The management of waste through dual way of recycling (i-e offline and online) is assumed to have a key role in attaining ecological sustainability and enabling circular practices. The research on online recycling is gaining evolution in recent age. Prior literature on the current research theme has failed to provide a comprehensive outlook and future trend. Therefore, the current research intends to elaborate the current research scenario linked with online recycling by critically scrutinizing the prior research over the last 41 years. A comprehensive analysis was conducted using the Scopus database, retrieving a total of 866 articles. These articles were selected to provide a conceptual overview and understanding of the fundamental research conducted in the field. By employing bibliometric analysis this research provides comprehensive detail about evolution, mapping of publications and prominent trends from the year 1981 to 2022 to understand the practices and future trends of online recycling research. The outcomes elucidated that there is exponential increase in research publications relating to online recycling over the last five years. The most influential producer of online recycling research are China, United Kingdom and United States. Chinese Universities has the highest number of publications among all the countries across globe. Moreover, the current research trend is focused on technology based circular economy, industrial ecology, bio-based waste management, dual channel recycling, municipal waste, waste from electrical and electronic equipment (WEEE), environmental impact and lifecycle assessment. Hence, the prominent research perspective and highlighted features could offer recommendation for upcoming studies to contribute in literature and help practitioners, policymakers and professionals move towards circular practices.
Due to the rapid increase in the use of electrical and electronic equipment (EEE) worldwide, e-waste has become a critical environmental issue for many governments around the world. Several studies have pointed out that failure to adopt appropriate recycling practices for e-waste may cause environmental disasters and health concerns to humans due to the presence of hazardous materials. This warrants the need for a review of the existing processes of e-waste management. In view of the growing e-waste generation in the Asia Pacific region and the importance of e-waste management, this study critically reviews previous research on e-waste generation and management practices of major e-waste producing nations (Australia, China, India, Indonesia, and Malaysia) in the Asia Pacific region, provides an overview of progress made and identifies areas for improvement. To fulfil the aims of this research, previous studies from 2005 to 2020 are collected from various databases. Accordingly, this study focuses on e-waste generation and environmental management of these countries. This study found that e-waste management practices of the selected countries need to be enhanced and recommends several best practices for effectively managing e-waste.
Management of waste is one of the major challenges faced by many developing countries. This study therefore attempts to develop a circular economy (CE) model to manage wastes and closing the loop and reducing the generation of residual wastes in Indian municipalities. Through extant literature review, the researchers found 30 success factors of CE implementation. Using the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) SIMOS approach, the rating and weight of decision makers (DMs) for each factor were collected. A structured questionnaire has been developed incorporating all these 30 factors, to extract the most important factors. The data was collected from top 10 officials (DMs) from the Chennai municipality, who handle three regions (metropolitan, suburbia and industrial). Based on the TOPSIS SIMOS analysis, nine CE implementing factors (critical success factors (CSFs)) among the 30 variables that were significant based on the cut-off value was identified. A CE model has been proposed based on these nine CSFs for waste management in India.
In recent years, off-site volumetric construction has been promoted as a viable strategy for improving the sustainability of the construction industry. Most prefabricated prefinished volumetric construction (PPVC) structures are composed of either steel or concrete; thus, it is imperative to carry out life cycle assessments (LCAs) for both types of structures. PPVC is a method by which free-standing volumetric modules-complete with finishes for walls, floors, and ceilings-are prefabricated and then transferred and erected on-site. Although many studies have examined these structures, few have combined economic and environmental life cycle analyses, particularly for prefinished volumetric construction buildings. The purpose of this study is to utilize LCA and life cycle cost (LCC) methods to compare the environmental impacts and costs of steel and concrete PPVCs "from cradle to grave." The results show that steel necessitates higher electricity usage than concrete in all environmental categories, while concrete has a higher emission rate. Steel outperforms concrete by approximately 37% in non-renewable energy measures, 38% in respiratory inorganics, 43% in land occupation, and 40% in mineral extraction. Concrete, on the other hand, performs 54% better on average in terms of measures adopted for greenhouse gas (GHG) emissions. Steel incurs a higher cost in the construction stage but is ultimately the more economical choice, costing 4% less than concrete PPVC owing to the recovery, recycling, and reuse of materials. In general, steel PPVC exhibits better performance, both in terms of cost and environmental factors (excluding GHG emissions). This study endeavors to improve the implementation and general understanding of PPVC.
