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Environmental modelling of aluminium recycling: A Life Cycle Assessment tool for sustainable metal management
Abstract
Abstract The uncontrolled mixing of metals and their alloys during the different life cycle phases, combined with the melt purification constraints during remelting, pose great challenges during their end-of-life (EoL) treatment. In practice, open-loop recycling is typical and more common for metals than closed-loop recycling; especially in the case of aluminium, the industry operates in a cascade recycling approach. Associated with open-loop recycling are various types of material losses; loss of original functional quality, dissipation of scarce resources and the final need for dilution of the resulting metal impurities with primary materials. Thus, an environmental assessment tool is presented within this paper, aiming to support decision making related to the sustainable management of metal resources during secondary aluminium production. A material blending model aims at the minimization of the above mentioned losses in order to meet the product quality requirements. The goal of the study is threefold: i) to assess the environmental impact calculation of aluminium recycling, ii) to express, quantify and integrate dilution and quality losses into Life Cycle Assessment (LCA) studies, and iii) to determine the optimum material input for the recycling process from an environmental perspective. Different recycling options or strategies can be evaluated and compared based on avoided environmental impact. Case studies focusing on major post-consumer scrap streams are used to illustrate application areas and highlight the importance of altering and optimizing the raw material input. Finally, policy issues and opportunities for environmentally conscious metal management are discussed.
... Extrusion offers unique construction and design possibilities, with different functional characteristics ( [12,[15][16][17]). Also, it is an extremely complex process associated with several variables, from numerous sources and in the various phases of the process, and must be controlled to ensure product and customer's specificity's, as well as the minimum scrap production ( [18,19]). ...
... However, the acceleration time also helps to reduce the total extrusion cycle time and increase productivity ( [12]). [12,19] presented different ways to reduce the cycle time of each alloy and billet size. ...
... Temperature [18], [23], [27], [30], [31], [50], [32], [26], [24], [49], [25], [21], [12] and [20]. Time [30], [31], [32], [33], [19], [12] and [20]. Speed [18], [23], [27], [30], [31], [50], [32], [47], [21] and [12]. ...
In the discussion on environmental policies, the notion of eco-efficiency is often used. Eco-efficiency is defined as the delivery of products and services with competitive values, while reducing the ecological impacts and satisfying human needs. In an environment of great competitiveness in which the companies operate, the improvements in the productive process is one of the differentiating factors for guaranteeing a strong competition. Also it is essential rationalizing energy consumption and natural resources. For this it is necessary to understand the main operations and dynamics of the company. This work presents an empirical study of a Portuguese company in the industrial sector. The problematic here presented is based on the company’s growing concern to reduce the amount of scrap produced. From the literature research that was performed, a strong dependence relation between the different variables in the extrusion process was found. The main objective of this work is to model the aluminium extrusion process, with the aim of minimizing the production of scrap. For this several variables involved in the process are taking into account. Using statistical techniques, in particular multiple linear regressions, it was possible to identify the importance of the variables under study for the scrap production.
... 现有关于铝工业能耗和碳排放的研究多局限 于铝生命周期的特定阶段,如生产阶段 [6][7][8] 、产品使 用阶段 [9][10][11] 、废料回收和再利用阶段 [12][13][14][15] 等,没有分 析铝在全生命周期的能耗和碳排放量;同时研究的 数据来源于采矿公司 [7] 、国家年鉴 [8] 、欧洲铝业协 会 [9] 、Ecoinvent 数据库 [12] 等,数据获取方式不同使 结果易出现偏差;环境影响评价框架的生命周期边 界、地域和时间边界以及环境负荷边界不同 [6,10,12] , 边界具有不完整性、 不统一性;清单分析中的能源种 类 [8] 不同,缺乏统一的标准,研究结果的可比性差.仅 有少量文献对铝工业能耗碳排放量进行预测 [16][17][18][19] , ...
... 现有关于铝工业能耗和碳排放的研究多局限 于铝生命周期的特定阶段,如生产阶段 [6][7][8] 、产品使 用阶段 [9][10][11] 、废料回收和再利用阶段 [12][13][14][15] 等,没有分 析铝在全生命周期的能耗和碳排放量;同时研究的 数据来源于采矿公司 [7] 、国家年鉴 [8] 、欧洲铝业协 会 [9] 、Ecoinvent 数据库 [12] 等,数据获取方式不同使 结果易出现偏差;环境影响评价框架的生命周期边 界、地域和时间边界以及环境负荷边界不同 [6,10,12] , 边界具有不完整性、 不统一性;清单分析中的能源种 类 [8] 不同,缺乏统一的标准,研究结果的可比性差.仅 有少量文献对铝工业能耗碳排放量进行预测 [16][17][18][19] , ...
... 现有关于铝工业能耗和碳排放的研究多局限 于铝生命周期的特定阶段,如生产阶段 [6][7][8] 、产品使 用阶段 [9][10][11] 、废料回收和再利用阶段 [12][13][14][15] 等,没有分 析铝在全生命周期的能耗和碳排放量;同时研究的 数据来源于采矿公司 [7] 、国家年鉴 [8] 、欧洲铝业协 会 [9] 、Ecoinvent 数据库 [12] 等,数据获取方式不同使 结果易出现偏差;环境影响评价框架的生命周期边 界、地域和时间边界以及环境负荷边界不同 [6,10,12] , 边界具有不完整性、 不统一性;清单分析中的能源种 类 [8] 不同,缺乏统一的标准,研究结果的可比性差.仅 有少量文献对铝工业能耗碳排放量进行预测 [16][17][18][19] , ...
... He concluded that the introduction of CCS technologies leads to a significant decrease in the GWP indicator, while all other environmental indicators have a more or less significant increase compared to the conventional production process [24]. Dimos Paraskeva et al. [25] researched aluminum recycling LCA using the ReCipe impact assessment method to develop a Parametric LCA tool to simplify environmental impact calculation. The study incorporates the material hygiene concept during the recycling of aluminum that didn't get attention from other LCA studies [25]. ...
... Dimos Paraskeva et al. [25] researched aluminum recycling LCA using the ReCipe impact assessment method to develop a Parametric LCA tool to simplify environmental impact calculation. The study incorporates the material hygiene concept during the recycling of aluminum that didn't get attention from other LCA studies [25]. Jana Gerta et al. [26] conducted a cradle-to-gate LCA study to give a comprehensive life cycle assessment in one of the integrated steel mills in Germany to produce 1 kg of hot rolled coil having measured primary data collected for 2018. ...
A clear understanding of the major environmental impacts of steelmaking from scraps, as well as potential solutions involving a circular economy paradigm, is essential. This study is conducted to pave the way for using life cycle assessment (LCA) to have sustainable development and effective resource management by evaluating the environmental impacts of the steel rebar manufacturing process using secondary resources. It is a cradle-to-gate LCA that includes scrap collection and sorting, transportation, melting, continuous casting, billet reheating, and reinforcing bar rolling. Inventory data were acquired as primary data from the factory and secondary data from ecoinvent v3.8, 2021 version integrated with SimaPro 9.4.0.2 faculty version. All of the analyses in this LCA were conducted using the Recipe 2016 Midpoint (H)V1.00 and Endpoint (I)V1.00 impact assessment techniques taking one-ton reinforcing bar production as reference flow. This LCA study shows that using renewable energy and bulk transport systems has a significant advantage in reducing the environmental impact created during steel production processes. Because of this, the global warming potential created during the rebar manufacturing process is 467 kgCO2 eq as taken from the environmental impact calculation report. By charging hot billet from the continuous casting machine (CCM) to the rolling mill and using an efficient transportation system, the environmental impact of GWP can be reduced by 50%.
... The LCA has been identified as a reliable methodology for proving and analyzing environmental impacts throughout the life cycle of a product and as part of the decision-making process toward more environmentally friendly products [8]. In addition, LCA is proven to be used to analyze the environmental impact of metal-based products [9]. ...
... Previous researchers have carried out the use of LCA for measuring environmental impacts in several different research objects, such as in cement [10] [11][12], construction [13] [14], furniture [15] [16], electronics [17] and mining industries [18] [19]. Assessment of environmental impacts using LCA has also been carried out by several previous researchers in the iron and steel [20], aluminum [9], and nickel industries [21]. Of the several LCA studies in the metal industry that have been carried out, measurement has yet to be found for the brass metal industry, so this research will measure the environmental impact of the brass industry using LCA. ...
Sampurna Kuningan is a small and medium enterprises (SMEs) specializing in creating various brass metal handicraft products. They need to improve their efficiency in producing brass door handles within their manufacturing process. The issues mainly revolve around two tasks - dipping and refining processes. At the finishing stage, the chemical solution left from brass cleaning is improperly treated and disposed of in the sewer, wasting resources. This study’s primary objective is to evaluate the eco-efficiency index (EEI) value and propose improvement strategies to reduce the environmental impact caused by their production activities. The eco-efficiency measurement involves comparing the financial performance represented by the net value and the environmental performance measured as eco-cost. The eco-cost is calculated using a life cycle assessment through the Sima-Pro software. The results of the calculations indicate an EEI value of 2.22. The production process is both economically affordable and sustainable. However, there is a relatively high environmental impact during the finishing process. Improvement scenarios for this process include implementing water treatment or substituting finishing chemicals. Using citric acid for a brass door handle yields a significant average reduction in eco-cost, reaching approximately 50%.
... [6] Most of the wrought Al alloys are made from primary (high purity) ingots with limited quantity of scrap Al (often recycled in closed loops) because of the lower tolerances for impurities from the scrap metals. [7] It should be noted that the primary Al production is an energy-intensive process leaving 12 kg of CO 2eq /kg of carbon footprint (193 MJ/kg for smelting process) compared to a recycled alloy with an average of 1.2 kg of CO 2eq /kg (26 MJ/kg). [8] Cast Al-Si-based alloys containing other elements (Cu, Mg, Fe, Mn) possess excellent mechanical properties and fluidity that can be cast into thin sections using high-pressure die casting (HPDC) process. ...
... Generally, secondary alloys (A830, A383) have higher tolerant limits for impurities such as Fe (2 wt pct max) and act as a sink for absorbing more secondary Al alloys from mixed or downgraded scraps. [7,10] However, repeated recycling loops cause the entrainment of steel scraps arising from the sorting process (small prices that are difficult to sort) resulting in the gradual accumulation of higher Fe in the secondary alloys. [11,12] In the HPDC process, the presence of Fe or Mn (in low Fe-containing structural alloys) reduces the die soldering effect by the diffusion of Fe at the casting/ die interface; [9,13] however, exceeding a critical limit of Fe (about 0.2 wt pct) would result in severe loss of mechanical properties due to the formation of brittle Fe-based intermetallic phases. ...
The presence and morphology of Fe-containing intermetallic phases affect the mechanical properties of aluminum alloys, especially in secondary Al–Si-based cast alloys. Although strontium (Sr) addition of 50 to 500 ppm is known to refine the needle-type eutectic silicon structure, the influence of Sr on the formation of Fe-intermetallic phases remains unclear. The present work investigates the combined additions of Sr and Mn to Al–9Si–0.6Fe–0.35Mg (All compositions are in wt pct except otherwise stated.) alloys on the formation of Fe-intermetallic phases at different solidification rates from ~ 1.5 to ~ 60 °C/s. Long and branched-type AlFeSi phase with size ranging from 50 to 120 µm are more common when solidified at the rate of 1.5 °C/s regardless of Sr and Mn additions. However, at the fast solidification rate of 60 °C/s, a 60 ppm Sr addition significantly reduced the average length of needle-shaped AlFeSi phase to less than 3 to 5 µm. Thermodynamic simulations have been performed using CALculation of PHAse Diagrams (CALPHAD) models to predict the formation of various phases and their possible interactions during solidification. The results indicated that the combination of a high solidification rate and about 60 ppm of Sr is beneficial to refining the δ-Al3FeSi2 phase in Al–Si–Mg alloys containing 0.6 pctFe. This unexpected finding of Fe-intermetallic refinement by low Sr addition (~60 ppm) provides an important guide in designing secondary alloys for sustainable casting applications.
