Recycled Materials Research Articles

Straightforward identification of flow curve and yield locus parameters from three-point bending experiments

Material testing and modeling is one of the cornerstones of virtual analysis of sheet metal forming processes. However, it is also becoming more and more relevant for incoming goods inspection, especially in view of the increasing amount of recycled material or frequent changes of suppliers, e.g. to provide workers, processes and/or process models with relevant information about a new batch of material. Efficient material testing and straight-forward test evaluation is essential for this. The flow curve and yield locus are central to describe the forming behavior of sheet metal materials. However, the parameters of the associated models are currently determined in various tests on different systems and with special sample geometries. The present work presents a methodology that allows the determination of a set of flow curve and yield locus parameters from three three-point bending tests only. The evaluation routine does not require finite element simulation and processes only the force-displacement information of the bending tests, which also places low demands on the measurement technology. The results were compared with a conventionally determined parameter set using a validation test, and the results are of reasonable quality, especially considering the minimal effort involved.

The Influence of the Comonomer Ratio and Reaction Temperature on the Mechanical, Thermal, and Morphological Properties of Lignin Oil-Sulfur Composites.

Although lignin is a plentiful biomass resource, it continually exists as an underutilized component of biomass material. Elemental sulfur is another abundant yet underutilized commodity produced as a by-product resulting from the refining of fossil fuels. The current study presents a strategy for preparing five durable composites via a simple one-pot synthesis involving the reaction of lignin oil and elemental sulfur. These lignin oil-sulfur composites LOSx@T (where x = wt. % sulfur, ranging from 80 to 90, and T represents the reaction temperature in °C) were prepared via the reaction of elemental sulfur and lignin oil (LO) with elemental sulfur. The resulting composites could be remelted and reshaped several times without the loss of mechanical strength. Mechanical, thermal, and morphological studies showed that LOSx@T possesses properties competitive with some mechanical properties of commercial building materials, exhibiting favorable compressive strengths (22.1-35.9 MPa) and flexural strengths (5.7-6.5 MPa) exceeding the values required for many construction applications of ordinary Portland cement (OPC) and brick formulations. While varying the amount of organic material did not result in a notable difference in mechanical strength, increasing the reaction temperature from 230 to 300 °C resulted in a significant increase in compressive strength. The results reported herein reveal potential applications of both lignin and waste sulfur during the ongoing effort toward developing recyclable and sustainable building materials.

Performance enhancement of asphalt mixture through the addition of recycled polymer materials

Enhancing the performance of asphalt binders is essential for ensuring the long-term durability and serviceability of asphalt mixtures, as it can help reduce the frequency of maintenance and repair work, ultimately leading to the development of more sustainable transportation infrastructure. To achieve this goal, this study investigates the effects of incorporating recycled polymer materials, including reclaimed polyvinyl chloride (PVC) and polystyrene (PS) derived from household waste, into hot mix asphalt. The experimental work involved subjecting the polymer-modified asphalt binders to a range of physical tests, such as softening point, penetration, ductility, indirect tensile strength, Marshall stability, and moisture susceptibility, and the results showed that the addition of recycled polymers, with an optimal content of 4%, led to lower penetration values and higher softening point temperatures, indicating improved resistance to temperature changes. Further analysis of the asphalt mixture performance revealed several beneficial outcomes, including a decrease in flow, a boost in the asphalt mixture's resistance to moisture-induced damage, and an improvement in Marshall stability and indirect tensile strength, with the inclusion of 4% recycled polymers yielding increases in Marshall stability of 43.7% and 37.4% for PVC and PS-modified mixes, respectively, and increments in indirect tensile strength of 32.2% and 29.7% for the same mixes. The study concludes that the use of recycled polymers can effectively enhance the performance and durability of asphalt mixtures, contributing to the development of more sustainable asphalt pavement construction practices by utilizing locally available or reused materials, which could lead to the increased knowledge and application of stronger and more weather-resistant asphalt mixes, ultimately promoting the advancement of sustainable transportation infrastructure.

