Recycling Concepts Research Articles

Recovery of pure PET from wool/PET/elastane textile waste through step-wise enzymatic and chemical processing

Textile waste is mostly incinerated because few recycling processes are available to recover valuable materials. In this work, a feasible chemo-enzymatic recycling process of wool/polyethylene terephthalate (PET)/elastane blends to recover pure PET is for the first time successfully demonstrated. Two novel enzyme formulations were selected for wool hydrolysis, whereas the recovered amino acids were quantified using high-performance liquid chromatography and two assays (Ninhydrin and Folin–Ciocalteu). Kinetic studies on the amino acid formation alongside reaction observations by scanning electron microscopy proved sufficient removal of wool within 8 hours with the new enzyme formulation, marking an acceleration compared to previous studies. Finally, elastane was separated with a non-hazardous solvent to obtain pure PET. Tensile tests on the recovered PET fibres reveal only slight changes through the enzymatic treatment and no changes induced by the applied solvent. The enzyme formulation was successfully tested on five different post-consumer wool/PET textile waste samples. This valorization approach enhances the circular economy concept for textile waste recycling.

Crystallization of Bis(2-hydroxyethylene) Terephthalate as a Part of a Bottle-to-Bottle Recycling Concept for Poly(ethylene terephthalate).

The chemical recycling of poly(ethylene terephthalate) (PET) is very attractive as PET bottle waste provides an abundant clean material with low levels of additives. One of the most promising processes is glycolysis, which depolymerizes PET in the presence of ethylene glycol. For this process, it is necessary to think through the whole concept, from the waste material to the newly polymerized virgin polymer. Most research ends with determining the yield of bis(2-hydroxyethyl)terephthalate (BHET) after glycolysis. Some research includes antisolvent crystallization with water to separate BHET from ethylene glycol. However, the subsequent separation of water and ethylene glycol is an energy-intensive process. Therefore, this work aims to directly crystallize BHET from ethylene glycol. For this reason, the crystallization of BHET was investigated experimentally. Crystallization was simulated using gPROMS Formulated Products with the aim of estimating kinetic parameters and using these to optimize an industrial process. Kinetic parameters were determined by model validation, including primary and secondary nucleation and crystal growth. The best-fitting set of kinetic parameters was used to optimize BHET crystallization in batch and continuous modes by minimizing equipment costs. Impeller parameters were found to have a great influence on crystallization performance. Ultimately, the continuous and batch processes gave comparable results in terms of equipment cost, with the batch process giving larger crystals and higher yields but the continuous process requiring a smaller crystallizer.

Recycling of Blended Fabrics for a Circular Economy of Textiles: Separation of Cotton, Polyester, and Elastane Fibers

The growing textile industry is polluting the environment and producing waste at an alarming rate. The wasteful consumption of fast fashion has made the problem worse. The waste management of textiles has been ineffective. Spurred by the urgency of reducing the environmental footprint of textiles, this review examines advances and challenges to separate important textile constituents such as cotton (which is mostly cellulose), polyester (polyethylene terephthalate), and elastane, also known as spandex (polyurethane), from blended textiles. Once separated, the individual fiber types can meet the demand for sustainable strategies in textile recycling. The concepts of mechanical, chemical, and biological recycling of textiles are introduced first. Blended or mixed textiles pose challenges for mechanical recycling which cannot separate fibers from the blend. However, the separation of fiber blends can be achieved by molecular recycling, i.e., selectively dissolving or depolymerizing specific polymers in the blend. Specifically, the separation of cotton and polyester through dissolution, acidic hydrolysis, acid-catalyzed hydrothermal treatment, and enzymatic hydrolysis is discussed here, followed by the separation of elastane from other fibers by selective degradation or dissolution of elastane. The information synthesized and analyzed in this review can assist stakeholders in the textile and waste management sectors in mapping out strategies for achieving sustainable practices and promoting the shift towards a circular economy.

Educational practices for improvement of sustainability education at secondary school level

In the future of education, concepts of sustainability and recycling have to become integral parts of core subjects which require interdisciplinary collaboration beyond subject borders. Project-based Learning offers the perfect educational environment for such integration of knowledge not limited by single subject curricula or school curricula in general. At the same time, it offers a hands-on approach to actively in- volve students in the creation of products as well as the training of skills for critical thinking and problem-solving, but also increases their awareness regarding sustainability and environmental challenges. In this context, the goals of a circular economy are supported by such an educational approach combined with an environmental focus.