Recovery of cellulose fibres from paper mill effluent has been studied using common polysaccharides or biopolymers such as Guar gum, Xanthan gum and Locust bean gum as flocculent. Guar gum is commonly used in sizing paper and routinely used in paper making. The results have been compared with the performance of alum, which is a common coagulant and a key ingredient of the paper industry. Guar gum recovered about 3.86mg/L of fibre and was most effective among the biopolymers. Settling velocity distribution curves demonstrated that Guar gum was able to settle the fibres faster than the other biopolymers; however, alum displayed the highest particle removal rate than all the biopolymers at any of the settling velocities. Alum, Guar gum, Xanthan gum and Locust bean gum removed 97.46%, 94.68%, 92.39% and 92.46% turbidity of raw effluent at a settling velocity of 0.5cm/min, respectively. The conditions for obtaining the lowest sludge volume index such as pH, dose and mixing speed were optimised for guar gum which was the most effective among the biopolymers. Response surface methodology was used to design all experiments, and an optimum operational setting was proposed. The test results indicate similar performance of alum and Guar gum in terms of floc settling velocities and sludge volume index. Since Guar gum is a plant derived natural substance, it is environmentally benign and offers a green treatment option to the paper mills for pulp recycling.
In light of concerns relating to improper waste disposal and resources preservation, reclamation of the discarded glass in construction materials had been extensively carried out since 1963. In the past decade, although more than 100 papers associated with the use of glass powder (GP) in the micron level scale were published, comprehensive review of all practical applications in cement-based materials and construction products is not available. This paper therefore provides a summary of the body of knowledge on the interaction and effects of using GP in cement-based and extended construction materials. This review concludes that GP is an innovative and promising eco-supplementary cementitious material. Beyond that, use of GP is demonstrated to be potentially beneficial as a precursor in geopolymer and suitable for manufacturing eco-cement, artificial lightweight aggregate and composite phase change material. The multiple applications of GP are seen as an important step towards waste glass recycling as a sustainable construction material and for the overall betterment of the industry.
To tackle the crisis associated with the rising commercial food waste generation, it is imperative to comprehend how corporates' recycling behaviour is influenced by different industry structures and economies. This study aims to fill in the information gap that various factors might be affecting corporates' recycling behaviour in two different economies due to environmental inequality by comparing upper-middle-income region (Malaysia) and high-income region (Hong Kong), respectively. A questionnaire survey regarding food waste management according to the Theory of Planned Behaviour was conducted with representatives coming from diverse industries of the hotel, food and beverage, and property management. The questionnaire responses were evaluated based on quantitative structural equation modelling and correlation analysis. The analysis results showed that the model fit the data well, explaining 78% of the variance in recycling behaviour. The findings demonstrated that the most substantial factor on individual's recycling intention by Malaysian commercial food waste generators was perceived behavioural control, and logistics and management incentives. Subjective norms demonstrated significant and adverse effects on the behaviour of food waste recycling. The variable of administrative incentives and corporate support presented strong positive correlations with moral attitudes as well as logistics and management incentives. Hotel industries from both Hong Kong and Malaysia have a higher acceptance level on human resources regarding food waste recycling. In comparison, food and beverage industries from both regions have a lower acceptance level. These findings could enrich our knowledge of the concerns in establishing regional policy strategies to encourage economic behavioural changes for sustainable development.
A novel approach for the determination of Al(3+) from aqueous samples was developed using an optode membrane produced by physical inclusion of Al(3+) selective reagent, which is morin into a plasticized poly(vinyl chloride). The inclusion of Triton X-100 was found to be valuable and useful for enhancing the sorption of Al(3+) ions from liquid phase into the membrane phase, thus increasing the intensity of optode's absorption. The optode showed a linear increase in the absorbance at λ(max)=425 nm over the concentration range of 1.85×10(-6)-1.1×10(-4) mol L(-1) (0.05-3 μg mL(-1)) of Al(3+) ions in aqueous solution after 5 min. The limit of detection was determined to be 1.04×10(-6) mol L(-1) (0.028 μg mL(-1)). The optode developed in the present work was easily prepared and found to be stable, has good mechanical strength, sensitive and reusable. In addition, the optode was tested for Al(3+) determination in lake water, river water and pharmaceutical samples, which the result was satisfactory.
In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO2/Al2O3 membrane was packed with potassium hydroxide catalyst supported on palm shell activated carbon. The central composite design (CCD) of response surface methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst amount and cross flow circulation velocity on the production of biodiesel in the packed bed membrane reactor. The highest conversion of palm oil to biodiesel in the reactor was obtained at 70 °C employing 157.04 g catalyst per unit volume of the reactor and 0.21 cm/s cross flow circulation velocity. The physical and chemical properties of the produced biodiesel were determined and compared with the standard specifications. High quality palm oil biodiesel was produced by combination of heterogeneous alkali transesterification and separation processes in the packed bed membrane reactor.
