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Recycling, Volume 9, Issue 1 (February 2024) – 20 articles

Cover Story (view full-size image): Second-generation biomass feedstocks have immense potential in terms of creating a more sustainable future and shifting the paradigm from conventional carbon-intensive resources to carbon-neutral renewable resources. Unlocking the full potential of second-generation biomass feedstocks is essential to creating a sustainable future. By refining these waste feedstocks through biorefining, a nexus of biofuels, biochemicals, and biomaterials can be created. This is a sustainable approach to transform low-value residues into high-value industrial products with a target to reduce waste generation and greenhouse gas emissions. This innovative approach reduces our reliance on finite fossil fuels and promotes a circular economy where waste is converted into valuable resources for our inustries and societies. View this paper
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15 pages, 1960 KiB  
Article
Analysis of Essential Features and Optimal Operational Parameters of an RF-ICP Torch for Waste Treatment Applications
by Mustafa A. Aldeeb, Sharif Abu Darda, Vahid Damideh, Isaac Hassen and Hossam A. Gabbar
Recycling 2024, 9(1), 20; https://doi.org/10.3390/recycling9010020 - 15 Feb 2024
Viewed by 1529
Abstract
Recently, plasma-based pyrolysis has gained increasing prominence as a technology in response to the growing challenges in waste disposal and the recognition of opportunities to generate valuable by-products. The efficiency of the pyrolysis process is intricately tied to the characteristics of the plasma [...] Read more.
Recently, plasma-based pyrolysis has gained increasing prominence as a technology in response to the growing challenges in waste disposal and the recognition of opportunities to generate valuable by-products. The efficiency of the pyrolysis process is intricately tied to the characteristics of the plasma involved, particularly the effective electron temperature (Teff) and plasma density (ne). This study aimed to conduct a comprehensive examination of the essential features and optimal operational parameters of a developed RF-ICP torch specifically designed for small-scale municipal solid waste (MSW) pyrolysis (mixture of paper and polypropylene) with the goal of controlling both the torch and the overall process. Using optical emission spectroscopy (OES), we measured plasma parameters, specifically (Teff) and (ne), while varying argon gas flow rates and RF powers. The (Teff) and (ne)were determined using the Boltzmann plot and Stark broadening, respectively. The RF torch was found to generate (ne) up to approximately 2.8×1020 cm3 and (Teff) up to around 8200 K, with both parameters being controlled by the discharge power and gas flow rate. Additionally, a power-losing mechanism, namely the anomalous skin effect, was detected during the study, which is uncommon in atmospheric plasma discharge. Full article
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19 pages, 1706 KiB  
Review
Drivers and Barriers in the Production and Utilization of Second-Generation Bioethanol in India
by Falguni Pattnaik, Biswa R. Patra, Sonil Nanda, Mahendra K. Mohanty, Ajay K. Dalai and Jaya Rawat
Recycling 2024, 9(1), 19; https://doi.org/10.3390/recycling9010019 - 09 Feb 2024
Cited by 1 | Viewed by 1520
Abstract
Second-generation biorefinery refers to the production of different types of biofuels, biomaterials, and biochemicals by using agri-based and other lignocellulosic biomasses as substrates, which do not compete with arable lands, water for irrigation, and food supply. From the perspective of transportation fuels, second-generation [...] Read more.
Second-generation biorefinery refers to the production of different types of biofuels, biomaterials, and biochemicals by using agri-based and other lignocellulosic biomasses as substrates, which do not compete with arable lands, water for irrigation, and food supply. From the perspective of transportation fuels, second-generation bioethanol plays a crucial role in minimizing the dependency on fossil-based fuels, especially gasoline. Significant efforts have been invested in the research and development of second-generation bioethanol for commercialization in both developing and developed countries. However, in different developing countries like India, commercialization of second-generation bioethanol has been obstructed despite the abundance and variety of agricultural feedstocks. This commercial obstruction was majorly attributed to the recalcitrance of the feedstock, by-product management, and marginal subsidies compared to other nations. This article reviews the major roadblocks to the viability and commercialization of second-generation biofuels, especially bioethanol in India and a few other leading developed and developing nations. This article also reviews the biomass availability, technological advancements, investments, policies, and scale-up potential for biorefineries. A thorough discussion is made on the prospects and barriers to research, development, and demonstration as well as strengths, weaknesses, opportunities, and threats for the commercialization of second-generation bioethanol. Full article
(This article belongs to the Special Issue Resource Recovery from Waste Biomass)
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18 pages, 3014 KiB  
Article
Performance of the Food Waste Recycling Law in Japan with Reference to SDG 12.3
by Tomoko Okayama and Kohei Watanabe
Recycling 2024, 9(1), 18; https://doi.org/10.3390/recycling9010018 - 08 Feb 2024
Viewed by 1689
Abstract
SDG target 12.3 calls for halving food waste in retail, food service, and households by 2030. The food waste index developed for this purpose includes parts attached to food that are usually removed intentionally (“unavoidable food waste”) and counts conversion into animal feed [...] Read more.
