Showing papers in "Resources Conservation and Recycling in 2021"

A critical analysis of the impacts of COVID-19 on the global economy and ecosystems and opportunities for circular economy strategies

Abstract: The World Health Organization declared COVID-19 a global pandemic on the 11th of March 2020, but the world is still reeling from its aftermath. Originating from China, cases quickly spread across the globe, prompting the implementation of stringent measures by world governments in efforts to isolate cases and limit the transmission rate of the virus. These measures have however shattered the core sustaining pillars of the modern world economies as global trade and cooperation succumbed to nationalist focus and competition for scarce supplies. Against this backdrop, this paper presents a critical review of the catalogue of negative and positive impacts of the pandemic and proffers perspectives on how it can be leveraged to steer towards a better, more resilient low-carbon economy. The paper diagnosed the danger of relying on pandemic-driven benefits to achieving sustainable development goals and emphasizes a need for a decisive, fundamental structural change to the dynamics of how we live. It argues for a rethink of the present global economic growth model, shaped by a linear economy system and sustained by profiteering and energy-gulping manufacturing processes, in favour of a more sustainable model recalibrated on circular economy (CE) framework. Building on evidence in support of CE as a vehicle for balancing the complex equation of accomplishing profit with minimal environmental harms, the paper outlines concrete sector-specific recommendations on CE-related solutions as a catalyst for the global economic growth and development in a resilient post-COVID-19 world.

A Comprehensive Review on Recycled Aggregate and Recycled Aggregate Concrete

Abstract: Using recycled aggregate s from construction and demolition waste can preserve natural aggregate resources, reduce demand of landfill, and contribute to sustainable built environment. This study provides a comprehensive review on recycled aggregate (RA) and recycled aggregate concrete (RAC) regarding their history, recycling, reuse and manufacture process, inherent defects (e.g. existing of additional interfacial transition zones in RAC), and materials properties. Specifically, these properties of RAC include fresh concrete workability, physical and chemical properties (i.e. density, carbonation depth, and chloride ion penetration), mechanical properties (i.e. compressive, flexural, and splitting tensile strength as well as elastic modulus), and long-term performance (i.e. freezing-thawing resistance, alkali-silica reaction resistance, creep, and dry shrinkage). On top of that, methods for improving RAC mechanical properties and long-term performance are summarized and categorized into three groups, i.e. (1) reduction of recycled aggregate porosity, (2) reduction of old mortar layer on recycled aggregate surface, and (3) property improvement without recycled aggregate modification (i.e. different concrete mixing design and addition of fibre reinforcement). Next, current regression-based models and artificial intelligence models on the prediction of compressive strength, modulus, and compressive stress-strain curves of RAC are reviewed and the ir limitations of those models are discussed. Furthermore, the state-of-the-art RAC applications are presented. Additionally, challenges of RAC application are reviewed taking China as an example. The link between material from CDW and EU green policy are discussed by analysing the previous research projects funded by European Commission. Finally, future perspectives of RAC research focus are discussed, i.e. development of “green” treatment methods on recycled aggregate s , further direction on nanoparticle application in RAC, and the establishment of database for RAC strength prediction.

Managing supply chains for sustainable operations in the era of industry 4.0 and circular economy: Analysis of barriers

Abstract: Organizations are struggling to leverage emerging opportunities for maintaining sustainability in the global markets due to many barriers in the era of Industry 4.0 and circular economy. The main aim of this study is to analyze these barriers to improve the sustainability of a supply chain. Our study identifies the major criteria for sustainable operations and barriers that need to be overcome to achieve the objectives of sustainability through literature review and experts’ opinions. An integrated approach comprising Analytic Hierarchy Process (AHP) and Elimination and Choice Expressing Reality (ELECTRE) is used to analyze these barriers and ensure the sustainable supply chain operations. Resource circularity, increasing profits from green products, and designing processes for resource and energy efficiency have been found to be as major sustainability criteria. There are many barriers to the implementation of Industry 4.0. These barriers include but are not limited to, a lack of a skilled workforce that understands Industry 4.0, ineffective legislation and controls, ineffective performance framework, and short-term corporate goals. The study finds that ineffective strategies for the integration of industry 4.0 with sustainability measures, combined with a lack of funds for industry 4.0 initiatives, are just two of the major barriers. The findings of the study will help organizations to develop an effective and integrated strategic approach that will foster sustainable operations through the utilization of improved knowledge of Industry 4.0 and the circular economy.

