Showing papers in "Resources Conservation and Recycling in 2022"
TL;DR: In this paper, the authors explored the concept of carbon neutrality and made a comparative analysis of the gap between China, the European Union, and the United States vis-a-vis carbon neutrality based on international data.
Abstract: In response to climate change, the Chinese government has set a clear goal to reach its carbon peak by 2030 and achieve carbon neutrality by 2060, endeavoring to gradually realize net-zero carbon dioxide (CO2) emissions. This paper explores the concept of carbon neutrality and makes a comparative analysis of the gap between China, the European Union, and the United States vis-a-vis carbon neutrality based on international data. The main challenges China faces in its progress toward carbon neutrality are the following: first, China's energy consumption and CO2 emissions continue to increase, while its carbon peak has not yet been reached; second, carbon emission reduction in China is an arduous process, as the transition period allowed for the country to transition from its carbon peak to carbon neutrality is shorter than that of developed countries; third, China remains reliant on high-carbon fossil energy, with high energy consumption and low energy utilization efficiency; fourth, China's low level of economic development, compared with those of the EU, the US, or other developed countries, makes it relatively weak to withstand economic risks; and fifth, China's low-carbon and zero-carbon technologies are not mature. Therefore, this paper posits a three-stage/four-step strategy as well as seven specific suggestions that could benefit China's progress toward carbon neutrality.
399 citations
TL;DR: Wang et al. as discussed by the authors analyzed China's challenges toward carbon neutrality by 2060 and proposed a three-stage/four-step strategy for China to achieve CN, and also presented seven suggestions to foster China's green transition.
Abstract: • This paper analyzes China's challenges toward carbon neutrality (CN) by 2060. • Currently, up to 85% of China's energy consumption relies on fossil fuels. • China's zero-carbon technologies and economy are not yet sufficient for CN. • Thus, we propose a three-stage/four-step strategy for China to achieve CN. • This paper also presents seven suggestions to foster China's green transition. In response to climate change, the Chinese government has set a clear goal to reach its carbon peak by 2030 and achieve carbon neutrality by 2060, endeavoring to gradually realize net-zero carbon dioxide (CO 2 ) emissions. This paper explores the concept of carbon neutrality and makes a comparative analysis of the gap between China, the European Union, and the United States vis-à-vis carbon neutrality based on international data. The main challenges China faces in its progress toward carbon neutrality are the following: first, China's energy consumption and CO 2 emissions continue to increase, while its carbon peak has not yet been reached; second, carbon emission reduction in China is an arduous process, as the transition period allowed for the country to transition from its carbon peak to carbon neutrality is shorter than that of developed countries; third, China remains reliant on high-carbon fossil energy, with high energy consumption and low energy utilization efficiency; fourth, China's low level of economic development , compared with those of the EU, the US, or other developed countries, makes it relatively weak to withstand economic risks; and fifth, China's low-carbon and zero-carbon technologies are not mature. Therefore, this paper posits a three-stage/four-step strategy as well as seven specific suggestions that could benefit China's progress toward carbon neutrality.
398 citations
TL;DR: In this article, the authors explore the non-linear renewables and carbon emission efficiency nexus to optimize the energy transition path and find that RED is conductive to CEE, but there is a significant threshold effect.
Abstract: This study aims to explore the non-linear renewables and carbon emission efficiency (CEE) nexus to optimize the energy transition path. Taking 32 developed countries that have proposed carbon neutrality targets as the research objects, the super-efficiency slacks-based measure (SE-SBM) model is first used to measure their CEE from 2000 to 2018. Then, a newly developed panel threshold model with interactive fixed effects (PTIFEs) is established to comprehensively explore the non-linear impact of renewable energy development (RED) on CEE. The results show that: (1) During the sample period, there are significant differences in CEE among countries, and most countries are inefficient. (2) On the whole, RED is conductive to CEE, but there is a significant threshold effect. Specifically, this positive effect decreases with energy consumption intensity, whereas it increases with financial development, RED, and CEE. (3) The heterogeneity analysis shows that the threshold effect persists across countries with different income levels, and the direction is consistent with the entire sample. Besides, as the incomes down, the positive correlation between RED and CEE is significantly diminished. This study provides a new perspective for optimizing the energy transition path.
113 citations
TL;DR: In this paper, the authors present a consistent methodology to encourage energy transition in developing countries where the role of science is still not fully exploited under the goal of carbon neutrality, including reducing the carbon intensity of the energy supply mix, increasing energy efficiency, prioritizing environmental protection, improving actions based on science, and promoting environmental education and awareness.
Abstract: Shifting from fossil-fuel (FF) to renewable energy systems, a process known as energy transition (ET), is crucial for developing countries as the ET brings new opportunities to accomplish leapfrog development for achieving carbon neutrality. Parallel to climate change, developing countries face energy security and independence issues with extra pressures such as the Covid-19 pandemic and increasing inequality. Taking Mexico as a case, four ET scenarios under “gradual” or “rapid” narratives are developed with the Kaya Identity. Gradual Transition Scenarios (GTS) present a business-as-usual scenario with natural gas as the most significant fuel in the supply mix due to economic and social concerns. Rapid Transition Scenarios (RTS) propose a combination of FF and renewables or a full deployment of Renewable Energy Sources (RES). The results show that GTS reach 491∼ 501 Mt CO2 emissions in 2050, risking a carbon lock-in, stranded assets and economic losses. RTS reach 87∼103 Mt CO2 in 2050 with RES prioritization, energy efficiency improvements and coal phase-out. In particular, following GTS would mean failing to join global efforts to limit warming temperature to 1.5 °C. Alternatively, following RTS brings Mexico closer to achieve carbon neutrality. Several strategies are proposed, including reducing the carbon intensity of the energy supply mix, increasing energy efficiency, prioritizing environmental protection, improving actions based on science, and promoting environmental education and awareness. This paper presents a consistent methodology to encourage ET in developing countries where the role of science is still not fully exploited under the goal of carbon neutrality.
