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ISSN (Online) 2313-4321
Published by MDPI Homepage  [258 journals]
  • Recycling, Vol. 8, Pages 29: Circular Construction Indicator: Assessing
           Circularity in the Design, Construction, and End-of-Life Phase

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

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

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

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

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

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

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

    • Authors: Christiam Méndez-Lazarte, Victor W. Bohorquez-Lopez, Carlos Caycho-Chumpitaz, Alfredo Estrada-Merino
      First page: 36
      Abstract: Facilitating solid waste separating behavior at home continues to be a challenge for municipal programs in emerging economies. Large cities concentrate the generation of solid waste and, in Latin America, a great percentage of this waste is not re-used. Therefore, in this research, we explore the drivers motivating solid waste separation at home in Lima. We applied 450 surveys in two municipalities of Lima and analyzed the results through Structural Equation Modeling (SEM). The results demonstrate that attitude, perception of technical knowledge, and availability of physical space influence solid waste separation behavior. Additionally, the mediating role of intention between solid waste separation attitude and behavior is demonstrated. Municipal solid waste recycling programs in emerging economies tend to focus on educational and motivational actions, without giving due importance to space at home in order to manage solid waste. The lack of urban equipment and the limited availability of space at home introduce barriers that limit solid waste separating behaviors in emerging economies.
      Citation: Recycling
      PubDate: 2023-03-13
      DOI: 10.3390/recycling8020036
      Issue No: Vol. 8, No. 2 (2023)
  • Recycling, Vol. 8, Pages 7: Development and Evaluation of Sustainable
           Bituminous Paver Blocks

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    • Authors: Aziza Athumani Konyo, Revocatus Machunda, Liliane Pasape, Anthony Mshandete
      First page: 1
      Abstract: The use of sisal decorticated waste (SDW) for various applications is limited due to its high acidic content. This is the first study of its kind regarding the use of SDW as a substrate for the growth of the black soldier fly (BSF). Pre-treatment was a necessary and challenging step performed on the waste to meet the minimum requirements for the rearing of BSF. The SDW was sun dried, sieved, and decomposited and neutralized to form the final products that were used for the rearing of BSF. The resultant waste had fourteen (14) elements; the essential elemental form results were Ca, P, K, Mn, Fe, Cu, and Zn at varying levels, which are all essential for animal growth. The SDW contained 10 ± 0.01 percent of crude protein, 11 ± 0.02 moisture and energy (1615 kcal/g of sisal decorticated waste). The sun dried BSF larvae were reared on SDW that contained 53 ± 0.005 percent of crude protein, 4 ± 0.01 percent of crude fat, a moisture content of (10 ± 0.1)%, carbohydrate percent of (43 ± 0.01)%, and ash percent of (37 ± 0.08). When rearing was finished, 3000 g of dried pre-treated waste yielded more wet BSF larvae, (336 ± 41.3) g, compared to 3000 g of fruit waste, which yielded (244 ± 4.16) g of wet BSF larvae. Therefore, based on this study, SDW is a promising potential feed for rearing BSF because it had a better reduction of the waste by 52%. Furthermore, the harvested BSF larvae contained sufficient nutritional value to feed poultry and fish.
      Citation: Recycling
      PubDate: 2022-12-23
      DOI: 10.3390/recycling8010001
      Issue No: Vol. 8, No. 1 (2022)
  • Recycling, Vol. 8, Pages 2: Blending Recycled High-Density Polyethylene
           HDPE (rHDPE) with Virgin (vHDPE) as an Effective Approach to Improve the
           Mechanical Properties

    • Authors: Jian Zhang, Valerian Hirschberg, Denis Rodrigue
      First page: 2
      Abstract: The mechanical properties of virgin/recycled high-density polyethylene (HDPE) blends over the complete concentration range was thoroughly investigated in this work. In particular, a focus was made on the long-term properties via mechanical fatigue. Two different mixing methods, namely powder mixing (dry blending) and extrusion mixing (melt blending), were used to determine the effect of processing conditions on the tensile and fatigue behavior of the blends after compression molding. It was found that both tensile (modulus, ultimate strength) and fatigue performances were improved with increasing vHDPE content. Based on the obtained data, a correlation between the blends composition and mechanical properties is reported. Moreover, it was observed that increasing the vHDPE content led to slower crack propagation rate, probably due to less defects (contamination) in the blends. Finally, a negligible difference in mechanical properties (fatigue resistance) between both mixing approaches was observed, but samples produced via powder mixing showed less viscous dissipation (heat generation) as the vHDPE content increased, leading to lower surface temperature rise which can be an advantage for specific applications.
      Citation: Recycling
      PubDate: 2022-12-26
      DOI: 10.3390/recycling8010002
      Issue No: Vol. 8, No. 1 (2022)
  • Recycling, Vol. 8, Pages 3: Biological Pretreatment Effects on the
           Bioconversion of Brewer Spent Grain with Hermetia illucens Larvae

    • Authors: Martha Sumba-Zhongor, Eduardo Álava, Luis Galarza, Johana Ortiz-Ulloa, Eduardo J. Chica, Omar Ruiz-Barzola, Julia Nieto-Wigby, Maria Isabel Jiménez-Feijoo, Malena Torres-Ulloa
      First page: 3
      Abstract: Hermetia illucens is an important species for waste management and the circular economy. The aim of this study was to analyze the effects of Trichoderma reesei C2A and Pleurotus sp. as pretreatments of brewer spent grain (BSG). BSG was inoculated with fungal solution or distilled water (control). After seven days, this was used for H. illucens larvae cultivation. At the end of bioconversion process, parameters of substrate reduction and H. illucens larval development were evaluated. Chemical properties of BSG, frass and larvae were also analyzed. With T. reesei C2A pretreatment, highest substrate reduction (46.3 ± 0.9%) was achieved, but larval growth rate was lower (1.0 ± 0.1 mg/d) than that of control (2.8 ± 0.2 mg/d). Larvae of Pleurotus sp. pretreatment had limited development, reflected in their negative growth rate (−0.6 ± 0.2 mg/d). In conclusion, cultivation of H. illucens larvae (six day old) on BSG pretreated with Pleurotus sp. is not recommended. On the other hand, T. reesei C2A pretreatment enhance BSG reduction, and its potential use for lignocellulosic waste management should be more explored.
      Citation: Recycling
      PubDate: 2022-12-27
      DOI: 10.3390/recycling8010003
      Issue No: Vol. 8, No. 1 (2022)
  • Recycling, Vol. 8, Pages 4: An Analysis of the Circular Economy Practices
           of Pesticide Container Waste in Pakistan

    • Authors: Ali Raza, Syed Asif Ali Naqvi, Muhammad Abuzar Mehdi, Muhammad Usman, Sadia Ali, Ashfaq Ahmad Shah, Bilal Hussain
      First page: 4
      Abstract: Empty pesticide container recycling helps control nonpoint source pollution and provides alternative sources for basic materials. This article investigates end users’ adoption of recycling their pesticide container waste and investigates the determinants influencing their adoption. The study uses an extensive farm survey of 210 farmers from the District Faisalabad of the Province of Punjab (Pakistan). It applies the partial least squares structural equation modeling technique to assess the impact of different elements, such as subjective norms, attitude, perceived behavioral control, intention, and environmental concerns, on end users’ adoption regarding recycling of pesticide empty container waste. The results explain that perceived behavioral control and intention to reuse pesticide container waste positively predict end users’ adoption. Furthermore, adoption is positively impacted by attitude, subjective norms, and environmental concerns via the intention to recycle pesticide container waste. The study urges the need to encourage end users to share responsibility for pesticide container waste management for a sustainable society.
      Citation: Recycling
      PubDate: 2022-12-27
      DOI: 10.3390/recycling8010004
      Issue No: Vol. 8, No. 1 (2022)
  • Recycling, Vol. 8, Pages 5: Use of Biomass Ash in Reinforced Clayey Soil:
           A Multiscale Analysis of Solid-State Reactions

    • Authors: Maximiliano Fastelli, Costanza Cambi, Azzurra Zucchini, Paola Sassi, Elia Pandolfi Balbi, Leonardo Pioppi, Franco Cotana, Gianluca Cavalaglio, Paola Comodi
      First page: 5
      Abstract: Clayey soils are treated with binding agents to improve their mechanical properties, as these soils are widely used in construction. The production of binding agents is an energy-intensive process and emits significant amounts of CO2. In addition, the interest in recycling industry waste materials has increased, and the management of significant waste from biomass power plants remains an issue. We used three biomass ashes derived from pellet, olive, and grapevine combustion as stabilizing agents of a clayey soil. The mechanical effects of the treatment on clay-ash mixtures were evaluated using confined compressive tests. The mixtures’ chemo-mineralogical evolution was evaluated through X-ray powder diffraction and quantitative Rietveld analysis, Fourier transform infrared spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy coupled with scanning electron microscopy (EDS-SEM). The FT-IR spectra showed an evolution of the Si-O-Si/Al features, with shifting band positions due to polymerization of the tetrahedral units. The EDS-SEM analysis showed an evolution of the Ca/Si distribution and the growth of pozzolanic reaction products, such as C-S-H nanocrystals and gels. This evidence confirms that the pozzolanic reaction occurs by dissolution of clay minerals and/or the amorphous phase of the ash, which affects the macroscopic behavior of clayey soils in terms of stiffening and strengthening, as confirmed by mechanical tests, albeit these effects are non-homogenous and continuous.
      Citation: Recycling
      PubDate: 2022-12-29
      DOI: 10.3390/recycling8010005
      Issue No: Vol. 8, No. 1 (2022)
  • Recycling, Vol. 8, Pages 6: Release of PAH from Secondary Products Made
           from End-of-Life Tire Recyclates into 20% Aqueous Ethanol as Assessment of
           Human Dermal Absorption

    • Authors: Stefan Hoyer, Lothar Kroll, Benny Fischer, Kai Pisulla, Albrecht Seidel
      First page: 6
      Abstract: Compliance with the legal limits set at the European level for the content of polycyclic aromatic hydrocarbons (PAH), which are harmful to human health and the environment, is of central importance for the recycling of rubber, particularly end-of-life tires (ELT), into secondary products, e.g., elastic fall protection mats or anti-slip mats for the transport sector. However, different regulations associated with different analytical methods apply to newly produced tires on the one hand and secondary products made from ELT on the other. Given these discrepancies, ELT can potentially contain levels of PAH, which can be problematic when reused in consumer products. The total PAH content, however, is not without doubt a reliable risk indicator, which should ultimately be based primarily on the transfer of the substances from the product into the skin of human beings or their release into the environment. Accordingly, additional studies are required to determine the extent to which migration-based measurements are more suitable for risk assessment and how the PAH content correlates with migration. Complementing the recently published results of PAH content in different types of ELT, this study investigates the release of PAH for a range of typical secondary materials composed entirely or partly of ELT. In the present study, migration tests with 20% aqueous ethanol were applied, a methodology that has been shown in previous investigations by others to reflect human skin exposure well, and the resulting migration rates of PAH are determined.
      Citation: Recycling
      PubDate: 2022-12-30
      DOI: 10.3390/recycling8010006
      Issue No: Vol. 8, No. 1 (2022)
  • Recycling, Vol. 7, Pages 81: The Application of Artificial Intelligence in
           the Effective Battery Life Cycle in the Closed Circular Economy
           Model—A Perspective

    • Authors: Agnieszka Pregowska, Magdalena Osial, Weronika Urbańska
      First page: 81
      Abstract: Global pollution of the environment is one of the most challenging environmental problems. Electronic-based population and anthropogenic activity are the main reasons for dramatically increasing the scale of waste generation, particularly battery waste. Improper battery waste disposal causes harmful environmental effects. Due to the release of heavy metals, battery waste affects ecosystems and health. We are faced with the challenge of effective battery waste management, especially recycling, to prevent the depletion of natural resources and maintain ecological balance. Artificial Intelligence (AI) is practically present in all areas of our lives. It enables the reduction of the costs associated with various types of research, increases automation, and accelerates productivity. This paper reviews the representative research progress of effective Artificial Intelligence-based battery waste management in the context of sustainable development, in particular, the analysis of current trends, algorithm accuracy, and data availability. Finally, the future lines of research and development directions of human-oriented Artificial Intelligence applications both in the battery production process and in battery waste management are discussed.
      Citation: Recycling
      PubDate: 2022-11-07
      DOI: 10.3390/recycling7060081
      Issue No: Vol. 7, No. 6 (2022)
  • Recycling, Vol. 7, Pages 82: Environmental Impact Assessment of
           Construction Waste Recycling versus Disposal Scenarios Using an LCA-BIM
           Tool during the Design Stage

    • Authors: Carmen Llatas, Rocío Quiñones, Nuria Bizcocho
      First page: 82
      Abstract: The scientific community has revealed the environmental benefits of recycling construction waste (CW) versus its disposal, and its contribution to circularity. The Life Cycle Assessment (LCA) method enables the environmental impact of CW management to be quantified and facilitates the comparison of recycling versus alternative disposal scenarios. However, due to its complexity, LCA is seldom used by technicians during the design phase, which constitutes a crucial stage in the prevention of environmental impacts. This paper therefore proposes an LCA-based tool, integrated into the Building Information Modelling (BIM) methodology, that helps designers to automate the environmental assessment of recycling versus disposal. The CW-LCA-BIM tool uses impact factors obtained from an LCA model applied to CW and was applied to the structural system of a building in Spain. Up to 99% of the non-hazardous waste was recyclable or reusable. The management of three types of recyclable waste was assessed: concrete (27.2 t), plastics (4.2 t), and steel (1.5 t). Recycling is shown to be the best option since it prevents 1.4 times (14.6 t) the emissions of the disposal scenario and saves 85 times (148.5 GJ) its energy consumption. This tool can be developed in other waste management systems and infrastructures. It can be useful both for designers for the reduction of the environmental impact of their buildings, and for policy managers for waste-prevention policies.
      Citation: Recycling
      PubDate: 2022-11-07
      DOI: 10.3390/recycling7060082
      Issue No: Vol. 7, No. 6 (2022)
  • Recycling, Vol. 7, Pages 83: How Do Industrial Ecology, Energy Efficiency,
           and Waste Recycling Technology (Circular Economy) Fit into China’s
           Plan to Protect the Environment' Up to Speed

