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Waste Recycling and Circular Economy: From Trash to Treasure

A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Waste and Recycling".

Deadline for manuscript submissions: 30 April 2024 | Viewed by 23131

Special Issue Editors

Hydrometallurgy and Environment Group, The Robert M. Buchan Department of Mining, Queen’s University, Goodwin Hall, 25 Union St., Kingston, ON K7L 3N6, Canada
Interests: sustainable and applied chemistry; extractive metallurgy; mineral processing; waste recycling/management; resource recovery; material synthesis for metal extraction applications
Faculty of Engineering, Department of Chemical and Materials Engineering, University of Alberta, 12-245, Donadeo Innovation Centre for Engineering, 9211-116 Street NW., Edmonton, AB T6G 1H9, Canada
Interests: hydrometallurgy; critical metal processing; solution purification; end-of-life product recycling; secondary resource processing; mining waste treatment; sustainable processing; circular economy
Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, ON M5S 3E5, Canada
Interests: recycling of Li-ion batteries; recovery of REE from primary and secondary resources; purification and crystallization of materials for battery industry; development of next-generation Al-ion batteries; material synthesis for NMC Li-ion batteries; thermal management of Li-ion batteries

Special Issue Information

Dear Colleagues,

In recent decades, the development of science and technology has made human life easier and more comfortable, but has also built up environmental and economic pressure. It has increased the consumption of primary resources due to the high market demand and huge generation of waste during the production of products, as well as at the user end. In a world bank report published in 2018, global waste production was found to be responsible for about 5% of global emissions, with an output of 1.6 billion metric tons of carbon dioxide equivalent in 2016, and is expected to reach 2.6 billion metric tons by 2050. This has an adverse effect on nature, the climate, and living beings. The preservation of primary resources, fulfillment of market demand, and recycling of waste have also been addressed through the concept of the circular economy, which is based on the implementation of cleaner and sustainable technologies, and innovative business models with supported policies. 

Scientists have developed many technologies for the recycling of different kinds of waste, e.g., mining/metallurgical, electronic, batteries, polymer, construction, plastic, food, and end-of-life products wastes. Despite the increasing number of recycling methods, further efforts are still required to devise innovations that provide more green, sustainable, and economical solutions for waste material treatment and give recycled materials a second life. In addition, the use of circular economy principles will be useful for the improvement of technologies and affect the overall economic and environmental impact.

This Special Issue invites both research and review articles focused on the broad range of waste (mentioned above) recycling options and their conversion into useful products using sustainable technologies. Studies on the circular economy and possible industrial solutions are also welcome. Possible themes of interest include, but are not limited to, the following:

  • Sustainable processes for different kinds of waste (mentioned above) recycling;
  • Novel methods for the separation of critical metals from secondary resources;
  • Complexity, challenges, and risks in a circular economy;
  • Circular economy models for waste recycling and their impact;
  • Innovative processes for the extraction of REEs, Li, Ni, Co, Ga, In, etc., from end-of-life products;
  • Application of biological processes to recover values from wastes and plastic/polymer waste degradation;
  • Food waste treatment: biogas production and bioenergy sustainability;
  • Hazardous waste remediation/detoxification;
  • Current trends for construction and demolition waste management.

Dr. Harshit Mahandra
Dr. Farzaneh Sadri
Dr. Monu Malik
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • circular economy
  • net-zero carbon emission
  • critical metals
  • waste recycling
  • end-of-life product
  • sustainability
  • waste degradation
  • hazardous materials
  • biotechnology

Published Papers (14 papers)

