Journal Description
Recycling
Recycling
is an international, peer-reviewed, open access journal on the recycling and reuse of material resources, including circular economy published bimonthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, ESCI (Web of Science), FSTA, Inspec, AGRIS, and other databases.
- Journal Rank: CiteScore - Q2 (Management, Monitoring, Policy and Law)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 20 days after submission; acceptance to publication is undertaken in 4.9 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Impact Factor:
4.3 (2022);
5-Year Impact Factor:
4.4 (2022)
Latest Articles
Effect of Recycled Concrete Aggregate Addition on the Asphalt Mixtures Performance: ITZ Area, Microstructure, and Chemical Analysis Perspectives
Recycling 2024, 9(3), 41; https://doi.org/10.3390/recycling9030041 (registering DOI) - 18 May 2024
Abstract
The importance of environmental consciousness and sustainability is increasing among transportation governing bodies worldwide. Many government bodies are concerned with maximizing the usage of recycled substances in road construction. Therefore, assessing the effect of recycled materials consumption is essential, mainly when designing new
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The importance of environmental consciousness and sustainability is increasing among transportation governing bodies worldwide. Many government bodies are concerned with maximizing the usage of recycled substances in road construction. Therefore, assessing the effect of recycled materials consumption is essential, mainly when designing new ‘green’ pavement types. The primary objective of this study is to investigate the impact of different treatments on improving the interfacial transition zone (ITZ) of coarse recycled concrete aggregate (CRCA) and its application in asphalt mixes. Such an aim is accomplished by enhancing its physical and mechanical characteristics, as well as its microstructure. The surface morphology, chemical composition, and intermix phases of the ITZ area and calcium silicate hydrate (CSH) compounds for CRCA were evaluated using scanning electron microscopy (SEM), an energy-dispersive X-ray analyzer (EDAX), and X-ray diffraction analysis (XRD). The performance of asphalt mixtures that included treated and untreated CRCA was also examined using different tests. It was found that heat treatment is an effective technique for enhancing the ITZ. However, cracks were seen in the mortar of CRCA when exposed to high temperatures (500 °C), which adversely affects the characteristics of the mortar. Acid treatment appeared to be an effective approach for improving the ITZ area. Nevertheless, the treatment that used acetic acid, a weak acid, was more effective than HCl acid, a strong acid. The outcomes revealed that the ITZ microstructure is significantly enhanced under different treatment types; however, microstructure improvements mainly included increased surface homogeneity and CSH compounds and a reduced Ca/Si ratio. It was also found that the asphalt mixtures with different proportions of untreated CRCA exhibited enhanced resistance to rutting. Furthermore, their tensile strength ratio (TSR) values were above the minimal level requirements. Moreover, the asphalt mixture with 30% CRCA, which was treated with various treatment methods, demonstrated a significant improvement in the mixtures’ mechanical properties; therefore, its application is highly successful and an environmentally friendly solution.
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(This article belongs to the Special Issue Sustainable Management in Eco-Materials, Industrial Residues and Construction and Demolition Waste)
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Open AccessSystematic Review
Valorizing Fruit and Vegetable Waste: The Untapped Potential for Entrepreneurship in Sub-Saharan Africa—A Systematic Review
by
Grace Okuthe
Recycling 2024, 9(3), 40; https://doi.org/10.3390/recycling9030040 - 17 May 2024
Abstract
Valorizing food waste (FW) in sub-Saharan Africa (SSA) can enhance the efficiency of limited resources, make healthy diets more affordable, and foster the creation of innovative enterprises. The vast quantities of FW from the agri-food chain significantly threaten food security. To address this
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Valorizing food waste (FW) in sub-Saharan Africa (SSA) can enhance the efficiency of limited resources, make healthy diets more affordable, and foster the creation of innovative enterprises. The vast quantities of FW from the agri-food chain significantly threaten food security. To address this issue and maximize potential environmental and socio-economic benefits, valorizing waste, a value-adding process for waste materials, has emerged as a sustainable and efficient strategy. Valorizing FW reduces greenhouse gas emissions, mitigates climate change, enhances resource efficiency, and improves planetary health. As a pivotal player in the transition toward the circular economy, this study investigates the potential of converting FW into value-added products, offering entrepreneurial opportunities for SSA’s unemployed youth. A systematic literature review is conducted to identify and filter relevant articles over five years by applying inclusion and exclusion criteria. A total of 33 articles were included for in-depth analysis to address the study’s aim. The findings highlight a range of value-added products derived from FW, including renewable energy sources, nutraceuticals, and heavy metal adsorbents. These products present promising entrepreneurial prospects within SSA. Nonetheless, overcoming barriers to FW valorization adoption is crucial for fully realizing its potential as a profitable business avenue.
