Recycling — Open Access Journal

This paper presents a brief description of some existing models of facility location problems (FLPs) in solid waste management. The study provides salient information on commonly used distance functions in location models along with their corresponding mathematical formulation. Some of the optimization techniques that have been applied to location problems are also presented along with an appropriate pseudocode algorithm for their implementation. Concerning the models and solution techniques, the survey concludes by summarizing some recent studies on the applications of FLPs to waste collection and disposal. It is expected that this paper will contribute in no small measure to an integrated solid waste management system with specific emphasis on issues associated with waste collection, thereby boosting the drive for effective and efficient waste collection systems. The content will also provide early career researchers with some necessary starting information required to formulate and solve problems relating to FLP. Full article

In this paper, we report a study on the use of a linear triblock copolymer based on styrene and ethylene/butylene (SEBS) and a polypropylene (PP)-based olefin block copolymer (OBC) for improving the impact strength of a recycled polypropylene (PP) from packaging waste. Talc was used as a reinforcing filler in order to prepare a material suitable for being used in the automotive sector. The composite mixtures were prepared by melt extrusion, and the samples were manufactured by injection molding. Impact strength was evaluated by Izod tests, and a morphological study of the produced fractures was performed. As a result, a composite with substantially improved impact properties was prepared, with a two-fold increase of the impact strength in the case of unnotched specimens, while only a limited positive effect was produced on notched specimens. Since talc-filled PP is a typical material used in the automotive sector, the obtained results demonstrate that post-consumer PP coming from the municipal waste collection of plastic packaging can be successfully used in car components with no compromise in terms of mechanical requirements. Full article

The effects of poor solid waste management practices in many developing countries have been identified in the literature. This study focuses on understanding the public perception and attitudes of people towards local waste management practices. Five Local Government Areas in Ogun State, Nigeria, were selected based on population, landmass, spatial location, and distribution. The study used a survey that looked into the socio-demographics, household characteristics, and standard solid waste disposal practices at the household and municipal levels. Factors such as frequency of waste collection, presence of environmental task force/protection agency, and level of effectiveness of such task force/agency were all investigated. The study verified the impact of people’s attitudes towards waste management, as well as the effects of monitoring and control on the management of waste. The results showed that significant factors such as age, income, and education levels affect the perceptions, practices, and attitudes of the people towards solid waste management. An average of 36.6% of the people in the selected local governments dispose of their solid wastes at open dumps, with the majority of the residents (54.4%) still with the opinion that sanitation services are too costly and should be the prerogative of the local and state governments to carry out. These outcomes resonate that more efforts by the government and relevant stakeholders should be put into proper enforcement of environmental laws, as well as creating awareness on proper solid waste management practices in schools and public places. Full article

Several theories and case studies have shown that information has little or no direct influence on waste sorting behavior. However, it is often suggested that information plays a vital role by indirectly influencing behavior. This contribution sheds light on how instructive information influences users of a recycling scheme in terms of perception, knowledge and waste sorting behavior. The study was performed as a case study on a student population in a medium-sized city in Sweden. An intervention in the form of modified information that was provided to the users was studied. This information was instructive in nature and adapted to the participants’ needs using the Recycling Behavior Transition procedure, where the users are involved in the development and modification of recycling schemes. New information was designed after investigating how the participants perceived the original information on correct waste sorting, as well as ascertaining their preferred channel for providing the information. Pick analyses and surveys were conducted before and after providing the user-adapted information. The results indicated a trend towards correct participation in the recycling scheme. These results are also discussed in the theoretical context of the Motivation-Opportunity-Ability-Behavior model. The study shows that user-adapted, instructive information can have a significant influence on people’s knowledge of correct waste separation and their overall perception of information. Full article

Given the increasing efforts at improving waste management in developing countries, this study aimed to analyze factors that influence participation in household waste sorting. It thereby is the first review that extends the published literature on this topic. A meta-analysis was conducted that analyzed twelve influencing factors. A moderate correlation was found for the most strongly influential factors—attitude, moral norm, subjective norm and perceived behavior control—which indicates that people’s perception of waste sorting is most influencing in prompting participation in household waste sorting in developing countries. The results of this meta-analysis indicate that knowledge, situational factors, such as physical conditions, and governmental incentives can influence participation in household waste sorting in developing countries but the relationship between those factors and other factors with high correlations should be studied further. Notably, socio-demographic factors have the weakest influence on the participation in waste sorting in developing countries despite a large body of research on such factors. It can be constructive to take the relationship across the identified factors and the participation in waste sorting into consideration when aiming to implement measures to increase the participation in waste management schemes through waste sorting. The outcome of this study may contribute to recommendations and policy suggestions regarding the promotion of sustainable waste management through household waste sorting in developing countries. Full article