Shear Behavior and Modeling of Short Glass Fiber- and Talc-Filled Recycled Polypropylene Composites at Different Operating Temperatures

The present paper aims to broaden the field of application of the phenomenological model proposed by the authors in a previous study (ICP model) and to assess the shear properties of a recycled 30 wt.% talc-filled polypropylene (TFPP) and a recycled 30 wt.% short glass fiber-reinforced polypropylene (SGFPP), used in the automotive industry. The materials were produced by injection molding employing post-industrial mechanical shredding of recycled materials. In particular, Iosipescu shear tests adopting the American Standard for Testing Materials (ASTM D5379) at three different operating temperatures (−40, 23 and 85 °C) were performed. The strain was acquired using a Digital Image Correlation (DIC) system to determine the map of the strain in the area of interest before failure. Lower operating temperatures led to higher shear chord moduli and higher strengths. Recycled SGFPP material showed higher mechanical properties and smaller strains at failure with respect to recycled TFPP. Finally, the ICP model also proved to be suitable and accurate for the prediction of the shear behavior of 30 wt.% SGFPP and 30 wt.% TFPP across different operating temperatures.

Construction engineering in China under green Transition: Policy research Topic clusters and development forecasts

China’s construction engineering market is gradually transitioning towards high-quality development, driven by policies such as green and low-carbon. Identifying research topics for China’s construction engineering policy and predicting future research trends are crucial for policymakers to make informed decisions and promote the transformation of the construction industry. This study combines Latent Dirichlet Allocation (LDA) and Autoregressive Integrated Moving Average Model (ARIMA) to analyze more than 6,500 relevant literature abstracts. The LDA model identified 11 key topics, with the five hottest topics conceptualized with trend prediction. ARIMA-based trend forecasts show that these topics will continue to grow over the next two years. Energy Consumption in Construction (Topic 2) is caused by the urgency of transforming China’s construction industry. The environmental impacts of green construction (Topic 6) are due to the sustainability potential of the green construction model. The relationship between urbanization, the economy and the environment (Topic 7) was prompted by the discussion that the relationship between them is still unclear. The use of recyclable materials in construction (Topic 8) is a result of resource depletion and environmental degradation. The relationship between urbanization and ecosystems (Topic 9) was prompted by the environmental problems associated with China’s high rate of urbanization. These findings reveal the focus and development trend of construction engineering transformation in China and provide feedback to policy makers and companies from the perspective of experts and scholars. The accuracy of the predictions can be further improved in the future through data updates and multi-modeling combinations.

Exploring the use of recycled materials in interior design and their environmental benefits

Sustainable and environmentally friendly interior design practices have grown in popularity in recent years. The field of interior architecture has adopted a fresh perspective in its design process. Consideration of both the user's and the environment's well-being are central to sustainable interior design. Sustainable interior design is discussed in the article, along with the significance and use of certain materials. In addition, examples of completed projects that prioritize environmental friendliness are shown, along with the fundamental principles of sustainable design. As a result of the economy's meteoric rise, "green ecology" has quickly gained widespread acceptance. Investigating and studying the potential uses of biodegradable materials in this setting is worthwhile. The use of biodegradable materials in home decor is the topic of this article. Avoidance, reduction, and reuse are the three main tenets of waste minimization initiatives.

Transforming Urban Sanitation: Enhancing Sustainability through Machine Learning-Driven Waste Processing

The enormous increase in the volume of waste caused by the population boom in cities is placing a considerable burden on waste processing in cities. The inefficiency and high costs of conventional approaches exacerbate the risks to the environment and human health. This article proposes a thorough approach that combines deep learning models, IoT technologies, and easily accessible resources to overcome these challenges. Our main goal is to advance a framework for intelligent waste processing that utilizes Internet of Things sensors and deep learning algorithms. The proposed framework is based on Raspberry Pi 4 with a camera module and TensorFlow Lite version 2.13. and enables the classification and categorization of trash in real time. When trash objects are identified, a servo motor mounted on a plastic plate ensures that the trash is sorted into appropriate compartments based on the model’s classification. This strategy aims to reduce overall health risks in urban areas by improving waste sorting techniques, monitoring the condition of garbage cans, and promoting sanitation through efficient waste separation. By streamlining waste handling processes and enabling the creation of recyclable materials, this framework contributes to a more sustainable waste management system.

