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ISSN (Online) 2313-4321
Published by MDPI Homepage  [258 journals]
  • Recycling, Vol. 8, Pages 82: Investigation of the Fiber Length and the
           Mechanical Properties of Waste Recycled from Continuous Glass
           Fiber-Reinforced Polypropylene

    • Authors: Shiva MohammadKarimi, Benedikt Neitzel, Maximilian Lang, Florian Puch
      First page: 82
      Abstract: This paper explores the mechanical recycling of continuous fiber-reinforced thermoplastics (CFRTPs) waste into injection molded products, focusing on the influence of recycling parameters on fiber length and mechanical properties. CFRTPs are gaining attention for their promising attributes, including weight-specific mechanical properties, short cycle times, storability, and recyclability, making them suitable for diverse applications. However, as CFRTP production rates rise, recycling strategies become crucial for sustainability. This study investigates the processability of CFRTP waste, defines size reduction conditions, and evaluates the impact of various compounding parameters such as temperature, screw speed, and fiber volume content during extrusion. The research findings indicate that higher screw speeds lead to fiber length reduction, whereas elevated temperatures result in longer fibers. Increased fiber volume intensifies interactions, resulting in shorter lengths. Additionally, the study examines the influence of injection molding parameters such as back pressure, screw speed, and initial fiber length on the resulting fiber length and mechanical properties of injection molded specimens, emphasizing the need for precise parameter control to optimize performance in recycled CFRTPs. Key findings are that increasing the initial fiber length from 260 μm to 455 μm results in an average fiber length after injection molding of 225 μm and 341 μm, respectively. This implies that longer initial fibers are more prone to breakage. Regarding the mechanical properties, increasing back pressure from 20 bar to 60 bar results in a reduction in Young’s modulus of approximately 40 MPa. Higher screw speed also reduces modulus by approximately 70 MPa due to intensified fiber–screw interactions. However, back pressure and screw speed have neutral effects on the tensile strength and the elongation at break.
      Citation: Recycling
      PubDate: 2023-10-24
      DOI: 10.3390/recycling8060082
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 83: Alleviation of Selected Environmental Waste
           through Biodegradation by Black Soldier Fly (Hermetia illucens) Larvae: A

    • Authors: Sunarto Zulkifli, Anuraga Jayanegara, Bambang Pramudya, Melta Rini Fahmi, Mardiah Rahmadani
      First page: 83
      Abstract: Alleviation of environmental waste is a significant challenge, contributing to greenhouse gas emissions and wasting valuable resources. To address this issue sustainably, valorization techniques are being explored to convert environmental waste into valuable bio-based products. Additionally, the use of black soldier fly (Hermetia Illucens) larvae has emerged as a potential solution to degrade environmental waste and produce biomass. This study aimed to quantify the waste reduction index (WRI) of environmental waste through biodegradation by black soldier fly (BSF) larvae. A meta-analysis method was employed, involving a comprehensive search in the Scopus database for analysis. A total of 45 articles were analyzed and the results indicate that kitchen waste and fruit and vegetable wastes have a positive effect on WRI and other variables. The WRI of kitchen waste and fruit and vegetable wastes is 4.77 ± 2.98 g/day and 2.72 ± 2.14 g/day, respectively. Fecal waste results in a lower WRI than those of other waste categories, i.e., 2.22 ± 1.29 g/day. Overall, the BSF larvae effectively reduce organic environmental wastes and convert them into their body mass, which is rich in protein. This study contributes to a deeper understanding of the potential of BSF in waste management, offering insights into sustainable waste reduction strategies.
      Citation: Recycling
      PubDate: 2023-10-24
      DOI: 10.3390/recycling8060083
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 84: X-ray Fluorescence Analysis of Waste Sm-Co
           Magnets: A Rational Approach

    • Authors: Alexandra Alexandrovna Arkhipenko, Galina Evgenievna Marina, Marina Sergeevna Doronina, Natalya Alexandrovna Korotkova, Vasilisa Borisovna Baranovskaya
      First page: 84
      Abstract: Determination of the chemical composition of waste Sm-Co magnets is required for their efficient recycling. The non-stereotypical composition of said magnets makes an analysis extremely challenging. X-ray fluorescence spectrometry is a promising analytical tool for this task. It offers high accuracy and simplicity of sample preparation as it does not require sample dissolution. However, a serious limitation of X-ray fluorescence analysis is the spectral interference of matrix elements and impurities. In this work, a two-stage technique has been developed for the determination of the main components (Sm, Co) and impurities (Fe, Cu, Zr, Hf, Ti, Ni, Mn, Cr) in samples of spent samarium–cobalt magnets using wavelength dispersive X-ray fluorescence spectrometry. In order to overcome the main limitation of the chosen method and to maximize its capabilities of qualitative and quantitative analysis, we propose an approach to the selection of analytical lines and experimental conditions, as well as a preparation method for the calibration standards. The obtained results have been shown to have a good correlation with ICP-OES. The limits of detection are in the range of 0.001–0.02 wt%, and the limits of quantification are 0.003–0.08 wt%.
      Citation: Recycling
      PubDate: 2023-11-01
      DOI: 10.3390/recycling8060084
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 85: Gravity Concentration in Urban Mining
           Applications—A Review

    • Authors: Weslei M. Ambrós
      First page: 85
      Abstract: Urban mining has emerged as a concept that goes beyond conventional recycling, as it aims to tackle both the challenges of solid waste generation and management, as well as the scarcity of primary resources. Gravity concentration has gained increasing attention as a promising method for addressing crucial challenges in urban mining applications. In this sense, this review provides a comprehensive and up-to-date overview of gravity concentration in urban mining processes, covering principles, techniques, current applications, recent advancements, challenges, and opportunities. Emphasis was placed on shifting from the commonly found literature focus on ore processing to solid waste processing. Three types of solid waste, namely plastics, construction and demolition waste (CDW), and waste from electrical and electronic equipment (WEEE), were chosen for a more in-depth examination due to their massive production and widespread generation. Discussions also considered the potential of gravity concentration to address the unique challenges in their processing and explored possibilities for future developments.
      Citation: Recycling
      PubDate: 2023-11-01
      DOI: 10.3390/recycling8060085
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 86: A Systematic Literature Review of Waste
           Identification in Automatic Separation Systems

    • Authors: Juan Carlos Arbeláez-Estrada, Paola Vallejo, Jose Aguilar, Marta Silvia Tabares-Betancur, David Ríos-Zapata, Santiago Ruiz-Arenas, Elizabeth Rendón-Vélez
      First page: 86
      Abstract: Proper waste separation is essential for recycling. However, it can be challenging to identify waste materials accurately, especially in real-world settings. In this study, a systematic literature review (SLR) was carried out to identify the physical enablers (sensors and computing devices), datasets, and machine learning (ML) algorithms used for waste identification in indirect separation systems. This review analyzed 55 studies, following the Kitchenham guidelines. The SLR identified three levels of autonomy in waste segregation systems: full, moderate, and low. Edge computing devices are the most widely used for data processing (9 of 17 studies). Five types of sensors are used for waste identification: inductive, capacitive, image-based, sound-based, and weight-based sensors. Visible-image-based sensors are the most common in the literature. Single classification is the most popular dataset type (65%), followed by bounding box detection (22.5%). Convolutional neural networks (CNNs) are the most commonly used ML technique for waste identification (24 out of 26 articles). One of the main conclusions is that waste identification faces challenges with real-world complexity, limited data in datasets, and a lack of detailed waste categorization. Future work in waste identification should focus on deployment and testing in non-controlled environments, expanding system functionalities, and exploring sensor fusion.
      Citation: Recycling
      PubDate: 2023-11-02
      DOI: 10.3390/recycling8060086
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 87: Safety Assessment of Recycled Plastics from
           Post-Consumer Waste with a Combination of a Miniaturized Ames Test and
           Chromatographic Analysis

    • Authors: Elisa Mayrhofer, Lukas Prielinger, Victor Sharp, Bernhard Rainer, Christian Kirchnawy, Christian Rung, Anita Gruner, Mladen Juric, Arielle Springer
      First page: 87
      Abstract: European circular economy goals require the use of recycled polymers in sensitive applications such as food packaging. As plastic recyclates can contain unknown post-consumer substances, the European Food Safety Authority evaluates recycling processes using a worst-case assumption: all contaminants are DNA-reactive mutagens/carcinogens with extremely low safety thresholds. The current data are insufficient to estimate whether this assumption is justified. To provide scientific evidence on the presence of DNA-reactive mutagens in recycled plastics, 119 input and output samples from plastic recycling were tested with a miniaturized Ames test. DNA-reactive mutagens were not detected in recycled polyethylene terephthalate, which is already approved for food contact. However, other types of recycled plastics (polyethylene, polypropylene and polystyrene), which are currently unauthorized for food contact, showed DNA-reactive, mutagenic effects in a total of 51 samples. The DNA-reactive substances that are responsible for the detected mutagenic activity could not be identified by comparison of the bioassay data with analytical results from a chromatographical screening. The data from the Ames test analysis of different independent batches and a comparison of input and output material indicate that the DNA-reactive contaminants are not randomly introduced through the misuse of recycled packaging by consumers, but are systematically formed during the recycling process from precursors in the input. This publication highlights the need to identify the source for this critical contaminant to enable the future use of polyethylene, polypropylene and polystyrene in sensitive applications.
      Citation: Recycling
      PubDate: 2023-11-04
      DOI: 10.3390/recycling8060087
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 88: Recent Recycling Innovations to Facilitate
           Sustainable Packaging Materials: A Review

    • Authors: Idowu D. Ibrahim, Emmanuel R. Sadiku, Yskandar Hamam, Williams K. Kupolati, Julius M. Ndambuki, Tamba Jamiru, Azunna A. Eze, Jacques Snyman
      First page: 88
      Abstract: Packaging materials play a significant role in the meat, fish, and seafood, pharmaceutical, beverages, and electronics industries. These materials protect the contents during handling and transportation from damage, contamination, and loss of quality, thus enhancing the shelf life of the products being packaged. Several materials, like paper and cardboard, plastics, metals, and glass, have been widely used. However, the vast consumption of these materials leads to high waste generation due to increasing demands globally. This article considers some aspects of recycling waste packaging materials, the need for recycling in terms of environmental impacts, and the energy-saving and economic benefits. It also provides some highlights on the sustainability of the processes of recycling and how the government and public can influence recycling operations. The impact of the COVID-19 pandemic on packaging systems and solid waste management is also highlighted. This study also provides a short note on the possible future methods to be adopted in the recycling process of waste packaging materials.
      Citation: Recycling
      PubDate: 2023-11-07
      DOI: 10.3390/recycling8060088
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 89: Automated Battery
           Disassembly—Examination of the Product- and Process-Related
           Challenges for Automotive Traction Batteries

    • Authors: Domenic Klohs, Christian Offermanns, Heiner Heimes, Achim Kampker
      First page: 89
      Abstract: As the market share of electric vehicles continues to rise, the number of battery systems that are retired after their service life in the vehicle will also increase. This large growth in battery returns will also have a noticeable impact on processes such as battery disassembly. The purpose of this paper is, therefore, to examine the challenges of the battery disassembly process in relation to the required increase in the degree of automation. For this purpose, a survey of various experts along the battery value chain was conducted, and product-side hurdles, such as the wide range of variants, and process-side challenges, such as the opening of the housing cover or the removal of cables and connectors, were identified. Together with an assessment of the potential degree of automation in the context of downstream processes (reuse, repair, remanufacturing, and recycling), this results in a variety of streams for future research in the field of automated battery disassembly. The core aspect in this context is data availability consisting of product and component data as well as process-relevant parameters.
      Citation: Recycling
      PubDate: 2023-11-08
      DOI: 10.3390/recycling8060089
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 90: An Overview of Management Status and
           Recycling Strategies for Plastic Packaging Waste in China

    • Authors: Chaojie Yu, Diyi Jin, Xichao Hu, Wenzhi He, Guangming Li
      First page: 90
      Abstract: Given their exceptional performance, plastic packaging products are widely used in daily life, and the dramatic expansion in plastic packaging waste (PPW) has exacerbated environmental problems. Many countries have enacted laws and developed recycling technologies to manage plastic packaging waste in consideration of the nature of PPW as both garbage and a resource. As the world’s largest producer and consumer of plastics, China has also taken measures to address this issue. This paper presents the latest management regulations and recycling strategies for PPW in China. Based on an analysis of the current management status of PPW and recycling technologies and their carbon emission impacts, some management suggestions and a comprehensive full-chain recycling process were put forward. We supposed that management challenges that need to be overcome in the future can be solved through the improvement of green designs for plastic packaging, manufacturing technology updates, consumption concept changes, and the high-value utilization of PPW. This paper aims to provide valuable references for government decisions on PPW management and, furthermore, to set up an economically sensible and industrially feasible PPW solution and boost the development of PPW recycling.
      Citation: Recycling
      PubDate: 2023-11-11
      DOI: 10.3390/recycling8060090
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 91: Exploring the 5Rs Holistic Model for Zero
           Food Waste in Saudi Arabian Food Service Outlets

    • Authors: Abu Elnasr E. Sobaih, Ahmed E. Abu Elnasr
      First page: 91
      Abstract: Background: The proportion of food waste in the Kingdom of Saudi Arabia, particularly in food service outlets, sends an important and urgent call for a holistic model to either prevent or at least properly manage this high level of food waste. This study draws on the European Union Waste Hierarchy Framework and the United States Environmental Protection Agency Food Recovery Framework to develop a holistic model to manage the high rate of food waste in Saudi food service outlets. Methods: This study adopted the Standards for Reporting Qualitative Research using one-to-one interviews with food service experts to explore the current and appropriate practices for food waste prevention. The in-depth interviews discussed the implementation of the 5Rs hierarchy, which includes reducing food surplus and waste at the source, redistributing food surplus to needy people, reusing food surplus/waste, recycling food waste, and recovering food waste benefits, i.e., bioenergy production. Results: The successful implementation of the 5Rs hierarchy depends on effective collaboration between the key stakeholders, i.e., policy makers, food industry administrators, non-governmental organizations, and customers. The effective management of the food supply chain is also vital to avoid food surplus and prevent waste in food service outlets. Additionally, sustainable production by staff and responsible consumption by consumers contribute effectively to the implementation of the 5Rs model, which contributes to the achievement of zero food waste and, ultimately, to sustainable development. Conclusions: This study provided a novel hierarchy model, which has five tiers, aiming to avoid food waste. The successful implementation of this model will lead to several significant positive impacts on the economy, community, and environment.
      Citation: Recycling
      PubDate: 2023-11-11
      DOI: 10.3390/recycling8060091
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 92: Recovery of Kish Graphite from Steelmaking
           Byproducts with a Multi-Stage Froth Flotation Process

    • Authors: Ying-Liang Chen, Wei-Ping Chiang, Ping-Yu Hsieh
      First page: 92
      Abstract: Steelmaking processes inevitably generate large amounts of byproducts, including slags, specks of dust, etc., and their treatment has been a critical issue for the steelmaking industry. Kish graphite is a valuable substance existing in steelmaking byproducts, and the recovery of Kish graphite has attracted more attention in recent years. The purpose of this study was to use a multi-stage froth flotation process for the beneficiation of Kish graphite and to investigate the influence of flotation conditions on the mass distribution of graphite and impurities. The results showed that the dust D2 contained ~34 wt.% of graphite and thus had the highest potential for the recovery of Kish graphite. The dosages of frother (methyl isobutyl carbinol, MIBC) at 0.005 kg/t and collector (kerosene) at 1 kg/t were optimal for the flotation of Kish graphite. After three-stage froth flotation, the graphite content of the concentrate was progressively increased to 84.09 wt.%, and the entire recovery rate was 93.05%. During the multi-stage froth flotation process, most of the impurities were separated in stage I, but the Fe-containing impurities were mainly separated in stage II. Some Ca2+, Na+, and K+ were leached out, and there were barely any heavy metals in the liquid phases.
      Citation: Recycling
      PubDate: 2023-11-18
      DOI: 10.3390/recycling8060092
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 93: Recycled Surgical Mask Waste as a Resource
           Material in Sustainable Geopolymer Bricks

