How much sorting is required for a circular low carbon aluminum economy?

Aluminum recycling follows a downcycling dynamic where wrought alloys are transformed into cast alloys, accumulating tramp elements at every cycle. With the saturation of stocks of aluminum and the reduction of the demand for cast alloy due to electrification of transport, improvement in the recycling system must be made to avoid a surplus of unused recycled aluminum, reduce the overall environmental impacts of the industry, and move toward a circular economy. We aim to evaluate the potential environmental benefits of improving sorting efforts by combining operations research, prospective material flow analysis, and life cycle assessment. An optimization defines the optimal sorting to minimize climate change impacts according to different sorting efforts, dismantling conditions, and collection rates. Results show how the improvement of sorting can reduce by around 30% the greenhouse gas emissions of the industry, notably by reducing unused scrap generation and increasing the recycled content of the flows that supply the demand of aluminum. The best performance is achievable with four different sorting pathways. Further improvements occur with a better dismantling and an increase of collection rates, but it requires more sorting pathways. Results point to different closed-loop recycling initiatives that should be promoted on priority in specific sectors, like the building and construction sector and the aluminum cans industry. To implement a better material circularity, the mobilization of different stakeholders is needed. From a wider perspective, the article shows how operations research can be used to project a circular future in a specific industry. This article met the requirements for a Gold–Gold JIE data openness badge described at http://jie.click/badges .      

Design for Recycling

As design for recycling becomes more broadly applied in material and product design, analytical tools to quantify the environmental implications of design choices will become a necessity. Currently, few systematic methods exist to measure and direct the metallurgical alloy design process to create alloys that are most able to be produced from scrap. This is due, in part, to the difficulty in evaluating such a context‐dependent property as recyclability of an alloy, which will depend on the types of scraps available to producers, the compositional characteristics of those scraps, their yield, and the alloy specification itself. This article explores the use of a chance‐constrained based optimization model, similar to models used in operational planning in secondary production today, to (1) characterize the challenge of developing recycling‐friendly alloys due to the contextual sensitivity of recycling, (2) demonstrate how such models can be used to evaluate the potential scrap usage of alloys, and (3) explore the value of sensitivity analysis information to proactively identify effective alloy modifications that can drive increased potential scrap use. These objectives are demonstrated through two cases that involve the production of a broad range of alloys utilizing representative scraps from three classes of industrial end uses.     

Evaluation of Life Cycle Assessment Recycling Allocation Methods

Life cycle assessment practitioners struggle to accurately allocate environmental burdens of metals recycling, including the temporal dimension of environmental impacts. We analyze four approaches for calculating aluminum greenhouse gas emissions: the recycled content (RC) or cut‐off approach, which assumes that demand for recycled content displaces primary production; end‐of‐life recycling (EOLR), which assumes that postuse recycling displaces primary production; market‐based (MB) approaches, which estimate changes in supply and demand using price elasticities; and value‐corrected substitution (VCS), which allocates impact based on price differences between primary and recycled material. Our analysis suggests that applications of the VCS approach do not adequately account for the changing scrap to virgin material price ratio over time, whereas MB approaches do not address stock accumulation and depletion. The EOLR and RC approaches were analyzed using two case studies: U.S. aluminum beverage cans and vehicle engine blocks. These approaches produced similar results for beverage cans, which have a closed material loop system and a short product life. With longer product lifetimes, as noted with the engine blocks, the magnitude and timing of the emissions differs greatly between the RC and EOLR approaches. The EOLR approach indicates increased impacts at the time of production, offset by negative impacts in future years, whereas the RC approach assumes benefits to increased recycled content at the time of production. For vehicle engine blocks, emissions using EOLR are 140% higher than with RC. Results are highly sensitive to recycled content and future recycling rates, and the choice of allocation methods can have significant implications for life cycle studies.     

