Recycling

17 pages, 5917 KiB

Open AccessArticle

Best Available Technology for P-Recycling from Sewage Sludge—An Overview of Sewage Sludge Composting in Austria

by Bernhard Stürmer and Melanie Waltner

Recycling 2021, 6(4), 82; https://doi.org/10.3390/recycling6040082 - 17 Dec 2021

Cited by 3 | Viewed by 3976

In order to close the phosphorus cycle in the long term, efficient recycling processes are necessary to ensure that this critical nutrient can be returned to arable land. Sewage sludge recycling is of particular importance due to the relatively high phosphorus content of [...] Read more.

In order to close the phosphorus cycle in the long term, efficient recycling processes are necessary to ensure that this critical nutrient can be returned to arable land. Sewage sludge recycling is of particular importance due to the relatively high phosphorus content of sewage sludge. In this article, the current recycling paths of Austrian sewage sludge are highlighted, focusing on the advantages and limitations of sewage sludge composting. In addition to nutrient contents, pollutant loads were also analyzed in order to also discuss the limitations of this recycling pathway. Therefore, data from Austrian composting plants with focus on sewage sludge are used. The results show that the currently relevant pollutants (heavy metals) are predominantly below the limits prescribed for recycling and spreading on arable land. However, in order to decide on a recycling path at an early stage, a pollutant monitoring system must be in place. Due to pollution, mono-incineration with subsequent phosphorus recovery is also currently being discussed in Austria. Mono-incineration can represent an important component of sewage sludge disposal, because some sewage sludges are not suitable for composting due to potential environmental hazards. Therefore, it is important that evidence-based limit values and measures for the reduction in pollutants for input sources are determined. Full article

(This article belongs to the Special Issue Reuse of Wastewater: Recovery of Water, Nutrients, and Energy)

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14 pages, 2394 KiB

Open AccessArticle

Assessment of Biodegradation and Eco-Toxic Properties of Novel Starch and Gelatine Blend Bioplastics

by Marta Mroczkowska, Kieran Germaine, David Culliton, Thomais Kakouli Duarte and Adriana Cunha Neves

Recycling 2021, 6(4), 81; https://doi.org/10.3390/recycling6040081 - 16 Dec 2021

Cited by 7 | Viewed by 4829

Abstract

To combat the release of petroleum-derived plastics into the environment the European Commission has adopted the EU plastics strategy, which aims for a complete ban on single-use plastics by 2030. Environmentally friendly and sustainable packaging like bioplastic is being up taken at significant [...] Read more.

To combat the release of petroleum-derived plastics into the environment the European Commission has adopted the EU plastics strategy, which aims for a complete ban on single-use plastics by 2030. Environmentally friendly and sustainable packaging like bioplastic is being up taken at significant levels by companies and consumers. In this study, the environmental impact of novel gelatine–starch blend bioplastics is investigated. The assessments included ecotoxicology with different species that can be found in marine and soil environments to simulate natural conditions. Microalgae, plant, and nematode species were chosen as these are representative of their habitats and are known for their sensitivity to pollutants. Degradation rates of these novel bioplastics were assessed as well as microbiome analysis of the soil before and after bioplastic degradation. The main findings of this study are that (i) the bioplastic generated can be fully biodegraded in soil environments at moderate conditions (20 °C) leaving no physical traces; (ii) bioplastic did not exhibit significantly adverse effects on any organisms assessed in this study; (iii) microbiome analysis of the soil after biodegradation showed a decrease in alpha diversity and a significant increase of Actinobacteria and Firmicutes phyla, which were dominative in the soil. Full article

(This article belongs to the Special Issue Advances in the Recycling and Processing of Plastic Waste)

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13 pages, 1233 KiB

Open AccessArticle

Avoidable Household Food Waste: Diagnosing the Links between Causes and Composition

by Peter J. Shaw

Recycling 2021, 6(4), 80; https://doi.org/10.3390/recycling6040080 - 4 Dec 2021

Cited by 6 | Viewed by 4426

Abstract

Problems associated with the wastage of food intended for human consumption are well known and the discarding of edible but unconsumed food—avoidable food waste—is clearly undesirable. Interventions to reduce avoidable food waste need to be suitably informed: understanding the causes and consequences of [...] Read more.