... The smaller part of the alloys is used for the production of deformable alloys, which have less tolerance regarding the content intervals of the main components and impurities. To produce recycled aluminum alloys from mixed scrap, there is a need of dilution with a large amount of primary aluminum [10][11][12], which increases the cost, and also leads to the depletion of natural resources and pollution of the atmosphere with greenhouse gasses [13,14]. ...
... During remelting, dilution losses occur due to the need for dilution the residual element concentration (e.g. iron) with primary aluminum [14,[82][83][84]; to avoid quality losses alloying elements are added. ...
... The main advantages of the iron aluminides in terms of environmental impact reduction are, that ferroalloys as used for casting wear resistant steels tend to have a high environmental impact and therefore contribute severely to the GWP of high-alloyed iron-based alloys [34], whereas primary aluminium shows less impact [35]. Substituting scrap aluminium for primary aluminium in production further lowers the environmental impact, since scrap aluminium shows lower overall environmental impact [36,37]. ...
... If primary aluminium is used for production, the electricity mix for the electrolytic Al smelting has a crucial influence on the emissions. Here, the use of scrap metal and a greener energy mix as intended in many European countries can achieve significant emission reductions [36,38]. ...
... 7 The topic is particularly important because the internationally available amount of "old" scrap (which refers to highly contaminated post-consumer scrap) grows much faster for some of the metals in need than the chemically well sorted and less contaminated high-quality industry scrap. 391,392 Hence, the research community must find out how metallic alloys can be made more robust against elemental contamination or how such impurities can be even turned into a benefit. ...
... Due to the low melting point of aluminum (660°C, and only moderately different for its alloys), the energy required for melting is only about 5% of that required for primary production. This qualifies secondary aluminum synthesis via use of scrap as the most effective and rapid pathway toward a more sustainable metallurgy of the aluminum sector, 2,7,9,54,101,392 Figure 72. ...
Production of metals stands for 40% of all industrial greenhouse gas emissions, 10% of the global energy consumption, 3.2 billion tonnes of minerals mined, and several billion tonnes of by-products every year. Therefore, metals must become more sustainable. A circular economy model does not work, because market demand exceeds the available scrap currently by about two-thirds. Even under optimal conditions, at least one-third of the metals will also in the future come from primary production, creating huge emissions. Although the influence of metals on global warming has been discussed with respect to mitigation strategies and socio-economic factors, the fundamental materials science to make the metallurgical sector more sustainable has been less addressed. This may be attributed to the fact that the field of sustainable metals describes a global challenge, but not yet a homogeneous research field. However, the sheer magnitude of this challenge and its huge environmental effects, caused by more than 2 billion tonnes of metals produced every year, make its sustainability an essential research topic not only from a technological point of view but also from a basic materials research perspective. Therefore, this paper aims to identify and discuss the most pressing scientific bottleneck questions and key mechanisms, considering metal synthesis from primary (minerals), secondary (scrap), and tertiary (re-mined) sources as well as the energy-intensive downstream processing. Focus is placed on materials science aspects, particularly on those that help reduce CO2 emissions, and less on process engineering or economy. The paper does not describe the devastating influence of metal-related greenhouse gas emissions on climate, but scientific approaches how to solve this problem, through research that can render metallurgy fossil-free. The content is considering only direct measures to metallurgical sustainability (production) and not indirect measures that materials leverage through their properties (strength, weight, longevity, functionality).
... 7 The topic is particularly important because the internationally available amount of "old" scrap (which refers to highly contaminated post-consumer scrap) grows much faster for some of the metals in need than the chemically well sorted and less contaminated high-quality industry scrap. 391,392 Hence, the research community must find out how metallic alloys can be made more robust against elemental contamination or how such impurities can be even turned into a benefit. ...
... Due to the low melting point of aluminum (660°C, and only moderately different for its alloys), the energy required for melting is only about 5% of that required for primary production. This qualifies secondary aluminum synthesis via use of scrap as the most effective and rapid pathway toward a more sustainable metallurgy of the aluminum sector, 2,7,9,54,101,392 Figure 72. ...
Production of metals stands for 40% of all industrial greenhouse gas emissions, 10% of the global energy consumption, 3.2 billion tonnes of minerals mined, and several billion tonnes of by-products every year. Therefore, metals must become more sustainable. A circular economy model does not work, because market demand exceeds the available scrap currently by about two-thirds. Even under optimal conditions, at least one-third of the metals will also in the future come from primary production, creating huge emissions. Although the influence of metals on global warming has been discussed with respect to mitigation strategies and socio-economic factors, the fundamental materials science to make the metallurgical sector more sustainable has been less addressed. This may be attributed to the fact that the field of sustainable metals describes a global challenge, but not yet a homogeneous research field. However, the sheer magnitude of this challenge and its huge environmental effects, caused by more than 2 billion tonnes of metals produced every year, make its sustainability an essential research topic not only from a technological point of view but also from a basic materials research perspective. Therefore, this paper aims to identify and discuss the most pressing scientific bottleneck questions and key mechanisms, considering metal synthesis from primary (minerals), secondary (scrap), and tertiary (re-mined) sources as well as the energy-intensive downstream processing. Focus is placed on materials science aspects, particularly on those that help reduce CO2 emissions, and less on process engineering or economy. The paper does not describe the devastating influence of metal-related greenhouse gas emissions on climate, but scientific approaches how to solve this problem, through research that can render metallurgy fossil-free. The content is considering only direct measures to metallurgical sustainability (production) and not indirect measures that materials leverage through their properties (strength, weight, longevity, functionality).
... 3 For aluminum, the remelting process adds ≈5% to the initial energy used to produce the primary aluminum, leading to an energy saving of circa 95%. 4 There are a number of further environmental and social benefits from increased PCS content in aluminum. 5,6 Both availability and demand of PCS scrap, e.g. in architectural applications, is bound to increase in the near future. 7 Certain recycling friendly alloys can be manufactured without property loss compared to primary based alloys by adjusted composition windows. ...
... 48 Post mortem characterization.-Mass loss measurements were done by immersion of samples for different periods of time (5,15,45, 135, 405 s) in an aqueous 2.5 M NaOH solution at 60°C. For all the samples a fresh solution was used and all the specimens were weighed before and after the exposure to the alkaline environment and the mass loss was normalised by the sample area. ...
Alkaline etching is a common pretreatment for aluminium surfaces. Etching behaviour was compared between an alloy based on post-consumer scrap (PCS) and several model alloys of rolled AA3005 and extruded AA6060 with systematically varied amounts of Mn, Cu, and Ni. Analysis of concentrations of alloy elements in the etching solution by inductively coupled plasma mass spectrometry (ICP-MS) shows that significant fractions of the investigated elements Cu, Fe, Mg, Mn, Ni, and Zn dissolve. Surface analysis of samples in different stages of the etching process show (i) an increase in oxide layer thickness with etching time, (ii) an enrichment of important alloy elements and impurities (Cr, Cu, Fe, Mg, Mn, Si) near the metal/oxide interface, and (iii) the deposition of Mg, Fe, Si-containing aluminium hydroxide on the surface. A comparison with open circuit potential measurements and time-resolved electrochemical polarisation resistance measurements enables a detailed analysis of the etching mechanism. The aluminium dissolution rate during etching is limited by the transport of species through the oxide precursor layer, making it potential-independent. Differences in etching rates between different alloy classes, evidenced by mass loss measurements, are related to differences in the cathodic or anodic reaction mechanisms (hydrogen evolution or metal dissolution) during etching.
... These losses are a result of oxides and dross formation, quality losses due to downgraded material and dilution by adding new virgin material to the mix. For closed-loop recycling the latter two does not occur [38]. ...
... To handle alloys with for example complex or high alloying content it is also crucial that the by-products can be utilized [26]. As an alternative Paraskevas et al. [38] shows in their study that there are considerable environmental gains to reduce quality losses and dilution losses by proper selection and utilization of scrap. When there is a need to add material to reach desired material mix the scrap utilization can increase and the need for primarily material decrease by using the composition of available scrap to gain the correct material characteristics. ...
Recycling is an important area to improve to reduce negative impact on the environment. With increased material recovery, less virgin materials are needed to provide the same benefits for the society. Aluminium is an important metal in the efforts to reduce negative climate impact. Demand for wrought aluminium will heavily increase with electrification of vehicles. However, with today’s recycling, contamination of aluminium alloys results in significant losses where wrought aluminium products are downcycled to cast aluminium with lower value and performance. This paper review the state of the art of aluminium recycling and investigate the current knowledge on the recyclability of current important aluminium alloys and their alloying elements. Future implementations and research are explored to find possible road maps for a sustainable circular economy of aluminium products. The findings indicate that closed-loop recycling trough better developed sorting and separation processes are one of the primary improvement directions. Also, improve utilization of the alloys and their alloying elements in the making of new aluminium alloys.
... 42 The availability of postconsumer scrap could increase to the point that it exceeds the demand for casting alloys, making a surplus of EOL scrap likely. 20,54,55 If advanced sorting and recycling processes were developed or new applications for mixed scrap were found, 9,56 this scrap could also be used in the remelters. For this purpose, we used the parameter "advanced sorting and recycling technologies". ...
Low-carbon technologies are essential for the aluminum industry to meet its climate targets despite increasing demand. However, the penetration of these technologies is often delayed due to the long lifetimes of the industrial assets currently in use. Existing models and scenarios for the aluminum sector omit this inertia and therefore potentially overestimate the realistic mitigation potential. Here, we introduce a technology-explicit dynamic material flow model for the global primary (smelters) and secondary (melting furnaces) aluminum production capacities. In business-as-usual scenarios, we project emissions from smelters and melting furnaces to rise from 710 Mt CO2-eq./a in 2020 to 920–1400 Mt CO2-eq./a in 2050. Rapid implementation of inert anodes in smelters can reduce emissions by 14% by 2050. However, a limitation of emissions compatible with a 2 °C scenario requires combined action: (1) an improvement of collection and recycling systems to absorb all the available postconsumer scrap, (2) a fast and wide deployment of low-carbon technologies, and (3) a rapid transition to low-carbon electricity sources. These measures need to be implemented even faster in scenarios with a stronger increase in aluminum demand. Lock-in effects are likely: building new capacity using conventional technologies will compromise climate mitigation efforts and would require premature retirement of industrial assets.
... Aluminum and polypropylene are intrinsically associated with significant environmental impacts, as highlighted by Paraskevas et al. (2015), underlining the urgent need to identify more sustainable alternatives. This need is further amplified by rigorous European regulations, which, by promoting the transition from a linear to a circular model (Bucknall, 2020), aim to reduce both the quantity of waste generated and the exploitation of virgin resources. ...
The following study arises from the need to replace aluminum and polypropylene, from fossil and non-renewable sources, with innovative materials to produce coffee capsules. The analysis was carried out using Life Cycle Assessment (LCA) and Multi Criteria Decision Analysis (MCDA). In the comparison were considered different materials: aluminum capsules, polypropylene, biocompostable plastic in an industrial environment (industrial compost) and biocompostable plastic in a domestic environment (home compost). The results indicate that, for current disposal, biocompostable plastic capsules, particularly those suitable for domestic compost, have lower environmental impacts. These results are also confirmed for the 10-year disposal scenario. Polypropylene capsules demonstrate greater environmental sustainability when considering a recovery rate of 100 % of the raw material. The MCDA analysis confirms that, at the moment, bioplastics represent the solution with the least environmental impact. However, this advantage is reduced if the capsules are made of aluminum and polypropylene using exclusively fully recycled raw material. Furthermore, it appears that the recycling of fossil materials is a viable alternative to bioplastics. It should be noted, however, that polypropylene can be recycled up to three times, unlike aluminum which can be recycled an indefinite number of times.