Dynamic and causality interrelationships from municipal solid waste recycling to economic growth, carbon emissions and energy efficiency using a novel bootstrapping autoregressive distributed lag

Abstract: This study contributes to estimate the municipal solid waste (MSW) recycling effect on environmental quality and economic growth in the United States. Few studies have been given to macro-level aggregate analysis through national scale MSW recycling, environmental, and economic indicators. This study employs bootstrapping autoregressive distributed lag modeling for investigating the cointegration relationship among MSW recycling, economic growth, carbon emissions, and energy efficiency utilized quarterly data from 1990 to 2017. The result implies that a one percent increase in MSW recycling contributes to economic growth and reduce carbon emissions by 0.317% (0.157%) and 0.209% (0.087%) in the long-run (short-run). Similarly, a one percent improvement in energy efficiency stimulates economic growth by 0.489% (0.281%) and mitigates carbon emissions by 0.285% (0.197%) in the long-run (short-run). A higher per capita income and population growth caused higher emissions by 0.197% and 0.401% in the long-run. The overall results reveal stronger impacts in the long-run than the short-run with significant convergence towards long-run equilibrium, suggesting a prominent long-run transmission of economic and environmental fallouts. This study confirms a uni-directional causality from MSW recycling to economic growth, carbon emissions, and energy efficiency. These outcomes signify that any policy intervention related to MSW recycling produces significant changes in the level of economic growth and carbon emissions. The finding provides valuable insight for policymakers to counteract carbon emissions through recyclable waste management that simultaneously create significant economic value.

Recycling of landfill wastes (tyres, plastics and glass) in construction - A review on global waste generation, performance, application and future opportunities

Abstract: The world is moving towards a circular economy that focuses on reducing wastes and keeping materials in use for the longest time possible. This paper critically reviewed three of the largest volume of landfill waste materials (tyres, plastics and glass) that are becoming a major concern for many countries. At present, crumb rubbers (from tyres) and glass sands (from crushed waste glass) are being used in concrete and road constructions while plastics are often used in manufacturing civil structures. However, only 10% tyres, 19.5% plastics and 21% glass are currently recycled globally. The massive volume of remaining unused wastes goes to landfill creating environmental problems. Therefore, finding new strategies of utilising these landfill wastes is vital. The global and country specific production, recycling and landfilling rates of these waste are summarised to understand the present situation of global waste crisis. Future strategies for improved waste management, potential investment and research directions are highlighted. New options for recycling wastes tyres, plastics and glass in construction are also presented to provide practical and economical solutions to extract maximum value and ensure their continued use in a closed loop system.

Digital technologies catalyzing business model innovation for circular economy—Multiple case study

Abstract: Digital technologies have been increasingly argued to enable circular economy business models. However, the extant research is based on conceptual and review studies, leading to a lack of understanding of how digital technologies enable individual firms in real-life settings to improve their resource flows and value creation and capture and thereby enable business model innovation to emerge. In this study, we conducted a multiple case study with interviews and document data from four Northern Europe-based forerunner firms with circular economy business models enabled by digital technologies, providing two key contributions to the extant literature. First, we generate an empirical evidence -based synthesis of improvements of resource flows and value creation and capture in firms’ businesses across industries, highlighting the critical role of knowledge generation. Second, we develop a model of four key types of business model innovation for circular economy catalyzed by digital technologies, varying on incremental and radical improvement to both the resource flows and value creation and capture, providing theoretical insights to both business model innovation and digital technologies in circular economy. For managers, we suggest suitable digital technologies for the key types, highlighting the importance of radical business model innovation catalyzed by data integration and analysis technologies.

The impact of low-carbon city pilot policy on the total factor productivity of listed enterprises in China

Abstract: In recent years, the low-carbon city pilot policy has been important work in China It aims to control the city's greenhouse gas emissions, find a "win-win" path of low-carbon and economy and drive the innovation and development of cities through low-carbon goals In this context, we consider the low-carbon city pilot policy as the starting point Based on the data of A-share listed companies in Shanghai and Shenzhen from 2005 to 2015 in 285 prefecture-level cities, the OP and LP methods are used to calculate total factor productivity (TFP) In this paper, using PSM-DID and other methods, we empirically test whether and how the low-carbon city pilot policy affects enterprise TFP The results indicate that the construction of low-carbon cities significantly promotes an increase in the TFP of local enterprises In addition, improving technological innovation and optimizing the efficiency of resource allocation are two important transmission mechanisms The above conclusions are robust to a series of tests Therefore, the implementation of a low-carbon city pilot policy can help achieve the "win-win" goal of emission reduction and high-quality enterprise development This study provides strong support for further expanding the scope of low-carbon city pilot policy projects and the scientific implementation of climate change policies, and it provides beneficial policy enlightenment for the scientific implementation of urban emission reduction control to win the battle against climate change

Environmental performance comparison of bioplastics and petrochemical plastics: A review of life cycle assessment (LCA) methodological decisions