Problems associated with the wastage of food intended for human consumption are well known and the discarding of edible but unconsumed food—avoidable food waste—is clearly undesirable. Interventions to reduce avoidable food waste need to be suitably informed: understanding the causes and consequences of avoidable food waste is instructive in this regard. One hitherto unexplored approach to understand better the causes of food waste is to elucidate associations between the composition of avoidable food waste and the reasons why it is generated. If such associations can be established, data relating to the composition of avoidable food waste can contribute evidence to underpin interventions intended to prevent or reduce avoidable food waste. The aim of this study was therefore to explore links between the causes of avoidable food waste and its composition, and thereby contribute to the development of management measures. Information relating the commonly reported causes of avoidable food waste and its composition (part-consumed, whole-unused and leftovers) was gathered via a series of participatory workshops involving university students. Outcomes of the workshops indicated that individual causes of avoidable food waste rarely lead exclusively to a single type of avoidable food waste, but some relationships were evident. Five of the 13 causal factors explored were considered to lead to all three types of avoidable food waste; a further five were considered to lead mainly to part-consumed and whole-unused food waste. Potential interventions to effect positive change are explored; the value of classifying avoidable food waste to guide interventions was evident, although approaches would need to be aligned with the observed composition of avoidable food waste and the method(s) of intervention considered. Applications of the approach and outcomes of this study are also considered in a policy context. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members (EBMs) of Recycling)

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8 pages, 2726 KiB

Open AccessCommunication

A Review of Glass Fibre Recycling Technology Using Chemical and Mechanical Separation of Surface Sizing Agents

by Jih-Hsing Chang, Ya-Shiuan Tsai and Pei-Yu Yang

Recycling 2021, 6(4), 79; https://doi.org/10.3390/recycling6040079 - 2 Dec 2021

Cited by 4 | Viewed by 3841

Abstract

Glass fiber is widely used in various modern industrial applications because it has the advantages of good electrical insulation performance and good process ability. Inevitably, some flawed glass fiber generated during manufacturing processes becomes waste and, in recent years, the treatment or recycling [...] Read more.

Glass fiber is widely used in various modern industrial applications because it has the advantages of good electrical insulation performance and good process ability. Inevitably, some flawed glass fiber generated during manufacturing processes becomes waste and, in recent years, the treatment or recycling of glass fiber waste has become an environmental concern. Since glass fiber is brittle, non-wearing, and can easily generate static electricity after friction, the surface of glass fiber must be coated with a wetting agent (i.e., surface sizing agent) to overcome these disadvantages. However, glass fiber waste cannot be directly recycled as glass raw materials due to the presence of the surface sizing agent and the high content of sodium element. Therefore, there is a need to develop a feasible technology for removal of surface sizing agent in order to recycle glass fiber waste. In this study, two methods were used to remove surface sizing agent from glass fiber waste. After removing the surface sizing agent, the treated glass fiber waste can replace sand particles for manufacturing controlled low-strength material (CLSM). The first method for removing surface sizing agent used different organic solvents such as ethyl acetate to dissolve the surface coating (i.e., surface sizing agent). Then, an optical microscope was used to observe the surface changes before and after such removal treatments. The second method involved grinding glass fiber waste into a fine powder and heating it to a high temperature. An X-ray diffractometer (XRD) and X-ray fluorescence (XRF) were used to analyze the surface characteristics of the glass fiber waste. The experimental results showed that different organic solvents could not effectively remove the surface sizing agent, even if the glass fiber waste was processed by ultrasonic vibration for 5 h. In contrast, after high heating at 800 °C for 2 h, the surface sizing agent could be removed, and glass fiber waste transformed to cristobalite. The CLSM concrete produced by mixing cristobalite with cement in an appropriate proportion can meet the CLSM specification standard in Taiwan. Full article

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14 pages, 2427 KiB

Open AccessReview

Recycling of Rubber Wastes as Fuel and Its Additives

by Ahmed Akbas and Nor Yuliana Yuhana

Recycling 2021, 6(4), 78; https://doi.org/10.3390/recycling6040078 - 1 Dec 2021

Cited by 27 | Viewed by 13131

Abstract

Economic, social, and urban developments generally require improvements in the transportation sector, which includes automobiles such as trucks, buses, trailers, airplanes, and even bicycles. All these vehicles use rubber tires. After consumption, these tires become waste, leading to enlarged landfill areas for used [...] Read more.