    • Authors: Kritish Thoudam, Nabil Hossiney, Srinidhi Lakshmish Kumar, Jacob Alex, Sanoop Prakasan, Sarath Chandra, Yogeshraj Urs, A. S. Arunkumar
      First page: 93
      Abstract: With the advent of the COVID-19 pandemic, the global consumption of single-use surgical masks has risen immensely, and it is expected to grow in the coming years. Simultaneously, the disposal of surgical masks in the environment has caused plastic pollution, and therefore, it is exigent to find innovative ways to handle this problem. In this study, surgical masks were processed in a laboratory using the mechanical grinding method to obtain recycled surgical masks (RSM). The RSM was added in doses of 0%, 1%, 2%, 3%, and 4% by volume of geopolymer bricks, which were synthesized with ground granulated blast furnace slag (GGBS), rice husk ash (RHA), sand, and sodium silicate (Na2SiO3) at ambient conditions for a duration of 28 days. The developed bricks were tested for compressive strength, flexural strength, density, water absorption, efflorescence, and drying shrinkage. The results of the study reveal that compressive strength and flexural strength improved with the inclusion of RSM in the bricks. The highest values of compressive strength and flexural strength were 5.97 MPa and 1.62 MPa for bricks with 4% RSM, respectively. Further, a reduction in the self-weight of the bricks was noticed with an increase in RSM. There was no pronounced effect of RSM on the water absorption and efflorescence properties. However, the RSM played a role in reducing the drying shrinkage of the bricks. The sustainability analysis divulges the catalytic role of RSM in improving material performance, thereby proving to be a potential candidate for low-carbon material in the construction industry.
      Citation: Recycling
      PubDate: 2023-11-19
      DOI: 10.3390/recycling8060093
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 94: Exploring the Plastic Collection and
           Recycling Trends in Sri Lanka

    • Authors: Rohantha Rukshan Jayasinghe, Wasudha Prabodhani Abeyrathna, Krishani Rukmali Jayasingha, Manuja Promodya Hendawitharana, Thusitha Saman Bandara, Champika L. Liyanage, Karl S. Williams
      First page: 94
      Abstract: This study examined plastic waste management in Sri Lanka, concentrating on the contributing factors to plastic waste generation and collection. Data were gathered through a questionnaire survey from registered plastic recycling and management centres. The analysis revealed a positive correlation between tourist arrivals and plastic waste generation, indicating increased plastic waste production due to tourism spanning from 2014 to 2022. However, plastic waste collection negatively correlated with precipitation levels, suggesting heavy rainfall hampers collection efforts. This study found HDPE, PVC, LDPE, and PP to be the most collected and recycled plastic types, whereas PS and PET recycling were less prevalent. The results demonstrate the need for enhanced recycling infrastructure and highlight the necessity for government participation in plastic waste management initiatives. This study recommends increasing waste collection and recycling during the tourist season. In addition to enhancing public and private awareness, there should be additional investment in recycling facilities. The findings offer crucial insights into plastic waste management in Sri Lanka, emphasizing the importance of collaborative efforts and comprehensive strategies to tackle plastic pollution.
      Citation: Recycling
      PubDate: 2023-11-26
      DOI: 10.3390/recycling8060094
      Issue No: Vol. 8, No. 6 (2023)
  • Recycling, Vol. 8, Pages 65: Study of the Effect of Modification of
           Asphalt on the Rheological Properties Employing Microwave
           Radiation—An Aging Study

    • Authors: Khalid Ahmed Owaid, Raghed Y. Ghazal, M. A. Avdelzaher
      First page: 65
      Abstract: This study focuses on producing asphalt with improved rheological properties that differ from the original asphalt and are less affected by aging conditions. The rheological properties of Qayara asphalt were enhanced by modifying the asphalt using spent rubber tire (SRT) with different percentages of anhydrous aluminum chloride. Percentages ranging from 1.0% by weight of the spent tire rubber were added after proceeding with the thermal crushing process. The percentages of anhydrous aluminum chloride catalyst were 0.4 and 0.8%, respectively. This mixture was microwaved at 270 watt of power for 4, 8, and 12 min, respectively. The measurements performed are plasticity, penetration, softening point, and penetration index. The previously mentioned measurements were also made on the modified asphalt one year after the modification process to understand the effect of aging conditions. The microstructure and thermodynamics have been characterized by FE-SEM and EDX measurements. This study provides good rheological properties of the modified bitumen binder that is aging-resistant.
      Citation: Recycling
      PubDate: 2023-08-26
      DOI: 10.3390/recycling8050065
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 66: Assessing Greenhouse Gas Emissions and Energy
           Efficiency of Four Treatment Methods for Sustainable Food Waste Management

    • Authors: Xiaoming Liu, Si Li, Wenhao Chen, Huizhou Yuan, Yiguan Ma, Muhammad Ahmar Siddiqui, Asad Iqbal
      First page: 66
      Abstract: Food waste (FW) increases with urbanization and population growth, which puts pressure on the treatment system, causing a variety of harmful impacts on the environment. Proper FW treatment is imperative for ecological integrity and public health. Even though FW treatment is an extensively studied topic, the sustainable FW treatment considering holistic-lifecycle-based environmental impacts has rarely been evaluated. This study addresses this gap through a comprehensive analysis of various FW treatment methods, including co-treatment with sewage, anaerobic digestion, incineration, and aerobic composting. The impacts of greenhouse gas (GHG) emission and energy use efficiency are assessed by analyzing diverse FW treatment methods in Shenzhen, China. The study indicates that FW addition to sewage does not adversely affect the current sewage treatment plant, but benefits GHG avoidance and energy recovery. Compared with the other FW treatment methods, FW anaerobic digestion avoids the most GHG emissions with −71.3 kg CO2 eq/FU and recovers the most energy with −223 kWh/FU, followed by FW co-treated with sewage. The energy conversion efficiency of the combined heat and power (CHP) unit greatly affects FW incineration, while energy consumption in incineration and anaerobic digestion (AD) process is relatively minor. Perturbation analysis pinpoints key parameters influencing outcomes, including CHP efficiency, GHG emission factor of local electricity, and chemical oxygen demand (COD) in FW with ratios of −13~−0.942, −0.518~0.22, and −13~1.01, respectively, that should be given special attention. This study sheds light on sustainable FW management strategies, not only in China but also transferrable to regions confronting similar challenges. Advocating ecologically balanced and resource-efficient approaches, the study aligns with broader aims of fostering sustainable development.
      Citation: Recycling
      PubDate: 2023-08-27
      DOI: 10.3390/recycling8050066
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 67: Properties of High-Flowability Liquefied
           Stabilized Soil Made of Recycled Construction Sludge

    • Authors: Yuji Shigematsu, Shinya Inazumi, Susit Chaiprakaikeow, Supakij Nontananandh
      First page: 67
      Abstract: This paper focuses on the development of high-flowability liquefied stabilized soils (HFLSS) made of recycled construction sludge (RCS) to enhance their application in construction work. Liquefied stabilized soils (LSSs) have already found widespread use in construction sites, particularly for filling long-distance structures and dealing with complex underground spaces. However, to further optimize their performance, the development of high-flowability liquefied stabilized soils (HFLSSs) with superior flowability is required. This study experimentally investigates the basic properties, including mechanical characteristics and flowability performance, of the newly developed HFLSS made of RCS. The results confirm that the developed HFLSS made of RCS meets the quality requirements expected from LSSs and exhibits enhanced flowability, making it a promising material for construction applications. The advanced development of LSSs in this paper expects to promote recycling construction-generated soils, including construction-generated sludges in the construction industry.
      Citation: Recycling
      PubDate: 2023-08-30
      DOI: 10.3390/recycling8050067
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 68: Bacterial Treatment of Recycled Concrete

    • Authors: Austen Rowell, Tewodros Ghebrab, Randall Jeter
      First page: 68
      Abstract: Microbial treatment of recycled concrete aggregate (RCA) may improve the quality of the aggregate, and enhance its use in the production of structural concrete and promote the recycling of concrete waste. The mortar phase of the RCA is responsible for the poor performance of the aggregate. Treating the old adhered mortar or removing it from the natural aggregate (NA) is an option to make RCA beneficial for the production of quality recycled aggregate concrete (RAC). Removing the adhered mortar from recycled concrete aggregate using silicate-solubilizing bacteria was investigated. The bacteria could synthesize the silicates in the calcium silicate hydrate phase of the cement paste leading to the breakdown of the old adhered mortar. Four SSB strains were tested for survivability and activity in an alkaline medium to simulate the concrete environment. The Serratia marcescens bacterial strain, which survived the environment, was inoculated into screw-cap glass vials containing recycled concrete aggregate fragments and glucose-enhanced nutrient broth and then incubated for 14 days. Partial removal of the old adhered mortar was observed based on the weight lost from the RCA. The S. marcescens bacterial strain could survive the alkaline concrete environment and solubilize the silicates present in cement paste resulting in the removal of the old adhered mortar.
      Citation: Recycling
      PubDate: 2023-09-09
      DOI: 10.3390/recycling8050068
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 69: Circularity Outlines in the Construction and
           Demolition Waste Management: A Literature Review

    • Authors: Izabella-Eva Gherman, Elena-Simina Lakatos, Sorin Dan Clinci, Florin Lungu, Vladut Vasile Constandoiu, Lucian Ionel Cioca, Elena Cristina Rada
      First page: 69
      Abstract: This study provides a comprehensive view of the research field of construction and demolition waste (CDW) management in the circular economy based on a literature review. The increased intensity of interest is due to the need to create frameworks, mechanisms, and tools for the process of mind-shifting towards circularity. Research topics, researched life cycle stages, strategies for CDW management, sustainability assessment, building stock quantification, assessment tools and forecast methods, materials with CDW content, waste treatment solutions, and the barriers and drivers for efficient waste management in the construction industry are identified as the main concerns in the analyzed research field. The results show that a major concern in the academic field directs research to the path of innovative strategy elaboration, identifying the enablers and barriers in CDW management, computational tool creation for design and assessment, building stock modeling, and circular building material development. The environmental approach prevails, leaving economic and social assessments in CDW management uncovered. Although stakeholders’ involvement is stressed in most cases, strategies for awareness-raising and education for a sustainable circular activity in the field are lacking. The circularity of CDW management being a multifaceted and multi-disciplinary complex challenge, it is approached on different levels. This study introduces the novelty of structuring the trends of existing knowledge in a holistic view, identifying the research directions, dimensions, specific aspects, and instruments.
      Citation: Recycling
      PubDate: 2023-09-11
      DOI: 10.3390/recycling8050069
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 70: Application of TIMES for Bioresource Flow
           Optimization—Case Study of Animal Husbandry in Latvia, Europe

    • Authors: Ketija Bumbiere, Maksims Feofilovs, Pauls Asaris, Dagnija Blumberga
      First page: 70
      Abstract: As an integral part of the EU’s Green Deal, the purpose of the bioeconomy is to ensure an effective transition to meet people’s needs based on renewable resources while maintaining economic growth. This study undertakes the modeling of bioresource value scenarios in the agricultural sector and proposes a methodology to evaluate the possibilities of reaching a higher added value of bioresource products. The main objective of the study is the adaptation of the market allocation–energy flow optimization model system (TIMES) for analysis of high-value-added product production capacities in the livestock sector to reach an increase in added value for 2030 with the introduction of new technologies. The developed model is tested in a case study of the animal husbandry sector in Latvia. The results show which pathways are economically feasible to achieve value-added targets set for 2030. Although not all of the available resources are used due to local market limitations, there is significant potential for the use of animal husbandry resource waste, and it is possible to achieve about 62% higher cumulative added value from 2023 to 2030 with the production of new products (protein powder, wool pellets, and gelatin) in comparison with the base scenario.
      Citation: Recycling
      PubDate: 2023-09-12
      DOI: 10.3390/recycling8050070
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 71: The Challenge of Plastic Management for Waste
           Electrical and Electric Equipment Recycling in the Global South: A Case
           Comparison between Europe and Latin America

    • Authors: Cecilia Chaine, Andrew S. Hursthouse, Iain McLellan, Evi Viza, Jan Miller
      First page: 71
      Abstract: Countries with emerging legislation on the waste electrical and electric equipment (WEEE), but limited infrastructure, may find in other, more robust, systems the tools to develop adaptable and socioeconomically viable management schemes. Additives found in the plastics in electronic goods, such as brominated flame retardants (BFRs), are components of a safety system, but introduce characteristics that result in their waste being hazardous. Established and emerging regulatory systems need to implement legislation that impacts the management of WEEE, to reduce risks to human health and the environment, while maximising opportunities for resource recovery from widely varying materials. To assess the context of developed and emerging regulatory systems, a baseline study was undertaken of WEEE plastics in Scotland and Uruguay. For the identification of BFRs in plastics, an internationally validated screening methodology using X-ray fluorescence was adopted at different processing operations. It was observed that, using a threshold of 830 mg/kg for Br as a BFR tracer, in Scotland, more than 70% of the plastics would be recyclable, while, in Uruguay, that fraction dropped to 50%. These results, and the wider literature discussion, highlight the impact that regulatory frameworks have on the quality and recyclability of recovered material. We identify future actions to be considered by policy-makers for a more sustainable regulatory approach.
      Citation: Recycling
      PubDate: 2023-09-15
      DOI: 10.3390/recycling8050071
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 72: An Experimental Approach to Determining the
           Average Diffusion Coefficient of Volatile Components in Polymer Waste

    • Authors: Chi Nghia Chung, Christian Marschik, Jakub Klimosek, Juraj Kosek, Mohamad Hassan Akhras, Georg Steinbichler
      First page: 72
      Abstract: One of the major challenges in recycling plastics is the removal of undesired volatile components from the polymeric phase, which may reduce process efficiency and negatively affect product quality. Accordingly, the recycling industry employs a broad range of degassing techniques, the efficiency of which often depends on the diffusion coefficient—a measure of the mass transport of volatile components in polymeric phases. The aim of this study was to develop a practically feasible experimental approach using thermogravimetric analysis (TGA) to determine the average diffusion coefficient of volatile components in polymer waste materials. First, the TGA method was validated with a pressure decay apparatus (PDA) using predefined binary material mixtures: Thin sheets were pressed from virgin high-density polyethylene (HDPE) and polypropylene (PP) and deliberately saturated with toluene in a sorption experiment. These saturated samples were then used in TGA and PDA desorption experiments at 60 °C, 80 °C and 100 °C, which yielded similar results with an average difference of 7.4% for the HDPE-toluene system and 14.7% for the PP-toluene system. When validated, TGA was employed to determine the diffusion coefficient of volatile components in post-industrial plastic waste melt at a temperature of 220 °C. The proposed method contributes to the understanding of diffusion-based mass transport in polymer waste materials and provides a key parameter for model-based process control and optimization. In practice, the diffusion coefficient results can be used to predict the degassing performance of an extrusion process in the mechanical recycling of plastic waste.
      Citation: Recycling
      PubDate: 2023-09-21
      DOI: 10.3390/recycling8050072
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 73: Combining SWOT with AHP for Analyzing the
           Adoption of a Circular Economy in the Apparel Industry in Brazil

    • Authors: Rimena Canuto Oliveira, Irenilza de Alencar Nääs, Solimar Garcia
      First page: 73
      Abstract: The Brazilian fashion industry is the country’s second-largest generator of direct and indirect jobs. Despite Brazilian design being a world reference mainly for prints and summer-related collections, it is also the second most polluting industry in the country. We investigated the factors that impact adopting a circular economy in the textile industry using an association of a SWOT analysis and the AHP approach. We analyzed the adoption of a circular economy in the apparel industry. The opportunities, strengths, weaknesses, and threats were associated using the evaluators’ comparison of the selected SWOT items related to the application of a circular economy in the conventional apparel industry were used as criteria for the AHP approach. The case study used managers from two intimate apparel industries in northeastern Brazil and four academics in Production Engineering. By applying the concepts to the case study, we found that expanding products, upcycling, and increasing sustainability were the three vital criteria for reaching a circular economy in the studied apparel industry.
      Citation: Recycling
      PubDate: 2023-09-22
      DOI: 10.3390/recycling8050073
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 74: Comparative Study of Adsorption of Methylene
           Blue and Basic Red 9 Using Rice Husks of Different Origins

