查看更多>>摘要：In this paper, we have proposed a robust Printed Circuit Board (PCB) classification system based on computer vision and deep learning to assist sorting e-waste for recycling. We have used a public PCB dataset acquired using a conveyor belt, as well as a locally developed PCB dataset that represents challenging practical conditions such as varying lighting, orientation, distance from camera, cast shadows, view-points and different cameras/resolutions. A pre-trained EfficientNet-B3 deep learning model is utilized and retrained for use with our data in PCB classification context. Deep nets are designed for closed set recognition tasks capable of classifying only the images they have been trained for. We have extended the closed set nature of deep nets for use in our open set classification tasks which require identifying unknown PCBs apart from classifying known PCBs. We have achieved an open set average accuracy of 92.4% which is state of the art given the complexities in the datasets we worked with.
查看更多>>摘要：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.
查看更多>>摘要：On the long term, buildings could initiate less material flows and have improved environmental performance if they are designed for future disassembly and reuse. However, material flows in the building life cycle are difficult to map, especially those initiated by material replacements and at end-of-life. The calculation formula for the number of replacements in buildings in the Life Cycle Assessment standard EN 15978 neglects the effect such replacements may have on the surrounding interdependent building parts, and hence fails to capture the potential benefits of Design for Disassembly. In light of this shortcoming, we propose a method to model the flows of building parts initiated by the disassembly of a building, both during operational and end-of-life stages. This modeling method considers aspects of structural stability, accessibility, and the use of detachable connections. It offers a bottom-up time-based Material Flow Analysis of an entire building which can be integrated in a Life Cycle Assessment. We apply our method on a pavilion and compare the method results to the those obtained with EN 15978, considering nine design options. The life cycle environmental impact estimated with our method is up to 162% larger than the impacts calculated with EN 15978 for a pavilion with non-detachable connections, which demonstrates the importance of this design parameter. Our method can be of interest to researchers, Life Cycle Assessment and Life Cycle Costing auditors, architecture, engineering and construction professionals, urban miners and any other actors interested in the design of demountable buildings.
查看更多>>摘要：Sustainable management of waste electrical and electronic equipment (WEEE) offers a significant opportunity for resource recovery. However, the generation of plastics in WEEEs and the environmental impacts related to subsequent recycling have not been well addressed. This study estimates the generation volumes of plastics that are recycled from five typical kinds of WEEEs in China and analyzes the environmental performance of WEEE plastics recycling using life cycle assessment (LCA). The results show that recycled plastics from WEEEs increased from 231.6 kt in 2010 to 565.8 kt in 2018, by an average rate of 11.8% per year, with acrylonitrile-butadienestyrene (ABS), polypropylene (PP) and polystyrene (PS) being the three main components. In 2018, the estimated total electricity consumption and greenhouse gas emissions caused by Chinese WEEE plastics recycling reached 238.6 million kWh and 712.1 kt CO2 eq, primarily due to energy consumption, transportation and WEEE disassembling processes. Based on the results, we find that recycled plastics from WEEEs demonstrate better performance on most environmental aspects except for ozone depletion as compared to the production of virgin plastics. The ongoing ozone-depleting emissions imply an urgent need for additional actions to minimize potential refrigerant leakage in WEEE plastics recycling. This study provides essential information about the existing WEEE plastics recycling practices in China and offers valuable implications to enhance the recycling of plastic materials from WEEEs and achieve sustainable WEEE management.
查看更多>>摘要：Natural resources depletion is gradually becoming a critical burden on the environmental and ecological balance, pushing the development of artificial aggregates forward. In order to curb the shortage issues of natural aggregates and minimize the destruction of land topography, alkali-activated aggregates (AAA) have gradually become a hot topic in recent years as a new application of alkali-activated materials (AAM) with the benefits of utilizing industrial by-products and waste materials. This article provides an overall review of the manufacturing process and engineering properties of two types of artificial aggregates, cold-bonded AAA (CB-AAA) and sintered AAA (ST-AAA). Their applications in concrete, besides the mechanical evaluation, durability performance, and leaching behavior, are summarized based on the existing research outcomes. Finally, the future perspectives and challenges of artificial aggregates development are also proposed.