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(This article belongs to the Special Issue Resource Recovery from Waste Biomass)
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Rapid Waste Motor Oil Conversion into Diesel-Range Hydrocarbons Using Hydrochar as Catalyst: Kinetic Study and Product Characterization
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Herman A. Murillo, Evelyn Juiña, Karla Vizuete, Alexis Debut, Daniel Echeverría, Sebastian Taco-Vasquez and Sebastian Ponce
Recycling 2024, 9(3), 39; https://doi.org/10.3390/recycling9030039 - 17 May 2024
Abstract
Herein, raw and alkali-treated hydrochars from biomass waste are prepared as a highly active catalyst for the conversion of waste motor oil into diesel-like fuels. Among all materials, hydrochar obtained at 250 °C and subsequent alkali activation with KOH showed a 600% improvement
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Herein, raw and alkali-treated hydrochars from biomass waste are prepared as a highly active catalyst for the conversion of waste motor oil into diesel-like fuels. Among all materials, hydrochar obtained at 250 °C and subsequent alkali activation with KOH showed a 600% improvement of the kinetic constant from 0.0088 to 0.0614 m−1. Conversion values at the same conditions were also improved from 66 to 80% regarding thermal and catalytic cracking, respectively. Moreover, the activation energy was also reduced from 293 to 246 kJ mol−1 for thermal and catalytic cracking, respectively. After characterization, the enhanced catalytic activity was correlated to an increased surface area and functionalization due to the alkali activation. Finally, the liquid product characterization demonstrated that catalytic cracking is more effective than thermal cracking for producing hydrocarbons in the diesel range. In particular, hydrochar-based catalysts are suggested to promote the formation of specific hydrocarbons so that the carbon distribution can be tailored by modifying the hydrothermal treatment temperature.
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(This article belongs to the Special Issue Resource Recovery from Waste Biomass)
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Green Valorization of Waste Plastics to Graphene as an Upcycled Eco-Friendly Material for Advanced Gas Sensing
by
Prince Oppong Amoh, Marwa Elkady, Mahmoud Nasr and Hassan Shokry
Recycling 2024, 9(3), 38; https://doi.org/10.3390/recycling9030038 - 13 May 2024
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The valorization technique successfully transformed waste polyethylene terephthalate (PET) into valuable carbon nanomaterial (CN)/graphene, while doped and undoped ZnO nanopowders were synthesized via sol–gel methods. Utilizing XRD, BET, TEM, EDX, FTIR, and TGA analyses, the synthesis of sp2 2D sheet, pristine, and
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The valorization technique successfully transformed waste polyethylene terephthalate (PET) into valuable carbon nanomaterial (CN)/graphene, while doped and undoped ZnO nanopowders were synthesized via sol–gel methods. Utilizing XRD, BET, TEM, EDX, FTIR, and TGA analyses, the synthesis of sp2 2D sheet, pristine, and doped ZnO nanostructures was confirmed. Solid-state gas sensor devices, tested under 51% relative humidity (RH), 30 °C ambient temperature, and 0.2 flow rate, exhibited a 3.4% enhanced response to H2 gas compared to CO2 at 50 ppm concentrations over time. Notably, the ZnO/CN sensor surpassed CN and ZnO alone, attributed to CN dopant integration with decreasing order of response performance as ZnO/CN > CN > ZnO. This study underscores the efficacy of valorization techniques in generating high-value carbon nanomaterials and their efficacy in bolstering gas sensor performance, with ZnO/CN demonstrating superior response capabilities.
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Open AccessReview
Recent Trends of Recycling and Upcycling of Polymers and Composites: A Comprehensive Review
by
Christina Podara, Stefania Termine, Maria Modestou, Dionisis Semitekolos, Christos Tsirogiannis, Melpo Karamitrou, Aikaterini-Flora Trompeta, Tatjana Kosanovic Milickovic and Costas Charitidis
Recycling 2024, 9(3), 37; https://doi.org/10.3390/recycling9030037 - 6 May 2024
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This review article gathers the most recent recycling technologies for thermoset and thermoplastic polymers. Results about existing experimental procedures and their effectiveness are presented. For thermoset polymers, the review focuses mainly on fibre-reinforced polymer composites, with an emphasis on epoxy-based systems and carbon/glass
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This review article gathers the most recent recycling technologies for thermoset and thermoplastic polymers. Results about existing experimental procedures and their effectiveness are presented. For thermoset polymers, the review focuses mainly on fibre-reinforced polymer composites, with an emphasis on epoxy-based systems and carbon/glass fibres as reinforcement, due to the environmental concerns of their end-of-life management. Thermal processes (fluidised bed, pyrolysis) and chemical processes (different types of solvolysis) are discussed. The most recent combined processes (microwave, steam, and ultrasonic assisted techniques) and extraordinary recycling attempts (electrochemical, biological, and with ionic liquids) are analysed. Mechanical recycling that leads to the downgrading of materials is excluded. Insights are also given for the upcycling methodologies that have been implemented until now for the reuse of fibres. As for thermoplastic polymers, the most state-of-the-art recycling approach for the most common polymer matrices is presented, together with the appropriate additivation for matrix upcycling. Mechanical, chemical, and enzymatic recycling processes are described, among others. The use of fibre-reinforced thermoplastic composites is quite new, and thus, the most recent achievements are presented. With all of the above information, this extensive review can serve as a guide for educational purposes, targeting students and technicians in polymers recycling.