... Numerous machine learning techniques, such as classification and regression trees, support vector machines, random forests, Naive Bayes, adaptive neuro-fuzzy inference systems, decision trees, genetic algorithm rule-set production, and quick unbiased efficient statistical trees, have been utilized by researchers to investigate environmental hazards in recent decades (Azzaoui et al. 2019a, b;Liu et al. 2016;Costache et al. 2020;Mirzaei et al. 2020;Darabi et al. 2019;Hong et al. 2018;Chen et al. 2017;Yan et al. 2020;Lee et al. 2017;Rahmati et al. 2019;Hosseini et al. 2020;Eini et al. 2020;Chaki et al. 2022;Onyelowe et al. 2023). These machine learning prediction models have been applied in various fields, including sand dune encroachment, groundwater mapping, landslide prediction, soil and gully erosion, air pollution, ecology, land use, and remote sensing studies (Al-Zubaidi et al. 2022;Khan et al. 2022;Sahar et al. 2021;Baeza and Corominas 2001;Dai and Lee 2001;Mateo et al. 2012;Nourani et al. 2014;Paraskevas et al. 2015;Eker et al. 2015;Ramos et al. 2015;Naghibi et al. 2016;Zabihi et al. 2018;Golkarian et al. 2018;Rajaee et al. 2019;Sameen et al. 2019;and Kim et al. 2019). In particular, machine learning approaches have been utilized to analyze data collected from sand dune movements to identify patterns and make predictions about future movement, which can aid in comprehending the dynamics of dune movement. ...
Accurate mapping plays a crucial role in the management of natural hazards, particularly in the monitoring of sand dune movement. In this research, we focused on modeling sand dune encroachment in a specific study area situated between latitudes 25° 26’ 30” N and 27° 49’ N, and longitudes 27° 28’ E and 31° 08’ E, located in the central Western Desert of Egypt. To accomplish this, we employed advanced machine learning techniques, such as linear support vector machines (SVM), and integrated machine learning algorithms with spatial data types using GIS and R software. To identify dune accumulations from various multispectral sensors, we proposed a novel index called the Drifting Sand Index (DSI). The effectiveness of the DSI was demonstrated, highlighting its significant potential for mapping and monitoring dunes in the study area. Through the utilization of different data sources and field surveys, we identified approximately 150 sand dune locations in the study area. For the sand dune encroachment modeling, we generated nine variables, including slope, aspect, altitude, lithology, distance to roads, normalized difference vegetation index (NDVI), land use/land cover (LULC), wind speed, and direction and soil properties. The results obtained from the DSI indicated that the movement of dunes in the study area ranged approximately 4.9 m/yr towards the southeast. By employing the SVM model, we were able to produce a comprehensive map illustrating the risks associated with sand dune encroachment. The sand dunes hazard zones were classified into five categories: very low (47.1 km²), low (11285.7 km²), medium (356.8 km²), high (9519.1 km²), and very high-risk (16552.1 km²) zones. The area under curve (AUC) approach has been applied to evaluate, validate, and compare the SVM model performance. The results indicated that AUC values for nine MLTs range from 95.1%. The RMSE value for the applied MLT was determined to be 0.391, indicating a significant agreement between the model and reality. .The information derived from this study will contribute to the achievement of sustainable development goals and the preservation of the environment.
... An element Si, combined with Mg, plays an important role in the formation of Mg2Si or β phase, which is the main hardening precipitate in the alloy [8]. As a result, lower grades and qualities of recycled aluminum scrap will be retrieved due to the presence of impurities [12]. On the other hand, the demand for wrought aluminum alloy products increases for low impurities and a good combination of mechanical properties. ...
An as-cast aluminum billet with a diameter of 100 mm has been successfully prepared from aluminum scrap by using direct chill (DC) casting method. This study aims to investigate the microstructure and mechanical properties of such as-cast billets. Four locations along a cross-section of the as-cast billet radius were evaluated. The results show that the structures of the as-cast billet are a thin layer of coarse columnar grains at the solidified shell, feathery grains at the half radius of the billet, and coarse equiaxed grains at the billet center. The grain size tends to decrease from the center to the surface of the as-cast billet. The ultimate tensile strength (UTS) and the hardness values obtained from this research slightly increase from the center to the surface of the as-cast billet. The distribution of Mg, Fe, and Si elements over the cross-section of the as-cast billet is inhomogeneous. The segregation analysis shows that Si has negative segregation towards the surface, positive segregation at the middle, and negative segregation at the center of the as-cast billet. On the other hand, the Mg element is distributed uniformly in small quantities in the cross-section of the as-cast billet.
... Aluminium recycling provides an opportunity for reduction of greenhouse gas emissions since it reduces the need for primary aluminium production, which has been identified in critical lifecycle assessment by Paraskeva et al. [34] as an energy-and carbon-intensive process. Al alloys are used in an extremely wide range of applications and industries, including aerospace, automotive, construction, and beverage packaging, all of which generates a large quantity of waste. ...
Additive manufacturing has revolutionised the production of functional components and assemblies, offering a high degree of manufacturing flexibility. This review explores the latest advancements in additive manufacturing, focusing on its fusion-based and solid-state based technologies, and highlights the use of recycled aluminium as feedstock in these processes. The advantages and limitations of incorporating recycled materials are thoroughly analysed, considering factors such as material properties, sustainability, and process acceptance. While up to 14.4 kg CO2 per kg of aluminium is released during primary aluminium ingot production, solid-state based additive manufacturing, which is tolerant of feedstock contamination, can directly recycle aluminium. Meanwhile, fusion based additive manufacturing can readily utilise recycling pathways such as maintaining grade, upcycling, and downcycling, as well as powder reuse, providing opportunities for significant emissions reduction. The examination of feedstock manufacturing in this review, such as wire for WAAM and powder for PBF, indicates that this step indirectly increases the resource consumption of additive manufacturing. Finally, the alignment of aluminium recycling and additive manufacturing with Circular Economy principles and the UN's sustainable development goals are addressed, highlighting contributions to SDGs 3, 9, and 12.
... Aluminium is a 100% recyclable material, and different studies have shown the advantages of secondary aluminium production through LCA and its lesser environmental impacts (Damgaard et al. 2009;Hong et al. 2010;Ding et al. 2012;Paraskevas et al. 2015;Zare and Izadikhah 2017). Nonetheless, the long lifespan of aluminium ensures the continuity of primary aluminium demand in the future. ...
Purpose
Aluminium industry emits around 1–2% of the world’s total greenhouse gas emissions. Up to one-third of those are linked to the thermal energy consumed during its initial process: the alumina refining (Bayer process). Previous studies consider the Bayer process a single stage despite its being made of several reaction stages. This work presents a disaggregated energy analysis of the Bayer process that facilitates to find relationships between the main variables in regular alumina production and the environmental impacts.
Methods
Two different thermodynamic simulations of the Bayer process were carried out using Aspen V11 software. The results of these simulations were validated with referenced data, and afterwards, they were used to perform a life cycle assessment. ISO 14040 and 14,044 standards were followed during the analysis. LCA was implemented on SimaPro 9.0, and ReCiPe 2016 Midpoint (H) method was used to calculate environmental impacts. The influence of bauxite mineral form, type of fuel (energy input), and the distance from the mine to the plant was analysed throughout the study.
Results and discussion
As expected, the type of fuel was revealed as the most crucial factor in the environmental impact of alumina production, with potential savings of up to 75.5% of CO2-equivalent emissions. Nonetheless, the tendency is diverse for other indicators, such as marine eutrophication or terrestrial acidification. On the other hand, while bauxite transportation always has the same impact on the different environmental indicators, bauxite mineral form affects differently depending on the fuel, causing variations in the CO2-eq emissions from 7.7 to 51.3%.
Conclusions
Results indicated that the electrification of heat-demanding processes and the use of renewable power is the most effective approach for reducing environmental impacts. This strategy, however, must be considered in combination with others, as interdependent effects exist on the type of mineral used. These results provide strong evidence of the potential for environmentally friendly strategies in the metal industry, including new processes, alternative fuels, or mineral switching to promote more sustainable aluminium production.
... The focus of the study is on aluminum recycling life cycle assessment using the ReCipe impact assessment method. The reduction of energy requirement and material losses in aluminum production from the secondary resources will reduce the environmental impact per mass of produced alloy [19]. ...
A clear understanding of the major environmental impacts of steelmaking from scraps, as well as potential solutions involving a circular economy paradigm, is essential. This study is conducted to pave the way for using life cycle assessment (LCA) to have sustainable development and effective resource management by evaluating the environmental impacts of the steel rebar manufacturing process using secondary resources. This is a cradle-to-gate LCA that includes scrap collection and sorting, transportation, melting, continuous casting, billet reheating, and reinforcing bar rolling. Inventory data is acquired as primary data from the factory and secondary data from the SIMAPRO-integrated eco-event database. All of the analyses in this LCA were conducted using the Recipe midpoint and endpoint impact assessment techniques taking one-ton reinforcing bar production as reference flow. The global warming potential created during the manufacturing process is recorded as 467 kgCO 2 eq in the environmental impact report. By moving hot billet directly to the rolling mill and using an efficient transportation system, the environmental impact of global warming potential can be reduced nearly 50%.
... In the recycling process, in which open-loop recycling is typical, a substantial amount of highpurity aluminum scrap is degraded as the casting aluminum alloy. This process would increase the secondary casting aluminum ratio (Paraskevas et al., 2015). Therefore, the middle-and high-ratio scenarios of secondary casting aluminum are designated as that their ratios would increase to 40% and 45% in 2030, respectively. ...
... Paraskevas et al. [163] proposed an environmental modelling approach for assessing the sustainability of aluminum recycling. Their study developed a LCA tool to evaluate the environmental impacts of different recycling scenarios. ...
... Most commercial wrought and cast Al alloys have Fe impurity around 0.2 wt.%, which increases further to a level of 0.3-0.8 wt.% or higher during recycling (Belov, Aksenov, and Eskin 2002), and its removal from Al melts is energy intensive and severely limited for thermodynamic reasons (Gaustad, Olivetti, and Kirchain 2012;Nakajima et al. 2010;Paraskevas et al. 2015). To diminish the detrimental effects of Fe, several different metallurgical solutions were used, i.e. (1) to avoid the formation of low symmetry Al-Fe or Al-Fe-Si compounds by lowering Fe levels as low as economically possible; ...
Achieving superior mechanical properties of Al alloys with high content of Fe impurities is very challenging. Here, a feasible method was applied to accommodate high Fe content (∼2.2 wt.%) and obtain superior strength in an Al–5Mg2Si–2Mg–2Fe alloy by using additive manufacturing. Heterogeneous distribution of Fe, including a high number density of α-Al12(Fe,Mn)3Si particles distributed at the melting pool boundary and excessive Fe segregated along the cell boundaries that divided by Mg2Si eutectics, was verified as the beneficial factor for the alloy design and strength enhancement. In addition to the heterogeneous grains that contain fine cells, the interactions between dislocations and coherent Mg2Si eutectics and the α-Al12(Fe,Mn)3Si particles played an important role in improving the mechanical properties. This work represents a breakthrough in recycling high-strength Al alloys with extremely high Fe doping for green industrial application through additive manufacturing.
... Therefore, mixed post-consumer scrap that contains both Wrought and Cast alloys is typically only suitable for the 36 production of secondary Cast alloys, or it must be diluted with high amounts of primary aluminum for the production 37 of secondary Wrought alloys (Paraskevas et al., 2015). A Deep Learning approach was developed by (Díaz-Romero 38 et al., 2022a) to classify aluminum post-consumer scrap into three commercially interesting output fractions. ...