SDG target 12.3 calls for halving food waste in retail, food service, and households by 2030. The food waste index developed for this purpose includes parts attached to food that are usually removed intentionally (“unavoidable food waste”) and counts conversion into animal feed and utilisation as biomaterial as a means of reduction. In Japan, the “Food Waste Recycling Law”, which has been in effect since 2001, promotes the recycling of food waste generated from businesses, designating feed conversion as a top priority. On the other hand, based on the more recent “Food Loss Reduction Promotion Act” of 2019, the government is currently promoting reduction in avoidable food waste to meet the SDG target. Based on statistical sources and interviews with ministry officers, this paper explains the history and achievements of Japan’s 23-year policy based on the Food Recycling Law, as well as the tension between the two legislations. Full article
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20 pages, 9879 KiB  
Review
A Critical Review on the Application of Recycled Carbon Fiber to Concrete and Cement Composites
by Manan Bhandari and Il-Woo Nam
Recycling 2024, 9(1), 17; https://doi.org/10.3390/recycling9010017 - 07 Feb 2024
Viewed by 1360
Abstract
Carbon fiber (CF) exhibit extraordinary properties, such as high specific and tensile strength, high elastic modulus, light weight, and weather resistance, which has led to a rapid increase in the use of CF in sectors such as aerospace, sports equipment, energy storage, automotive, [...] Read more.
Carbon fiber (CF) exhibit extraordinary properties, such as high specific and tensile strength, high elastic modulus, light weight, and weather resistance, which has led to a rapid increase in the use of CF in sectors such as aerospace, sports equipment, energy storage, automotive, construction, and wind energy applications. However, the increase in CF applications has led to a massive production of CF waste. As CF is non-biodegradable, it results in CF accumulation in landfills. CF waste is a rapidly growing ecological hazard because of its high energy consumption and expensive production methods. The properties of carbon fibers can be preserved even after recycling given the development of recycling technology; therefore, multiple studies have been conducted to demonstrate the effect of recycled carbon fiber (RCF) in different composites such as cement-based composites. This review presents the results of studies conducted on the application of RCF to cement composites and analyzes those results to investigate the effect of RCF on the properties of cement composites such as mechanical properties (compressive strength, flexural strength, and tensile strength), fracture characteristics (fracture toughness and fracture energy), electrical properties, and workability. Overall, the studies demonstrated a positive trend in the application of RCF to cement composites. Full article
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19 pages, 4295 KiB  
Article
Geopolymerization of Recycled Glass Waste: A Sustainable Solution for a Lightweight and Fire-Resistant Material
by Marios Valanides, Konstantinos Aivaliotis, Konstantina Oikonomopoulou, Alexandros Fikardos, Pericles Savva, Konstantinos Sakkas and Demetris Nicolaides
Recycling 2024, 9(1), 16; https://doi.org/10.3390/recycling9010016 - 07 Feb 2024
Viewed by 1438
Abstract
Glass is considered a sustainable material with achievable recovery rates within the EU. However, there are limited data available for construction glass waste management. Furthermore, glass is a heavy material, and considering the geographical limitations of Cyprus, the transportation trading cost within the [...] Read more.
Glass is considered a sustainable material with achievable recovery rates within the EU. However, there are limited data available for construction glass waste management. Furthermore, glass is a heavy material, and considering the geographical limitations of Cyprus, the transportation trading cost within the EU is extremely high. Therefore, another method for utilizing this by-product should be developed. The aim of this research is to investigate the production of a low-cost, lightweight and fireproof material able to retain its structural integrity, using the geopolymerization method with the incorporation of randomly collected construction glass waste. The glass waste was initially processed in a Los Angeles abrasion machine and then through a Micro-Deval apparatus in order to be converted to a fine powder. Mechanical (compressive and flexural strength), physical (setting time and water absorption) and thermal properties (thermal conductivity) were investigated. The fire-resistant materials presented densities averaging 450 kg/m3 with a range of compressive strengths of 0.5 to 3 MPa. Additionally, a techno-economic analysis was conducted to evaluate the viability of the adopted material. Based on the results, the final geopolymer product has the potential to be utilized as a fire resistance material, preventing yielding or spalling. Full article
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18 pages, 2240 KiB  
Article
Optimization of Pyrolysis Process Parameters for Fuel Oil Production from the Thermal Recycling of Waste Polypropylene Grocery Bags Using the Box–Behnken Design
by Balasubramaniam Prabha, Desikan Ramesh, Srinivasan Sriramajayam and Doraiswamy Uma
Recycling 2024, 9(1), 15; https://doi.org/10.3390/recycling9010015 - 06 Feb 2024
Cited by 1 | Viewed by 2436
Abstract
The impact of dumping plastic waste is realized in different ecosystems of the planet. Several methods have been adopted to dispose of these wastes for energy recovery. This study, for the first time, proposed the Box–Behnken design technique to optimize the pyrolysis process [...] Read more.