The disposal and littering of cigarette butts (CBs) is a serious environmental problem. Trillions of cigarettes are produced every year worldwide, resulting in millions of tonnes of toxic waste being dumped into the environment in the form of cigarette butts. As CBs have poor biodegradability, it can take many years for them to break down. This paper reviews and presents some of the results of a study on the recycling of CBs into fired clay bricks. Bricks with 2.5%, 5%, 7.5%, and 10% CB content by weight were manufactured and tested, and then compared against control clay bricks with 0% CB content. The results showed that the dry density decreased by up to 30% and the compressive strength decreased by 88% in bricks with 10% CBs. The calculated compressive strength of bricks with 1% CBs was determined to be 19.53Mpa. To investigate the effect of mixing time, bricks with 7.5% CB content were manufactured with different mixing times of 5, 10, and 15min. To test the effect of heating time on the properties of CB bricks, the heating rate used during manufacturing was changed to 0.7, 2, 5, and 10°Cmin(-1). Bricks with 0% and 5% CB content were fired with these heating rates. Leachate tests were carried out for bricks with 0%, 2.5%, 5%, and 10% CB content. The emissions released during firing were tested for bricks with 0% and 5% CB content using heating rates of 0.7, 2, 5, and 10°Cmin(-1). The gases tested were carbon monoxide (CO), carbon dioxide (CO2), chlorine (Cl2), nitrogen oxide (NO), and hydrogen cyanide (HCN). Finally, estimations were made for the energy that could be saved by firing bricks incorporating CBs. Calculations showed that up to 58% of the firing energy could potentially be saved. Bricks were shown to be a viable solution for the disposal of CBs. They can reduce contamination caused by cigarette butts and provide a masonry construction material that can be either loadbearing or non-loadbearing, depending on the quantity of CBs incorporated. This paper proposes the use of bricks with 1% CB content throughout the brick-manufacturing industry. If bricks contained as little as 1% CB content, they would still provide a solution for the issue of CB recycling while maintaining properties very similar to those of a non-CB brick. Our calculations show that, theoretically, only 2.5% of the world's annual brick production is necessary to completely offset the worldwide, annual cigarette production.
Studies on sustainable management of waste from electrical and electronic equipment (or e-waste) have gained increasing attention from researchers around the world in recent years, with investigations into various aspects of e-waste management were investigated. Studies on e-waste generation by previous papers have been reviewed to provide an overview of the current research progress and recommendations for future research. The relevant existing studies were collected from various databases. Using content analysis, three main aspects of the existing studies were evaluated: the distribution and trends of the publications, the scope and boundaries of the studies, and the current research practices and research applications. Although there was a significant increasing trend of the amount of research on the evaluation of e-waste generation, however, the number of publications based on the countries of origin was still small. Another limitation was found related to the differences in the selection of research subjects and the level of analysis resulted in variations in the scopes and boundaries of the existing studies. Various other research areas were investigated further based on their research findings, but the analysis of various methodological aspects was complicated due to the increasing number of newly developed methodologies and the lack of comprehensive and up-to-date reviews on this research area. Additionally, there was also a need to evaluate emerging and/or older technology, which led electrical appliances to be overlooked. We found that comprehensive and up-to-date reviews of the methodological aspects of e-waste generation are still lacking. Based on the research gaps and limitations discussed, recommendations for future research were made.
Recently Xiamen (China) has encountered various challenges of municipal solid waste management (MSWM) such as lack of a complete garbage sorting and recycling system, the absence of waste segregation between organic and dry waste at source, and a shortage of complete and clear information about the MSW generated. This article critically analyzes the existing bottlenecks in its waste management system and discusses the way forward for the city to enhance its MSWM by drawing lessons from Hong Kong's effectiveness in dealing with the same problems over the past decades. Solutions to the MSWM problem are not only limited to technological options, but also integrate environmental, legal, and institutional perspectives. The solutions include (1) enhancing source separation and improving recycling system; (2) improving the legislation system of the MSWM; (3) improvement of terminal disposal facilities in the city; (4) incorporating digitization into MSWM; and (5) establishing standards and definitions for recycled products and/or recyclable materials. We also evaluate and compare different aspects of MSWM in Xiamen and Hong Kong SAR (special administrative region) under the framework of 'One Country, Two Systems' concerning environmental policies, generation, composition, characteristics, treatment, and disposal of their MSW. The nexus of society, economics of the MSW, and the environment in the sustainability sphere are established by promoting local recycling industries and the standardization of recycled products and/or recyclable materials. The roles of digitization technologies in the 4th Industrial Revolution for waste reduction in the framework of circular economy (CE) are also elaborated. This technological solution may improve the city's MSWM in terms of public participation in MSW separation through reduction, recycle, reuse, recovery, and repair (5Rs) schemes. To meet top-down policy goals such as a 35% recycling rate for the generated waste by 2030, incorporating digitization into the MSWM provides the city with technology-driven waste solutions.