Integrating multi-sensor systems to sort and monitor complex waste streams is one of the most recent innovations in the recycling industry. The complementary strengths of Laser-Induced Breakdown Spectroscopy (LIBS) and computer vision systems offer a novel multi-sensor solution for the complex task of sorting aluminum (Al) post-consumer scrap into alloy groups. This study presents two novel methods for fusing RGB and Depth images with LIBS using Deep Learning models. The first method is a single-output model that combines LIBS UNET and two DenseNets in a late fusion framework. The second method is a multiple-output model that uses the structure of the single-output model to enhance learning and avoid overfitting. In particular, the network has two outputs that enable the regularization of the individual sensors. A data set of 773 aluminum scrap pieces was created with two sets of ground truth-values, corresponding to the two envisaged sorting tasks, to train and evaluate the developed models. The first sorting task is separating Cast and Wrought (C&W) aluminum. The second is the division of the post-consumer aluminum scrap into three commercially interesting fractions. The single-output model performs best for separating C&W, with a Precision, Recall, and F1-score of 99%. The multiple-output model performs best for classifying the three selected commercial fractions, with a Precision, Recall, and F-score of 86%, 83%, and 84%, respectively. The presented data fusion method for LIBS and computer vision images encompasses the great potential for sorting post-consumer aluminum scrap. By sorting mixed post-consumer aluminum scrap in alloy groups, more wrought-to-wrought recycling can occur, and quality losses can be mitigated during recycling.
... [9]. This approach is suboptimal since it is characterised by significant quality losses [10]. The wrought 35 ...
... Al alloys are classified in two major groups, wrought and cast. Since the percentage of contaminants leads to lower ability to deformation, wrought alloys have much lower alloying elements share, on the other hand, as cast alloys do not need high deformability, have higher content of alloying elements [5]. Since most cast parts need further surface treatment, the addition of silicon gives also to these a higher machinability. ...
... It is known to be harmful to both animals and humans due to their release of smoke and toxic gases such as carbon monoxide and nitric oxide [62]. The use of bio-based epoxy resin were found to be more environmentally friendly than petroleum based ones [63][64][65]. As for aluminium, regardless of its primary or secondary (recycled) production, the majority of the impact comes from undertaking electrolysis, and the associated electricity demand in this process. ...
Kesterite-based structures are being extensively studied for solar module productions due to their earth abundant and nontoxic nature, high absorption coefficient, and a wide variety of scalable deposition methods. Kesterites are mostly manufactured using thin-film technology. However, in the last decade, the monograin approach has gained further attention, providing a third alternative to mono-crystalline wafer and thin film methods. This is due to its high throughput, low-cost deposition techniques, flexibility, and light weight. Despite the technical advancements in the monograin technology, their environmental impacts have not been studied in the literature. This paper, for the first time, presents a cradle to gate environmental life cycle assessment of CZTS monograin module production. The analysis is designed to identify the environmental hotspots associated with materials, energy usage, and manufacturing processes. The results were compared to CZTS thin-film and the commercially available CIGS technologies. The analyses suggested that the front contact accounted for the majority of impact in all categories due to the use of silver. The normalisation results showed that the marine aquatic ecotoxicity impact category dominated the overall impact results. A comparison of CZTS monograin and thin film production demonstrated that monograin outperformed the thin film technology when silver was substituted with alternative materials and was proximate to CIGS even considering their higher achieved efficiency. The analysis presents considerable environmental benefits associated with the monograin technology. Further savings in emissions could be achieved with improved conversion efficiency and usage of renewable energy sources in the manufacturing stages.
... Therefore, mixed post-consumer scrap that contains both Wrought and Cast alloys is typically only suitable for the 36 production of secondary Cast alloys, or it must be diluted with high amounts of primary aluminum for the production 37 of secondary Wrought alloys (Paraskevas et al., 2015). A Deep Learning approach was developed by (Díaz-Romero 38 et al., 2022a) to classify aluminum post-consumer scrap into three commercially interesting output fractions. ...
Integrating multi-sensor systems to sort and monitor complex waste streams is one of the most recent innovations in the recycling industry. The complementary strengths of Laser-Induced Breakdown Spectroscopy (LIBS) and computer vision systems offer a novel multi-sensor solution for the complex task of sorting aluminum (Al) post-consumer scrap into alloy groups. This study presents two novel methods for fusing RGB and Depth images with LIBS using Deep Learning models. The first method is a single-output model that combines LIBS UNET and two DenseNets in a late fusion framework. The second method is a multiple-output model that uses the structure of the single-output model to enhance learning and avoid overfitting. In particular, the network has two outputs that enable the regularization of the individual sensors. A data set of 773 aluminum scrap pieces was created with two sets of ground truth-values, corresponding to the two envisaged sorting tasks, to train and evaluate the developed models. The first sorting task is separating Cast and Wrought (C&W) aluminum. The second is the division of the post-consumer aluminum scrap into three commercially interesting fractions. The single-output model performs best for separating C&W, with a Precision, Recall, and F1-score of 99%. The multiple-output model performs best for classifying the three selected commercial fractions, with a Precision, Recall, and F-score of 86%, 83%, and 84%, respectively. The presented data fusion method for LIBS and computer vision images encompasses great potential for sorting post-consumer aluminum scrap. By sorting mixed post-consumer aluminum scrap in alloy groups, more wrought-to-wrought recycling can occur, and quality losses can be mitigated during recycling
... As far as lightweight aluminum alloys are concerned, the CR approach is still energy-intensive and demonstrates low energy efficiency [23,24]. In every remelting process, metal losses occur in slag mixing and metal oxidation [25,26]. By replacing metal permanent losses with primary aluminum, the embodied energy of recycled aluminum can increase by up to 30 megajoules/kg [15,27]. ...
The current practice in aluminum recycling plants is to change the waste into molten metal through the conventional recycling (CR) manufacturing process. However, the CR technique is so energy-intensive that it also poses an indirect threat to the environment. This paper presents a study on meltless direct recycling hot press forging (DR-HPF) as an alternative sustainable approach that has fewer steps with low energy consumption, as well as preventing the generation of new waste. A laboratory experiment was conducted to study the mechanical properties and surface integrity of AA7075 aluminum alloy by employing a hot press forging (HPF) process under different temperatures (380, 430, and 480 °C) and holding times (0, 60, and 120 min). It was found that as the parameter increased, there was a positive increase in ultimate tensile strength (UTS), elongation to failure (ETF), density, and microhardness. The recycled chips exhibit the best mechanical properties at the highest parameters (480 °C and 120 min), whereas the UTS = 245.62 MPa and ETF = 6.91%, while surface integrity shows that the calculated microhardness and density are 69.02 HV and 2.795 g/cm3, respectively. The UTS result shows that the highest parameters of 480 °C and 120 min are comparable with the Aerospace Specification Metals (ASM) Aluminum AA7075-O standard. This study is a guide for machinists and the manufacturing industry to increase industry sustainability, to preserve the earth for future generations.
... It is known to be harmful to both animals and humans due to their release of smoke and toxic gases such as carbon monoxide and nitric oxide [62]. The use of bio-based epoxy resin were found to be more environmentally friendly than petroleum based ones [63][64][65]. As for aluminium, regardless of its primary or secondary (recycled) production, the majority of the impact comes from undertaking electrolysis, and the associated electricity demand in this process. ...
... This metric is defined as the primary evaluation metric for classification, creating a better measure for evaluating the number of misclassifications in imbalanced samples. Precision = TP TP + FP (5) Recall = TP TP + FN (6) F1-score = 2⋅ ...
In the recycling industry, the use of deep spectral convolutional networks for the purpose of material classification and composition estimation is still limited, despite the great opportunities of these techniques. In this study, the use of Laser-Induced Breakdown Spectroscopy (LIBS), Machine Learning (ML), and Deep Learning (DL) for the three-way sorting of Aluminum (Al) is proposed. Two sample sets of Al scrap are used: one containing 733 pieces for pre-training and validation with a ground truth of X-Ray Fluorescence (XRF), and the second containing 210 pieces for testing for unknown compositions. The proposed method comprises a denoising system combined with a method that extracts 145 features from the raw LIBS spectra. Further, three ML algorithms are assessed to identify the best-performing one to classify unknown pieces of aluminum post-consumer scrap into three commercially interesting output classes. The classified pieces are weighed, melted, and analyzed using spark analysis. Finally, to optimize the best-performing ML system, three state-of-the-art denoising and three feature extraction networks are pre-trained for learning the baseline correction and the proposed feature extraction. Transfer Learning from the six pre-trained networks is applied to create and evaluate 24 end-to-end DL models to classify Al in real-time from >200 spectra simultaneously. The end-to-end DL scheme shows the advantages of learning and denoising the spectra, allowing the transfer of traditional spectral analysis knowledge and the proposed feature extraction into DL, where the network learns from the entire spectrum. The best results for ML and DL were obtained with Random Forest processing one spectrum in 150 ms and BPNN+GHOSTNET(Fine-tuning) processing 200 spectra in 9 ms, which achieved 0.80 Precision, 0.81 Recall, 0.80 F1-score, and 0.80 Precision, 0.79 Recall, 0.79 F1-score, respectively.
... The inclusion of recycled and secondary materials was explored by several research groups [61][62][63][64][65][66]. The incorporation of aluminum shavings from machining chips within a foundry plant was carried out, and the efficiency of the recycling depended on the conditioning of the material, melting technique, and treatment methodology of the melted metals. ...
This review aims to carry out a scientific review of the current status of aluminum can recycling processes over the last 15 years, seeking to find sustainable applications for its destination. Thus, the research topics were defined by the identification of the structure of the scientific field of research and the relationship of aluminum recycling, casting processes, and formation of aluminum-based alloys, as well as their applications. Therefore, three topics were studied: the state of the art of aluminum recycling practices; processes being performed and aluminum casting techniques and methods; and the current state of formation of secondary aluminum-based alloys, the alloy elements being used, and their applications after the formation of alloys. Based on the above three topics, the research topics include (A) aluminum recycling, (B) casting processes, and (C) the formation of aluminum-based alloys and their applications. For bibliometric analysis, the software SciMAT was applied. Through the overlaid map and the evolution map, it was possible to detect the temporal evolution of the scientific field in the researched area. Cluster analysis allowed us to identify the motor words. Through the connections network, keywords connected to the motor themes were verified that indicated the connection areas of the research field and the main authors. The simulation models were factors of innovation in the area, as well as the software packages ANSYS and ProCAST. In the area of alloy formation, the liquid metal cleaning analyzer technique was highlighted in the production of high-quality alloys. The important connections to aluminum recycling feasibility are presented in this review.
... Therefore, the production of aluminium, iron and plastic from secondary raw materials is a positive sustainable development option. The process is beneficial from both an economic and environmental point of view [6][7][8][9][10][11]. ...
Aluminium, iron and plastic are materials which are extensively used at both industry and individual levels. However, significant amounts of aluminium, iron and plastic end up in the environment. Specifically, bottle caps made of these materials are often thrown away, with or without bottles, and appear among the common plastic debris entering the world’s oceans and beaches. More than 20 million bottle caps and lids have been identified during beach-cleaning campaigns over the last 30 years. To recover bottle caps from the shores, conventional technologies can be used. In this paper, the physical properties of used metal and plastic bottle caps were examined and related to the settling and rising velocities of the caps, as well as their drag coefficients and hydrodynamic modes in water environments, with respect to gravity separation. The sample contained aluminium, iron, high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP) bottle caps. The findings revealed that the density differences between the bottle caps resulted in the terminal settling velocities of aluminium and iron particles, which were significantly higher than the rising velocities of the plastic caps. The results allowed us to design a flowsheet for bottle cap recovery from beach coasts in order to reduce environmental impact and produce add-on plastic and metal products. Key words: plastic recycling, waste recycling, solid waste separation.
... Consequently, the aluminium is downcycled instead of recycled. Paraskevas et al. show that this downcycling practice and the rising need for high purity aluminium will result in an excess of low purity aluminium for which there is no demand [5]. This excess of aluminium scrap will likely end up to a large extent in landfill and will need to be replaced by new primary aluminium, resulting in additional environmental impact. ...