The impact of dumping plastic waste is realized in different ecosystems of the planet. Several methods have been adopted to dispose of these wastes for energy recovery. This study, for the first time, proposed the Box–Behnken design technique to optimize the pyrolysis process parameters for fuel oil production from waste polypropylene (PP) grocery bags using a semibatch-type pyrolytic reactor. The semibatch-type pyrolytic reactor was developed and employed to produce fuel oil from waste PP grocery bags. The effect of different process parameters on fuel oil production was comprehensively analyzed using the response surface methodology (RSM) with the conjunction of the Box–Behnken design (BBD). The BBD facilitates the prediction of the response variables with respect to changes in the input variables by developing a response model. The BBD was used to optimize the process parameters, such as the reaction temperature (400–550 °C), nitrogen flow rate (5–20 mL min−1), and substrate feed rate (0.25–1.5 kg h−1), and their effect on the responses were observed. The optimum response yields of the fuel oil (89.34 %), solid residue (2.74%), and gas yield (7.92%) were obtained with an optimized temperature (481 °C), a nitrogen flow rate (13 mL min−1), and a feed rate (0.61 kg h−1). The quadratic model obtained for the fuel oil response denotes the greater R2 value (0.99). The specific gravity and calorific value of the fuel oil were found to be 0.787 and 45.42 MJ kg−1, respectively. The fuel oil had higher research octane number (RON) (100.0 min) and motor octane number (MON) (85.1 min) values. These characteristics of the fuel oil were matched with conventional petroleum fuels. Further, Fourier transform infrared spectroscopy (FT-IR) and gas chromatography–mass spectroscopy (GC-MS) were used to analyze the fuel oil, and the results revealed that the fuel oil was enriched with different hydrocarbons, namely, alkane (paraffins) and alkene (olefins), in the carbon range of C4–C20. These results, and also the fractional distillation of the fuel oil, show the presence of petroleum-range hydrocarbons in the waste PP fuel oil. Full article
(This article belongs to the Special Issue Feature Papers in Recycling 2023)
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23 pages, 21163 KiB  
Article
Effect of Surface Condition on the Results of Chemical Composition Measurements of Scrap Copper Alloys
by Łukasz Bernat, Tomasz Jurtsch, Grzegorz Moryson, Jan Moryson and Grzegorz Wiczyński
Recycling 2024, 9(1), 14; https://doi.org/10.3390/recycling9010014 - 04 Feb 2024
Viewed by 1303
Abstract
The processing of copper-bearing scrap makes it possible to reduce the costs and energy consumption of obtaining copper alloy products compared to producing them from primary raw materials. To achieve this, it is necessary to quickly and accurately determine the content of alloying [...] Read more.
The processing of copper-bearing scrap makes it possible to reduce the costs and energy consumption of obtaining copper alloy products compared to producing them from primary raw materials. To achieve this, it is necessary to quickly and accurately determine the content of alloying elements in individual scrap elements. However, the copper-bearing scrap obtained at secondary raw materials collection points consists of elements with various surface conditions (due to contamination, shape, paint coatings, roughness, etc.). The paper contains research results on the influence of surface roughness and paint coatings on the measurement result of the content of alloying elements in copper-bearing scrap. Three mobile spectrometers were used for measurements: spark-induced optical emission spectroscopy (OES), X-ray fluorescence spectrometry (XRF) and laser-induced breakdown spectroscopy (LIBS). The tests used elements with different surface roughness (from Ra = 0.03 μm to 6.7 μm) and covered with various types of varnish (alkyd, water-based, oil-phthalic, acrylic, oil-alkyd). It was found that the roughness of Ra < 2 μm does not significantly affect the results of the measurements with the OES and LIBS spectrometers, and a larger scatter of measurement results was observed for the XRF spectrometer compared to OES and LIBS. For Ra > 2 μm, a significant impact of roughness was found on the measurement results (this may result in the erroneous classification of the scrap as an incorrect material group). The influence of paint coatings on the measurement is much stronger compared to surface roughness. Even a single layer of paint can cause a change in the measurement result of the content of alloying elements by more than 10%. In the case of an OES spectrometer, paint coatings may prevent the measurement from being performed (which means that no measurement result can be acquired). Full article
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24 pages, 956 KiB  
Review
Battery Waste Management in Europe: Black Mass Hazardousness and Recycling Strategies in the Light of an Evolving Competitive Regulation
by Mattia Gianvincenzi, Enrico Maria Mosconi, Marco Marconi and Francesco Tola
Recycling 2024, 9(1), 13; https://doi.org/10.3390/recycling9010013 - 04 Feb 2024
Viewed by 1669
Abstract
The increasing significance of batteries in the 21st century and the challenges posed by the anticipated surge in end-of-life batteries, particularly within the European context, are examined in this study. Forecasts predict a notable escalation in battery waste, necessitating a focus on the [...] Read more.