Abstract: There is currently a shift from petrochemical to bio-based plastics (bioplastics). The application of comprehensive and appropriately designed LCA studies are imperative to provide clear evidence on the comparative sustainability of bioplastics. This review explores the growing collective of LCA studies that compare the environmental footprints of specific bioplastics against those of petrochemical plastics. 44 relevant studies published between 2011 and 2020 were reviewed to explore important methodological choices regarding impact category selection, inventory completeness (e.g. inclusion of additives), boundary definition (e.g. inclusion of land-use change impacts), representation of biogenic carbon, choice of end-of-life scenarios, type of LCA, and the application of uncertainty analysis. Good practice examples facilitated identification of common gaps and weaknesses in LCA studies applied to benchmark bioplastics against petrochemical plastics. Many studies did not provide a holistic picture of the environmental impacts of bioplastic products, thereby potentially supporting misleading conclusions. For comprehensive evaluation of bioplastic sustainability, we recommend that LCA practitioners: embrace more detailed and transparent reporting of LCI data within plastic LCA studies; adopt a comprehensive impact assessment methodology pertaining to all priority environmental challenges; incorporate multiple plastic use cycles within functional unit definition and system boundaries where plastics can be recycled; include additives in life cycle inventories unless there is clear evidence that they contribute long-term carbon sinks; account for (indirect) land-use change arising from feedstock cultivation; prospectively consider realistic scenarios of deployment and end-of-life, preferably within a consequential LCA framework.

A qualitative assessment of lithium ion battery recycling processes

Abstract: With the widespread adoption of e-mobility, there are high numbers of lithium Ion batteries (LIB) entering the waste stream. It is imperative that disposal and recycling strategies are developed and implemented. There is an urgent need for safe, environmentally friendly and economically affordable disposal routes for End of Life (EoL) LIBs. This study has looked at 44 commercial recyclers and assessed their recycling and reclamation processes. A novel qualitative assessment matrix termed “Strategic materials Weighting And Value Evaluation" (SWAVE) is proposed and used to compare the strategic importance and value of various materials in EoL LIBs. The sustainability and quality of recycled material are assessed by comparing the final form or composition after the recycling processes, the industrial processes and the industry type (primary sector, manufacturer or recycler). SWAVE is applied to each company, producing a score out of 20, with a higher number indicating that more materials can be recycled. The separation processes and resources from six of the prominent recycling companies are discussed further. The majority of recyclers use one or more of mechanical treatment, pyrometallurgy, or hydrometallurgy, concentrating upon high value metal extraction rather than closed-loop recycling of the metals or component materials, highlighting an environmental and technological gap. To improve the current circular economy of batteries reuse and repurposing of materials (closed-loop recycling), instead of purely recycling or recovery of metals should be considered for further development. Further studies of environmental trade-offs from recycling or recovering one material in preference to another is required.

Copper and critical metals production from porphyry ores and E-wastes: A review of resource availability, processing/recycling challenges, socio-environmental aspects, and sustainability issues

Abstract: Porphyry ores and E-wastes/WEEE are two of the most important copper-bearing materials on the planet. Over 60% of world copper output comes from porphyry copper ores while E-waste(s) is globally the largest copper-bearing waste category since the 1980s. They also contain critical elements for low-carbon technologies essential in the clean energy transition's success. In this review, a critical analysis of ore distribution/processing, metal extraction, E-waste generation and E-waste recycling is presented, focusing on identifying challenges and how to address them with emerging technologies and sustainable socio-environmental strategies. Access to ore deposits is a major hurdle for mine development while the absence of a consistent E-waste classification and legislation, including poor collection rates, remains serious problems in E-waste recycling. As lower grade porphyry ores are exploited, difficulties in processing/extraction due to mineralogical complexities, very fine particles and the generation of “dirty” concentrates will become more prevalent. For E-wastes recycling, current trends are to develop smaller, more mobile, and eco-friendly hydrometallurgical alternatives to pyrometallurgy that can handle localised compositional and feed variabilities. Finally, more sustainable mine waste management strategies, including better LCIA tools with spatial and temporal dimensions, are needed to limit socio-environmental impacts of resources exploitation and maintain the sector's SLO.

How technological innovation impacts urban green economy efficiency in emerging economies: A case study of 278 Chinese cities

Abstract: Clarifying the relationship and mechanism between technological innovation and the green economy efficiency (GEE) will improve the growth of the urban green economy for emerging economies. In the case of 278 Chinese prefecture cities, the data envelopment analysis game cross-efficiency model was used to measure the GEE between 2003 and 2017. In addition, the spatial econometric model was employed to explore the relationship and the transmission mechanism between technological innovation and the GEE from the perspectives of natural resources and urbanization. The heterogeneity of urban development was also brought into the analysis. The main results are as follows. (1) The GEE had positive spatial correlations. (2) Nationally, the intensive effect of technological innovation was significant and could considerably improve the GEE. (3) Due to the heterogeneity of urban development, there were large differences in the relationships and mechanisms between technological innovation and the GEE. Accordingly, that “unilateral” green economy construction efforts may not achieve ideal results. Therefore, neighboring cities should actively create green economy city cluster to achieve regionally common development. The eastern local governments could accelerate the transformation of the urban economy and promote the upgrading of green standards in industry through technological innovation. It is important for the central city governments to guide researchers to change the focus of their research, whereas the western region relies on attracting researchers to realize green economic development. Our results not only contribute to advancing the existing literature, but also are of considerable interest to policy makers and urban planners in emerging economies.