Recycling Rates of Aluminum in the United States

Recycling rates of aluminum are defined in different (sometimes inconsistent) ways and poorly quantified. To address this situation, the definitions and calculation methods of four groups of indicators are specified for the United States: (1) indicators used to measure recycling efficiencies of old aluminum scrap at the end‐of‐life (EOL) stage, including EOL collection rate (CR), EOL processing rate, EOL recycling rate, and EOL domestic recycling rate; (2) indicators used to compare generation or use of new with old scrap, including new to old scrap ratio, new scrap ratio (NSR), and old scrap ratio; (3) indicators used to compare production or use of primary aluminum with secondary aluminum, including four recycling input rates (RIRs); and (4) indicators used to track the sinks of aluminum metal in the U.S. anthroposphere. I find that the central estimate of EOL CR varies between 38% and 65% in the United States from 1980 to 2009 and shares a relatively similar historical trend with the primary aluminum price. The RIR is shown to be significantly reduced if excluding secondary aluminum produced from new scrap resulting from the relatively high NSR. In 2003, a time when approximately 73% of all of the aluminum produced globally since 1950 was considered to still be “in service,” approximately 68% to 69% of all metallic aluminum that had entered the U.S. anthroposphere since 1900 was still in use: 67% in domestic in‐use stock and 1% to 2% exported as scrap. Only 6% to 7% was definitely lost to the environment, although the destination of 25% of the aluminum was unknown. It was either exported as EOL products, was currently hibernating, or was lost during collection.     

Quality Evaluation of Steel,Aluminum, and Road Material Recycled from End‐of‐Life Urban Buildings in Japan in Terms of Total Material Requirement

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.     

Influence of Input‐Scrap Quality on the Environmental Impact of Secondary Steel Production

In electric arc furnaces (EAFs), different grades of steel scrap are combined to produce the targeted carbon steel quality. The goal of this study is to assess the influence of scrap quality on the recycling process and on the final product by investigating the effect of the scrap mix composition, and other inputs, for example, preheating energy, on the electricity demand of the melting process. A large industrial data set (empirical data set of ～20,000 individual heats recorded during 2.5 years at a Swiss EAF site) is analyzed using linear regression. The influence of scrap grades on electricity demand are found to correlate strongly with their respective quality; specific electricity demand is up to 45% higher for low‐quality scrap than for high‐quality scrap. Given that chemical compositions of scrap grades are highly variable and often unknown, average concentrations are determined using linear regression with scrap input as the predictors and the amounts of the investigated elements in liquid steel as the dependent variable. The lowest quality (highest copper and tin concentrations) and the highest electricity demand in the EAF are found for scrap recovered from bottom ashes of municipal solid waste incineration. Although even with low‐quality scrap input steel recycling is environmentally superior to primary steel production, the optimization potential in terms of energy efficiency and resource recovery, for example, through pretreatment, seems to be substantial.     

Toward Estimating Displaced Primary Production from Recycling: A Case Study of U.S. Aluminum

Recycling materials from end‐of‐life products has the potential to create environmental benefit by displacing more harmful primary material production. However, displacement is governed by market forces and is not guaranteed; if full displacement does not occur, the environmental benefits of recycling are reduced or eliminated. Therefore, quantifying the true “displacement rate” caused by recycling is essential to accurately assess environmental benefits and make optimal environmental management decisions. Our 2016 article proposed a market‐based methodology to estimate actual displacement rates following an increase in recycling or reuse. The current article demonstrates the operation, utility, and challenges of that methodology in the context of the U.S. aluminum industry. Sensitivity analyses reveal that displacement estimates are sensitive to uncertainty in price elasticities. Results suggest that 100% displacement is unlikely immediately following a sustained supply‐driven increase in aluminum recycling and even less likely in the long term. However, zero and even negative displacement are possible. A variant of the model revealed that demand‐driven increases in recycling are less likely than supply‐driven changes to result in full displacement. However, model limitations exist and challenges arose in the estimation process, the effects of which are discussed. We suggest implications for environmental assessment, present lessons learned from applying the estimation methodology, and highlight the need for further research in the market dynamics of recycling.     