The increasing significance of batteries in the 21st century and the challenges posed by the anticipated surge in end-of-life batteries, particularly within the European context, are examined in this study. Forecasts predict a notable escalation in battery waste, necessitating a focus on the recycling of black mass (BM)—a complex and hazardous byproduct of the battery recycling process. Employing systematic analysis, this research investigates the hazardous nature of BM derived from various battery types. The study underscores the urgent need for definitive legislative classification of BM’s hazardous properties (HPs), in accordance with European regulations. This comprehensive examination of BM’s HPs contributes significantly to the understanding of BM recycling complexities, proving essential for industry stakeholders and guiding future developments in this field. Additionally, the study explores innovative technologies and strategies that could improve recycling efficiency and reduce associated risks. A pivotal finding of this investigation is the inherently hazardous nature of BM, leading to the recommendation that BM should be classified at a minimum under the “HP3—Flammable” category. This discovery underscores the critical need for stringent management protocols and robust regulatory frameworks to address the burgeoning challenge of battery waste in Europe. Full article
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15 pages, 5171 KiB  
Article
Using Cassava Starch Processing By-Product for Bioproduction of 1-Hydroxyphenazine: A Novel Fungicide against Fusarium oxysporum
by Tu Quy Phan, San-Lang Wang, Thi Hanh Nguyen, Thi Huyen Nguyen, Thi Huyen Thoa Pham, Manh Dung Doan, Thi Ha Trang Tran, Van Anh Ngo, Anh Dzung Nguyen and Van Bon Nguyen
Recycling 2024, 9(1), 12; https://doi.org/10.3390/recycling9010012 - 02 Feb 2024
Viewed by 1275
Abstract
This study aimed to develop the eco-friendly production of bioactive 1-hydroxyphenazine (HP) through fermentation using an industrial processing by-product of cassava as the main carbon/nitrogen source. Cassava starch processing by-product (CSPB) was screened as a suitable substrate for fermentation to produce HP [...] Read more.
This study aimed to develop the eco-friendly production of bioactive 1-hydroxyphenazine (HP) through fermentation using an industrial processing by-product of cassava as the main carbon/nitrogen source. Cassava starch processing by-product (CSPB) was screened as a suitable substrate for fermentation to produce HP with a high yield. Mixing CSPB with a minor amount of tryptic soy broth (TSB) at a ratio of 8/2 and with 0.05% K2HPO4 and 0.05% FeSO4 was effective in HP production by Pseudomonas aeruginosa TUN03. HP was also further scaled up through production on a bioreactor system, which achieved a higher level yield (36.5 µg/mL) in a shorter fermentation time (10 h) compared to its production in the flask (20.23 µg/mL after 3 days). In anti-fungal activity tests against various Fusarium phytopathogens, HP exhibited the most significant effect on Fusarium oxysporum F10. It could inhibit the mycelial growth of this fungus, with an inhibition rate of 68.7% and anti-spore germination activity of up to 98.4%. The results of the docking study indicate that HP effectively interacted with the protein 1TRY targeting anti-F. oxysporum, with all obtained docking parameters in the accepted range. This study supports the novel use of CSPB as the carbon/nitrogen source for P. aeruginosa fermentation to produce HP, a F. oxysporum anti-fungal agent reported here for the first time. Full article
(This article belongs to the Special Issue Resource Recovery from Waste Biomass)
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14 pages, 4388 KiB  
Article
Carbon Fiber Composites Recycling Technology Enabled by the TuFF Technology
by Tekin Ozdemir, Joseph M. Deitzel, Roger Crane, Shridhar Yarlagadda, Chris Blackwell, Mark Davis, Rebecca Emmerich and Dirk Heider
Recycling 2024, 9(1), 11; https://doi.org/10.3390/recycling9010011 - 02 Feb 2024
Viewed by 1583
Abstract
Carbon Fiber Composites (CFCs) recycling has received increasing interest by the composites industry, but it is still in its early stages as an industry. There are two primary challenges that need to be addressed in order to achieve full property retention during CFC [...] Read more.