89 citations
TL;DR: In this paper, the authors review microplastic's impact on agroecosystem components and possible effects on the food chain and propose a solution to deal with the problem.
Abstract: This work reviews microplastic's impact on agroecosystem components and possible effects on the food chain. Microplastics are sized
68 citations
TL;DR: In this article, the authors empirically examined how environmental regulation affects the iron and steel industry's green development and showed that there is a U-shaped relationship between environmental regulation and energy-environmental performance.
Abstract: Environmental regulation is a critical instrument for achieving sustainable economic and social development in the context of carbon neutrality. The iron and steel industry is highly polluting and energy-consuming, posing a significant threat to China's environmental sustainability. Based on the panel of Chinese provincial-level data from 2000 to 2017, this paper empirically examines how environmental regulation affects the iron and steel industry's green development. The findings show that there is a U-shaped relationship between environmental regulation and energy-environmental performance. Low environmental regulation intensity inhibits the improvement of energy-environmental performance. But as the regulation intensity increases, it contributes to the advancement of energy-environmental performance. Environmental regulation affects the industrial energy-environment performance through technological innovation, and the relationship between environmental regulation and technological innovation presents a U-shaped relationship. There are noticeable regional differences in the impact of environmental regulation on energy-environmental performance. The findings provide new evidence to confirm the Porter Hypothesis. Finally, this paper provides policy suggestions for further energy-environmental performance improvements in China's iron and steel industry.
64 citations
TL;DR: In this article , the authors present some of the most pressing challenges of EV lithium-ion batteries across the different stages of its life cycle, including supply and demand of the battery raw materials, battery manufacturing, use and end-of-life treatments.
Abstract: Lithium-ion batteries (LIBs) play a key role in advancing electromobility. With an increasing trend in the demand for LIBs, the sustainability prospect of LIBs lifecycle faces many challenges that require proactive approaches. There are various sustainability challenges and risks across the supply and value chains of LIBs from mining, material supplies to Original Equipment Manufacturers (OEMs), users to final disposal. Risks are for example the increased raw material demands as well as some economic risks due to price increment or political instabilities in some countries within the raw material supply chain. Despite the promising research efforts on the performance metrics of LIBs and advancing the technology, the research on the various aspects of sustainability of LIBs and its life cycle are still in its infancy and require closer attention. As the editorial of the Special Issue on sustainable supply and value chains of EV batteries, this article presents some of the most pressing challenges of EV LIBs across the different stages of its life cycle. It covers issues from supply and demand of the battery raw materials, battery manufacturing, use, and end-of-life treatments. Within this context the reported findings of some 20 different research teams from across the globe, the state-of-the-art, technical or policy gaps in EV LIBs research and development are presented, as well as market instruments such as innovative business models, and governmental interventions like subsidies or regulations. We grouped the materials presented into five main themes (1) EV and LIB materials demand projections (2) EV LIBs international trade risk (3) EV battery regulation and adoption (4) EV LIBs life cycle assessment (5) and EV LIBs reverse logistics. We conclude by discussing some future research challenges such as the need for more reliable and applicable prediction models that use accurate data on EV stock and end-of-life EVs. Finally, we argue that more collaboration between academia, manufactures, OEMs and the battery recycling industry is needed to implement successful circular economy strategies to achieve environmentally friendly, flexible and cost-efficient battery supplies, use and recycling processes.
64 citations
TL;DR: In this paper , the uptake, translocation, and phytotoxicity of nanoplastics in terrestrial plants are highlighted. But, their impacts on terrestrial plants (particularly crops) are poorly understood.
Abstract: • Smaller MNPs can enter and translocate in plants more easily. • MNPs can cause damages in plants at various levels. • Phytotoxicity of MNPs is dependent on their polymer type, size, dose, and shape. • Plant responses to MNPs vary with plant species and exposure conditions. • Plant accumulation of MNPs may pose health risks through food chain. Micro(nano)plastics (MNPs) are categorized as emerging persistent pollutants that occur widely in various ecosystems. However, their impacts on terrestrial plants (particularly crops) are poorly understood. Given the persistence and widespread distribution of MNPs in the soil, it is necessary to recognize their potential impacts on terrestrial plants. This paper highlights the uptake, translocation, and phytotoxicity of MNPs in terrestrial plants. Due to their small size and high adsorption capacity, MNPs can adhere to the surfaces of seeds and roots, and thus inhibit seed germination, root elongation, and absorption of water and nutrients, and ultimately inhibit plant growth. Microplastics (MPs), especially nanoplastics (NPs), can be absorbed by roots, and be translocated to stems, leaves, and fruits. The adherence and accumulation of MNPs can induce oxidative stress, cytotoxicity, and genotoxicity in plants, leading to a series of changes in plant growth, mineral nutrition, photosynthesis, toxic accumulation, and metabolites in plants tissues. Overall, the phytotoxicity of MNPs varies dependent on their polymer type, size, dose, and shape, plant tolerance, and exposure conditions. Of particular importance is that the accumulation of MNPs and subsequent damage in plants may further affect crop productivity, and food safety and quality, causing potential health risks. Finally, knowledge gaps and future research priorities are discussed.