    • Authors: Sasmoko Sasmoko, Muhammad Zaheer Akhtar, Haroon ur Rashid Khan, Sriyanto Sriyanto, Mohd Khata Jabor, Awais Rashid, Khalid Zaman
      First page: 83
      Abstract: The challenges of environmental protection are especially prevalent in South and Southeast Asian nations, which adversely affects their sustainable developmental goals. During the last two decades, increased industrialization and urbanization have caused massive air pollution, particularly in the most industrialized and densely populated countries. Due to China’s fast economic expansion and development, the demand for natural resources has increased, resulting in climate change, biodiversity loss, soil degradation, and environmental risks. China’s ecological footprint has been the subject of little investigation on the premises of a circular economy. This study used a literature review methodology on the critical key factors that hinder or facilitate the transition of a linear economy towards a circular economy. Further, based on the literature review, this study used industrial ecology, energy efficiency, and waste recycling technology factors to analyze the role of the circular economy on the country’s environmental sustainability agenda for the period of 1975–2020. The results show that in the short run, the link between ecological footprints and per capita income is monotonically decreasing; however, in the long run, the relationship is U-shaped. In both the short and long run, waste recycling technology and cleaner manufacturing significantly decrease ecological footprints. Renewable energy consumption increases ecological footprints in the short run but decreases them in the long run. The management of natural resources reduces ecological footprints to support the ‘resource blessing’ hypothesis. The Granger causality corroborated the unidirectional relationship between ecological footprints, oil rents, and urbanization and ecological footprints. In addition, economic growth Granger causes industrialization and waste recycling technology while green energy Granger causes economic growth, industrialization, and recycling technology. The two-way link between economic development and urbanization exists within a nation. The variance decomposition analysis (VDA) predicts that in the future, China’s natural resources, green energy demand, and technological spillover will limit its ecological footprint through material and technology efficiency.
      Citation: Recycling
      PubDate: 2022-11-07
      DOI: 10.3390/recycling7060083
      Issue No: Vol. 7, No. 6 (2022)
  • Recycling, Vol. 7, Pages 84: Mineral Carbonation of Basic Oxygen Furnace

    • Authors: Daniel Vollprecht, Dominik Wohlmuth
      First page: 84
      Abstract: Mineral carbonation is a method in carbon capture and utilization (CCU) in which carbon dioxide reacts with natural or synthetic mineral phases to form carbonates. In this study, BOF slag consisting of alite, Ca3SiO5, belite, Ca2SiO4, melilite, (Ca,Na)2(Mg,Al)[Si2O7], brownmillerite, Ca(Fe,Al)2O5, calcium ferrite, Ca2FeO4 and Ca-, Mg- and Mn-bearing wuestite, (Mg,Ca,Mn,Fe)O, was crushed into different particle size fractions and exposed over various durations (1 d, 3 d, 9 d, 14 d, 24 d) at a grate to 120 °C hot off-gas with a CO2 content of 25%. However, the total inorganic carbon (TIC) content never increases above the detection limit of 0.5% throughout the experimental duration. The determination of the carbonation depth using phenolphthalein does not reveal a homogeneous carbonation front, but an irregular carbonation. This observation was confirmed by microprobe analyses using elemental mapping. The solubility of the slag increases with increasing carbonation, e.g., the leachability of sulfate increases from 7.8 to 8270 mg/kg dry matter (DM), and of calcium from 940 to 3860 mg/kg DM. The leaching of environmentally relevant element varies: the leachable concentration of molybdenum increases from 0.017 mg/kg DM to 0.089 mg/kg DM, that of chromium remains constant (ca. 0.05 mg/kg DM) whereas that of vanadium decreases from 1.1 to 0.45 mg/kg. In summary, the chosen carbonation technology must be improved to enhance carbonate yield.
      Citation: Recycling
      PubDate: 2022-11-07
      DOI: 10.3390/recycling7060084
      Issue No: Vol. 7, No. 6 (2022)
  • Recycling, Vol. 7, Pages 85: Asbestos Waste Treatment—An Effective
           Process to Selectively Recover Gold and Other Nonferrous Metals

    • Authors: Omirserik Baigenzhenov, Alibek Khabiyev, Brajendra Mishra, Indira Aimbetova, Sultan Yulusov, Inkar Temirgali, Yerzhan Kuldeyev, Zhanar Korganbayeva
      First page: 85
      Abstract: We investigated the potential of tailings generated from chrysotile asbestos fiber production as a source of iron, nonferrous metals, and gold. We proposed the use of granulometric separation and systematically examined different enrichment processes, namely magnetic separation, gravity concentration, and enrichment using a Knelson concentrator, to extract the valuable components. The characterization of the initial tailing samples revealed that it comprises primarily of serpentine, brucite, antigorite, hematite, vustite, sillimanite, and magnesium oxide. Using the suggested enrichment process, we isolated gold, chromite, and nickel-cobalt concentrates as valuable products in addition to magnetite. The new approach exhibited high separation efficiency for iron, nonferrous metals, and gold, allowing their satisfactory extraction.
      Citation: Recycling
      PubDate: 2022-11-17
      DOI: 10.3390/recycling7060085
      Issue No: Vol. 7, No. 6 (2022)
  • Recycling, Vol. 7, Pages 86: Kinetics of Zn–C Battery Leaching with
           Choline Chloride/Urea Natural Deep Eutectic Solvents

    • Authors: Irlanda G. Cruz-Reyes, Jorge A. Mendoza-Pérez, Rosario Ruiz-Guerrero, Dulce Y. Medina-Velázquez, Luis G. Zepeda-Vallejo, Ángel de J. Morales-Ramírez
      First page: 86
      Abstract: A choline chloride/urea natural deep eutectic solvent (ChCl NADES) was prepared via a green chemistry method and used to leach Zn and Mn oxides from conventional Zn–C scrap batteries. FTIR and 1H NMR spectroscopy were used to characterize the NADES. The leaching kinetics of the Zn and Mn oxides was monitored at isothermal conditions (80, 100, 125, and 150 °C) and at two solid/NADES ratios: 3.3 and 10 g dm−3. It was possible to dissolve Zn and Mn oxides under all of tested conditions, reaching more than a 95% recovery for both metals at 150 °C after 90 min, whereas, at 25 °C, it was possible to leach up to 90% of the Zn and 30% of the Mn after 4320 min (72 h). Furthermore, the leaching kinetics was controlled by the boundary layer, coincident with a shrinking core model. According to the Arrhenius plot, the activation energy for Zn ranges from 49.13 to 52.21 kJ mol−1, and that for Mn ranges from 46.97 to 66.77 kJ mol−1.
      Citation: Recycling
      PubDate: 2022-11-18
      DOI: 10.3390/recycling7060086
      Issue No: Vol. 7, No. 6 (2022)
  • Recycling, Vol. 7, Pages 87: Healthcare Waste Management in Nigeria: A

    • Authors: Obiora B. Ezeudu, Tochukwu S. Ezeudu, Uzochukwu C. Ugochukwu, Imokhai Theophilus Tenebe, Agbaji P. Ajogu, Uchenna V. Nwadi, Charles C. Ajaero
      First page: 87
      Abstract: Healthcare waste management has become an important aspect of medical care delivery globally. This is simply because of its hazardous and infectious components that have greater potential for adverse health and environmental impacts. As such, certain guidelines and procedures have been developed by international aid agencies and conventions to guide national governments and local administrations in formulating policies and practices for effective healthcare waste management. In this work, we reviewed the existing literature to appraise the status of healthcare waste management practices in Nigeria. This included generation, segregation, collection, storage, transportation, treatment, and disposal. The current work further reviewed the other essential elements of healthcare waste management, such as policy landscapes, training, awareness, and waste characterization, and discusses challenges and opportunities for effective healthcare waste management in Nigeria. Among the challenges are poor funding, inadequate training, ineffective legislature, and absence of data. However, there are available low-cost technologies that are suitable for the treatment of waste in a developing country like Nigeria. This technology variant offers an opportunity for a circular economy as it can simultaneously achieve energy production, waste management, and other socioeconomic advantages.
      Citation: Recycling
      PubDate: 2022-11-21
      DOI: 10.3390/recycling7060087
      Issue No: Vol. 7, No. 6 (2022)
  • Recycling, Vol. 7, Pages 88: Evaluation of Construction and Demolition
           Waste Management in Kuwait

    • Authors: Mohammed Baqer Hasan Almusawi, Ahmad Tarmizi Bin Abd Karim, Saleem Ethaib
      First page: 88
      Abstract: This research aimed to evaluate Kuwait’s current construction and demolition waste (C&D waste) situation by focusing on C&D waste generation and management issues. This work also investigated the causes and factors affecting C&D waste to understand the actual waste management activities and proposed strategies to minimize the waste generated at the local level. This study estimated C&D waste generation rates based on data collected from five construction projects and two demolition projects in Kuwait. In addition, a questionnaire survey was conducted to evaluate the causes of C&D waste generation. The results showed that the average C&D waste quantities generated by construction activities were 49.5 kg/m2 for public/commercial building projects and 35 kg/m2 for residential projects. At the same time, public/commercial construction, residential construction, and demolition works generated 1.480 ton/m2, 0.0495 ton/m2, and 0.035 ton/m2, respectively. The average composition of C&D waste from the construction sector was 35.4% concrete waste, followed by 19.2% tiles/blocks, and 14.2% metals, with the remainder being other materials. Meanwhile, the demolition waste was composed of 70% concrete and cement waste and 20% metals. The results showed that 54% of the projects disposed of their C&D waste directly in the landfills. The leading causes of C&D waste generation were reworks due to changes in specifications, poor material quality, improper material handling, and improper site management. Strategic C&D waste management practices are necessary for sustainable natural resource management and conservation of the environment.
      Citation: Recycling
      PubDate: 2022-11-24
      DOI: 10.3390/recycling7060088
      Issue No: Vol. 7, No. 6 (2022)
  • Recycling, Vol. 7, Pages 89: Sustainable Bio-Composites Obtained from
           Recycling Post-Industrial PLA and Fillers Derived from Coffee Production

    • Authors: Andrea Saccani, Maurizio Fiorini, Gianfranco Burzotta
      First page: 89
      Abstract: Bio-composites have been formulated by exploiting post-industrial PLA derived from thin film production and silver skin, a by-product of the coffee’s roasting process. The mix design for the compounds exploits the effects of regrading and toughening agents. The mechanical properties of the materials have been investigated as well as the thermal and physical ones. The recycled material mixed with the regrading additive shows good mechanical properties. The filler addition increases the elastic modulus of PLA up to a 20% but decreases the mechanical properties (about 20% on tensile strength), leading to a brittle behavior (minus 35% of impact strength). The use of a toughening agent restores the plastic deformation ability of the matrix.
      Citation: Recycling
      PubDate: 2022-11-30
      DOI: 10.3390/recycling7060089
      Issue No: Vol. 7, No. 6 (2022)
  • Recycling, Vol. 7, Pages 90: Washing Post-Consumer Flexible Polyethylene
           Packaging Waste

    • Authors: Ezgi Ceren Boz Noyan, Abhijit Venkatesh, Antal Boldizar
      First page: 90
      Abstract: The mechanical and thermal properties of injection-molded recycled polyethylene were studied, specifically with respect to the influence of large-scale washing and melt-compounding of polyethylene from post-consumer packaging waste. Three types of materials were studied: those taken after sorting, after sorting and washing, and after sorting, washing, and melt-compounding, including melt-filtration, all from a large-scale material flow. The materials were further processed on a laboratory scale and compared. The results showed that large-scale washing significantly reduced thermo-oxidative stability, as well as molar mass and melt viscosity. The degradation during large-scale washing made the material susceptible to further degradation in the subsequent extrusion compounding, as shown by the differences in compounding at 240 and 200 °C using a high-shear screw configuration. The compounding parameters, screw configuration, and compounding temperature did not influence the stiffness and strength of the unwashed and large-scale-washed materials, but the elongation-at-break varied, specifically, with the increased temperature. Washing had an influence on the mechanical properties as well, and the unwashed material provided molded samples with stiffness measurements of approximately 550 MPa, whereas the large-scale-washed material provided stiffness of approximately 400 MPa. The strength measurements were approximately 15 MPa for samples made of both unwashed and large-scale-washed material, and the elongation-at-break measurements were between 50 and 150%. The large-scale-washed and compounded materials had very different mechanical properties, with stiffness measurements of approximately 320 MPa, strength of approximately 20 MPA, and elongation-at-break of approximately 350%. The significantly different mechanical properties of the large-scale-washed and compounded materials were likely due to the melt-filtration included in the compounding through the removal of metal and rubber particles, and they may also have been due to the compatibilizing and stabilizing additive used in the compounding.
      Citation: Recycling
      PubDate: 2022-12-14
      DOI: 10.3390/recycling7060090
      Issue No: Vol. 7, No. 6 (2022)
  • Recycling, Vol. 7, Pages 62: Assessment of Public Opposition to
           Construction and Demolition Waste Facilities: A Case Study in Australia

    • Authors: Soheila Ghafoor, Salman Shooshtarian, Tayyab Maqsood, Peter SP Wong
      First page: 62
      Abstract: The purpose of this paper is to investigate the nature of public opposition (PO) to the siting of construction and demolition (C&D) waste management facilities in Australia. A qualitative case study of PO to the development proposal for the Gunnedah waste facility, in the state of New South Wales (NSW), was conducted. The waste facility is promised to process up to 250 kilotons of waste materials, much of which is C&D waste intended for use in road constructions after processing. Using a content analysis approach, the study analysed 86 public submissions that were lodged within the allocated development application exhibition period to systematically analyse the arguments used by the submitters about the establishment of the facility. The case study revealed five broad perceived risk classes to the siting of the Gunnedah waste facility, namely location, environmental, human health, financial and process risks. It was also shown that while not-in-my-back-yard (NIMBY) attitudes may have played a part in the PO to the sitting at the facility, the PO was heavily affected by the poor public participation process. The study outlines key strategies for an effective public participation process that may assist with the management of PO to the siting of C&D waste management facilities in Australia. The study contributes to the theory and practice of effective C&D waste management, enhancing the social acceptance of such facilities toward a more circular economy in the built environment.
      Citation: Recycling
      PubDate: 2022-08-26
      DOI: 10.3390/recycling7050062
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 63: Quantification of Construction Waste in Early
           Design Stages Using Bim-Based Tool