Carbon Fiber Composites (CFCs) recycling has received increasing interest by the composites industry, but it is still in its early stages as an industry. There are two primary challenges that need to be addressed in order to achieve full property retention during CFC recycling: (1) the ability to recover the fiber content without property loss; and (2) conversion of the recycled, short fiber material back into high-performance CFC structures. The ability to manufacture high fiber volume fraction CFCs with end-of-life products would provide an opportunity to reduce material cost and lifetime-embodied energy. In this paper, recycled, short carbon fibers are processed via solvolysis and converted into high-performance CFCs with fiber volume fraction of ~50% and excellent composite property retention. This is enabled through alignment of the discontinuous, recycled fiber feedstock using the Tailorable universal Feedstock for Forming (TuFF) process. The paper introduces the necessary steps to process the fibers in the wet-laid process and explores the resulting mechanical and microstructural properties. The importance of incoming fiber surface quality and the effect of surface contamination from residue left by the recycling process on both the TuFF process and final composite properties is discussed in detail. A pyrolytic process has been adopted to remove the residue that is a by-product of the recycling process from the incoming recycled fiber surface. The approach presents a promising pathway for the recycling of high-performance CFCs. Full article
(This article belongs to the Special Issue Feature Papers in Recycling 2023)
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13 pages, 2106 KiB  
Article
Evaluation of the Landfill Storage Capacity in Slovakia, Compared to the EU Situation
by Zuzana Šimková, Marcela Taušová, Katarína Čulková, Peter Tauš, Danylo Shyp, David Krasniči and Simona Novotná
Recycling 2024, 9(1), 10; https://doi.org/10.3390/recycling9010010 - 27 Jan 2024
Viewed by 1621
Abstract
The circular economy and efficient use of resources gained importance in the context of sustainable development. The paper aims to evaluate the development of landfilling in Slovakia. The next goal is to assess the trend in compared with the EU’s situation. The presented [...] Read more.
The circular economy and efficient use of resources gained importance in the context of sustainable development. The paper aims to evaluate the development of landfilling in Slovakia. The next goal is to assess the trend in compared with the EU’s situation. The presented research presents a continuation of previous research in the area of waste recycling in Slovakia, pointing to the waste and landfilling, which is deserving of analysis from a long-term perspective. The research is carried out via data collection at the EU level by recording continuously published values. The paper’s results are processed in statistical software. Considering regional development, landfilling in Slovakia is followed up according to the geographical units of the entire country. The results shown here show that a higher recycling capacity is required and Slovakia should decrease its level of landfill. Such results can be used in the waste treatment area, protection of the living environment and sustainable development of regions. Full article
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26 pages, 2819 KiB  
Review
A Comprehensive Review of Lithium-Ion Battery (LiB) Recycling Technologies and Industrial Market Trend Insights
by Bowen He, Han Zheng, Karl Tang, Ping Xi, Muqing Li, Laiwei Wei and Qun Guan
Recycling 2024, 9(1), 9; https://doi.org/10.3390/recycling9010009 - 26 Jan 2024
Cited by 1 | Viewed by 2340
Abstract
Adopting EVs has been widely recognized as an efficient way to alleviate future climate change. Nonetheless, the large number of spent LiBs associated with EVs is becoming a huge concern from both environmental and energy perspectives. This review summarizes the three most popular [...] Read more.
Adopting EVs has been widely recognized as an efficient way to alleviate future climate change. Nonetheless, the large number of spent LiBs associated with EVs is becoming a huge concern from both environmental and energy perspectives. This review summarizes the three most popular LiB recycling technologies, the current LiB recycling market trend, and global recycling magnates’ industrial dynamics regarding this subject. We mainly focus on reviewing hydrometallurgical and direct recycling technologies to discuss the advancement of those recycling technologies and their future commercialization pathway. Full article
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20 pages, 2656 KiB  
Review
Evolution, Prospects, and Predicaments of Polymers in Marine Applications: A Potential Successor to Traditional Materials
by Aravind Dhandapani, Senthilkumar Krishnasamy, Senthil Muthu Kumar Thiagamani, Diwahar Periasamy, Chandrasekar Muthukumar, Thirumalai Kumaran Sundaresan, Saood Ali and Rendi Kurniawan
Recycling 2024, 9(1), 8; https://doi.org/10.3390/recycling9010008 - 22 Jan 2024
Viewed by 1774
Abstract
Polymers are ideal solutions for architects and constructors in the marine field who require materials that can achieve light and stable structures owing to their unique advantages. For instance, they possess a high strength-to-weight ratio, high wear resistance and fatigue strength, resistance to [...] Read more.