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Recycling of Rhenium from Superalloys and Manganese from Spent Batteries to Produce Manganese(II) Perrhenate Dihydrate
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Katarzyna Leszczyńska-Sejda, Arkadiusz Palmowski, Michał Ochmański, Grzegorz Benke, Alicja Grzybek, Szymon Orda, Karolina Goc, Joanna Malarz and Dorota Kopyto
Recycling 2024, 9(3), 36; https://doi.org/10.3390/recycling9030036 - 30 Apr 2024
Abstract
This work presents the research results on the development of an innovative, hydrometallurgical technology for the production of manganese(II) perrhenate dihydrate from recycled waste. These wastes are scraps of Ni-based superalloys containing Re and scraps of Li–ion batteries containing Mn—specifically, solutions from the
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This work presents the research results on the development of an innovative, hydrometallurgical technology for the production of manganese(II) perrhenate dihydrate from recycled waste. These wastes are scraps of Ni-based superalloys containing Re and scraps of Li–ion batteries containing Mn—specifically, solutions from the leaching of black mass. This work presents the conditions for the production of Mn(ReO4)2·2H2O. Thus, to obtain Mn(ReO4)2·2H2O, manganese(II) oxide was used, precipitated from the solutions obtained after the leaching of black mass from Li–ion batteries scrap and purified from Cu, Fe and Al (pH = 5.2). MnO2 precipitation was carried out at a temperature < 50 °C for 30 min using a stoichiometric amount of KMnO4 in the presence of H2O2. MnO2 precipitated in this way was purified using a 20% H2SO4 solution and then H2O. Purified MnO2 was then added alternately with a 30% H2O2 solution to an aqueous HReO4 solution. The reaction was conducted at room temperature for 30 min to obtain a pH of 6–7. Mn(ReO4)2·2H2O precipitated by evaporating the solution to dryness was purified by recrystallization from H2O with the addition of H2O2 at least twice. Purified Mn(ReO4)2·2H2O was dried at a temperature of 100–110 °C. Using the described procedure, Mn(ReO4)2·2H2O was obtained with a purity of >99.0%. This technology is an example of the green transformation method, taking into account the 6R principles.
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(This article belongs to the Special Issue Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals)
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Considering Grouped or Individual Non-Methane Volatile Organic Compound Emissions in Life Cycle Assessment of Composting Using Three Life Cycle Impact Assessment Methods
by
Ben Joseph and Heinz Stichnothe
Recycling 2024, 9(3), 35; https://doi.org/10.3390/recycling9030035 - 29 Apr 2024
Abstract
Composting is a waste management practice that converts organic waste into a product that can be used safely and beneficially as a bio-fertiliser and soil amendment. Non-methane volatile organic compounds (NMVOCs) from composting are known to cause damage to human health and the
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Composting is a waste management practice that converts organic waste into a product that can be used safely and beneficially as a bio-fertiliser and soil amendment. Non-methane volatile organic compounds (NMVOCs) from composting are known to cause damage to human health and the environment. The impact of waste management on the environment and workers is recognised as a growing environmental and public health concern. Measurements of NMVOCs emitted during composting have been carried out only in a few studies. NMVOC emissions are typically reported as a group rather than as species or speciation profiles. Recognising the need to investigate the issues associated with NMVOCs, the objective of this study is to estimate variation in life cycle assessment (LCA) results when NMVOCs are considered individual emissions compared to grouped emissions and to compare midpoint and endpoint life cycle impact assessment (LCIA) methods. In general, the ReCiPe 2016 LCIA method estimated the highest impact from the composting process in comparison to IMPACT World+ and EF 3.0 for the impact categories of ozone formation, stratospheric ozone depletion, and particulate matter formation. For ReCiPe 2016 and IMPACT World+, the NMVOC emissions were not linked to human toxicity characterisation factors, meaning that the contribution from NMVOC towards human health risks in and around composting facilities could be underestimated. Using individual NMVOCs helps to additionally estimate the impacts of composting on freshwater ecotoxicity and human carcinogenic and non-carcinogenic toxicity potential. If ecotoxicity or toxicity issues are indicated, then LCA should be accompanied by suitable risk assessment measures for the respective life cycle stage.