    • Authors: Hadid Sukmana, Etelka Tombácz, Gergő Ballai, Gábor Kozma, Zoltán Kónya, Cecilia Hodúr
      First page: 74
      Abstract: Methylene blue (MB) and basic red 9 (BR9) are cationic dyes that are commonly used in the dye industry and negatively affect humans and other living organisms. This study compares the performance of Indonesian rice husk (IRH) and Hungarian rice husk (HRH) as bio-adsorbents for removing MB and BR9 from aqueous solutions. Chemical content, zeta potential, and Fourier-transform infrared spectroscopy analyses were used to characterize the rice husks (RHs). Adsorption studies were performed through batch experiments involving several parameters, namely, pH, adsorbent dose, initial dye concentration, contact time, and temperature to observe the self-association (aggregation) of MB and BR9. Adsorption kinetic studies showed that maximum dye removal was achieved at a contact time of 120 min. MB and BR9 adsorption followed a pseudo-second order kinetic model, and the BET multilayer isotherm model provided a better fit to the experimental data of MB and BR9 adsorption. The IRH adsorption capacities were 15.0 mg/g for MB and 7.2 mg/g for BR9, whereas those of HRH were 24.4 mg/g for MB and 8.3 mg/g for BR9. Therefore, these RHs are potential bio-adsorbents for removing MB and BR9 from aqueous solutions.
      Citation: Recycling
      PubDate: 2023-09-27
      DOI: 10.3390/recycling8050074
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 75: Application Potential of Wastewater
           Fertigated Short Rotation Coppice Systems in a Selected Region (Aligarh,
           UP, India)

    • Authors: Mirko Hänel, Ganbaatar Khurelbaatar, Emil Jespersen, Aryan Upadhyay, Andrés Acosta, Nadeem Khalil, Hans Brix, Carlos A. Arias
      First page: 75
      Abstract: In many Indian regions, increased wastewater is both a threat to public health and the environment, but it also presents an opportunity as a source of water and nutrients. With less than one-third of India’s wastewater treated and an alarming water scarcity situation, efficient wastewater treatment and reuse schemes are needed to face impending water and fertiliser shortages. This study explores the application potential of wastewater fertigated Short Rotation Coppice systems (wfSRC) as a cost-efficient and promising solution for treating and reusing wastewater in a specific region (400 km2, 184 settlements) of Aligarh (UP), India. Based on real data from a local wfSRC pilot site using bamboo, willow, and poplar, we analysed the system’s treatment performance, nutrient recovery, carbon sequestration potential, land requirements, biomass production potential, and cost–benefit, under various scenarios. The results show that the pilot wfSRC system is efficiently treating 250 m3/day of domestic wastewater on 6864 m2 of land, and serving 2500 people. The land requirements for wfSRC systems vary depending on local conditions (e.g., climate, soil type, wastewater composition) and user demands (e.g., water reuse efficiency, type, and amount of biomass). The calculated areas ranged from 2.75 to 25.7 m2/PE, which equates to a required land area in the whole study region of between 108 and 1006 ha in 2036. This would produce up to 100 DM t/ha/year of valuable biomass. Early local stakeholder involvement and the monitoring of pollutants are recommended as priorities during the planning process for the large-scale implementation of wfSRC systems in India.
      Citation: Recycling
      PubDate: 2023-09-29
      DOI: 10.3390/recycling8050075
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 76: Building a Deposit–Refund System (DRS)
           for Closed-Loop Recycling of Water Bottles in the United Arab Emirates

    • Authors: Wisam Abu Jadayil, Eman Aqil
      First page: 76
      Abstract: Water bottles are widely used in the Gulf countries. One estimate indicates that the water bottle usage in the United Arab Emirates (UAE) may reach up to 250 L of water per person annually. Generally, the water bottles are made of polyethylene terephthalate (PET), a recyclable material. Because of the non-availability of a powerful incentive system, these recyclable water bottles are often disposed of in landfills. This paper proposes a feasibility study of building a Deposit–Refund System (DRS) to encourage the closed-loop recycling of 0.5 L PET water bottles in the UAE waste disposal system. Water bottles are collected by a reverse vending machine (RVM) and recycled to produce PET bottles, and the proposed system will reward consumers with 0.04 United Arab Emirates Dirham (AED) per deposited water bottle. Additionally, this study calculates the cost of 100% virgin polyethylene terephthalate (vPET) and 60% recycled polyethylene terephthalate (rPET) bottles based on the UAE population, data obtained from local water bottle companies, and existing research. Adopting this DRS will cut down on waste, protect the environment, improve the manufacturing process of water bottles, and boost the local economy.
      Citation: Recycling
      PubDate: 2023-10-03
      DOI: 10.3390/recycling8050076
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 77: Experimental Study on the Thermal
           Conductivity of Three Natural Insulators for Industrial Fishing

    • Authors: Laura Leinad Lobo-Ramos, Yulibeth Carolina Osorio-Oyola, Alvaro Espeleta-Maya, Francisco Narvaez-Montaño, Shirley Patricia García-Navarro, Luis Alfonso Moreno-Pacheco, Ricardo Andrés García-León
      First page: 77
      Abstract: Ecological materials have been implemented in different industrial sectors due to their good performance as thermal insulators and the fact that they are 100% natural, recyclable, and biodegradable, contributing to environmental sustainability. The main objective of this article is to compare the thermal conductivity coefficients of three natural insulators with that of expanded polystyrene (a non-biodegradable material). Expanded polystyrene is one of the materials which is most often used to maintain cold temperatures in containers built for this purpose in the fishing industry; it is used for this purpose because of its properties, including a light weight and a high thermal insulation capacity and resistance. Almost all insulators have the ecological disadvantage of being environmentally unfriendly materials because they are made up of oil particles, which are not recyclable and are harmful to ecosystems. The natural insulator materials were evaluated and subjected to a drying process to reduce the humidity coefficient; then, the containers were built with an adequate insulation thickness of 25 mm. Three filling tests were carried out (at 100, 70, and 50%) to evaluate the thermal conductivity, using the Mann–Whitney U statistical analysis process to determine insulator differences. The results show that the expanded polystyrene had the lowest thermal conductivity of 0.032 W/m K, followed by the rice husk, which had a value of 0.036 W/m K. Finally, a comparative study of conservation costs was carried out in the different containers built with the natural insulators; the lowest value found was for the expanded polystyrene (COP 159.57 around USD 0.040). This allowed to conclude that rice husk is the material that comes closest to the insulating characteristics of expanded polystyrene.
      Citation: Recycling
      PubDate: 2023-10-06
      DOI: 10.3390/recycling8050077
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 78: Closing the Loop on LIB Waste: A Comparison
           of the Current Challenges and Opportunities for the U.S. and Australia
           towards a Sustainable Energy Future

    • Authors: Gavin E. Collis, Qiang Dai, Joanne S. C. Loh, Albert Lipson, Linda Gaines, Yanyan Zhao, Jeffrey Spangenberger
      First page: 78
      Abstract: Many countries have started their transition to a net-zero economy. Lithium-ion batteries (LIBs) play an ever-increasing role towards this transition as a rechargeable energy storage medium. Initially, LIBs were developed for consumer electronics and portable devices but have seen dramatic growth in their use in electric vehicles (EVs) and via the gradual uptake in battery energy storage systems (BESSs) over the last decade. As such, critical metals (Li, Co, Ni, and Mn) and chemicals (polymers, electrolytes, Cu, Al, PVDF, LiPF6, LiBF4, and graphite) needed for LIBs are currently in great demand and are susceptible to global supply shortages. Dramatic increases in raw material prices, coupled with predicted exponential growth in global demand (e.g., United States graphite demand from 2022 7000 t to ~145,000 t), means that LIBs will not be sustainable if only sourced from raw materials. LIBs degrade over time. When their performance can no longer meet the requirement of their intended application (e.g., EVs in the 8–12 year range), opportunities exist to extract and recover battery materials for re-use in new batteries or to supply other industrial chemical sectors. This paper compares the challenges, barriers, opportunities, and successes of the United States of America and Australia as they transition to renewable energy storage and develop a battery supply chain to support a circular economy around LIBs.
      Citation: Recycling
      PubDate: 2023-10-07
      DOI: 10.3390/recycling8050078
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 79: Recovery of Graphite from Spent Lithium-Ion

    • Authors: Charlotte Badenhorst, Iwona Kuzniarska-Biernacka, Alexandra Guedes, Elsayed Mousa, Violeta Ramos, Gavin Rollinson, Guozhu Ye, Bruno Valentim
      First page: 79
      Abstract: Critical raw materials, such as graphite and lithium metal oxides (LMOs), with a high supply risk and high economic importance are present in spent lithium-ion batteries (LIBs). The recovery and recycling of these critical raw materials from LIBs will contribute to the circular economy model, reduce the environmental footprint associated with the mining of these materials, and lower their high supply risk. The main aim of this paper is to present a separation process to recover graphite from black mass (BM) from spent LIB. Simultaneously, LMO and copper (Cu) and aluminum (Al) foils were also recovered as by-products from the process. The process used a combination of simple and/or low environmental footprint technologies, such as sieving, sink-float, citric acid leaching, and milling through ultrasound and soft attrition, to allow separation of the LIB valuable components. Three graphite-rich products (with purities ranging between 74 and 88 wt.% total carbon and a combined yield of 14 wt.%) with three different sizes (<25 µm, <45 µm, and <75 µm), Cu and Al foil fragments, and an LMO-rich precipitate product are delivered. The developed process is simple, using low temperatures and weak acids, and using affordable and scalable equipment available in the market. Its advantage over other LIB recycling processes is that it can be implemented, so to speak, “in your backyard”.
      Citation: Recycling
      PubDate: 2023-10-08
      DOI: 10.3390/recycling8050079
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 80: Precious Metal Recovery from Waste Electrical
           and Electronic Equipment through Oxidative Refining

    • Authors: Eunmi Park, Minji Kim, Min-Wook Pin, Hyunsik Park, Yong-Hwan Kim
      First page: 80
      Abstract: This study delves into the application of oxidative refining for the recovery and concentration of precious metals, namely palladium (Pd) and gold (Au), from waste electrical and electronic equipment by WEEE recycling, leveraging pyrometallurgical techniques. The primary objective is to optimize refining parameters, encompassing variations in gas pressure, temperature, and gas composition, to maximize the extraction and purification of precious metals from recycled materials. Through an array of comprehensive characterization techniques, encompassing microstructural analysis, elemental composition assessment, and metal concentration measurement, this study scrutinizes the potential of oxidative refining. The conclusive findings underscore the remarkable potential of oxidative refining in augmenting the efficiency and effectiveness of metal recovery from waste printed circuit boards (PCBs), with a pronounced emphasis on the concentration of Pd and Au. This research not only highlights the promise of oxidative refining but also concludes that optimizing process parameters, such as a N2/O2 mixed gas pressure of 4 L/min, a process time of 40 min, and a temperature of 1400 °C, is imperative for achieving the highest efficiency in metal recovery from electronic waste, especially precious metals like Pd and Au. It further contributes to the sustainable management of electronic waste and the strategic extraction of valuable precious metals.
      Citation: Recycling
      PubDate: 2023-10-16
      DOI: 10.3390/recycling8050080
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 81: Avocado Waste Biorefinery: Towards
           Sustainable Development

    • Authors: Teresa Sandoval-Contreras, Fernando González Chávez, Amrita Poonia, Maricarmen Iñiguez-Moreno, Lizet Aguirre-Güitrón
      First page: 81
      Abstract: The increasing demand for avocado consumption has led to a vast generation of waste products. Despite the high nutritional value of avocados, the waste generated from their processing poses a significant environmental challenge. Therefore, the development of a sustainable approach to avocado waste management is a major concern. Biorefinery presents a promising approach to the valorization of avocado waste components, including the seed, peel, and pulp residues. This paper explores the potential of avocado waste biorefinery as a sustainable solution to produce bio-based products. Several approaches, including extraction, hydrolysis, fermentation, and biodegradation, to obtain valuable products such as starch, oil, fiber, and bioactive compounds for food or feed goods have been proposed. The review also highlights the approaches towards addressing challenges of energy security and climate change by utilizing avocado waste as a source to produce biofuels such as biogas, biodiesel, and bioethanol. In conclusion, the development of avocado waste biorefinery presents a promising avenue for sustainable development. This process can efficiently convert the avocado waste components into valuable bio-based products and clean energy sources, contributing to the attainment of a circular economy and a more sustainable future.
      Citation: Recycling
      PubDate: 2023-10-20
      DOI: 10.3390/recycling8050081
      Issue No: Vol. 8, No. 5 (2023)
  • Recycling, Vol. 8, Pages 53: Carbon-Based Synthesized Materials for CO2
           Adsorption and Conversion: Its Potential for Carbon Recycling

    • Authors: Tuan-Dung Hoang, Suhaib A. Bandh, Fayaz A. Malla, Irteza Qayoom, Shahnaz Bashir, Suhail Bashir Peer, Anthony Halog
      First page: 53
      Abstract: During the last half-century, the CO2 concentration in the world’s atmosphere has increased from 310 p.p.m. to over 380 p.p.m. This is due to the widespread usage of fossil fuels as a main source of energy. Modeling forecasts have shown that this trend will continue to rise and reducing CO2 emissions is a challenging task for multi-stakeholders, including research institutions. The UN Climate Change Conference in Glasgow (COP26) has stressed that stakeholders need to work together to achieve a NetZero target. Technologies involving absorbents for the capture of CO2 from a gas mixture are energy-intensive. Carbon adsorption and conversion (CAC) approaches have been gaining attention recently since these technologies can mitigate CO2 emissions. In this review, materials ranging from advanced carbon-based materials to natural resources-based materials will be reviewed. Adsorption and conversion capacities as well as the scalability possibility of these technologies for solving the CO2 emission problem will be investigated. The review, therefore, is timely and meaningful concerning the net zero emission targets set by countries and developmental organizations worldwide.
      Citation: Recycling
      PubDate: 2023-06-21
      DOI: 10.3390/recycling8040053
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 54: Recycled Construction and Demolition Waste as
           Supplementary Cementing Materials in Eco-Friendly Concrete

    • Authors: Silvina V. Zito, Edgardo F. Irassar, Viviana F. Rahhal
      First page: 54
      Abstract: Growing environmental awareness and scarcity of natural resources are forcing the world to migrate from linear to circular economies. The possibility of partially replacing cement with ceramic-based waste from construction and demolition waste (C&DW) is a government and industry focus. The present study analyzes the effects of including finely ground complete walls of ceramic blocks (including masonry mortars) as supplementary cementing materials (SCM) on the physical, mechanical, and transport properties (water absorption and permeability) of concrete. The replacement ratio employed was 25% by weight of cement. Studies of the hydration evolution of cement pastes support the described properties of concretes. The findings reveal that the ground ceramic-based waste from C&DW stimulates hydration at all ages. Initially, this stimulation is predominantly physical (filler effect), but in later stages, it becomes chemical (pozzolanic reaction). Based on the results obtained in this study, it is possible to produce concrete with mechanical properties comparable to those of conventional concrete at 28 days.
      Citation: Recycling
      PubDate: 2023-06-28
      DOI: 10.3390/recycling8040054
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 55: The Impact of Industry 4.0 on the Steel
           Sector: Paving the Way for a Disruptive Digital and Ecological

    • Authors: Laura Tolettini, Eleonora Di Maria
      First page: 55
      Abstract: Since the creation of a common term to indicate a set of incremental and disruptive digital technologies, Industry 4.0 has challenged European manufacturers to find a way to concretely exploit these innovations in their own business strategy. During this journey, Industry 4.0 has recently highlighted some evidence about its efficacy in enabling strategic goals on the three dimensions (economical, environmental, social) of sustainable development, which is a key element for the European Union’s goal to make manufacturers become carbon neutral until 2030. Industry 4.0 and sustainability are together affecting manufacturers’ business models, forcing managers to take chances and face challenges within their organization and in their supply-chain. As an energy-intensive sector, steel industries will be intensively affected by sustainability paradigms. With 19 qualitative interviews in the organization and supply chain of an internationalized steel producer, Feralpi Group, we provide evidence that, beyond the use of main strategic technologies (Internet of Things and Big Data analysis), the implementation of a sustainability strategy is also possible through the creation of new partnerships beyond the own supply chain. The combination of Industry 4.0 technologies and sustainability strategies, especially concerning the environment through Circular Economy practices, pushes steel industries to revise their business models, paving the way for unexpected collaborations, where suppliers, customers, and even more diverse stakeholders such as competitors could bring benefits to the company sustainable economic growth and durability.
      Citation: Recycling
      PubDate: 2023-06-28
      DOI: 10.3390/recycling8040055
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 56: Sustainable Waste Management for Clean and
           Safe Environments in the Recreation and Tourism Sector: A Case Study of
           Lithuania, Turkey and Morocco