Waste separation intention of households in Sri Lanka

Abstract The effective practice of waste separation at the source is crucial for achieving sustainable development and promoting the reduce, reuse, and recycle concept. This practice should be adopted by both households and business organisations. The primary objective of this study is to investigate the factors that influence the intention of waste separation at the household level in Sri Lanka. For this purpose, a random selection of 388 households representing the entire country was undertaken. Independent variables, including attitude, perceived cost benefits, moral norms, inconvenience, and rules and regulations, were examined in relation to their impact on the dependent variable, which was the intention of waste separation. A 5-point Likert scale questiommaire was utilised to assess each of these variables. The methodology employed in this study included principal component analysis, factor analysis, and Structural Equation Model (SEM) to establish the underlying model. The results of the analysis revealed the significance of attitude, perceived cost benefits, and moral norms at a 5% significance level. Interestingly, although inconvenience exhibited a negative influence on intention, its significance was not established. Furthermore, while existing literature commonly attributed local government rules and regulations as a significant factor, the model indicated a positive and insignificant relationship. In conclusion, this study underscores the importance of positive attitudes, perceived benefits in terms of cost, and adherence to moral norms in fostering the intention for waste separation. Despite the negative impact of inconvenience not reaching statistical significance, it remains a noteworthy consideration. Additionally, the unexpected positive and insignificant relationship with local government rules and regulations prompts further exploration.

Role of Biomass Gasification in Achieving Circular Economy

Growing awareness of environmental concerns and the prioritisation of environmental stewardship necessitates the incorporation of sustainability practices that are both economical and profitable. This involves transforming existing industrial practices from the ‘take-make-waste’ approach to one that aligns with the principles of a circular economy. This includes the use and restoration of bioreserves or the cycling of products in a manner that minimizes waste generation by employing the concepts of reuse and recycling. The adoption of circular economy principles is especially critical in energy-intensive industries, and there is increased attention to implementing these principles through biomass gasification. Various methodologies exist for utilizing the potential of biomass by employing biomass gasification to achieve the desired levels of energy output. Techniques incorporating circular economy principles for biomass gasification have become increasingly sought after and achieved widespread implementation in the past few decades. In this paper, we examine the principle of a circular economy and how biomass gasification can be leveraged in processes requiring high-energy input to achieve the same.

Development of a recycling machine for constructing synthetic yarn from plastic waste

A major challenge in plastic recycling is to convert plastic waste into a useful product. For this transformation, sustainable technologies such as plastic recycling machines are required. Current technological concepts of plastic recycling are fairly similar. This study aims to develop a small and economical plastic recycling machine to enhance microenterprise by supplying simple equipment for recycling locally processed plastic waste into thread. Starting with a hopper at the input end, the machine incorporates an auger inside a barrel, which is then linked to a metallic perforated mold at the output end. With the help of the system, the plastic flakes melting process is facilitated by maintaining temperatures between 170 °C to 211 °C at equispaced locations of a uniform barrel, while the auger spin enables the flow of molten plastic forward towards the mold.The mold reshapes the liquid plastic into strings of thread. The machine exhibits higher efficiency, reaching approximately 75 % at a decreased screw speed, as low as 28 rpm. It also achieves an average throughput of 156 gm/hour at the lowest specific mechanical energy (SME) consumption. The prototype consumes 1.5 kW for an hour operation. The entire system requires minimal space, making it appealing to individuals with limited financial resources to start a new business venture.•A sustainable technology to recycle plastic waste into plastic thread.•This optimized, portable and robust system ensures safety and lower operating costs.•This system does not require prior knowledge for operation, hence encouraging small entrepreneurs.

Atomic hydrogen production in a cold plasma for application in a metal foil pump

Any good design of fuel cycles for thermonuclear fusion reactors, which operate on deuterium-tritium fusion, comes with minimized tritium inventory. The direct internal recycling concept can significantly reduce the tritium inventory of a fusion power plant by introducing a bypass for most of the unburned fuel from the torus exhaust. It requires a technology that can sharply separate hydrogen isotopes from other gases in the given environment in the reactor's pump duct. The prime candidate for this task is a metal foil pump (MFP) using plasma-driven permeation. A workflow toward a performance predicting modeling tool of a MFP is introduced. It is based on the characterization of the employed cold plasma by using a plasma simulation, which is experimentally validated using optical emission spectroscopy and the actinometry method. The used approach accounts for the radial inhomogeneity of the linearly extended plasma. We determine the atomic hydrogen content down to pressures of 1 Pa and condense the complex processes that contribute to the hydrogen atom production into a single excitation probability. This value can be used in Monte Carlo based modeling approaches to determine the particle exhaust performance of the vacuum pump.