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(This article belongs to the Special Issue Feature Papers in Recycling 2023)
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Recycling of Egyptian Shammi Corn Stalks for Maintaining Sustainable Cement Industry: Scoring on Sustainable Development Goals
by
Fajr Qasem, Mahmoud Sharaan, Manabu Fujii and Mahmoud Nasr
Recycling 2024, 9(3), 34; https://doi.org/10.3390/recycling9030034 - 26 Apr 2024
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This study focuses on recycling Shammi corn stalks in the cement industries, further avoiding air and soil pollution caused by their improper disposal. This crop residue was thermally treated at 700 °C for 2 h under an oxygen-rich environment to produce Shammi corn
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This study focuses on recycling Shammi corn stalks in the cement industries, further avoiding air and soil pollution caused by their improper disposal. This crop residue was thermally treated at 700 °C for 2 h under an oxygen-rich environment to produce Shammi corn stalk ash (SCSA). This SCSA was used as a cement replacement material (2–10%, w/w), whereas the control sample included only cement. The compressive strength values for the 4% (w/w) replacement ratio at 2-, 7-, and 28-day ages were greater than those for the control by 26.5%, 15.8%, and 11.4%, respectively. This 4% (w/w) also maintained a better flexural strength than other mixtures, with proper initial and final setting times (135 and 190 min), workability (18.5 cm), and water consistency (27.5%). These mechanical/physical properties were integrated with socio-enviro-economic data collected from experts through a pairwise comparison questionnaire, forming the inputs of a multi-criteria decision-making (MCDM) model. Recycling SCSA in the cement-manufacturing process attained positive scores in the achievement of the three pillars of sustainable development, revealing an overall score greater than the control. Hence, the study outcomes could be essential in developing green concrete, cement blocks, and mortar, based on the sustainable development goals (SDGs) agenda.
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Open AccessArticle
Evaluation of Thermoplastic Starch Contamination in the Mechanical Recycling of High-Density Polyethylene
by
Antonio Cascales, Cristina Pavon, Santiago Ferrandiz and Juan López-Martínez
Recycling 2024, 9(3), 33; https://doi.org/10.3390/recycling9030033 - 26 Apr 2024
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This research highlights the importance of addressing bioplastic contamination in recycling processes to ensure the quality of recycled material and move towards a more sustainable circular economy. Polyethylene (PE) is a conventional plastic commonly used in packaging for which large amounts of waste
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This research highlights the importance of addressing bioplastic contamination in recycling processes to ensure the quality of recycled material and move towards a more sustainable circular economy. Polyethylene (PE) is a conventional plastic commonly used in packaging for which large amounts of waste are produced; therefore, PE is generally recycled and has an established recycling process. However, the contamination of biodegradable polymers in the PE waste stream could impact recycling. This study, therefore, focuses on polyethylene (PE) that has been polluted with a commercial thermoplastic starch polymer (TPS), as both materials are used to produce plastic films and bags, so cross-contamination is very likely to occur in waste separation. To achieve this, recycled PE was blended with small quantities of the commercial TPS and processed through melt extrusion and injection molding, and it was further characterized. The results indicate that the PE-TPS blend lacks miscibility, evidenced by deteriorated microstructure and mechanical properties. In addition, the presence of the commercial TPS affects the thermal stability, oxidation, and color of the recycled PE.