    • Authors: Dalia Perkumienė, Ahmet Atalay, Larbi Safaa, Jurgita Grigienė
      First page: 56
      Abstract: Due to intensive tourism and increasing demand for recreational activities, people produce more waste. In this context, the aim of this research is to determine the opinions of experts working in tourism and recreation areas in Lithuania, Turkey and Morocco with respect to waste management problems. Interviews were held in Turkey, Lithuania and Morocco in order to determine the attitudes of experts about recreational activities with respect to a clean environment and sustainability. A semistructured interview form was used for interviews with forest operators and other experts. The sample group consisted of 24 experts from Turkey, Lithuania and Morocco. The prominent results of the interviews conducted in the three countries regarding waste and sustainable waste management can be listed as follows: intensive waste production caused by participants, inadequate legal regulation, insufficient recycling, damage to the environment and natural structures, inadequate control and inspections, lack of education and awareness activities, an insufficient number of personnel and insufficient infrastructure. Sustainable waste management strategies, such as reducing waste generation, improving waste collection and disposal methods, and promoting recycling and composting, can help to mitigate these negative impacts.
      Citation: Recycling
      PubDate: 2023-06-28
      DOI: 10.3390/recycling8040056
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 57: Evaluation of Biogas Energy from Co-Digestion
           of Organic Urban Solid Waste with Lime Mud

    • Authors: Ulisses Raad da Silva Coelho, Adriele Maria de Cássia Crispim, Maria Auxiliadora de Barros Martins, Regina Mambeli Barros, Maria Luiza Grillo Reno, Geraldo Lúcio Tiago Filho, Ivan Felipe Silva Santos
      First page: 57
      Abstract: The elevated presence of organic material in Brazilian urban solid waste, along with mismanagement of its disposal, can aggravate environmental problems from greenhouse gas emissions to water and soil pollution. In parallel, the paper and cellulose industries consume considerable resources and produce important solid wastes, including lime mud. These urban and industrial realities present common ground, from which a little-studied alternative arises in using biogas electrical energy from the co-digestion of the organic portion of urban solid waste using lime mud. This intersection can reduce the environmental impacts associated with inadequate management and disposal of solid waste, providing industry financial economy resources and contributing to Brazilian energy grid diversification. The current study used economic–financial indicators to evaluate the proposal’s economic feasibility. The obtained results presented a minimum population of 165,200 inhabitants, generating 39,295.77 m3/year of methane, in order to enable a co-digestion proposal. The sensitivity analysis indicated that a population of 185,500 inhabitants would provide a 10-year payback, an energy rate of USD 0.139, and 44,124.49 m3/year of methane to supply the population with power. The net present value was USD 23,336.94, with an internal return rate of 14.71% and a levelized energy cost of 0.103 USD/kWh.
      Citation: Recycling
      PubDate: 2023-07-01
      DOI: 10.3390/recycling8040057
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 58: Assessing the Measurement Model for
           Source-Separating Waste for Recycling under a Proposed Smart Waste
           Management Scheme in Shah Alam, Malaysia

    • Authors: Abdullatif Bazrbachi, Shaufique Fahmi Sidique, Shehu Usman Adam, Normaz Wana bt Ismail, Tey Yeong Sheng
      First page: 58
      Abstract: Due to rapid urbanization, solid waste management (SWM) is a major challenge in Malaysia, hence the need to sustainably manage it. Compared with other states, Selangor produces the highest volume of domestic waste. Most of the state’s waste is generated in Shah Alam City. This condition is expected to worsen because the population of Shah Alam is projected to rise by 2.5% from 2018 to 2035. This situation will increase the demand for resources, production, and consumption, increasing the volume of waste generated in Shah Alam. Hence, the pressing necessity to advance from the current traditional waste management practices to a more sustainable SWM system has been identified as a key target in Shah Alam’s 2025–2030 plans. The Smart Waste Management System (SWMS) has been identified as a novel approach to dealing with the absence of route optimization, real-time information exchange, and the consequent increase in waste management costs. All of these elements have characterized the current traditional households’ SWM. However, because this method is novel, there is a dearth of knowledge on the appropriate measurement model for evaluating the dimension of households’ intention to recycle waste through source separation as well as measuring the determinants of such a pro-environmental intention under the new SWMS. Thus, confirmatory factor analysis (CFA) was carried out to verify the factorial structure of the variables, relying on the Theory of Planned Behavior (TPB) based on the structural dimensions identified in prior exploratory factor analysis (EFA). The study found support for the use of TPB as a relevant framework for modeling the intention for source separation and its determinants under SWMS.
      Citation: Recycling
      PubDate: 2023-07-07
      DOI: 10.3390/recycling8040058
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 59: The Recycling of End-of-Life Lithium-Ion
           Batteries and the Phase Characterisation of Black Mass

    • Authors: Laurance Donnelly, Duncan Pirrie, Matthew Power, Ian Corfe, Jukka Kuva, Sari Lukkari, Yann Lahaye, Xuan Liu, Quentin Dehaine, Ester M. Jolis, Alan Butcher
      First page: 59
      Abstract: Black mass is the industry term applied to end-of-life (EoL) lithium-ion batteries that have been mechanically processed for potential use as a recycled material to recover the valuable metals present, including cobalt, lithium, manganese, nickel and copper. A significant challenge to the effective processing of black mass is the complexity of the feed material. Two samples of black mass from a European source were analysed using a combination of methods including automated SEM-EDS (AMICS) to characterise and quantify the phases present and particle chemistry. Micro X-CT imaging, overlain onto automated mineralogy images, enabled the 3D morphology of the particles to be determined. Micro-XRF was used to map the copper, nickel, manganese and cobalt-bearing phases. Since Li cannot be detected using SEM-EDS, its abundance was semi-quantified using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The integration of these complimentary analytical methods allowed for detailed phase characterisation, which may guide the potential hydrometallurgical or pyrometallurgical recycling routes and chemical assaying.
      Citation: Recycling
      PubDate: 2023-07-12
      DOI: 10.3390/recycling8040059
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 60: Special Issue “Feature Papers in
           Recycling 2022”

    • Authors: Francesco Paolo La Mantia, Beatrice Castellani
      First page: 60
      Abstract: This Special Issue aimed to collect high-quality papers (original research articles or comprehensive review papers) published during 2022 on the subject of waste recycling [...]
      Citation: Recycling
      PubDate: 2023-07-13
      DOI: 10.3390/recycling8040060
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 61: Lignocellulosic Agricultural Waste
           Valorization to Obtain Valuable Products: An Overview

    • Authors: Alessandro Blasi, Alessandra Verardi, Catia Giovanna Lopresto, Sarah Siciliano, Paola Sangiorgio
      First page: 61
      Abstract: The sustainable management of lignocellulosic agricultural waste has gained significant attention due to its potential for the production of valuable products. This paper provides an extensive overview of the valorization strategies employed to convert lignocellulosic agricultural waste into economically and environmentally valuable products. The manuscript examines the conversion routes employed for the production of valuable products from lignocellulosic agricultural waste. These include the production of biofuels, such as bioethanol and biodiesel, via biochemical and thermochemical processes. Additionally, the synthesis of platform chemicals, such as furfural, levulinic acid, and xylose, is explored, which serve as building blocks for the manufacturing of polymers, resins, and other high-value chemicals. Moreover, this overview highlights the potential of lignocellulosic agricultural waste in generating bio-based materials, including bio-based composites, bio-based plastics, and bio-based adsorbents. The utilization of lignocellulosic waste as feedstock for the production of enzymes, organic acids, and bioactive compounds is also discussed. The challenges and opportunities associated with lignocellulosic agricultural waste valorization are addressed, encompassing technological, economic, and environmental aspects. Overall, this paper provides a comprehensive overview of the valorization potential of lignocellulosic agricultural waste, highlighting its significance in transitioning towards a sustainable and circular bioeconomy. The insights presented here aim to inspire further research and development in the field of lignocellulosic waste valorization, fostering innovative approaches and promoting the utilization of this abundant resource for the production of valuable products.
      Citation: Recycling
      PubDate: 2023-07-20
      DOI: 10.3390/recycling8040061
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 62: Recycling of Polypropylene Recovered from a
           Composting Plant: Mechanical Behavior of Compounds with Virgin Plastic

    • Authors: Claudio Badini, Oxana Ostrovskaya, Giulia Bernagozzi, Roberta Lanfranco, Stefania Miranda
      First page: 62
      Abstract: The recycling of polypropylene recovered from waste discarded by a composting plant was investigated. The recovery involved a sorting step carried out by means of an optical infrared separator and a subsequent washing treatment. This method of processing allowed us to obtain polypropylene that was only slightly contaminated by other polymeric and inorganic materials. As many tens of tons of polypropylene could be recovered every year in this plant, recycling could be convenient from the economic point of view and beneficial for the protection of the environment. In fact, the landfill of this waste could be reduced in this manner. A possible mechanical recycling route was developed for the recovered plastic. The recycling was carried out by pelletizing the recovered polypropylene, mixing it with a commercial polypropylene feedstock, and manufacturing items by injection molding. In this way, tensile specimens containing different amounts of recycled polypropylene were processed and tested. Their tensile features were compared with those of a commercial polypropylene that was used as a reference. The elastic modulus and tensile strength were slightly worsened when using the recycled plastic, while the strain at failure significantly increased. Nonetheless, the tensile properties of compounds made by mixing recycled and virgin polypropylene were consistent with the characteristics that are expected for polypropylene-based plastics.
      Citation: Recycling
      PubDate: 2023-07-31
      DOI: 10.3390/recycling8040062
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 63: Catalytic Pyrolysis of Waste Low-Density

    • Authors: Krishna Prasad Rajan, Ibrahim Mustafa, Aravinthan Gopanna, Selvin P. Thomas
      First page: 63
      Abstract: The present investigation reports the results of experiments related to the conversion of low-density polyethylene (LDPE) waste carry bags to fuel through an economic catalytic pyrolysis method in a batch reactor using zinc oxide (ZnO) as the catalyst. Plastics are highly beneficial for the day-to-day activities of human beings; however, their decomposition is limited due to their strong covalent bonding. Degradation of these big molecules into smaller ones or monomers has been attempted by several researchers in recent decades, with limited success. Pyrolysis is one of the ideas used to convert plastics, with the crowded structure of polymers, into fuel rather than small molecules. Among these plastics, LDPE is widely used as carry bags throughout the world, and, herein, the results of catalytic pyrolysis of the conversion of LDPE into fuel are reported. A compact laboratory-scale batch reactor, specially designed at our laboratory, was used to carry out the pyrolysis process. Different dosages of ZnO were used as a catalyst to carry out the pyrolysis at a specific temperature. The optimal dosage of ZnO for a 50 g waste LDPE batch was found to be 0.6 g to get the maximum oil yield. The yielded oil was analyzed chemically through Fourier transform infrared spectroscopy (FTIR) and a Reformulyzer M4 Hydrocarbon Group Type Analyzer. Evaluation of physical and chemical exergy along with exergetic efficiency of the process was carried out. The described experiments and the results represent a small but significant step toward curbing the menace of plastic solid wastes, which are degrading the environment and human life worryingly, and allowing them to be utilized for generating low-cost fuel for transportation and other applications.
      Citation: Recycling
      PubDate: 2023-08-16
      DOI: 10.3390/recycling8040063
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 64: Assessment of Three Recycling Pathways for
           Waste Cooking Oil as Feedstock in the Production of Biodiesel,
           Biolubricant, and Biosurfactant: A Multi-Criteria Decision Analysis

    • Authors: Giovanni De Feo, Carmen Ferrara, Luana Giordano, Libero Sesti Ossèo
      First page: 64
      Abstract: The management of waste cooking oil (WCO) often poses significant challenges. The improper disposal of WCO results in negative environmental impacts and economic losses. However, from a circular economy perspective, WCO can be recycled and used as a sustainable feedstock for numerous industrial products, replacing virgin vegetable oils. This approach enables the recovery of resources while simultaneously addressing the problem of WCO disposal. By employing a multi-criteria decision analysis (MCDA) approach, the study assesses three alternative recycling pathways for WCO used as a feedstock in the production of (A1) biodiesel, (A2) biolubricant, and (A3) biosurfactant. The aim is to identify the optimal alternative, taking into account environmental, economic, and technical factors. The procedure involved a team of chemical engineers working in the WCO recycling sector who were selected as decision makers. The ‘priority scale’ combined with the Paired Comparison Technique was employed as a weighting method to evaluate the selected criteria. The results revealed that the decision makers considered environmental sustainability as the most crucial evaluation criterion, followed by the economic criterion. In contrast, the aspect of process management was deemed less significant. Among the compared alternatives, utilizing WCO as a feedstock for biosurfactant production was assessed as the optimal WCO recycling solution. This alternative not only demonstrated the lowest coefficient variation but was also deemed the most favourable option. Biolubricant production was determined to be the second-best alternative. The adopted MCDA approach proved to be a reliable and effective tool, enabling the clear identification of the preferred WCO recycling alternative among those assessed. This was achieved through the utilization of the decision makers’ expertise and knowledge.
      Citation: Recycling
      PubDate: 2023-08-20
      DOI: 10.3390/recycling8040064
      Issue No: Vol. 8, No. 4 (2023)
  • Recycling, Vol. 8, Pages 45: Municipal Waste Recycling Customer Education
           and Communication in Slovenia and Croatia

    • Authors: Boštjan Aver, Nikša Alfirević, Ajda Fošner
      First page: 45
      Abstract: The aim of this paper is twofold: (a) to present the existing regional research related to customer education and communication in municipal waste recycling from the viewpoint of a comparative bibliometric analysis and (b) to illustrate how municipal waste recycling practices in the two countries mirror the theoretical trends identified in the literature and the EU institutional and policy requirements. We discuss the practical implementation of municipal waste recycling practices in the two European countries and provide practical recommendations for local governments, municipal companies, and other stakeholders of the municipal waste management process.
      Citation: Recycling
      PubDate: 2023-05-01
      DOI: 10.3390/recycling8030045
      Issue No: Vol. 8, No. 3 (2023)
  • Recycling, Vol. 8, Pages 46: Microfactory Design for Valorization of
           E-Waste Plastics (Acrylonitrile-Butadiene-Styrene, Polycarbonate, and
           Polypropylene) on Additive Manufacturing Sector

    • Authors: Alejandro Moure Abelenda, Farid Aiouache
      First page: 46
      Abstract: Less than half of e-waste plastics are sorted worldwide, and this rate is likely to decline as major processing countries have banned importation of e-waste plastics. This forces the development of decentralized processing facilities, also known as microfactories. The present work investigates the recyclability of different grades of acrylonitrile-butadiene-styrene (ABS) copolymer, polycarbonate, and polypropylene, which were found to be very abundant in a recycling site in the UK. The determination of the matrix relied on the resin identification codes imprinted in the e-waste plastics and subsequent Fourier-transform infrared spectroscopy (FTIR). Melt-blend extrusion technology enabled the valorization of the wasted thermoplastics as 3D filament without significant degradation of the polymers. The recycled materials maintained the tensile strength at around 2.5 MPa in agreement with the specifications offered by virgin polymers. Further characterization was done by means of laser microscope, thermogravimetric analysis, and X-ray fluorescence to determine the commercial viability of the recycled filament. A modified solvent-based method was developed with acetone to remove the brominated flame retardants: 25 g/100 mL, 30 min of contact time, and 4 extraction steps. The FTIR results show that the degradation of the rubbery dispersed phase corresponding to the butadiene can be accumulated in the less soluble fraction of the extracted ABS.
      Citation: Recycling
      PubDate: 2023-05-01
      DOI: 10.3390/recycling8030046
      Issue No: Vol. 8, No. 3 (2023)
  • Recycling, Vol. 8, Pages 47: The Use of Vacuum Residue as a Potential
           Rejuvenator in Reclaimed Asphalt Pavement: Physical, Rheological, and
           Mechanical Traits Analysis

    • Authors: Zaid Hazim Al-Saffar, Ahmed Eltwati, Ehab Essam Aziz, Haryati Yaacob, Halah Abdulsattar Dawood, Ramadhansyah Putra Jaya, Mohammed S. Al Jawahery, Ekarizan Shaffie
      First page: 47
      Abstract: Asphalt recycling technology with a high content of reclaimed asphalt pavement (RAP) is becoming more important as the price of paving materials rises and sustainable development and environmental conservation rules become more rigorous. Nevertheless, road authorities in numerous countries still prohibit the utilisation of RAP in asphalt mixes due to the negative impacts of RAP on the performance of asphalt mixtures. Consequently, different rejuvenators have been introduced to reinstate the original attributes of aged asphalt to resolve this issue. This study incorporated vacuum residue (VR) into mixtures with 40% RAP. The physical, rheological, and mechanical traits of the resultant samples were assessed. The results show that the 7.5% VR rejuvenator minimised the RAP asphalt ageing impact. Furthermore, the rejuvenating agent demonstrated physical and rheological rehabilitative benefits for the aged asphalt. The mechanical attributes of the rejuvenated samples were also enhanced compared to the virgin asphalt (VA) specimens.
      Citation: Recycling
      PubDate: 2023-05-04
      DOI: 10.3390/recycling8030047
      Issue No: Vol. 8, No. 3 (2023)
  • Recycling, Vol. 8, Pages 48: Emerging and Recycling of Li-Ion Batteries to
           Aid in Energy Storage, A Review