Manajemen Lingkungan dan Pengolahan Sampah Rumah Tangga dan Minyak Jelantah menjadi Nilai Ekonomi di Kelurahan Kalibaru

Kalibaru Village is a lowland area which has relatively hot temperatures located in Bekasi City. Sub-optimal waste management in Kalibaru Village can have a negative impact and various environmental problems such as flooding, worsening environmental sanitation, decreasing organic content in the environment, and accelerating global warming. In addition to public awareness that is still low not to throw away used cooking oil resulting from food processing, it also has a great potential to pollute the environment. But not only awareness is needed by the community but also programs that can overcome this pollution by converting household waste and used cooking oil into economic value. Seeing the problems in Kalibaru Village in environmental management, a work program can be developed that refers to the waste bank program. Of course, to realize this, it is necessary to have cooperation between universities and the community, it is hoped that this work program can create a cleaner, more beautiful and healthier environment. The stages that will be carried out related to the implementation of Community Service include the Observation & Focus Group Discussion stages (Phase 1). At this stage, a direct observation is carried out to analyze the situation and conditions of partners. Evaluation of advanced programs that are in line with waste management through waste banks and waste cooking oil processing has economic value. Stage 2, namely developing a waste bank program, aims to change people's behavior in handling waste and used cooking oil (reduce reuse recycle concept). By separating the waste, this waste has economic value. Stage 3, then converting waste and used cooking oil into having economic value and turning waste into input for environmental improvement and developing the scalability of waste banks to be able to manage waste even better and be able to sustain it.

Solusi Recycle Sampah Organik dan Anorganik bagi Keluarga di Perumahan Taman Dramaga Permai 2 Bogor

Households are one of the contributors to organic and inorganic waste. Generally, the family needs to manage waste independently. The concept of waste recycling can be applied at the household level. The aim of waste management in the Dosen Mengabdi Reguler 2022 was to provide alternative solutions for processing organic and inorganic waste in the household based on the recycling concept. The activities were carried out from July‒November 2022 in one of the villages around the IPB campus locations, namely the Taman Darmaga Permai 2, Cihideung Ilir, Ciampea, Bogor. The core activities consist of discussions and demonstrations about compost, coenzymes, re-growing vegetable plants, and the culture of mung bean sprouts from Vima 1 and Vimil 1 varieties. About 42.9% of the 14 participants sorted household waste, and 28.6% managed waste. Compost from organic waste was harvested within one month after the process, while coenzymes were harvested after three months. Ecoenzymes were attractive to all participants as a solution for processing waste. About 50% of participants favor growing vegetables and 21.4% re-grow vegetable waste. Katuk and Welsh onion plants have 100% growth and 90% survival rates. All participants had never sprouted mung bean seeds. The sprouts can be harvested 1 to 3 days after sowing as needed. The Vima 1 mung bean variety has a sweet sprout taste and produces 657.9 g of sprouts from 100 g of seeds, while the Vimil 1 taste is slightly astringent with a lower sprout production of 543.8 g.

Okul Öncesi Dönem Çocuklarının Çevre ve Geri Dönüşüm Farkındalığı Üzerine Bir Eylem Araştırması

The aim of the study was to determine how applied recycling studies carried out in the preschool period (60-72 months) affected children's awareness of the concepts of environment and recycling. Action research model was used in the research in which qualitative research design was adopted. The study group of the research consisted of eight preschool children studying in a kindergarten class of a public school affiliated with the Ministry of National Education in Boztepe District of Kırşehir Province. Data of the research; It was obtained through student drawings and semi-structured interview forms. Data were analyzed using the MAXQDA data analysis program. As a result of the research, it was observed that children's environmental awareness changed positively and they especially paid attention to the integrity of nature with living things. It was determined that there was a positive change in the children's knowledge of the concepts of "not garbage" and "reused" and that they expressed these concepts correctly. Keywords: Environmental awareness, recycling, preschool

Концепция «Медленный город» как перспективное направление развития малых и средних городов России