Polymers are ideal solutions for architects and constructors in the marine field who require materials that can achieve light and stable structures owing to their unique advantages. For instance, they possess a high strength-to-weight ratio, high wear resistance and fatigue strength, resistance to corrosion, ease of fabrication, and superior vibration damping behavior. These properties make polymers well suited for marine-based applications. However, polymers have their disadvantages, such as contributing to plastic pollution, which has a detrimental impact on the environment. In recent times, various concurrent methods have been employed to advance the future of polymers. This review explores (i) an overall view of polymers used in marine industries, (ii) a focus on reducing plastic wastage, (iii) challenges involved in recycling polymers and ensuring their sustainability, and (iv) the development of renewable plastics. Full article
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35 pages, 5668 KiB  
Article
Hygrothermal Optimization for Excavated Soil Reuse in Various Climate Buildings: A Global Literature Meta-Analysis
by Yannick Igor Fogue Djombou, Melvyn Gorra and Bruno Malet-Damour
Recycling 2024, 9(1), 7; https://doi.org/10.3390/recycling9010007 - 22 Jan 2024
Viewed by 1550
Abstract
This article investigates the hygrothermal properties of earth-based materials by analyzing experimental data from 88 articles spanning 32 countries worldwide. The focus is determining effective techniques for leveraging the use of excavated soil in construction, particularly emphasizing enhancement of hygrothermal comfort in specific [...] Read more.
This article investigates the hygrothermal properties of earth-based materials by analyzing experimental data from 88 articles spanning 32 countries worldwide. The focus is determining effective techniques for leveraging the use of excavated soil in construction, particularly emphasizing enhancement of hygrothermal comfort in specific climates. Based on statistical analysis, the study presents a comprehensive classification of earth production techniques, incorporating additives, and examines their impacts on hygrothermal properties of excavated soils. Additionally, it explores the intricate relationship between the climatic conditions of a region and the chosen earth-material production techniques. The analysis aims to propose standard parameters for earthen materials and identify gaps in both methods and experimental studies. Therefore, this study will provide valuable insights by proposing new design tools (ternary diagrams) to maximize the use of excavated soils in construction practices. The proposed diagrams illustrate the intricate relation linking either hygrothermal properties, the climate zone, and manufacturing techniques, or the relation between the most studied manufacturing techniques (compaction, fibered, and stabilization) and expected dry thermal conductivity. Thereby, results from this meta-analysis and critical review will contribute to advancing sustainable construction practices. Full article
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15 pages, 3179 KiB  
Article
Two-Step Bio-Dissolution of Metals from Printed Circuit Boards Using Acidophilic Iron- and Sulfur-Oxidizing Mesophiles
by Kundani Magoda, Philiswa N. Nomngongo and Lukhanyo Mekuto
Recycling 2024, 9(1), 6; https://doi.org/10.3390/recycling9010006 - 18 Jan 2024
Viewed by 1658
Abstract
To date, electronic waste (e-waste) is the fastest-growing waste stream worldwide due to technological advancement and the advent of the Fourth Industrial Revolution. Although e-waste is an environmental hazard, these materials are considered good secondary sources of metals. This study examined the bioleaching [...] Read more.
To date, electronic waste (e-waste) is the fastest-growing waste stream worldwide due to technological advancement and the advent of the Fourth Industrial Revolution. Although e-waste is an environmental hazard, these materials are considered good secondary sources of metals. This study examined the bioleaching of metals from printed circuit boards, where a two-step bioleaching approach was used with iron–sulfur-oxidizing microorganisms at different e-waste particle sizes. The metal analysis from the different particle sizes (PSs) showed that copper (Cu), tin (Sn), and lead (Pb) were predominantly deposited in the coarser fraction, ranging from 500 to 710 µm at 28.7, 20.5, and 11.1 wt.%, respectively. On the other hand, metals such as iron (Fe), zinc (Zn), manganese (Mn), nickel (Ni), and aluminum (Al) were mostly deposited in the finer fraction, which ranged from 38 to 150 µm at 37.3, 5.9, 8.8, 1.3, and 4.2 wt.%, respectively. After the bioleaching process, it was observed that higher metal extraction occurred at a PS ranging from 38 to 150 µm, which achieved recovery efficiency rates of 62.9%, 68.2%, 95.3%, 86.1%, 61.9%, 47.2%, 21.2%, and 63.6% for Al, Cu, Fe, Mn, Ni, Pb, Sn, and Zn, respectively, over 10 days. Full article
(This article belongs to the Special Issue Recovery of Valuable Metals and Nonmetals from E-Waste)
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18 pages, 2378 KiB  
Article
Degradation of Plastic Materials through Small-Scale Pyrolysis: Characterization of the Obtained Hydrocarbons and Life Cycle Analysis
by José Alfredo Torres Tovar, Hermelinda Servín-Campuzano, Mauricio González-Avilés, Hugo Sobral and Francisco Javier Sánchez-Ruiz
Recycling 2024, 9(1), 5; https://doi.org/10.3390/recycling9010005 - 15 Jan 2024
Viewed by 1713
Abstract
Plastic waste signifies a global predicament, aggravated by deficient management practices. Unearthing methods to repurpose energy from this waste is pivotal. This study delves into the pyrolytic degradation of low-density plastics to convert plastic waste into valuable products on a modest scale. A [...] Read more.