    • Authors: Rocío Quiñones, Carmen Llatas, Maria Victoria Montes, Isidro Cortés
      First page: 63
      Abstract: Construction and demolition waste represents a growing environmental, social, and economic problem, and has become a priority for European and worldwide policies. The early quantification of construction waste is essential for the minimisation of its production and the improvement of waste management. This requires the development of design-based tools that enable a better understanding of the expected waste produced during the construction phase. Building Information Modelling (BIM) methodologies have gained recognition in the Architecture, Engineering, Construction, and Operations (AECO) sector, largely due to their capacity for data simulation, storage, and management during the building design phase. This study presents a software application, called WE-BIM Add-in, to quantify construction waste (CW) while designing the BIM model in Revit. A validated CW quantification model which enables waste types and quantities per building element to be predicted in detail according to the European List of Waste (LoW) is integrated into the Revit workflow. Design alternatives could be effortlessly simulated in real time to assist practitioners in decision-making during the early design stages. Two alternative structural systems of a Spanish residential building were compared: a reinforced concrete structure, Option 1 (O1), and a steel structure, Option 2 (O2). The results were obtained automatically: O2, in addition to reducing 56% of O1′s waste, would have increased the waste recycling rate by 49%; and displayed in Revit, thereby remaining consistent with those of other studies that compare prefabricated systems with in situ systems. This work provides a basis for future research into the automated estimation of construction waste in BIM which could become a useful tool in waste-prevention policies.
      Citation: Recycling
      PubDate: 2022-08-31
      DOI: 10.3390/recycling7050063
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 64: The Current State, Challenges, and
           Opportunities of Recycling Plastics in Western Australia

    • Authors: Ana María Cáceres Ruiz, Atiq Zaman
      First page: 64
      Abstract: In 2018–2019, 85% of discarded plastics were landfilled in Australia. In Western Australia (WA), only 5.6% of plastics were recovered for reprocessing. With several Asian Countries imposing import restrictions, which were the prime destination for recyclables from Australia, the whole scenario for the waste industry has changed. Australia has now adopted export bans for recyclables, including plastics. WA is at a fork in the road; WA needs to rethink its relationship with plastic materials. This study explores how to create local markets for recycled plastics underpinning circular principles. The study examines barriers and drivers to enable markets for recycled plastics in WA through questionnaires, surveys, and interviews with relevant stakeholders. Poor source separation, low and inconsistent plastic waste feedstock, and virgin plastic competition are some of the challenges, while new investments in recycling infrastructure, WA’s take-back scheme for beverage containers and circularity frameworks are drivers. This study concludes that a modulated fee-based product stewardship model focused on product design, along with strategies such as green procurement and landfill management modifications would promote a circular plastic waste economy in WA. This can create markets for secondary recycled plastics, minimize the over-reliance on fossil fuels and prevent plastics from leaking into ecosystems.
      Citation: Recycling
      PubDate: 2022-09-06
      DOI: 10.3390/recycling7050064
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 65: Plastics Crash Course: A Website for Teaching
           Plastics Recycling and Microplastics Prevention through Infographics

    • Authors: Madison R. Reed, Wan-Ting Chen
      First page: 65
      Abstract: Microplastic particles have been found virtually everywhere, including within our food and drinking water. While the implications of microplastics on human health are not fully known, early effects have been seen on marine life and the environment. Studies have shown that microplastics can cause changes in the reproductive habits of marine life by blocking digestive tracts, causing abrasions to the mouth and esophagi of small animals upon ingestion, and altering feeding behavior. While much of the blame for our plastics pollution problem should be shifted to irresponsible manufacturing, we as consumers must make choices to benefit the environment by reducing our use and learning how to effectively recycle plastic waste. The Plastics Crash Course combines visual learning with plastics recycling knowledge to educate the public about why we need plastics and why we should recycle them. Microplastics formation and general guides for plastic recycling were also included in the Plastics Crash Course. Out of 120 participants, 95% responded that they had learned new information. From the pre-survey, participants responded, saying they thought all plastic was the same and that it just varied in density to provide different properties, so they would recycle everything. After reading the infographics on the Plastics Crash Course website, most participants said they learned what plastics can be recycled and what their resin identifying codes mean, how microplastics form, and that there is more than one type of plastic.
      Citation: Recycling
      PubDate: 2022-09-07
      DOI: 10.3390/recycling7050065
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 66: New Terahertz Wave Sorting Technology to
           Improve Plastic Containers and Packaging Waste Recycling in Japan

    • Authors: Jeongsoo Yu, Xiaoyue Liu, Gaku Manago, Tadao Tanabe, Shiori Osanai, Kazuaki Okubo
      First page: 66
      Abstract: Plastic product consumption and disposal are widespread. Given that these products are derived from crude oil, it is critical to reduce their consumption and effectively recycle plastic waste as recycled resources to achieve a low-carbon society. Japan enacted the “Containers and Packaging Recycling Law” in 2000, encouraging the recycling of plastic packaging and containers. However, material recycling of plastic waste has stalled due to recycling costs and technical challenges. This paper examines and evaluates the transition process and operational status of Japan’s recycling policy for plastic containers and packaging, as well as clarifies the limits of resources recycling. The limits and issues of current identification technology are discussed by analyzing the characteristics of plastic marks and detecting the material compositions of waste samples. The paper also discusses a new sorting technology that uses terahertz waves to improve plastic recycling. This analysis revealed that plastic containers are typically made of two or more plastic materials, which makes resources recycling more difficult. Terahertz waves are safer than other high-accuracy sorting technologies currently in use. Thus, material recycling can be expanded by accurately analyzing the composition of plastic waste and introducing sorting devices appropriate for achieving the circular economy with sustainable resource recycling.
      Citation: Recycling
      PubDate: 2022-09-09
      DOI: 10.3390/recycling7050066
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 67: Biohydrometallurgical Recovery of Metals from
           Waste Electronic Equipment: Current Status and Proposed Process

    • Authors: Kundani Magoda, Lukhanyo Mekuto
      First page: 67
      Abstract: Electronic waste (e-waste) is an emerging health and environmental burden due to the toxic substances present within e-wastes. To address this burden, e-wastes contain various base, rare earth and noble metals, which can be recovered from these substances, thus serving as secondary sources of metals. Pyrometallurgical and hydrometallurgical processes have been developed to extract metals from e-waste. However, these techniques are energy-intensive and produce secondary wastes, which will add to the operating costs of the process. However, the biohydrometallurgical approach has been deemed as an eco-friendly, cost-effective, and environmentally friendly process that does not produce large quantities of secondary waste. However, research has focused chiefly on one-stage bioprocesses to recover the metals of interest and majorly on base metals recovery. Hence, this review proposes a two-stage bio-hydrometallurgical process where the first stage will consist of acidophilic iron and sulphur oxidising organisms to extract base metals, followed by the second stage which will consist of cyanide-producing organisms for the solubilisation of rare earth and precious metals. The solid waste residue that is produced from the system can be used in the synthesis of silica nanomaterials, which can be utilised for various applications.
      Citation: Recycling
      PubDate: 2022-09-12
      DOI: 10.3390/recycling7050067
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 68: Comparative Study of Manufacturing NdFeB
           Magnet Wastes Recycling: Oxidative Roasting-Selective Leaching and Whole
           Leaching Routes

    • Authors: Tapany Patcharawit, Woranittha Kritsarikan, Tanongsak Yingnakorn, Sakhob Khumkoa
      First page: 68
      Abstract: This research investigated recycling of manufacturing NdFeB magnet wastes in as-sintered and powder forms which contained high carbon via pyro-hydro metallurgy process. Effects of oxidative roasting on selective leaching of the magnet wastes were the main focus in comparison to recycling via whole leaching without oxidative roasting. The process started from oxidative roasting at 600 °C, sulfuric leaching, drying, roasting at 750 °C for powder and 800 °C for sintered wastes, water leaching, oxalic acid precipitation and calcination at 1000 °C to obtain neodymium oxides. Oxidative roasting was found to reduce carbon and resulted in neodymium and iron oxide formation with a minimum amount of neodymium iron oxide. This provided effective selective leaching of neodymium. For whole leaching, a significant loss of neodymium into leached residue was observed. Oxidative roasting-selective leaching provided significant recovery in the amount of 75.46% while whole leaching resulted in only 31.62 wt.% in the case of sintered waste. The final composition via oxidative roasting-selective leaching consisted of 68.11 wt.% neodymium, 19.83 wt.% praseodymium and 0.31 wt.% iron, while whole leaching resulted in a higher amount of iron at 1.20 wt.%. Similar results were obtained for powder magnet waste.
      Citation: Recycling
      PubDate: 2022-09-19
      DOI: 10.3390/recycling7050068
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 69: Manufacturing of a PET Filament from Recycled
           Material for Material Extrusion (MEX)

    • Authors: Maximilian Bustos Seibert, Gerardo Andres Mazzei Capote, Maximilian Gruber, Wolfram Volk, Tim A. Osswald
      First page: 69
      Abstract: Due to its low cost and easy use, the use of material extrusion (MEX) as an additive manufacturing (AM) technology has increased rapidly in recent years. However, this process mainly involves the processing of new plastics. Combining the MEX process with polyethylene terephthalate (PET), which offers a high potential for mechanical and chemical recyclability, opens up a broad spectrum of reutilization possibilities. Turning used PET bottles into printable filament for MEX is not only a recycling option, but also an attractive upcycling scenario that can lead to the production of complex, functional parts. This work analyzes the process of extruding recycled PET bottle flakes into a filament, taking different extrusion screws and extrusion parameters into account. The filament is subsequently processed with MEX into tensile tests. An accompanying thermal, rheological and mechanical characterization of the recycled resin is performed to offer a comparison to the virgin material and a commercially available glycol modified polyethylene terephthalate (PETG) filament. The results show the importance of adequate drying parameters prior to the extrusion and the sensitivity of the material to moisture, leading to degradation. The recycled material is more prone to degradation and presents lower viscosities. Mechanical tests display a higher tensile strength of the recycled and virgin resin in comparison to the PETG. The extrusion of the used PET into a filament and the subsequent printing with the MEX process offers a viable recycling process for the discarded material.
      Citation: Recycling
      PubDate: 2022-09-20
      DOI: 10.3390/recycling7050069
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 70: Plastic Waste Management through the
           Development of a Low Cost and Light Weight Deep Learning Based Reverse
           Vending Machine

    • Authors: Huma Zia, Muhammad Uzair Jawaid, Hafiza Sundus Fatima, Imtiaz Ul Hassan, Azmat Hussain, Sheryar Shahzad, Muhammad Khurram
      First page: 70
      Abstract: The management of the abundant amount of used plastic bottle waste is a major concern nowadays, because it is a major contributor to landfills and overburdens waste processing facilities. Once disposed of, plastic can take centuries to break down, hence, recycling not only manages the waste efficiently, but it reduces the environmental impact and creates economic opportunities, as well. An incentive-based Reverse Vending machine (RVM) is an effective way to involve the general public in the management of plastic waste. The existing solutions are either very expensive, from a computation and cost perspective, or they lack the robustness and durability necessary for deployment. In this research, we have developed an incentive-based low-cost RVM for the collection, identification, classification, and sorting of used plastic bottles with the addition of a reward-based user application. The developed RVM includes a low-cost computing device running a lightweight image processing algorithm, sensors, camera, and a self-designed mechanical arm. To support the low computing device in the RVM, a lightweight MobileNet model has been trained using transfer learning. A dataset of 10,983 pet bottle images was collected using a camera installed inside the machine for the classification model. The results of the study show that MobileNet achieved 99.2% testing accuracy, which is better than the existing bottle-classification approaches. Moreover, the weight of the developed model was only 12 Mb, which is fourteen and six times less than inceptionV3 and Res-Net (Residual Neural Networks), respectively. Furthermore, the developed RVM costs a fraction of the price, compared to the existing solutions. Two versions of the machine have been deployed at a University for more than 6 months, collecting over 650 kg of plastic waste.
      Citation: Recycling
      PubDate: 2022-09-22
      DOI: 10.3390/recycling7050070
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 71: Design of a Fixed-Bed Column with Vegetal
           Biomass and Its Recycling for Cr (VI) Treatment

    • Authors: Uriel Fernando Carreño Sayago, Yineth Piñeros Castro, Laura Rosa Conde Rivera
      First page: 71
      Abstract: The aim of this work is to design a fixed-bed column with vegetal biomass of Eichhornia crassipes and the process of recycling it for treatment via the adsorption of water loaded with chromium (VI). In the first stage, the relationship between the fixed-bed density and the microparticle density is calculated, giving a model for the design of the fixed bed. Using this model, two systems for the treatment of Cr (VI)-contaminated water were designed and built. The vegetable biomass at three particle diameters of 0.212 mm, 0.30 mm and 0.45 mm was evaluated in the removal of Cr (VI) from water using the designed fixed-bed systems, giving the best removal of Cr (VI) with the lowest size particles and allowing the validation of the proposed model with the Thomas model. The incorporation of iron into the biomass allowed for the treatment of near 2.0 L of polluted solution, removing around 90% of Cr (VI), while it was only possible to treat nearly 1.5 L when using raw biomass, removing around 80% of Cr (VI). The recycling of the biomass was achieved via the elution of Cr (VI) with EDTA, permitting the reuse of the material for more than five treatment cycles.
      Citation: Recycling
      PubDate: 2022-09-24
      DOI: 10.3390/recycling7050071
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 72: Applied Tests to Select the Most Suitable
           Fungal Strain for the Recovery of Critical Raw Materials from Electronic
           Waste Powder