In modern conditions requiring rational use of resources, increasing the efficiency of management of small and medium-sized cities is a complex and multifaceted task facing public authorities. The study considered the possibility of solving it based on foreign experience in this area. The works of domestic and foreign scientists on the problem of the development of small and medium-sized cities built the methodological basis of the study. The purpose of the study is to analyze foreign approaches to the development of small and medium-sized cities and determine the possibility of their implementation in relation to Russian small and medium-sized cities using the example of the Sverdlovsk region. The authors studied foreign concepts of 15-minute city, Walkable city, Land recycling and Slow city (Cittaslow), their key idea and main directions of implementation. The Cittaslow concept was chosen to assess the possibility of implementation in domestic practice. Unlike the others considered, it is represented by a wide geography of implementation, including in Russia (Svetlogorsk city). The authors developed an original methodology to assess the possibility of using the Cittaslow concept, which was tested in a number of small and medium-sized cities in the Sverdlovsk region. Based on the results obtained, recommendations are given for planning the further socio-economic development of the studied municipalities.

Circular recycling concept for silver recovery from photovoltaic cells in Ethaline deep eutectic solvent

Metallic silver is directly recovered from photovoltaic cells by leaching and electrodeposition in Ethaline deep eutectic solvent associated with a redox shuttle that can be regenerated to start a new cycle.

Consumer Behaviour in a Circular System – How Values Promote and Hinder the Participation of Young Adults in the Swedish Deposit-Refund System for Beverage Packaging

This study contributes to the understanding of how values promote and hinder circular consumer behaviour by examining and learning from the Swedish deposit-refund system for beverage cans and PET bottles. We have used the consumption value theory in our analysis, building on the concepts of circular economy, sustainable consumption and recycling. Data was collected from focus group interviews with young adults in order to identify and explore the ways that values promote and hinder participation. Functional values were found to be at the core of sustainable consumption as a result of financial incentives and the fact that consumers value convenience. The study also highlights the importance that young adults place on emotional values, in particular embarrassment, which hinders them from recycling. When it comes to sustainable consumption, young adults are driven by selfish behaviour, prioritising personal comfort. Social settings were also found to promote and hinder participation in the deposit-refund system. The study finds that an understanding of the reasons why different social groups and age groups approve or disapprove of participation in circular solutions may help design solutions to increase participation in circular solutions and circular economies. The results show that it is important to study the combinations of value dimensions to understand consumer behaviour in a circular system fully.

A comprehensive comparison of the life-cycle environmental impacts of traditional and returnable express delivery packaging in China

China's express delivery service industry has been experiencing rapid development; in 2021, deliveries reached a total of 108.29 billion. However, with the increasing demand for express packaging and the accompanying environmental pressures, the widespread adoption of returnable mailing packaging has become a key consideration to promote the reduce, reuse, and recycle (3R) concept. This study performed a life cycle assessment (LCA) and analyzed the environmental impacts of returnable packaging with respect to those of traditional packaging. Five scenarios were established, including traditional express bags and boxes as well as returnable bags and boxes. Results revealed that the comprehensive environmental impact value of returnable packaging bags is 1.75 × 10−5 per capita equivalent (PE), representing 59% and 26% reductions compared to the waste incineration and recycling paths of plastic bag packaging, respectively. Additionally, the comprehensive environmental impact value of box-type returnable packaging is 1.85 × 10−4 PE, which is 63% lower than that of carton-type express packaging. To reduce pollution and greenhouse gas emissions, returnable express boxes and bags should be reused at least five and fifteen times, respectively.

Power to gas and top gas recycling integration in an oxygen blast furnace steelmaking industry

A new process concept integrating power to methane with top gas recycling in an oxygen blast furnace (BF) is investigated to reduce the emission intensity of steelmaking. Power to gas produces synthetic methane using hydrogen (H2) generated by an electrolyser operated with renewable electricity, and CO2 captured from the BF gas by amine scrubbing supplied with heat from the methanation process. The clean gas from the amine scrubbing is recycled and injected in the BF (via top gas recycling), together with synthetic methane. A parametric analysis is performed to vary the amount of top gas recycled (from 0 kg/tHM to 270 kg/tHM). Based on the results, CO2 equivalent emissions can decrease by 34% using power to gas technology, and by 30% with power to gas and top gas recycling (compared to conventional BFs). Nevertheless, if both integrations are present, additional benefits on the specific energy consumption (12.0 MJ/tHM), and specific cost (130 €/tHM) are achieved, compared to only applying power to gas (17.5 MJ/tHM and 233 €/tHM). In all cases, the downstream thermal energy needs of the steel plant are fulfilled, contrarily to conventional top gas recycling concepts. The main conclusion is that top gas recycling should be considered together with PtG technology, and vice versa, when integrated in blast furnace ironmaking, in order to both abate emissions while supplying downstream energy needs.