Photocatalytic fuel cell (PFC) is considered as a sustainable green technology which could degrade organic pollutant and generate electricity simultaneously. A synergistic double-sided ZnO/BaTiO3 loaded carbon plate heterojunction photoanode was fabricated in different ratios by using simple ultrasonication and mixed-annealed method. The double-sided design of photoanode allowed the lights irradiated at both sides of the photoanode. The ferroelectricity fabricated photoanode was applied in a membraneless PFC with platinum-loaded carbon as the cathode. Results revealed that the photoanode with 1:1 ratio of BaTiO3 and ZnO exhibited a superior photocatalytic activity among all the photoanodes prepared in this study. The heterojunction of this photoanode was able to achieve up to a removal efficiency of 93.67% with a maximum power density of 0.5284 μW cm-2 in 10 mg L-1 of Reactive Red 120 (RR120) without any supporting electrolyte. This photoanode was able to maintain at high performance after recycling 3 times. Overloading of ZnO above 50% on BaTiO3 could lead to deterioration of the performance of PFC due to the charge defects and light trapping ability. The interactions, interesting polarizations of the photocatalysts and proposed mechanism of the n-n type heterojunction in the photoanode of ZnO/BaTiO3 was also discussed.
This paper provides preliminary evidence ofthe need foraccounting for trash management in public organizations, in particular, UniversitiMalaysia Terengganu (UMT). It has two objectives: tosolicit opinions from students regarding their behaviorsand perceptions towards recycling habits,and to provide data on the extent of accounting for trash management at UMT. A survey among155 UMT students indicatedthat theyrecycled the trashandwereaware of environmental issues caused by the waste. However, they were not informed about the benefits of environmental management accounting practice particularly regardingtrash management. Interviewswith UMT management also revealed that while UMT supported recycling activities byfunding the projects and providing facilities, the data on the opportunity cost involved in the current practice was never integrated into UMT accounting system. As a result, the management hadno idea of how much was lost (or gained) during the process. Based on the findings,this study callsfor the implementation of accounting for trash management in a public university.
Microencapsulated paraffin wax/polyaniline was prepared using a simple in situ polymerization technique, and its performance characteristics were investigated. Weight losses of samples were determined by Thermal Gravimetry Analysis (TGA). The microencapsulated samples with 23% and 49% paraffin showed less decomposition after 330 °C than with higher percentage of paraffin. These samples were then subjected to a thermal cycling test. Thermal properties of microencapsulated paraffin wax were evaluated by Differential Scanning Calorimeter (DSC). Structure stability and compatibility of core and coating materials were also tested by Fourier transform infrared spectrophotometer (FTIR), and the surface morphology of the samples are shown by Field Emission Scanning Electron Microscopy (FESEM). It has been found that the microencapsulated paraffin waxes show little change in the latent heat of fusion and melting temperature after one thousand thermal recycles. Besides, the chemical characteristics and structural profile remained constant after one thousand thermal cycling tests. Therefore, microencapsulated paraffin wax/polyaniline is a stable material that can be used for thermal energy storage systems.
This study evaluated the use of alginate-immobilized bentonite to remove Cu(II) as an alternative to mitigate clogging problems. The adsorption efficacy (under the influence of time, pH and initial Cu(II) concentration) and reusability of immobilized-bentonite (1% w/v bentonite) was tested against plain alginate beads. Results revealed that immobilized bentonite demonstrated significantly higher sorption efficacy compared to plain alginate beads with 114.70 and 94.04 mg Cu(II) adsorbed g(-1) adsorbent, respectively. Both sorbents were comparable in other aspects where sorption equilibrium was achieved within 6 h, with optimum pH between pH 4 and 5 for adsorption, displayed maximum adsorption capacity at initial Cu(II) concentrations of 400 mg l(-1), and demonstrated excellent reusability potential with desorption greater than 90% throughout three consecutive adsorption-desorption cycles. Both sorbents also conformed to Langmuir isotherm and pseudo-second order kinetic model. Immobilized bentonite is therefore recommended for use in water treatments to remove Cu(II) without clogging the system.