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Open AccessArticle
Enhancing the Strength and the Environmental Performance of Concrete with Pre-Treated Crumb Rubber and Micro-Silica
by
M. R. Rajagopal, Jyothikumari Ganta and Yashwanth Pamu
Recycling 2024, 9(3), 32; https://doi.org/10.3390/recycling9030032 - 24 Apr 2024
Abstract
Dumped non-biodegradable tires present a significant environmental threat, with overflowing landfills and associated health risks highlighting the urgency of tire waste disposal. Current disposal methods, such as stacking tires in open spaces, exacerbate the problem. The large-scale recycling of tire rubber waste offers
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Dumped non-biodegradable tires present a significant environmental threat, with overflowing landfills and associated health risks highlighting the urgency of tire waste disposal. Current disposal methods, such as stacking tires in open spaces, exacerbate the problem. The large-scale recycling of tire rubber waste offers environmental benefits. This study examines the effects of pre-treatment using NaOH and micro-silica as a mineral admixture on the mechanical strength of crumb rubber concrete (CRC) with partial replacement of natural sand. Samples of M20 and M30 grade were prepared with varying levels of crumb rubber (CR) replacement and evaluated at 28 days. CRC prepared with pre-treated NaOH solution and micro-silica showed improved workability and strength compared to conventional concrete and untreated CRC, with the highest strength observed for 5% CR replacement using micro-silica. Predictive models and micro-structural analysis validated these findings. Life Cycle Assessment (LCA) using OpenLCA v2.10 software and the ecoinvent database revealed that incorporating micro-silica into CRC did not significantly increase environmental impacts, compared to conventional concrete across different mixes.
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(This article belongs to the Special Issue Recycling of Rubber Waste, 2nd Edition)
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Rural Urban Nutrient Partnership (RUN): Life Cycle Assessment of Multi Nutrient Recovery from Kitchen Waste and Blackwater
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Heinz Stichnothe, Ben Joseph, Volker Preyl and Carsten Meyer
Recycling 2024, 9(2), 31; https://doi.org/10.3390/recycling9020031 - 17 Apr 2024
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Newly developed and innovative RUN technology aims to recover nutrients from urban wastewater (blackwater) and biowaste (kitchen waste). The development of RUN technology has been supported by the life cycle assessment (LCA) in order to identify hotspots and trade-offs. While the performance of
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Newly developed and innovative RUN technology aims to recover nutrients from urban wastewater (blackwater) and biowaste (kitchen waste). The development of RUN technology has been supported by the life cycle assessment (LCA) in order to identify hotspots and trade-offs. While the performance of the process at a laboratory scale did not show any environmental benefits from P recovery, the LCA results have helped to improve the environmental performance at the following scale-up step. The recovery of P on a technical scale was environmentally beneficial, especially in terms of the global warming potential (GWP). However, there were still some trade-offs, e.g., freshwater and marine eutrophication were slightly higher compared to conventional P fertilizer production. Given that P is considered a critical raw material and that climate change is probably the most pressing environmental issue, RUN technology has the potential to deliver on both domains.
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(This article belongs to the Special Issue Reuse of Wastewater: Recovery of Water, Nutrients, and Energy—2nd Edition)
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An Overview of the Current Trends in Marine Plastic Litter Management for a Sustainable Development
by
Maria Râpă, Elfrida M. Cârstea, Anca A. Șăulean, Cristina L. Popa, Ecaterina Matei, Andra M. Predescu, Cristian Predescu, Simona I. Donțu and Alexandra G. Dincă
Recycling 2024, 9(2), 30; https://doi.org/10.3390/recycling9020030 - 9 Apr 2024
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This review summarizes recent data related to the management of marine plastic litter to promote sustainable development. It discusses the distribution and identification of marine plastic litter, assesses the potential socio-economic and environmental impacts of these pollutants, and explores their recovery strategies, from
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This review summarizes recent data related to the management of marine plastic litter to promote sustainable development. It discusses the distribution and identification of marine plastic litter, assesses the potential socio-economic and environmental impacts of these pollutants, and explores their recovery strategies, from a circular economy perspective. The main findings indicate that the majority of marine plastic litter originates from land-based sources. Current technologies and approaches for valorizing marine plastic litter include mechanical and chemical recycling, blockchain technologies by providing traceability, verification, efficiency and transparency throughout the recycling process, and public awareness programs and education. The developed policies to prevent marine plastic litter emphasize regulations and initiatives focused toward reducing plastic use and improving plastic waste management. By adopting a holistic and sustainable approach, it is possible to mitigate the environmental impact of marine plastic debris while simultaneously creating economic opportunities.