    • Authors: Shammya Afroze, Md Sumon Reza, Kairat Kuterbekov, Asset Kabyshev, Marzhan M. Kubenova, Kenzhebatyr Z. Bekmyrza, Abul K. Azad
      First page: 48
      Abstract: The global population has increased over time, therefore the need for sufficient energy has risen. However, many countries depend on nonrenewable resources for daily usage. Nonrenewable resources take years to produce and sources are limited for generations to come. Apart from that, storing and energy distribution from nonrenewable energy production has caused environmental degradation over the years. Hence, many researchers have been actively participating in the development of energy storage devices for renewable resources using batteries. For this purpose, the lithium-ion battery is one of the best known storage devices due to its properties such as high power and high energy density in comparison with other conventional batteries. In addition, for the fabrication of Li-ion batteries, there are different types of cell designs including cylindrical, prismatic, and pouch cells. The development of Li-ion battery technology, the different widely used cathode and anode materials, and the benefits and drawbacks of each in relation to the most appropriate application were all thoroughly studied in this work. The electrochemical processes that underlie battery technologies were presented in detail and substantiated by current safety concerns regarding batteries. Furthermore, this review collected the most recent and current LIB recycling technologies and covered the three main LIB recycling technologies. The three recycling techniques—pyrometallurgical, hydrometallurgical, and direct recycling—have been the subject of intense research and development. The recovery of valuable metals is the primary goal of most recycling processes. The growth in the number of used LIBs creates a business opportunity to recover and recycle different battery parts as daily LIB consumption rises dramatically.
      Citation: Recycling
      PubDate: 2023-05-08
      DOI: 10.3390/recycling8030048
      Issue No: Vol. 8, No. 3 (2023)
  • Recycling, Vol. 8, Pages 49: Costs of Gasification Technologies for Energy
           and Fuel Production: Overview, Analysis, and Numerical Estimation

    • Authors: Gonçalo Lourinho, Octávio Alves, Bruno Garcia, Bruna Rijo, Paulo Brito, Catarina Nobre
      First page: 49
      Abstract: During recent years, gasification technology has gained a high potential and attractiveness to convert biomass and other solid wastes into a valuable syngas for energy production or synthesis of new biofuels. The implementation of real gasification facilities implies a good insight of all expenses that are involved, namely investments required in equipment during the project and construction phases (capital expenditures, CapEx) and costs linked to the operation of the plant, or periodic maintenance interventions (operational expenditures, OpEx) or costs related to operations required for an efficient and sustainable performance of a gasification plant (e.g., feedstock pre-treatment and management of by-products). Knowledge of these economic parameters and their corresponding trends over time may help decision-makers to make adequate choices regarding the eligible technologies and to perform comparisons with other conventional scenarios. The present work aims to provide an overview on CapEx associated with gasification technologies devoted to convert biomass or solid waste sources, with a view of reducing the carbon footprint during energy generation or production of new energy carriers. In addition, an analysis of technology cost trends over time using regression methods is also presented, as well as an evaluation of specific capital investments according to the amount of output products generated for different gasification facilities. The novelty of this work is focused on an analysis of CapEx of existing gasification technologies to obtain distinct products (energy and fuels), and to determine mathematical correlations relating technology costs with time and product output. For these purposes, a survey of data and categorization of gasification plants based on the final products was made, and mathematical regression methods were used to obtain the correlations, with a statistical analysis (coefficient of determination) for validation. Specific investments on liquid biofuel production plants exhibited the highest decreasing trend over time, while electricity production became the least attractive solution. Linear correlations of specific investment versus time fitted better for electricity production plants (R2 = 0.67), while those relating the product output were better for liquid biofuel plants through exponential regressions (R2 = 0.65).
      Citation: Recycling
      PubDate: 2023-05-19
      DOI: 10.3390/recycling8030049
      Issue No: Vol. 8, No. 3 (2023)
  • Recycling, Vol. 8, Pages 50: Bioherbicide from Azadirachta indica Seed
           Waste: Exploitation, Efficient Extraction of Neem Oil and Allelopathic
           Effect on Senna occidentalis

    • Authors: Larissa Macelle de Paulo Barbosa, Jorge Oliveira Santos, Rayssa Carolinne Mouzinho de Sousa, Jomar Livramento Barros Furtado, Pedro Vidinha, Marco Aurelio Suller Garcia, Hector Aguilar Vitorino, Daiane Fossatti Dall’Oglio
      First page: 50
      Abstract: Bioherbicides are an alternative to minimize the damage caused to the environment using agrochemicals. This study had the objective of extracting neem oil from ripe waste fruits that Azadirachta indica A. Juss and optimizing the process using solvents (or a mixture of solvents) with different polarities. Then, through a solid-liquid extraction system (Soxhlet), the solvents hexane, methanol/hexane (1:1), ethanol, and hexane/ethanol (1:1) were used to determine the process with the highest yield and most efficiency. The physicochemical parameters of the extracted oil (density, acidity value, iodine value, saponification value, esters value, and molecular weight) and the % of free fatty acids were determined. In addition, the allelopathic properties of the oil (0%, 2%, 3%, and 4% m/v) on septic weed Senna occidentalis seeds were evaluated, analyzing their growth and development parameters (germination, germination speed, hypocotyl, and radicle length). Hexane was the most efficient (4 h) in neem oil extraction, with the highest yield (43%). It also provided a better oleic and linoleic acid content (41.3% and 18.6%), similar to ethanol extraction (41.1% and 20.22%). Moreover, the allelopathic properties were more prominent for the oils extracted with hexane and hexane/ethanol. This optimized process provides an efficient alternative to obtain a natural herbicidal potential for strategically controlling harmful plants.
      Citation: Recycling
      PubDate: 2023-05-24
      DOI: 10.3390/recycling8030050
      Issue No: Vol. 8, No. 3 (2023)
  • Recycling, Vol. 8, Pages 51: Effect of Virgin PP Substitution with
           Recycled Plastic Caps in the Manufacture of a Product for the Telephony

    • Authors: Beatriz Arioli de Sá Teles, Isadora Luiza Clímaco Cunha, Manoel Lisboa da Silva Neto, Hélio Wiebeck, Ticiane Sanches Valera, Simara Silveira de Souza, Alfredo Felipe de Oliveira Schmitt, Vinicius Oliveira, Luiz Kulay
      First page: 51
      Abstract: This study investigated the effects of partial and total substitutions of fossil polypropylene (PP) for recycled plastic cap equivalents in the manufacture of signage labels used by the telephone industry. Four alternative scenarios to using virgin PP were evaluated considering recycled material in flake and pellet forms based on environmental performance, degree of circularity, and technical behavior. The environmental analysis was performed by the life cycle assessment (LCA) technique, and for all impact categories evaluated, using recycled material to replace the virgin reduced adverse effects on the environment. The most significant results in this dimension, with gains of 81% in the Global Environmental Indicator, occurred when recycled PP flakes entirely replaced the fossil polymer. Once again, the highest values of the Materials Circularity Indicator (MCI) were achieved by scenarios with full recycled resin in processing the tags; however, this product must also be reused. The mechanical behavior of the tags measured technical performance, and in this case, the product made with virgin PP outperformed the recycled options except for elongation. An analysis that integrated the three dimensions into a single performance index pointed to the complete substitution of virgin material for recycled as the most balanced option.
      Citation: Recycling
      PubDate: 2023-06-09
      DOI: 10.3390/recycling8030051
      Issue No: Vol. 8, No. 3 (2023)
  • Recycling, Vol. 8, Pages 52: Valuation of Plastic Waste as a Community
           Circular Economy Strategy in the Municipality of Choco–Colombia

    • Authors: Angie Tatiana Ortega-Ramírez, Miriam Reyes Tovar, Nelly del Carmen Elmira Castro, Oscar Silva-Marrufo
      First page: 52
      Abstract: A business solution is proposed for the accumulation of waste in the Municipality of Choco without prior treatment through the establishment of a center for the reception, classification, recovery and use of solid plastic waste in the Municipality of Quibdo, which would optimize and expand the management of plastic waste. In this study, the basic diagnosis of the practices that are currently carried out in Quibdo is evaluated with the appropriation of the knowledge of the population, the technical structuring of the conditions of production of plastic wood is carried out from the management of plastic waste, recognition of the market for waste generated as an alternative for development and sustainable growth and the financial feasibility of the project and the profitability of each of the investment plans for its implementation. The results of the investigation include the identification of weaknesses and opportunities in waste management practices and the proposal of two investment plans for the establishment of the center. It is concluded that investment plan 2 would require 46,590.50 USD less than investment plan 1, equivalent to a 2.21% return compared to investment plan 1.
      Citation: Recycling
      PubDate: 2023-06-20
      DOI: 10.3390/recycling8030052
      Issue No: Vol. 8, No. 3 (2023)
  • Recycling, Vol. 8, Pages 29: Circular Construction Indicator: Assessing
           Circularity in the Design, Construction, and End-of-Life Phase

    • Authors: Kostas Anastasiades, Johan Blom, Amaryllis Audenaert
      First page: 29
      Abstract: The construction industry is responsible for half of the currently excavated amount of raw materials. In addition, a quarter of all waste in the European Union is construction waste. This construction waste comprises numerous materials that can still be reused or recycled. Thus, a shift to a circular construction sector is necessary. To make this shift, it is vital to enable the measurement of and the progress toward circularity. Therefore, this paper investigates the currently available circularity indicators with regard to the 4 Rs—Reduce, Reuse, Recycle, Recover. Subsequently, a comprehensive Circular Construction Indicator framework is introduced that evaluates a construction project according to the three typical construction phases: design, construction, and end-of-life. In this, new partial indicators to assess material scarcity, structural efficiency, and service life prediction should help designers consider these aspects already in the conceptual design stage. Lastly, suggestions for further research are defined to develop further said new partial indicators.
      Citation: Recycling
      PubDate: 2023-02-22
      DOI: 10.3390/recycling8020029
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 30: Recovery of Collagen/Gelatin from Fish Waste
           with Carbon Dioxide as a Green Solvent: An Optimization and

    • Authors: Sophat Phon, Adit Ludfi Pradana, Sudtida Pliankarom Thanasupsin
      First page: 30
      Abstract: Fish processing produces large amounts of fish waste. Instead of disposing of it, it is wiser to recover the valuable resource for high-value-added products. Our study proposed a process using carbon dioxide-acidified water as a green solvent under supercritical conditions to successfully recover collagen/gelatin from the skin and bone of striped catfish. The optimum extraction conditions were obtained at 75 bar, 37 °C, and 24 h. The yields from the dry skin and bone mass were around 37% and 8%, respectively. The extracted products were characterized by Fourier-transformed infrared spectroscopy to study the functional groups, scanning electron microscopy to evaluate the morphology, sodium dodecyl-sulfate polyacrylamide gel electrophoresis to study the protein pattern, UV–vis analysis to measure the absorption peak, and thermal gravimetric analysis to determine the denaturation temperature. The results show the viability of the proposed method on an industrial scale. The characteristics of the extracted product show promising results and potential for being developed further in many applications such as biomaterial engineering in healthcare or natural polymer-based absorbent material for efficient removal of heavy metals from water and wastewater.
      Citation: Recycling
      PubDate: 2023-02-23
      DOI: 10.3390/recycling8020030
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 31: Evaluating the Eco-Intensity Dynamics of the
           Mining Industry in Russia: Towards a Circular Economy

    • Authors: Irina Elokhova, Kirill Vyatkin, Pavel Ilyushin, Aleksandra Krutova, Anna Pepelyaeva, Natalia Sliusar
      First page: 31
      Abstract: One of the main tasks of the circular economy is the decoupling between economic growth and natural resource consumption at the input and the volume of generated waste at the output. The effectiveness of this process can be assessed by the dynamics of the eco-intensity indicators at the macro-, meso- and micro-levels. The article presents the assessment results of the decoupling and growth color of the mining sector in Russia, which show the dynamics of eco-intensity indicators and may reflect the trend towards a circular economy. For the period 2010–2021, it was revealed that negative expansion decoupling and “Black” growth have been observed in terms of generated waste and atmospheric pollution, strong decoupling and “Green” growth in terms of hydrosphere pollution, weak decoupling and “Brown” growth in terms of electricity consumption, and according to water intake from natural water bodies, expansion coupling and “Black” growth. During the study period, the gross value added (GVA) of the mining industry in Russia in comparable prices increased by 77%, while the industry’s negative impact on the atmosphere increased by 34%; the volume of production and consumption waste generation increased by 131%, and the negative impact on the hydrosphere decreased by 51%. The growth of the environmental and economic efficiency of any system can be achieved by influencing the drivers and barriers to moving towards a circular economy, so it is important to identify the most significant factors of influence for a particular industry, region or country in the current conditions. Using the ordinary least squares (OLS) method, it was revealed that factors reflecting innovative activities of the mining industry have a significant impact on reducing eco-intensity in the field of electricity consumption and water intake from natural water bodies. The significance of these factors’ influence has been confirmed not only at the macro-level, but also at the micro-level.
      Citation: Recycling
      PubDate: 2023-03-01
      DOI: 10.3390/recycling8020031
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 32: Identifying Optimal Precursors for Geopolymer
           Composite Mix Design for Different Regional Settings: A Multi-Objective
           Optimization Study

    • Authors: Mariam Abdulkareem, Anastasija Komkova, Jouni Havukainen, Guillaume Habert, Mika Horttanainen
      First page: 32
      Abstract: Global objectives to mitigate climate change in the construction industry have led to increasing geopolymer development as an alternative to carbon-intensive cement. Geopolymers can have similar mechanical properties and a lower carbon footprint. However, geopolymer production is not as homogeneous as cement because it is produced by synthesizing alkali solutions with different aluminosilicate precursors. This study assessed the feasibility of using conventional (fly ash, blast furnace slag, and metakaolin) and alternative precursors (steel slag, mine tailings, glass waste, sewage sludge ashes, and municipal solid waste incineration bottom ashes (MSWI BA)) in geopolymer mixes for different European regions (Belgium and Finland) from a sustainability perspective, using environmental, economic, and resource availability indicators as the criteria. A multi-objective optimization technique was applied to identify optimal precursors for geopolymer mixes using two scenarios: (1) considering both conventional and alternative precursors; (2) only considering alternative precursors. The results from the first scenario show that one of the most optimal precursor combinations for the geopolymer mix is 50% fly ash, 25% MSWI BA, and 25% sewage sludge ash for Belgium. For Finland, it is 19% fly ash, 27% mine tailings, and 45% MSWI BA. For the second scenario, one of the most optimal precursor combinations for Belgium is 87% MSWI BA and 13% steel slag. For Finland, it is 25% mine tailings and 75% MSWI BA. Subsequently, linear regression analysis was applied to predict the compressive strength of the identified optimal mixes, and the results for Belgium and Finland were between 31–55 MPa and 31–50 MPa for the first scenario and between 50–59 MPa and 50–55 Mpa for the second scenario, respectively.
      Citation: Recycling
      PubDate: 2023-03-02
      DOI: 10.3390/recycling8020032
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 33: Strategies for Sustainable Management of
           Agricultural Waste Vinyl in South Korea

    • Authors: Dowan Kim, Eunsook Kim, Chaegun Phae
      First page: 33
      Abstract: Vinyl, such as those in the form of mulching and vinyl houses, is used to improve agricultural productivity. It is generated as an agriculture waste vinyl (AWV) after use. The collected AWV is transported to a recycling facility and shredded, washed, and compressed to be recycled. Recycled materials can contribute to the circular economy of agriculture as they are used again as an agricultural plastic product. However, in Korea, there are concerns about the illegal disposal (landfill, incineration) of AWV. So, a new management model is needed in which stakeholders voluntarily establish an AWV management system. In this study, a sustainable management strategy was proposed. This strategy is reinforcing the responsibility of the producers of AWV and forms a value chain in the proper discharge after consumption by applying the deposit system proposed to recover AWV. Local governments and the National Agricultural Cooperative Federation (NH) proposed education to curb the illegal disposal of AWV, and for managing areas where a collection system has not yet been established, biodegradable mulching vinyl (BMV) was proposed to minimize the environmental pollution caused by AWV. It was calculated that the EPR contribution was 0.16 USD/kg, and the introduction of BMV was 0.42 USD/kg in Korea. This study will provide a new alternative in countries struggling with AWV management.
      Citation: Recycling
      PubDate: 2023-03-03
      DOI: 10.3390/recycling8020033
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 34: The Production of Gypsum Materials with
           Recycled Citrogypsum Using Semi-Dry Pressing Technology