58 citations
TL;DR: The analysis showed that distinct technologies will develop unevenly in different parts of the world, and a gap between recycling targets and recycling technologies was identified, representing short-term opportunities for more sustainable materials, such as bio-based.
Abstract: Multi-material multilayer plastic packaging (MMPP) is widely applied in fast moving consumer goods (FMCG) combining functionalities of distinct materials. These packaging structures can enhance properties, such as resource-use efficiency and barrier performance leading to consequential benefits like a prolonged shelf-life. Nevertheless, they represent a challenge for existing recycling systems, confronting circular economy principles. This study aim was to foresight the future of recycling technologies for MMPP in the next five to ten years. Future scenarios were identified, including (1) high-performance material recycling, (2) recycling into hydrocarbons, (3) business as usual, and (4) downcycling. In-depth interviews and a feedback survey were methods used to validate the scenario matrix while defining experts' expectations towards the future. The analysis showed that distinct technologies will develop unevenly in different parts of the world. A mix of all scenarios is probable in the upcoming years, depending, essentially, on regulations and technology availability. Advanced high-performance material recycling encounters systemic bottlenecks, such as insufficient sorting technology for post-consumer waste. In contrast, chemical recycling (feedstock) is concentrating investments as a solution, requiring low input-characterization. Additionally, design for recycling trends might reduce multilayers’ complexity. A gap between recycling targets and recycling technologies was identified, representing short-term opportunities for more sustainable materials, such as bio-based.
57 citations
TL;DR: In this paper , the authors apply an evolutionary game model to a two-level green supply chain composed of green suppliers and green manufacturers in order to analyze a variety of internal and external factors that affect the behavior of both parties in the game, and thence numerically simulate the evolution and stability trend of coordinated reductions in emissions.
Abstract: The green supply chain realizes the unification of economic and environmental benefits through green manufacturing, green circulation and reverse logistics, and represents an important way to reduce emissions. The characteristics of the green supply chain network, however, can encourage some companies to exhibit “free-riding” behavior, participating without being willing to reduce emissions directly themselves. This paper applies an evolutionary game model to a two-level green supply chain composed of green suppliers and green manufacturers in order to analyze a variety of internal and external factors that affect the behavior of both parties in the game, and thence numerically simulate the evolution and stability trend of coordinated reductions in emissions. The results identify many cases of system evolution but the only stable evolution strategy is when both (1) the sum of collaborative emission reduction benefits and government subsidies is greater than the sum of collaborative emission reduction input costs and "free rider" benefits, and (2) the increased rate of unilateral emission reduction benefits is greater than the ratio of costs to original benefits. Income arising from collaborative reductions in emissions, enterprise original income, income from unilateral reductions in emissions increase ratio, government subsidy coefficient and achievement reward base can directly affect the system evolution path. The larger these value, the greater the probability of green suppliers and green manufacturers choosing collaborative reductions in emissions, and the faster the system convergence speed. Only the imposition of regulatory punishments above the threshold will affect the "free riding" behavior of enterprises and drive the upstream and downstream enterprises of the green supply chain to reduce emissions faster.
TL;DR: Wang et al. as mentioned in this paper investigated the influence of digital technology development on carbon emissions in the framework of spatial analysis, and they found that digital technologies can positively influence carbon abatement through the "spillover effect", that is, it can not only reduce local carbon emissions, but also promote carbon abattement in the surrounding cities.
Abstract: We investigate the influence of digital technology development on carbon emissions in the framework of spatial analysis. Using a sample of 283 prefecture-level cities in China, we find that digital technology development can positively influence carbon abatement through the “spillover effect”, that is, it can not only reduce local carbon emissions, but also promote carbon abatement in the surrounding cities. The “siphon effect” which could negatively affect carbon abatement in the surrounding cities is outweighed by the “spillover effect”. In addition, due to increasing information transmission costs and local protectionism, the “spillover effect” of digital technology development on carbon emissions has geographical boundaries. Although no economic boundary is found, there exists an optimal economic distance interval. Furthermore, the heterogeneous analysis shows that government intervention would reduce the carbon abatement effect of digital technology development. Compared with the eastern cities, this negative impact is more significant in the central and western cities of China. Our results suggest that governments could achieve the dual goals of digital technology development and carbon abatement by promoting regional cooperation, and reducing local protectionism and administrative divisions.
TL;DR: In this paper, the authors provide a framework that establishes a detailed relationship between the SDGs, construction waste management and the circular economy to direct future sustainable development research, policies, and innovations.