Microalgae are rich in valuable biomolecules and grow on non-arable land with rapid growth rate, which has a host of new possibility as alternative protein sources. In the present study, extraction of proteins from Chlorella vulgaris via an efficient technique, Liquid Triphasic Flotation (LTF) system, was studied. The optimized conditions in LTF system were 70% v/v of t-butanol, 40% w/v of salt solution, 0.5% w/v of biomass, pH 5.54, 1:1 of salt to t-butanol solution, and 10 min of air flotation time to attain 87.23% of protein recovery and 56.72% of separation efficiency. Besides, the study on recycling t-butanol has demonstrated that only one run was sufficient to maintain the performance of system. The efficiency of LTF in extracting protein has performed better than just Three Phase Partitioning (TPP) system. LTF system is hence an effective protein extraction and purification method with minimum operation unit and processing time.
Associated with the continuing increase of construction activities such as infrastructure projects, commercial buildings and housing programs, Bangladesh has been experiencing a rapid increase of construction and demolition (C&D) waste. Till now, the generation rate of C&D waste has not been well understood or not explicitly documented in Bangladesh. This study aims to provide an approach to estimate C&D waste generation using waste generation rates (WGR) through regression analysis. Furthermore, analyses the economic benefit of recycling C&D waste. The results revealed that WGR 63.74 kg/m2 and 1615 kg/m2 for construction and demolition activities respectively. Approximately, in financial year (FY) 2016, 1.28 million tons (0.149 construction and 1.139 demolition) waste were generated in Dhaka city, of which the three largest proportions were concrete (60%), brick/block (21%) and mortar (9%). After collection they were dumped in either landfills or unauthorized places. Therefore, it can be summarized as: waste is a resource in wrong place. The results of this study indicate that rapid urbanization of Dhaka city would likely experience the peak in the generation of C&D waste. This paper thus designates that C&D waste recycling is an entrepreneurial activity worth venturing into and an opportunity for extracting economic and environmental benefits from waste. The research findings also show that recycling of concrete and brick waste can add economic value of around 44.96 million USD. In addition, recycling of C&D waste leads to important reductions in CO2 emissions, energy use, natural resources and illegal landfills. Therefore, the findings of WGR and economic values provide valuable quantitative information for the future C&D waste management exercises of various stakeholders such as government, industry and academy.
This research aims to analyse and understand recycling phenomena and competition between large-scale and small-scale enterprises under different public attention. It mainly emphasizes service-providing behaviours to the consumers in the recycling industry, where recyclers are struggling to enhance their profits. The government strives to protect the environment by promoting an efficient recycling industry. As fast-growing waste products, the recyclers should achieve the advantage of number and be equipped with service capability for the consumers. Thus, this study employs an evolutionary game model to analyse the competition for waste products acquisitions between large and small recyclers. Due to a significant association between the service and acquisition waste product price for the consumers and recycling quantity, there is a strong mutual influence between the acquisition price of waste products and the price strategy-taken rate of large and small recyclers. Results also reveal that the market acquisition price and processing cost play a crucial role in recyclers' decision-making on setting prices for acquiring waste products from consumers. Furthermore, it is also found that waste products acquisition price and recyclers' processing cost are the key factors that affect large and small recyclers' recycling quantity.
Paving block is a widely used pavement material due to its long service life, fast and easy production and easily replaced for maintenance purpose. The huge production volume of paving blocks consumes large amount of natural aggregates such as sand and granite. Therefore, there is a necessity to review the utilization of alternative materials as the aggregate replacement to cut down both the consumption of natural resources and disposal of various waste. This paper thus analyses published works and provides a summary of knowledge on the effect of utilizing selected waste materials such as soda-lime glass, cathode ray tube (CRT) glass, recycled concrete waste, marble waste, crumb rubber (CR) waste and waste foundry sand (WFS) as aggregate replacement in concrete paving blocks fabrication. The influence of each waste material on the properties of paving block is discussed and highlighted in this paper. The adherence of the waste material paving block to the standard requirements is also presented to provide a clear direction on the utilization of these materials for practical application. Soda-lime glass, CRT glass, pre-treated RCA and calcined WFS have the potential to be utilized in high quantities (30-100%), normal RCA and marble waste can be incorporated in moderate amount (30%) while CR waste and WFS is limited to low amount (6-10%). In overall, the usage of waste materials as aggregate replacement has good potential for producing eco-friendly concrete paving block towards the sustainable development of construction material.