    • Authors: Nataliya Alfimova, Sevda Pirieva, Ksenia Levickaya, Natalia Kozhukhova, Mikhail Elistratkin
      First page: 34
      Abstract: The search for ways to utilize and recycle industrial by-products is the basic principle that governs rational environmental management, synthesis of “green” materials, and appears as one of the main criteria for sustainable development in most countries of the world. Gypsum-containing waste (GCW) derived from industries, represents a large-tonnage product. The production of gypsum materials could be one of the ways to recycle GCW products. GCW from various industries can be used as an alternative to natural raw materials when producing gypsum binders. However, the features of GCW do not allow the production of a high-quality binder when traditional technologies are applied, so it requires the development of additional methods or the introduction of various modifiers to the binder system. One of the ways to increase the efficiency of GCW as a raw material for the production of gypsum binders is to apply a semi-dry pressing method, at reduced values of the W/S ratio of the binder. The objective of this research was to study the possibility of increasing the efficiency of GCW using citrogypsum for production of gypsum materials, by optimization of the mix design and by applying a semi-dry pressing method, using a lower pressure load at the molding stage. The mix design and technological parameters were optimized using mathematical planning of the experimental method. Parameters such as the amount of citrogypsum as an additive in the raw mixture, molding pressure, and water–solid (W/S) ratio were taken as input parameters of variation. To plot the relationship of the input–output parameters, the SigmaPlot software was applied, to analyze and demonstrate scientific and statistical data in the form of nomograms. It has been established that the use of the semi-dry pressing method with the optimal mix design and technological parameters, makes it possible to obtain gypsum samples with demolding strengths up to 2 MPa, and final compressive strengths up to 26 MPa. The incorporation of citrogypsum and the optimal W/S ratio of 0.25, results in positive effects, such as a reduction in the sticking properties of the mix during the demolding stage, and the homogeneity of compaction and visual appearance of the samples were also improved.
      Citation: Recycling
      PubDate: 2023-03-08
      DOI: 10.3390/recycling8020034
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 35: Flotation Sludges from Precious Metal
           Recovery Processes: From Waste to Secondary Raw Material in Ceramics

    • Authors: Matteo Perotti, Francesco Iacoviello, Narcisa M. Marian, Carlo Indelicato, Giancarlo Capitani, Riccardo Salvini, Marco Zampini, Cecilia Viti
      First page: 35
      Abstract: In this study, we investigated flotation muds (FM) deriving from the recovery processes of precious metals contained in e-waste (wastes from electronics) and exhausted catalysts. FM consist of an amorphous phase, corresponding to a Ca- and Al-rich silicatic glass, potentially usable as a secondary raw material (SRM) to obtain a final ceramic product (CFM). A high FM amount was used in our ceramic tests, and suitably mixed with variable percentages of other phases. Chemical analysis, phase composition, microstructure, pore pattern and technological properties of the new ceramic products were determined using different analytical techniques, including bulk XRF, XRD, SEM-EDS and µCT. The CFM product predominantly consists of nepheline, pyroxene and wollastonite as the main crystalline phases, with a minor amorphous phase occurring as a compact interstitial matrix. The ceramic product has a porous interconnected microstructure. Nevertheless, this microstructure does not negatively affect the mechanical properties of the ceramic product, as testified by the geo-mechanical tests, revealing good properties in terms of bending and uniaxial strength. These preliminary results point out that FM recycling is feasible, at least at the laboratory scale.
      Citation: Recycling
      PubDate: 2023-03-10
      DOI: 10.3390/recycling8020035
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 36: Attitude Is Not Enough to Separate Solid
           Waste at Home in Lima

    • Authors: Christiam Méndez-Lazarte, Victor W. Bohorquez-Lopez, Carlos Caycho-Chumpitaz, Alfredo Estrada-Merino
      First page: 36
      Abstract: Facilitating solid waste separating behavior at home continues to be a challenge for municipal programs in emerging economies. Large cities concentrate the generation of solid waste and, in Latin America, a great percentage of this waste is not re-used. Therefore, in this research, we explore the drivers motivating solid waste separation at home in Lima. We applied 450 surveys in two municipalities of Lima and analyzed the results through Structural Equation Modeling (SEM). The results demonstrate that attitude, perception of technical knowledge, and availability of physical space influence solid waste separation behavior. Additionally, the mediating role of intention between solid waste separation attitude and behavior is demonstrated. Municipal solid waste recycling programs in emerging economies tend to focus on educational and motivational actions, without giving due importance to space at home in order to manage solid waste. The lack of urban equipment and the limited availability of space at home introduce barriers that limit solid waste separating behaviors in emerging economies.
      Citation: Recycling
      PubDate: 2023-03-13
      DOI: 10.3390/recycling8020036
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 37: A Study on the Calculation of the Standard
           Recycling Cost of PVC Profiles and Flooring Waste in Korea

    • Authors: Do-Wan Kim, Kyung Kim, Choong-Real Baek, Chae-Gun Phae
      First page: 37
      Abstract: The Voluntary Agreement for Collecting and Recycling Plastic Waste (VA), including polyvinyl chloride (PVC) profiles and flooring materials, will be converted to an Extended Producer Responsibility (EPR) system from 2023. The objective of this study is to calculate the standard recycling cost and the recycling market size for preparing the new system. Among the total recycling companies participating in the VA, a cost analysis was conducted for 11 profile businesses (35% of the total businesses) and seven flooring businesses (58% of the total businesses). As a result, the standard recycling cost was calculated as 0.45 USD/kg for PVC profiles and 0.36 USD/kg for PVC flooring materials. As of 2020, the total market size is 1135 million USD (5.86 million USD for PVC profiles and 5.49 million USD for PVC flooring materials). Our research shows that few countries have nationally managed accurate data regarding PVC profiles and flooring waste. Compared to the European Union (EU), the total amount of recycled PVC products in Korea seems lower, but the recycling rate per capita is higher. This study can provide basic data about the recycling industry for the recycling academia and the manufacturing field.
      Citation: Recycling
      PubDate: 2023-03-29
      DOI: 10.3390/recycling8020037
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 38: Controlled Combustion and Pyrolysis of Waste
           Plastics: A Comparison Based on Human Health Risk Assessment

    • Authors: Arianna Moranda, Ombretta Paladino
      First page: 38
      Abstract: Increasing conditions of economic and social well-being have led to an increase in waste production. Among the waste products, a significant portion consists of plastic materials that are popular in the components of consumer goods. For this reason, the conversion of plastic to energy via controlled combustion and plastic to fuel via thermal/catalytic pyrolysis or gasification can be proposed to treat the residual heterogeneous mixed plastics that cannot be recovered as individual polymers. The quality and type of fuels that are possible to obtain from these processes are different, as is the quality of their emissions, which generally contain VOCs, PCBs, dioxins, PAHs, and heavy metals. In this work, we propose a methodology based on human health risk assessment to compare controlled combustion and catalytic pyrolysis. Many pathways are analyzed, and pollutant concentrations are computed in the atmosphere, water, vegetables, fish, and food. Exposure is evaluated for inhalation and ingestion routes by taking into account uncertainties. Our results show that the risk profile of catalytic pyrolysis is low. Controlled combustion remains an interesting process, but even if Best Available Technologies (BAT) are adopted, the cancer risk due to PAHs contained in particulate is around the threshold for people living near the plant if a long period of operation is considered.
      Citation: Recycling
      PubDate: 2023-04-03
      DOI: 10.3390/recycling8020038
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 39: Recycling of Post-Consumer Polystyrene
           Packaging Waste into New Food Packaging Applications—Part 2:
           Co-Extruded Functional Barriers

    • Authors: Frank Welle
      First page: 39
      Abstract: Post-consumer polystyrene (PS) recyclates behind a functional barrier of virgin PS polymer is an attractive way to introduce post-consumer PS recyclates in packaging materials. However, until now, there has been no official guidance published on how to test the performance of a functional barrier. In addition, no threshold limits for the evaluation of post-consumer recyclates behind FBs have been published by competent authorities. This is a drawback in the food law compliance evaluation and novel technology notification of post-consumer recyclates behind a functional barrier. In this study, co-extruded yogurt cups with an artificially spiked core layer were investigated with respect to migration of the applied surrogates. The applied migration kinetic testing method into the gas phase was shown to be sensitive and suitable for the evaluation of the functional barrier performance. For consumer safety evaluation, two worst-case scenarios were used. As a result, due to the high processing temperatures used during co-extrusion, the virgin PS functional barrier layer was partly contaminated with the surrogates from the core layer. However, on the basis of the conditions, data, and the evaluation presented, the use of post-consumer recycled PS behind an FB of virgin PS can be considered as safe.
      Citation: Recycling
      PubDate: 2023-04-03
      DOI: 10.3390/recycling8020039
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 40: The Relationship between Knowledge,
           Attitudes, Values, and Technology in Promoting Zero-Waste
           Pro-Environmental Behaviour in a Zero-Waste Campus Framework

    • Authors: Mayawi Baba-Nalikant, Nor Athiyah Abdullah, Mohd Heikal Husin, Sharifah Mashita Syed-Mohamad, Mohamad Saifudin Mohamad Saleh, Asyirah Abdul Rahim
      First page: 40
      Abstract: This study aimed to investigate the relationships between knowledge, attitudes, and values in promoting zero-waste, pro-environmental behaviour among the university campus community and how technology plays its role. A survey instrument was developed from the findings of earlier focus group discussions and in-depth interviews, which were based on the adaptation and adoption of previous studies, especially Kollmuss and Agyeman’s 2002 Model of Pro-Environmental Behaviour and a modified Knowledge-Attitude-Practises Model. Three hundred ninety-three respondent samples from Universiti Kebangsaan Malaysia, Universiti Putra Malaysia, and Universiti Sains Malaysia were analysed for their insights regarding their vision of a Zero-Waste Campus using the Structural Equation Modelling approach. The results show positive relationships between the five studied variables and the proposed hypotheses. Knowledge and attitudes serve as moderating variables, enhancing the strength of the causal effects of the related relationships. As the results show good significance, proper planning for integrating the studied variables and the proposed zero-waste campus framework can be used by university management, other institutions, or national-level agencies to develop an environment-specific plan to promote zero-waste, pro-environmental behaviour.
      Citation: Recycling
      PubDate: 2023-04-05
      DOI: 10.3390/recycling8020040
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 41: Numerical Modeling of Thermochemical
           Conversion of Biomass and Tires as Fuels for Cement Clinker Production

    • Authors: Baby-Jean Robert Mungyeko Bisulandu, Frédéric Marias
      First page: 41
      Abstract: This article presents the numerical modeling of the thermochemical conversion of biomass and tires as alternative fuels in kilns dedicated to the production of cement. The study seeks to understand and control the phenomena that occur when heavy fuel oil (traditional fuel) is partially replaced by biomass and tires. These are thoroughly mixed with meal at the entrance to the rotary kiln and form the bed of solids. The mathematical model developed takes into account both chemical reactions of meal and alternative fuels. At the entrance, the meal is made up of species such as CaCO3, MgCO3, Al2O3, SiO2, Fe2O3, MgO, CaO, C2S, C3A, C4AF and C3S, some of which form along the kiln. The article focuses specifically on the influence of alternative fuels on the clinker or cement obtained. The properties (moisture, organic matter, composition, energy value, etc.) of the biomass and the tires, which are associated with the operating parameters of the kiln, greatly influence the production of clinker. In order to understand and control the behavior of each material and the operating parameters in the clinker (cement) production process, the mathematical model follows the evolution of each species and parameters step-by-step, until the clinker is obtained. The effect of alternative fuels on clinker production was found for the kiln’s operational parameters, the dynamic angle of the bed (30°), the angle of inclination of the kiln (2°), rotation (2 rpm), the length and the inside diameter, respectively (80 m) and (4 m); the chemical and physical properties (humidity, organic, inorganic matter, C, H, O, N, S, Cl); the lower calorific value, raw material); and the numerical parameters (spatial discretization 30 and 120). Despite the high energy content of tire fuels, the results of the use of biomass give better characteristics of clinker/cement (52.36% C3S and 3.83% CaO).The results found show that biomass pyrolysis is endothermic, with the heat of reaction found to be ∆rHpyro=184.9 kJ/kg, whereas for tires, a heat of reaction of ∆rHpyro=−1296.3 kJ/kg was found, showing that the pyrolysis of this material is exothermic. Char production is higher in the case of tires than in the case of biomass, with rates of 0.261 kg/kgOrg.Mat. and 0.196 kg/kgOrg.Mat., respectively. In both cases, waste conversion was complete (100%). The cement obtained in the different cases meets the requirements of Portland cements (73.06% silicates and 18.76% aluminates), the conversion of alternative fuels is complete (100%), and the specific energy consumption is almost consistent with values from the literature.
      Citation: Recycling
      PubDate: 2023-04-06
      DOI: 10.3390/recycling8020041
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 42: Considering Waste Generation in the Energy
           Sector during the Transition to a Circular Economy

    • Authors: Anzhelika Karaeva, Elena Magaril
      First page: 42
      Abstract: The need to reduce the negative environmental impact of energetics with the growing energy demand in the world is the core objective of the industry for the upcoming decades. The global agenda in the field of environmental protection increases the requirements for evaluation of the energy investment projects, in particular for their environmental efficiency. Currently, much attention is paid to assessing the impact of the project on atmospheric air, water bodies and land resources, including the formation of industrial waste during the operational stage. The formation of production and consumption waste at other stages of the project life cycle is not considered either when generating cash flows or when conducting the assessment pf environmental efficiency. It might significantly reduce the reliability of assessment results. The purpose of this study is to develop a system of integrated accounting for all types of waste generated and the environmental costs incurred for handling them during the environmental and economic assessment of energy projects. The paper discusses modern waste management practices at energy enterprises, waste generation at various stages of investment projects implementation, and provides recommendations on waste accounting when assessing their environmental and economic efficiency.
      Citation: Recycling
      PubDate: 2023-04-08
      DOI: 10.3390/recycling8020042
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 43: Environmental Performance of Nitrogen
           Recovery from Reject Water of Sewage Sludge Treatment Based on Life Cycle

    • Authors: Ali Saud, Jouni Havukainen, Petteri Peltola, Mika Horttanainen
      First page: 43
      Abstract: Recovering and recycling nitrogen available in waste streams would reduce the demand for conventional fossil-based fertilizers and contribute toward food security. Based on life cycle assessment (LCA), this study aimed to evaluate the environmental performance of nitrogen recovery for fertilizer purposes from sewage sludge treatment in a municipal wastewater treatment plant (WWTP). Utilizing either air stripping or pyrolysis-derived biochar adsorbent, nitrogen was recovered from ammonium-rich reject streams generated during mechanical dewatering and thermal drying of anaerobically digested sewage sludge. A wide range of results was obtained between different scenarios and different impact categories. Biochar-based nitrogen recovery showed the lowest global warming potential with net negative GHG (greenhouse gas) emissions of −22.5 kt CO2,eq/FU (functional unit). Ammonia capture through air stripping caused a total GHG emission of 2 kt CO2,eq/FU; while in the base case scenario without nitrogen recovery, a slightly lower GHG emission of 0.2 kt CO2,eq/FU was obtained. This study contributes an analysis promoting the multifunctional nature of wastewater systems with integrated resource recovery for potential environmental and health benefits.
      Citation: Recycling
      PubDate: 2023-04-13
      DOI: 10.3390/recycling8020043
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 44: Environmental Analysis of the Incorporation
           of Sugarcane Bagasse in Medium Density Particleboard Panels through Life
           Cycle Assessment