Economic, social, and urban developments generally require improvements in the transportation sector, which includes automobiles such as trucks, buses, trailers, airplanes, and even bicycles. All these vehicles use rubber tires. After consumption, these tires become waste, leading to enlarged landfill areas for used tires and implying additional harm to the environment. This review summarizes the growth of rubber recycling application and the sustainability of using waste rubber in the construction field. Furthermore, we provide methods to convert rubber waste to fuel or fuel additives by using tire-derived fuel and concentrate to pyrolysis, which are environmentally friendly and efficient ways. The related parameters such as temperature, pressure, and feedstock composition were studied. Most research papers observed that 500 °C is the optimal temperature at atmospheric pressure in the presence of a specific type of catalyst to improve pyrolysis rate, oil yield, and quality. Full article

(This article belongs to the Special Issue Recycling of Rubber Waste)

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21 pages, 1076 KiB

Open AccessArticle

Enhancement of WEEE Management Practices in MTN Phone Village, Rumukurushi, Port Harcourt, Nigeria

by Ogechukwu Okwu, Andrew Hursthouse, Evi Viza and Linus Idoko

Recycling 2021, 6(4), 77; https://doi.org/10.3390/recycling6040077 - 24 Nov 2021

Cited by 2 | Viewed by 3689

Abstract

Informal recycling has been a source of challenges to a mobile telephone network (MTN) phone village in Rumukurushi, Port Harcourt, Nigeria, and several locations in developing countries. In order to bring a lasting solution to the menace of informal recycling in this location, [...] Read more.

Informal recycling has been a source of challenges to a mobile telephone network (MTN) phone village in Rumukurushi, Port Harcourt, Nigeria, and several locations in developing countries. In order to bring a lasting solution to the menace of informal recycling in this location, the study proposed a new waste electrical and electronic equipment (WEEE) management system. The system comprises the application of two key concepts. The first concept includes limiting the activities of informal recyclers to WEEE collection only. This implies WEEE treatment, dismantling, etc., are carried out by government-approved agencies and experts. The second concept involves the application of the just-in-time (JIT) management concept for managing WEEE. The concept ensures that WEEE is only requested from the recycler or the individuals in possession of it and only on demand. The study adopted a qualitative research approach. Data collection and analysis were achieved via semi-structured phone interviews and thematic analysis, respectively. The outcome of the study limits the activities of the informal recyclers to WEEE collection. Informal recyclers gain revenue from collection. A reduction in the waiting time of workers and WEEE storage space is achieved. This offers safety, efficiency, and an increased productivity. This will help to revolutionise the WEEE management system in the location. Full article

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11 pages, 5396 KiB

Open AccessReview

Comparison of Properties with Relevance for the Automotive Sector in Mechanically Recycled and Virgin Polypropylene

by Abdelhak Ladhari, Esra Kucukpinar, Henning Stoll and Sven Sängerlaub

Recycling 2021, 6(4), 76; https://doi.org/10.3390/recycling6040076 - 24 Nov 2021

Cited by 22 | Viewed by 6581

Abstract

Polypropylene (PP) has a high recycling potential. However, the properties of mechanically recycled PP (R-PP) have not been fully compared to those of virgin PP (V-PP). Therefore, in this study, properties of R-PP and V-PP were compared using data from recyclers, virgin plastic [...] Read more.

Polypropylene (PP) has a high recycling potential. However, the properties of mechanically recycled PP (R-PP) have not been fully compared to those of virgin PP (V-PP). Therefore, in this study, properties of R-PP and V-PP were compared using data from recyclers, virgin plastic suppliers, and the literature. The properties of recyclates could not be directly correlated either with the properties of the virgin polymers from which the recyclates were made or the recycling parameters. It was found that the MFR of R-PP was higher; MFR R-PP had a median value (m) of 11 g/10 min while MFR V-PP had a median value of 6.3 g/10 min (at 230 °C and with 2.16 kg). In terms of mechanical properties, in many cases R-PP exhibited stiffer and more brittle behavior, with a slightly higher Young’s modulus (E_R-PP = 1400 and E_V-PP = 1200 MPa), a reduced elongation at break (ɛb_R-PP = 4 l.-% and ɛb_V-PP = 83 l.-%), and notched charpy impact strength (NCIS_R-PP = 4.8 and NCIS_V-PP = 7.5 kJ/m²). However, the values for every property had a broad distribution. In addition to existing information from the literature, our research sheds fresh light on the variation of the characteristics of recycled polypropylenes presently on the market. Full article

(This article belongs to the Special Issue Feature Papers in Recycling 2021)

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18 pages, 4360 KiB

Open AccessArticle

Purchase Intentions for Brazilian Recycled PET Products—Circular Economy Opportunities

by Fernanda Cristina Barbosa Pereira Queiroz, Nilton Cesar Lima, Christian Luiz da Silva, Jamerson Viegas Queiroz and Gustavo Henrique Silva de Souza

Recycling 2021, 6(4), 75; https://doi.org/10.3390/recycling6040075 - 12 Nov 2021

Cited by 14 | Viewed by 5846

Abstract

Circular economy involves structural changes in traditional business models and consumers’ behavior toward recycled products. The recycling of PET products is increasing but there is still a gap between consumption and demand for PET packaging in Brazil. In this research, waste reduction was [...] Read more.