查看更多>>摘要：As global and local actors seek to address climate concerns, municipalities, regions, and countries are developing policies for the built environment to reach carbon neutrality. In most cases, however, current policies target new construction and operational carbon emissions only, thus omitting the significant carbon emission saving potential resulting from the reactivation of embodied carbon in existing buildings. This article describes the development of a high-resolution combined building stock model (BSM) and building energy model (BEM) on both building and urban scale using all residential buildings of Ithaca, NY, USA as a case study. The model offers a holistic, detailed and local perspective on operational and embodied carbon emissions, associated saving potentials at both the building and urban scale, and the linkages, trade-offs and synergies between buildings and energy use as a basis for decision-making. A circular economy (CE) in construction posited on the reuse and recycling of existing building materials, necessitates a detailed material inventory of the current building stock. However, the scale and nature of this endeavor preclude traditional survey methods. The modeling process described in this article instead engages a bottom-up data aggregation and analysis approach that combines detailed construction archetypes (CAs) and publicly available, higher-level municipal geospatial data with building metadata defining occupancy and systems to create an autogenerated, detailed 3D geometry. The resulting BSM and BEM can simulate both embodied carbon content and operational carbon emissions of individual buildings within a municipal study with minimal required input data and a feasible computational effort. This provides modelers with a new spatial and geometric fidelity to simulate holistic renewal efforts, and inform carbon neutrality policies and incentives towards the decarbonization of the built environment.
查看更多>>摘要：A short lifespan and increased consumption patterns make e-waste the world's fastest-growing waste stream. Computers are one of the most significant parts of e-waste. Recycling of e-waste has been introduced as the main solution to deal with environmental problems and to save natural mines. This research aims to investigate the bioleaching of Cu, Ni, and Al from computer printed circuit boards (CPCBs) using Penicillium simplicissimum. The adaptation phase began at 1 g/l CPCBs powder with 107 spores and final pulp density was reached at 30 g/l. The most effective parameters including pulp density, initial pH, and the sucrose concentration were optimized to achieve maximum simultaneous leaching efficiency of Cu, Ni, and Al. The results showed the main mechanism of Al and Ni leaching was acidolysis, while complexoysis was the main mechanism for leaching of Cu. The optimal conditions of 60 g/l sucrose concentration, 16 g/l pulp density, and initial pH 6 led to leaching of 100% Cu, 70% Ni, and 98% Al. Additionally, the initial CPCBs sample and the bioleaching residue were analyzed using XRD, HPLC, SEM, and FTIR. The HPLC results confirmed that gluconic and oxalic acids were the main metabolites produced by P. simplicissimum. The SEM micrograph revealed the effectiveness of the bioleaching process in metal leaching. FTIR spectra validated conversion of the molecular structure to simpler materials, as well as the presence of HIPS, PC, and PPO in CPCBs waste powder.
查看更多>>摘要：Globally, wilderness areas are being lost at a rate that outpaces their protection, which has adverse effects on the global environment. Rapid action is needed to understand the trends and consequences of global wilderness change. We present projections of global wilderness decline in 2100 under the influence of land-use change within the framework of the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES). The projections revealed that the decline of wilderness was deeply affected by different global socioeconomic development pathways. The total wilderness loss (4.74%) in scenario A2 (with slow technological innovation and traditional demand for biofuels) was much higher than in the other scenarios. Around 76.51% of the loss of global wilderness globally occurs occurred in South America, which will occur in Tropical and Subtropical Moist Broadleaf Forests. The smallest loss (0.08%) occurred in scenario B1 (with a high level of environmental consciousness). We found that wilderness losses in 2100 will be concentrated in some important biomes, which have relatively high-density carbon storage. These findings stress the importance of targeted wilderness protection to ensure the long-term integrity of ecosystems and the balance of the carbon cycle.
查看更多>>摘要：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.
NSTL
Elsevier