查看更多>>摘要：The currently fossil-based production and highly linear use of polymer products generates significant amounts of CO2 emissions and irretrievably wastes resources. To address these challenges, effective and competitive technologies are required to enhance the circularity of carbon use. In this study economic and environmental effects of the use of CO2 as carbon source for polymer products such as packaging, construction material or medical products are analyzed. Thereby, the whole value chain, from the CO2 source to the market-ready product is considered. Material flow cost accounting is combined with environmental indicators to assess 28 possible CO2-based value chains. Data envelopment analysis (DEA) is used to compare the alternatives and to identify the most eco-efficient examples considering production costs, CO2-emissions, energy demand and fossil carbon use. In all cases, a significant reduction of CO2-emissions is achieved compared to the conventional alternative. For subsequently produced consumer products with a high value, the additional costs for CO2-based value chains are between 0.7 - 4% in the status quo and 0.1 - 1% in a future scenario which enables a market entrance for CO2-based products with comparably small price premiums. Considering the studied assessment indicators, the use of CO2 can already lead to the same or a similar overall performance compared to fossil-based production. The choice of the right product and value chain set up is decisive, with economies of scale playing a significant role. The results further show that costs and benefits are currently imbalanced along the value chain, wherefore an effective cooperation is key to achieve market readiness.
查看更多>>摘要：The construction sector consumes high amounts of resources and energy while generating significant amounts of waste. This development is contrary to Circular Economy principles, which require buildings that are resource and energy efficient and enable material recycling to the greatest possible extent. To effectively tackle this problem, the EU places a strong focus on sustainable building design. However, to assess this development, indicators that measure the potential recyclability of buildings already at the design stage are necessary. In this study, the "Relative product-inherent recyclability " (RPR) assessment method is applied to evaluate the recyclability of buildings. The RPR method considers buildings' material composition and structure (assembly) to measure recyclability, thereby describing recycling-relevant factors. The method is based on the statistical entropy approach, which aims to describe material distributions. The RPR increases the more building parts can be disassembled, allowing recovery of concentrated materials. A case study on a timber and concrete building is used to demonstrate the applicability of the RPR metric. The results show that the RPR metric is a suitable indicator for expressing buildings' inherent recyclability, thus identifying significant differences between building variants. Relevant design optimizations can be deduced from the RPR results. In our case, the timber building achieves higher recyclability than the concrete building. Applying the RPR indicator on the EU level can be recommended and offers significant insights into the design and recyclability of buildings. Architects and constructors could use the metric as a planning and evaluation tool, thereby promoting circular building design concepts.
Ul Islam, Mohammad MomeenLi, JieWu, Yu-FeiRoychand, Rajeev...
25页
查看更多>>摘要：End-of-life tires are a challenging waste because of their non-biodegradable properties, high production volume, and low utilization rate. Extensive research is currently being undertaken to look for various applications of waste tire rubber in the concrete industry to improve their utilization rate and significantly increase the uptake of this waste material. However, low strength and poor bond performance between rubber aggregates and cement matrix are hindering its application in the concrete industry. This paper introduces an innovative method of prestressing the coarser rubber aggregates (RAs) to address these challenges and limitations found in the critical literature review. Two steel mould rigs were newly designed for manufacturing the rubberized concrete (RuC). Three different mix designs containing 100% replacement of conventional coarse aggregates were prepared using (i) two different sizes of rubber particles and (ii) the addition of steel fibers. Density, SEM-EDS analysis, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity were undertaken to evaluate mechanical performances. The experimental results depict that this novel preloading method can bring a maximum of 97%, 59%, and 20% increase in compressive strength, flexural and tensile strength compared to that of the normal RuC, respectively. In addition, it provides a significant improvement in the interfacial tran-sition zone between the matrix and RAs. This study demonstrates the efficient scientific recycling procedures in manufacturing the RuC with a maximum compressive strength of 18 MPa (density of 2000 kg/m3), which can be considered structural lightweight concrete as per ACI 213R-14 and Eurocode 2 recommendations.
查看更多>>摘要：Facing the urgent need for more sustainable construction materials all over the world, mortars containing the agricultural by-product Rice Husk Ash (RHA) as supplementary cementitious material (SCM) were investigated. Pozzolanic activity, microstructural investigations through Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, compressive strength and durability properties were examined and compared to properties of mortars either without SCM or with equivalent amounts of fly ash and limestone powder. It was found that mortar samples with a cement substitution of 25 wt.-% by RHA showed a higher strength than the comparison samples at hydration ages of 7 to 90 days. Durability investigations, namely carbonation resistance and capillary suction, showed an increased performance of RHA mortars due to their dense microstructure. Microstructural analysis found that especially in the early hydration during the first hours after water addition, an accelerated reaction rate of the RHA mortars led to an increased heat flow and thus build-up of hydration products. A strong pozzolanic reaction, calculated through the measurement of decreasing crystalline phase amounts with XRD, was shown with increasing hydration time. Altogether, the investigations provide important insights into the usability of RHA in concrete. The enhanced strength development as well as the low water absorption and thus small capillary porosity indicate that the RHA is a suitable pozzolanic additive for both sustainable and durable concrete.