Abstract: The construction industry plays an essential role in a country's economic growth. The industry has been criticised for activities and processes that generate high volumes of waste, whilst obstructing sustainable development goal (SDGs) targets. The circular economy (CE) increases waste minimisation by keeping materials and resources in a closed loop. This concept has continued to gain positive traction as a potential solution to achieve sustainable development. The authors argue that contextualising the circular economy (CE) as part of the discourse towards implementing the United Nations (UN) SDGs Agenda 2030 is crucial for managing the increasing amounts of waste generated by the construction industry. This paper provides a framework that establishes a detailed relationship between the SDGs, construction waste management and the CE to direct future sustainable development research, policies, and innovations. The study adopted a narrative literature review methodology. Scopus and Web of Science were scoured for relevant literature published between 2015 and 2021. Initially 65 articles were identified with this number being reduced to 24 following a detailed inspection of their applicability to the study. The findings from the articles were summarized, synthesized, and incorporated into the study. A key theme that emerged was that an understanding of the SDGs-circular economy linkages in construction waste management is integral to establishing long-term innovative solutions for developing multi-sectorial measures for waste prevention, eco-design, and re-use of materials. These linkages increase competitiveness, stimulate innovation, and boost economic growth. This study proposes that all stakeholders who generate waste should apply new innovative technologies, methods and strategies leading to transdisciplinary and transformative change.
TL;DR: In this article , the authors provide a framework that establishes a detailed relationship between the SDGs, construction waste management and the circular economy to direct future sustainable development research, policies, and innovations.
Abstract: • The CE as a sustainable model can meet the needs of the construction industry. • SC is one of construction industry's approaches to achieving SD and SDGs . • The CE links the SDGs through its economic, social and environmental impacts . • Adoption of the CE in the construction industry can achieve about 10 SDGs. The construction industry plays an essential role in a country's economic growth. The industry has been criticised for activities and processes that generate high volumes of waste, whilst obstructing sustainable development goal (SDGs) targets. The circular economy (CE) increases waste minimisation by keeping materials and resources in a closed loop. This concept has continued to gain positive traction as a potential solution to achieve sustainable development. The authors argue that contextualising the circular economy (CE) as part of the discourse towards implementing the United Nations (UN) SDGs Agenda 2030 is crucial for managing the increasing amounts of waste generated by the construction industry. This paper provides a framework that establishes a detailed relationship between the SDGs, construction waste management and the CE to direct future sustainable development research, policies, and innovations. The study adopted a narrative literature review methodology. Scopus and Web of Science were scoured for relevant literature published between 2015 and 2021. Initially 65 articles were identified with this number being reduced to 24 following a detailed inspection of their applicability to the study. The findings from the articles were summarized, synthesized, and incorporated into the study. A key theme that emerged was that an understanding of the SDGs-circular economy linkages in construction waste management is integral to establishing long-term innovative solutions for developing multi-sectorial measures for waste prevention, eco-design, and re-use of materials. These linkages increase competitiveness, stimulate innovation, and boost economic growth. This study proposes that all stakeholders who generate waste should apply new innovative technologies, methods and strategies leading to transdisciplinary and transformative change.
TL;DR: In this article , the authors demonstrate that deploying wind and solar capacity within flexible and optimized grids can meet ∼67% of electricity demands by all society sectors for 2050 (∼6.3% curtailment rate), even without other costly power sources or storage.
Abstract: China's goal of being carbon-neutral by 2060 requires a green electric power system dominated by renewable energy. However, the potential of wind and solar alone to power China remains unclear, hindering the holistic layout of the energy development plan. Here, after taking temporal matching of supply and demand (60 min), land use, and government policy into account and assuming lossless transmission, we demonstrate that deploying wind and solar capacity of 2495 and 2674 GW, respectively, within flexible and optimized grids can meet ∼67% of electricity demands by all society sectors for 2050 (∼6.3% curtailment rate), even without other costly power sources or storage. Spatially explicit configurations of the grids are provided simultaneously to support this achievement. The resulting green electricity supply of 10.4 PWh per year help secure China's carbon-neutral goal and reduces 2.08 Mt SO2 and 1.97 Mt NOx emissions annually. Our findings recommend policymakers accelerate exploiting complementary wind and solar power as the dominant source of energy.
TL;DR: In this paper , a review comprehensively illustrates the stress-induced strategies of recent studies and achievements in promoting the lipid accumulation of microalgae, and the possible mechanisms of using phytohormone and abiotic stress to enhance the micro-algae lipid biosynthesis are discussed.
Abstract: Microalgae have been proposed as a potential renewable energy source for biofuel production. However, owing to the low biomass concentration and lipid productivity, the sustainable and industrialized production of microalgae biofuels is still limited. New lipid improvement strategies have appeared at the technology forefront to overcome the bottlenecks. This review comprehensively illustrates the stress-induced strategies of recent studies and achievements in promoting the lipid accumulation of microalgae. Different stress-induced strategies for improving lipid production such as the use of phytohormone, change of cultivation strategies, combined chemical additives and abiotic stresses (nutrient stress, metal ions and wastewater, etc.) are addressed. After a comprehensive analysis, it is shown that the use of phytohormone combined with abiotic stress under two-stage culture condition is a promising stress-induced strategy to promote the microalgae lipid accumulation. Furthermore, the possible mechanisms of using phytohormone and abiotic stress to enhance the microalgae lipid biosynthesis are discussed. This review is dedicated to further accelerate the sustainable development and practical application of microalgae-based biofuel production.
