Recycling, Volume 6, Issue 1 (March 2021) – 22 articles

The volume of discarded solid wastes, especially plastic, which accumulates in large quantities in different environments, has substantially increased. Population growth and the consumption pattern of societies associated with unsustainable production routes have caused the pollution level to increase. Therefore, the development of materials that help mitigate the impacts of plastics is fundamental. However, bioplastics can result in a misunderstanding about their properties and environmental impacts, as well as incorrect management of their final disposition, from misidentifications and classifications. This chapter addresses the aspects and factors surrounding the biodegradation of bioplastics from natural (plant biomass (starch, lignin, cellulose, hemicellulose, and starch) and bacterial polyester polymers. Therefore, the biodegradation of bioplastics is a factor that must be studied, because due to the increase in the production of different bioplastics, they may present differences in the decomposition rates. Full article

The use of biomass as an energy source presents itself as a viable alternative, especially at a time when the mitigation of climate change requires that all possibilities of replacing fossil fuels be used and implemented. The use of residual biomass also appears as a way to include in the renewable energy production system products that came out of it, while allowing the resolution of environmental problems, such as large volumes available, which are not used, but also by the elimination of fuel load that only contributes to the increased risk of rural fires occurrence. Invasive species contribute to a significant part of this fuel load, and its control and eradication require strong investments, so the valorization of these materials can allow the sustainability of the control and eradication processes. However, the chemical composition of some of these species, namely Acacia dealbata, Acacia melanoxylon, Eucalyptus globulus, Robinia pseudoacacia and Hakea sericea, presents some problems, mainly due to the nitrogen, chlorine and ash contents found, which preclude exclusive use for the production of certified wood pellets. In the case of Eucalyptus globulus, the values obtained in the characterization allow the use in mixtures with Pinus pinaster, but for the other species, this mixture is not possible. From a perspective of local valorization, the use of materials for domestic applications remains a possibility, creating a circular economy process that guarantees the sustainability of operations to control and eradicate invasive species. Full article

Aseptic beverage cartons are multilayer polymer-coated paperboards with a layer of aluminum foil. Due to their multilayer structure it is commonly assumed that they cannot be recycled. This is not the case and this review details the multifarious processes that are used to recycle aseptic beverage cartons. Hydrapulping to recover the paper fibers that constitute 75% of the carton is the most widespread process, followed by the manufacture of construction materials such as boards and tiles which utilize the complete carton. A range of mechanical, chemical and thermal processes are used to separate the PolyAl (polyethylene and aluminum) residual that remains after the paper fibers have been recovered. The simplest process involves agglutination followed by extrusion to obtain pellets that can then be used in industrial and consumer products or combined with other materials such as lignocellulosic wastes. Chemical approaches involve the solubilization of polyethylene and the removal of aluminum. Various thermal processes have also been investigated and a novel microwave-induced pyrolysis process appears the most commercially viable. It is concluded that the focus in future years is likely to be on recycling cartons into construction materials where there is a theoretical yield of 100% compared with 75% for hydrapulping. Full article

The substitution of mineral aggregates with crumb rubber (CR) from waste end-of-life tires (ELTs) in the asphalt concretes, has been considered a sustainable paving industry approach. The rubber has been used to construct pavements with proven enhanced resilience and improved durability. However, some issues related to the rubber’s surface adhesion or swelling may arise with these practices and generate complications (binder consumption, temperatures, mixing times). One possible solution to overcome the materials’ compatibility problems is to pre-treat the CR’s surface before its incorporation into the asphalt mixes to allow a surface functionalization that can enhance coverage and cohesion inside the mixes. The physical treatments using radiations-based beam are already exploited in the plastic recycling industries avoiding the use of chemicals in considerable amounts. Such treatments permit the recovering of large quantities of polymer-based materials and the enhancement of interfacial properties. This article provides an overview of existing surface treatments of polymers and especially rubber, including gamma ray, UV-ozone, microwaves, and plasma. Several studies have shown an overall improvement of the rubber surface’s reactive properties due to contaminant removal or roughness enhancement attributed to cross-linking or scission reactions occurring on the rubber’s surface layer. With those properties, the asphalt mixes’ phase stability properties are increased when the pre-treated rubber is incorporated. The treatments would permit to increase the CR quantities, yet reduce the layer stiffness, and improve the durability and the sustainability of future advanced road pavements. Full article