Plastic waste signifies a global predicament, aggravated by deficient management practices. Unearthing methods to repurpose energy from this waste is pivotal. This study delves into the pyrolytic degradation of low-density plastics to convert plastic waste into valuable products on a modest scale. A small-scale, low-CO2 emitting distiller was employed in the process. A zeolite was harnessed as a catalyst to augment the temperature and hasten the pyrolysis process. A comprehensive life cycle analysis was executed to assess the environmental impact of the process. In this scenario, zeolite-facilitated pyrolysis was more proficient compared to traditional thermal pyrolysis, generating a yield of 22.5% with the catalyst, contrasting with 18% without. A kinetic model was formulated, observing reaction mechanisms and temperature escalation and culminating in the extraction of aromatic oils. These oils were further distilled to produce liquid hydrocarbons, beginning the distillation at 60 °C with the catalyst. Characterization of the secured hydrocarbons was conducted using infrared, Raman spectroscopy, and gas chromatography, discovering compounds akin to gasoline, such as benzene, toluene, and xylenes. Additionally, the procedure exhibited a minimal environmental detriment, as validated by the life cycle analysis. This study concludes by highlighting the potential of small-scale, low-CO2 emitting pyrolytic degradation of low-density plastics for energy recovery from plastic waste, demonstrating the practical and environmental benefits of this avant-garde method. Full article
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19 pages, 3559 KiB  
Article
The Potential Material Flow of WEEE in a Data-Constrained Environment—The Case of Jordan
by Laila A. Al-Khatib and Feras Y. Fraige
Recycling 2024, 9(1), 4; https://doi.org/10.3390/recycling9010004 - 09 Jan 2024
Viewed by 1913
Abstract
The rising concerns about electric and electronic equipment waste (WEEE) come from the rapid increase in demand for appliances and the decreasing lifetimes of equipment. Setting a sustainable WEEE management system that exploits this secondary resource is paramount to maximize resource efficiency, mitigate [...] Read more.
The rising concerns about electric and electronic equipment waste (WEEE) come from the rapid increase in demand for appliances and the decreasing lifetimes of equipment. Setting a sustainable WEEE management system that exploits this secondary resource is paramount to maximize resource efficiency, mitigate its environmental impact, and stimulate the circular economy. This paper aims, for the first time, to quantify the material flow expected from recycling the generated WEEE, propose the number of plants required to recycle this secondary resource, and outline the expected economic and environmental benefits that could be achieved from recycling operations. The findings of material flow calculations show that the amount of steel, copper, and aluminum is predominant in the WEEE composition. Also, the expected metal content in WEEE in 2022 is approximately 26 kt, 3.3 kt, and 2.5 kt, respectively. These are expected to substantially increase to approximately 109 kt, 11.9 kt, and 9 kt for the three metals in 2050, respectively. Other valuable metals are doubling their quantities between 2022 and 2050 to reach approximately 1133 kg silver and 475 kg gold. Approximately, four treatment plants are required to recover these materials in 2030 with relative installation costs of USD 100 million. The forecasted financial revenues of recovering materials included in WEEE and indicators for environmental impact based on life cycle assessment (LCA) are calculated. The results of this study can serve as a preliminary reference for future usage in guiding effective planning for WEEE recycling and sustainable management in the country. Full article
(This article belongs to the Special Issue Recovery of Valuable Metals and Nonmetals from E-Waste)
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17 pages, 3206 KiB  
Article
Improvement of Thermal Protection in Recycled Polyolefins through Hybrid Mesoporous Silica–Antioxidant Particles
by Enrique Blázquez-Blázquez, Rosa Barranco-García, Tamara M. Díez-Rodríguez, Pilar Posadas, Ernesto Pérez and María L. Cerrada
Recycling 2024, 9(1), 3; https://doi.org/10.3390/recycling9010003 - 02 Jan 2024
Viewed by 1970
Abstract
The deficient management of plastic waste has caused a serious worldwide environmental problem. Thus, one of the main challenges for the industry in the plastics sector in contributing to sustainability and a circular economy consists of providing a subsequent service life to this [...] Read more.