TL;DR: Zhang et al. as mentioned in this paper constructed a framework for evaluating the green transformation performance (GTP) of resource-based cities in China, measured the GTP of 115 prefecture-level and above resource based cities using the entropy weight-TOPSIS model, and further quantitatively assessed the policy effects of sustainable development planning (SDP) in China's resourcebased cities from both the overall and local levels using synthetic control method.
Abstract: Scientific evaluation of the transformation effect of resource-based cities is an important way to measure the effect of the implementation of national transformation policies, and it is also an important issue in the study of China's urban transformation development under the "30-60" goal of carbon peaking and carbon neutral. Based on the systematic understanding of the connotation of green transformation development in resource-based cities, this study constructed a framework for evaluating the green transformation performance (GTP) of resource-based cities in China, measured the GTP of 115 prefecture-level and above resource-based cities in China using the entropy weight-TOPSIS model, and further quantitatively assessed the policy effects of sustainable development planning (SDP) in China's resource-based cities from both the overall and local levels using synthetic control method. The results showed the following. (1) Time-series evolution characteristics analysis results showed that the average GTP allocation level of China's resource-based cities showed a steady upward trend in 2009 to 2018, from 0.4196 in 2009 to 0.4946 in 2018, an increase of 17.88%, and the growth rate showed a "W"-type fluctuating change characteristics. (2) Spatial differentiation characteristics analysis results showed that the average GTP allocation level of resource-based cities showed the heterogeneous characteristics of "east>middle>west", "regenerative type> growth type> mature type> declining type", and "ferrous metals> oil and gas> non-metals> forest industry> coal> non-ferrous metals". (3) Overall policy effects analysis results showed that the implementation of the SDP policy had a weak positive promotion effect on the overall transformation and development of resource-based cities. The overall policy effect showed an "M"-type fluctuation trend, with a more obvious pushing effect at the early stage of policy implementation, and then showed a fluctuation and weakening trend. (4) Local policy effects analysis results showed that the implementation of the SDP policy had different impacts on the green transformation and development of different resource-based cities. This policy has positively promoted the GTP of mature cities (e.g., Panzhihua City) and declining cities (e.g., Jiaozuo City), while it has not significantly promoted the GTP of growth cities and regenerative cities. These findings can provide a reference for the optimization and improvement of sustainable development policies in resource-based cities in China.
TL;DR: In this article, the role of rice husk ash (RHA) on thermal stability and thermal insulation of geopolymer foamed material (GFM) was systematically investigated.
Abstract: This study reports the preparation and characterization of alkali-activated slag based geopolymer foamed material (GFM). The roles of rice husk ash (RHA) on thermal stability and thermal insulation of GFM were systematically investigated. Thanks to the low self-weight and good reactivity of RHA, the compressive strength and specific compressive strength of GFM are enhanced, promoting the lightweight and high-strength developments of GFM. More importantly, the replacement of GGBS by RHA efficiently mitigates the strength degradation, reduces the weight loss and increases the volumetric stability of GFM during thermal exposure. The thermal conductivity of GFMs registered from 0.1102-0.2891 W/m•K reflects good thermal insulation characteristic, which is better than the reported thermal insulation properties of other alkali-activated foamed materials system at the same strength/density level. The mechanism of RHA acting on GFMs is closely related to the property characteristics of RHA itself, basic properties enhancement and pore structure development of GFMs. With the use of 20 wt.% RHA, the GFM containing 2 wt.% H2O2 exhibits the optimal comprehensive properties: 0.01270 × 103kN•m/kg specific compressive strength, 827 kg/m3 volume density, 10.5MPa compressive strength, 0.1331 W/m•K thermal conductivity and better volumetric stability.
TL;DR: In this paper , the role of rice husk ash (RHA) on thermal stability and thermal insulation of geopolymer foamed material (GFM) was systematically investigated.
Abstract: This study reports the preparation and characterization of alkali-activated slag based geopolymer foamed material (GFM). The roles of rice husk ash (RHA) on thermal stability and thermal insulation of GFM were systematically investigated. Thanks to the low self-weight and good reactivity of RHA, the compressive strength and specific compressive strength of GFM are enhanced, promoting the lightweight and high-strength developments of GFM. More importantly, the replacement of GGBS by RHA efficiently mitigates the strength degradation, reduces the weight loss and increases the volumetric stability of GFM during thermal exposure. The thermal conductivity of GFMs registered from 0.1102-0.2891 W/m•K reflects good thermal insulation characteristic, which is better than the reported thermal insulation properties of other alkali-activated foamed materials system at the same strength/density level. The mechanism of RHA acting on GFMs is closely related to the property characteristics of RHA itself, basic properties enhancement and pore structure development of GFMs. With the use of 20 wt.% RHA, the GFM containing 2 wt.% H2O2 exhibits the optimal comprehensive properties: 0.01270 × 103kN•m/kg specific compressive strength, 827 kg/m3 volume density, 10.5MPa compressive strength, 0.1331 W/m•K thermal conductivity and better volumetric stability.
TL;DR: In this paper , the effects of reprocessing/recycling on the material properties of NFRPCs are discussed, including mechanical performance, thermal properties, hygroscopic behavior, viscoelasticity, degradation, and durability.