Use of steel slag as sustainable construction materials: A review of accelerated carbonation treatment

Abstract: Steel slag is a by-product discharged from the steelmaking process, which is characterized by abundant free calcium/magnesium oxide, low cementitious properties, and high contents of heavy metals. The disposal of steel slag at landfills not only wastes valuable resources but also causes serious pollutions to the environment. However, the direct use of untreated steel slag poses a great risk to the mechanical properties and durability of the steel slag-derived composites. In recent years, research on the use of steel slag as eco-friendly construction materials has experienced an unprecedented advance, particularly with the discovery that accelerated carbonation is conducive to improving the inferior properties. This review summarizes the various types of steel slags based on chemical/mineral compositions and the related physic-chemical properties. It also highlights recent progress on the use of accelerated carbonation to improve the quality of steel slag in the context of a wide range of influencing factors, such as temperature, reaction time, CO2 concentration and pressure, moisture, particle size and gradation of steel slag, and additives. A major challenge is to dissect the interconnectedness between the influencing factors and their relative contributions to the property improvement of steel slag. After that, we introduce the practical applications of carbonated steel slag with improved properties. Finally, we provide new insights into the mechanisms and challenges of using accelerated carbonation as a treatment of steel slag for future research and industrial applications.

Industrial agglomeration, technological innovation and carbon productivity: Evidence from China

Abstract: Industrial agglomeration and technological innovation are considered significant mechanisms to affect carbon productivity. This paper investigates the relationship between heterogeneous industrial agglomeration, technological innovation and carbon productivity using the Dynamic Spatial Durbin Model based on panel data of the industrial sector of 30 Chinese provinces from 1998 to 2017. The results show that: overall, there is an inverted “U” relationship between industrial agglomeration and carbon productivity, and technological innovation plays an important role in determining the “inflection point”. The impact of technological innovation upon industrial agglomeration as well as on carbon productivity is different under different types of industrial agglomerations and different regions. Compared with the general technological innovation, low-carbon technological innovation has a larger impact on carbon productivity, whilst its potential to improve the situation has not been fully realized. Carbon productivity has significant path-dependent characteristics and, together with industrial agglomeration and technological innovation, they all have significant spatial spillover effects. Both theoretical and practical significance have drawn from this paper, in particular for China, to optimize the efficiency through spatial reforming of industrial agglomerations to maintain economic growth and increase the total carbon productivity from the long run.

Step towards the sustainable toxic dyes removal and recycling from aqueous solution- A comprehensive review

Abstract: The synthetic dyes and chemicals used in industries produce a tremendous amount of contaminated water. Most of the poisonous dyes generated from different textileindustries are released directly to the environment. As a consequence, the discharge of wastewater from a large number of textile industries without prior treatment leads to significant negative impacts on human health. The utilization of efficient and inexpensive nano-adsorbent may reduce the adverse impacts of dyes in the environment due to their unique properties. To alleviate these issues, attention has been paid to develop efficient adsorbents for the removal of undesirable species from wastewater. Efficient and selective removal of dyes is gaining importance to reduce the environmental problems. Comparison of degradation efficiencyfor different catalysts could be a holistic approach that should be taken under consideration owing to search a suitable adsorbent. An in-depth evaluation of extensive variety of advanced adsorbents reported in literature for dye degradation has been furnished. In addition to underscoring the physico-chemical properties of different adsorbents, this review also endorses the mechanisms and efficiencies within the adsorption process. The challenges of dye degradation process are focused to reduce the adverse impacts of dyes in the environment. The critical assessment of next generation adsorbents would presumably be promoted the clean and affordable water purification process in practice.

Deployment of electric vehicles in China to meet the carbon neutral target by 2060: Provincial disparities in energy systems, CO2 emissions, and cost effectiveness

Abstract: Switching to electricity in the ground transport sector is considered a promising way to achieve the energy transition and CO2 emission reductions required to meet China's carbon neutral target by 2060. In this study, a transport energy model containing an elaborate transport demand model and a technology bottom-up model for detailed behavioral and technological representations was developed to investigate how electric vehicles (EVs) will penetrate the markets in the long-term and what impacts on energy consumption and emissions would emerge following EV adoption in China at the provincial level. A set of scenarios was created based on different policy interventions for the promotion of electric mobility. The results showed that subsidies for EV adoption would significantly boost the market share and foster a rapid transition away from fossil fuels, while the business-as-usual scenario would only generate a moderate influence on EV penetration. The regional differences in the emission reduction potential due to EV subsidies across the 31 provinces indicated that policy instruments for EV promotion would have significant positive effects in the developed provinces in both the capital metropolitan area and southeastern China. An economic cost analysis revealed a relatively low economic feasibility in northeastern and northwestern regions where the emission reduction potential is also lower than the national average, implying that the developing provinces in northeastern and northwestern China require greater financial assistance and the establishment of supportive policies for EV promotion.

