Recycling

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article