Integration of Sustainable and Net-Zero Concepts in Shape-Memory Polymer Composites to Enhance Environmental Performance.

This review research aims to enhance the sustainability and functionality of shape-memory polymer composites (SMPCs) by integrating advanced 4D printing technologies and sustainable manufacturing practices. The primary objectives are to reduce environmental impact, improve material efficiency, and expand the design capabilities of SMPCs. The methodology involved incorporating recycled materials, bio-based additives, and smart materials into 4D printing processes, and conducting a comprehensive environmental impact and performance metrics analysis. Significant findings include a 30% reduction in material waste, a 25% decrease in energy consumption during production, and a 20% improvement in shape-memory recovery with a margin of error of ±3%. Notably, the study highlights the potential use of these SMPCs as biomimetic structural biomaterials and scaffolds, particularly in tissue engineering and regenerative medicine. The ability of SMPCs to undergo shape transformations in response to external stimuli makes them ideal for creating dynamic scaffolds that mimic the mechanical properties of natural tissues. This increased design flexibility, enabled by 4D printing, opens new avenues for developing complex, adaptive structures that support cell growth and tissue regeneration. In conclusion, the research demonstrates the potential of combining sustainable practices with 4D printing to achieve significant environmental, performance, and biomedical advancements in SMPC manufacturing.

Principles for Incorporating Recycled Materials into Airport Pavement Construction for More Sustainable Airport Pavements

Current international waste policy promotes the reduction and re-use of waste materials, and in some cases, specifically calls for the use of recycled materials in pavements. Consequently, there is a need to understand the performance of recycled materials in airport pavements, as well as the overall sustainability benefit. This paper reviews several recycled materials and their applications to asphalt concrete, cement concrete, and bound and unbound granular materials in the context of airport pavements. Additionally, it reviews sustainability quantification methods, as well as implementation challenges for using recycled materials in airport pavements. For comparing pavements with and without recycled materials, a triple bottom line approach is appropriate. The triple bottom line approach should use life cycle cost assessment and life cycle assessment for the financial and environmental impacts, respectively, as best-practice, with frameworks and guidelines already established. For social impacts, it is recommended to quantify the reduction in virgin material use which relates to intergenerational equity by ensuring access to materials by future generations. Because there are still implementation challenges for the airport pavement industry, principles are developed that aim to promote uptake of recycled materials. These principles include sorting and processing, minimising haulage distances, and ensuring performance of pavement layers through performance testing and performance-related specifications.

Intensified biogas to liquid (IBGTL) Process: Experimental validation and modeling analysis

The Intensified Biogas to Liquid (IBGTL) process aims to overcome traditional economy-of-scale barriers in biogas-to-liquid fuel production by integrating bi-reforming and Fischer-Tropsch synthesis (FTS) in a single IBGTL reactor. This reactor operates at uniform pressure with different optimized temperatures across two zones for efficient conversion, utilizing multifunctional bi-reforming catalysts and high-temperature FTS catalysts.Bench scale experiments were carried out using landfill gas (LFG) in a single pass process, and the yield data from these experiments were fed into process scale-up design and techno-economic analysis (TEA) across four scenarios: (1) a single pass process, (2) a process with material recycling, (3) a process with liquefied petroleum gas (LPG) co-product recovery, and (4) a process with electricity generation from the fuel gas produced. TEA identified Scenario 2 as the most cost-effective, achieving a Minimum Fuel Selling Price (MFSP) of $4.59 per gallon, competitive with the current national diesel price of $4.7 per gallon. However, comparison with the conventional two-reactor system highlights the need for catalyst performance improvements.Sensitivity analysis emphasized the importance of manufacturing cost, liquid fuel yield, and biogas flow rate. Further analysis determined that the IBGTL process must achieve a diesel mass yield beyond 11.7% to surpass the economic viability of the conventional TriFTS (Tri-reforming followed by Fischer-Tropsch Synthesis) process. If the IBGTL process attains the TriFTS yield of up to 17%, the resulting MFSP could be approximately 31% lower than the current TriFTS MFSP. Renewable energy credits and carbon credits can further enhance the economic viability of BGTL processes.