    • Authors: Ester Rosa, Simone Di Piazza, Grazia Cecchi, Michela Mazzoccoli, Micol Zerbini, Anna Maria Cardinale, Mirca Zotti
      First page: 72
      Abstract: Electrical and electronic wastes (WEEEs) are a potential source of raw materials. The main challenge for scientists is to set up a reliable and eco-friendly process to recycle raw materials and precious elements from WEEEs. Today, we know that fungi could play an active role in green technologies aimed at recycling valuable elements. The bioaccumulation mechanism and bioleaching activity of filamentous fungal species have already been exploited fruitfully in extraction processes. However, not all fungal strains possess the same characteristics, and it is crucial to choose the right strains to use. In this work, we show a method to assess the precious elements’ recovery efficiency from WEEE using fungal strains. A CAS agar screening test for siderophore detection was carried out with three strains. The following plate accumulation test performed on a medium added with 120 ppm of electronic waste powder highlighted the differences in accumulation capability, growth rate, and biomass production. Among the elements in tested waste, yttrium, copper, and palladium show the highest bioconcentration factor. The results confirm the biotechnological potential of fungi to recover valuable elements at the bench scale, highlighting the importance of effective screening tests to assess the most efficient strain for each kind of waste.
      Citation: Recycling
      PubDate: 2022-10-05
      DOI: 10.3390/recycling7050072
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 73: Potential Analysis of the Plastics Value
           Chain for Enhanced Recycling Rates: A Case Study in Iceland

    • Authors: Moritz Mager, Ines Traxler, Joerg Fischer, David C. Finger
      First page: 73
      Abstract: In light of the circular economy gaining momentum, plastics recycling is regarded as a key solution to keep materials in the loop. Continuous efforts are needed to achieve the packaging waste recycling targets set by the European Union. Hence, this work evaluates the potential of the Icelandic plastics value chain for enhanced recycling rates. In addition to identifying the main challenges and opportunities, a feasibility study was conducted on the expansion of the deposit-return system to Skyr cups, allowing for closed-loop solutions. Based on the status quo, proposals for the improvement of the current waste and recycling system are made. Insights were acquired by semi-structured interviews with nine key stakeholders in Iceland, representing vital groups that influence the plastics value chain. The obtained answers followed the same trend, pointing out that a circular economy within the boundaries of Iceland is currently not feasible. This is mainly due to the strong dependence on international partners in all parts of the value chain except waste collection. However, major improvements are required to enhance the current waste collection rate of 28%. No conclusive evidence was found to justify the suitability of Skyr cups for the deposit-return system, as the disadvantages outweigh theoretically higher collection and recycling rates. Moreover, the extended producer responsibility scheme implemented with the Icelandic Recycling Fund is a valuable tool to enforce a design for recycling of products, enabling higher recycling rates. Despite one recycler operating in Iceland, Icelandic stakeholders consider sorting and treatment of mixed plastic waste as economically more efficient by collaborating with experts throughout Europe. Therefore, they expect that the current practice of exporting the majority of the domestic waste will prevail. On the contrary, the authors propose a comprehensive waste treatment and recycling scheme within Iceland, which requires a sorting step prior to three possible pathways, being (1) mechanical recycling, (2) alternative fuel, and (3) waste-to-energy. The aim of the proposed scheme is a reduction in greenhouse gas impact of plastics entering the waste stage by an efficient and flexible design of the relevant technologies within Iceland.
      Citation: Recycling
      PubDate: 2022-10-09
      DOI: 10.3390/recycling7050073
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 74: The Utilization of Waste Toner as a Modifier
           in Trinidad Asphalts

    • Authors: Shane Rambarran, Rean Maharaj, Sharona Mohammed, Nadine Sangster
      First page: 74
      Abstract: As more persons are adjusting to home working in light of the COVID-19 pandemic, there has been a significant increase in the use of technology. Trinidad and Tobago, like many other Small Island Developing States, began exploring strategies in the areas of recycling and reuse techniques to mitigate negative environmental impacts from the disposal of waste toners. The reuse of waste toners as a performance enhancer in bituminous materials has successfully been achieved in foreign jurisdictions; however, the lack of research on the utilization of the indigenous Trinidad Lake Asphalt (TLA) and Trinidad Petroleum Bitumen (TPB) has stymied the application of this strategy locally. The influence of four waste toners (A, B, C, and D) on the rheological properties of an unmodified TLA/TPB paving binder was measured using the dynamic shear rheology (DSR) testing technique. The addition of waste toners noted improvements in the rheological parameters of stiffness, elasticity, and viscosity, exhibiting superior temperature susceptibility. Of great interest was the observation at 90 °C, where the modified paving binders containing 5% Toner C and 20% Toner D were elastically superior to the world-renowned TLA. This study demonstrated the potential of utilizing waste toner as a bitumen modifier, providing an innovative, sustainable disposal option.
      Citation: Recycling
      PubDate: 2022-10-13
      DOI: 10.3390/recycling7050074
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 75: Efficient Recovery of Solid Waste Units as
           Substitutes for Raw Materials in Clay Bricks

    • Authors: Ioannis Makrygiannis, Athena Tsetsekou
      First page: 75
      Abstract: The advent of new materials and technologies in building materials has changed the way of building. New lighter materials with easier application methods and improved mechanical behaviors, have become necessary for the market. Moreover, the new environmental policy (2022) aims to transform the waste management into sustainable materials management to ensure the long-term protection and improvement of the environment. For the brick and tile industry, raw materials and the additives that compose the product mixture seem to be a key factor in this direction. Furthermore, every product type (solid or perforated brick) requires different additives to achieve the properties that are postulated by the international standards. For the study, the wide range of additives that were used have been assorted into three (3) categories: the inert materials, the lightweight materials, and the industrial remains. Totally, eight (8) different materials were used as additives into ceramic mass, in different proportions each time. Almost all additives used for this research were pore-forming agents. These burn out almost completely before reaching the full-fire temperature, and do not change the fired body. As a result of additives burnt out, the necessary pore volume is formed in the fired brick body, which, if combined with an appropriate percentage of voids, result in raw density readings. The pore structure is significant as long as the ultimate strength of lightweight bricks is acceptable. In this study, additives between 3 and 25% by weight were added to the clay mixture. The extrusion of specimens in solid form was carried out using the Laboratory’s vacuum press. Firstly, the extrusion of specimens from the original raw material was implemented. Secondly, it was made on the material mixed with the additives mentioned above. A series of experimental activities were followed to determine the variations of the mechanical and physical properties as well as their production procedures (extrusion, drying, and firing). According to five (5) key properties measured in the current study and compared with the mixture without additives, it was found that the variation in thermal conductivity improvement is between -11% and 19%. The bending strength of the fired products showed a decrease from 16% to 55% except for the addition of bauxite residue, which increased the strength by 8%. Bigot drying sensitivity decreased from 11% to 27%. The density in two cases increased from 2% to 7% while in the majority the mixtures with the additives showed a decrease in density from 1% to 14%. Finally, the addition of the necessary water for shaping during extrusion showed a variation from a 10% decreased to a 14% increased water.
      Citation: Recycling
      PubDate: 2022-10-17
      DOI: 10.3390/recycling7050075
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 76: Recycling of Cement–Wood Board
           Production Waste into a Low-Strength Cementitious Binder

    • Authors: Argalis, Sinka, Bajare
      First page: 76
      Abstract: Cement is a widely used building material, with more than 4.4 billion metric tons produced in 2021. Unfortunately, the excessive use of cement raises several environmental issues, one of which is the massive amounts of CO2e produced as a by-product. Using recycled materials in the concrete mix is widely employed to solve this problem. A method for minimizing the use of natural cement by substituting it with secondary cementitious material that consists of wood–cement board manufacturing waste has been studied in this paper. The cement in the waste stream was reactivated by a mechanical treatment method—the use of a planetary mill, allowing it to regain its cementitious properties and be used as a binder. Physical and mineralogical analysis of the binder material was performed using X-ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA) and Brunauer–Emmett–Teller analysis; granulometry and compressive strength tests were also carried out. The results show that the grinding process did not significantly change the mineralogical composition and the specific surface area; it did, however, affect the compressive strength of the samples prepared by using the reactivated binding material; also, the addition of plasticizer to the mix increased compressive strength by 2.5 times. Samples were cured in high-humidity conditions. The optimal water-to-binder (W/B) ratio was found to be 0.7 because of the wood particles that absorb water in their structure. Compressive strength increased as the grinding time increased.
      Citation: Recycling
      PubDate: 2022-10-17
      DOI: 10.3390/recycling7050076
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 77: Methods of Commercialization and Usage of
           Sosnovsky hogweed Processing

    • Authors: Daria Y. Mironova, Vijayakumar Varadarajan, Ivan V. Timakhovich, Nadezhda V. Barakova, Asemgul A. Tokbaeva, Olga N. Rumiantseva, Elizaveta E. Pomazkova, Igor V. Baranov, Liudmila I. Tishchenko
      First page: 77
      Abstract: Sosnovsky’s hogweed is an invasive species that suppresses natural meadow biocenoses, but at the same time it can be a source of various biological substances (raw materials). Hogweed can be processed to produce cellulose. The obvious advantage of cellulose from Sosnovsky’s hogweed is the unsuitability of the raw material for other uses, i.e., while valuable resources that are now being used to produce cellulose can be saved, the stems of Sosnovsky’s hogweed are waste products obtained because of getting rid of the plant. Despite this, there is an actual problem of including hogweed in the production chain. To solve this problem, business models can be built that are aimed at using the biproducts of processing hogweed. It is important that business models not only reflect the process of producing added value but also can solve the main problem of processing weed plants: the finiteness of the specified resource. Specifically, entrepreneurs starting such a business should not get into a situation where they destroy their only resource. This article is focused on a comparison of business models according to the following criteria: feasibility, profitability, and environmental impact. Business models that involve constructing a processing plant, using mobile laboratories, and industrial symbiosis models are presented. The overall result of this work is a business model that meets the specified criteria. Similar business models can be used for other plants with the possibility of obtaining valuable raw materials. Research shows how Sosnovsky hogweed can be processed into bioethanol or cellulose.
      Citation: Recycling
      PubDate: 2022-10-17
      DOI: 10.3390/recycling7050077
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 78: Green Composites Based on PLA and Cotton
           Fabric Waste: Preparation and Characterization

    • Authors: Narongchai O-Charoen, Piyaporn Kampeerapappun, Khanittha Charoenlarp, Nawadon Petchwattana, Ektinai Jansri
      First page: 78
      Abstract: Textile waste, from both consumption and production, has dramatically increased due to a lack of diversification in its use. Increasing the number of textile alternatives can help to solve these problems. Producing a green composite product is an interesting alternative method. The objectives of this work were to study the preparation and characterization of green composites created from PLA and cotton fabric waste (CFW) and to consider the effect of the CFW content on the composites. The procedure of the research began with CFW pellets preparation; this was subsequently compounded with PLA pellets using a melt-mixing technique with a twin-screw extruder at ratios of 90:10, 80:20, and 70:30 wt% between the PLA and cotton fabric waste, respectively. Then, the testing specimens were produced by compression molding. The experiments demonstrated that an increase in the CFW caused an increase in the viscosity, stiffness, Tg, Tm, and water absorption of the composites. The decomposition temperature of the composites showed a range of 302.41 to 361.22 °C; this decreased when the CFW increased. An increase in the CFW also produced greater and clearer phase separation and roughness on the fracture surface area.
      Citation: Recycling
      PubDate: 2022-10-19
      DOI: 10.3390/recycling7050078
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 79: Recycling Perspectives of Circular Business
           Models: A Review

    • Authors: Md Tasbirul Islam, Usha Iyer-Raniga, Sean Trewick
      First page: 79
      Abstract: The circular business model (CBM) is one of the main building blocks of circular economy (CE), and recycling is one of the main strategies for achieving it. CBM literature is currently evolving, and recycling-oriented discussion has been found in a scattered manner. This review article aims to identify critical components of the recycling-focused business model in CE and evaluate potential business and research opportunities in the area. Data collection was undertaken from the Web of Science (WoS) core collection and ScienceDirect database. Results of the study showed that efficiency of municipal solid waste management, reporting mechanism of recyclers cost of recycled materials, the establishment of a plastic hub, implementation of extended producer responsibility, strategic partnership, incentives, and product design were highlighted as critical requirements for efficient recycling operated business models, especially for waste solar PV panels, e-waste, textile waste, and vehicles and battery sector. It also identified the benefits of using recycled materials in reducing carbon footprint, energy consumption, and achieving low environmental impact. Three-dimensional printing, sensor-based RFID tags, digital twins, additive manufacturing, Industry 4.0, and the Internet of Things (IoT) were found as state-of-the-art technological innovations applied to recycling-oriented circular business models. This article provides critical practical solutions for new business model development and indicates vital future research directions along with a conceptual framework development, which would be helpful for policymakers, business entities, and research academics.
      Citation: Recycling
      PubDate: 2022-10-20
      DOI: 10.3390/recycling7050079
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 80: Assessment of the Energetical and Biological
           Characteristics of Municipal Solid Waste from One of the Largest Landfills
           in Kazakhstan