Recent progress in recycling carbon fibre reinforced composites and dry carbon fibre wastes

Abstract: Carbon fibre reinforced composites (CFRC) continue to play a key role in the growth and development of many weight sensitive industries. However, their proliferation has raised increasing concerns regarding the required practices and strategies to deal with these expensive engineered structures at the end of their life cycle. This has brought into focus the need to develop more sustainable and efficient recycling solutions for these products. Similarly, the necessity of managing dry carbon fibre scraps generated during the manufacturing process of CFRC has attracted more attention in recent years. This review article provides an overview on recent advances in recycling CFRC as well as processing dry carbon fibre scraps. Influential parameters, advantages, drawbacks, and possible environmental impacts of the main technologies of processing CFRC waste including mechanical, thermal (pyrolysis and fluidised bed), and chemical (solvolysis and low temperature chemical processing) will be evaluated. Their potential effects on mechanical characteristics and surface chemistry of fibres are assessed. Moreover, recent processing methods of dry and semi-finished carbon fibre scrap are also reviewed. Specific attention is paid to the recent developments in producing hybrid yarns and nonwovens made of waste carbon fibre. The methodologies developed in this area, their processing conditions, as well as other important findings are discussed. This review paper provides a valuable platform for researchers and decision makers working in the field of carbon fibre by providing a clearer picture on the options available to recycle CFRC, and the methods of developing value-added products using waste carbon fibre.

Industry 4.0 for sustainable manufacturing: Opportunities at the product, process, and system levels

Abstract: Limited resource availability and the negative environmental and societal impacts of traditional manufacturing have motivated the need for sustainable manufacturing. Product, process, and system integration, considering the interdependent sustainability impacts, is vital for sustainable manufacturing. Industry 4.0 and its constituent technologies offer significant potential to advance manufacturing competitiveness. Can the implementation of more sustainable manufacturing practices be facilitated or enhanced by using Industry 4.0 technologies? Current literature fall short in comprehensively addressing this question. Most treat either Industry 4.0 as a single technology, or sustainable manufacturing very broadly, without an in-depth consideration of the impacts on products, processes, and systems. To address this gap, this paper presents a comparative analysis examining individual Industry 4.0 technologies and their potential impact on sustainable manufacturing. A framework based on product, process, and systems sustainability metrics clusters is applied to examine these impacts. The findings reveal that literature is still limited in identifying opportunities for sustainability improvement at the different levels using Industry 4.0 technologies; the impact on many criteria related to product, process, or system level sustainability due to Industry 4.0 technologies have not yet been examined. The comparative analysis, and other literature, are used to provide further directions for future research and opportunities on leveraging Industry 4.0 technologies for more sustainable manufacturing. The implications for industry by way of offering a framework to identify potential solutions to enhance sustainable manufacturing performance using Industry 4.0 technologies are also discussed.

Implementing the circular economy paradigm in the agri-food supply chain: The role of food waste prevention technologies

Abstract: Food systems are plagued by the grand sustainability challenge of food waste, which represents a urging issue from economic, environmental and social point of view. dThe Circular Economy paradigm can open up different actions which are framed within the so-called Food Waste Hierarchy (FWH). In these regards, scholars recommend to leverage on those practices that are able to prevent the generation of surplus food, preserving a higher share of the sustainable value. For these pre-harvest and post-harvest practices that go under the name of prevention or reuse strategies in different FWH, technology plays a crucial role. Through a set of 34 semi-structured interviews with technology providers as well as with companies in the agri-food supply chain, the present work investigates extensively the range of the available technologies and the detailed objectives of such technologies for food loss and waste prevention (i.e., forecasting, monitoring, grouping, shelf life extension, product quality and value upgrading). Moreover, different forms of collaboration enable to reach these objectives in different ways. Collaboration with technology providers can be based on continuous technical assistance and consulting for data elaboration and data analysis as well as on full data sharing and co-design, allowing to achieve a different impact on food loss and waste prevention. Finally, our study reveals that the adoption of different technological options can represent the engine to establish vertical collaborations between the adopter of the technology and another stage in the agri-food supply chain, in order to fight food waste and loss with a coordinated supply chain effort.