Circular economy involves structural changes in traditional business models and consumers’ behavior toward recycled products. The recycling of PET products is increasing but there is still a gap between consumption and demand for PET packaging in Brazil. In this research, waste reduction was examined under a projective scenario to the current ecological purposes in Brazil for reducing environmental pollution. In that manner, this paper aimed to comprehend the intention to purchase recycled PET products of Brazilian consumers. With a non-probabilistic and convenience sample, the study counts 422 participants. The method employed was based on structural equation modelling and partial least Squares, used to test the hypotheses of causality among the variables. Results showed the perception of low quality about recycled products reduced consumers’ intention to purchase. Additionally, the sustainability of recycled products positively influenced the intention to purchase. In addition, recycled products presented a negative impact on the perceived safety, which could influence the purchase of recycled products in Brazil. We conclude that the image that Brazilian consumers have about recycled products positively affects the intention to purchase. Full article

(This article belongs to the Special Issue Advances in the Recycling and Processing of Plastic Waste)

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19 pages, 849 KiB

Open AccessArticle

Identifying and Evaluating Recirculation Strategies for Industry in the Nordic Countries

by Jutta Hildenbrand, Johan Dahlström, Sasha Shahbazi and Martin Kurdve

Recycling 2021, 6(4), 74; https://doi.org/10.3390/recycling6040074 - 12 Nov 2021

Cited by 4 | Viewed by 3287

Abstract

The manufacturing industry in the Nordic countries aims to include closing product and material loops to recover values in their circular economy strategies. Recirculating strategies for products and materials are required for existing products that are part of the stock and are also [...] Read more.

The manufacturing industry in the Nordic countries aims to include closing product and material loops to recover values in their circular economy strategies. Recirculating strategies for products and materials are required for existing products that are part of the stock and are also anticipated to be aligned with products designed for circularity and circular business models in the future. Options to capture value of discarded products are diverse and include reuse, remanufacturing and material recycling. The Circular Economy Integration in the Nordic Industry for enhanced sustainability and competitiveness (CIRCit) project developed a framework to guide decision makers in the industry on how to identify suitable treatments and subsequent use at the end of use or end of life of a product and how to select among different options. Factors considered in the assessment include technical feasibility, necessary efforts, networks of business partners, legal implications and overall sustainability aspects. Our empirical studies show great support for decision-makers in the value recovery of different products with different complexity levels. It is also concluded that the properties of products at their end of use are the main drivers behind selecting a proper recirculation strategy. This study contributes with an empirical evaluation and a consistent terminology framework for recirculation options. The general setup is relevant for the Nordic countries. Full article

24 pages, 1983 KiB

Open AccessFeature PaperArticle

A Synthesis of Express Analytic Hierarchy Process (EAHP) and Partial Least Squares-Structural Equations Modeling (PLS-SEM) for Sustainable Construction and Demolition Waste Management Assessment: The Case of Malaysia

by Kambiz Ghafourian, Kamyar Kabirifar, Amir Mahdiyar, Maziar Yazdani, Syuhaida Ismail and Vivian W. Y. Tam

Recycling 2021, 6(4), 73; https://doi.org/10.3390/recycling6040073 - 6 Nov 2021

Cited by 33 | Viewed by 6286

Abstract

Construction and demolition waste (CDW), as the main consequence of construction and demolition (C&D) activities, has severely affected our sustainability needs. However, construction and demolition waste management (CDWM) lacks the integration of sustainability concepts. Thus, there is a great need to include sustainability [...] Read more.