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Research

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14 pages, 2007 KiB  
Article
Analysis of Waste Tire Particle Movement in a Single Horizontal-Axis Stirred Reactor Based on the Eulerian Discrete Element Method
by Litong Hou, Yicheng Wu, Xiaomin Chen, Junrong Liu and Yongzhi Ma
Sustainability 2024, 16(6), 2301; https://doi.org/10.3390/su16062301 - 11 Mar 2024
Viewed by 382
Abstract
The pyrolysis of waste tires has been considered a potential sustainable solution in light of escalating carbon dioxide emissions. Nevertheless, current research indicates a lack of comprehensive understanding regarding the movement of waste tire particles in a single horizontal-axis stirred pyrolysis reactor. This [...] Read more.
The pyrolysis of waste tires has been considered a potential sustainable solution in light of escalating carbon dioxide emissions. Nevertheless, current research indicates a lack of comprehensive understanding regarding the movement of waste tire particles in a single horizontal-axis stirred pyrolysis reactor. This study employed EDEM 2021.2 software to perform comprehensive numerical simulations of a single horizontal-axis stirred pyrolysis reactor, examining the impact of three main production factors—particle size, feed rate, and central axis speed—on particle motion. By acquiring contact data between particles and reactor walls, we illustrated the persistent motion of particles during the operation of the equipment. The research findings suggest that with the rise in rotational speed, there is a corresponding increase in particle accumulation. In high-speed conditions, the interaction between particles and the reactor wall is intensified. The contact level increased by 15.54% (at 3 r/min) and 25.66% (at 5 r/min) with the rise in rotational speed. Furthermore, at an identical rotational speed, the interaction between the larger particle group and the wall surpassed that of the smaller particle group. Doubling the feed rate led to a reduction of over 10% in the contact level between particles and the reaction wall at varying speeds. Through a thorough analysis of various factors influencing particle motion, our objective is to elucidate the motion traits of particles in the reactor, offering crucial theoretical direction and technical assistance to enhance production efficiency and ensure the secure and steady operation of pyrolysis reactors. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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21 pages, 4323 KiB  
Article
Assessment of Modified Culture Conditions for Fungal Bio-Oxidation of Sulfidic Gold Ores Performed at Circumneutral pH
by Guillermo Hein, Harshit Mahandra and Ahmad Ghahreman
Sustainability 2023, 15(21), 15559; https://doi.org/10.3390/su152115559 - 02 Nov 2023
Viewed by 476
Abstract
The significant neutralization of waste streams required after the acidic bio-oxidation of sulfidic gold ores could be avoided by performing a novel treatment at circumneutral pH with an in situ neutralization. For the first time, the white-rot fungus Phanerochaete chrysosporium was incubated in [...] Read more.
The significant neutralization of waste streams required after the acidic bio-oxidation of sulfidic gold ores could be avoided by performing a novel treatment at circumneutral pH with an in situ neutralization. For the first time, the white-rot fungus Phanerochaete chrysosporium was incubated in a modified culture medium containing corn steep, an industrial waste product, to support microbial activity and, subsequently, the oxidation of a sulfidic ore at an initial circumneutral pH environment. In this investigation, the concentration of the native culture medium ingredients was first evaluated with response surface methodology to attain maximum sulfide oxidation. The statistical analysis proposed a modified culture medium composed of 12.86 g/L glucose, 2.20 g/L malt extract, 1.67 g/L yeast extract, and 0.49 g/L MgSO4·7H2O to reach a maximum of 28.7% sulfide oxidation after 14 d-bio-oxidation. pH-controlled batch cultures showed that an increase in initial pH in the range of 5.8 to 7.0 reduced the microbial activity, affecting sulfide oxidation. In addition, the modified culture medium at which yeast extract was substituted with 1.67 g/L corn steep produced comparable microbial activity and sulfide oxidation after 14 d, attaining 21.6% at 5% w/v with a maximum 39 U/L lignin peroxidase and 116 U/L manganese peroxidase. A 40.6% sulfide oxidation and 43.8% gold recovery were obtained after 42 d three-cycle replenishing bio-oxidation and 24 h cyanidation, respectively. Overall, corn steep waste showed the potential to substitute more expensive culture medium ingredients, supporting microbial activity and oxidation of sulfidic gold ores at an initial circumneutral pH and contributing to circularity of waste management. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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16 pages, 1922 KiB  
Article
Study on Co-Pyrolysis of Coal and Biomass and Process Simulation Optimization
