Sustainable aluminium recycling of end-of-life products: A joining techniques perspective

The sustainable management of aluminium has become crucial due to the exponential growth in global demand. The transition to a sustainable society with lightweight electric vehicles has led to the increasing use of aluminium in the transportation sector. This has consequently led to the importance of aluminium recycling to prevent the valuable material stream going to landfill. In addition, the extraction of primary aluminium has high environmental impact due to the high energy consumption and waste generation in comparison to secondary aluminium processing. Despite being one of the most recycled metals, ongoing trends of multi-material designs and the associated joining choices have caused increasing difficulty of separating aluminium with high purity. This paper evaluates the types of joining techniques causing impurities in the aluminium streams, and the relationship between particle size reduction and the presence of impurities due to joints particularly for end-of-life vehicles. An empirical experiment in a leading European recycling facility was conducted and demonstrated that mechanical fasteners, such as machine screws, socket screws, bolt screws and rivets, are the major types of joining technique causing impurities. Based on the observations from this case study, the characteristics of imperfectly liberated joints are examined. A Life Cycle Assessment (LCA) is also performed to evaluate the environmental impact of recycling different aluminium scrap qualities with varying impurity levels. The outcomes are then used to provide ecodesign guidelines aimed at improving the quality and increase the quantity of recycled aluminium.This study is supported by the Commonwealth Government CRC Program (AutoCRC), the Australian National University, and the Centre for Industrial Management, University of Leuven

Preparatory study of Ecodesign and Energy Labelling measures for High Pressure Cleaners

Following the Ecodesign Working Plan 2016-20191, the European Commission launched in 2018 a preparatory study for the product group ‘high pressure cleaners’. The preparatory study follows the Commission’s Methodology for the Evaluation of Energy related Products (MEErP). It consists of: Scope definition, standard methods and legislation, Market analysis, Analysis of user behaviour and system aspects, Analysis of technologies, Environmental and economics, Design options and Policy analysis and scenarios The comprehensive analysis of the product group following the steps above will provide the technical and scientific evidence for policy-making decisions. The research is based on available scientific information and data, uses a life-cycle thinking approach, and has engaged stakeholder experts in order to discuss key issues, and to the extent possible reach consensus on the proposals.JRC.B.5-Circular Economy and Industrial Leadershi

Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation

Recently, “meltless” recycling techniques have been presented for the light metals category, targeting both energy and material savings by bypassing the final recycling step of remelting. In this context, the use of spark plasma sintering (SPS) is proposed in this paper as a novel solid-state recycling technique. The objective is two-fold: (I) to prove the technical feasibility of this approach; and (II) to characterize the recycled samples. Aluminum (Al) alloy scrap was selected to demonstrate the SPS effectiveness in producing fully-dense samples. For this purpose, Al alloy scrap in the form of machining chips was cold pre-compacted and sintered bellow the solidus temperature at 490 °C, under elevated pressure of 200 MPa. The dynamic scrap compaction, combined with electric current-based joule heating, achieved partial fracture of the stable surface oxides, desorption of the entrapped gases and activated the metallic surfaces, resulting in efficient solid-state chip welding eliminating residual porosity. The microhardness, the texture, the mechanical properties, the microstructure and the density of the recycled specimens have been investigated. An X-ray computed tomography (CT) analysis confirmed the density measurements, revealing a void-less bulk material with homogeneously distributed intermetallic compounds and oxides. The oxide content of the chips incorporated within the recycled material slightly increases its elastic properties. Finally, a thermal distribution simulation of the process in different segments illustrates the improved energy efficiency of this approach

Sustainable Metal Management and Solid State Recycling of Aluminium and Magnesium Alloys ,,

Starting from existing challenges and limitations in light metal recycling (in particular aluminium and magnesium alloys), this PhD thesis aims to address these and explore new opportunities by sustainable metal management and solid-state recycling (SSR) methods. This PhD also quantifies the potential environmental benefits of the explored strategies and SSR techniques by Life Cycle Assessment (LCA). More specifically: During pyro-metallurgical recycling of aluminium alloys, the refining/melt purification options of aluminium alloys, restricted by thermodynamic barriers, are very limited compared to other base metals such as steels. As the removal from the melt of most elements is problematic, it is crucial to control their concentration in the scrap streams prior to remelting. Thus, scrap sorting is important to avoid additional (eventually impossible) refining, quality degradation (down-cycling), and dilution of the residual elements with primary aluminium addition. It is therefore described that establishing of well-optimised, harmonised recycling loops is of prime importance from an environmental perspective. Based on these arguments, Chapter 2 addresses this issue by developing a decision support model that aids in the direction of environmental conscious metal clustering. It aims: i) to express and quantify in a LCA framework, dilution and quality losses that occur during open loop recycling, and ii) to determine the optimal material input for the recycling process based on the input/output metal composition. By compositionally closing the recycling loops, it is feasible to minimise primary resource addition (primary aluminium and alloying elements) by maximising the scrap utilisation. A multi-objective optimisation approach (goal programming) is selected as the most appropriate method to prioritise the optimisation goals. After performing the environmental modelling of the secondary aluminium production as a reference route, Chapter 3 moves on to ‘meltless’ or ‘solid state recycling’ techniques for high grade aluminium production scrap. This approach is studied to achieve a significant material and energy savings by omitting/bypassing the conventional recycling step. Annually more than 40% of liquid aluminium is scrapped during the initial production-fabrication-manufacturing steps. Especially for fine form scrap from material removal processes, their very high surface-to-mass ratio results in significant unrecoverable oxidation losses during remelting. In this context, this work investigates the applicability of Spark Plasma Sintering (SPS) as an alternative SSR technique for aluminium alloy chips (Chapter 3). This allows the direct fabrication of bulk, near-net shape and semi-finished products directly from machining chips. The improved consolidation achieved via SPS is associated with the combined action of plastic deformation and the electric field during SPS processing. Microstructural investigations as well as the mechanical behaviour of the SPS blanks confirm successful solid state chips welding. Furthermore, this work also investigates applications of SPS in scrap consolidation and binding. Chapter 4 examines the use of atomised aluminium powder as a binding material/matrix for the machining chips. Chapter 5 describes the consolidation via SPS of larger scrap types (sheet metal scrap). After developing a reliable SPS route for SSR of aluminium alloy scrap, Chapter 6 analyses the environmental performance of the SPS route along with major SSR routes for aluminium alloys (recycling via hot extrusion and via screw extrusion). For this reason a LCA study was conducted where the examined SSR routes are compared with their corresponding remelting routes as reference. Mg alloys confront similar challenges in recycling as aluminium alloys. Taking also into account the wide range of magnesium applications and their higher scrap value compared to aluminium scraps; Chapter 7 focuses on broadening the material palette of SSR via SPS into Mg alloys. In this respect, this work studies the consolidation of machining chips for two Mg systems (i.e., pure Mg and AZ31 Mg alloy). This includes the microstructural evolution in different metal recycling steps (initial ingot, chips, SPSed samples) as well as the mechanical behaviour of the recycled samples versus their parent material. Finally, the conclusions, the contributions to the state of the art as well as proposed future research topics are discussed in Chapter 8.nrpages: 180status: publishe