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Open AccessArticle
The Influence of a Commercial Few-Layer Graphene on the Photodegradation Resistance of a Waste Polyolefins Stream and Prime Polyolefin Blends
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S. M. Nourin Sultana, Emna Helal, Giovanna Gutiérrez, Eric David, Nima Moghimian and Nicole R. Demarquette
Recycling 2024, 9(2), 29; https://doi.org/10.3390/recycling9020029 - 9 Apr 2024
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This work investigated the photostabilizing role of a commercially available few-layer graphene (FLG) in mixed polyolefins waste stream (MPWS), ensuring extended lifespan for outdoor applications. The investigation was conducted by analyzing carbonyl content increase, surface appearance, and the retention of mechanical properties of
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This work investigated the photostabilizing role of a commercially available few-layer graphene (FLG) in mixed polyolefins waste stream (MPWS), ensuring extended lifespan for outdoor applications. The investigation was conducted by analyzing carbonyl content increase, surface appearance, and the retention of mechanical properties of UV-exposed MPWS/FLG composites. Despite the likely predegraded condition of MPWS, approximately 60%, 70%, 80%, and 90% of the original ductility was retained in composites containing 1, 4, 7, and 10 wt.% FLG, respectively. Conversely, just 20% of the original ductility was retained in unfilled MPWS. Additionally, less crack density and lower carbonyl concentrations of the composites also highlighted the photoprotection effect of FLG. For prime polyolefin blends, only 0.5 wt.% or 1 wt.% FLG was sufficient to preserve the original surface finishing and protect the mechanical properties from photodegradation. Hence, it was observed that MPWS requires more FLG than prime polyolefin blends to get to comparable property retention. This could be attributed to the poor dispersion of FLG in MPWS and inevitable uncertainties such as the presence of impurities, pre-degradation, and polydispersity associated with MPWS. This study outlines a potential approach to revalorize MPWS that possess a minimal intrinsic value and would otherwise be destined for landfill disposal.
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A Sustainable Solution with Improved Chemical Resilience Using Repurposed Glass Fibers for Sewage Rehabilitation Pipes
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Devanand Chelot, Shivnarain Ravichandran and Priyank Upadhyaya
Recycling 2024, 9(2), 28; https://doi.org/10.3390/recycling9020028 - 31 Mar 2024
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This paper introduces a sustainable sewage rehabilitation solution, utilizing repurposed glass fibers for enhanced chemical resilience and environmental conservation. The approach involves dividing a unitary pipe into segments, assembled during commissioning, aiming to reduce installation and transportation costs, particularly in less accessible areas.
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This paper introduces a sustainable sewage rehabilitation solution, utilizing repurposed glass fibers for enhanced chemical resilience and environmental conservation. The approach involves dividing a unitary pipe into segments, assembled during commissioning, aiming to reduce installation and transportation costs, particularly in less accessible areas. Each pipe segment comprises a multi-layered glass fiber composite sandwich, joined by an adhesive reinforced with recycled glass fibers. The glass fiber-reinforced plastic (GFRP) pipe features a core of blended sand impregnated with resin, an outer layer for impact resistance, and an inner layer to prevent corrosion. Chemical resilience is assessed through a 10,000 h strain corrosion study exposing both unitary and two-piece circular GFRP pipes to sulfuric acid in a deflected condition. An apparent hoop tensile test evaluates mechanical integrity before and after exposure. The experimental results reveal that the two-piece pipe with a tongue and groove joint (TGJ) with recycled glass fiber adhesive exhibits superior long-term bending stress and failure strain % compared to unitary pipes. This enhancement is attributed to the TGJ’s improved load-bearing capability and chemical resistance. The failure strain % of the two-piece pipe (1.697%) is higher compared to the unitary pipe (1.2613%). The long-term bending stress of the two-piece pipe obtained is 119.94 MPa whereas the unitary pipe reaches 93.48 MPa at the 50-year mark. The cost analysis supports the adoption of the two-piece pipe over unitary pipes due to a 40% reduction in carbon emissions and transportation cost. The novelty lies in the utilization of multi-piece pipes with enhanced chemical resilience, achieved through the incorporation of milled fiberglass reinforcements in the TGJ. Strain corrosion tests take a long time to perform; hence, an accelerated test is needed to improve the current recommended testing standard.
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(This article belongs to the Special Issue Sustainable Management in Eco-Materials, Industrial Residues and Construction and Demolition Waste)
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Blue Circular Economy—Reuse and Valorization of Bivalve Shells: The Case of Algarve, Portugal
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Fernanda Caroline Magalhães, Poliana Bellei, Inês Flores-Colen and Eduarda Marques da Costa
Recycling 2024, 9(2), 27; https://doi.org/10.3390/recycling9020027 - 30 Mar 2024
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The Circular Economy emerges as an alternative to reinvent the linear production model (take–make–waste), focusing on reintegrating waste into the production cycle, and aiming to minimize both environmental disposal and the unrestrained extraction of raw materials. In this context, the concept of Blue
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The Circular Economy emerges as an alternative to reinvent the linear production model (take–make–waste), focusing on reintegrating waste into the production cycle, and aiming to minimize both environmental disposal and the unrestrained extraction of raw materials. In this context, the concept of Blue Economy arises, an approach centered on preserving and valorizing marine and coastal resources. This article aims to develop a model for the circuit of bivalve shells, emphasizing the transformation of the residues into new products and identifying how these processes affect sociocultural, economic, and environmental dimensions. The methodology involved the surveying of local stakeholders directly involved in bivalve production and consumption to identify the relationship of these stakeholders with the production, marketing, and disposal of bivalves. It is concluded that biowaste has potential, and there is interest among local stakeholders in reusing it, but a lack of knowledge and connection among stakeholders ultimately leads to the devaluation of the product. The circuit of bivalves is necessary to identify value, propose correct collection, and stimulate interest in their reuse, both by other industries and by the aquaculture industry itself. Exploring the potential for reusing bivalves and mitigating their waste, as well as preventing improper disposal, could drive the development of the Blue Circular Economy in coastal regions.