Due to shifting material use in several sectors, such as the automotive sector, the demand for wrought aluminium alloys is significantly increasing. Because of their low weight and desirable mechanical properties, wrought aluminium alloys find their use in many different applications. However, the primary production of aluminium is extremely energy intensive. Therefore, using secondary aluminium yields major environmental benefits. Hence, in order to avoid degradation of the aluminium quality during recycling, sorting aluminium alloys, based on their alloying elements, is necessary. Today, various non-ferrous metal fractions are either still sorted manually in unhealthy working conditions, resulting in either high labour costs, or the export of this waste stream to countries with a lower labour cost. With the emergence of novel spectrometric techniques, such as laser-induced breakdown spectrometry (LIBS) and deep learning computer vision techniques, the technical feasibility of classifying different aluminium alloys has been demonstrated. Therefore, the techno-economic viability of a robotic sorting process, that could be combined with such advanced classification systems, is presented. This study presents the development and evaluation of a robotic sorting system consisting of; a vision system, a conveyor, a SCARA robot and a pneumatic gripper. The vision system recognises the dimensions and positions of the objects on the conveyor and communicates with an innovative sequence planning algorithm. The use of experimental data enables to obtain realistic insights in the sorting efficiencies that can be obtained. The initial economic analysis illustrates the substantial potential of the proposed robotic sorting approach. To overcome saturation of the conveyor belt, two of the proposed systems are assumed to be capable of sorting 20.000 tons of aluminium annually each equipped with 6 robots creating a total added revenue up to 1,95 million euro per year.
... Recycling of end-of-life aluminium alloys is commonly by remelting of mixed scraps, which implies that geochemically scarce elements tend to lose functionality after remelting (Paraskevas et al. 2015;Reijnders 2018). The dissipative loss for aluminium is about one third of the amount extracted . ...
Substitutability of natural capital by human-made capital would seem to be limited. When human-made capital substitutes natural capital, there are currently commonly long-lasting negative impacts of such substitutions on constituents of natural capital. Long-lasting negative impacts on natural capital can be considered at variance with justice between the generations. In view thereof, there is a case to define (environmental) sustainability as keeping natural capital intact for transferral to future generations. A major problem for such conservation regards natural resources generated by geological processes (virtually non-renewable resources), especially regarding geochemically scarce elements. Substitution of virtually non-renewable resources by generating equal amounts of renewables has been proposed as a way to conserve natural capital. However, renewables substituting for fossil carbon compounds are currently associated with negative impacts on constituents of natural capital to be transferred to future generations. The same holds for the substitution of widely used geochemically scarce virtually non-renewable copper by abundant resources generated by geological processes. Though current negative impacts of substitutions on natural capital can be substantially reduced, their elimination seems beyond the scope of what can be achieved in the near future. The less strict “safe operating space for humanity”, which has been used in “absolute sustainability assessments” is, however, not a proper alternative to keeping natural capital intact for transferral to future generations.
The European Green Deal has the ambition to enhance recycling practices to better close material loops. However, in the recycling industry of today it is common practice to shred products to liberate the different materials that the product contains. This, typically results in a broad range of object sizes and mixed waste streams, which increases the complexity for the robotic sorting of these waste streams. Nonetheless, to meet up with today's number of different material types and quality standards, the potential and demand for robust robotic sorting increases. While the robotic (sorting) industry is quickly evolving, currently used robotic grippers are often not designed to cope with the large variation in material types and shapes encountered in shredded material streams. Therefore, a novel High Airflow Vertical COnveying (HAVCO) gripping system is developed in the presented research. This HAVCO gripper is validated in an aluminum sorting use case, which demonstrated significant opportunities for the sorting of random shaped, small and light waste fractions, which typically pose challenges for the state-of-the-art gripper technologies. The main advantage of the presented HAVCO gripper is that it does not require challenging gripping pose estimation and proofs to be able to perform a robotic pick in less than 0.4 seconds, which is up to 3 times faster than commonly used parallel grippers while achieving high picking success rates of approximately 93%.
One of the most promising innovation strategies for sorting and recycling post-consumer aluminium scrap is using quantitative Laser-Induced Breakdown Spectroscopy (LIBS) analysis. However, existing methods to estimate alloying element concentrations based on LIBS spectra, such as linear univariate regression and Machine Learning models, are still too limited in their performance to achieve the accuracy demanded by the industry. Therefore, this study presents novel Deep Learning approaches and compares their performance to those of traditional univariate regression and Machine Learning methods in terms of RMSE, MAE, and R2 value. For this evaluation, two sample sets of aluminium pieces are used: one containing 27 certified aluminium reference samples and the second containing 733 post-consumer scrap pieces for which the ground truth concentrations are determined by X-Ray Fluorescence (XRF).
Adopting multiple loss functions, one for each element has proven its significant value for the regression performance. It improves the results for all performance metrics in the Scrap Sample set, and the same is true for the Reference Sample set, except for the coefficient of determination of Fe, Mn and Mg. In addition, the proposed methodology considers the learning prioritisation problem to prevent that learning the concentration of the base element is prioritised over the alloying elements. Although the effect of excluding the base alloy aluminium from the learning is small and not always positive for the performance, demonstrating this effect is also considered valuable. Since the average RMSE on the prediction is just 0.02 wt.% for Al and Si, and not more than 0.01 wt.% for Fe, Cu, Mn, Mg, and Zn, the best performing Deep Learning model shows promise for the future of LIBS in metal sorting applications.
Metal recycling industry offers a pathway for promoting resource reuse and waste mitigation. Particularly, aluminum and magnesium alloys, which are handled efficiently, have been adopted in various sectors and recycled. Despite the advantages of these materials, recycling these products introduces the risk of fires and explosions during the recycling process owing to their physical and chemical properties. Aluminum and magnesium are notable water-reactive and combustible metals. Thus, with the internal and external hazards, such as water and chemical reactions, the aluminum and magnesium in the recycling plants can ignite violently, causing disastrous consequences. Thus, this study aims to draw lessons to improve the risk and safety management capacity of metal recycling plants in South Korea by investigating four cases of fire and explosion in magnesium and aluminum recycling plants. The lessons identified are as follows: set up regulations/guidelines to undertake measures based on the hazardous materials from the recycling process and possible reactions; consider the probability of extreme events caused by external hazards based on risk analysis and assessment; prepare safety and preventive equipment considering the specific environmental conditions of the metal recycling plants; plan resources required for appropriate response; arrange safeguards to avoid possible damage; and finally, discern the mechanism of aluminum and magnesium fire.
In this paper, the deformation behavior of Al-4.5Cu alloys containing the Cu clusters under high temperature is systematically investigated by molecular dynamics. Reduced nucleation stress of dislocation is driven by increasing strain rate and temperature, which triggers the stress–strain curves of Al-4.5Cu alloy showing gradually elastic-plastic stage and elastic-plastic-viscous stage. Besides, the defect surface in Al-4.5Cu alloy do not have enough time to move along and gather due to the increase of strain rate, which make the distribution of defect surface mainly divide into three types: the plane distribution which is at 45° angle to the direction of tensile, the stratification distribution which is perpendicular to the direction of tensile and the distribution of honeycomb, respectively. The microscopic fracture morphology for Al-4.5Cu alloy are changed from pure shear fracture to microporous aggregate fracture due to three type of defect surface.
The booming development of the aluminum industry has greatly contributed to China's economic development, but it also imposed a burden on the environment. Recent technological development has emerged various methods for aluminum production to improve production efficiency and reduce environmental impacts, while reducing energy intensity in traditional production practices can also lower emissions and remain low production costs. However, which approach that performs better in achieving economic benefits and reducing environmental impacts is unclear. This study analyzed six major aluminum production methods based on alumina production process and energy mix. Environmental parameters were derived based on life cycle assessment, and economic cost parameters were formed by building an economic benefits model. This paper then analyzed the potential of achieving economic benefits and environmental impacts reduction for each method using life cycle assessment and principal component analysis. Finally, the greenhouse gas emissions from the aluminum industry in 2030 based on scenario analysis was analyzed. Results showed that Bayer process-hydropower method performs the best in reducing environmental impacts and achieving economic benefits, while the sinter process-thermal power method performs the worst. The effect of reducing emissions by changing the energy mix (75%) was more significant than that by changing the alumina production process (up to 10%). Furthermore, the scenario analysis was used to expand the capacity share of the Bayer process-hydropower method with optimal comprehensive benefit increased by 22.2%, the cost of electricity decreased by 313.77 CNY/t-Al, and the global warming potential was reduced by nearly 1/3. Thus, our results reveal the significant benefits of the Chinese government's push to increase the share of clean energy applications in the aluminum industry.
The growing challenges on fuel economy improvement and greenhouse gas emission control have become the driving force for automakers to produce lightweight automobiles. Also, the weight reduction may contribute to superior recyclability and/or vehicle performance (e.g., improved driving economy, braking behaviors, and crashworthiness). One effective strategy is to develop and implement lightweight yet high-performance materials as alternative solutions for conventional automotive materials such as cast iron and steel. Herein, a systematic review of available lightweight materials to produce next-generation automobiles is provided, including light alloys, high-strength steels, composites, and advanced materials in the ongoing research. By investigating the entire life cycle of automotive materials, physical/mechanical properties, characterization, manufacturing techniques, and potential applications of specific lightweight materials are discussed. Both the advantages and drawbacks of the reviewed materials are summarized, yielding the appropriate application scenarios for different lightweight materials. Given the future challenges, on expectations, the development of versatile advanced materials or improvement of the manufacturing/treatment techniques can be rather promising to resolve the possible bottlenecks and, in turn, enables more capable, safer, durable, and environmental-friendly vehicles.
There are several facets of aluminum when it comes to sustainability. While it helps to save fuel due to its low density, producing it from ores is very energy-intensive. Recycling it shifts the balance towards higher sustainability, because the energy needed to melt aluminum from scrap is only about 5% of that consumed in ore reduction. The amount of aluminum available for recycling is estimated to double by 2050. This offers an opportunity to bring the metallurgical sector closer to a circular economy. A challenge is that large amounts of scrap are post-consumer scrap, containing high levels of elemental contamination. This has to be taken into account in more sustainable alloy design strategies. A “green aluminum” trend has already triggered a new trading platform for low-carbon aluminum at the London Metal Exchange (2020). The trend may lead to limits on the use of less-sustainable materials in future products. The shift from primary synthesis (ore reduction) to secondary synthesis (scrap melting) requires to gain better understanding of how multiple scrap-related contaminant elements act on aluminum alloys and how future alloys can be designed upfront to become scrap-compatible and composition-tolerant. The paper therefore discusses the influence of scrap-related impurities on the thermodynamics and kinetics of precipitation reactions and their mechanical and electrochemical effects; impurity effects on precipitation-free zones around grain boundaries; their effects on casting microstructures; and the possibilities presented by adjusting processing parameters and the associated mechanical, functional and chemical properties. The objective is to foster the design and production of aluminum alloys with the highest possible scrap fractions, using even low-quality scrap and scrap types which match only a few target alloys when recycled.
In this study, a novel method using supergravity separation with manganese addition to remove iron for aluminum recovery from scrap aluminum alloy was explored. The effects of separating temperature (T), Mn/Fe mass ratio, and gravity coefficient (G) on iron separation efficiency were evaluated. Increasing the separating temperature improved the Al yield but decreased Fe removal. The higher Mn/Fe mass ratio resulted in a rise in Fe removal but a drop in Al yield, since Mn addition transformed the needle-like β-AlFeSi to compact α-AlSiFeMn phase in aluminum alloy. The gravity coefficient showed no effect on the Fe removal but greatly influenced Al yield. At the optimal conditions of T=670°C, Mn/Fe=1.0, and G=500, the Fe removal and Al yield were well balanced at 60.4% and 82.5%, respectively, and the purity of recovered Al was 94.6wt%. In addition, the Scheil-Gulliver solidification model of the Thermo-Calc software was used to calculate the solidification diagram and solidified phase fraction of scrap Al alloy, and it was found that the addition of Mn altered the solidification path, increased alloy solidification temperature, and promoted the formation of α-AlSiFeMn phase in the melt, which was able to reduce the balanced content of iron in the liquid phase.