Construction and demolition waste (CDW), as the main consequence of construction and demolition (C&D) activities, has severely affected our sustainability needs. However, construction and demolition waste management (CDWM) lacks the integration of sustainability concepts. Thus, there is a great need to include sustainability dimensions in CDWM to reach sustainable construction and demolition waste management (SCDWM). This study aims at empirically investigating SCDWM by analyzing the impacts of factors that contribute to sustainability aspects of CDWM on waste management hierarchy (WMH), including reduce, reuse, recycle, and disposal strategies. According to the literature, 26 factors were initially identified and grouped under four categories, namely environmental, economic, social, and administrative, that contribute to sustainability aspects of CDWM. Subsequently, a pilot test was performed to assess the significance and applicability of these factors in the Malaysian construction industry by implementing the express analytic hierarchy process (EAHP). Then, a questionnaire survey was performed to collect data from 132 construction companies involved in CDWM. Partial least squares-structural equation modeling (PLS-SEM) was used to test the hypothetical relationships by applying SmartPLS software. Results demonstrated that the economic aspect of CDWM (main category) and “public environment contamination due to illegal waste dumping” (sub-category) were the most influential factor in SCDWM in Malaysia. Full article

(This article belongs to the Special Issue Using Circular Economy Principles to Manage Construction Waste)

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18 pages, 2491 KiB

Open AccessFeature PaperArticle

Recycling of Waste Fiber-Reinforced Plastic Composites: A Patent-Based Analysis

by Beatrice Colombo, Paolo Gaiardelli, Stefano Dotti, Flavio Caretto and Gaetano Coletta

Recycling 2021, 6(4), 72; https://doi.org/10.3390/recycling6040072 - 5 Nov 2021

Cited by 14 | Viewed by 5195

Abstract

Fiber-reinforced plastic composite materials are increasingly used in many industrial applications, leading to an increase in the amount of waste that must be treated to avoid environmental problems. Currently, the scientific literature classifies existing recycling technologies into three macro-categories: mechanical, thermal, and chemical; [...] Read more.

Fiber-reinforced plastic composite materials are increasingly used in many industrial applications, leading to an increase in the amount of waste that must be treated to avoid environmental problems. Currently, the scientific literature classifies existing recycling technologies into three macro-categories: mechanical, thermal, and chemical; however, none are identified as superior to the others. Therefore, scholars and companies struggle to understand where to focus their efforts. Patent analysis, by relying on quantitative data as a precursor to new technological developments, can contribute to fully grasping current applications of each recycling technology and provide insights about their future development perspectives. Based on these premises, this paper performs a patent technology roadmap to enhance knowledge about prior, current, and future use of the main recycling technologies. The results show that recycling macro-categories have different technology maturity levels and growth potentials. Specifically, mechanical recycling is the most mature, with the lowest growth potential, while thermal and chemical recycling are in their growth stage and present remarkable future opportunities. Moreover, the analysis depicts several perspectives for future development on recycling technologies applications within different industries and underline inter- and intra-category dependencies, thus providing valuable information for practitioners and both academic and non-academic backgrounds researchers interested in the topic. Full article

(This article belongs to the Special Issue Feature Papers in Recycling 2021)

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14 pages, 248 KiB

Open AccessArticle

The Impact of a Rural School-Based Solid Waste Management Project on Learners’ Perceptions, Attitudes and Understanding of Recycling

by Busisiwe Mkhonto and Lindelani Mnguni

Recycling 2021, 6(4), 71; https://doi.org/10.3390/recycling6040071 - 3 Nov 2021

Cited by 4 | Viewed by 11696

Abstract

Continued environmental degradation necessitates innovative strategies to improve society’s attitude towards and understanding of recycling solid waste. Previous research has shown that school-based projects integrated into the school curriculum could effectively enhance learners’ knowledge of recycling and attitudes towards recycling. However, not much [...] Read more.

Continued environmental degradation necessitates innovative strategies to improve society’s attitude towards and understanding of recycling solid waste. Previous research has shown that school-based projects integrated into the school curriculum could effectively enhance learners’ knowledge of recycling and attitudes towards recycling. However, not much is known about the impact of such projects if they are driven by learners, particularly in under-resourced rural schools. Therefore, in the current research, we aimed to determine the impact of a school-based recycling project, integrated as practical work, on learners’ understanding of recycling, their attitude towards recycling, and the perceived impact of the project on the school environment, in an under-resourced rural school. Our findings showed that participating in a rural school-based recycling project may not enhance Grade 7 Natural Sciences learners’ perceptions of, attitudes towards, and understanding of recycling. We posit that various factors may affect the effectiveness of a recycling project. Further research is required to explore these factors further. Full article

(This article belongs to the Special Issue Feature Papers in Recycling 2021)

12 pages, 2979 KiB

Open AccessArticle

Recycling of WEEE Plastics Waste in Mortar: The Effects on Mechanical Properties

by Alessandra Merlo, Luca Lavagna, Daniel Suarez-Riera and Matteo Pavese

Recycling 2021, 6(4), 70; https://doi.org/10.3390/recycling6040070 - 22 Oct 2021

Cited by 7 | Viewed by 3487

Abstract

This work focused on the recycling of WEEE plastic waste as a partial substitute for aggregate in light mortars. The plastic mix, provided by the IREN group, was used as a replacement of aggregate in 15, 30, 45, 60, 75, and 90%_vol [...] Read more.