This study examined HDPE (high-density polyethylene) plastic waste as an added material for concrete mixtures. The selection of HDPE was based on its increased strength, hardness, and resistance to high temperatures compared with other plastics. It focused on how HDPE plastic can be used as an additive in concrete to increase its tensile strength and compressive strength. 156 specimens were used to identify the effect of adding different percentages and sizes of HDPE lamellar particles to lower, medium, and higher strength concrete for non-structural applications. HDPE 0.5 mm thick lamellar particles with sizes of 10 × 10 mm, 5 × 20 mm, and 2.5 × 40 mm were added at 2.5%, 5%, 10%, and 20% by weight of cement. The results showed that the medium concrete class (with compressive strength equal to 10 MPa) had the best response to the addition of HDPE. The 5% HDPE addition represented the optimal mix for all concrete types, while the 5 × 20 mm size was best. Full article

The need to satisfy the increasing demand for building materials and the challenge of reusing plastic to help improve the critical environmental crisis has led to the recycling of plastic waste, which is further exploited and transformed into new and creative materials for the construction industry. This study looked into the use of low-density recycled polyethylene (LDPE) to produce non-conventional plastic sand cobbles. LDPE waste was melted in order to obtain enough fluid consistency which was then mixed with sand in a 25/75 plastic-sand ratio respectively, such a mixture helped producing cobbles of 10 cm × 20 cm × 4 cm. Water absorption, weight, and density measurements were performed on both commercial and non-conventional plastic sand cobbles. Moreover, compression, bending, and wear resistance were also conducted as part of their mechanical characterization. Plastic sand cobbles showed lower water absorption and density values than commercial cobbles. The mechanical properties evaluated showed that plastic sand cobbles have a higher modulus of rupture and wear resistance than commercial cobbles. In addition, plastic sand cobbles meet the Colombian Technical Standard in lightweight traffic for pedestrians and vehicle, officially known as Norma Técnica Colombiana (NTC), with 25.5 MPa, 16.3 MPa, and 12 mm compression resistance, modulus of rupture and footprint length in wear resistance respectively. Finally, a market study was conducted to establish a factory to produce this type of cobbles in Ibague, Colombia. Not only the study showed positive financial indicators, which means that it is feasible running a factory to manufacture plastic sand cobbles in the city of Ibague, but it also concluded that nonconventional plastic sand cobbles could be explored to provide a comprehensive alternative to LDPE waste. Full article

The recovery rate of construction materials is only 5% in China, which will lead to environmental and economic problems. Researchers from other countries have recognized the potential of building information modelling (BIM) in optimizing construction material recycling. However, previous research did not take the whole life cycle into consideration and was not practical enough. In this research, a questionnaire was conducted to find out how construction waste is disposed of in construction projects. Then, the existing research results were analyzed to find out how to apply BIM in the whole-life-cycle disposal of construction materials. According to the results of the questionnaire, landfill is the most common way to dispose of construction materials in China; besides this, almost no construction projects use BIM in material recycling. Hence, a BIM-based dynamic recycling model is proposed. Information management of materials, demolition planning, and BIM were all combined in this model for the purpose of optimizing the application of BIM, thus developing a waste material disposal system to achieve higher recovery rates and sustainability. More positive measures should be taken to deal with the problem of construction waste; if not, more environmental and economic problems will follow. Full article

The estimated production of world electronic waste until 2017 is approximately 6 Gt. Despite this enormous problem, there are no clear regulations regarding the orientation for disposal or treatment of this type of residuals in many countries. There is a federal public policy in Brazil that supports a network of Computer Reconditioning Centers—CRCs. These CRCs train young people and recover or recycle electronic equipment. Through this work, CRCs produce interlocking plastic pavers for application on pavements from recycled electronic industry waste. This article presents the characterization of these interlocking paver’s mechanical properties when applied on the pavement. This characterization is a necessary step to show the effectiveness of this product. We show that the plastic pavers behave similarly to the artifacts manufactured in concrete, thus creating commercial opportunities for this initiative, and contributing to the Brazilian Solid Waste Policy. Full article

Next-generation vehicles (NGVs), which mainly refers to hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs), electric vehicles (EVs), fuel-cell vehicles (FCVs), and clean diesel vehicles (CDVs), are becoming more and more popular as the potential answer to decreasing fossil fuel consumption and CO₂ emission from traffic sectors. Although the research on NGVs started in the 1990s, a systematic observation or summarization of the research on NGVs has not been performed yet. Thus, the current status, characteristics, latest trends, and issues of the research on NGVs have not been clarified yet. This research analyzed the research on NGVs recorded in the Web of Science published between 1990 to 2020 using CiteSpace, from a macro perspective. The results show that HVs and EVs are the crucial research objects in comparison with FCVs and CDVs. The research on NGVs was mainly performed by countries that own large vehicle makers or markets. However, it is noticeable that many developing countries have also started to study NGVs, which proves that NGVs have become popular globally. On the other hand, the research topics and categories of NGV study have always had a strong bias in favor of their function and technology development. Since NGVs have been sold for years in many countries already, there will be a considerable number of waste NGVs generated in the future, and so, future research should focus on recycling policies and/or recycling technology for NGVs to guarantee their sustainable development. Full article

