAFs). It outlines diverse biofuel production methods, including alcohol upgrading, fermentation, gasification-Fischer Tropsch, and thermochemical processes. It also discusses innovative technologies such as microbial and enzymatic approaches and power-to-liquid (PtL). The review examines the global challenges and policies surrounding sustainable waste management in airports, emphasizing the disconnect between sustainability goals and rising waste output accompanying the need for more effective policies and research on emissions quotas and consumption patterns. Additionally, it addresses the need for collaboration and innovative technologies regarding waste-to-energy (WtE) conversion to achieve comprehensive and efficient airport waste management strategies. The integration of CE within airport vicinities is vital to mitigate the environmental impacts by emphasizing the importance of waste management strategies and utilizing aviation waste such as cabin waste and end-of-use waste as a valuable resource for SAFs production, which continues to face several challenges related to scalability, technological readiness, and economic viability.

Gypsum is a widely used building material with a variety of benefits, including good fire resistance, sound insulation, and environmental friendliness. However, gypsum disposal is commonly associated with significant environmental risks, including unhealthy gas emissions and land degradation. Gypsum recycling can help to reduce these impacts, but it can also lead to a decrease in the performance of the recycled gypsum products. This study investigated the effects of graphene nanofibers (GNFs) on the recyclability and properties of gypsum plasters. The results showed that test samples containing 1 % of GNFs exhibited improved mechanical response, with flexural and compressive strength exceeding those of neat gypsum by 30 % and 60 % respectively. This improvement is attributed to the retained functional properties of GNFs during the recycling process. Recycled gypsum pastes containing GNFs presented a more uniform and denser matrix with longer crystals, enhanced bonding, and reduced porosity. These findings suggest that GNFs can be used to facilitate the recycling of gypsum waste and to produce recycled gypsum components with improved properties. Overall, this study demonstrates the potential of GNFs to improve the sustainability and performance of recycled gypsum plasters.