Abstract: Natural fibers have been widely used for reinforcing polymers attributed to their sustainable nature, excellent stiffness to weight ratio, biodegradability, and low cost compared with synthetic fibers like carbon or glass fibers. Thermoplastic composites offer an advantage of recyclability after their service life, but challenges and opportunities remain in the recycling of natural fiber reinforced polymer composites (NFRPCs). This article summarized the effects of reprocessing/recycling on the material properties of NFRPCs. The material properties considered include mechanical performance, thermal properties, hygroscopic behavior, viscoelasticity, degradation, and durability. NFRPCs can generally be recycled approximately 4–6 times until their thermomechanical properties change. After recycling 7 times, the tensile strength of NFRPCs can decrease by 17%, and the tensile modulus can decrease by 28%. The mitigation approaches to overcome degradation of material properties of NFRPCs such as adding functional additives and virgin plastics are also discussed. The main challenges in these approaches such as degradation and incompatibility are discussed, and an effort is made to provide a rationale for reprocessing/recyclability assessment. Future applications of NFRPCs such as additive manufacturing and automotive part use are discussed.
TL;DR: In this paper, the effects of reprocessing/recycling on the material properties of NFRPCs are discussed, including mechanical performance, thermal properties, hygroscopic behavior, viscoelasticity, degradation, and durability.
Abstract: Natural fibers have been widely used for reinforcing polymers attributed to their sustainable nature, excellent stiffness to weight ratio, biodegradability, and low cost compared with synthetic fibers like carbon or glass fibers. Thermoplastic composites offer an advantage of recyclability after their service life, but challenges and opportunities remain in the recycling of natural fiber reinforced polymer composites (NFRPCs). This article summarized the effects of reprocessing/recycling on the material properties of NFRPCs. The material properties considered include mechanical performance, thermal properties, hygroscopic behavior, viscoelasticity, degradation, and durability. NFRPCs can generally be recycled approximately 4–6 times until their thermomechanical properties change. After recycling 7 times, the tensile strength of NFRPCs can decrease by 17%, and the tensile modulus can decrease by 28%. The mitigation approaches to overcome degradation of material properties of NFRPCs such as adding functional additives and virgin plastics are also discussed. The main challenges in these approaches such as degradation and incompatibility are discussed, and an effort is made to provide a rationale for reprocessing/recyclability assessment. Future applications of NFRPCs such as additive manufacturing and automotive part use are discussed.
TL;DR: In this paper, the systematic and sequential processes adopted for PCB metallic recoveries via physical, pyrometallurgical, hydromet alloys, and combined technologies are discussed, and an integrated, definite framework for full resource recovery from waste PCBs was proposed.
Abstract: Printed circuit boards (PCBs) are an essential and central component of electronic waste. The rapid depletion of natural resources, massive generation of end-of-life PCBs and inherently metal-loaded values inevitably call for recycling and recovery. This review critically discusses the systematic and sequential processes adopted for PCB metallic recoveries via physical, pyrometallurgical, hydrometallurgical, and combined technologies. Pre-treatments play a decisive and significant role in upgradation and efficient metal extraction. A novel combination of different pre-treatments and hybrid thermal-chemical routes are often reported for improved separation efficiency and performance. Selective recovery (using solvent extraction, precipitation, polymer inclusion membrane, adsorption, ion exchange) of high purity product from multi-elemental leach solution has recently gained interest and is reviewed. Current recycling techniques at a commercial scale are preferably based on pyrometallurgy (smelting-refining), where electronic waste is only a fraction of the total feed stream. Electronic components such as monolithic ceramic capacitors, tantalum capacitors, integrated circuits, and central processing units mounted on the PCBs are important due to precious metals' presence. The futuristic recycling perspective should treat base and precious metal-rich components separately with minimal environmental effect, end product usage, and maximum economic benefit. Sustainable processing routes for converting discarded PCBs into value-added products should also be attempted, as amplified in this review. An integrated, definite framework for full resource recovery from waste PCBs was proposed.
TL;DR: In this article , a review of the recent works applying chemometric methods to plastic waste sorting is presented, which includes principal component analysis (PCA), linear discriminant analysis (LDA), partial least square (PLS), k-nearest neighbors (k-NN), support vector machines (SVM), random forests (RF), artificial neural networks (ANNs), convolutional neural network (CNNs), and K-means clustering.
Abstract: Mismanagement of plastic waste globally has resulted in a multitude of environmental issues, which could be tackled by boosting plastic recycling rates. Chemometrics has emerged as a useful tool for boosting plastic recycling rates by automating the plastic sorting and recycling process. This paper will comprehensively review the recent works applying chemometric methods to plastic waste sorting. The review begins by introducing spectroscopic methods and chemometric tools that are commonly used in the plastic chemometrics literature. The spectroscopic methods include near-infrared spectroscopy (NIR), mid-infrared spectroscopy (MIR), Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS). The chemometric tools include principal component analysis (PCA), linear discriminant analysis (LDA), partial least square (PLS), k-nearest neighbors (k-NN), support vector machines (SVM), random forests (RF), artificial neural networks (ANNs), convolutional neural networks (CNNs) and K-means clustering. This review revealed four main findings. (1) The scope of plastic waste should be expanded in terms of types, contamination and degradation level to mirror the heterogeneous plastic waste received at recycling plants towards understanding potential application in the recycling industry. (2) The use of hybrid spectroscopic method could potentially overcome the limitations of each spectroscopic methods. (3) Develop an open-sourced standardized database of plastic waste spectra would help to further expand the field. (4) There is limited use of more novel machine learning tools such as deep learning for plastic sorting.
