Resources, conservation & recycling advances最新文献

Food waste management has emerged as a pivotal issue with the acceleration of urbanization. Inappropriate treatment of food waste causes environmental contamination, resource squandering, and land occupation. This research explores optimal strategies in Beijing with an experimental case study on the bioconversion technology using black soldier fly larvae (BSFL), comparing centralized and decentralized approaches. We studied waste sorting behaviors influenced by community characteristics, employing an Agent-Based Model (ABM) and a mixed integer non-linear programming (MINLP). Results indicate that 29 % of Beijing's food waste could be suitably managed through decentralized methods with BSFL, particularly in outlying areas and densely populated suburbs. Decentralized treatment exhibits the potential to boost waste separation participation in medium-sized, close- knit communities. However, this approach encounters hurdles related to technological implementation, public perception, and urban planning. This study underscores the need for community-specific strategies and a concerted effort from communities, government, and the private sector in advancing sustainable urban food waste management.

Waste of Electrical and Electronic Equipment (WEEE) is one of the fastest growing waste streams in Europe. Only 42.5 % of WEEE is collected and recycled with even lower rates for small WEEE, leading to significant environmental pressures. Applying end-of-life (EoL) strategies helps to ensure raw material availability, increases price resilience and reduces environmental impacts.

This study analyses greenhouse gas (GHG) and cost saving potentials of EoL strategies (recycling, component reuse, remanufacturing and reuse), performed by manufacturers with own take-back systems. A life cycle assessment (LCA), including production, transport and EoL, is conducted to measure the GHG emissions, followed by a unit cost calculation. The results are compared with current practices of WEEE disposal, including WEEE in centralised collection and recycling system (WEEE recycling). As a representative for small EEE, the use case is based on a coffee machine.

The LCA shows that manufacturers have great potential to reduce their products' emissions over the life cycle by taking back WEEE and implementing EoL strategies in-house. Thereby, GHG emissions can be reduced by 15–39 % over the life cycle compared to the WEEE recycling, whereby reuse and remanufacturing strategies have the highest reduction potential.

Moreover, all analysed EoL strategies have the potential to reduce unit costs compared to linear production of a new machine. While the recycling scenario has the lowest cost savings at 7.7 % (new machine with recycled content), the reuse scenario can reduce unit costs by 66.5 % (tested and cleaned only) compared to the status quo.

The Circular Economy (CE) has been proposed as a strategy to promote the efficient use of resources, maximizing the benefits derived from materials and products through value recovery strategies, and minimizing waste generation. However, ambiguity remains in defining what makes a product circular and its characteristics when adapting the CE concept for application at the product level. More clarity about the constitutive characteristics of Circular Products (CPs) is also vital to facilitate their design. To address this challenge, and with the intention to increase the adoption of CE concept within the industry, the descriptions and attributes of a Circular Product (CP) were examined through a scoped literature review and analysis. Findings were then synthesized to establish a preliminary framework of CP attributes. These attributes were used to review the existing product circularity assessment methods. The results highlight limitations in the coverage of CP attributes in the existing methods and research opportunities for their improvement. The findings from this study will contribute to the development of a comprehensive and accurate product circularity assessment method.

Ordinary Portland cement (OPC) production requires heating limestone up to 1450 °C and produces 0.5–0.9 kg of carbon dioxide for every 1 kg produced. Moreover, the massive volume of cement manufactured around the world every year adds to the urgent need to look for sustainable alternatives. This work proposes a novel calcium oxide (CaO)-activated high-volume silica fume mixture as a cementitious binder for pavement application that can address the sustainability concern with cement (because producing CaO requires a much lower calcination temperature than OPC, and that CaO is also used in low-volume in the binder). The combination of low-volume CaO and high-volume silica fume, particularly as a pavement binder has not been studied in the literature before. The compressive and flexural strength results showed that even by using a small fraction of CaO in the binder, it is possible to obtain acceptable strengths that satisfy ASTM pavement design guidelines, while OPC is unable to provide similar strengths at such low dosage. The mix having CaO content as 30 % of the silica fume content (CSF-30) shows the highest compressive strength (28d: 18.4 MPa) and flexural strength (28d: 4 MPa). In contrast, the maximum OPC-silica fume compressive and flexural strengths observed are 13.9 MPa and 2.9 MPa respectively at 28d From the microstructural results, it was seen that CaO–silica fume develops strength due to formation of calcite and calcium silicate hydrate. Almost all CaO–silica fume mixes exhibited lower porosity compared to their OPC-silica fume counterparts; CSF-30, the mix having the best mechanical performance showed the lowest porosity at 28d (2.8 %). A comparative sustainability analysis followed by a 5D analysis considering all the parameters studied in this work revealed that CSF-30 is the best binder alternative (overall score: 5.24). The results of this work will be useful for pavement users, designers, researchers, engineers, and relevant government officials, in having a sustainable clinker-free alternative pavement binder to OPC, particularly for low-volume roads, that satisfies the pavement design guidelines.