ASSuRe - Solid State Recycling of Industrial Aluminium Waste Streams

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Environmental re-engineering of a surface processing and electrostatic coating aluminium plant

Στον παρόν άρθρο μελετάται ο περιβαλλοντικός ανασχεδιασμός μιας μονάδας ηλεκτροστατικής βαφής προφίλ αλουμινίου. Ο περιβαλλοντικός σχεδιασμός περιλαμβάνει την μελέτη και προτάσεις για τεχνολογικά εφικτές εναλλακτικές λύσεις με τη χρήση νέας μεθόδου παθητικοποίησης ελεύθερης χρωμίου, αλλά και τη χρήση νέων πουδρών επίστρωσης χωρίς τοξικά βαρέα μέταλλα. Η εναλλακτική αυτή πρόταση, αξιολογήθηκε με βάση της περιβαλλοντικές επιπτώσεις του εξασθενούς χρωμίου και της νέας μεθόδου ελέυθερης χρωμίου, εφαρμόστηκε στη παραγωγική διαδικασία και βελτιστοποιήθηκε ως προς τα τελικά αποτελέσματα της. Διερευνήθηκαν και αξιολογήθηκαν οι μέθοδοι διαχείρισης και διάθεσης των αποβλήτων (υγρών και στερεών) και των δύο μεθόδων επεξεργασίας του αλουμινίου ως προς τα όρια διάθεσης τους. Η σύγκριση και αξιολόγηση έγινε μέσω πολυκριτιριακής ανάλυσης σε τεχνικό, περιβαλλοντικό, κοινωνικό και οικονομικό επίπεδο. Το αποτέλεσμα είναι περιβαλλοντικά και οικονομοτεχνικά βιώσιμη λύση.status: publishe

Incorporating denitrification-decomposition method to estimate field emissions for Life Cycle Assessment

This study focuses on a detailed Life Cycle Assessment (LCA) for flax cultivation in Northern France. Nitrogen related field emissions are derived both from a process-oriented DeNitrification-DeComposition (DNDC) method and the generic Intergovernmental Panel on Climate Change (IPCC) method. Since the IPCC method is synthesised from field measurements at sites with various soil types, climate conditions, and crops, it contains significant uncertainties. In contrast, the outputs from the DNDC method are considered as more site specific as it is built according to complex models of soil science. As it is demonstrated in this paper the emission factors from the DNDC method and the recommended values from the IPCC method exhibit significant variations for the case of flax cultivation. The DNDC based emission factor for direct N2O emission, which is a strong greenhouse gas, is 0.25-0.5%, significantly lower than the recommend 1% level derived from the IPCC method. The DNDC method leads to a reduction of 17% in the impact category of climate change per kg retted flax straw production from the level obtained from the IPCC method. Much higher reductions are recorded for particulate matter formation, terrestrial acidification, and marine eutrophication impact categories. Meanwhile, based on the DNDC and IPCC methods, a comparative LCA per kg flax straw is presented. For both methods sensitivity analysis as well as comparison of uncertainties parameterisation of the N2O estimates via Monte-Carlo analysis are performed. The DNDC method incorporates more relevant field emissions from the agricultural life cycle phase, which can also improve the quality of the Life Cycle Inventory as well as allow more precise uncertainty calibration in the LCA inventory.publisher: Elsevier articletitle: Incorporating denitrification-decomposition method to estimate field emissions for Life Cycle Assessment journaltitle: Science of The Total Environment articlelink: http://dx.doi.org/10.1016/j.scitotenv.2017.03.112 content_type: article copyright: © 2017 Elsevier B.V. All rights reserved.status: publishe

Environmental modelling of aluminium recycling: a Life Cycle Assessment tool for sustainable metal management

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.publisher: Elsevier articletitle: Environmental modelling of aluminium recycling: a Life Cycle Assessment tool for sustainable metal management journaltitle: Journal of Cleaner Production articlelink: http://dx.doi.org/10.1016/j.jclepro.2014.09.102 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved.status: publishe