This work focused on the recycling of WEEE plastic waste as a partial substitute for aggregate in light mortars. The plastic mix, provided by the IREN group, was used as a replacement of aggregate in 15, 30, 45, 60, 75, and 90%_vol in mortars. Worsening of the mechanical performance of around 50% was detected already at only 15%_vol of mineral aggregate substituted with plastic waste. The explanation of this phenomenon was found in both the scarce mechanical properties of the used plastic and in the poor adhesion between matrix and plastics that resulted in extra-porosity formation, as also demonstrated by comparing the results with several models in the literature. However, the use of plastic waste as a partial replacement of natural aggregate contributes to the preservation of natural resources and, in any case, does not limit the application of these materials in non-structural applications. Full article

(This article belongs to the Special Issue Advances in the Recycling and Processing of Plastic Waste)

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22 pages, 18225 KiB

Open AccessReview

Informing the Public and Educating Students on Plastic Recycling

by Ethan M. Bennett and Paschalis Alexandridis

Recycling 2021, 6(4), 69; https://doi.org/10.3390/recycling6040069 - 21 Oct 2021

Cited by 24 | Viewed by 27076

Abstract

Approximately 300 million tons of plastic waste is generated per year. The major portion of this plastic waste is landfilled, while part of it leaks into the environment. When plastic waste enters the terrestrial or aqueous environment, it can have negative impacts on [...] Read more.

Approximately 300 million tons of plastic waste is generated per year. The major portion of this plastic waste is landfilled, while part of it leaks into the environment. When plastic waste enters the terrestrial or aqueous environment, it can have negative impacts on ecosystems, human health, and wildlife. Increasing the amount of plastic waste that is recycled will correspondingly reduce the amount of plastic waste that enters the environment. By educating the public and industry on plastic recycling, current recycling programs can be used more efficiently, and new programs can be created. Education material on plastic recycling is available through professional and industry associations, foundations with an environmental focus, university courses, and short courses offered with private companies. This review assembles and analyzes the current education material on plastic recycling that is available from these providers. The material compiled here can be used to gain insight into specific plastic recycling-related topics, to identify areas of recycling education that can be improved, and as a resource to help build university level courses. There is currently a dearth of plastic recycling courses offered at the university level. Educating more students on plastic recycling will equip them with the knowledge and skills to make informed decisions as consumers, and to implement plastic recycling systems at the professional level. Full article

(This article belongs to the Special Issue Advances in the Recycling and Processing of Plastic Waste)

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10 pages, 2838 KiB

Open AccessArticle

Variation of Used Vegetable Oils’ Composition upon Treatment with Algerian Clays

by Abdelhak Serouri, Zoubida Taleb, Alberto Mannu, Sebastiano Garroni, Nina Senes, Safia Taleb, Sara Brini and Sabrine Kawther Abdoun

Recycling 2021, 6(4), 68; https://doi.org/10.3390/recycling6040068 - 19 Oct 2021

Cited by 4 | Viewed by 3698

Abstract

The treatment of used vegetable oils (UVOs) with clays represents a pivotal step in their industrial recycling process as well as one of the most challenging topics for researchers. In particular, cheap, effective, and sustainable powders need to be explored in order to [...] Read more.

The treatment of used vegetable oils (UVOs) with clays represents a pivotal step in their industrial recycling process as well as one of the most challenging topics for researchers. In particular, cheap, effective, and sustainable powders need to be explored in order to develop new processes which produce beneficial results in relation to economic and environmental aspects. In this context, five samples within commercial and waste vegetable oils were treated with two sodium- and calcium-based bentonites employing a low oil/bentonite ratio (0.15 wt%). The outcomes of the processes were monitored by FT-IR spectroscopy and compared with the data relative to the parent commercial edible oil. In particular, treatment of FT-IR data by multivariate statistical analysis allowed us to determine a chemical fingerprint characteristic of each sample. Important relationships between the overall chemical composition and the specific clay employed and the treatment time (2 or 4 h) were highlighted. Finally, N₂ physisorption, TEM microscopy, and FT-IR analyses of the more efficient Na bentonite allowed us to characterize the material and thus to furnish all the information needed to set-up a general protocol for the partial regeneration of waste vegetable oil destined for further processing. Full article