by Biao Wang, Na Liu, Shanshan Wang, Xiaoxian Li, Rui Li and Yulong Wu
Sustainability 2023, 15(21), 15412; https://doi.org/10.3390/su152115412 - 30 Oct 2023
Cited by 1 | Viewed by 1036
Abstract
In this paper, the optimal process conditions for coal–biomass co-pyrolysis were obtained through pyrolysis experiments. The results show that under the condition of the pyrolysis temperature of 500 °C, the pyrolysis oil yield and positive synergistic effect reach the maximum, and the ratio [...] Read more.
In this paper, the optimal process conditions for coal–biomass co-pyrolysis were obtained through pyrolysis experiments. The results show that under the condition of the pyrolysis temperature of 500 °C, the pyrolysis oil yield and positive synergistic effect reach the maximum, and the ratio of coal to biomass raw materials is 1:3. The effects of three loading methods (coal loading on biomass, biomass loading on coal, and coal–biomass mixing) on the distribution of simulated products of coal–biomass co-pyrolysis were constructed using Aspen Plus V11 software. The experimental results of pyrolysis carbon, pyrolysis oil, pyrolysis gas, and water under three different ratios are close to the simulation results, and the maximum error is 8%. This indicates that the model is dependent. This paper analyzes the economic situation in terms of investment in factory construction, raw material collection, product production, and product sales. The results show that when the processing scale is 9 tons h−1, the pyrolysis plant can be profitable in the first year. This study provides basic data and the basis for the commercialization investment of coal–biomass co-pyrolysis technology. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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16 pages, 2863 KiB  
Article
Research on Magnetic Rollers for Recovering Non-Ferrous Metals from End-of-Life Vehicles Employing Machine Learning
by Youdong Jia, Jianxiong Liu and Zhengfang Li
Sustainability 2023, 15(18), 13451; https://doi.org/10.3390/su151813451 - 08 Sep 2023
Viewed by 736
Abstract
Recovering copper foil and crushed aluminum from end-of-life vehicles (ELVs) is a significant issue in the recycling industry. As a key technology for sorting aluminum, copper, and other non-ferrous metals, eddy current separation (ECS) is efficient in isolating the non-ferrous metals according to [...] Read more.
Recovering copper foil and crushed aluminum from end-of-life vehicles (ELVs) is a significant issue in the recycling industry. As a key technology for sorting aluminum, copper, and other non-ferrous metals, eddy current separation (ECS) is efficient in isolating the non-ferrous metals according to their different electrical conductivity and density. However, further research is still needed in the separation of large-size copper foil and crushed aluminum from scrapped vehicles. In this study, support vector regression (SVR) and the sparrow search algorithm (SSA) are exploited for the first time to be used in optimizing the Halbach magnetic roller. Firstly, the numerical simulation results are based on the response surface methodology (RSM). Then, the accuracy of four kernel functions employing SVR is compared to select a kernel function. The sparrow search algorithm (SSA) is proposed to optimize the structural parameters of the Halbach magnetic roller, concentrating on the above-selected kernel function. Meanwhile, the parameters are confirmed. Numerical simulation results indicate that machine learning for magnetic roller optimization is feasible. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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26 pages, 2710 KiB  
Article
Measuring the Circularity and Impact Reduction Potential of Post-Industrial and Post-Consumer Recycled Plastics
by Anna Schulte, Benjamin Kampmann and Christina Galafton
Sustainability 2023, 15(16), 12242; https://doi.org/10.3390/su151612242 - 10 Aug 2023
Cited by 1 | Viewed by 2162
Abstract
Post-industrial recycling (PIR) and post-consumer recycling (PCR) are measures used to sustain resources by improving material circularity and sustainability. Currently, circularity is mainly measured as the degree of reutilization of a material from 0 to 100% at the product or company level. This [...] Read more.
Post-industrial recycling (PIR) and post-consumer recycling (PCR) are measures used to sustain resources by improving material circularity and sustainability. Currently, circularity is mainly measured as the degree of reutilization of a material from 0 to 100% at the product or company level. This measure fails to assess the resource usage over multiple product life cycles. Therefore, we propose to assess circularity as (i) the frequency of resource use in products (effective circularity, eC), and as (ii) a vehicle to reduce environmental impacts (environmentally efficient circularity, eeC). Additionally, to compare the environmental impacts of using recycled materials from PIR or PCR, we analyze their impact reduction potential (IRP), indicating the environmental benefits of recycling in relation to virgin material submitted to the market. We demonstrate the suggested indicators for a case study material: polypropylene. For this polymer type, the eC ranges between 0.93 and 9.08 uses of the resource, on average, depending on collection, sorting, and recycling rates. Likewise, the eeC ranges between 0.31 and 1.50 uses per kg of CO2 equivalents emitted. PCR has a higher IRP regarding climate change impacts than PIR in all analyzed scenarios. The results reveal the relevance of PCR and PIR beyond the product life cycle. Finally, we discuss possible embeddings of the indicators in the assessment of climate policy and environmental protection measures, such as strengthening the use of PCR in contrast to PIR materials. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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17 pages, 1657 KiB  
Article
Performance Analysis of Manufacturing Waste Using SWARA and VIKOR Methods: Evaluation of Turkey within the Scope of the Circular Economy
by Alaeddin Koska and Mehri Banu Erdem
Sustainability 2023, 15(16), 12110; https://doi.org/10.3390/su151612110 - 08 Aug 2023
Cited by 2 | Viewed by 959
Abstract
The increasing population and industrial developments driven by growing needs and expectations have led to an increase in consumption. The rise in consumption, in turn, results in more waste generation. The management of waste has become a global issue concerning human and environmental [...] Read more.
The increasing population and industrial developments driven by growing needs and expectations have led to an increase in consumption. The rise in consumption, in turn, results in more waste generation. The management of waste has become a global issue concerning human and environmental health. As a solution to climate change, waste, and biodiversity loss, the concept of the circular economy has emerged, which involves a global effort. Zero waste, which is one of the key elements of the circular economy, is regulated by waste management legislation in the European Union in accordance with the waste management hierarchy. Therefore, waste management is an important and urgent issue that requires significant planning, especially for countries with trade relations with the European Union. This study aims to evaluate the performance of waste management in Turkey’s manufacturing industry within the scope of the circular economy. The SWARA (Step-wise Weight Assessment Ratio Analysis) and VIKOR (VIseKriterijumsa Optimizacija I Kompromisno Resenje) multi-criteria decision-making methods were used in the research. The examination of manufacturing waste in conjunction with the waste hierarchy and within the scope of the circular economy using multi-criteria decision-making methods sets this study apart from other research on the subject. The analysis results indicate that Turkey, particularly in the preference for the option of selling, has shown an increasing trend in waste reduction, reuse, and recycling indicators, while showing a decreasing trend in disposal. In this context, it can be said that Turkey will not face difficulties in the process of aligning with the European Green Deal, and positive environmental developments have been observed. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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17 pages, 6455 KiB  
Article
A Study on the Production Methods of Upcycling Tweed Fabric Using Clothing Waste Based on Chanel’s Tweed Design
by Hyewon Lee
Sustainability 2023, 15(4), 3374; https://doi.org/10.3390/su15043374 - 12 Feb 2023
Cited by 1 | Viewed by 2086
Abstract
This study aimed to produce upcycled tweed fabric using clothing waste, and to this end, weaving methods for tweed were designed, and the creative upcycling of tweeds was produced. For the improvement in the quality of recycled fabrics and to produce creative, upcycled [...] Read more.
This study aimed to produce upcycled tweed fabric using clothing waste, and to this end, weaving methods for tweed were designed, and the creative upcycling of tweeds was produced. For the improvement in the quality of recycled fabrics and to produce creative, upcycled tweed designs, four weaving methods were designed based on Chanel’s tweed design. Various types of discarded clothing waste were collected and used as materials. The upcycling tweeds produced were evaluated by experts based on the factors of novelty and appropriateness. As a result of the evaluation, all of the upcycled tweed fabrics presented excellent creativity scores. The creativity score was high when different materials, such as yarn and fabric tape and yarn and bead, were used. Tweed weaving is not difficult to perform, and our interest increased during the weaving process. The creativity of upcycling tweed fabric was discussed in depth, centered on experts who evaluated upcycling tweeds. Through this study, the possibility of popularizing the upcycling of tweed fabric using clothing waste is expected. This study is meaningful in that it presents aesthetic and functional utilization methods for decreasing clothing waste and shows the possibility of creative changes made to clothing waste. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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16 pages, 2478 KiB  