    • Authors: Arlan Z. Abilmagzhanov, Nikolay S. Ivanov, Oleg S. Kholkin, Iskander E. Adelbaev
      First page: 80
      Abstract: Solid waste management is one of the main problems in large cities. The determination of the quantitative and qualitative composition of municipal solid waste is necessary for proper planning in the processing of such waste. This article presents the results of studies of the morphological composition, physico-chemical parameters and energetical potential of municipal solid waste (MSW) from the landfill of the city of Shymkent. Waste samples were taken from 10 different points of the landfill. The volume–mass parameters of the samples and their average density were determined. The combined waste samples mainly consisted of food waste, paper and cardboard, polymers and plastic, glass, metal, textiles, wood, leather, bones and rubber. Most of the waste, more than 30%, contains plastic products. The moisture of the combustible fraction of the samples is low and varies from 0.3% to 2.3%. The average ash content of the combustible fraction of the samples was determined and its average value is 18.4%. The yield of the volatile substances was determined and the average value per dry state is 78.7%. To determine the energetical potential of municipal solid waste, the gross calorific value was determined and the net calorific value was calculated, the average value of which is 24.15 MJ/kg. This shows the possibility of using solid waste as an energy source.
      Citation: Recycling
      PubDate: 2022-10-20
      DOI: 10.3390/recycling7050080
      Issue No: Vol. 7, No. 5 (2022)
  • Recycling, Vol. 7, Pages 42: Understanding Business Requirements for
           Increasing the Uptake of Recycled Plastic: A Value Chain Perspective

    • Authors: Malou van der Vegt, Evert-Jan Velzing, Martijn Rietbergen, Rhiannon Hunt
      First page: 42
      Abstract: Circularity and recycling are gaining increased attention, yet the amount of recycled plastic applied in new products remains low. To accelerate its uptake by businesses, it will be useful to empirically investigate the barriers, enablers, needs and, ultimately, requirements to increase uptake of recycled plastic feedstock for the production of new plastic products. During the six focus group sessions we conducted, a value chain approach was used to map the factors that actors face regarding the implementation of recycled materials. The identified factors were structured based on three levels: determining whether a certain factor acted as a barrier or enabler, identifying the steps in the value chain that the factor directly affected and the category it could be subdivided into. The results were then further processed by translating the (rather abstract) needs of businesses into (specific) requirements from industry. This study presented eight business requirements that require actions from other actors in the value chain: design for recycling, optimised waste processing, standardisation, material knowledge, showing possibilities, information and education, cooperation, and regulation and government intervention. The main scientific contributions were the value chain perspective and the applied relevance of the findings. Future studies may delve deeper into the individual factors identified.
      Citation: Recycling
      PubDate: 2022-06-29
      DOI: 10.3390/recycling7040042
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 43: Environmental and Economic Comparison of
           Natural and Recycled Aggregates Using LCA

    • Authors: Adriana Dias, Salem Nezami, José Silvestre, Rawaz Kurda, Rui Silva, Isabel Martins, Jorge de Brito
      First page: 43
      Abstract: Recycled aggregates (RAs) have been playing an important role in replacing natural aggregates (NAs) in concrete production, thereby contributing to a reduction in the extraction of natural resources and the promotion of a circular economy. However, it is important to assess the global impacts of this replacement, in both environmental and economic terms. In this study, an overview of the impacts of the production of natural and recycled aggregates is presented, using the life cycle assessment (LCA) methodology. Through this methodology, products with the same function are compared and information about the best solutions is given, considering their environmental and economic impacts. Studies with data collected from specific producers were compared, as well as environmental product declarations (EPDs) and generic databases, regarding the production of natural and recycled, coarse and fine, and rolled and crushed aggregates. This study intends therefore to provide the environmental and economic impact comparison at the global level through LCA from different data sources. According to this literature review, the best and worst environmental results are assigned to lower and higher transport distances, respectively. Regarding EPDs, the lowest environmental impacts are related to recycled coarse aggregates and the highest to natural coarse crushed aggregates. In terms of generic databases, the results are similar, with the lowest impacts associated with natural fine rolled aggregates and the highest to natural coarse crushed aggregates. In what concerns the economic impacts, in general, recycled aggregates are associated with the lowest costs. However, these results are highly dependent on transport distances and costs.
      Citation: Recycling
      PubDate: 2022-06-30
      DOI: 10.3390/recycling7040043
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 44: Improving the Separation of PS and ABS
           Plastics Using Modified Induced Air Flotation with a Mixing Device

    • Authors: Pattarasiri Fagkaew, Nattawin Chawaloesphonsiya, Saret Bun, Pisut Painmanakul
      First page: 44
      Abstract: A dramatic increase in plastic waste has resulted in a strong need to increase plastic recycling accordingly. A selective flotation has been highlighted due to its outstanding efficiency for the separation of mixed plastics with analogous physicochemical characteristics. In this study, the effects of design and operational factors on the bubble’s hydrodynamic and mixing parameters in induced air flotation (IAF) with a mixing device were investigated through a design of experiment method (DOE) analysis for improving the plastic separation efficiency (i.e., PS and ABS). As a result of DOE analysis, the increase in the induced air tube diameter together with the rotational speed could generate a smaller bubble size. This led to the enhancement of the ratio of interfacial area to velocity gradient (a/G), which was interestingly found to be a significant factor affecting plastic recovery apart from the chemical agents. It demonstrates that operating IAF with a mixing device at a greater a/G ratio improved the plastic separation performance. These findings suggest that operating an IAF process with a mixing device at suitable a/G conditions could be a promising technique for separating plastic wastes, which have similar physicochemical characteristics as PS and ABS.
      Citation: Recycling
      PubDate: 2022-07-04
      DOI: 10.3390/recycling7040044
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 45: Recycling of Lead Pastes from Spent

    • Authors: Yongliang Xiong
      First page: 45
      Abstract: Lead–acid batteries are important to modern society because of their wide usage and low cost. The primary source for production of new lead–acid batteries is from recycling spent lead–acid batteries. In spent lead–acid batteries, lead is primarily present as lead pastes. In lead pastes, the dominant component is lead sulfate (PbSO4, mineral name anglesite) and lead oxide sulfate (PbO•PbSO4, mineral name lanarkite), which accounts for more than 60% of lead pastes. In the recycling process for lead–acid batteries, the desulphurization of lead sulfate is the key part to the overall process. In this work, the thermodynamic constraints for desulphurization via the hydrometallurgical route for recycling lead pastes are presented. The thermodynamic constraints are established according to the thermodynamic model that is applicable and important to recycling of lead pastes via hydrometallurgical routes in high ionic strength solutions that are expected to be in industrial processes. The thermodynamic database is based on the Pitzer equations for calculations of activity coefficients of aqueous species. The desulphurization of lead sulfates represented by PbSO4 can be achieved through the following routes. (1) conversion to lead oxalate in oxalate-bearing solutions; (2) conversion to lead monoxide in alkaline solutions; and (3) conversion to lead carbonate in carbonate solutions. Among the above three routes, the conversion to lead oxalate is environmentally friendly and has a strong thermodynamic driving force. Oxalate-bearing solutions such as oxalic acid and potassium oxalate solutions will provide high activities of oxalate that are many orders of magnitude higher than those required for conversion of anglesite or lanarkite to lead oxalate, in accordance with the thermodynamic model established for the oxalate system. An additional advantage of the oxalate conversion route is that no additional reductant is needed to reduce lead dioxide to lead oxide or lead sulfate, as there is a strong thermodynamic force to convert lead dioxide directly to lead oxalate. As lanarkite is an important sulfate-bearing phase in lead pastes, this study evaluates the solubility constant for lanarkite regarding the following reaction, based on the solubility data, PbO•PbSO4 + 2H+ ⇌ 2Pb2+ + SO42− + H2O(l).
      Citation: Recycling
      PubDate: 2022-07-12
      DOI: 10.3390/recycling7040045
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 46: Leading the World: A Review of Household
           Recycling in Wales

    • Authors: Ian D. Williams, Joseph Phillips
      First page: 46
      Abstract: Wales is one of the world leaders in household waste recycling with a steady recent recycling rate of ~65%. The Welsh Assembly Government (WAG) set a statutory target of achieving a 70% recycling rate by 2024/25. We reviewed historical trends in waste management in Wales from 2006 to 2020, with a focus on recycling. Authoritative, official data were obtained from WasteDataFlow, an Internet system for municipal waste data reporting by UK local authorities to government. Data are collected quarterly allowing the generation of time series plots, trendlines and like-for-like comparisons between groupings of various characteristics, such as number of separate kerbside collections, income, political preference, and impact of policy changes. Results showed that the approach taken by the WAG to politically prioritise and encourage participation in household recycling has achieved impressive results that contrast starkly with the recycling performance of other UK countries. In Wales, household waste disposed annually per person via landfill decreased from ~410 kg to <50 kg and household waste recycled increased from to ~150 kg to ~310 kg, with a recent increase in incineration with energy recovery to ~135 kg as infrastructure has come online. Recycling rates show a seasonal variation due to increases in garden waste sent for composting in the summer. There are variations in local authority performance across Wales, mainly caused by variations in the number of separate collections. Co-mingled collections tend to lead to higher contamination of recyclates that are then not able to be sold for recycling. Deprivation, as indicated by differences in income, also influences total waste arisings and recycling rates. A plateau of ~65% recycling rate was reached in 2020, with incineration reaching a rate of >25%. The recycling rate plateaus at exactly the same time as incineration comes on stream. Evidence demonstrates that improvements to recycling rates can become more difficult when incineration becomes available. Whilst further reductions and improvements to recycling in Wales will be more challenging, the WAG’s track record of focused proactive political and policy support shows what can be achieved when there is suitable political will. The WAG has demonstrated that it tends to deliver on its waste-related plans, and it clearly has the best chance of any of the UK’s four countries of achieving its aims.
      Citation: Recycling
      PubDate: 2022-07-18
      DOI: 10.3390/recycling7040046
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 47: Skid Resistance Performance of Asphalt
           Mixtures Containing Recycled Pavement Materials under Simulated Weather

    • Authors: Maria Pomoni, Christina Plati
      First page: 47
      Abstract: One of the challenges of using recycled materials in road structures is to maintain safe and durable pavements. A multitude of research has been conducted over the years on various recycled materials, with a focus on the structural performance of pavements. Another crucial, but almost overlooked, aspect is the pavement’s ability to provide adequate skid resistance for road users under different climatic conditions. With this in mind, the present study aimed to investigate the skid resistance of asphalt mixtures containing two different types of recycled materials under laboratory-simulated weather conditions. Conventional hot-mix asphalt (HMA) and mixtures containing either reclaimed asphalt pavement (RAP) for aggregate replacement or crumb rubber (CR) as a bitumen additive were prepared and tested at different temperatures and different surface conditions (i.e., dry/wet) following a wetting protocol. Skid resistance was measured using a British Pendulum Tester (BPT). The results showed that the recycled mixtures performed similarly to conventional ones in terms of the skid resistance when the temperature was varied and under variable simulated surface conditions too. In some cases, they performed even better than conventional mixtures. Overall, a promising potential is demonstrated towards the use of the investigated recycled materials in asphalt surface courses.
      Citation: Recycling
      PubDate: 2022-07-19
      DOI: 10.3390/recycling7040047
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 48: An Approach for Automated Disassembly of
           Lithium-Ion Battery Packs and High-Quality Recycling Using Computer
           Vision, Labeling, and Material Characterization

    • Authors: Merle Zorn, Christina Ionescu, Domenic Klohs, Konstantin Zähl, Niklas Kisseler, Alexandra Daldrup, Sigrid Hams, Yun Zheng, Christian Offermanns, Sabine Flamme, Christoph Henke, Achim Kampker, Bernd Friedrich
      First page: 48
      Abstract: A large number of battery pack returns from electric vehicles (EV) is expected for the next years, which requires economically efficient disassembly capacities. This cannot be met through purely manual processing and, therefore, needs to be automated. The variance of different battery pack designs in terms of (non-) solvable fitting technology and superstructures complicate this. In order to realize an automated disassembly, a computer vision pipeline is proposed. The approach of instance segmentation and point cloud registration is applied and validated within a demonstrator grasping busbars from the battery pack. To improve the sorting of the battery pack components to achieve high-quality recycling after the disassembly, a labeling system containing the relevant data (e.g., cathode chemistry) about the battery pack is proposed. In addition, the use of sensor-based sorting technologies for peripheral components of the battery pack is evaluated. For this purpose, components such as battery pack and module housings of multiple manufacturers were investigated for their variation in material composition. At the current stage, these components are usually produced as composites, so that, for a high-quality recycling, a pre-treatment may be necessary.
      Citation: Recycling
      PubDate: 2022-07-20
      DOI: 10.3390/recycling7040048
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 49: Stakeholder Assessment on Closing Nutrient
           Cycles through Co-Recycling of Biodegradable Household Kitchen Waste and
           Black Water between Rural and Urban Areas in South India

    • Authors: Veronika Fendel, Martin Kranert, Claudia Maurer, Gabriela Garcés-Sánchez, Jingjing Huang, Girija Ramakrishna
      First page: 49
      Abstract: Agricultural land degradation, urban migration, increasing food demand and waste, and inadequate sanitation systems all affect farmers, local society, and the environment in South India. Joint recycling of biodegradable secondary household resources to close nutrient cycles between urban and rural regions can address all these challenges and thus several SDGs at the same time. Efforts are being made to this end, but many attempts fail. The central research question is, therefore: how can co-recycling concepts be evaluated in this context' For this purpose, composting plants, biogas fermenters, and a high-tech concept to produce plant charcoal, design fertilizer, and biopolymers are considered. The aim of this study is to evaluate the recycling concepts from the stakeholders’ perspective to avoid gaps between theory and practice. Six expert and one focus group interviews on two successful on-site case studies and 15 online expert interviews with thematic actors were qualitatively evaluated and presented in a social network analysis to identify preferences and indicators for the further evaluation of co-recycling concepts. The results show that the focus is on mature technologies such as compost and biogas. High-tech solutions are currently still in rudimentary demand but will play a more important role in the future. To evaluate such concepts, seven key indicators and their measured values were identified and clustered into the categories ecological, social, technical, economic, and connective. The results show that this methodology of close interaction with stakeholders and the evaluation of successful regional case studies minimize the gap between practice and theory, contribute to several goals of the SDGs, and thus enable such concepts to be implemented sustainably.
      Citation: Recycling
      PubDate: 2022-07-20
      DOI: 10.3390/recycling7040049
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 50: Use of a Design of Experiments (DOE) for
           Studying the Substitution of Natural River Sand (NRS) by Gold Mine
           Tailings (GMT) in Concrete Manufacturing