(This article belongs to the Special Issue Recycling and Recovery of Biomass Materials II)

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13 pages, 3535 KiB

Open AccessArticle

Recovery of Ag, Au, and Pt from Printed Circuit Boards by Pressure Leaching

by Guadalupe Martinez-Ballesteros, Jesus Leobardo Valenzuela-García, Agustin Gómez-Alvarez, Martin Antonio Encinas-Romero, Flerida Adriana Mejía-Zamudio, Aaron de Jesús Rosas-Durazo and Roberto Valenzuela-Frisby

Recycling 2021, 6(4), 67; https://doi.org/10.3390/recycling6040067 - 13 Oct 2021

Cited by 11 | Viewed by 3906

Abstract

Reclamation of printed circuit boards (PCBs) to recover metals is gaining growing attention due to minerals being non-renewable resources. Currently, metals extraction from PCBs through an efficient and green method is still under investigation. The present investigation concerns the recycling of printed circuit [...] Read more.

Reclamation of printed circuit boards (PCBs) to recover metals is gaining growing attention due to minerals being non-renewable resources. Currently, metals extraction from PCBs through an efficient and green method is still under investigation. The present investigation concerns the recycling of printed circuit boards using hydrometallurgical processes. First, the basic metals (Cu, Ni, Zn and Fe) were separated using a sulfuric acid solution at moderate temperatures. The remaining solids were characterized by SEM-EDS, whereby a high content of precious metals (Au, Ag and Pt) was observed. In the second stage, solids were leached with a solution of HCl and NaClO in a 1-L titanium reactor with varied oxygen pressure (0.2, 0.34 and 0.55 MPa), temperature (40, 50 and 80 °C) and concentration of HCl (2 and 4 M), obtaining extractions above 95% at [HCl] = 4 M, P = 0.34 MPa and T = 40 °C. The extraction increased depending on the concentration of HCl. Eh–pH diagrams for Ag–Cl–H₂O, Au–Cl–H₂O and Pt–Cl–H₂O were constructed to know the possible species in the solution. Full article

(This article belongs to the Special Issue Hydrometallurgical Recycling of Critical Metals from End-of-Life Devices)

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10 pages, 6358 KiB

Open AccessArticle

High-Shear De-Gassing and De-Ironing of an Aluminum Casting Alloy Made Directly from Aluminum End-of-Life Vehicle Scrap

by Kawther Al-Helal, Jaime Lazaro-Nebreda, Jayesh B. Patel and Geoff M. Scamans

Recycling 2021, 6(4), 66; https://doi.org/10.3390/recycling6040066 - 9 Oct 2021

Cited by 10 | Viewed by 4040

Abstract

High-shear melt conditioning (HSMC) technology was used for degassing and de-ironing of an aluminum alloy recovered from the Zorba cast fraction of the non-ferrous scrap from shredded end-of-life vehicles. The results showed that the recovery of aluminum alloys from the Zorba cast fraction [...] Read more.

High-shear melt conditioning (HSMC) technology was used for degassing and de-ironing of an aluminum alloy recovered from the Zorba cast fraction of the non-ferrous scrap from shredded end-of-life vehicles. The results showed that the recovery of aluminum alloys from the Zorba cast fraction was more than 80%. High-shear melt conditioning improved the degassing process during melt treatment in comparison with the adding of degassing tablets. The efficiency of the de-ironing process using HSMC increased by up to 24% after, increasing the Mn content to 0.8% in the melt. Adding Mn to Zorba melt enhanced the de-ironing process and eliminated the formation of β-AlFeSi intermetallic particles, which have a detrimental effect on both the mechanical and corrosion properties of the alloy. Full article

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15 pages, 1518 KiB

Open AccessArticle

Waste Management System Fraud Detection Using Machine Learning Algorithms to Minimize Penalties Avoidance and Redemption Abuse

by Ali Hewiagh, Kannan Ramakrishnan, Timothy Tzen Vun Yap and Ching Seong Tan

Recycling 2021, 6(4), 65; https://doi.org/10.3390/recycling6040065 - 4 Oct 2021

Cited by 3 | Viewed by 4330

Abstract

Online frauds have pernicious impacts on different system domains, including waste management systems. Fraudsters illegally obtain rewards for their recycling activities or avoid penalties for those who are required to recycle their own waste. Although some approaches have been introduced to prevent such [...] Read more.