TL;DR: Wang et al. as mentioned in this paper designed and developed a garbage classification system based on deep learning that can recognize and recycle domestic garbage, focusing on the problems of low accuracy and poor real-time performance.
Abstract: Garbage classification technology is not only an important basis for the harmless treatment of waste and resource recovery, but also the inevitable trend of social development. The current garbage classification methods rely on manual classification in the garbage collection stage, and it is difficult to achieve satisfying results in consistency, stability, and sanitary conditions. For this reason, this study designs and develops a garbage classification system based on deep learning that can recognize and recycle domestic garbage. Focusing on the problems of low accuracy and poor real-time performance, a lightweight garbage classification model GCNet (Garbage Classification Network) is proposed. GCNet contains three improvements on ShuffleNet v2, including the design of parallel mixed attention mechanism (PMAM), the use of new activation functions, and transfer learning. The experimental results show that the average accuracy of GCNet on the self-built dataset is 97.9%, the amount of model parameters is only 1.3M, the single inference time on Raspberry Pi 4B is about 105ms, and the classification system needs only 0.88 seconds to complete the classification and collection of a single object. The method proposed in this paper is an effective attempt at machine vision in garbage classification and resource recovery. With the improvement of technology, it will effectively promote academic exploration and engineering application in the field of resources and environment.
TL;DR: In this article , a multidimensional scenario analysis was developed for 2012 to 2030 to analyze the material flows from batteries of passenger electric vehicles in China and the USA to estimate the future lithium-ion batteries market in the USA and China and its influences on the materials demand, end-life reaching of LIBs material, and second use based on three different scenarios.
Abstract: In the fight for reducing GHG emissions from road transport, electromobility has gained huge attention in recent years. However, the higher adoption of battery electric vehicles in the transportation sector will increase the demand for battery materials, including nickel, lithium, copper, cobalt, and graphite. Therefore, this study estimates the future lithium-ion batteries (LIBs) market in the USA and China and its influences on the materials demand, end of life reaching of LIBs material, and second use based on three different scenarios. For this purpose, a multidimensional scenario analysis was developed for 2012 to 2030 to analyze the material flows from batteries of passenger electric vehicles in China and the USA. The result suggests strong benefits of a circular battery values chain. The results from three scenarios showed that in 2030 there would be around 5–7 kt of recovered Li, 35–60 kt of recovered Ni only in China. Based on the economic evaluation of LIBs in scenario 2, it was found that recovered nickel would have the economic values of 725 million US dollars only in 2030 in China. Through the second use assessment of LIBs in the third scenario, where 50% of used batteries were assumed for second use application, it was found that around 33 GWh batteries would be available for second use only in 2030 in China. Therefore, the larger portion of used LIBs should be utilized for a second life as it could further delay the recycling of LIBs, which can further give time to the government so that the improved and larger recycling infrastructure could be built to tackle a higher amount of coming used LIBs.
TL;DR: Zhang et al. as discussed by the authors applied zero sum gains data envelopment analysis (ZSG-DEA) model combined with entropy model to allocate China's renewable energy quota from provincial perspectives.
Abstract: Renewable energy policy plays an important role in achieving carbon neutrality which is main goal for climate change mitigation. China is striving to promote the implementation of renewable portfolio standards under the goal of carbon neutralization in 2060. Thus, based on the principles of equality and efficiency, we apply zero sum gains data envelopment analysis (ZSG-DEA) model combined with entropy model to allocate China's renewable energy quota from provincial perspectives. Further, we introduce an environmental Gini coefficient to evaluate the rationality of allocation results. The allocation results show that Guangdong, Jiangsu, Sichuan and Shandong are four provinces with the most renewable energy quota, while Hainan, Guizhou, Gansu, and Xinjiang are four provinces with the least quota. In addition, the quota allocation results have achieved the goal of transferring the responsibility of renewable energy quota from western provinces to eastern provinces. Last, managerial suggestions in promoting renewable energy development are discussed.
TL;DR: In this paper, the authors present a dashboard that can be used at various spatial levels to guide the agri-food sector toward a more sustainable development model in line with the principles of the circular economy (CE).
Abstract: The agri-food sector is one of the key sectors where the action is needed to ensure the transition to a more sustainable development model in line with the principles of the circular economy (CE). The use of indicators to monitor progress and areas for action is a key element in the shift of companies, regions, and countries toward a circular model. This study aims to create a dashboard that can be used at various spatial levels to guide the agri-food sector toward a CE and sustainable development. Starting with the relevant literature, we identified 102 indicators classified according to three areas of sustainability (environmental, economic and social) and spatial dimensions (macro‑meso-micro) within 8 scopes. The dashboard provides a toolbox for directing decision-making processes and strategies through the targeted use of indicators with respect to the context in which the CE is applied. In addition, the dashboard allows us to highlight missing aspects related to (1) new indicators not covered by the tool; (2) new scopes not yet explored in the literature; and (3) the need to adopt cross-sectional indicators. For this last aspect, the analysis revealed only 17 such indicators. A future step is to define the most suitable configurations among the indicators in which CE is generated, starting from the test of the indicators at the micro level to validate their applicability and consider the impacts they may have at the macro or meso levels.