    • Authors: Clarisse Njovu Balegamire, Pierre Jean-Marie Dable, Kouwelton Kone, Bossissi Nkuba
      First page: 50
      Abstract: The extraction of precious minerals leaves behind an important amount of tailings. When stored in nature, these tailings contribute to environmental degradation. To reduce this degradation, tailings are incorporated in construction as substitute to natural materials. The objective of this study was to use a design of experiments (DOE) to reveal how the substitution of natural river sand (NRS) by gold mine tailings (GMT) in concrete manufacturing can be optimally achieved. This DOE considered three constituents: the amounts of NRS/GMT, that of gravel and of cement. The experimental domain was defined within the concrete standards dosage of 350 kg/m3 and 400 kg/m3 as the lower and upper levels, respectively. The smallest compressive strength on standard cubic specimens on the 28th day varied between 11 N/mm2 and 37 N/mm2 following to the experimental domain. The values of the compressive strength of the experiments carried out allowed to acquire the model of the strength with the coefficients of each factor: Strength=23.25−5.86*A+4.56*B−1.96*C−0.56*A*B+1.41*A*C+1.08*B*C+0.71*A*B*C (with A: GMT+NRS; B: cement; C: gravel). The values of the cumulative weight of the coefficients of each factor were 36.7% (A), 64.5% (B) and 76.6% (C). The study also found that a larger dosage of gravel (40 kg) improves the concrete compressive strength when GMT substitutes NRS between 70% and 100% and when 15 kg of cement is used. For a sustainable and better reuse of GMT as construction materials, an economic and environmental study (the leaching of metals) of the concrete based on GMT would be ideal to consider a large scale production.
      Citation: Recycling
      PubDate: 2022-07-26
      DOI: 10.3390/recycling7040050
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 51: A State-of-the-Art Review on the
           Incorporation of Recycled Concrete Aggregates in Geopolymer Concrete

    • Authors: Bahareh Nikmehr, Riyadh Al-Ameri
      First page: 51
      Abstract: Geopolymer concrete (GC) has the potential to incorporate recycled concrete aggregates (RCA) obtained from construction and demolition waste. This research aims to review the current state-of-the-art knowledge of the RCA in GC and identify the existing knowledge gaps for future research direction. This paper highlights the essential factors that impact the GC’s mechanical and durability properties. Moreover, the influence of various percentages of coarse and fine RCA and the pattern of their replacement will be assessed. The effect of aluminosilicate material, alkaline activators, and curing regime also will be evaluated. Besides, the durability-related characteristics of this concrete will be analysed. The impact of exposure to a higher temperature, freeze–thaw cycles, marine environment, and acid and alkali attack will be comprehensively reviewed. A literature review revealed that increasing alumina silicate content, such as slag and metakaolin, and increasing the Na2SiO3/NaOH ratio and alkali-activator-to-binder ratio improve the hardened GC. However, increasing slag and metakaolin content and the Na2SiO3/NaOH ratio has an adverse impact on its workability. Therefore, finding the optimum mix design for using RCA in GC is vital. Moreover, there is a scope for developing a self-compacting GC cured at ambient temperature using RCA.
      Citation: Recycling
      PubDate: 2022-07-27
      DOI: 10.3390/recycling7040051
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 52: Factors Influencing Household Waste
           Separation Behavior: Cases of Russia and Finland

    • Authors: Anna Zaikova, Ivan Deviatkin, Jouni Havukainen, Mika Horttanainen, Thomas Fruergaard Astrup, Minna Saunila, Ari Happonen
      First page: 52
      Abstract: This paper investigates the factors influencing the behavior of individuals in source-separation of municipal solid waste in an immature system for collection of recyclable waste (Saint Petersburg, Russia) and a more mature waste system (selected urban areas, Finland). Online questionnaires were applied to collect data from citizens of Saint Petersburg and the Finnish urban population. The data were examined within an extended theory of planned behavior using structural equation modeling for the identification of factors affecting waste source-separation behavior. The findings indicate that the factors differed significantly in the two waste systems. In Russia, the inconvenience of waste collection limited waste source-separation behavior, while intentions of individuals and information availability had an almost equal positive effect. In Finland, waste source-separation behavior was mostly affected by people’s intentions. Based on the findings, recommendations for the development of recycling practices were made for practitioners in Russia and possibly other early-stage systems for the collection of recyclable waste. Limitations of the study pinpointed the possibilities for future research.
      Citation: Recycling
      PubDate: 2022-07-28
      DOI: 10.3390/recycling7040052
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 53: Unpicking the Gender Gap: Examining
           Socio-Demographic Factors and Repair Resources in Clothing Repair Practice

    • Authors: Rachel H. McQueen, Lisa S. McNeill, Qinglan Huang, Balkrushna Potdar
      First page: 53
      Abstract: Increased fashion consumption spurred by fast fashion has led to excessive textile waste, giving rise to a global crisis as textile waste pollutes land and waterways, while landfill and incineration contribute to global greenhouse gas emissions. Extending a product’s life for as long as possible is a core principle of the circular economy (CE) to ensure that the maximum value of the original product is realized over its lifetime. As such, repair is an essential component of a CE because it supports the preferred waste hierarchy elements of reduce and reuse, with recycling being the last resort in a CE necessary to close resource loops. Consumers are an essential enabler of a CE; therefore, it is critical to understand consumers’ characteristics in the context of behaviors such as repair. The purpose of this study was to examine the role of gender on engagement in clothing repair practices; women have often only been the focus of clothing repair studies. An online survey was conducted to collect responses from Canadian and U.S. consumers (n = 512). Findings showed that self-repair was the most common form of clothing repair, with women being more highly engaged in self-repair practices, increasing with age. Paid repair is the type of repair that has the lowest level of engagement, and there are only negligible differences between the genders. Men utilize unpaid forms of repair more than women. However, among the youngest age group (18–24), both genders are equally likely to have clothing repaired for free. Gender gaps exist, but opportunities for increased utilization in repair can be created to encourage full participation within a CE. In particular, the findings point to the importance of increasing repair activities amongst men and younger consumers.
      Citation: Recycling
      PubDate: 2022-08-05
      DOI: 10.3390/recycling7040053
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 54: Agro-Industrial Wastewater Treatment with

    • Authors: Nuno Jorge, Ana R. Teixeira, Marco S. Lucas, José A. Peres
      First page: 54
      Abstract: The removal of dissolved organic carbon (DOC) and total polyphenols (TPh) from agro-industrial wastewater was evaluated via the application of coagulation–flocculation–decantation (CFD) and Fenton-based processes. For the CFD process, an organic coagulant based on Acacia dealbata Link. leaf powder (LP) was applied. The results showed that the application of the LP at pH 3.0, with an LP:DOC ratio of 0.5:1 (w/w), achieved a high removal of turbidity, total suspended solids (TSS), and volatile suspended solids (VSS) of 84.7, 79.1, and 76.6%, respectively. The CFD sludge was recycled as fertilizer in plant culture (germination index ≥ 80%). Afterwards, the direct application of Fenton-based processes to raw WW was assessed. The Fenton-based processes (UV/Fenton, UV/Fenton-like, and heterogeneous UV/Fenton) showed high energy efficiency and a cost of 1.29, 1.31 and 1.82 €/g/L DOC removal, respectively. The combination of both processes showed the near complete removal of TPh and DOC after 240 min of reaction time, with high energy efficiency. In accordance with the results obtained, the combination of CFD with Fenton-based processes achieves the legal limits for the disposal of water into the environment, thus allowing the water to be recycled for irrigation.
      Citation: Recycling
      PubDate: 2022-08-08
      DOI: 10.3390/recycling7040054
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 55: Experimental and Artificial Neural
           Network-Based Study on the Sorptivity Characteristics of Geopolymer
           Concrete with Recycled Cementitious Materials and Basalt Fibres

    • Authors: Sherin Khadeeja Rahman, Riyadh Al-Ameri
      First page: 55
      Abstract: The environmental concerns regarding the production of the most widely consumed cement construction material have led to the need for developing sustainable alternatives. Using recycled industry waste products such as fly ash and slag via geopolymerisation has led to the development of geopolymer cement—an efficient replacement for ordinary Portland cement (OPC). Adopting geopolymer cement and concrete as a construction material reduces greenhouse gas and promotes the recycling of waste products. This study explores the suitability of a unique geopolymer concrete mix made of recycled cementitious materials including industry waste products such as fly ash, micro fly ash and slag for use in aggressive environments. Sorptivity tests are conducted to assess the durability of concrete and indicate the cementitious material’s ability to transmit water through the capillary forces. This study thus reports on the sorptivity characteristics of a newly developed self-compacting geopolymer concrete and two other fibre geopolymer concrete mixes containing 1% (by weight) of 12 mm- or 30 mm-long basalt fibres. The addition of basalt fibres indicated less water absorption and moisture ingress than the mix without fibres. The study used 18 specimens from three geopolymer concrete mixes, and the results showed that adding fibres improved the durability performance in terms of resistance to moisture ingress. Finally, an artificial neural network model is developed to predict the absorption rates of geopolymer concrete specimens using MATLAB. The prediction models reported excellent agreement between experimental and simulated datasets.
      Citation: Recycling
      PubDate: 2022-08-09
      DOI: 10.3390/recycling7040055
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 56: Special Issue “Feature Papers in
           Recycling 2021”

    • Authors: Francesco Paolo La Mantia, Beatrice Castellani
      First page: 56
      Abstract: Recycling is the collection and conversion process of waste materials into second raw materials [...]
      Citation: Recycling
      PubDate: 2022-08-11
      DOI: 10.3390/recycling7040056
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 57: Reclaiming the Value of Cotton Waste
           Textiles: A New Improved Method to Recycle Cotton Waste Textiles via Acid

    • Authors: Edvin Ruuth, Miguel Sanchis-Sebastiá, Per Tomas Larsson, Anita Teleman, Amparo Jiménez-Quero, Sara Delestig, Viktor Sahlberg, Patricia Salén, Marjorie Sanchez Ortiz, Simran Vadher, Ola Wallberg
      First page: 57
      Abstract: The fashion industry is becoming one of the largest emitters worldwide due to its high consumption of raw materials, its effluents, and the fact that every garment will eventually contribute to the vast amount of waste being incinerated or accumulating in landfills. Although fiber-to-fiber recycling processes are being developed, the mechanical properties of the textile fibers are typically degraded with each such recycle. Thus, tertiary recycling alternatives where textiles are depolymerized to convert them into valuable products are needed to provide end-of-life alternatives and to achieve circularity in the fashion industry. We have developed a method whereby cotton waste textiles are depolymerized to form a glucose solution, using sulfuric acid as the sole catalyst, with a high yield (>70%). The glucose solution produced in this process has a high concentration (>100 g/L), which reduces the purification cost and makes the process industrially relevant. This method can be applied regardless of the quality of the fibers and could therefore process other cellulosic fibers such as viscose. The glucose produced could subsequently be fermented into butanediol or caprolactam, precursors for the production of synthetic textile fibers, thus retaining the value of the waste textiles within the textile value chain.
      Citation: Recycling
      PubDate: 2022-08-12
      DOI: 10.3390/recycling7040057
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 58: Analyzing Polyethylene Terephthalate Bottle
           Waste Technology Using an Analytic Hierarchy Process for Developing
           Countries: A Case Study from Indonesia

    • Authors: Akhmad Amirudin, Chihiro Inoue, Guido Grause
      First page: 58
      Abstract: PET bottle waste is easy to recycle because it is easy to separate, abundant, and competitively priced. Technologies for the treatment of PET bottle waste have been evaluated to date by using life cycle assessment (LCA), but this does not take into account all of the aspects that policymakers consider necessary when selecting an acceptable technology. Aspects such as society, economics, policies, and technical applicability need to be considered along with the environment and resource consumption to complement the LCA results for PET bottle waste. These aspects were selected as criteria for the analytical hierarchy process (AHP), and stakeholders were invited to make a comparison evaluation of the criteria and sub-criteria. Academics were involved to compare the technology options. The results show that society is the highest priority because it is the main actor that ensures the application of the technology, and that job creation is the most important indicator for the selection of the technology in society criteria. After comparing open landfills, sanitary landfills, incineration with energy recovery, pelletizing, glycolysis, and hydrolysis for the utilization of PET bottle waste, this study suggests pelletizing as the acceptable technology for Indonesia because pelletizing is dominant in all the criteria and sub-criteria which support sustainability in waste management. This is the first time that a single plastic fraction that is easy to collect and recycle has been studied with the AHP. The results show that this type of plastic could also be reused in developing countries through mechanical recycling.
      Citation: Recycling
      PubDate: 2022-08-15
      DOI: 10.3390/recycling7040058
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 59: Strength and Microstructure of Coffee
           Silverskin Blended Mortar

    • Authors: Moruf Olalekan Yusuf, Zeyad M. A. Mohammed, Adeshina A. Adewumi, Mutasem Taisir Shaban, Meshrif Omar Meshrif AlBaqawi, Hatim Dafalla Mohamed
      First page: 59
      Abstract: This study pertains to incorporation of coffee silverskin (CSS) in partial replacement for ordinary Portland cement (OPC) in mortar, by investigating its fresh properties (setting and workability), compressive strength (3, 7, 14 and 28-day), absorption and microstructural characteristics. The objectives were to reduce environmental solid wastes and achieve cost efficiency in the use of construction materials. The CSS was expressed as a ratio of total binder (CSS/(OPC + CSS)) and varied from 0 to 5%. The findings revealed that CSS could reduce workability, setting time and early strength. It could also enhance the absorption of the CSS-blended mortar (CBM). The cause of reduction in workability was due to its contribution to the viscosity of the mixture due to the emulsification of the fat component (acetate) and aromatic compounds, as observed in the Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction techniques. The presence of these compounds also caused microstructural disintegration that resulted in the lower strength. In addition, the presence of other organic compound in CSS but absent in OPC enhanced microstructural disintegration and porosity in CBM. The 28-day strength of 25 MPa could be achieved in CSS-blended mortar if the CSS/(CSS + OPC) ratios were kept below 3%. The maximum compressive strength of 38.5 MPa was obtained with the optimum CSS content of 1 wt%. The relative density (water) of CSS was 0.345; therefore, it could also be used to produce lightweight concrete. This study promotes the valorization of raw CSS waste as construction material which could be used for subgrade in the construction of road pavement.
      Citation: Recycling
      PubDate: 2022-08-15
      DOI: 10.3390/recycling7040059
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 60: Environmental Effects of Bio-Waste Recycling
           on Industrial Circular Economy and Eco-Sustainability