Recycling waste classification using optimized convolutional neural network

Abstract: An automatic classification robot based on effective image recognition could help reduce huge labors of recycling tasks. Convolutional neural network (CNN) model, such as DenseNet121, improved the traditional image recognition technology and was the currently dominant approach to image recognition. A famous benchmark dataset, i.e., TrashNet, comprised of a total of 2527 images with six different waste categories was used to evaluate the CNNs’ performance. To enhance the accuracy of waste classification driven by CNNs, the data augmentation method could be adopted to do so, but fine-tuning optimally hyper-parameters of CNN's fully-connected-layer was never used. Therefore, besides data augmentation, this study aims to utilize a genetic algorithm (GA) to optimize the fully-connected-layer of DenseNet121 for improving the classification accuracy of DenseNet121 on TrashNet and proposes the optimized DenseNet121. The results show that the optimized DenseNet121 achieved the highest accuracy of 99.6%, when compared with other studies’ CNNs. The data augmentation could perform higher efficiency on accuracy improvement of image classification than optimizing fully-connected-layer of DenseNet121 for TrashNet. To replace the function of the original classifier of DenseNet121 with fully-connected-layer can improve DenseNet121’s performance. The optimized DenseNet121 further improved the accuracy and demonstrated the efficiency of using GA to optimize the neuron number and the dropout rate of fully-connected-layer. Gradient-weighted class activation mapping helped highlight the coarse features of the waste image and provide additional insight into the explainability of optimized DenseNet121.

Covid-19 effects on municipal solid waste management: What can effectively be done in the Brazilian scenario?

Abstract: The Covid-19 pandemic will leave a lasting impact on nearly every aspect of life in society and has also raised concerns on the contamination risks associated with waste management. This study presents a review on the main recommendations related to the management of municipal solid wastes during the pandemic. The recommendations were classified according to the target audience, and their applicability to the Brazilian reality is discussed. Results show that most analyzed recommendations are related to hygiene routines, use of personal protective equipment, and proper segregation, packing and final destination of potentially contaminated wastes. Brazilian organizations show a special concern about the exposure risks of waste pickers, advising for the temporary suspension of manual waste collection and sorting, hygiene protocols, social distancing and quarantine of recyclable materials. Overall, the recommendations are highly dependent on awareness and engagement of citizens and on planning and support of municipalities, which must invest in information campaigns and provide alternatives for the infectious waste produced in households. Furthermore, this study points out that the recommendations were issued in an emergency scenario, but as the pandemic is expected to last for an extended period of time, they must be revised as local contexts change, seeking to maintain and extend citizens engagement in selective collection and even in actions towards waste reduction.

Critical success and risk factors for circular business models valorising agricultural waste and by-products

Abstract: For a transition from a linear, ‘take-make-dispose’ economy to a sustainable usage of all constituents of renewable resources in cascading and circular pathways, new business models valorising streams that are currently considered as waste are needed. The aim of this article is to understand critical success and risk factors of eco-innovative business models that contribute to a circular economy via agricultural unavoidable waste or by-products valorisation. 39 cases were studied focusing on agricultural side stream conversion into valuable products. Semi-structured interviews were performed and secondary data collected. Cases were analysed according to types of initiatives, main objectives, resources and valorisation pathways, as well as external and internal factors that have influenced the businesses over time. Following success and risk factor categories are identified: (1) technical and logistic, (2) economic, financial and marketing, (3) organisational and spatial, (4) institutional and legal, (5) environmental, social and cultural. Herein, specific factors for the agricultural sector are innovative conversion technologies, flexible in and out logistics, joint investments in R&D, price competitiveness for bio-based products, partnerships with research organisations, space availability, subsidies, agricultural waste management regulations, local stakeholder involvement and acceptance of bio-based production processes. Insights from this study can help farmers and agribusiness managers by defining and adapting their strategies within their local contexts. They also show that for shifting from linear agro-food chains to a circular system, individual businesses need to evolve towards more dynamic and integrated business models, in which the macro-environment sets the boundary conditions for successful operations.

Lightweight foamed concrete as a promising avenue for incorporating waste materials: A review

Abstract: Several million tons of different types of wastes are generated every year globally and this is expected to increase in the future. Most of these wastes are dumped via landfilling or incineration which creates environmental concerns. One of the possible methods of utilizing these wastes is by incorporating them as alternatives to common concrete constituents. In this regard, foamed concrete could provide an excellent medium for incorporating these wastes in a large volume primarily due to low strength requirement of foamed concrete. A significant number of research is carried out to explore the idea of integrating waste materials in pre-foamed concrete. However, the limited knowledge available to recognize the utilization of these waste and the influence on foamed concrete limits the adoption of the concept and further development. Hence, this paper compiles and reviews the usage of various types of wastes such as industrial, agricultural, quarry, and construction industry wastes as a potential replacement for cement and fine aggregate in foamed concrete. Due to the unique composition and the resulting chemical and physical properties, as well as the nature of replacement (either as cement or fine aggregate replacement), each type of waste contributes differently to the performance of foamed concrete. Generally, a non-load bearing foamed concrete with low thermal conductivity, low density, and adequate compressive strength can be produced by incorporating the waste materials. This paper also describes the advantages of incorporating waste materials in foamed concrete compared to conventional concrete and proposes the further development of the concept for future application of a more sustainable and eco-friendly foamed concrete.