The deficient management of plastic waste has caused a serious worldwide environmental problem. Thus, one of the main challenges for the industry in the plastics sector in contributing to sustainability and a circular economy consists of providing a subsequent service life to this waste. For that purpose, the appropriate incorporation of antioxidants will play a key role in preventing or postponing the degradation of plastic waste, where the formation of radicals is initiated during its previous lifetime by the action of degrading agents. Functionalized particles, based on mesoporous MCM-41 silica with Irganox 1076, were prepared with two different protocols and were further incorporated into a material containing virgin PP and 30 wt.% of recycled PP, with the purpose of guaranteeing thermal stability during its next service life. A very significant increase in the thermal stability of the resulting composites was found, attributable to the synergistic action between the Irganox 1076 antioxidant and the MCM-41 particles. In addition, the presence of hybrid particles leads to an important nucleating effect for the crystallization of PP. Moreover, a reinforcing role was also played by these modified mesoporous silicas in the resultant systems. The presented methodology constitutes, therefore, a promising strategy for contributing to the circular economy—since the synergy between the Irganox 1076 antioxidant and MCM-41 particles was found to play an important role in the ultimate performance of recycled polyolefins. Full article
(This article belongs to the Special Issue Advances in the Recycling, Processing and Use of Plastic Waste II)
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11 pages, 1440 KiB  
Article
Reforming Construction Waste Management for Circular Economy in Kazakhstan: A Cost–Benefit Analysis of Upgrading Construction and Demolition Waste Recycling Centres
by Ferhat Karaca and Aidana Tleuken
Recycling 2024, 9(1), 2; https://doi.org/10.3390/recycling9010002 - 29 Dec 2023
Viewed by 1754
Abstract
This paper investigates the advantages of enhancing construction and demolition waste (CDW) recycling facilities to conform to circular economy (CE) models in Kazakhstan’s construction sector. The industry is experiencing significant growth due to urbanization, but it faces difficulties managing CDW, frequently resulting in [...] Read more.
This paper investigates the advantages of enhancing construction and demolition waste (CDW) recycling facilities to conform to circular economy (CE) models in Kazakhstan’s construction sector. The industry is experiencing significant growth due to urbanization, but it faces difficulties managing CDW, frequently resulting in landfill disposal. In response, this paper provides a cost–benefit analysis of upgrading the CDW recycling centres aligned with CE needs. Reflecting legislative changes in Kazakhstan’s Environmental Code, which prohibited CDW in landfills starting December 2020, the initiative to establish modern CDW recycling centres is gaining momentum in major cities. The primary objective is to maximize material recovery and eliminate contaminants that curtail the utilization of recycled sand and aggregate products. The analysis yields compelling results, indicating that the project has the potential to recycle up to 84 million tons of CDW over eight years, with an annual 25% capacity increase and a maximum possible 95% recycling efficiency. Despite an estimated cost of USD 48 million, the project demonstrates a payback period of 9.9 years, signalling eventual cost recovery. These findings underscore the project’s capacity to mitigate CDW issues while generating economic benefits and contributing to a sustainable environment. In conclusion, implementing modern CDW recycling centres in Kazakhstan represents a potent solution for the construction industry as it transitions toward a CE model. This transition addresses both pressing environmental challenges and promising economic prospects. Full article
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13 pages, 3642 KiB  
Article
Sustainable WPC Production: A Novel Method Using Recycled High-Density Polyethylene and Wood Veneer
by Leslie Cristell Canto-Borges, Julio César Cruz, Javier Rodrigo Nahuat-Sansores, José Antonio Domínguez-Lepe and Mayra Polett Gurrola
Recycling 2024, 9(1), 1; https://doi.org/10.3390/recycling9010001 - 28 Dec 2023
Viewed by 1667
Abstract
This research work is focused on the development of an alternative method for manufacturing Wood Plastic Composite (WPC) panels based on Wood Veneers (WVs) and High-Density Polyethylene (HDPE) through compression molding, which enhances the physical properties, particularly, water absorption and moisture content. The [...] Read more.
This research work is focused on the development of an alternative method for manufacturing Wood Plastic Composite (WPC) panels based on Wood Veneers (WVs) and High-Density Polyethylene (HDPE) through compression molding, which enhances the physical properties, particularly, water absorption and moisture content. The aim of the present research was to develop alternative panels to replace commercial ones, which are heavily affected by hot, humid climates. In this context, the study began with the design process, which consisted of the collection and processing of primary material, production of the additional components necessary for the manufacturing process, determination of the WV ratio, and preparation of the samples. Thereafter, physical and mechanical tests were carried out on WPC, HDPE (control), commercial gypsum boards (GBs), plywood (PW), and medium density fiberboard (MDF) samples. The results indicate that the method applied to manufacture the WPC samples improved physical properties, achieving a water uptake of less than 4% in both proportions of replacement tested, in contrast to commercial panels, which reached values between 10% and 40%. In addition, a greater load capacity was achieved for lower thick elements. Full article
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