Integrating climate change practices in a circular economy context—The perspective from chemical enterprises

AbstractThis study describes the relationships between climate change and the concept of a circular economy, outlining the need for synergies within a company's context. It reports on a bibliometric analysis of the relations between climate change and circular economy, and it provides evidence and assessments based on a sample of 11 large companies in the chemical industry. The results show that there is a concern in the academic literature to discuss circular economy efforts to combat climate change, reduce carbon emissions, strengthen the supply chain, assess the life cycle of products, their environmental impact, and waste management, and identify barriers to implementing the circular economy. In addition, there is a close association between the CE concept and tackling climate change in how organisations report their practices to the stakeholders, in considering concepts of recycling, reusing, adopting renewable energy, seeking resource efficiency, and rethinking strategies. The study concludes by providing some suggestions that may assist companies in intensifying their efforts to reduce their carbon footprint, combining them with more circular business models. Efforts from interested stakeholders must focus on defining CE in a more detailed manner, as well as its implementation at the different stages of production and consumption, especially in operations for which no uniform approach or common practice can be established. In this context, implications for positive social and environmental impacts by promoting a faster and more proactive climate transition in the chemical sector are presented. The novelty of this paper relies on the fact that it advances knowledge on matters related to the circular economy under a climate change context, identifying current trends and suggesting some measures which may optimise current business practices of the chemical sector.

Hydrophobic building blocks enable unprecedented durability for chemically recyclable and biodegradable polymer

The widespread usage and improper disposal of conventionally non-degradable petrochemical-based polymers have led to anabatic energy depletion, significant resource shortages, and severe environmental concerns, motivating the development of polymers that combine chemical recyclability, biodegradability, and mechanical properties suitable for applications. However, there remains an irreconcilable contradiction between property retention in service and post-use degradation or recycling in this category of polymers. Herein, through the introduction of hydrophobic building blocks, a biodegradable polymer that shows excellent mechanical properties (elongation at break of 891.5 ± 23.2%, and maximum strength of 56.9 ± 0.9 MPa) and good thermal stability (decomposition temperature of approximately 290 °C) was obtained. Moreover, the polymer possessed not only easy-access-to-monomer recyclability (yield of 95.4% and purity of 99.9%) but also unprecedented durability (elongation-at-break retention of 54.4 ± 7% and maximum-strength retention of 79.6 ± 14% on the 30th day) under highly moist air (25 °C, relative humidity (RH) of 90%). In addition, the origins and mechanism of the performance improvement were investigated, and a proof of concept for chemical closed-loop recycling between monomers and polymers was demonstrated.

Sustainable Construction with Energy-efficient Materials

Due to the overuse of energy, water, land, and other resources as a result of urbanisation and industrialization, the natural ecosystem has become unbalanced. Rapid industrialization has resulted in the accumulation of millions of tonnes of varied industrial wastes at numerous locations, which has severely harmed the ecosystem. In India, demolition wastes from built-up areas also produce a sizable amount of debris, including sand, gravel, concrete, stone, and bricks. The demand-supply gap can be partially filled by recycling aggregate materials from construction and demolition debris and using industrial wastes for the production of valuable building materials. This essay focuses on the concepts of recycling and reusing, creating income from trash, and the proper use of waste in the production of building materials.

Conceptions and Feasibility Study of Fiber Orientation in the Melt as Part of a Completely Circular Recycling Concept for Fiber-Reinforced Thermoplastics

Fiber-reinforced thermoplastics are an important construction material for lightweight applications. The increasing use of especially glass fiber-reinforced plastics leads to growing amounts of not recyclable composite materials, which is commonly disposed of by landfilling. Hence, there is a need for a recycling concept for glass-fiber-reinforced plastics that enables their complete reuse over many recycling cycles. In this paper, such a recycling concept is presented, which is based on the idea of melting the whole glass-fiber-reinforced component without prior size reduction. The fiber-reinforced melt will be pressed through a nozzle in order to achieve a strand with highly oriented fibers that can then be applied in new components via a tape-like laying process. The feasibility of the recycling concept is proved in this paper. Therefore, investigations on the reorientation of fibers in the melt by pressing through a rectangular nozzle have been carried out with different nozzle diameters, shear rates and melt temperatures. The investigations result in a stable process, which enables an increase in fiber orientation of about 37% up to a mean fiber orientation of 67% in the flow direction. These findings are independent of the initial fiber orientation.