Each year, more than 5 million Waste Mobile Phones (WMP) is generated in Japan. Since WMPs contain many rare metals and precious metals, it is essential to collect and recycle high-value metal resources from them effectively. Although multiple stakeholders have already developed WMP collection routes, these WMP collection routes’ current status is unclear. Furthermore, some WMP collection routes can only collect a small number of WMP, and so, their resource efficiency is low. This research aims to clarify each WMP collection route’s characteristics and evaluate their resource efficiency by conducting interview research on related stakeholders and the WMP dismantle experiment. The result shows that local government, authorized recyclers, and telecom carriers are the major stakeholders in collecting WMPs in Japan. To improve the WMP collection rate in cities with high population densities, using the local government’s collection route and installing an authorized recycler’s collection station is considered to be more effective. In cities with low population densities, the collection stations built by authorized recyclers are sufficient. The collection stations can also improve recycling behavior by offering points. Furthermore, the telecom carriers are encouraged to participate in the WMP collection business, but they should figure out a way to monitor the flow route of secondhand phones they exported and prompt the proper recycling of exported phones. Full article

Over the years, the world was not paying strict attention to the impact of rapid growth in plastic use. This has led to unprecedented amounts of mixed types of plastic waste entering the environment unmanaged. Packaging plastics account for half of the global total plastic waste. This paper seeks to give an overview of the use, disposal, and regulation of food packaging plastics. Demand for food packaging is on the rise as a result of increasing global demand for food due to population growth. Most of the food packaging are used on-the-go and are single use plastics that are disposed of within a short space of time. The bulk of this plastic waste has found its way into the environment contaminating land, water and the food chain. The food industry is encouraged to reduce, reuse and recycle packaging materials. A wholistic approach to waste management will need to involve all stakeholders working to achieve a circular economy. A robust approach to prevent pollution today rather than handling the waste in the future should be adopted especially in Africa where there is high population growth. Full article

In order to add value to recycled textile material and to guarantee that the input material for recycling processes is of adequate quality, it is essential to be able to accurately recognise and sort items according to their material content. Therefore, there is a need for an economically viable and effective way to recognise and sort textile materials. Automated recognition and sorting lines provide a method for ensuring better quality of the fractions being recycled and thus enhance the availability of such fractions for recycling. The aim of this study was to deepen the understanding of NIR spectroscopy technology in the recognition of textile materials by studying the effects of structural fabric properties on the recognition. The identified properties of fabrics that led non-matching recognition were coating and finishing that lead different recognition of the material depending on the side facing the NIR analyser. In addition, very thin fabrics allowed NIRS to penetrate through the fabric and resulted in the non-matching recognition. Additionally, ageing was found to cause such chemical changes, especially in the spectra of cotton, that hampered the recognition. Full article

Petroleum-derived products, such as lubricant oils, are non-renewable resources that, after use, must be collected and processed properly to avoid negative environmental impacts. A circular economy of used oils requires the re-refining and reuse of the same. Similar to most countries in Latin America, the management of used oils in Ecuador is still incipient and few cities collect and treat this material properly. In Cuenca, the ETAPA company collects ~1344 t/year of used oils, which are subjected to pretreatment operations prior to their use as fuel in a cement factory. However, combustion generates polluting gases and disallows the adding of value to the used oils. The lack of studies on the characterization and methods utilized for recovering used oils under the conditions found in medium-size Latin-American cities (e.g., Cuenca), alongside a lack of government policies, have hindered the adoption of re-refining operations. The objective of this work is to characterize the used lubricant oils in Cuenca, to compare them with the properties of used oils from other countries, and to suggest some re-refining technologies for oils with similar properties. Used oil samples were collected from mechanic shops and car-lubricating shops for characterization. Its physicochemical properties and metal contents are comparable to the used oils in other countries globally. Specifically, the flash point, kinematic viscosity, TBN, and concentrations of Zn, Cd, and Mg are similar to the properties of used oils in Iraq, Egypt, and the United Arab Emirates. Based on these results, the best re-refining option for used oils in Cuenca is extraction with solvents in which sedimentation and dehydration (already conducted in Cuenca) is followed by a solvent reaction process, a vacuum distillation process, a finishing process with bentonite, and a final filtration step. Full article