The benefit of knowing the exact chemical composition of metal scrap plays a significant role from metallurgical point of view in recycling processes. Thus, the focus of this paper is to identify opportunities for more efficient scrap management, in order to minimize quality loses and primary material consumption during recycling. By moving to compositionally closer recycling loops, higher recycling values by reducing the need for primary metal and alloying elements addition, can be achieved. A Life Cycle Assessment (LCA) was performed, focusing on aluminium scrap, in order to validate, estimate and compare the environmental impact of different recycling options and the effect of scrap separation strategies. Furthermore, a metric to compare the ‘quality’ in terms of recyclability of the various metal flows is proposed.
For the evaluation of the compatibility of materials combinations for metallurgical recycling, a ther-modynamic approach has been applied. This approach led to the construction of a decision tree model for the evaluation of the compatibility of materials combinations, the thermodynamic evaluation of materials combinations (THEMA) model. The technological and economical aspects of recycling were also mentioned, as they introduce additional constraints to the feasibility of the recycling processes. The results were structured in a matrix for materials combinations, the THEMA matrix. The decision tree and matrix are to be used as a decision support tool in product design. The objective is to minimise the recycling losses and contaminations, increasing the resource efficiency of product systems. With lower contamination levels, the recovery and recycling processes would become more profitable, as less energy and resources are required, leading to a win–win situation to the industry and environment. Some application examples are included, using a passenger vehicle as example. The major compatibility problems for the metallurgic recycling of the recovered material streams from end-of-life vehicles (ELVs) were described. From the thermodynamics perspective, special attention is required with the increasing use of lightweight metals, because they are very sensitive to contaminations.
Climate change mitigation in the materials sector faces a twin
challenge: satisfying rapidly rising global demand for materials while
significantly curbing greenhouse-gas emissions. Process efficiency
improvement and recycling can contribute to reducing emissions per
material output; however, long-term material demand and scrap
availability for recycling depend fundamentally on the dynamics of
societies' stocks of products in use, an issue that has been largely
neglected in climate science. Here, we show that aluminium in-use stock
patterns set essential boundary conditions for future emission pathways,
which has significant implications for mitigation priority setting. If
developing countries follow industrialized countries in their aluminium
stock patterns, a 50% emission reduction by 2050 below 2000 levels
cannot be reached even under very optimistic recycling and technology
assumptions. The target can be reached only if future global per-capita
aluminium stocks saturate at a level much lower than that in present
major industrialized countries. As long as global in-use stocks are
growing rapidly, radical new technologies in primary production (for
example, inert anode and carbon capture and storage) have the greatest
impact in emission reduction; however, their window of opportunity is
closing once the stocks begin to saturate and the largest reduction
potential shifts to post-consumer scrap recycling.
Global aluminum consumption has exhibited significant growth in recent years, due to its useful properties. As this will result in a large amount of aluminum accumulation as urban mines, the exploitation of these urban stocks will be an important issue in the future. To examine the recycling potential of urban stocks, a dynamic material flow analysis on aluminum was conducted focusing on Japan, the United States, Europe and China. The concentrations of the alloying elements were also investigated, since carryover of alloying elements during recycling results in off-specification secondary metals and alloys. The recycling of aluminum scrap was optimized from the results of dynamic material flow analysis using multi-material pinch analysis. It was estimated that Japan, the United States, Europe and China have the potential to reduce their primary aluminum consumption to 60%, 65%, 30% and 85% of their present levels, respectively. In 2050, it is estimated that 11400 kt of primary aluminum will be required among the four countries, while 12400 kt of obsolete scrap will not be able to be recycled due to high concentrations of alloying elements.
Aluminum demand in Japan has grown significantly during the last few decades. For most uses, small amounts of other metals are added to the primary aluminum to make harder alloys, which are classified by the nature and concentrations of their alloying elements. Aluminum scraps from end-of-life products, which are used as raw materials for secondary aluminum, are often mixtures of several alloys. Therefore, not only the amount of scrap but also the concentrations of their alloying elements must be taken into account when assessing the maximum recycle rate of aluminum scraps. This paper reports a dynamic substance flow analysis of aluminum and its alloying elements in Japan, focusing on the alloying elements Si, Fe, Cu and Mn. We devised eight categories of aluminum end uses and 16 types of aluminum alloys. The amount of each alloy in each end-use category was estimated from statistical data. We then estimated future quantities of discarded aluminum in each of the eight categories using the population balance model. At the same time, we calculated the concentrations of the alloying elements in each of the end uses. It was estimated that the amount of aluminum recovered in Japan would be about 1800 kt in 2050, which is 2.12 times that recovered in 1990. Calculated concentrations of alloying elements in aluminum scraps showed good correlation with those of the measured data.
Among the various steps of aluminium production from liquid metal, a lot of scrap is generated due to machining operations. Therefore, recycling of aluminium scrap is an interesting subject because of the broad applications of this metal and low efficiency of processes used to recycle metal scrap. In this paper, the recyclability of aluminium alloy AA 336 turnings with different cold compacting pressures and a protective salt flux (NaCl–KCl–KF) has been experimentally studied. Various categories of compacted samples were melted at 750°C in molten aluminium alloy AA 336 and also in the protective salt flux to recover aluminium alloy. In order to understand the amount of recycling of different samples, weight loss measurement was applied. From recyclability stand point it is shown that using protective salt flux is the best route, from the point of view of recyclability. Mechanical properties and chemical analysis of samples were approximately the same as the primary material produced by conventional casting process.
Goal, scope, and background
The aim of this work is to present guidance on the application of ISO 14044 to allocation procedures for metal recycling. As such, graphical patterns of metal recycling and generic “rules” for metal recycling maps are presented. The results are intended to be useful in assessing and validating the suitability of allocation procedures for metal recycling in the context of life cycle assessment (LCA) and assist in the understanding of metals flow patterns in product systems. LCA uses a product-focus; therefore, the perspective here is on recycling metals in post-consumer products. The discussions, analysis, and illustrations in this paper emphasize old (post-consumer) scrap and do not detail flows of new (post-manufacturing, pre-consumer) or prompt (internal) scrap. The work included participation and review from International Council on Mining and Metals, the Nickel Institute, the International Copper Association, the International Zinc Association, worldsteel (formerly International Iron and Steel Institute), and the International Aluminium Institute.
Methods
A survey of generic metal flows was conducted for three major non-ferrous metals—nickel, copper, and zinc. Based on the results of this survey, four metal recycling map models were developed. Implications of these recycling maps for LCA were then considered, and parameters necessary to model metal recycling were presented. Relationships of inherent properties and recycling loops are provided and connected to the allocation procedures in the context of LCA.
Results and discussion
Four metals recycling map models were generated based on a survey and analysis of current metals flow analysis. The utility of the recycling maps is to serve the basis of a structured approach to recycling allocation in life cycle assessment and leveraging the efforts of harmonized recycling metrics.
Conclusions
A consensus on mapping metals is important in order to achieve an accurate understanding and measurement of metals recycling. To this end, consensus mapping presentation of a general allocation approach and identification of harmonized metrics were achieved among representatives of ferrous and non-ferrous metals groups.
Perspectives
For the future, allocation factors based on sound empirical data needs to be developed. Those metrics will empower the various stakeholders—industry, policy makers, non-governmental organizations, and academics to make appropriate decisions based on agreed scientific bases.
The production of aluminum billets—starting from the conversion of bauxite to alumina, the processing of alumina to aluminum, and the final cast product—is studied using a Life Cycle Assessment (LCA) approach. The aluminum supply chain consists of a refinery, a smelter, and a casting plant. In the LCA model, the environmental loads of four different case scenarios were investigated. The scenarios included various approaches employed for improving the environmental performance of the system for the production of 1 ton of aluminum metal.The final impact assessment results for the overall environmental loads of the supply chain showed cumulative decreases of 2.2% and 3.8% for Scenarios 2 and 3, respectively. In Scenario 2, scrap metal was reduced from the casting plant. For Scenario 3, the reduction of scrap metal from casting was accompanied by improvements of both energy efficiency and reject rates at the smelter. A significant cumulative decrease of 32.8% was obtained in Scenario 4, which was mainly due to the reduction of red mud from the refinery by about 50%.
Metals have been essential to human civilisation for many thousands of years. With a broad range of applications they have found their way into virtually every aspect of our daily lives. Their durable and recyclable properties should make them ideal materials for a sustainable economy. But can metals live up to this promise? What are the economic, ecological, and social implications of their increasing use? How can we secure the supply of high-quality metals in the future? Do we need substitutes for scarce or especially toxic metals? We will face many such questions on the path towards sustainable production, trade and use of metals.
This book brings together experts from many fields, with sometimes controversial opinions, to discuss the conditions and limits of a sustainable metals management. The ideas and goals of sustainability are not only explained theoretically, but also applied to various stages of the metal making and trading process. The unique feature of this book is its focus on the practical issues of sustainability and the eminent role that companies play in this respect. Experts take a look at the history of metals and metals processing, analyse the current flows and trends of their use, and try to predict future developments in production and trade. Others assess the ecological and social effects of their production and use, highlight the need for international and inter-organisational thinking, and lay out more efficient ways of pursuing this. All the contributors of this book are united by a common goal: making metals an economically, ecologically, and socially safe choice for the 21st century.
This book is a must-read for anyone interested in the short-term and long-term development of the production, trade and use of metals. It provides a wealth of information on the market, the ecological repercussions of the industry, and the social implications of the production and trade of metals. It is thus a valuable source for decision makers, scientists and campaigners in this field.
We conduct a screening comparison using life cycle assessment (LCA) methodology to model two end-of-life vehicle (ELV) waste management scenarios. The first is the prevalent scrapping process, which entails shredding. The second is manual disassembly, a hypothetical scenario designed to reach the targets in the EU ELV Directive for 2015. The LCA considers three impact categories; climate change, metal depletion, and cumulative energy demand (CED), and identifies the potential lifecycle environmental and resource impacts of new ELV dismantling and recycling processes. Manual disassembly significantly reduces climate change impact and metal depletion, by recycling more polymers and copper and recovering more energy via incineration. The CED is much lower in the manual than the shredding scenario, mainly due to increased recycling and energy recovery, over half the reduction being attributable to polymer recycling and energy recovery. The manual scenario is significantly better than the shredding scenario in terms of environmental and resource impacts, recovering more copper and recycling more polymers. The current shredding scenario does not fulfil the current or future requirements of the ELV Directive. We identify a need to develop new ELV scrapping methods for better resource management and to investigate the value of "new" materials in ELVs, such as rare earth elements.
One strategy for mitigating the effects of rapidly growing global materials consumption is intensified recycling. A key barrier to recycling is the ability to segment or sort constituents within end‐of‐life products. Various sorting technologies hold promise, but each must demonstrate added value to achieve wide‐scale deployment. Potential factors affecting such value include the mix of scrap supply, the nature and mix of finished goods demand, sorting technology performance, and costs. This article examines the use of optimization models to identify economically efficient sorting strategies and their impact on scrap usage. Using this method, this article attempts to identify the conditions that amplify and mute the value of sorting to facilitate recycling.When this method is applied to a case representative of European aluminum secondary production, it is clear that sorting methods can add value in a broad range of conditions. Although better sorting performance (in the form of segmentation efficiency, referred to as recovery rate) correlates positively with cost savings and scrap utilization, it does not always vary monotonically with optimal sorter utilization (i.e., the fraction of scrap sorted rather than unsorted). Furthermore, the case analysis indicates that the value of sorting is more strongly dependent on recovery rate for the more heterogeneous fraction, which, in the case of aluminum, is the cast‐like fraction. Ultimately, sorting increases production flexibility, making a recycler more economically resilient in the face of changing supply and production conditions.