Recyclable and Stable Strain Sensors Based on Semi‐Wrapped Structure of Silver Nanowires in Polyvinyl Alcohol for Human Motion Monitoring

AbstractHighly sensitive strain sensors have been widely used in human motion monitoring, medical treatment, soft robots, and human–computer interaction, and the recycling of functional materials is in a huge demand for eco‐friendly and sustainable electronics. However, the manufacturing of recyclable strain sensors still remains challenging. Here, a semi‐wrapped structure based on silver nanowires and polyvinyl alcohol is proposed to realize a recyclable and stable strain sensor. It has shown excellent sensitivity, fast response, high stretchability and good environmental stability, and is successfully applied for human motion monitoring. In addition, a simple strategy is developed to effectively recycle silver nanowires in an eco‐friendly manner. The recyclable and stable strain sensor demonstrates potential applications in wearable and stretchable electronics, and the recycling strategy can be extended to other noble metal nanomaterials.

Geopolymer-based insulated wall incorporating construction and demolition waste: Experimental assessment of thermo-physical behavior

The benefit of the application of geopolymers in the building sector is nowadays undisputed. In addition to good structural characteristics, these are characterized by interesting thermophysical properties, obtained through a production process, that reduces CO2 emissions and could incorporate recycled material, thus responding to environmental sustainability. However, it is noted the lack of studies regarding the in-field thermal performance. Thus, the aim of the present study is to investigate the thermal performance, under real conditions, of an innovative geopolymer-based insulated wall. It incorporates over 70% of net weight of Construction and Demolition Waste materials. The wall is conceived within the European project called “Green INSTRUCT” aimed to realize modular prefabricated building elements, for retrofitting and new construction of buildings. Two wall prototypes are analysed, which differ for the type of lightweight aggregate of geopolymer matrix, 3% by weight: expanded polystyrene or extruded polystyrene. The study refers to almost one year of continuous monitoring within a full-scale test room located in southern Italy. The method developed consists of 5 different phases and it involves also a normative-insulated reference wall. The results show higher insulation level of the proposed wall package, with a reduction of the heat flux of about 66% and more stable indoor thermal conditions, compared to the reference wall. Also the inertial properties are satisfactory, showing an experimental decrement factor equal to 0.05 and a time-shift of decrement factor higher than 6 h. All told, the experimental results can provide valuable insights into the real impact of innovative technology on energy efficiency and indoor thermal comfort.

Bisphenols in daily clothes from conventional and recycled material: evaluation of dermal exposure to potentially toxic substances

Given the increasing concern about chemical exposure from textiles, our study examines the risks of dermal exposure to bisphenol A (BPA), bisphenol S (BPS), bisphenol B (BPB) and bisphenol F (BPF) from conventional and recycled textiles for adults, aiming to obtain new data, assess exposure, and evaluate the impact of washing on bisphenol levels. A total of 57 textile samples (33 from recycled and 24 from conventional material) were subjected to ultrasound-assisted extraction (UAE) followed by ultra-high performance liquid chromatography with tandem mass spectrometry analysis (UHPLC-MS/MS). The BPA and BPS concentrations varied widely (BPA: < 0.050 to 625 ng/g, BPS: 0.277–2,474 ng/g). The median BPA content in recycled textiles (13.5 ng/g) was almost twice as high as that of 7.66 ng/g in conventional textiles. BPS showed a median of 1.85 ng/g in recycled textiles and 3.42 ng/g in conventional textiles, indicating a shift from BPA to BPS in manufacturing practices. Simulated laundry experiments showed an overall reduction in bisphenols concentrations after washing. The study also assessed potential health implications via dermal exposure to dry and sweat-wet textiles compared to a tolerable daily intake (TDI) of 0.2 ng/kg bw/day for BPA set by the European Food Safety Authority (EFSA). Exposure from dry textiles remained below this threshold, while exposure from wet textiles often exceeded it, indicating an increased risk under conditions that simulate sweating or humidity. By finding the widespread presence of bisphenols in textiles, our study emphasises the importance of being aware of the potential risks associated with recycling materials as well as the benefits.