TL;DR: In this article, the authors focused on the factors which affect consumers' intention to use EVs in the Malaysian context, including environmental concern, trust in EVs, personal norms, price value, attitudes regarding EVs, and subjective norms.
Abstract: Today's societies consider the transportation sector as a key component of the economy that contributes significantly to sustainability and global economic development. However, the challenges resulting from transportation are expected to increase more seriously in the years to come in light of socioeconomic growth and increasing living standards. One of the most unfavorable outcomes of the transportation industries is climate change, which necessitates sustainable strategies to reduce emissions of greenhouse gasses. Although the use of electric vehicles (EVs) has obvious social advantages, including improvements to air quality along with beneficial effects of reducing CO2 emissions, EVs are being adopted quite slowly as a clean and green alternative form of transportation in Malaysia. Therefore, the present study has focused on the factors which affect consumers’ intention to use EVs in the Malaysian context. An extensive review of previous studies was carried out to identify the determinants of adopting EVs in the prior literature. The survey questionnaire was designed with reference to the decision-making trials alongside the Decision-Making Trials and Evaluation Laboratory (DEMATEL) method, after which questionnaires were distributed to Malaysian consumers of EVs. According to the results of the data analysis, environmental concern, trust in EVs, personal norms, price value, attitudes regarding EVs, and subjective norms are the most important factors influencing the adoption of EVs in the Malaysian context. The findings of the study provide directions for policymakers and automotive manufacturers.
TL;DR: In this article , the feasibility of pyrolysis scenarios as sewage sludge treatment processes through cradle-to-gate life-cycle assessment and additional energy consumption, carbon emission, and economic benefit analyses, considering circular economy principles.
Abstract: • Biochar and bio-oil pyrolysis are promising as innovative sludge treatment options. • AC pyrolysis has high toxicity but low GWP and energy demands. • Gas energy recovery reduces energy demands by 21–34% but increases the GWP burden. • Biochar and bio-oil pyrolysis both achieve a positive energy balance. This study aimed to determine the feasibility of pyrolysis scenarios as sewage sludge treatment processes through cradle-to-gate life-cycle assessment and additional energy consumption, carbon emission, and economic benefit analyses, considering circular economy principles. The examined pyrolysis scenarios include slow pyrolysis with various residence times to produce activated carbon (AC) or biochar and fast pyrolysis to produce bio-oil, all with internal gas energy recovery. The functional unit (FU) in this study comprises 1000 kg of dried sludge entering the pyrolysis reactor. The overall evaluation and new product application routes address gaps in current studies on sludge treatment via pyrolysis. Environmentally, the bio-oil (-0.31 kg CO 2 -eq/kg FU) and biochar (-0.05 kg CO 2 -eq/kg FU) scenarios show considerable improvement over contemporary pyrolysis and other conventional sludge treatment methods. The AC scenarios have higher toxicity but lower carbon emissions (1.50–1.70 kg CO 2 -eq/kg FU) than contemporary AC production processes. Chemical reagent usage has significant effects on the environmental burden of AC production processes. The biochar and bio-oil pyrolysis scenarios achieve net energy recovery through product applications. Although the AC scenarios still require energy input, this demand can be significantly reduced by optimising moisture removal processes. Operating cost analysis indicates that the examined pyrolysis scenarios are potentially profitable. Primary product yield and market value are significant factors determining the net profit of these pyrolysis scenarios, but further assessment of capital costs is required. This study shows that bio-oil and biochar pyrolysis are eco-friendly sewage sludge treatment methods.
TL;DR: In this paper , the authors propose a sustainable solid waste management model and address opportunities and challenges for waste reuse and recycling in a developing country, and a hybrid approach is adopted using a systematic data-driven analysis comprising content analyses, system uncertainty and complexity, the fuzzy Delphi method, interpretive structural modeling, and the fuzzy decision-making trial and evaluation laboratory.
Abstract: This study enriches sustainable solid waste management knowledge by establishing a valid hierarchical model and critiques the causal interrelationship between waste reuse and recycling attributes. The challenges and opportunities for sustainable waste reuse and recycling are emphasized, and direction is provided for practices. Many developing and emerging countries have been attempting to address solid waste management problems and serious restrictions on material reuse and recycling activities. However, it is not well developed, and reuse and recycling efforts have not yet been well implemented due to weak economic and political institution levels. This study aims to propose a sustainable solid waste management model and address opportunities and challenges for waste reuse and recycling in a developing country. A hybrid approach is adopted using a systematic data-driven analysis comprising content analyses, system uncertainty and complexity, the fuzzy Delphi method, interpretive structural modeling, and the fuzzy decision-making trial and evaluation laboratory. The results show that 19 valid indicators are congregated into five aspects, in which circular resource management, societal requirements, and municipal sustainability are causative aspects with the capability to improve sustainable solid waste management as it regards waste reuse and recycling. The top prominent indicators helping to enhance practices are the circular economy, the informal sector, material flow analysis, policy restrictions, waste treatment technologies. The state-of-the-art literature is presented, and further opportunities and challenges are determined.