Air source heat pumps (ASHP) are increasingly being recognised as a low carbon alternative to traditional fossil fuel type heating systems for residential buildings, with many countries targeting their mass deployment to meet their emissions reduction goals. However, the environmental impacts of ASHPs throughout their entire life cycle to include manufacture and end-of-life, as well as operation, have not received comprehensive attention to date. This study addresses this gap by conducting a review of research quantifying the life cycle impact of domestic ASHPs, coupled with an examination of technology uptake and deployment. By analysing the entire life cycle, from production to end-of-life, the ASHP's global warming potential is estimated to be 35.8 t CO2 equivalent over the lifetime of 17 years identified by the study. Additionally, the study conducts a comparative analysis of the operational footprint of selected countries based on their electricity carbon footprint and the ratio of embodied to operational footprint, which ranges from 4 to 65, indicating potential for improvement. Furthermore, the study calculates the global warming potential using both the seasonal performance factor specified by a heat pump manufacturer and real-world field trial data. The findings unveil a significant disparity of 20 % between the two methodologies, underscoring the paramount importance of incorporating in-field heat pump performance data when evaluating their environmental impact.

The imperative to mitigate carbon emissions and seek sustainable alternatives to cementitious materials has driven the advancement of geopolymer binders, which are inorganic binders of aluminosilicate industrial-waste materials activated by alkaline agents. The use of geopolymers carries the potential for significant reductions in greenhouse gas emission. Furthermore, the incorporation of plastic waste as aggregates addresses not only resource conservation but also environmental sustainability. This study conducted a comprehensive life-cycle assessment of the use of geopolymers from fly ash as a precursor with polyethylene terephthalate (PET) waste as a substitute for natural aggregates. It was observed that when replacing natural aggregates with PET waste to the maximum extent, the global warming potential (GWP) in the category of emissions related to aggregate preparation increased by 16.7 %. This increase was attributed to significant emissions generated during PET processing, including activities such as washing and grinding. The total GWP to produce one cubic meter of geopolymer mixture was 643.55 kgCO₂-e without PET aggregates and 667.86 kgCO₂-e with maximum use of PET aggregates. The optimization of energy-intensive PET preparation processes led to a remarkable reduction of 19.63 % for production of geopolymer mixture with maximum use of PET aggregates. These findings show the potential for improved sustainability in the production of geopolymer mixtures and emphasize the critical role of optimizing the production processes in mitigating their environmental impact.

Globalization has fueled the rapid expansion of international tourism, significantly impacting global food systems. This study aims to quantitatively evaluate the influence of tourism on global food greenhouse gas (GHG) emissions. By integrating the Food and Agriculture Organization Statistical Database and the World Tourism Organization Tourism Statistics database, we analyze regional differences in dietary choices among cross-border tourists and connect them to detailed national-level food supply inventories, enabling us to estimate the GHG emissions associated with cross-border tourism. Additionally, we employ the modified Regional Integrated model of Climate and the Economy (RICE) model to project future trends in tourism-related GHG emissions across regions and countries. Our findings indicate that tourism has resulted in a reduction of 620 Mt CO₂e in global food system emissions between 2001 and 2019. Taking into account tourism development trajectories and regional economic growth, our projection suggests that GHG emissions reduction from the global food system resulting from tourism could reach a substantial 96 Mt CO₂e per year by 2100. The analysis shows that strengthening the national economy and increasing the labor force, and taking reasonable measures to change the social diet pattern in different regions can further reduce tourism embodied food GHG emissions. This study highlights the significant role of tourism in mitigating global food system emissions and underscores the potential for further emission reductions in the future.