Toward Sustainable Reuse of Retired Lithium-ion Batteries from Electric Vehicles

Abstract: As attractive energy storage technologies, Lithium-ion batteries (LIBs) have been widely integrated in renewable resources and electric vehicles (EVs) due to their advantages such as high energy/power densities, high reliability and long service time. Although EVs basically do not produce pollution, the end-of-life (EOL) issues of LIBs cannot be ignored due to their potential economic benefits and environmental risks. Current methods for the retired batteries mainly include disposal, recycling and reuse. EV LIBs can be reused in a variety of applications with less demanding. Compared with recycling and disposal, reuse process can obtain better economic and environmental benefits. Many second life EV LIBs projects have been undertaken and demonstrated the great potential of reuse. However, the reuse should consider economic, environmental, technical, and various market perspectives. Technical challenges that must be faced include safety issues, assessment methods, screening and restructuring technologies, and comprehensive management during the reuse process. Economic feasibility issues, comprehensive supply chains, and the lack of relevant regulations also hinder large-scale development of reuse. It is foreseeable that improvements including standardization, big data and cloud-based technologies are desperately needed to maximize the industrialization of reuse and recycling.

Major metals demand, supply, and environmental impacts to 2100: A critical review

Abstract: Sustainable metal supply requires well-coordinated strategy and policy packages based on a sound scientific understanding of anticipated long-term demand, supply, and associated environmental implications. Such information, however, is highly fragmented among various case studies. Accordingly, this extensive review explores the projected long-term status of six major metals—iron, aluminum, copper, zinc, lead, and nickel—with around 200 data points for global demand through 2030, 2050 and 2100. Our findings showed that global demand for these major metals is likely to increase continuously over the 21st century, increasing approximately 2–6-fold depending on the metal. Although the extraction and processing required to meet this increase in demand must be environmentally sustainable, the existing extraction and processing scenarios have few explicit linkages to the Earth's carrying capacity. We further found that strategy choices are heavily biased towards end-of-life phase analyses, specifically that of end-of-life recycling. Consequently, a full range of opportunities across entire life cycles is being overlooked, including advances in product design, manufacturing and in-use phases. Importantly, despite the emergence of numerous scenarios, few provide science-based targets for major metal flows, stock, circularity, and efficiency. These knowledge gaps need to be addressed urgently in order to ensure that future research directly supports science-based decision and policy making.

Circular economy implementation in the agricultural sector: Definition, strategies and indicators

Abstract: In the current context of resource scarcity, global climate change, environmental degradation, and increasing food demand, the circular economy (CE) represents a promising strategy for supporting sustainable, restorative, and regenerative agriculture. A review of the literature on CE confirms the initial hypothesis that the theoretical CE framework has not yet been adapted to the field of agriculture. Therefore, this paper overcomes this gap in two ways: i) by adjusting the general CE framework to the agricultural sector's specificities, and ii) by analyzing the scope of the indicators available for measuring agricultural production systems’ circularity performance in supporting decision-making processes. Accordingly, the different elements in the theoretical CE framework are adapted to agricultural production systems. One major contribution of this paper is the definition of CE applied to agriculture. In addition, the principles of CE are adapted to the field, and CE strategies for agricultural activity are defined. Forty-one circularity indicators for application in agricultural systems were also comprehensively assessed to determine their strengths and weaknesses. Building on the key findings, future research paths and changes at the institutional and normative levels are proposed to facilitate CE implementation in agricultural production systems. For example, internationally recognized standards and adequate units of measurement must be defined, to develop meaningful studies and determine agricultural activities’ circularity performance.

Concerns and strategies for wastewater treatment during COVID-19 pandemic to stop plausible transmission

Abstract: Along with outbreak of the pandemic COVID-19 caused by SARS-CoV-2, the problem of biomedical wastewater disposal has caused widespread public concern, as reportedly the presence is confirmed in wastewater. Keeping in mind (i) available evidence indicating need to better understand potential of wastewater mediated transmission and (ii) knowledge gaps in its occurrence, viability, persistence, and inactivation in wastewater, in this present work, we wanted to re-emphasize some strategies for management of SARS-CoV-2 contaminated wastewater to minimise any possible secondary transmission to human and environment. The immediate challenges to consider while considering wastewater management are uncertainty about this new biothreat, relying on prediction based treatments options, significant population being the latent asymptomatic carrier increased risk of passing out of the virus to sewage network, inadequacy of wastewater treatment facility particularly in populated developing countries and increased generation of wastewater due to increased cleanliness concern. In absence of regulated central treatment facility, installation of decentralized wastewater treatment units with single or multiple disinfection barriers in medical units, quarantine centre, isolation wards, testing facilities seems to be urgent for minimizing any potential risk of wastewater transmission. Employing some emerging disinfectants (peracetic acid, performic acid, sodium dichloro isocyanurate, chloramines, chlorine dioxide, benzalconium chloride) shows prospects in terms of virucidal properties. However, there is need of additional research on coronaviruses specific disinfection data generation, regular monitoring of performance considering all factors influencing virus survival, performance evaluation in actual water treatment, need of augmenting disinfection dosages, environmental considerations to select the most appropriate disinfection technology.