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Open AccessArticle
Non-Structural Vibro-Compressed Concrete Incorporating Industrial Wastes
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Gabriela Bertazzi Pignotti, Ana Mafalda Matos and Fernanda Giannotti da Silva Ferreira
Recycling 2024, 9(2), 26; https://doi.org/10.3390/recycling9020026 - 25 Mar 2024
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This study presents more eco-efficient concrete formulations for precast vibro-compressed masonry blocks. The proposed formulations incorporated industrial waste, glass powder (GP), and quartz powder (QP), in which natural aggregate was partially replaced by QP (10%) and Portland cement by GP (10% and 20%).
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This study presents more eco-efficient concrete formulations for precast vibro-compressed masonry blocks. The proposed formulations incorporated industrial waste, glass powder (GP), and quartz powder (QP), in which natural aggregate was partially replaced by QP (10%) and Portland cement by GP (10% and 20%). The best combination of powder materials, water, and admixture was optimised at mortar level, considering a “zero slump” criteria and compressive strength. Afterwards, studies at concrete level followed. Specimens were vibrated and compressed in laboratory and immediately demoulded, aiming to simulate the industrial process. The compressive strength decreased when GP and QP were used alone; however, when combining 10% GP as cement replacement + 10% QP as fine aggregate replacement, the compressive strength increased by approximately 26.6% compared to the reference concrete. Water absorption results varied between 8.92 and 17.9%, and the lowest absorption was obtained by concrete specimens incorporating 20% GP. The UPV presented a narrow range of variation among all concrete mixtures under study, around 2–2.5 km/s at 28 days, whereas electrical resistivity was achieved at 28 days, at 20,000 and 25,000 ohms. Although there were some limitations of the casting process at the laboratory scale, the research results showed promising results, and it seems feasible to use this waste as a substitute for non-renewable raw materials in the production of concrete on an industrial scale. This can provide added value to abundant local wastes while contributing to a circular concrete economy.
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(This article belongs to the Special Issue Sustainable Management in Eco-Materials, Industrial Residues and Construction and Demolition Waste)
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Unlocking the Potential of Agrifood Waste for Sustainable Innovation in Agriculture
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Monica Voss, Carlotta Valle, Emanuela Calcio Gaudino, Silvia Tabasso, Claudio Forte and Giancarlo Cravotto
Recycling 2024, 9(2), 25; https://doi.org/10.3390/recycling9020025 - 20 Mar 2024
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The United Nations Environment Programme’s (UNEP’s) Food Waste Index Report 2021 highlights a global annual food waste of 1 billion tons. The UNEP plays a crucial role in achieving Sustainable Development Goal (SDG) 12.3, which aims to halve per capita global food waste
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The United Nations Environment Programme’s (UNEP’s) Food Waste Index Report 2021 highlights a global annual food waste of 1 billion tons. The UNEP plays a crucial role in achieving Sustainable Development Goal (SDG) 12.3, which aims to halve per capita global food waste (FW) at the retail and consumer levels and reduce food losses along production and supply chains globally by 2030. On the other hand, the agricultural sector faces the challenge of increasing productivity to feed the world’s growing population while reducing the environmental impact on ecosystems and human health. In this context, the conversion of agri-food waste (AFW) into biocides, bio-based fertilizers (BBFs) and biostimulants could represent a successful approach to tackle all these issues. This review shows the latest findings on the different sources of AFW and the application of their bioactive compounds in agriculture. Increasing crop yields and improving plant physiology through the utilization of AFW-derived value products aligns with a circular economy approach, bolstering people’s confidence in managing food waste for improved food production.