    • Authors: Sasmoko, Khalid Zaman, Maida Malik, Usama Awan, Wiwik Handayani, Mohd Khata Jabor, Muhammad Asif
      First page: 60
      Abstract: Few prior studies have examined the social and environmental consequences of waste generation and recycling, resulting in a policy gap in the sustainability agenda. The research filled a knowledge vacuum in the literature by investigating the environmental repercussions of different waste generation and recycling processes in the Chinese economy. The study analyzed waste production and recycling statistics over the last 46 years, from 1975 to 2020, and their impact on the nation’s emissions per capita. This study used four primary approaches to determine the links between the examined variables, beginning with the unit root test, which identifies the stationary process of the variables’ underlying processes. Second, the autoregressive distributed lag (ARDL) model was used to produce the variables’ short- and long-run estimates. Third, estimations of Granger causality examined the causal relationships between the variables. Finally, innovation accounting matrices (IAM)were utilized to predict the relationships between variables during the following decade. The unit root estimates imply the mix order of variable integration; hence, it is appropriate to employ ARDL modeling for parameter estimations. The ARDL estimations demonstrate that combustible renewables and waste decrease a nation’s carbon emissions by boosting industrial waste recycling. Despite recycling systems, carbon emissions have escalated to uncontrolled levels owing to the massive production of municipal solid garbage. Sustainable waste management and recycling are vital to reducing carbon emissions. Granger’s estimations of causation imply that combustible renewables and waste and carbon emissions cause industrial and municipal solid waste recycling. Additionally, population growth is responsible for greenhouse gas emissions, biowaste recycling, and industrial waste recycling. Furthermore, this shows the two-way connections between combustible renewables and waste and carbon emissions, implying the need to develop green waste recycling strategies in a nation. The IAM method identified future relationships between variables, which aids policymakers in implementing sustainable waste management practices for a nation. This study concludes that the environmental consequences of waste generation and recycling impede the nation’s circular economy agenda, which can be sustained by knowledge spillovers, chemical reduction in manufacturing, and allocating a certain amount of US dollars to ecological resource conservation.
      Citation: Recycling
      PubDate: 2022-08-15
      DOI: 10.3390/recycling7040060
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 61: Engineering Characterisation of Wearing
           Course Materials Modified with Waste Plastic

    • Authors: Nuha Mashaan
      First page: 61
      Abstract: This review paper shows several sections of bitumen, asphalt mixtures, polymers, and waste plastic in pavement engineering. The paper reviews and evaluates the influence of using waste polymer in improving the rheological and engineering properties of the modified binder and mixtures. Evaluation of properties and design of stone mastic asphalt mixtures are reviewed. Reports and studies had investigated the advantages and importance of using polymer in bitumen modification; however, they yet show a gap in research in terms of the role of waste polymer in improving the durability, aging, and fatigue life in the long term of service.
      Citation: Recycling
      PubDate: 2022-08-18
      DOI: 10.3390/recycling7040061
      Issue No: Vol. 7, No. 4 (2022)
  • Recycling, Vol. 7, Pages 27: Treatment of Scrap Tire for Rubber and Carbon
           Black Recovery

    • Authors: Alaa Sultan Abdulrahman, Fawzi Habeeb Jabrail
      First page: 27
      Abstract: In this study, a chemical dissolution treatment was used to recover rubber and carbon black (CB) from truck tire scrap, with gas oil acting as the solvent and 4-Hydroxy-TEMPO acting as the catalyst for the chemical reactions. Montmorillonite clay was used to separate the rubber solution from the CB and the other non-dissolved tire additives. The recovered rubber and CB were characterized together with the original scrap tire sample by XRD, SEM, BET and thermal analysis, as well as FTIR and 1H NMR spectral analyses. Characterization of the chemical structure of the recovered rubber showed that the main functional groups of styrene−butadiene rubber blend with natural rubber. The thermal behavior and crystalline structure of the recovered rubber, as well as its morphological images, showed that the properties of the rubber sample were acceptable and similar to natural rubber. The recovered CB characterizations showed that the sample after pyrolysis was a highly crystalline nanocomposite structure with a high specific surface area and scattered pores.
      Citation: Recycling
      PubDate: 2022-04-20
      DOI: 10.3390/recycling7030027
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 28: The Physical Characterization and Terminal
           Velocities of Aluminium, Iron and Plastic Bottle Caps in a Water

    • Authors: Alexander A. Nikolaev
      First page: 28
      Abstract: Aluminium, iron and plastic are materials which are extensively used at both industry and individual levels. However, significant amounts of aluminium, iron and plastic end up in the environment. Specifically, bottle caps made of these materials are often thrown away, with or without bottles, and appear among the common plastic debris entering the world’s oceans and beaches. More than 20 million bottle caps and lids have been identified during beach-cleaning campaigns over the last 30 years. To recover bottle caps from the shores, conventional technologies can be used. In this paper, the physical properties of used metal and plastic bottle caps were examined and related to the settling and rising velocities of the caps, as well as their drag coefficients and hydrodynamic modes in water environments, with respect to gravity separation. The sample contained aluminium, iron, high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP) bottle caps. The findings revealed that the density differences between the bottle caps resulted in the terminal settling velocities of aluminium and iron particles, which were significantly higher than the rising velocities of the plastic caps. The results allowed us to design a flowsheet for bottle cap recovery from beach coasts in order to reduce environmental impact and produce add-on plastic and metal products.
      Citation: Recycling
      PubDate: 2022-04-22
      DOI: 10.3390/recycling7030028
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 29: Analysis of Plastic-Derived Fuel Oil Produced
           from High- and Low-Density Polyethylene

    • Authors: Chandni Joshi Jangid, Kevin M. Miller, Jeffrey R. Seay
      First page: 29
      Abstract: The exponential growth of waste plastic accumulation has had an irreversible and lasting impact on the world. An imminent threat to marine and terrestrial ecosystems of massive proportions, plastic waste accumulation is a global problem that will not only have to be tackled by current generations but for many generations to follow. The scale of current recycling technologies and efforts to reduce consumption by for-profit and non-profit institutions, governments, and consumers will need to be rapidly increased to combat the negative impacts plastic waste has had on the planet since its conception. This is especially the case in areas with limited infrastructure to properly collect, manage, and dispose of plastic waste. Solutions to plastic waste accumulation crisis that are appropriate for the developing world are urgently needed. Conversion of plastic waste to liquid fuel by slow pyrolysis is a technology that is particularly suitable for developing countries due to its ability to convert polyolefin waste plastic into a useful product, thus preventing its eventual accumulation in the ecosystem. However, in developing countries, conversion techniques that do not rely on sophisticated technologies are needed. Since processing time and operating temperature are the simplest variables to control, an analytical study has been conducted to assess how the molecular composition of plastic derived fuel oil (PDFO) is impacted by these parameters. The results of gas chromatography-mass spectrometry (GC-MS) and thermogravimetric analysis (TGA) studies of PDFO from high- and low-density polyethylene plastic waste produced using appropriate technology techniques are presented alongside a comparison with traditional diesel fuel and kerosene. This approach is novel in that it differs from previously conducted research, which has studied the use of catalysts, additives, or single operating temperatures to assess the composition of PDFO. Therefore, this research contribution presents a simplistic and inexpensive approach for tuning PDFO composition in appropriate technology settings.
      Citation: Recycling
      PubDate: 2022-05-07
      DOI: 10.3390/recycling7030029
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 30: Processing of Gypsum Construction and
           Demolition Waste and Properties of Secondary Gypsum Binder

    • Authors: Girts Bumanis, Jelizaveta Zorica, Aleksandrs Korjakins, Diana Bajare
      First page: 30
      Abstract: The waste amount coming from construction and demolition (CDW) has significant volume and potential to provide the backbone of a secondary material bank. Up to now, little attention is paid to waste gypsum recycling from CDW while a shift in global attitude toward waste management brings motivation to use CDW gypsum as secondary raw material. The present research investigates the properties of gypsum binder obtained from secondary raw materials originating from CDW. Three types of drywall boards and cast monolithic gypsum from interior walls, treated in the laboratory, and a gypsum binder was obtained. Comparison has been studied and the most effective solutions regarding CDW treatment are represented. Separation, crushing, and milling were done. DTA/TG, XRD, SEM, and particle size distribution were characterized by CDW gypsum. The heat treatment temperature was selected at 130 °C for 4 or 24 h and 180 °C for 4 h. Consistency, set time, and mechanical properties were characterized. Results indicate that a gypsum binder with a strength up to 3.7 MPa can be obtained. Low strength is associated with fineness of CDW gypsum and a high water/gypsum ratio (from 0.6 to 1.396). Gypsum content in CDW (38 to 92 wt.%) should be considered as an important factor during gypsum CDW recycling.
      Citation: Recycling
      PubDate: 2022-05-17
      DOI: 10.3390/recycling7030030
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 31: Zero Liquid Discharge System for the Tannery
           Industry—An Overview of Sustainable Approaches

    • Authors: Rajamanickam Ricky, Subramanian Shanthakumar, Ganapathy Pattukandan Ganapathy, Fulvia Chiampo
      First page: 31
      Abstract: The tannery industry is characterized by the consumption of a large quantity of water, around 30–40 m3 for processing 1000 kg of hide or skin. This amount becomes wastewater, containing about 300 kg of different chemicals, mainly refractory organic compounds, with high chemical oxygen demand (COD), total dissolved salts (TDS), chromium, and evolution of toxic gases, such as ammonia and sulfides, etc. The remaining tanning chemicals are released as effluent having high resistance against biological degradation, becoming a serious environmental issue. Usually, end-of-pipe treatment is not sufficient to meet the concerns of environmental issues. In terms of cleaner production options, the redesigning of the existing effluent treatment procedures with alternate or additional treatment techniques, which “supports resource recovery with no added chemicals”, is expected to give a sustainable solution for the management of toxic effluent. The Zero Liquid Discharge (ZLD) system serves to ensure zero water emission, as well as treatment facilities by recycling, recovery, and reuse of the treated wastewater using advanced cleanup technology. The international scenario shows the implementation of ZLD thanks to pressure from regulatory agencies. The ZLD system consists of a pre-treatment system with conventional physicochemical treatment, tertiary treatment, softening of the treated effluent, reverse osmosis (RO) treatment for desalination, and thermal evaporation of the saline reject from RO to separate the salts. By adopting this system, water consumption is reduced. Moreover, ZLD also becomes effective in disaster mitigation in areas where the tannery industry is a strong economic actor. With this review, we aim to give an outlook of the current framework.
      Citation: Recycling
      PubDate: 2022-05-24
      DOI: 10.3390/recycling7030031
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 32: Identifying Future Skill Requirements of the
           Job Profiles for a Sustainable European Manufacturing Industry 4.0

    • Authors: Tugce Akyazi, Patricia del Val, Aitor Goti, Aitor Oyarbide
      First page: 32
      Abstract: The exponential growth of digitalisation and the continuous increase in sustainability needs are currently reshaping the European manufacturing industry through its entire value chain. Industrial sectors have undergone significant changes globally in recent years, and they will continue to face this deep transformation. The manufacturing sectors, more specifically, companies, need to develop a relevant strategy that can support their organisation to handle the upcoming future technological developments and sustainability requirements properly. In order to implement the strategy effectively and achieve an adequate digital and green transformation, their main focus should be the development of a multi-skilled workforce. This competent workforce can only be built by foreseeing the changes in the needed skills for the manufacturing industry and then updating the skills of the current workforce accordingly. As an answer to this need, we developed an automated skill database for the manufacturing industry, particularly transversal occupations of this sector related to the industrial symbiosis (IS) and energy efficiency (EE). Differently from the conventional ones, the generated database incorporated not only the current but also the future skill needs for each profile. During the development of the future skills for each occupation in the database, we identified the foreseen skill needs for the manufacturing industry through detailed desk research. Therefore, this paper presents a valuable perspective on the subject. Our work aimed to fill the gap for a database specifically developed for the manufacturing industry, which provides the end-users with data about the new skills requirements resulting from industrial changes and sustainability needs. We believe that companies, education and training institutions and policymakers can make use of the generated database as a complementary tool for developing their training programmes or strategy roadmaps to cover the emerging changes in each individual industrial sector.
      Citation: Recycling
      PubDate: 2022-05-26
      DOI: 10.3390/recycling7030032
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 33: Lithium-Ion Battery Recycling in the Circular
           Economy: A Review

    • Authors: Md Tasbirul Islam, Usha Iyer-Raniga
      First page: 33
      Abstract: Lithium-ion batteries have become a crucial part of the energy supply chain for transportation (in electric vehicles) and renewable energy storage systems. Recycling is considered one of the most effective ways for recovering the materials for spent LIB streams and circulating the material in the critical supply chain. However, few review articles have been published in the research domain of recycling and the circular economy, with most mainly focusing on either recycling methods or the challenges and opportunities in the circular economy for spent LIBs. This paper reviewed 93 articles (66 original research articles and 27 review articles) identified in the Web of Science core collection database. The study showed that publications in the area are increasing exponentially, with many focusing on recycling and recovery-related issues; policy and regulatory affairs received less attention than recycling. Most of the studies were experiments followed by evaluation and planning (as per the categorization made). Pre-treatment processes were widely discussed, which is a critical part of hydrometallurgy and direct physical recycling (DPR). DPR is a promising recycling technique that requires further attention. Some of the issues that require further consideration include a techno-economic assessment of the recycling process, safe reverse logistics, a global EV assessment revealing material recovery potential, and a lifecycle assessment of experiments processes (both in the hydrometallurgical and pyrometallurgical processes). Furthermore, the application of the circular business model and associated stakeholders’ engagement, clear and definitive policy guidelines, extended producer responsibility implications, and material tracking, and identification deserve further focus. This study presents several future research directions that would be useful for academics and policymakers taking necessary steps such as product design, integrated recycling techniques, intra-industry stakeholder cooperation, business model development, techno-economic analysis, and others towards achieving a circular economy in the LIB value chain.
      Citation: Recycling
      PubDate: 2022-05-28
      DOI: 10.3390/recycling7030033
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 34: A Study of the Feasibility of Using Grey
           Sedge Residue to Facilitate Zero Waste Production

