Recycling, Volume 7, Issue 5 (October 2022) – 19 articles

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. Full article

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. Full article

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, T_g, T_m, 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. Full article

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. Full article

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 CO_2e 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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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