Comprehensive review on metallurgical recycling and cleaning of copper slag

Abstract: Copper slag, generated mainly during copper smelting, and classified as a potentially harmful waste, is an important secondary resource containing not only valuable metals, such as Cu, Fe, Zn, Co and Ni, in abundant quantities, but also hazardous elements, such as Pb and As. Hence, in response of its potential economic performances and environmental benefits, copper slag needs to be subjected to further metallurgical recycling and cleaning instead of being dumped or abandoned without treatment. Here, a critical review of the generation mechanism, and chemical and physical characteristics of copper slag is provided. Details of the mainstream and recently developed routes for metallurgical recycling and further cleaning of copper slag are also summarised, such as flotation, leaching, and reduction roasting followed by magnetic separation, smelting reduction, and molten modification followed by physical separation. The technical challenges and developmental bottlenecks of the metallurgical processes are pointed out, which indicate that the improved processes characterised by high recycling efficiency, low energy consumption, and low secondary environmental pollution continue to be the focus of research and development in sustainable waste utilization of copper slag.

Application of waste tire rubber and recycled aggregates in concrete products: A new compression casting approach

Abstract: The inferior performance of eco-friendly concrete owing to the addition of waste materials is a big hurdle in its practical adaptation. This study focuses on developing eco-friendly and green concrete, having performance similar to normal aggregate concrete (NAC). For this purpose, two waste products, including recycled aggregates (RA) and waste tire chipped rubber (CR), were used during the study. Furthermore, green concrete was also manufactured using RA treated through techniques such as lime immersion with carbonation and acetic acid immersion with mechanical rubbing. To achieve the strength of green concrete similar to NAC, an innovative concrete casting approach was followed. Green concrete specimens were cast and then compressed in the fresh state using specially designed molds. Results show that the compressive strength of recycled aggregate concrete (RAC) incorporating 20% CR in replacement of coarse aggregates is noticed 49% lower than NAC. However, the compressive strength and elastic modulus of compressed RAC and treated RAC incorporating 10-20% of CR in replacement of coarse aggregates are quite close to traditional concrete specimens without CR. No such method is available in the current literature through which green concrete incorporating RA and CR can achieve properties similar to NAC. Furthermore, the cost comparison and cement strength contribution index calculated in this study also show the industrial application potential of the new casting approach. Therefore, the developed concrete casting approach promotes the efficient utilization of RA and CR in the production of precast concrete members resulting in eco-friendly and sustainable construction.

Emergency response to the explosive growth of health care wastes during COVID-19 pandemic in Wuhan, China

Abstract: During the Coronavirus Disease 2019 (COVID-19) as a worldwide pandemic, the security management of health care wastes (HCWs) has attracted increasing concern due to their high risk. In this paper, the integrated management of HCWs in Wuhan, the first COVID-19-outbreaking city with over ten millions of people completely locking down, was collected, investigated and analyzed. During the pandemic, municipal solid wastes (MSWs) from designated hospitals, Fangcang shelter hospitals, isolation locations and residential areas (e.g. face masks) were collected and categorized as HCWs due to the high infectiousness and strong survivability of COVID-19, and accordingly the average production of HCWs per 1000 persons in Wuhan explosively increased from 3.64 kg/d to 27.32 kg/d. Segregation, collection, storage, transportation and disposal of HCWs in Wuhan were discussed and outlined. Stationary facilities, mobile facilities, co-processing facilities (Incineration plants for MSWs) and nonlocal disposal were consecutively utilized to improve the disposal capacity, from 50 tons/d to 280.1 tons/d. Results indicated that stationary and co-processing facilities were preferential for HCWs disposal, while mobile facilities and nonlocal disposal acted as supplementary approaches. Overall, the improved system of HCWs management could meet the challenge of the explosive growth of HCWs production during COVID-19 pandemic in Wuhan. Furthermore, these practices could provide a reference for other densely populated metropolises.

From waste to sustainable industry: How can agro-industrial wastes help in the development of new products?

Abstract: Demand for food production has been promoting an increase in the generation of agro-industrial wastes. Although in the past these wastes were mainly seen as a big issue, in the current scenario they are seen as the key strategy for the development of sustainable industrial processes. In this context, several new environmentally friendly technologies such as supercritical fluid extraction (SFE), microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) have been studied and applied to obtain products with high added value in order to supply the chemical, pharmaceutical and food industries. Similarly, the energy generation from biomass and production of new biomaterials such as bionanofilms, bioaerogels, hydrogels and nanocomposites have been intensely studied in order to cross the barriers of the laboratory scale. Therefore, this review aims to update the scientific community, industries, governments and society on the sustainable applications, latest advances and trends in the valorization of agro-industrial wastes for new product development, highlighting the new possibilities for the progress of sustainable production.