    • Authors: Kamonwan Chucheep, Nathaporn Suwanpayak, Naree Phanchindawan
      First page: 34
      Abstract: There is approximately 30% of grey sedge (Lepironia articulata) residue remaining from weaving production that could add value to support zero waste management. Therefore, the aim of this research was to study the feasibility of using a residue of grey sedge or Krajood strips from weaving production to form a value-added product. To obtain preliminary data, Krajood strip residue was examined for its biological and physical properties. In addition, the biological and physical properties of Krajood strip residue in combination with loam soil (KSRL) were examined and compared with the properties of loam soil (LS) itself. The results showed that the total microbe and moisture content of the Krajood strip residue was significantly higher than that of the products made from Krajood strips (KS). The stress value of Krajood strips was higher than the stress values of other samples except for that of a bag made of paper. Identification of bacteria and mold by MALDI Biotyper and DNA sequencing compared with BLAST revealed the presence of the types of soil microbes that benefit plants. KSRL was enriched with larger amounts of the primary elements important for plant growth: nitrogen, phosphorus, and potassium, and the three second tier elements. The pH of KS, LS, and KSRL were 6.40 ± 0.14, 5.87 ± 0.04, and 5.26 ± 0.02, respectively. These results could support the use of this beneficial residue for bioresource sustainability.
      Citation: Recycling
      PubDate: 2022-05-31
      DOI: 10.3390/recycling7030034
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 35: Encouraging Sustainable Use of RAP Materials
           for Pavement Construction in Oman: A Review

    • Authors: Husam Al Dughaishi, Jawad Al Lawati, Munder Bilema, Ali Mohammed Babalghaith, Nuha S. Mashaan, Nur Izzi Md. Yusoff, Abdalrhman Milad
      First page: 35
      Abstract: The Sultanate of Oman has experienced rapid development over the last thirty years and has constructed environmentally friendly and sustainable infrastructure while it continues to find economical alternative resources to achieve the goals of the Oman 2040 vision. The primary concerns are preserving natural resources and reducing the impact of carbon dioxide (CO₂) emissions on the environment. This review aims to encourage the sustainable use of reclaimed asphalt pavement (RAP) materials in pavement construction and focuses primarily on employing RAP materials in new pavement projects. Currently, new construction projects utilise a significant percentage of demolished asphalt pavement to save costs and natural resources. The key issue that arises when mixing RAP into new asphalt mixtures is the effects on the mixtures’ resistance to permanent disfigurements, such as fatigue cracks, that influence asphalt mixture performance. Numerous studies have assessed the impact of using RAP in asphalt mixtures and found that RAP increases the stiffness of asphalt mixtures, and thus improves rutting resistance at high temperatures. Nevertheless, the findings for thermal and fatigue cracking were found to be contradictory. This review will address the primary concerns regarding the use of RAP in asphalt pavements, and aims to encourage highway agencies and academic researchers in the Gulf countries to develop frameworks for the practical usage of RAP in the construction of sustainable pavement systems.
      Citation: Recycling
      PubDate: 2022-06-06
      DOI: 10.3390/recycling7030035
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 36: Does Policy on Plastic Waste Support Higher
           Waste Management Hierarchy Options'

    • Authors: Kunle Ibukun Olatayo, Paul T. Mativenga, Annlizé L. Marnewick
      First page: 36
      Abstract: There is an urgent and growing need to further advance the plastic waste management system globally and in South Africa, due to the increasing impact of plastic waste. This study focused on the adequacy of plastic policies to sustainably manage plastic waste. Policies need to address the plastic material supply systems and the options up the waste hierarchy for them to be effective and support material circularity. The study used qualitative content analysis to assess how the evolution of plastic policies for plastic waste management in South Africa aligned with national plastic material flows and promoted options higher up the waste hierarchy. This was benchmarked with Norway and Germany, which have some of the highest plastic recycling rates. The results showed that the evolution of existing plastic policies for South Africa addresses stages of production, trade and consumption, and recycling. There is no focus on waste generation, collection and sorting. None aligned with the waste hierarchy options of rethink, reduce, reuse, repair, refurbish, remanufacture and repurpose. This policy gap supports the need for broader national plastic policy frameworks that embed a policy drive in the value chain points and promote the priority higher value measures of the waste hierarchy.
      Citation: Recycling
      PubDate: 2022-06-08
      DOI: 10.3390/recycling7030036
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 37: Waste Management for Green Concrete
           Solutions: A Concise Critical Review

    • Authors: Magdalena Osial, Agnieszka Pregowska, Sławomir Wilczewski, Weronika Urbańska, Michael Giersig
      First page: 37
      Abstract: Reinforced concrete based on ordinary Portland cement (OPC) is one of the most commonly used materials in modern buildings. Due to the global growth of the building industry, concrete components have been partially or completely replaced with waste materials that can be used as binders or aggregates. Besides the ecological aspects, modern architecture widely needs materials to make the concrete durable, resisting large loads and various detrimental forces in the environment. This opens the possibilities of managing waste materials and applying them in practice. This paper presents a concise review of the green solutions for ecofriendly materials in the building industry that deal with the practical application of materials commonly treated as waste. The main emphasis was placed on their influence on the properties of the building material, optimal composition of mixtures, and discussion of the advantages and disadvantages of each of the “green” additives. It turned out that some solutions are far from being ecofriendly materials, as they leech and release numerous harmful chemicals into the environment during their presence in concrete. Finally, the paper suggests a research direction for the development of an ecofriendly structural material for a sustainable future.
      Citation: Recycling
      PubDate: 2022-06-10
      DOI: 10.3390/recycling7030037
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 38: An Overview of Packaging Waste Models in Some
           European Countries

    • Authors: Giacomo Di Foggia, Massimo Beccarello
      First page: 38
      Abstract: Efficient packaging waste management systems are essential considering recent revisions of the European legislation on packaging waste management that sets ambitious targets. European rules aim to deal with the increasing quantities of packaging waste, which cause environmental problems. Consequently, it is necessary to identify functional packaging waste management systems to achieve these targets effectively and efficiently. However, given the heterogeneity of the different packaging management systems, policymakers, scholars, and industry operators struggle to have a comparative view. The number of non-harmonized laws in force across countries, autonomous recycling targets, and constant updates are prominent problems that make it difficult to obtain comparable information for research, business, and policymaking. To fill this gap, our research question consists of assigning responsibilities for prevention, collection, recycling, and recovery and an overview of some models at a glance with respect to the general governance and functioning of the system. We base our research on a multiple-case design since more cases are examined using complementary data collection methods, analysis of the previous literature, reports, legislation, and business and institutional websites. Our results provide insights from the following cases: Germany, France, the United Kingdom, the Netherlands, Portugal, Denmark, Spain, and Italy. In addition, policy implications emerge as our insights help overcome barriers in the European market’s development caused by the different rules on packaging management and design serving policymakers that aim to harmonize the management of packaging waste. The paper also contains managerial implications for circular economy business models that can be used by managers who aim to design or upgrade their business models according to both recent legislative upgrades and packaging management systems.
      Citation: Recycling
      PubDate: 2022-06-10
      DOI: 10.3390/recycling7030038
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 39: Properties of Rubberized Concrete Prepared
           from Different Cement Types

    • Authors: Idriss, Gamal
      First page: 39
      Abstract: At present, global waste tire generation considerably exceeds consumption. Moreover, waste rubber tires (WRTs) are a cause of concern, as huge volumes are being discarded and buried, thus causing serious environmental pollution. Rubberized waste concrete (RWC) is a type of environmentally friendly construction material. The main challenge encountered when manufacturing rubberized concrete is the low adhesive properties between the cement paste and rubber particles. This paper demonstrates the effects, through experiments, of using waste tire rubber instead of recycled coarse aggregate (RCA) on two types of cement, i.e., sulfate-resistant cement (SRC) and ordinary Portland cement (OPC), where SRC is a specially blended cement designed to improve concrete performance and workability in the most aggressive environments. All tested samples contained 10% silica fume (SF) and 0.2% fly ash (FA), and the substitution of recycled aggregate content with waste rubber tier (WRT) at different percentages of 100%, 75%, and 50% was evaluated .The research investigated the synergistic effect on the workability and mechanical properties of various cement types with different amounts of rubber aggregate . It was found that the sulfate-resistant (SRC)type can increase the compressive strength than OPC with a percentage of 25% with the same content of WRT at concrete mix. Moreover, ductility and cracking behavior are improved, and it appears that it is also possible to make lightweight rubber aggregate concrete with this type of mixture. Using this type of cement, it is possible to restore satisfactory ductility to the waste tires, thus facilitating a reduction in the formation of potential plastic cracks. Moreover, the indicative compressive strength development for SRC with recycled rubber in concrete positively contributes to a reduction in formed cracks. However, SEM microstructural analyses suggest a higher proportion of C–S–H intermixed with sulfate reaction phases of SRC rubberized mortar than those of OPC; thus, given that crystal growth results in a decreased percentage of air voids rather than decreased internal cracking, it is clearly shown that the average crack width increases in OPC mortar compared with SRC. Finally, t-testing was used as an inferential statistical tool to determine whether there is a sizeable distinction between the properties of the two categories of materials, OPC and SRC, by comparing the mean and standard deviation of the values for compressive and tensile strength.
      Citation: Recycling
      PubDate: 2022-06-12
      DOI: 10.3390/recycling7030039
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 40: Rudimentary Assessment of Waste-to-Wealth of
           Used Tires Crumbs in Thermal Energy Storage

    • Authors: Hussain H. Al-Kayiem, Bilawal A. Bhayo, Elena Magaril, Pavithra Ravi
      First page: 40
      Abstract: Disposing of waste tires is a major environmental and economic issue. Different recycling methods have been studied to account for its re-usage. This project aims to evaluate the possible usage of shredded waste tires in thermal energy storage (TES) applications, whether they are sensible or latent materials. An experimental setup has been developed with seven compartments. Each compartment contains different TES materials, including tire crumbs, paraffin wax, paraffin wax with shredded tires, pebbles, pebbles with shredded tires, concrete, and concrete with shredded tires. In all cases of the mixture, the base materials are 60%vol, and the tire crumbs are 40%vol. The experimental included three locations for temperature measurements in each compartment, solar irradiation, and ambient temperature. The tests were carried out from 9:00 a.m. till 7:00 p.m. and repeated for five days to account for the weather’s daily change. Results revealed that mixed 60%vol pebbles and 40%vol shredded tires have the highest recorded temperature, at 112.5 °C, with a 39.5% increment compared to pure pebbles. The interesting finding is that the added tire crumbs reduced the storage capacity of the paraffin wax, which is latent TES material. At the same time, it increased the storage capacity of the concrete and pebbles, which are sensible TES materials. Adding 40%vol of tire crumbs to the paraffin wax has a negative effect, where the thermal storage capacity is reduced by 43%, and the discharge capacity is reduced by 57%. In contrast, the concrete and the pebbles show enhanced storage capacity. Adding 40%vol of crumbs to the concrete increased the charging capacity by 54% and discharging capacity by 33.7%. The 40%vol added tire crumbs to the pebbles increased its charging capacity by 25% and the discharging capacity by 33%. The rudimentary assessment encourages further investigations on using the wasted tires crumbs for TES. The results reveal the probability of a circular economy using wasted tires with sensible TES for solar-to-thermal energy conversion.
      Citation: Recycling
      PubDate: 2022-06-13
      DOI: 10.3390/recycling7030040
      Issue No: Vol. 7, No. 3 (2022)
  • Recycling, Vol. 7, Pages 41: Assessing Alternative Supporting Organic
           Materials for the Enhancement of Water Reuse in Subsurface Constructed
           Wetlands Receiving Acid Mine Drainage

    • Authors: Martha M. Oberholzer, Paul J. Oberholster, Luyanda L. Ndlela, Anna-Maria Botha, Johannes C. Truter
      First page: 41
      Abstract: Acid mine drainage (AMD) is a global problem with severe consequences for the environment. South Africa’s abandoned mines are a legacy from the country’s economic dependence on the mining sector, with consequent negative impacts on ecosystems. AMD remediation includes active and passive techniques. Constructed wetlands (a passive technique) have lower operational costs but require larger spaces and longer timeframes to achieve the remediation of AMD, and are supported by anaerobic sulphate-reducing bacteria (SRB), which capable of remediating high-sulphate-laden AMD while precipitating dissolved metals from the AMD. Organic substrates supporting these activities are often the limiting factor. When enhancing existing passive AMD remediation technologies, alternative waste material research that may support SRB activity is required to support the circular economy through the reduction in waste products. Chicken feathers show potential as a substrate enhancer, boosting organic carbon availability to SRB, which sustains passive AMD treatment processes by achieving pH elevation, sulphate and metal reductions in AMD water for reuse. Microbial biodiversity is essential to ensure the longevity of passive treatment systems, and chicken feathers are proven to have an association with SRB microbial taxa. However, the longer-term associations between the AMD water parameters, microbial diversity and the selected substrates remain to be further investigated.
      Citation: Recycling
      PubDate: 2022-06-14
      DOI: 10.3390/recycling7030041
      Issue No: Vol. 7, No. 3 (2022)
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