Edenbrant, Anna KristinaNayga, Rodolfo M.Bolos, Laura AndreeaLagerkvist, Carl-Johan...
12页
查看更多>>摘要：This study investigates how framing in relation to environmental consequences directs consumers to prioritize among gain, hedonic, and normative goals when accepting suboptimal food to reduce food waste. A random sample of 1,704 United States consumers completed a three-wave survey instrument, including repeated discrete choice experiments. Goals related to gains deteriorated substantially over time. Goals for reducing environmental impact by purchasing sub-optimal food were stronger and more time-invariant. There was no increase in goal strength for reduce environmental impact due to the type information provided. Furthermore, there was no support for a lower decrease across time in normative goal strength due to exposure to positive framing. There were combined effects of information and time, respectively. Five latent groups were identified. These results are relevant for actions to increase the acceptance of suboptimal food, finding that differences in consumer preferences are attributable to goal type and goal strength.
Andersen, RuneRavn, Anders StokbroRyberg, Morten Walbech
10页
查看更多>>摘要：This study presents a comparative life-cycle assessment (LCA) of two alternatives for the end-of-life handling of steel facade cladding from demolished buildings. The main objective is to investigate the environmental benefits of eighteen different environmental impact categories to indicate the respective potential impacts of the two demolition alternatives. We compare the selective demolition of facade cladding and the cladding's subsequent reuse with a conventional demolition scenario in which steel cladding is recycled as scrap. The study therefore expands the existing data foundation on selective demolition to support future decisions on the reuse of building components. The LCA was performed using parametric modeling to facilitate a thorough sensitivity and uncertainty analysis of the results. Results show that the environmental impact across all impact categories was generally lower for the selective scenario compared to the conventional demolition baseline scenario over the total evaluated life-cycle. However, we also see that the impacts related to the actual demolition process are higher for selective demolition due to the longer operating times of heavy machinery. This study contributes new knowledge on selective demolition processes, which can support decision-makers in choosing the most sustainable demolition practice. Through a comparison with the production of new products, it also becomes clear that there are environmental benefits to reusing components from demolition in connection with new constructions. Overall, this can help reduce the environmental impact of the construction sector.
查看更多>>摘要：Oil and gas production necessitates substantial use of water. Inspired by the water footprint theory, in this study, we proposed a novel factor to measure unconventional water use in various processing and production activities. The proposed factor was used to establish a method for evaluating the water footprint in oil and gas production. Through analyzing water use characteristics in oil and gas exploration, construction, production, and operation in China, it was found that the direct blue and grey water footprints of oil and gas production in 2018 were 3.08 and 6.64 m(3)/toe, respectively. Technological innovation and increased use of unconventional water reduced the blue water footprint. The unconventional water use factor was 4.61 m(3)/toe in 2018. Because of the growth of natural gas, especially unconventional production, China is predicted to require 1.42 billion m3 of water for oil and gas production in 2030, marking a 43% increase.
查看更多>>摘要：Wastewater post-coagulation sludge (WPCS) rich in amorphous Al/Fe can be reused as desirable adsorbents for phosphate (PO4-P). To address clogging issues in filter systems resulting from powder type, a granular substrate was prepared by co-pyrolyzing WPCS with bentonite and corncob. Mixture design method and response surface analysis were adopted to optimize the preparation condition. Results revealed the conflict and coordination of the components that PO4-P adsorption was positively correlated with WPCS content, while bentonite and corncob were indispensable for maximizing the erosion wear resistance. Pyrolyzing 70 wt.% WPCS, 25 wt.% bentonite and 5 wt.% corncob at 400 ? for 2 h under CO2 atmosphere yield the optimized porous and anti erosion substrate, which exhibited strong selectivity for PO4-P with a maximum adsorption capacity of 34.44 mg g(-1). Ligand exchange between Al/Fe and PO4-P was the dominant adsorption mechanism. Developing valueadded green substrates from waste by-products herein has significant environmental and economic benefits.
查看更多>>摘要：Dysprosium (Dy) is a critical rare earth element. However, its supply, consumption, trade, and recycling along the entire supply chain have not been clearly investigated, especially for China where most Dy is produced and used. This study quantified the Dy flows and stocks in mainland China during 1990--2019. Key findings are as follows: (1) domestic Dy demand increased by 16-fold during 2004-2019, driven by green technologies; (2) Dy mine production failed to grow significantly after 2010 under intensified environmental regulations; (3) China's total Dy exports increased steadily, with exported commodities changing from upstream to downstream prod-ucts; (4) in-use Dy stocks grew by 15-fold during 2006-2019, implicating big potentials of urban mining, but commercial recycling systems have not been established. This study reveals the importance of supply-demand monitoring, environmental governance, and global cooperation to Dy industries, and highlights the necessity of material flow analysis for improving metal supply chain management.
NSTL
Elsevier