    • Authors: Nara Cangussu, Maria Luiza C. Vieira, Lino Maia
      First page: 44
      Abstract: The growth of civil construction and agroindustry, resulting from population growth, caused an increase in the demand for non-renewable resources and for the exploitation of natural resources. Consequently, it caused a greater generation of waste, causing the current scenario to require alternatives for the reuse of these materials. Particleboard panels, for example, used in civil construction, can add value to waste or materials of low acceptance, such as thinning wood, mechanical wood processing waste or agro-industrial waste. Thus, this study proposed to analyse the life cycle of the sugarcane bagasse, considering the stages of extraction of materials and energy resources until their final disposal. This study aimed to compare impacts generated by the production of particleboards panels produced with wood from plantations (pine) and with the sugarcane bagasse. As a result, a better environmental performance was obtained from the panel composed of sugarcane bagasse, as it generated lower environmental impacts in all impact categories studied. The benefits range from the reduction in waste disposed of in landfills, which increase its useful life, the lower demand for reforestation, with steps that generate atmospheric emissions and degrade the soil.
      Citation: Recycling
      PubDate: 2023-04-21
      DOI: 10.3390/recycling8020044
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 7: Development and Evaluation of Sustainable
           Bituminous Paver Blocks

    • Authors: Padmakumar Radhakrishnan, Vignesh Dhurai
      First page: 7
      Abstract: Most road surfaces globally are constructed using bituminous materials. The construction of new roads and the maintenance of existing ones demand a huge amount of virgin natural aggregates. Depletion of resources that takes place during the construction of the road has an impact on cost and also on the environment. Hence, there is a need to reduce virgin aggregate use for bituminous pavement construction. This can be achieved by utilizing sustainable materials such as marble waste and reclaimed asphalt pavement (RAP) in hot mix asphalt (HMA)-type road construction. This research work is focused on sustainable development goal (SDG) 12, exclusively on the target number 12.5 which describes the recycling and reuse of materials. However, no investigations were seen to be reported on the integrated utilization of sustainable materials and RAP in bituminous paver blocks. The bituminous mixes were evaluated based on strength and compared with the control mix in this study. Bituminous paver blocks were then cast using sustainable materials and tested in the laboratory to assess the performance of the blocks through a compression test, Cantabro loss test, and wheel rut test. The test results gave satisfactory values; hence, these bituminous blocks can be used for service maintenance of the pavement structures. The study indicates that using sustainable material along with RAP in blocks can provide an eco-friendly, easily maintainable pavement system which makes it a key approach to SDG 9 as well, in terms of innovative infrastructure solutions.
      Citation: Recycling
      PubDate: 2023-01-05
      DOI: 10.3390/recycling8010007
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 8: Upscaling of a Mechanochemical Devulcanization
           Process for EPDM Rubber Waste from a Batch to a Continuous System

    • Authors: Larissa Gschwind, Carmen-Simona Jordan
      First page: 8
      Abstract: The present work is a comparative study of the effects of mechanical shear, temperature, and concentration of a chemical agent on the devulcanization process of post-industrial ethylene propylene diene (EPDM) rubber waste. Devulcanization was carried out in a heating press (no shear), an internal mixer (low shear), and a co-rotating twin screw extruder (high shear) at temperatures ranging from 100 to 200 °C. The efficiency of pure dibenzamido diphenyl disulfide (DBD) and a commercial devulcanizing agent, Struktol A89®, containing DBD were studied. Based on the results, the devulcanization process was upscaled from 40 g per batch to a continuous process with a capacity of 270 g/h. The parameters were fine-tuned regarding flow rate, screw speed, and temperature. Blends of virgin rubber (VR) and 25, 50, and 75 wt% recyclates were compared with blends of VR and 25, 50, and 75 wt% of untreated RWP. The quality of the recyclate was determined by rheometer tests, SEM images, TGA, and mechanical properties. The best results were obtained with 2 wt% DBD in the extruder with a temperature profile of 120 to 80 °C, 50 rpm, and 4.5 g per minute (gpm). The tensile strength and strain at break of the recyclate already met the requirements of DIN EN 681-1:2006 for the production of sealing systems. The compression set and Shore A hardness were restored by mixing recyclate with 25 wt% VR.
      Citation: Recycling
      PubDate: 2023-01-06
      DOI: 10.3390/recycling8010008
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 9: The Uptake of Recycled Plastic in
           Manufacturing Companies: A Moral Responsibility or Worthwhile Business

    • Authors: Owais Khan
      First page: 9
      Abstract: The production and consumption of plastics, which is indispensable in our modern life, has caused severe environmental impacts. Hence, academics and policymakers have been advocating the circularity of plastics. The role of businesses—particularly manufacturing companies—is pivotal to ensuring the circularity of plastics. This study, therefore, attempted to investigate whether chief executives of manufacturing companies based in the EU are keen on the uptake of recycled plastic and, furthermore, whether the uptake of recycled plastic is a worthwhile business strategy. This study found that the attitude, subjective norms and perceived behavioral control of chief executives positively shape their behavioral intention toward the circularity of plastics. Furthermore, the behavioral intentions of chief executives positively influence the uptake of recycled plastic in manufacturing companies, which could consequently improve business performance. This study suggests measures to increase the uptake of recycled plastic among businesses.
      Citation: Recycling
      PubDate: 2023-01-07
      DOI: 10.3390/recycling8010009
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 10: Stabilization of Soft Soil by a Sustainable
           Binder Comprises Ground Granulated Blast Slag (GGBS) and Cement Kiln Dust

    • Authors: Ruqayah Al-Khafaji, Anmar Dulaimi, Hassnen Jafer, Nuha S. Mashaan, Shaker Qaidi, Zahraa Salam Obaid, Zahraa Jwaida
      First page: 10
      Abstract: Due to its significant deficiencies such as low permeability, low bearing and shear strength, and excessive compressibility, soft soil is one of the most problematic types of soil in civil engineering and soil stabilization can be considered a suitable technique for pavements. This study investigates the use of ground granulated blast slag (GGBS) and cement kiln dust (CKD) as stabilizers for soft soil. Thus, this study involves two optimization stages; in the first stage, GGBS was incorporated into 0%, 3%, 6%, 9%, and 12% by the weight of cement to obtain the optimal percentage, which was 6%. Then, the optimal GGBS was blended with CKD in a binary system at 0%, 25%, 50%, 75%, and 100% by the dry weight of the soil. The testing program used in this paper was Atterberg limits with compaction parameters to investigate the physical properties and unconfined compressive strength (USC) at 7 and 28 days to examine the mechanical characteristics. In addition, the microstructures of the soil specimens were tested at 7 and 28 days using scanning electron microscopy (SEM). The findings reveal that the binary system enhanced the physical and mechanical properties of the soft soil. The optimum binder achieved in this study was 6% (25% GGBS and 75% CKD), which generates an increase in strength of about 3.3 times in 7 days, and of 5.5 times in 28 days in comparison to the untreated soil. The enhancement was attributed to the formation of the hydration products as approved by SEM. Consequently, in the case of soft subgrade soils, this technique can increase the pavement’s bearing capacity and performance.
      Citation: Recycling
      PubDate: 2023-01-08
      DOI: 10.3390/recycling8010010
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 11: Microstructural and Thermal Behaviour of
           Composite Material from Recycled Polyethylene Terephthalate and Fly Ash

    • Authors: Nur Hazzarita Mohd Nasir, Fathoni Usman, Ean Lee Woen, Mohamed Nainar Mohamed Ansari, Abu Bakar Mohd Supian, Saloma Saloma
      First page: 11
      Abstract: Nowadays, the environmental impact of plastic waste is crucial, and in the energy industry, fly ash, a type of solid waste, has also prompted severe ecological and safety concerns. In this study, we synthesised composite material from two industrial wastes: recycled polyethylene terephthalate (rPET) as the matrix and fly ash as the filler. The effect of different fly ash loadings on the thermal behaviour and microstructure of the composite material using rPET were evaluated. Various loading amounts of fly ash, up to 68%, were added in the rPET mixtures, and composites were made using a single-threaded bar’s barrel extruder. The feeding zone, compression zone, and metering zone made up the three functional areas of the extruder machine with a single-flighted, stepped compression screw. The composite materials were subjected to DSC and SEM equipped with EDX spectroscopy tests to examine their thermal behaviour and microstructural development. It was found that the thermal behaviour of rPET improved with the addition of fly ash but degraded as the fly ash loading increased to 68%, as confirmed by the DSC study. The composites’ microstructural development revealed an even filler distribution within the polymer matrix. However, when the fly ash loading increased, voids and agglomeration accumulated, affecting the composites’ thermal behaviour.
      Citation: Recycling
      PubDate: 2023-01-09
      DOI: 10.3390/recycling8010011
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 12: Comparison between the Mechanical Recycling
           Behaviour of Amorphous and Semicrystalline Polymers: A Case Study

    • Authors: André A. Costa, Pedro G. Martinho, Fátima M. Barreiros
      First page: 12
      Abstract: The increase in waste has motivated the adoption of the circular economy concept, which assumes particular relevance in the case of plastic materials. This has led to research of new possibilities for recycling plastics after their end-of-life. To achieve this goal, it is fundamental to understand how the materials’ properties change after recycling. This study aims to evaluate the thermal and mechanical properties of recycled plastics, namely polycarbonate (PC), polystyrene (PS), glass fibre-reinforced polyamide 6 (PA6-GF30), and polyethylene terephthalate (PET). With this purpose, injected samples were mechanically recycled twice and compared through thermal and mechanical tests, such as differential scanning calorimetry, hardness, tensile strength, and the melt flow rate. The results show that the amorphous materials used do not suffer significant changes in their properties but exhibit changes in their optical characteristics. The semicrystalline ones present some modifications. PET is the material that suffers the biggest changes, both in its flowability and mechanical properties. This work demonstrates that the mechanical recycling process may be an interesting possibility for recycling depending on the desired quality of final products, allowing for some materials to maintain comparable thermal and mechanical properties after going through the recycling process.
      Citation: Recycling
      PubDate: 2023-01-10
      DOI: 10.3390/recycling8010012
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 13: Pyro-Hydrometallurgy Routes to Recover Silica
           from Indonesian Ferronickel Slag

    • Authors: Reza M. Ulum, Natalin, Rini Riastuti, Wahyu Mayangsari, Agus B. Prasetyo, Johny W. Soedarsono, Ahmad Maksum
      First page: 13
      Abstract: Ferronickel slag is a by-product of nickel smelting that provides an abundant silica source. Based on data, every ton of nickel production is equal to eight tons of ferronickel slag production, increasing without any recycling process. It is essential to create an end-to-end process for nickel production and its by-products because this would be a problem in the future and is relevant for many industrialized countries. This study describes a strategy to process ferronickel slag to produce silica. A pyrometallurgy–hydrometallurgy process and ferronickel slag were used to increase the silica content. The process was conducted through alkali fusion; the ferronickel slag was mixed with sodium carbonate at a temperature of 1000 °C for an hour and continued via leaching, precipitation, and cleaning processes. The leaching process was conducted with four concentrations (4 M, 6 M, 8 M, and 10 M) of sodium hydroxide and three different leaching durations (2 h, 4 h, and 6 h). Using hydrochloric acid (HCl) at pH 2 and deionized (DI) water cleaning, the precipitation process was adopted to synthesize a silica powder with the lowest agglomeration and enhance its purity. Characterization was carried out using X-ray Diffraction (XRD), Scanning Electron Microscopy–Energy-Dispersive Emission (SEM-EDS), X-ray Fluorescence (XRF), and Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP-OES). This study highlighted silica characteristics that indicate high recovery by 85% through alkali fusion, HCl leaching, precipitation, and deionized water cleaning.
      Citation: Recycling
      PubDate: 2023-01-13
      DOI: 10.3390/recycling8010013
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 14: Acknowledgment to the Reviewers of Recycling
           in 2022

    • Authors: Recycling Editorial Office Recycling Editorial Office
      First page: 14
      Abstract: High-quality academic publishing is built on rigorous peer review [...]
      Citation: Recycling
      PubDate: 2023-01-13
      DOI: 10.3390/recycling8010014
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 15: Life Cycle Assessment (LCA) of 3D Concrete
           Printing and Casting Processes for Cementitious Materials Incorporating
           Ground Waste Tire Rubber

    • Authors: Matteo Sambucci, Ilario Biblioteca, Marco Valente
      First page: 15
      Abstract: Ordinary concrete is an indispensable construction material of modern society which is used for everything from mundane road pavements to building structures. However, it is often used for non-load-bearing applications (for instance, insulating lightweight building units) where mechanical strength is not a priority. This leads to an avoidable depletion of natural aggregates which could instead be replaced by alternative waste materials capable of conferring to the material the desired performance while ensuring a “green” route for their disposal. Furthermore, the automation of production processes via 3D printing can further assist in the achievement of a more advanced and sustainable scenario in the construction sector. In this work, performance and environmental analyses were conducted on a 3D-printable cementitious mix engineered with ground waste tire rubber aggregates. The research proposed a comparative study between rubberized concrete mixes obtained by 3D printing and traditional mold-casting methods to achieve a comprehensive analysis in terms of the mix design and manufacturing process. To evaluate the environmental performance (global warming potential and cumulative energy demand) of the investigated samples, Life Cycle Assessment models were built by using the SimaPro software and the Ecoinvent database. The Empathetic Added Sustainability Index, which includes mechanical strength, durability, thermo-acoustic insulation, and environmental indicators, was defined to quantify the overall performance of the samples in relation to their engineering properties and eco-footprint.
      Citation: Recycling
      PubDate: 2023-01-20
      DOI: 10.3390/recycling8010015
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 16: Fruit and Restaurant Waste Polysaccharides
           Recycling Producing Xylooligosaccharides

    • Authors: Beatriz Salustiano Pereira, Alison Andrei Schmatz, Caroline de Freitas, Fernando Masarin, Michel Brienzo
      First page: 16
      Abstract: A significant part of fruit production is wasted annually, a material of high value without use, causing environmental and social damage. These residues from agro-industrial processes, or those that can no longer be used in the market, can be recycled and generate value-added products by pretreatments/hydrolysis. One of the important pretreatments is acid hydrolysis, which can produce xylooligosaccharides (XOS) from biomass, a product of great commercial value in the food and pharmaceutical markets, mainly due to its prebiotic potential. Bananas, oranges, and guava generate a large volume of waste and represent much of Brazil’s fruit production. The dilute acid hydrolysis resulted in XOS production of 37.69% for banana peel, 59.60% for guava bagasse, 28.70% for orange bagasse, and 49.64% for restaurant residue. XOS were quantified by a liquid chromatograph system with a Bio-Rad Aminex HPX-87C column. The results show that, for this type of material and hydrolysis, the ideal conditions to produce XOS are high temperature, low time, and high acid concentration for banana peel residue (160 °C, 15 min, and 3% H2SO4), low temperature, low time, and high acid concentration for guava bagasse (100 °C,15 min and 3% H2SO4), high temperature and acid concentration with low time for orange bagasse (160 °C,15 min and 3% H2SO4) and high temperature and time and high acid concentration for restaurant waste (160 °C, 55 min and 3% H2SO4). This study identified acid hydrolysis conditions that maximized XOS production with a low amount of xylose production using agro-industrial and food residues, also showing the high potential of the chosen residues through the high yields of XOS production.
      Citation: Recycling
      PubDate: 2023-01-26
      DOI: 10.3390/recycling8010016
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 17: Trends in Extraction of Rare Earth Elements
           from Coal Ashes: A Review

    • Authors: Gjergj Dodbiba, Toyohisa Fujita
      First page: 17
      Abstract: The demand for novel, cost-effective, and environmentally friendly rare earth element and yttrium (REY) sources is essential. The recovery of REY and other valuable components from coal fly ash (CFA) may result in securing alternative resources, decreased disposal costs, and environmental protection, all of which may have positive effects. However, research on the recovery of REY from CFA is underway, and it is still necessary to assess its viability from an economic and environmental standpoint. The authors have reviewed some of the most recent advances in extracting rare earth elements from CFA. However, most techniques reported for the treatment of CFA are still at the laboratory scale. Nevertheless, there are several pathways for industrial-scale applications. Therefore, CFA treatment and the extraction of valuable products from it have considerable potential for reducing both its carbon footprint and environmental burden.
      Citation: Recycling
      PubDate: 2023-01-30
      DOI: 10.3390/recycling8010017
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 18: Quality Aspects in the Compounding of Plastic