In this paper, the brightness of fly ash is improved by carbon removal by heating and iron-containing oxides removal by acid treatment using a two-step method to realize the application of fly ash as filler or coating in the future, which not only increases the range of resource utilization of fly ash, but also reduces dust pollution. The modification results show that the brightness of fly ash reaches the maximum value of 38.27% ISO (Brightness unit) after decarburization by heating at 600 °C. On this basis, the Box–Benhnken design scheme is adopted to optimize the brightening process for removing iron-containing oxides in fly ash. Finally, when the concentration of hydrochloric acid is 15%, the acid leaching time is 0.75 h, the reaction temperature is 74 °C, and the brightness of fly ash can eventually increase to 43.92% ISO. Full article

Recycling and recovery provide not only a sustainable option to decrease the volume of waste that needs final disposal, but also a blueprint to a circular economy. However, rates of recycling/recovery still remain very low on a global scale. While it is important to look for technology-based solutions to improve recycling/recovery activities, such solutions might not be necessarily affordable in many countries. A solution that involves the active participation of the population, on the other hand, has the potential to succeed in any country. The challenge is to attract and unite people to achieve such common goals. The theory of collective action and the Institutional Analysis and Development (IAD) framework, that have been originally used in resource management, are two concepts that can be adapted to organize recycling/recovery initiatives. This manuscript discusses what recycling/recovery programs can learn from the theory of collective action and the IAD framework, through a qualitative comparative study of such initiatives from three different cities. They are; Curitiba in Brazil, Padang in Indonesia, and Akure in Nigeria. The cases show the potential benefits of both concepts, not only in formulating and implementing recycling/recovery programs but also in making corrective measures for continuous improvements. All cases also showed the importance of increasing awareness-raising to change public perception towards waste from being a nuisance to a valuable resource. Full article

Environmental concerns about waste management systems have stimulated the search for technological and economical alternatives that introduce waste as raw material for production cycles. In this sense, this study aimed to develop and characterize styrene-butadiene rubber (SBR) composites that contain industrial rubber scraps devulcanized by microwaves (SBR-r) as a reinforcing filler. The scraps were ground under ambient conditions. From the obtained powder (SBR-r), composites were prepared, varying the exposure time of the powder to the microwaves (1, 2, and 3 min), as well as the SBR-r content. These composites were compared to a Reference sample (base formulation without SBR-r). The vulcanization parameters were determined by an oscillating disk rheometer. After vulcanization, the composites were characterized by mechanical properties (tensile and tear strength, and compression set). These properties were also evaluated after accelerated aging in an air oven and a UV chamber (ultraviolet light). The results indicated that as a result of increasing the exposure time of the waste to the microwaves, no significant influence in the composite properties was observed. Aged samples presented higher results as compared with the Reference sample (tensile strength up to 175% higher, tear strength up to 107% higher, and compression set up to 91% higher), which indicates the possibility of using these materials in technological applications, such as in the civil and automotive industries. Full article

This work shows a proposed room prototype and its thermal behavior evaluation. The room was built by using polyethylene terephthalate (PET) bottles filled with soil from the site for its walls and a roof made of multiple layers of reused materials. The construction had a green roof and skylights that were constructed out of upcycled entire glass bottles. Thermal measurements were made indoors and outdoors over the course of one year. Temperature and humidity sensors were used for internal measurements, and, at the same time, a reference sensor recorded data that corresponded to external environmental conditions. The constructed building differed by an average of 8.5 °C from the reference measurements of the external environment and an average of 24.24% in relative humidity. Thermograms were taken from the outside walls, which reached 54.2 °C, while internal wall temperatures reached 25.5 °C. Additionally, a thermal transfer simulation of the prototype was accomplished by using COMSOL Multiphysics. Simulation results approximated the experimental data. The prototype had low daily thermal fluctuations, which was considered a desirable thermal behavior. These results, along with the self-building practices, low costs, and reuse of waste materials, makes this kind of building a potentially feasible alternative. Full article