Online frauds have pernicious impacts on different system domains, including waste management systems. Fraudsters illegally obtain rewards for their recycling activities or avoid penalties for those who are required to recycle their own waste. Although some approaches have been introduced to prevent such fraudulent activities, the fraudsters continuously seek new ways to commit illegal actions. Machine learning technology has shown significant and impressive results in identifying new online fraud patterns in different system domains such as e-commerce, insurance, and banking. The purpose of this paper, therefore, is to analyze a waste management system and develop a machine learning model to detect fraud in the system. The intended system allows consumers, individuals, and organizations to track, monitor, and update their performance in their recycling activities. The data set provided by a waste management organization is used for the analysis and the model training. This data set contains transactions of users’ recycling activities and behaviors. Three machine learning algorithms, random forest, support vector machine, and multi-layer perceptron are used in the experiments and the best detection model is selected based on the model’s performance. Results show that each of these algorithms can be used for fraud detection in waste managements with high accuracy. The random forest algorithm produces the optimal model with an accuracy of 96.33%, F1-score of 95.20%, and ROC of 98.92%. Full article

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11 pages, 1059 KiB

Open AccessArticle

How COVID-19 Could Change the Economics of the Plastic Recycling Sector

by Ibrahim Issifu, Eric Worlanyo Deffor and Ussif Rashid Sumaila

Recycling 2021, 6(4), 64; https://doi.org/10.3390/recycling6040064 - 26 Sep 2021

Cited by 12 | Viewed by 7475

Abstract

The price of oil has a great influence on prices of recycled plastics and, therefore, plastic recycling efforts. Here, we analyze the effects of the ongoing COVID-19 pandemic on crude oil price and how this, in turn, is likely to affect the degree [...] Read more.

The price of oil has a great influence on prices of recycled plastics and, therefore, plastic recycling efforts. Here, we analyze the effects of the ongoing COVID-19 pandemic on crude oil price and how this, in turn, is likely to affect the degree of plastic recycling that takes place. Impulse response functions and variance decompositions, calculated from the structural vector autoregression, suggest that changes in crude oil prices are key drivers of the price of recycled plastics. The findings highlight that because plastics are made from the by-products of oil, falling oil prices increase the cost of recycling. Therefore, the price of recycled plastics should be supported using taxes while encouraging sustained behavioral changes among consumers and producers to selectively collect and recycle personal protective equipment so that they do not clog our landfills or end up in our water bodies as plastic waste. Full article

(This article belongs to the Special Issue Advances in the Recycling and Processing of Plastic Waste)

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16 pages, 2347 KiB

Open AccessArticle

Multistage Constructed Wetland in the Treatment of Greywater under Tropical Conditions: Performance, Operation, and Maintenance

by Fernando J. C. Magalhães Filho, José C. M. de Souza Filho and Paula L. Paulo

Recycling 2021, 6(4), 63; https://doi.org/10.3390/recycling6040063 - 26 Sep 2021

Cited by 7 | Viewed by 4355

Abstract

Greywater (GW) can be separated in different fractions where the kitchen component might be included. Constructed wetland (CW) systems are commonly used for the onsite treatment of GW, and the fraction treated might impact the performance, operation, and maintenance. These aspects are still [...] Read more.

Greywater (GW) can be separated in different fractions where the kitchen component might be included. Constructed wetland (CW) systems are commonly used for the onsite treatment of GW, and the fraction treated might impact the performance, operation, and maintenance. These aspects are still poorly explored in the literature and are of importance for a proper design and system sustainability. In this study, a multi-stage household-scale CW system composed of a horizontal flow (HF), followed by a vertical flow (VF) unit, was monitored over 1330 days, focusing on different GW fractions and hydraulic and organic loading rates. The biochemical oxygen demand (BOD) was ~50% lower without the kitchen sink component (GW_L) in the system inlet, while no drop was observed in the chemical oxygen demand (COD). Treatment with the GW_L component caused a sudden drop in the hydraulic loading rate applied at the HF-CW (~114 to 35 mm per day) and the VF-CW (~230 to 70 mm per day). Even when the HF-CW received ~90 gCOD m⁻² per day (GW), the multistage system reached a COD removal of 90%. The lower BOD load when treating GW_L avoids clogging and decreases the frequency of maintenance. These variables can be used for the optimal design and operation of a CW, contributing with empirical data to CW guidelines in Brazil, and could additionally be expanded for application in other countries with similar climates. Full article

(This article belongs to the Special Issue Reuse of Wastewater: Recovery of Water, Nutrients, and Energy)

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Recycling, Volume 6, Issue 4 (December 2021) – 20 articles

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