What Do We Know About Metal Recycling Rates?

The recycling of metals is widely viewed as a fruitful sustainability strategy, but little information is available on the degree to which recycling is actually taking place. This article provides an overview on the current knowledge of recycling rates for 60 metals. We propose various recycling metrics, discuss relevant aspects of recycling processes, and present current estimates on global end‐of‐life recycling rates (EOL‐RR; i.e., the percentage of a metal in discards that is actually recycled), recycled content (RC), and old scrap ratios (OSRs; i.e., the share of old scrap in the total scrap flow). Because of increases in metal use over time and long metal in‐use lifetimes, many RC values are low and will remain so for the foreseeable future. Because of relatively low efficiencies in the collection and processing of most discarded products, inherent limitations in recycling processes, and the fact that primary material is often relatively abundant and low‐cost (which thereby keeps down the price of scrap), many EOL‐RRs are very low: Only for 18 metals (silver, aluminum, gold, cobalt, chromium, copper, iron, manganese, niobium, nickel, lead, palladium, platinum, rhenium, rhodium, tin, titanium, and zinc) is the EOL‐RR above 50% at present. Only for niobium, lead, and ruthenium is the RC above 50%, although 16 metals are in the 25% to 50% range. Thirteen metals have an OSR greater than 50%. These estimates may be used in considerations of whether recycling efficiencies can be improved; which metric could best encourage improved effectiveness in recycling; and an improved understanding of the dependence of recycling on economics, technology, and other factors.     

The Global Flow of Hard Disk Drives: Quantifying the Concept of Value Leakage in E‐waste Recovery Systems

The remaining value within end‐of‐use/life hard disk drives (EoU/L HDDs) is often not optimally recovered. The improper collection and recovery of HDDs contribute not only to rising environmental and social concerns worldwide, but also to the transformation of the economy and a significant loss of value. Currently, the most preferred treatment option for used hard drives is to recover the metals with the highest recycling effectiveness, such as steel and aluminum, via a shredding‐based recycling process that results in both value and material leakages. The complexity of retrieving the remaining values within EoU/L HDDs demands a larger view of the global supply of HDDs available for recovery. The aim of this paper is to first identify the geographical patterns of transboundary global shipments of new and used HDDs between developing and developed regions, and then capture and quantify the value leakage by bringing several unique perspectives. Two analyses have been conducted. First, the loss of value due to the insufficient recovery of neodymium (Nd) at the global level is quantified. Second, the value leakage as a result of the delay on on‐time reuse of HDDs is captured. Furthermore, the central challenges toward proper recovery of HDDs, where consumer electronic industry can make significant contributions, have been identified. HDDs are well positioned to contribute important insights to the recovery of other electronic devices, so the findings from HDDs can be adopted for other types of electronics.     

Closed‐Loop Supply Chains for Photovoltaic Panels: A Case‐Based Approach

Photovoltaic (PV) waste is expected to significantly increase. However, legislation on producer responsibility for the collection and recovery of PV panels is limited to the European Union (EU) Waste Electrical and Electronic Equipment Directive Recast, which lays down design, collection, and recovery measures. Academic knowledge of closed‐loop supply chains (CLSCs) for PV panels is scarce. We analyze the supply chain using multiple cases involving the main stakeholders in the design, production, collection, and recovery of PV panels. Our article answers two research questions: How does the PV supply chain operate, and what are critical factors affecting the reverse supply chain management of used panels? Our research seeks to fill the gap in the CLSC literature on PV panels, as well as to identify barriers and enablers for PV panel design, collection, and recycling.     