A sustainable alternative to the destination of polyethylene (PE) residue from the prepreg package was established. This work intends to develop nanocomposites for packaging containing neat low-density polyethylene (LDPE), a compatibilizer agent (maleic anhydride grafted-LDPE, LDPE-g-MA), recycled LDPE obtained from the protective films of prepreg (rLDPE) and montmorillonite (MMT). The rLDPE, from the prepreg shield, has a primary role during the transport and storage of prepreg, which can be composed of epoxy resin and carbon fiber or glass fiber. However, this rLDPE is withdrawn and discarded, besides, it is estimated that tons of this material are discarded monthly by the company Alltec Materiais Compostos Ltd. (São José dos Campos-SP, Brazil). Due to several factors, including the lack of technology for recycling, the majority of this material is incinerated. In this context, this work presents a technical and ecologically viable alternative for the use of this discarded material. Nanocomposites of LDPE/rLDPE blends and montmorillonite (MMT) with different contents (0.0, 1.0, and 3.0 wt%) and with the addition of compatibilizer agent (LDPE-g-MA) were prepared by extrusion process. Test specimens were obtained by hot pressing in a hydropneumatic press followed by die-cutting. The nanocomposites produced using rLDPE presented good mechanical, thermal, and morphological properties, being the ideal concentration of 1 wt% MMT. Thus, the results obtained confirmed the viability of recycling LDPE from the prepreg package which contributes to the reduction of waste and the use of this material in technological applications. Full article

The European Union (EU) identified a number of raw materials that are strategic for its economy but suffer at the same time from a high supply risk. Such critical raw materials (CRMs) are used in a wide range of commercial and governmental applications: green technology, telecommunications, space exploration, aerial imaging, aviation, medical devices, micro-electronics, transportation, defense, and other high-technology products and services. As a result, the industry, the environment, and our quality and modern way of life are reliant on the access and use of them. In this scenario, recycling may be a strategic mitigating action aimed at reducing the critical raw materials supply risks. In this work, a design strategy is proposed for alloys selection that minimizes the number of CRMs with the lowest end-of-life recycling input rate. The method is illustrated with an example. Full article

Current product composition and quality test methods for the paper and pulp industries are rooted in wet-bench chemistry techniques which cannot be used to distinguish between virgin and secondary fibers. We have recently demonstrated the application of an in situ and nondestructive assessment method based on dielectric spectroscopy (DS), which can address this deficiency in the testing of paper. The DS technique, which employs a resonant microwave cavity, could be applicable to quality assurance techniques such as gauge capability studies and real-time statistical process control (SPC), and may have inherent forensic capabilities. In this paper, we show how this DS technique can be used to distinguish between office copier paper products which may contain recycled fibers. We show a reasonable correlation between the dielectric characteristics (e.g., dielectric loss) and the atomistic level chemical changes that result from the paper recycling process. Full article

The existing solid waste management principles are increasingly being replaced with discussions on circular economy (CE) principles in contemporary deliberations on solid waste handling. This shift is supported by the global adoption of the concept of sustainable development. The CE offers better prospects to solid waste management and has been implemented successfully in its full theory, practice, and policies in some developed locations of the world. The socio-economic disadvantages, insufficient expert knowledge and a lack of information have hindered its appropriateness and implementation in low and middle-income countries. Hence, the current research study examines the challenges and opportunities of implementing the circularity principle at the industrial sector level of a typical developing economy—Nigeria. Four different industries were selected for this case study—telecommunications, water packaging, pulp and paper and the food industry. These industries represent the major waste streams in an urban solid waste mix (waste electrical and electronic equipment (WEEE), plastic, paper and organic). This study discovered several barriers and existing pre-conditions in place that could either foster or militate against the smooth and successful application of a CE model as a simple modification of the generic model. This study also discussed future directions on the implementation of the model. Full article