Article
Construction and Demolition Waste as Substrate Component Improved the Growth of Container-Grown Duranta repens
by Jingjing Jia, Zhiguo Zhang, Zhijuan Tai, Ming Yang, Yuxin Luo, Zhuo Yang and Yumei Zhou
Sustainability 2023, 15(2), 1585; https://doi.org/10.3390/su15021585 - 13 Jan 2023
Cited by 1 | Viewed by 1241
Abstract
Small size construction and demolition waste (CDW) is rarely reused and consequently causes environmental problems. CDW can increase aeration porosity of soil due to the big surface area and water absorption. In order to investigate the feasibility and function of CDW as a [...] Read more.
Small size construction and demolition waste (CDW) is rarely reused and consequently causes environmental problems. CDW can increase aeration porosity of soil due to the big surface area and water absorption. In order to investigate the feasibility and function of CDW as a component of container substrate, we mixed four small sizes CDW (<10 mm) of 0–3, 3–6, 6–8, and 0–10 mm with clay soil according to the mass ratios of 20%, 35%, and 50% to plant one-year old Duranta repens cuttings, clay soil (CS) and pure CDW (CW) as the controls. Cluster analysis and principal component analysis (PCA) were performed to screen the most suitable particle size and proportion of CDW for plant growth and physiological function. The substrate containing 50% 3–6 mm CDW (S6) had the higher aeration porosity, lower water loss, better water retention and permeability, and therefore higher PCA score. The total branch length of plants in the S6 was increased by 18% and 71%, leaf area by 116% and 444%, and net photosynthetic rate by 10% and 59% compared to CS and CW, respectively. The suitable CDW has potential to improve substrate properties and can effectively improve plant growth. Meanwhile, the reuse of CDW can partially alleviate the problem of construction waste disposal and environmental pollution, and provide reference for the research on the combination of CDW and landscaping. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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20 pages, 9068 KiB  
Article
Recycling Discarded Facemasks of COVID-19 Pandemic to New Novel Composite Thermal Insulation and Sound-Absorbing Materials
by Khaled Al-Salem, Mohamed Ali, Redhwan Almuzaiqer, Zeyad Al-Suhaibani and Abdullah Nuhait
Sustainability 2023, 15(2), 1475; https://doi.org/10.3390/su15021475 - 12 Jan 2023
Cited by 2 | Viewed by 1981
Abstract
The COVID-19 pandemic has forced the whole world to wear single-use disposable facemasks for health protection. Studies have shown that about 129 billion facemasks are wasted each month, which will contaminate the environment and create a big problem in getting rid of them. [...] Read more.
The COVID-19 pandemic has forced the whole world to wear single-use disposable facemasks for health protection. Studies have shown that about 129 billion facemasks are wasted each month, which will contaminate the environment and create a big problem in getting rid of them. These discarded facemasks are usually dumped in garbage bins, in landfills, or in some cases littering them on the streets, which creates a health hazard to human beings. In order to solve such environmental problems, the current study presents new novel composite materials developed by recycling discarded facemasks. These materials have great potential to be used for both thermal insulation and sound-absorbing for building walls. Experiments have been performed to make bound composite materials using the discarded facemasks as new raw materials with wood adhesive as a binder. The discarded facemasks were first heated for one and half-hour at 120 °C to kill any contaminants (biological or others). Five different composites are made: the first uses the complete facemasks, the second uses facemasks with iron nose clip only, the third uses facemasks with no both ear loops and iron nose clip, the fourth one contains the elastic ear loops only, and the fifth one has facemasks with elastic ear loops only. Coefficients of thermal conductivity for the five samples are obtained as 0.0472, 0.0519, 0.05423, 0.0619, 0.0509 (#5, e), and 0.04347 (#5, f) W/m K at 25 °C, respectively. The sound-absorbing coefficient for samples 1, 2, and 3 is above 0.5 in general and, at some frequencies, approaches 0.8. Results show that the soft samples with low binder concentration have a good sound absorbing coefficient at high frequency, while the one with high binder concentration has that at a low frequency for the same facemasks’ mass. Mechanical properties of all samples are also reported by performing the three-point bending moment. Composite samples have a low moisture content (0.2%) and have high thermal stability up to 325 °C. These composite samples could replace the petrochemical and synthetic thermal insulation materials and, at the same time, get rid of the huge discarded waste facemasks, which is considered a huge environmental problem. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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16 pages, 3816 KiB  