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Open AccessArticle
A Framework for Developing a National Research Strategy for Water Reuse
by
Arkalgud Ramaprasad and Thant Syn
Recycling 2024, 9(2), 24; https://doi.org/10.3390/recycling9020024 - 16 Mar 2024
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Water reuse is critical to national development, sustenance, and survival in this era of climate, demographic, and social changes. There is no systemic national approach to systematically addressing this challenge. This paper presents a framework and method to develop a national research strategy
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Water reuse is critical to national development, sustenance, and survival in this era of climate, demographic, and social changes. There is no systemic national approach to systematically addressing this challenge. This paper presents a framework and method to develop a national research strategy for water reuse. It presents an ontology of water reuse strategies that encapsulates the combinatorial complexity of the problem clearly, concisely, and comprehensively. Subsequently, it discusses the method to use the framework to develop a national strategy, adapt it through feedback and learning, and ultimately effect a revolutionary change in the strategy for water reuse.
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Open AccessArticle
A Comprehensive Performance Evaluation of GGBS-Based Geopolymer Concrete Activated by a Rice Husk Ash-Synthesised Sodium Silicate Solution and Sodium Hydroxide
by
Jonathan Oti, Blessing O. Adeleke, Prageeth R. Mudiyanselage and John Kinuthia
Recycling 2024, 9(2), 23; https://doi.org/10.3390/recycling9020023 - 14 Mar 2024
Abstract
Commercial sodium hydroxide (NaOH) and sodium silicate (SS) are commonly used as alkaline activators in geopolymer concrete production despite concerns about their availability and associated CO2 emissions. This study employs an alternative alkaline activator (AA) synthesized from a sodium silicate alternative (SSA)
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Commercial sodium hydroxide (NaOH) and sodium silicate (SS) are commonly used as alkaline activators in geopolymer concrete production despite concerns about their availability and associated CO2 emissions. This study employs an alternative alkaline activator (AA) synthesized from a sodium silicate alternative (SSA) solution derived from rice husk ash (RHA) and a 10 M sodium hydroxide solution. The initial phase established an optimal water-to-binder (W/B) ratio of 0.50, balancing workability and structural performance. Subsequent investigations explored the influence of the alkali/precursor (A/P) ratio on geopolymer concrete properties. A control mix uses ordinary Portland cement (OPC), while ground granulated blast-furnace slag (GGBS)-based geopolymer concrete—GPC mixes (GPC1, GPC2, GPC3, GPC4) vary the A/P ratios (0.2, 0.4, 0.6, 0.8) with a 1:1 ratio of sodium silicate to sodium hydroxide (SS: SH). The engineering performance was evaluated through a slump test, and unconfined compressive strength (UCS) and tensile splitting (TS) tests in accordance with the appropriate standards. The geopolymer mixes, excluding GPC3, offer suitable workability; UCS and TS, though lower than the control mix, peak at an A/P ratio of 0.4. Despite lower mechanical strength than OPC, geopolymers’ environmental benefits make them a valuable alternative. GPC2, with a 0.4 A/P ratio and 0.5 W/B (water to binder) ratio, is recommended for balanced workability and structural performance. Future research should focus on enhancing the mechanical properties of geopolymer concrete for sustainable, high-performance mixtures.
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(This article belongs to the Special Issue Sustainable Materials from Waste and Renewable Sources)
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Open AccessArticle
Measurements of the Permeability Coefficient of Waste Coal Ash under Hydrostatic Pressure to Identify the Feasibility of Its Use in Construction
by
Barbara Dutka, Katarzyna Godyń, Przemysław Skotniczny, Katarzyna Tokarczyk and Maciej Tram
Recycling 2024, 9(2), 22; https://doi.org/10.3390/recycling9020022 - 4 Mar 2024
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The aim of this research was to measure the filtration properties of waste coal ash under the influence of hydrostatic pressure generated in a three-axial compression apparatus. The scope of work included determining the compactibility parameters, maximum bulk density and optimal moisture content.
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The aim of this research was to measure the filtration properties of waste coal ash under the influence of hydrostatic pressure generated in a three-axial compression apparatus. The scope of work included determining the compactibility parameters, maximum bulk density and optimal moisture content. Permeability tests were performed for a sample with an average grain composition at three compaction indices : 0.964, 0.98 and 1.00. The hydrostatic pressure ranging from 0.5 to 1.8 bar corresponded to the layer depths from 2.17 to 7.83 m. Gradually increasing the pressure during the first loading cycle caused irreversible changes in the structure of the sample by local material agglomeration or grain interlocking. The water permeability coefficient was higher in the second loading cycle than in the first cycle. It was shown that waste coal ash cannot be used as a construction material on its own. To obtain constant filtration properties, the waste coal ash material should be doped, or an optimal compactionshould be used ( = 1.00). The results presented in this study are important for assessing the use of waste coal ash for construction engineering purposes.
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