In recent years, Next-Generation Vehicles, especially Hybrid Vehicles (HV) are increasing rapidly in advanced countries. In fact, not only advanced countries but also some developing countries also own a large quantity of HV by importing secondhand HV from advanced countries. For instance, Mongolia is importing a huge amount of secondhand HV from Japan every year. On the other hand, there will be a huge amount of waste HV in Mongolia that needs to be recycled properly soon, and yet, this problem has been neglected and the number of waste HVs in Mongolia is still unknown. The purpose of this research is to propose a method to predict the End-of-Life HV number in Mongolia. This research finds that the Japanese vehicle deregistration rate can represent vehicles’ durability and can be used to estimate End-of-Life HV number in Mongolia. The result shows that there will be a huge amount of End-of-Life HV as well as Nickel-Metal Hydride (NiMH) batteries generated in Mongolia from now on, even more than in Japan, which is the largest HV market. It is urgent for the Mongolian government to build a proper End-of-Life HV recycling system now, and international cooperation on resource circulation is also expected. Full article

This work contributes to the recycling of technical black plastic particles, for example from the automotive or electronics industries. These plastics cannot yet be sorted with sufficient purity (up to 99.9%), which often makes economical recycling impossible. As a solution to this problem, imaging fluorescence spectroscopy with additional illumination in the near infrared spectral range in combination with classification by machine learning or deep learning classification algorithms is here investigated. The algorithms used are linear discriminant analysis (LDA), k-nearest neighbour classification (kNN), support vector machines (SVM), ensemble models with decision trees (ENSEMBLE), and convolutional neural networks (CNNs). The CNNs in particular attempt to increase overall classification accuracy by taking into account the shape of the plastic particles. In addition, the automatic optimization of the hyperparameters of the classification algorithms by the random search algorithm was investigated. The aim was to increase the accuracy of the classification models. About 400 particles each of 14 plastics from 12 plastic classes were examined. An attempt was made to train an overall model for the classification of all 12 plastics. The CNNs achieved the highest overall classification accuracy with 93.5%. Another attempt was made to classify 41 mixtures of industrially relevant plastics with a maximum of three plastic classes per mixture. The same average classification accuracy of 99.0% was achieved for the ENSEMBLE, SVM, and CNN algorithms. The target overall classification accuracy of 99.9% was achieved for 18 of the 41 compounds. The results show that the method presented is a promising approach for sorting black technical plastic waste. Full article

Some industrial wastes are shown to be useful in the production of mullite ceramics. These industrial wastes are rich in certain metal oxides such as silica (SiO₂) and alumina (Al₂O₃). This gives wastes the potential to be used as a starting material source for mullite ceramics preparation. The purpose of this review paper is to compile and review various mullite ceramics preparation methods that utilized a variety of industrial wastes as starting materials. This review also describes the sintering temperatures and chemical additives used in the preparation and its effects. A comparison of both mechanical strength and thermal expansion of the reported mullite ceramics prepared from various industrial wastes were also addressed in this work. Full article

This study seeks to find the influence of replacing a portion of the asphalt–rubber binder with the bio-based material “guayule resin.” This replacement could be beneficial in terms of sustainability, economics, and environmental concerns related to the asphalt industry. Nine asphalt–rubber–guayule binders were investigated to find their rheological properties. Consecutively, the study proceeded with five selected binders being compared to the original asphalt (PG64-22). Investigations underwent whole matrices (crumb rubber modifier (CRM) residue included) and liquid phases (CRM residue extracted). Additionally, these properties were partially sought for their corresponding asphalt–rubber binders to compare and judge the contribution of the guayule resin. Likewise, a thermo-gravimetric analysis was done for the guayule resin to recognize its moisture and composition complexity. Such an analysis was also done for the as-received CRM and some extracted CRMs to determine the release and residue of rubber components. Outcomes showed that the guayule resin has the potential to compensate the performance required against the original asphalt at elevated temperatures while greatly decreasing the asphalt cement proportion. For instance, a blend of 62.5% asphalt, 12.5% CRM, and 25% guayule resin provided better performance than that of the original asphalt. Full article

The melt conditioned direct chill (MC-DC) casting process has been used for the production of billets of AA-6111 alloy formulated from recycled aluminium derived from incinerator bottom ash (IBA). The billets were homogenised and then extruded into planks. Optical metallography of the MC-DC billets showed equiaxed refined grains in comparison to DC and grain refined (DC-GR) billets formulated from the same scrap source. Microstructure evaluation for the extruded planks showed a less extensive peripheral coarse grain (PCG) for the MC-DC sample. Full article