Despite the increase in popularity of the zero waste (ZW) concept, the successful implementation of this concept in waste management is still facing many challenges. The plastic recycling rate in Australia is at only about 9.4% (in 2017–2018). The state of Victoria (in Australia) has proposed an ambitious 10-year plan to upgrade its waste and recycling system and to divert about 80% of waste from landfills by 2030. The aim of this research is to study this currently proposed waste management plan and to develop a simulation model to assess the feasibility of achieving 80% diversion rate by 2030. The feasibility of achieving zero plastic waste by 2035 has also been assessed. In this direction, the existing knowledge of global ZW implementation has been reviewed to gain understanding of the challenges, obstacles, and uncertainties in achieving the ZW target. A simulation model is established using a method called double baselines. This method was developed to address the limitation of data availability for the model development. The model was run in 4 scenarios including one for Victoria’s current 10-year plan. Outcomes from the model are produced using six key considerations, including the rate of plastic consumption, waste to landfill, diversion rate, recycling rate, relative accumulative effort, and cost. The findings of this study point out that Victoria’s current plan for achieving an 80% diversion rate by 2030 is possible. On the other hand, the study results also suggest that achieving zero plastic waste by 2035 is less likely to happen. Hence, opportunities for improvement especially towards achieving the zero plastic waste are also presented. Full article

Efficient electronic waste (e-waste) management is one of the vital strategies to save materials, including critical minerals and precious metals with limited global reserves. The e-waste collection issue has gained increasing attention in recent years, especially in developing countries, due to low collection rates. This study aims to search for progressive solutions in the e-waste collection sphere with close-to-zero transport and infrastructure costs and the minimization of consumers’ efforts towards an enhanced e-waste management efficiency and collection rate. Along these lines, the present paper develops a smart reverse system of e-waste from end-of-life electronics holders to local recycling infrastructures based on intelligent information technology (IT) tools involving local delivery services to collect e-waste and connecting with interactive online maps of users’ requests. This system considers the vehicles of local delivery services as potential mobile collection points that collect and deliver e-waste to a local recycling enterprise with a minimum deviation from the planned routes. Besides e-waste transport and infrastructure costs minimization, the proposed smart e-waste reverse system supports the reduction of CO₂ through the optimal deployment of e-waste collection vehicles. The present study also advances a solid rationale for involving local e-waste operators as key stakeholders of the smart e-waste reverse system. Deploying the business model canvas (BMC) toolkit, a business model of the developed system has been built for the case of Sumy city, Ukraine, and discussed in light of recent studies. Full article

Solid Waste Management (SWM) is a multifaceted problem comprising political, socioeconomic, institutional, and environmental aspects. Due to exponential urban growth, it has become one of the most significant issues faced by urban spaces in developing countries. The gap in environmental knowledge among the youth and the old within developing countries contribute to ecological issues or waste management problems, resulting in unsustainable development, with important consequences in low-income countries. For that matter, a systematic review was conducted aiming to identify and analyse environmental knowledge, awareness, attitudes, and practice studies on SWM from 2010 to 2019 in developing countries. The evidence suggests that students at both secondary and tertiary levels have positive environmental attitudes, and high awareness of environmental issues, but there is a lack of practical education of teachers to guide students to put SWM into practice. Student’s low environmental knowledge is related to a deficiency in teachers’ practical experience in SWM for environmental sustainability. A relationship between teachers’ and students’ knowledge and attitudes towards SWM, as well as differences in awareness, attitude, and practices of SWM linked with education and age, were also found. This review also revealed that the lack of environmental education in most developing countries is caused by fragilities in practical environmental curricula of teachers to respond to modern-day environmental issues for sustainable development and cleaner production (CP). To bridge the knowledge gap between the youth and older people in SWM, environmental sustainability education should be integrated into schools at all levels within developing countries. Full article