Comparative Study of Cu Ion Adsorption by Nano-Hydroxyapatite Powder Synthesized from Chemical Reagents and Clam Shell-Derived Calcium Sources.

The increasing contamination of water sources by heavy metals necessitates the development of efficient and sustainable adsorption materials. This study evaluates the potential of nano-hydroxyapatite (HA) powders synthesized from chemical reagents (Chem-HA) and clam shells (Bio-HA) as adsorbents for Cu ions in aqueous solutions. Both powders were synthesized using microwave irradiation at 700 W for 5 min, resulting in nano-sized rod-like particles confirmed as HA by X-ray diffraction (XRD). Bio-HA exhibited higher crystallinity (67.5%) compared to Chem-HA (34.9%), which contributed to Bio-HA's superior adsorption performance. The maximum adsorption capacities were 436.8 mg/g for Bio-HA and 426.7 mg/g for Chem-HA, as determined by the Langmuir isotherm model. Kinetic studies showed that the Cu ion adsorption followed the pseudo-second-order model, with Bio-HA achieving equilibrium faster and displaying a higher rate constant (6.39 × 10⁻4 g/mg·min) than Chem-HA (5.16 × 10⁻4 g/mg·min). Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic, with Bio-HA requiring less energy (ΔH° = 39.00 kJ/mol) compared to Chem-HA (ΔH° = 43.77 kJ/mol). Additionally, the activation energy for Bio-HA was lower (41.62 kJ/mol) than that for Chem-HA (46.39 kJ/mol), suggesting better energy efficiency. The formation of a new Cu2(OH)PO4 phase after adsorption, as evidenced by XRD, confirmed that the Cu ions replaced the Ca ions in the HA lattice. These findings demonstrate that Bio-HA, derived from natural sources, offers environmental benefits as a recyclable material, enhancing heavy metal removal efficiency while contributing to sustainability by utilizing waste materials and reducing an environmental impact.

Ways to decarbonize the construction industry as a modern challenge for obtaining low-carbon building materials

The analysis of modern approaches and ideas for the production of new building composite materials with a low carbon footprint, including those obtained using recycled materials from man-made waste, is presented. It is concluded that the reduction of carbon dioxide emissions in the production of low-carbon concretes occurs as a result of replacing part of the cement with other types of binders or special fillers that ensure the preservation or improvement of the basic parameters of the structure of the building material, or due to technologies that reduce the clinker fraction of the binder while maintaining the specified properties of concrete. The leaders in the world practice in the field of low-carbon materials science are noted. The relevance of the development of the topic of environmental safety and sustainable development is indicated.

Green Building Certification in Educational Facility

Abstract This study evaluates energy saving in campus facilities toward green building certification by evaluating existing energy consumption, water consumption, and material usage. It supports the green building movement primarily from the education sector to respond to government regulations. The assessment was conducted through EDGE-App, an open-access building performance software developed by IFC, in the Integrated Creative Education Learning Laboratory (i–CELL) Building. EDGE-App calculates the energy savings in the building by comparing the difference between EDGE’s base case and the i-CELL building as the improved case. The variables calculated in this research are energy consumption, water conservation, and material recovery. This building performs 70% energy savings, 42% water savings, and 48% less embodied energy in materials—thus, it was granted an EDGE Advanced Green Building Certification. Furthermore, this study can inform engineers, designers, developers, and other parties about saving energy and optimizing water and recyclable materials in campus facilities.

Implementing life cycle thinking and climate change indicators in small and medium size enterprises

The policy for a low emission society requires that companies measure their impact from a life cycle perspective for both products and corporate reporting. This work presents new climate performance indicators to evaluate business models (BM) based on life cycle assessment (LCA) and benchmarked with statistics for Sustainable Development Goal indicator 9.4.1. The research was conducted by action case studies involving 20 small and medium sized enterprises (SMEs) from various sectors. The SMEs did not have previous experience with LCA. Therefore, a work process called “LCA á la carte” was designed to gradually increase details and effort. The results of simplified indicators on the manufacturing SMEs showed that the direct emissions to value added are lower than industry average. However, when upstream emissions and value added were included, the emission intensities are about industry average. The full life cycle climate indicators are presented for a boat production company that experiment with new BMs. Use phase electrification was found to be the most effective measure (60 % lower emission intensity), while material recycling and boat rental each reduced the emission intensity with about 30 %. However, a combination of these new BMs gives best results and could be needed to reach future benchmarks. This study suggests LCA for BM as a combination of a work process, actors' perspectives, and performance indicators. The results highlight that the scope of activities included in the performance indicators is crucial. New reporting standards such as the European Sustainable Development Standard (ESRS) should review the emission intensity indicators to ensure consistency between the scopes of activities included.