This article discusses the state of the practice, strength, and weakness of life cycle assessments (LCA) for achieving sustainability goals in the aluminum industry. Notable features of the reviewed LCAs include a limited geographical and life cycle scope and differentiated system boundaries, a common practice to use industry-wide inventory data, a polarized debate on allocation of aluminum recycling, and a predominant focus on energy and greenhouse gas emissions environmental metrics. Not surprisingly, the various studies have produced significantly different results, e.g., the greenhouse gas emissions per kilogram primary aluminum production range from 5.92 to 41.10 kg CO2-equivalent and the “break-even point” (the point when the fuel economy benefits of the lighter aluminum vehicle offset added emissions from the production stage) of vehicles lightweighting ranges from 50,000 to 250,000 km. These variations relate not only to real world differences (e.g., temporal and geographical characteristics), but also partly to data uncertainties and methodological choices. Particularly, the recyclability, long lifetime, and environmental benefits in the use phase of aluminum pose great challenges for LCA methodology, especially for the allocation of recycling. The identified uncertainties and deficiencies can serve as an important base for further improvement of subsequent LCA applications in the aluminum industry.
This paper discusses how the recycling of aluminum will change between now and 2050, focusing on the introduction of next-generation vehicles and scrap sorting. To evaluate the recycling potential, aluminum demand and discard in Europe, the United States, Japan, and China are estimated by material flow analysis (MFA). The MFA distinguishes between wrought and cast alloys so that the chemical composition of each flow is taken into account. A comparison of demand with discard is used to evaluate the amounts of primary aluminum required and scrap that cannot be recycled because of a high concentration of alloying elements. The results of these investigations show that the introduction of electric vehicles leads to a decrease in the demand for cast alloys, which generates 6.1 Mt of unrecyclable scrap in 2030. The results also indicate the effectiveness of scrap sorting in the future: if scrap sorting is carried out for end-of-life vehicles, it mitigates the generation of unrecyclable scrap and reduces the primary aluminum requirement by 15–25%.
This paper reports on historical analysis of the steel industry in which crude steel production trends are quantified for the period from 1950 to 2006. On the basis of this analysis, the future production of steel for the world is estimated using regression analysis. The historical analysis shows that the world steel production increased from 187Mt to 1299Mt in that period. In addition, the paper also reports on historical (1950–2006) steel scrap consumption and was compared with crude steel and electric arc furnace (EAF) steel production. Since 1950, scrap consumption by steel industry worldwide has been growing at 12% per annum whereas the EAF share of steel production has been increasing at 66% per annum. Furthermore, since 1987 iron ore prices have increased at 24% per annum whereas scrap prices have grown by 13% per annum.From the analysis on environmental benefits of steel recycling, it was established that there are numerous advantages of scrap utilisation. The major environmental benefits of increased scrap usage comes from the very fact that production of one tonne of steel through the EAF route consumes only 9–12.5GJ/tcs, whereas the BOF steel consumes 28–31GJ/tcs and consequently enormous reduction in CO2 emissions. In addition, a discussion on various alloying elements in steel and their presence in residual concentrations in the scrap on steel properties is also presented. Finally, this paper presents a discussion on policy issues that could enhance the use of scrap in steel-making is also presented.
GRG2 solves nonlinear optimization problems in which the objective and constraint functions can have nonlinearities of any form but should be differentiable. Both single and double precision versions are available for computers of all major vendors.
In this study we introduce the concept of total material requirement (TMR) to quantify the quality of materials from end‐of‐life buildings. The TMRs for the recycling of materials (urban ore TMR [UO‐TMR]) from four types of Japanese buildings ( Japanese traditional wooden structure [ JTWS], wooden frame with walls structure [ WFS ], reinforced‐concrete structure [RCS], and steel‐based structure [SS]) have been estimated and the trade‐off between the increase in function of recycled materials such as steel made from scrap and the additional inputs of energy and materials required to create the increase in function were evaluated. Steel made from scrap, aluminum made from scrap, and road material are assumed to be recycled from steel products, aluminum products, and aggregate and cement concrete in the buildings, respectively. Case study analyses were carried out to determine the effect of recycling only aboveground materials compared to recycling both aboveground and subsurface materials. Also, the effect of varying the recycling rate of wooden demolition debris is determined.
The UO‐TMRs of steel made from scrap range from 4.7 kilograms per kilogram (kg/kg) to 18.2 kg/kg. Urban tailings (unrecycled components) account for the greatest proportion of the UO‐TMR of steel made from scrap, and the next largest contributor is the recycling process. In the case of aluminum made from scrap, the UO‐TMRs range from 22 to 196 kg/kg, with the contribution of urban tailings generally dominant, and the second largest contributor being on‐site demolition and shredding. The UO‐TMRs of recycled road material range from 1.04 to 1.16 kg/kg and are similar for different recycling cases and types of buildings.
Demand for aluminium in final products has increased 30-fold since 1950 to 45 million tonnes per year, with forecasts predicting this exceptional growth to continue so that demand will reach 2 to 3 times today's levels by 2050. Aluminium production uses 3.5% of global electricity and causes 1% of global CO2 emissions, while meeting a 50% cut in emissions by 2050 against growing demand would require at least a 75% reduction in CO2 emissions per tonne of aluminium produced-a challenging prospect. In this paper we trace the global flows of aluminium from liquid metal to final products, revealing for the first time a complete map of the aluminium system and providing a basis for future study of the emissions abatement potential of material efficiency. The resulting Sankey diagram also draws attention to two key issues. Firstly, around half of all liquid aluminium (~39Mt) produced each year never reaches a final product, and a detailed discussion of these high yield losses shows significant opportunities for improvement. Secondly, aluminium recycling, which avoids the high energy costs and emissions of electrolysis, requires signification 'dilution' (~8Mt) and 'cascade' (~6Mt) flows of higher aluminium grades to make up for the shortfall in scrap supply and to obtain the desired alloy mix, increasing the energy required for recycling.
Metals can in theory be infinitely recycled in a closed-loop without any degradation in quality. In reality, however, open-loop recycling is more typical for metal scrap recovered from end-of-life (EoL) products because mixing of different metal species results in scrap quality that no longer matches the originals. Further losses occur when meeting the quality requirement of the target product requires dilution of the secondary material by adding high purity materials. Standard LCA usually does not address these losses. This paper presents a novel approach to quantifying quality- and dilution losses, by means of hybrid input-output analysis. We focus on the losses associated with the recycling of ferrous materials from end-of-life vehicle (ELV) due to the mixing of copper, a typical contaminant in steel recycling. Given the quality of scrap in terms of copper density, the model determines the ratio by which scrap needs to be diluted in an electric arc furnace (EAF), and the amount of demand for EAF steel including those quantities needed for dilution. Application to a high-resolution Japanese IO table supplemented with data on ferrous materials including different grades of scrap indicates that a nationwide avoidance of these losses could result in a significant reduction of CO(2) emissions.
Metals are infinitely recyclable in principle, but in practice, recycling is often inefficient or essentially nonexistent
because of limits imposed by social behavior, product design, recycling technologies, and the thermodynamics of separation.
We review these topics, distinguishing among common, specialty, and precious metals. The most beneficial actions that could
improve recycling rates are increased collection rates of discarded products, improved design for recycling, and the enhanced
deployment of modern recycling methodology. As a global society, we are currently far away from a closed-loop material system.
Much improvement is possible, but limitations of many kinds—not all of them technological—will preclude complete closure of
the materials cycle.
To reach required product qualities with lowest costs, aluminum postconsumer scrap is currently recycled using strategies of downgrading and dilution, due to difficulties in refining. These strategies depend on a continuous and fast growth of the bottom reservoir of the aluminum downgrading cascade, which is formed by secondary castings, mainly used in automotive applications. A dynamic material flow model for the global vehicle system was developed to assess the likelihood, timing, and extent of a potential scrap surplus. The results demonstrate that a continuation of the above-mentioned strategies will lead to a nonrecyclable scrap surplus by around 2018 ± 5 if no additional measures are taken. The surplus could grow to reach a level of 0.4-2 kg/cap/yr in 2050, corresponding to a loss of energy saving potential of 43-240 TWh/yr electricity. Various intervention options for avoiding scrap surplus are discussed. Effective strategies need to include an immediate and rapid penetration of dramatically improved scrap sorting technologies for end-of-life vehicles and other aluminum applications.
An accelerating increase in linear programming applications to industrial problems has made it virtually impossible to keep abreast of them, not only because of their number (and diversity) but also because of the conditions under which many are carried out. Industrial (and governmental) secrecy is often present. Other conditions also bar access to ascertainment and assessment of the pattern of applications. Lack of a tradition for publication is one. Failure to ascertain the general significance of particular findings is another, as is discouragement arising from the fact that similar applications have previously been published by others. Immediate remedies are not available for these difficulties. Presumably conventions such as this will help, over a period of time, by encouraging informal contacts between interested persons.
A talk on “industrial applications of linear programming” must be altered to suit these circumstances. In place of a survey or evaluation of industrial studies, two broad issues which are relevant to all such applications will be discussed. These are, (1) use of linear programming models as guides to data collection and (2) analysis (and prognosis) of fruitful areas of additional research, especially those which appear to have been opened by industrial applications.
Background, aim, and scopeThe development of robust and up-to-date generic life cycle inventory data for materials is absolutely crucial for the LCA
community since many LCA studies rely on these generic data about materials. LCA databases and software usually include within
their package such generic LCI datasets. However, in many cases, the quality of these data is poor while the methodology and
the models used for their development are rarely accessible or transparent. This paper presents the development of robust
European LCI datasets for the production of primary and recycled aluminium ingots and for the transformation of aluminium
ingot into semi-finished products, i.e. sheet, foil and extrusion.
Materials and methodsThe environmental data have been collected through an extensive environmental survey, organised among the European aluminium
industry, focusing on the year 2005 and covering EU27 countries as well as EFTA countries (Norway, Iceland and Switzerland).
From this survey, European averages, i.e. foreground data, have been calculated for the direct inputs and outputs of the various
aluminium processes. Using the GaBi software, the foreground data have been combined within LCI models integrating background
LCI data on energy supply systems, ancillary processes and materials. For the primary aluminium production (smelters), a specific
model for the electricity production has been developed. The methodology for the data consolidation and for the development
of the various models is explained as well as the main differences between the new modelling approach and LCI models used
in the past. An independent expert has critically reviewed the entire LCI project including data collection, models development,
calculation of LCI data and associated environmental indicators.
ResultsAs confirmed by the critical review, the new LCI datasets for aluminium ingot production and transformation into semi-finished
products have been developed though a robust methodology in full accordance with ISO 14040 and 14044. Most significant environmental
data and LCI results are reported in this paper with an emphasis on energy use and the major emissions to air. The full environmental
report, including the critical review report and the calculation of environmental indicators for a pre-set of impact categories,
is available on the website of the European Aluminium Association (EAA 2008). Whenever possible, the updated European averages and the new LCI data are compared with previous results developed from
two past European surveys covering respectively the years 2002 and 1998. For the aluminium processes related to primary production,
European averages are also benchmarked against global averages calculated from two worldwide surveys covering the years 2000
and 2005.
DiscussionWhile some data evolutions are directly attributed to the variation of foreground data, e.g. raw materials consumption or
energy use within the aluminium processes, modifications related to the system boundaries, the background data and the modelling
hypotheses can also influence significantly the LCI results. For primary aluminium production, the evolution of the foreground
data is dominated by the strong decrease of PFC (perfluorocarbon) emissions (about 70% since 1998). In addition, the electricity
structure calculated from the refined electricity model shows significant differences compared to previous models. In the
2005 electricity model, the hydropower share reaches 58% while coal contributes to 15% only of the electricity production.
In 1998, the respective share of coal-based and hydro-electricity were respectively calculated to 25% and 52%. As a result,
the electricity background LCI data are then significantly affected and influence also positively the environmental profile
of primary aluminium in Europe. For the semi-production processes, the reduction of process scrap production, especially for
extrusion and foil, demonstrates the increase of process efficiency from 1998. In parallel, a significant reduction of energy
use is observed between 1998 and 2005. However, this positive trend is not fully reflected within LCI data due to the significant
contribution of the background electricity data. The choice of the electricity model plays also a critical role for these
transformation processes since electricity production contributes to about 2/3 of the consumption of the non-renewable energy
and to about the same level of the air emissions. In such a case, the move from the UCPTE electricity model used in the past
towards the EU25 electricity model used for the development of the updated LCI data has a detrimental effect on the environmental
profile of the three LCI datasets respectively related to sheet, foil and extrusion. In addition to energy and process scrap
reduction, the reduction of the VOC (volatile organic compounds) emission is also a major trend in foil production. Finally,
for old aluminium scrap recycling, the new LCI data show a dramatic improvement regarding energy efficiency, reinforcing the
environmental soundness of promoting and supporting aluminium recycling within the aluminium product life cycles.