Considering sustainable mining, the use of seawater in mineral processing to replace conventional water is an attractive alternative, especially in cases where this resource is limited. However, the use of this aqueous medium generates a series of challenges; specifically, in the seawater flotation process, it is necessary to adapt traditional reagents to the aqueous medium or to propose new reagents that achieve better performance and are environmentally friendly. In this research, the technical feasibility of using recycled vegetable oil (RVO) as a collector of copper sulfide minerals in the flotation process using seawater was studied. The study considered the analysis of the metallurgical indexes when different concentrations of collector and foaming reagent were used, considering as collectors the RVO, potassium amyl xanthate (PAX) and mixtures of these, in addition to the methyl isobutyl carbinol (MIBC) as foaming agent. In addition, it was evidenced that the best metallurgical indexes were achieved using 40 g/t of RVO and 15 g/t of MIBC, which corresponded to an enrichment ratio of 6.29, a concentration ratio of 7.01, a copper recovery of 90.06% and a selectivity index with respect to pyrite of 4.03 and with respect to silica of 12.89. Finally, in relation to the study of the RVO and PAX collector mixtures, it was found that a mixture of 60 g/t of RVO and 40 g/t of PAX in the absence of foaming agent presented the best results in terms of copper recovery (98.66%) and the selectivity index with respect to pyrite (2.88) and silica (14.65), improving PAX selectivity and recovery compared to the use of RVO as the only collector. According to these results, it is possible to conclude that the addition of RVO improved the selectivity in the rougher flotation for copper sulfides in seawater. This could be an interesting opportunity for the industry to minimize the costs of the flotation process and generate a lower environmental impact. Full article

Polymer recycling is nowadays in high-demand due to an increase in polymers demand and production. Recycling of such materials is mostly a thermomechanical process that modifies their overall mechanical behavior. The present research work focuses on the recyclability of high-density polyethylene (HDPE), one of the most recycled materials globally, for use in additive manufacturing (AM). A thorough investigation was carried out to determine the effect of the continuous recycling on mechanical, structural, and thermal responses of HDPE polymer via a process that isolates the thermomechanical treatment from other parameters such as aging, contamination, etc. Fused filament fabrication (FFF) specimens were produced from virgin and recycled materials and were experimentally tested and evaluated in tension, flexion, impact, and micro-hardness. A thorough thermal and morphological analysis was also performed. The overall results of this study show that the mechanical properties of the recycled HDPE polymer were generally improved over the recycling repetitions for a certain number of recycling steps, making the HDPE recycling a viable option for circular use. Repetitions two to five had the optimum overall mechanical behavior, indicating a significant positive impact of the HDPE polymer recycling aside from the environmental one. Full article

Since the early 1980s, a large number of studies on enzymes from the red king crab hepatopancreas were conducted. They have been relevant both from a fundamental point of view in terms of studying the enzymes of marine organisms and in terms of rational natural resource management aimed to obtain new valuable products from the processing of crab fishing waste. Most of these works were performed by Russian scientists due to the area and amount of waste of red king crab processing in Russia (or the Soviet Union). However, the close phylogenetic kinship and the similar ecological niches of commercial crab species and the production scale of the catch provide the bases for the successful transfer of experience in the processing of the red king crab hepatopancreas to other commercial crab species caught worldwide. This review describes the value of recycled commercial crab species, discusses processing problems, and suggests possible solutions for these issues. The main emphasis is made on hepatopancreatic enzymes as the most salubrious products of red king crab waste processing. Full article

In this work, an additive model for the prediction of the rheological and mechanical properties of monopolymer blends made by virgin and reprocessed components is proposed. A polypropylene sample has been reprocessed more times in an extruder and monopolymer blends have been prepared by simulating an industrial process. The scraps are exposed to regrinding and are melt reprocessed before mixing with the virgin polymer. The reprocessed polymer is, then, subjected to some thermomechanical degradation. Rheological and mechanical experimental data have been compared with the theoretical predictions. The results obtained showed that the values of this simple additive model are a very good fit for the experimental values of both rheological and mechanical properties. Full article

In many cities of third world countries, managing waste represents a beehive of activities that involve human scavengers searching for reusable or recyclable items that are either consumed or sold to generate funds for personal and family upkeep, since alternative decent employment are not available for them in the formal employment sector. Many of these waste pickers are young, work without the necessary health and safety apparatus, and expose themselves to injury and various health hazards. Therefore, this study investigated the working conditions and career aspirations of waste pickers in Lagos State, Nigeria. Using the questionnaire approach, structured, semi-structured, and open-ended questions were asked, and the Statistical Package for Social Science (SPSS) was used to descriptively analyze the data collected and interpreted. The results showed that 87% of waste pickers in Lagos State have safety kits. In addition, the results showed flexibility in working hours and days since most waste pickers get to determine when and how they begin their work, i.e., 89% of the waste pickers spend 5 to 6 days a week in waste picking while 64% of them work between 10 and 14 h daily. Regarding earnings, the results showed that 68.3% of waste pickers earn between ₦2500 ($8.2) to ₦4900 ($16) daily. Finally, the results showed that despite access to safety kits, most waste pickers (54%) had experienced one form or another of hazard which has affected their career aspiration. Therefore, based on the study results we recommend that the Lagos State and the Nigerian federal government should develop a system that ensures strict compliance to established rules or guidelines that ensures the safety and health of waste pickers on the job. Full article