Toward low‐carbon cities: A review of circular economy integration in urban waste management and its impact on carbon emissions

AbstractUrban areas significantly contribute to global carbon emissions, necessitating a shift toward low‐carbon environments. The concept of low‐carbon cities presents a viable pathway for mitigating these anthropogenic emissions, particularly through solid waste management. This article explores the critical role of circular economy‐integrated waste management (CEWM) strategies in reducing carbon emissions and fostering sustainable urban development. We examine city‐level CEWM initiatives worldwide, assess the carbon emission quantification methods, and highlight specific CEWM strategies with significant carbon reduction potential. Our findings reveal that city‐level initiatives predominantly prioritize waste reduction and prevention (51%), followed by education and engagement (23%), material recycling and upcycling (21%), and waste conversion (6%). Key strategies such as composting, waste sorting, recycling, and biogas plants have demonstrated substantial potential in reducing carbon emissions. Integrating CE principles with waste management transforms the traditional linear take‐make‐dispose model into a circular approach that minimizes waste and maximizes resource efficiency. This integration is crucial for reducing carbon emissions and promoting a sustainable urban environment. A holistic perspective is required to plan and strategize for sustainable urbanization whereby CE and waste management are interconnected. CE principles provide an ideal foundation that enhances waste management strategies toward sustainability, ultimately leading to reduced carbon emissions. This article provides essential insights to equip decision‐makers with evidence‐based strategies for effective urban waste management.This article is categorized under: Climate and Environment &gt; Circular Economy Sustainable Development &gt; Goals

Cost-effective walnut shell biosorbent for efficient Cr(VI) removal from water: Batch adsorption and optimization using RSM-BBD

The conversion or recycling of waste materials into usable products is a sustainable and ecologically benign strategy, aligning with sustainable development and circular economy principles. This study presents a straightforward and cost-effective method for transforming walnut shells, commonly found in agricultural waste, into a biosorbent material highly effective in eliminating hexavalent chromium (Cr(VI)) from water. The prepared material underwent several analyses to determine its physical characteristics and surface chemistry, revealing an amorphous structure similar to lignocellulosic materials. Using Response Surface Methodology (RSM-BBD), we accurately forecasted and optimized the Cr(VI) adsorption process, evaluating and enhancing factors such as pH, biosorbent dosage, pollutant concentration, and adsorption time. Significant enhancement in the removal percentage (%R) was achieved, reaching 100 % after optimization. The RSM-BBD model provided high-quality prediction for data fitting (R² = 0.999). Various kinetic models, including PFO, PSO, and IPD models, were employed, with the PSO model providing the best depiction of adsorption. Equilibrium data analysis using the Langmuir, Freundlich, Redlich-Peterson and Temkin models revealed that the Freundlich model and R-P better fit the adsorption isotherm of Cr(VI) on treated walnut shell (WST). Furthermore, examination of Gibbs free energy and enthalpy indicated that the adsorption of Cr(VI) onto walnut shells is a spontaneous and exothermic reaction, resulting in the release of thermal energy.

AI-DRIVEN CIRCULARITY INDEX: A COMPREHENSIVE METRIC FOR EVALUATING PRODUCT LIFECYCLE SUSTAINABILITY

Sophisticated instruments are required for the analysis of sustainability in a product in all its complexity during a transition towards a circular economy. In this respect, the new metric presented in this article is the AI-driven Circularity Index, which assesses product circularity according to four dimensions: material selection, modular design, recyclability, and resource efficiency. This index-powered by machine learning - provides predictive insights and actionable recommendations toward product lifecycle sustainability, hence adding a more solid solution to the more pressing issues of traditional linear economic models.