This research aims to investigate the factors that influence green behavior in two developing countries, Malaysia and Nigeria. The study is based on the theory of planned behavior (TPB) and reasoned action (TRA), and it includes additional factors such as green culture, green product trust, product value, price sensitivity, and environmental awareness. A total of 547 participants were surveyed using a quantitative approach. The results from the multi-group (MGA) and partial least squares-structural equation modeling (PLS-SEM) analyses indicated that the extended TPB/TRA model is valid in the chosen developing nations. The multi-country model shows a significant difference, especially in the path connecting attitude and price sensitivity towards green behavior. Consumers in both countries have a positive attitude towards environmental protection and exhibit a green culture towards eco-friendly practices. In both models, green product trust and value have a positive relationship with green behavior, but not with environmental awareness. Perceived behavioral control is positively linked to green behavior in Nigeria, but not in Malaysia. Green culture is the strongest predictor of green behavior, more so than attitude. These stimulus factors were stronger in Nigeria. In both countries, the relationship between green culture, price sensitivity, perceived behavioral control, and green behavior is mediated by attitude. The study suggests that consumers in the chosen developing nations are gradually embracing eco-friendly practices. The findings highlight the importance of promoting environmental awareness to encourage green behavior towards nature. The study further discusses the implications of these findings.

Food and other bio-waste management is an integral part of urban development and living. Composting is a common practice in most developed countries, while open burning and landfilling is widely used in waste management in low and middle income countries. The outputs of composting include compost, heat, leachate, and off-gas. The off-gas consists of carbon dioxide (CO2), methane, nitrous oxide, water vapor, ammonia and volatile organic compounds. The CO₂, although biogenic could contribute to climate change mitigation if the emissions are controlled. CO₂ sequestration using microalgae has been widely reported has been widely reported as a viable alternative to geological storage. CO₂ sources in microalgal cultivation include ambient air, composting off-gas, combustion flue gas, wastewater aeration gas, syngas, and biogas. Carbon dioxide from composting can be used in controlled environment agriculture instead of commercially produced alternative, or from ambient air. This review examines the available information on composting off-gas dynamics, particularly CO₂ evolution, and the challenges and prospects of CO₂ use in microalgal cultivation, ensuring circularity in the composting process. This review recommends the utilization of CO₂ from composting as alternative to direct air extraction. However, achieving higher CO₂ concentration relative to oxygen is challenging. While efforts are made towards reduction in greenhouse gas emissions during composting, near zero oxygen concentration in the off-gas is essential to enhancing CO₂ utilization in microalgae cultivation. This should be achieved without compromising compost quality such as germination index and chemical oxygen demand/heavy metals reduction efficiency.

The increasing growth of solar photovoltaic (PV) deployment raises end-of-life management concerns. Previous studies have forecasted PV waste; however, the implications of the regulations were not assessed. The present study estimates the volume and composition of end-of-life solar PV waste for the European Union and the United States. The recycling potential of generated waste and the fate of materials in end-of-life PV waste as per the present regulations is also estimated. Further, the work analyses solar manufacturers contributing to the waste and provides recommendations for improving solar PV waste management. The analysis in the present study shows that 24.93 million tonnes and 36.23 million tonnes (metric ton) of PV waste with an economic value of 189 billion USD and 262 billion USD are expected to be generated between 2025 and 2050 in the US and European Union, respectively. This work also indicates that the US lacks federal PV waste-specific management regulations and has different requirements across the states. In contrast, European countries have adopted the Waste Electrical and Electronic Equipment Directive in their national legislations in addition to country-specific PV manufacturer compliance schemes. Due to the lack of regulations, 20 MT of PV waste is expected to be disposed of in landfills in the US. Chinese manufacturers like Tongwei, Aiko, and LONGi are leading manufacturers of PV shipments globally. They could play a significant role in PV recycling and management if they adopt take-back programs and invest in recycling, contributing to future end-of-life PV waste management. In light of these observations, a need for greater synchronization between federal and state-level end-of-life PV regulations, collaboration among recyclers and PV industry stakeholders, and continued research and knowledge sharing is recommended. Secondly, incorporating emerging contaminants in PV waste regulations and waste characterization methods is required for responsible recycling and safe management.