ConclusionsThis paper shows the development of generic LCI data about aluminium production and transformation processes which are based
on robust data, methodologies and models in full accordance with ISO 14040 and 14044 standards, as confirmed by the critical
review. The publishing of these LCI datasets definitely shows the commitment of the European aluminium industry to contribute
in a transparent, fair and scientifically sound manner to product sustainability in a life cycle thinking perspective.
Recommendations and perspectivesSoftware houses and LCA practitioners are invited to update their generic European data on aluminium with the herewith datasets.
Even if the quality and the completeness of these LCI data reach a high standard, some areas for data improvements have been
identified, as described within the review report. Land use, water use and solid waste treatment appear as three priority
areas for data refining and improvement. The land use dimension, particularly meaningful for bauxite mining, is not covered
in the current LCI data while it is now integrated within many LCA studies. Up to now, the reporting of meaningful and robust
data on water origins and use have not been possible due to the huge discrepancies between the surveyed sites combined with
the difficulty to report coherent input and output water mass flows. The development of water data, only focussing on water-stressed
areas, will most probably make more sense in the future. Finally, collecting more qualitative information about solid waste
processing and treatment will help to include such operations within the system boundaries and to model their associated air,
water and soil emissions.
Gaseous and solid fluxes play an important role in the degassing, demagging, and fluxing of aluminum and its alloys. Inert
as well as reactive gases, or hexachloroethane, may be used to remove dissolved hydrogen and sodium. Magnesium may be removed
by chlorine or an aluminum-fluoride-containing flux. Fluxes based on a KCl-NaCl mixture may be used to cover and protect the
metal from oxidation. To recover aluminum from drosses, a more reactive flux containing cryolite or some other fluoride may
be used. In this article, the thermodynamics of aluminum melting and refining are analyzed in terms of the behavior of sodium,
magnesium, and calcium. The coalescence of aluminum drops in salt fluxes improves with fluoride additions. With increasing
MgCl2 contents in the flux, the effects of NaF and KF additions become much less pronounced.
Life cycle management (LCM) aims at expanding the scope of the environmental management system of a company to address the up- and downstream impacts associated with the activities of its suppliers and customers. It is based on a perspective that focuses on products and the corresponding processes in addition to facilities and production sites. Therefore, the life cycle assessment (LCA) methodology plays a central role in implementing LCM. At Alcan, one of the world's leading producers of aluminum materials and products, as well as composite components and packaging solutions, LCA as a core element of LCM is being used for a variety of applications. In order to achieve the objectives of LCM and to ensure efficient decision support, the LCAs are performed in a simplified mode. Simplifications predominantly concern up- and downstream processes outside of Alcan's direct control as well as impact assessment procedures, the reuse of internal life cycle inventory analysis modules, and the aggregation and presentation of the results for top-management and other internal decision-makers. A recently completed LCA from the automotive sector demonstrates the ongoing implementation of LCA at Alcan.
There must be a change in attitude towards end-of-life products. The view that these products pose a liability must be changed. Secondary material is valuable as raw material. Thus, activities encouraging changes in opinion are important.Two major EU directives guide the recycling process; the Directive of End-of-Life Vehicles (ELV) and the Directive of Waste Electrical and Electronic Equipment (WEEE). Both focus on the input of the recycling system, not on what is coming out of the system.The WEEE Directive is the legislation on the European level that governs the handling and processing of these types of products. The WEEE Directive is not only aimed at stricter handling and reduction of hazardous materials but also encourages EU member states to support technical development in order to facilitate increased recycling.In order to properly address these issues a mind-set, material hygiene, has been introduced. The basic idea is to act, in every life cycle phase of the product, towards highest possible efficiency in recycling. The outcome of useful material is in focus.A study on dishwashers is made with copper outcome as target. The results are based on Swedish conditions but general conclusions can be made. Limited design efforts can raise the outcome of valuable materials, if the recycling process is organized in an optimal manner.A theoretical concept of disassembly structures is used to draw general conclusions on the case study.Increasing product recycling suitability is one side of the problem; another is increasing effectiveness of handling and processing of end-of-life products.The purpose of this paper is to introduce the concept of “material hygiene” and based on that demonstrate a method for grading structural properties in a recycling perspective. The findings presented in this paper are based on a field study in which a number of dishwashers were disassembled and analyzed.
Contaminants cause a decrease in the quality of materials with each recycling step. These quality losses should be minimized to increase the sustainability of resources use. Quality losses cannot be measured using weight-based recovery definitions alone, as the quality degradation cannot be translated by mass measures. Therefore, a better measure of the efficiency of resource use is investigated in the present work. Exergy is a measure of the quality of the energy and of resources in systems. The exergy losses are a thermodynamic measure of exhaustion and thus, of the quality losses in the resource systems. We describe a method to calculate the exergy content and exergy losses of metals during recovery and recycling of a concept car. The exergy losses attributed to recycling (the pollution with other metals) and the consequent need for dilution can be used as indicators of the quality loss of materials and of the efficiency of resource use in product systems.
For most materials used to provide buildings, infrastructure, equipment and products, global stocks are still sufficient to meet anticipated demand, but the environmental impacts of materials production and processing, particularly those related to energy, are rapidly becoming critical. These impacts can be ameliorated to some extent by the ongoing pursuit of efficiencies within existing processes, but demand is anticipated to double in the next 40 years, and this will lead to an unacceptable increase in overall impacts unless the total requirement for material production and processing is reduced. This is the goal of material efficiency, and this paper aims to stimulate interest in the area. Four major strategies for reducing material demand through material efficiency are discussed: longer-lasting products; modularisation and remanufacturing; component re-use; designing products with less material. In industrialised nations, these strategies have had little attention, because of economic, regulatory and social barriers, which are each examined. However, evidence from waste management and the pursuit of energy efficiency suggests that these barriers might be overcome, and an outline of potential mechanisms for change is given. In bringing together insights into material efficiency from a wide range of disciplines, the paper presents a set of 20 open questions for future work.
The effective reuse and recycling of metals will be a necessary element of the transition to a sustainable technology-based society. Realizing this will require actions by stakeholders throughout the materials system, this paper examines the use of mathematical programming models to identify detailed strategies for improving the reuse capacity for aluminum. Results, in particular sensitivity analysis, from this model are demonstrated to provide quantitative guidance for secondary metal processors, remelters, and product designers in their collection, selection, modification, and specification of materials. Using a case study involving hypothetical closed loop recycling of automotive aluminum, model results are used to guide alloy choices that improve reuse capacity by nearly 20%. Additionally, dozens of alloy compositional specifications are identified which offer both financial and reuse capacity benefits. The results and methods presented serve as a basis for intentional materials system design.
Operational uncertainties create disincentives for use of recycled materials in metal alloy production. One that greatly influences remelter batch optimization is variation in the raw material composition, particularly for secondary materials. Currently, to accommodate compositional variation, firms commonly set production targets well inside the window of compositional specification required for performance reasons. Window narrowing, while effective, does not make use of statistical sampling data, leading to sub-optimal usage of recycled materials. This paper explores the use of a chance-constrained optimization method, which allows explicit consideration of statistical information on composition. The framework and a case study of cast and wrought production with available scrap materials are presented. Results show that it is possible to increase the use of recycled material without compromising the likelihood of batch errors, when using this method compared to conventional window narrowing. This benefit of the chance-constrained method grows with increase in compositional uncertainty and is driven by scrap portfolio diversification.
This study presents the results of chemical thermodynamic analysis on the distribution of elements in the smelting process of metallic materials to examine the controllability of impurities in the pyrometallurgical technique. The results of the present work can give an answer against the frequently given question; "Which impurity element can be removable in metallurgical process?" or "How far can the impurity level be controlled?". The proposed method was applied to estimate the distribution of 29 elements for a copper converter and 26 elements for a steel-making process and shows the distribution tendency of elements among the gas, slag, and metal phases as well as clarifying which metals can be recovered or removed from secondary resources in metallurgical processes. The effects of temperature, oxygen partial pressure, and slag composition on the distribution ratio of elements were also evaluated, and the removal limit or controllability of impurity in these two processes was presented. This study results in thermodynamic features of various elements in the pyrometallurgical process and also shows, even by varying process parameters such as temperature and oxygen partial pressure, no drastic improvement of removal efficiency should be expected, except for lead and tin in copper.
In previous studies on the physical chemistry of pyrometallurgical processing of aluminum scrap, only a limited number of thermodynamic parameters, such as the Gibbs free energy change of impurity reactions and the variation of activity of an impurity in molten aluminum, were taken into account. In contrast, in this study we thermodynamically evaluated the quantitative removal limit of impurities during the remelting of aluminum scrap; all relevant parameters, such as the total pressure, the activity coefficient of the target impurity, the temperature, the oxygen partial pressure, and the activity coefficient of oxidation product, were considered. For 45 elements that usually occur in aluminum products, the distribution ratios among the metal, slag, and gas phases in the aluminum remelting process were obtained. Our results show that, except for elements such as Mg and Zn, most of the impurities occurred as troublesome tramp elements that are difficult to remove, and our results also indicate that the extent to which the process parameters such as oxygen partial pressure, temperature, and flux composition can be changed in aluminum production is quite limited compared to that for iron and copper production, owing to aluminum's relatively low melting point and strong affinity for oxygen. Therefore, the control of impurities in the disassembly process and the quality of scrap play important roles in suppressing contamination in aluminum recycling.
In the methodological context of the interpretation of environmental life cycle assessment (LCA) results, a normalisation study was performed. 15 impact categories were accounted for, including climate change, acidification, eutrophication, human toxicity, ecotoxicity, depletion of fossil energy resources, and land use. The year 2000 was chosen as a reference year, and information was gathered on two spatial levels: the global and the European level. From the 860 environmental interventions collected, 48 interventions turned out to account for at least 75% of the impact scores of all impact categories. All non-toxicity related, emission dependent impacts are fully dominated by the bulk emissions of only 10 substances or substance groups: CO(2), CH(4), SO(2), NO(x), NH(3), PM(10), NMVOC, and (H)CFCs emissions to air and emissions of N- and P-compounds to fresh water. For the toxicity-related emissions (pesticides, organics, metal compounds and some specific inorganics), the availability of information was still very limited, leading to large uncertainty in the corresponding normalisation factors. Apart from their usefulness as a reference for LCA studies, the results of this study stress the importance of efficient measures to combat bulk emissions and to promote the registration of potentially toxic emissions on a more comprehensive scale.
This paper originated from an industrial case study in the field of the aluminium supply chain. In particular, the most original aspects of the study are linked to the use of an alternative supply method for raw material (aluminium) in manufacturing. This method consists in the possibility of the company receiving the aluminium alloy from its supplier (refiner and remelter of secondary aluminium) in the liquid phase, as an alternative to the traditional supply of solid material.This practice has been possible by the use of special ladles, transportable by truck and moved within factories, thanks to specially equipped overhead bridge cranes. The supply of molten metal represents a substantial benefit for the whole supply chain, because of the energy savings implicit in the method itself (i.e. both energy and time can be saved when melting the metal at the company furnaces). Moreover, the study integrates the concerns about transport pollution, addressing the topics of a green supply chain problem and incorporating the environmental aspects in its analytical description. Therefore, the study proposes a model to evaluate the economic and environmental effects of the industrial practice described. The result of the model is the determination of the supply aluminium mix, i.e. molten and solid alloy, capable of balancing the economic benefits (highest scrap values, lowest total costs, etc.) as well as environmental requirements (least pollution).
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The properties and uses of fluxes in molten aluminum processing Quality evaluation of steel, aluminum, and road material recycled from end-of-life urban buildings in Japan in terms of total material requirement
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