Article
Assessment of the Chemical Reactivity of Brazilian Stone Cutting Plant Waste into Cementitious Matrices
by Anderson Batista Passos, Lucas Onghero, Paulo Ricardo de Matos, Tatiane Benvenuti, Laurence Colares Magalhães, Antonio Pedro Novaes de Oliveira, José Renato de Castro Pessôa, Lisandro Simão and Marcelo Tramontin Souza
Sustainability 2022, 14(24), 16925; https://doi.org/10.3390/su142416925 - 16 Dec 2022
Viewed by 1823
Abstract
The problems generated by the ornamental stone extraction and processing industry caused by the inadequate disposal of this waste can negatively affect rivers, lakes, streams, and even natural water reservoirs. This study discusses and evaluates the potentiality and challenges of dimension stone waste [...] Read more.
The problems generated by the ornamental stone extraction and processing industry caused by the inadequate disposal of this waste can negatively affect rivers, lakes, streams, and even natural water reservoirs. This study discusses and evaluates the potentiality and challenges of dimension stone waste (DSW) recycling generated from a Brazilian dimension stone processing industry in Portland cement formulations. Cement pastes with different amounts of DSW (10–30 wt.%), quartz (10 wt.%), and calcium carbonate (10 wt.%) were prepared and characterized in the fresh and hardened states. The results showed that DSW can be used in cement formulations, and its reactivity is governed by the size of the particles. With up to 10% DSW in place of cement, the samples had greater workability and compressive strength at 28 days compared with the reference mix. However, the strength was lower at early ages (3 and 7 days). When DSW is milled, the strength of the samples containing the waste matched the reference values at all ages, and the recommended replacement limit rose to 20%. On the other hand, the particle size reduction significantly decreased the workability. The use of DSW in cement-based formulations is encouraged due to the strong presence of stone processing and cement companies in Brazil and worldwide. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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16 pages, 1491 KiB  
Article
Life Cycle Sustainability Assessment of Single Stream and Multi-Stream Waste Recycling Systems
by Costantino Berardocco, Hannah Delawter, Thomas Putzu, Larson Curtis Wolfe and Hao Zhang
Sustainability 2022, 14(24), 16747; https://doi.org/10.3390/su142416747 - 14 Dec 2022
Cited by 1 | Viewed by 2080
Abstract
An increasing trend of moving towards single-stream waste management systems is occurring in many municipalities. This is because of the ability to process greater quantities of materials, minimize material management costs, and maximize recycling convenience and participation. Research on evaluating comprehensive sustainability (economic, [...] Read more.
An increasing trend of moving towards single-stream waste management systems is occurring in many municipalities. This is because of the ability to process greater quantities of materials, minimize material management costs, and maximize recycling convenience and participation. Research on evaluating comprehensive sustainability (economic, environmental, and social) of the two streams is very limited. This study looks to gain an in-depth understanding of two waste management systems and assist in the decision-making processes of municipalities. To achieve this, the study provides a framework for evaluating economic, environmental, and social impacts as well as a sustainability assessment of single- vs. multi-stream waste management systems within the scope of a typical North American college town. A life cycle assessment framework was employed. The scope of the assessment includes production of materials, collection, sorting, and processes included in a material recovery facility (MRF). The functional unit is 1 ton of municipal solid waste. The case study was conducted on a North American college city during its transition from multi-stream recycling to single-stream recycling. The sustainability assessment result of the case study reveals that the single-stream recycling collection cost is slightly lower (USD 86.96/ton) than the multi-stream recycling collection cost (USD 89/ton). Additionally, the GHG emissions for the single-stream recycling system (10.56 kg CO2eq/ton) are slightly higher than for the multi-stream recycling system (9.67 kg CO2eq/ton). This is due to the complexity of the processes involved in the MRF. Nevertheless, recycling rate is the determining factor for life cycle GHG emissions and costs. Municipal solid waste policymakers could benefit from this study by using the framework and study results for tactical and strategic decision-making. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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Review