    • Authors: Maximilian Auer, Jannick Schmidt, Jan Diemert, Gabriel Gerhardt, Maximilian Renz, Viola Galler, Jörg Woidasky
      First page: 18
      Abstract: Compounding is the final processing step for quality adjustment and control before recycled thermoplastic polymer material can be introduced into production processes. Motivated by the need for higher recyclate shares, the research question is which quality problems recycling compounders are encountered in practice, where they occur, and which mitigation options might be reasonable. Therefore, an online survey with 20 recycling compounders based in Germany was conducted asking about typical processing steps and processed materials, test procedures for quality assurance, quality problems, and possibilities for reducing quality problems. Results show that compounders mainly name impurities and contaminations of the input material as challenging and the reason for quality problems. The study shows that the problems are not dependent on the material input type. Quality problems occur along the entire secondary value chain, with companies manufacturing components themselves being particularly affected. The composition determination of the input materials helps to minimize quality problems.
      Citation: Recycling
      PubDate: 2023-01-31
      DOI: 10.3390/recycling8010018
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 19: Thermal and Sound Insulation Properties of
           Recycled Expanded Polystyrene Granule and Gypsum Composites

    • Authors: Girts Bumanis, Pauls Pavils Argalis, Genadijs Sahmenko, Deniss Mironovs, Sandris Rucevskis, Aleksandrs Korjakins, Diana Bajare
      First page: 19
      Abstract: Up to now, primary resources have been the main choice of raw material selection for production. Now, global market tendencies have brought significant attention to secondary resources as the price has been raised for primary materials, and there is a shortage of their delivery. This could bring an additional effort to increase the recycling level of construction and demolition waste, including expanded polystyrene (EPS). Efforts have been made to develop new efficient building materials with a high content of recycled EPS. In this paper, composite insulation material made of gypsum hemihydrate and recycled EPS beads by casting and compression methods were evaluated, and properties were compared. Thermal and sound insulation properties were characterized. Density from 48 to 793 kg/m3 was obtained and the thermal conductivity coefficient from 0.039 to 0.246 W/(m·K) was measured. Compression strength was from 18 kPa to 2.5 MPa. Composites produced with the compression method have a sound absorption coefficient α > 0.9 in the range from 600 to 700 Hz, while the samples produced by casting showed poor sound absorption with wide deviation. Compression methods had an advantage over the casting method as more homogenous and lightweight materials were produced with improved insulation properties.
      Citation: Recycling
      PubDate: 2023-02-03
      DOI: 10.3390/recycling8010019
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 20: Highlighting the Role of Archaea in Urban
           Mine Waste Exploitation and Valorisation

    • Authors: Annalisa Abdel Azim, Ruggero Bellini, Arianna Vizzarro, Ilaria Bassani, Candido Fabrizio Pirri, Barbara Menin
      First page: 20
      Abstract: E-materials become e-waste once they have been discarded without the intent of reuse. Due to its rich content of metals, among which many are Critical Raw Materials (CRMs), e-waste can be considered an urban mine to exploit and valorise. Common metal refining is performed by energy-intensive processes frequently based on the use of fossil fuel. Bio-metallurgy is a promising alternative for e-waste valorisation based on biological routes of specialised microorganisms able to leach solid-containing metals. Because of the physiology of these microorganisms, microbial leaching can be economically feasible, besides being an environmentally sustainable process. Like Bacteria and Fungi, Archaea are also capable of metal leaching activity, though their potential is underestimated. Among them, the extremophiles are the most studied and applied in the field of metal recovery, while mesophilic species are less common but still of high interest. Here we provide the state of industrial application of bio-metallurgy and report on the state of the art of Archaea exploitation in metal recovery from e-waste. Moreover, we give a special highlight to methanogenic archaea, which are able to convert CO2 into methane in order to highlight the potential for the valorisation of CO2-rich industrial streams generated by key processes (i.e., anaerobic digestion, concrete, and steel production) in CH4 for gas grid distribution, while making metals content in e-waste available again as raw material.
      Citation: Recycling
      PubDate: 2023-02-04
      DOI: 10.3390/recycling8010020
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 21: A Zero-Waste Campus Framework: Perceptions
           and Practices of University Campus Community in Malaysia

    • Authors: Mayawi Baba-Nalikant, Sharifah Mashita Syed-Mohamad, Mohd Heikal Husin, Nor Athiyah Abdullah, Mohamad Saifudin Mohamad Saleh, Asyirah Abdul Rahim
      First page: 21
      Abstract: This paper will explore the university campus community’s perspective towards the realization of a zero-waste campus. A qualitative approach is employed to identify the factors influencing the campus community’s awareness and participation in solid waste management (SWM). Perceptions, attitudes, beliefs, opinions, and ideas of Universiti Sains Malaysia (USM) campus community members are explored in focus group discussions (FGD) to determine the main factors influencing their zero-waste pro-environmental behaviour (PEB). The in-depth interview (IDI) is used to learn more about the university campus community’s perspectives on the themes defined by the FGD. The instruments were developed based on the adaption and adoption of previous studies, especially in reference to Kollmuss and Agyeman’s 2002 Model of Pro-Environmental Behaviour and a modified Knowledge-Attitude-Practices model. The findings show that environmental goals, environmental education, personal waste-related experience, environmental policy, environmental self-awareness, reinforcement contingencies, community engagement, social responsibilities, exemplary leadership, and social media influence the campus community’s zero-waste PEB. A framework based on an adaptation of Kollmuss and Agyeman’s model of pro-environmental behaviour is proposed to promote sustainable pro-environmental behaviour towards a Zero-Waste Campus.
      Citation: Recycling
      PubDate: 2023-02-06
      DOI: 10.3390/recycling8010021
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 22: The Effect of Recycled Citrogypsum as a
           Supplementary Mineral Additive on the Physical and Mechanical Performance
           of Granulated Blast Furnace Slag-Based Alkali-Activated Binders

    • Authors: Natalia I. Kozhukhova, Nataliya I. Alfimova, Marina I. Kozhukhova, Ivan S. Nikulin, Roman A. Glazkov, Anna I. Kolomytceva
      First page: 22
      Abstract: In the last decades, gypsum-bearing industrial wastes become one of the common globally produced industrial and domestic wastes that are currently recycled and further utilized. In this study, the gypsum-bearing waste citrogypsum was used as a Ca2+-containing component to modify the properties of alkali-activated cement (AAC) based on granulated blast-furnace slag (GBFS). Citrogypsum was used in different AAC mixes activated with three different alkaline components: Na2CO3, NaOH, and Na2SiO3. Laser granulometry was applied to assess the granulometric characteristics of citrogypsum and GBFS. Specific gravity (SG), compressive strength, and water resistance were tested to evaluate the effect of citrogypsum on the physical and strength performance of AAC. Experimental results obtained over 4-day to 28-day time periods for the studied AACs showed that the addition of citrogypsum had a detrimental effect on the properties of AAC mixes, where decreases in compressive strength between 1 and 100%, decreases in specific gravity between 4 and 30%, and decreases in water resistance between 12 and 100% were observed. It was determined that AAC mixes modified with citrogypsum cured in ambient conditions had compressive strength values 61% to 90% lower than those cured in hydrothermal conditions. In terms of strength performance, specific gravity and water resistance, citrogypsum showed the greatest effect on AAC mixes activated with NaOH, and to a lesser extent, on mixes activated with Na2CO3. The highest water resistance value of 0.77 was observed for the AAC mixes activated with Na2CO3 cured in ambient conditions, and when cured in hydrothermal conditions, the highest water resistance reached up to 0.84 for the AAC mixes activated with NaOH. It was observed that the type of alkaline activator and curing conditions are both crucial factors that govern the response of citrogypsum as a supplementary mineral additive in GBFS-based AAC mixes in regard to compressive strength, specific gravity and water resistance.
      Citation: Recycling
      PubDate: 2023-02-07
      DOI: 10.3390/recycling8010022
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 23: Recycling of Plastic Food Packages: A Case
           Study with Finnish University Students

    • Authors: Jarmo Alarinta, Margit Närvä, Gun Wirtanen
      First page: 23
      Abstract: Recycling, depositing, and proper discarding of plastics are significant means to reduce plastics in the environment. The purpose of this study was to monitor both the type and amount of plastic food packages recycled, reused, and discarded in Finnish households with at least one university student. The participating students came from various universities of applied sciences. They participated in courses related to sustainable food systems at Seinäjoki University of Applied Sciences. In total, 785 approved participants from 363 households took part in one-week monitoring. The focus was to quantify the number of food packages used and specify how the respondents handled the food packages after use. This study shows that the recycling rate of plastic packages in Finnish households was 61%. Bigger households produce less packaging waste per person than one- or two-person households. Furthermore, the recycling activity in single-person households was lower than for two- and three-person households. The Finnish deposit system for drink packages encourages people to recycle packages. This reduces municipal waste. Recycling requires knowledge of the plastic material used in food packages.
      Citation: Recycling
      PubDate: 2023-02-09
      DOI: 10.3390/recycling8010023
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 24: Identification and Evaluation of
           (Non-)Intentionally Added Substances in Post-Consumer Recyclates and Their
           Toxicological Classification

    • Authors: Christian Rung, Frank Welle, Anita Gruner, Arielle Springer, Zacharias Steinmetz, Katherine Munoz
      First page: 24
      Abstract: According to the European circular economy strategy, all plastic packaging placed on the market by 2030 has to be recyclable. However, for recycled plastics in direct contact with food, there are still major safety concerns because (non-)intentionally added substances can potentially migrate from recycled polymers into foodstuffs. Therefore, the European Food Safety Authority (EFSA) has derived very low migration limits (e.g., 0.1 µg/L for recycled polyethylene terephthalate (PET) and 0.06 µg/L for recycled high-density polyethylene (HDPE)) for recycled polymers. Thus, the use of recyclates from post-consumer waste materials in direct food contact is currently only possible for PET. A first step in assessing potential health hazards is, therefore, the identification and toxicological classification of detected substances. Within this study, samples of post-consumer recyclates from different packaging-relevant recycling materials (HDPE, LDPE, PE, PP, PET, and PS) were analyzed. The detected substances were identified and examined with a focus on their abundance, toxicity (Cramer classification), polarity (log P values), chemical diversity, and origin (post-consumer substances vs. virgin base polymer substances). It was demonstrated that polyolefins contain more substances classified as toxic than PET, potentially due to their higher diffusivity. In addition, despite its low diffusivity compared to polyolefins, a high number of substances was found in PS. Further, post-consumer substances were found to be significantly more toxicologically concerning than virgin base polymer substances. Additionally, a correlation between high log P values and a high Cramer classification was found. It was concluded that PET is currently the only polymer that complies with EFSA’s requirements for a circular economy. However, better-structured collection systems and cleaning processes, as well as more analytical methods that enable a highly sensitive detection and identification of substances, might offer the possibility of implementing other polymers into recycling processes in the future.
      Citation: Recycling
      PubDate: 2023-02-09
      DOI: 10.3390/recycling8010024
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 25: Assessing the Sorting Efficiency of Plastic
           Packaging Waste in an Italian Material Recovery Facility: Current and
           Upgraded Configuration

    • Authors: Giovanni Gadaleta, Sabino De De Gisi, Francesco Todaro, Giuseppe D’Alessandro, Silvio Binetti, Michele Notarnicola
      First page: 25
      Abstract: The first step in reintroducing plastic waste into the recycling cycle is to use material recovery facilities (MRFs). However, while the composition and types of plastic waste are changing over time, the layout of MRFs does not always adapt to this change. In this paper, an existing MRF in Southern Italy was chosen as a reference to evaluate its current performance and to estimate possible improvements in sorting through a specific upgrade. First, an analysis of the amount, composition, and sources (in terms of type of waste and distance from the MRF) of the input waste was conducted. The composition of the input waste was then compared with the amount of selected output waste streams in order to calculate the current sorting efficiency of each stream and compare it with the values obtained from the upgrade. Lastly, the current performance of the plant was compared with a previous assessment of the same MRF in order to highlight possible variation. Results showed how the incoming waste was mainly composed of packaging plastic waste, and that some plastic waste not yet selected by the plant ended up in specific output streams. Therefore, the current performance of the MRF resulted high for PET and PE bottles (80.2% and 92.8%, respectively), in contrast to mixed or flexible packaging, where the efficiency achieved lower values (55–50%). These values were caused by a weakness in the 2D flow sorting line, which the upgrade mostly addressed. The upgraded configuration increased the production of recyclable waste from 34.32% to 50.39%, especially due to the recovery of small flexible packaging films in PE and biopolymers.
      Citation: Recycling
      PubDate: 2023-02-12
      DOI: 10.3390/recycling8010025
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 26: Recycling of Post-Consumer Polystyrene
           Packaging Waste into New Food Packaging Applications—Part 1: Direct
           Food Contact

    • Authors: Frank Welle
      First page: 26
      Abstract: The increase in plastic recycling is an essential pre-requisite for the transition to a circular economy. Polystyrene (PS) is a low diffusive polymer and therefore a promising candidate for recycling back into food contact similar to polyethylene terephthalate (PET). However, such a recycling of PS cups has been not established to date on a commercial scale. Even if recycling back into food contact is desired, the health of the consumer must not be at risk. As a consequence, recycling processes must go through a conservative assessment by relevant authorities. For PS, however, evaluation criteria are not published, which is a drawback for process developers. Within the study, post-consumer PS recyclates were evaluated in a similar way to existing evaluation criteria for PET and HDPE. For the recycling of post-consumer PS back into packages with direct contact with food, there are still some points open which cannot be answered conclusively today. Upon closer inspection, there appears to be enough information available to give a first indication as to whether recycling of post-consumer PS packaging materials back into direct food contact can be considered safe. The knowledge gaps in PS recycling were determined and discussed.
      Citation: Recycling
      PubDate: 2023-02-16
      DOI: 10.3390/recycling8010026
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 27: The Effects of Data Security and Perceived
           Benefits on Mobile Phone Recycling Behaviour and the Recycling Intention
           Mediation Role

    • Authors: Taher Ben Yahya, Noriza Mohd Jamal, Balan Sundarakani, Siti Zaleha Omain
      First page: 27
      Abstract: Mobile phones are the most heavily utilised electronic devices on a global scale. Since they are relatively smaller than other electronic devices, unlike other electronic waste (e-waste), they are not disposed of properly. Hence, this study examines the factors influencing mobile phone users’ overall intention to recycle their mobile phones. The factors used originate from the theory of planned behaviour (TPB), but additional factors were also included, namely, perceived benefits and data security, to allow for a more in-depth analysis of customer behaviour. Partial least squares structural equation modelling (PLS-SEM) was employed to analyse 601 results from the United Arab Emirates (UAE) through a self-administered online survey. The results demonstrate that perceived benefits (whether environmental or financial) and perceived behavioural control possess the most statistically significant positive effects on the UAE mobile phone users’ intention to participate in reverse supply chain (RSC) processes such as refurbishing or recycling. The impacts of attitude and subjective norms were the second most positive influences. Meanwhile, only 7% of UAE mobile phone users were significantly impacted by data security in participating in RSC processes. Additionally, recycling intention had no noticeable mediation effect on the relationship among the TPB variables and the extended variables (namely, data security and perceived benefits) and mobile phone recycling behaviour. The study offers confidence to industrial players in implementing these particular factors in their reverse supply chain management (RSCM) systems to influence more users to return end-of-life (EOL) or end-of-use (EOU) mobile phones, which could, in return, assist in resource preservation and environmental protection.
      Citation: Recycling
      PubDate: 2023-02-18
      DOI: 10.3390/recycling8010027
      Issue No: Vol. 8, No. 1 (2023)
  • Recycling, Vol. 8, Pages 28: Effectiveness of the IoT in Regional Energy
           Transition: The Smart Bin Case Study

    • Authors: Dimitris Ziouzios, Minas Dasygenis
      First page: 28
      Abstract: As part of the European Green Deal, the EU aims to become climate-neutral and reach net-zero greenhouse gas emissions by 2050. Lignite has long dominated the electricity system of Greece, providing cheap and reliable energy, given the abundant and low-cost domestic resources at the cost of increased emission. In line with its national and international commitments to climate action, Greece needs to urgently transform its energy system and overcome its technological lock-ins, paving the way for a net-zero emission economy by the mid-century. The Internet of Things plays a significant role in this direction, providing with its technologies the protection of the environment and creating new jobs. The smart bins constitute an interesting proposal for areas in the energy transition. This research work reflects the current situation in the region of Western Macedonia and proposes the smart bin project as a part of the solution in the transition to the post-lignite era. For this purpose, survey research has been conducted in the municipalities of Greece on waste management technology.
      Citation: Recycling
      PubDate: 2023-02-20
      DOI: 10.3390/recycling8010028
      Issue No: Vol. 8, No. 1 (2023)
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