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37 pages, 2528 KiB  
Review
Advances in the Sustainable Development of Biobased Materials Using Plant and Animal Waste as Raw Materials: A Review
by Sebastián Salazar Sandoval, Alejandra Amenábar, Ignacio Toledo, Nataly Silva and Paulina Contreras
Sustainability 2024, 16(3), 1073; https://doi.org/10.3390/su16031073 - 26 Jan 2024
Viewed by 887
Abstract
There is substantial concern about critical environmental problems related to waste in production sectors such as textile, construction, and packaging. The materials ascribed to the sector’s unsustainability are primarily fabrics, plastic, and hazardous solvents, making developing new biobased materials imperative. As such, various [...] Read more.
There is substantial concern about critical environmental problems related to waste in production sectors such as textile, construction, and packaging. The materials ascribed to the sector’s unsustainability are primarily fabrics, plastic, and hazardous solvents, making developing new biobased materials imperative. As such, various strategies have been investigated to convert and recycle waste and give them commercial value via the manufacture of biobased materials. This review discusses the various types of raw materials as sources to develop new biobased materials that could promote the transition toward sustainability. According to the literature, the functional qualities of biobased materials are comparable to those of synthetic materials. Raw material sources such as biomass, derived from plant and animal-based waste, are attractive due to their low cost, abundance, and biodegradability. The manufacture of biomaterials, as well as their characterization and performance, are also discussed. Further, this review will offer a comprehensive view of the potential applicability and current commercial applications of the developed biobased materials in relevant areas such as packaging, construction, textile, and wastewater remediation. This could be a potential field of research to address the environmental challenges posed by the continuous growth of the global population. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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40 pages, 20943 KiB  
Review
Sourcing, Refining and Recycling of Rare-Earth Magnets
by John Ormerod, Anirudha Karati, Ajay Pal Singh Baghel, Denis Prodius and Ikenna C. Nlebedim
Sustainability 2023, 15(20), 14901; https://doi.org/10.3390/su152014901 - 16 Oct 2023
Cited by 1 | Viewed by 2936
Abstract
Permanent magnets today are used in a wide range of transportation, industrial, residential/commercial, consumer electronics, defense, domestic, data storage, wind energy, and medical markets and applications. There are five classes of commercial permanent magnet materials; however, magnets based on Nd-Fe-B account for over [...] Read more.
Permanent magnets today are used in a wide range of transportation, industrial, residential/commercial, consumer electronics, defense, domestic, data storage, wind energy, and medical markets and applications. There are five classes of commercial permanent magnet materials; however, magnets based on Nd-Fe-B account for over 60% of the global magnet production by value. They typically contain around 31 wt.% of rare earth elements (REEs), principally, Nd and Pr, plus Dy for higher-temperature performance. Nd-Fe-B magnets are forecast to grow throughout this decade, largely driven by the growth in electric vehicles of all types. However, several studies forecast a shortfall of the primary REEs from mined resources. In this paper, the sourcing, processing, and recycling of REEs are discussed. Additionally, presented are the advantages and disadvantages of the major recovery and recycling technologies for REEs. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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16 pages, 1179 KiB  
Review
Waste to Wealth of Apple Pomace Valorization by Past and Current Extraction Processes: A Review
by Nicky Rahmana Putra, Dwila Nur Rizkiyah, Ahmad Hazim Abdul Aziz, Mohd Azizi Che Yunus, Ibham Veza, Irianto Harny and Andy Tirta
Sustainability 2023, 15(1), 830; https://doi.org/10.3390/su15010830 - 03 Jan 2023
Cited by 14 | Viewed by 3190
Abstract
Every year, more than 50 million metric tons of apples are produced, and apple pomace is frequently discarded as waste in the food industry. Apple pomace, a byproduct of apple juice and cider production, is used as a sustainable raw material to make [...] Read more.
Every year, more than 50 million metric tons of apples are produced, and apple pomace is frequently discarded as waste in the food industry. Apple pomace, a byproduct of apple juice and cider production, is used as a sustainable raw material to make valuable products such as nutraceuticals and pectin. Apple pomace contains a substantial amount of antioxidant compounds, which have been related to several health advantages. Therefore, valuable components extracted from this byproduct may be used in the food and pharmaceutical industries. The common and new technologies to obtain valuable products from apple pomace which has come from production of apple juice or cider. Especially, emphasis of new and green technique is very important and will contribute the literature. Therefore, this review discussed apple processing, pectin as a bioactive compound, the extraction methods, current applications of apple pomace byproducts, and future studies on its potential uses in food. Full article
(This article belongs to the Special Issue Waste Recycling and Circular Economy: From Trash to Treasure)
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