Evaluation of the Metals Industry's Position on Recycling and its Implications for Environmental Emissions

A healthy debate on the treatment of metals recycling in the life cycle assessment (LCA) community has persisted for more than a decade. While no clear consensus across stakeholder groups has emerged, the metals industry has endorsed a set of recycling “facts” that support a single approach, end‐of‐life recycling, for evaluating the environmental benefits of metals recycling. In this article we draw from research conducted in several disciplines and find that three key tenets of the metals industry capture the theoretical potential of metals recycling from a metallurgical standpoint rather than reflecting observed behavior. We then discuss the implications of these conclusions on environmental emissions from metals production and recycling. Evidence is provided that, contrary to the position of the metals industry, metals are not necessarily recycled at high rates, are recycled only a small number of times before final disposal, and are sometimes limited in recycling potential by the economics of contaminant removal. The analysis concludes that metal recycled from old scrap largely serves as an imperfect substitute for primary metal. As a result, large‐scale displacement of primary production and its associated environmental emissions is currently limited to a few specific instances.     

Investigating Cross‐Sectoral Synergies through Integrated Aquaculture,Fisheries, and Agriculture Phosphorus Assessments: A Case Study of Norway

Future phosphorus (P) scarcity and eutrophication risks demonstrate the need for systems‐wide P assessments. Despite the projected drastic increase in world‐wide fish production, P studies have yet to include the aquaculture and fisheries sectors, thus eliminating the possibility of assessing their relative importance and identifying opportunities for recycling. Using Norway as a case, this study presents the results of a current‐status integrated fisheries, aquaculture, and agriculture P flow analysis and identifies current sectoral linkages as well as potential cross‐sectoral synergies where P use can be optimized. A scenario was developed to shed light on how the projected 2050 fivefold Norwegian aquaculture growth will likely affect P demand and secondary P resources. The results indicate that, contrary to most other countries where agriculture dominates, in Norway, aquaculture and agriculture drive P consumption and losses at similar levels and secondary P recycling, both intra‐ and cross‐sectorally, is far from optimized. The scenario results suggest that the projected aquaculture growth will make the Norwegian aquaculture sector approximately 4 times as P intensive as compared to agriculture, in terms of both imported P and losses. This will create not only future environmental challenges, but also opportunities for cross‐sectoral P recycling that could help alleviate the mineral P demands of agriculture. Near‐term policy measures should focus on utilizing domestic fish scrap for animal husbandry and/or fish feed production. Long‐term efforts should focus on improving technology and environmental systems analysis methods to enable P recovery from aquaculture production and manure distribution in animal husbandry.     

Dynamic Substance Flow Analysis of Neodymium and Dysprosium Associated with Neodymium Magnets in Japan

Recycling of neodymium and dysprosium is of great interest because of the rapid growth in their demand and limited supply of new resources. To promote recovery from end‐of‐life (EoL) products, it is desirable to quantify the recycling potentials of neodymium and dysprosium by their end use. This study characterized the substance flows of neodymium and dysprosium associated with neodymium magnets in Japan by conducting a dynamic substance flow analysis. A bottom‐up approach was employed in the analysis to estimate annual consumption by end use. Factors used in the analysis were the amounts of rare earth contents, weight of a magnet used for each product, adoption ratios of neodymium magnet usage in each product, and lifetime of products. It was found that the amount of neodymium entering use was approximately half of the domestic consumption; the balance existing in final products that were exported from Japan. The economic feasibility of recycling neodymium magnets was evaluated for their largest two end uses: driving motors in hybrid electric vehicles (HEVs) and compressors in air conditioners. It was found that recycling the neodymium magnets used in the driving motors has the potential for economic feasibility in Japan. The result showed that lower transportation costs for recovered magnets can make the recycling economically feasible regardless of the content rate and the price of metals. The future increase of EoL HEVs contributes to the feasibility of recycling with a profit in the upcoming years. Strategies for more profitable recycling are concentrating scrap motors or magnets among recycling factories or selecting specific factories that deal with EoL HEVs.     

Quality Assessment and Circularity Potential of Recovery Systems for Household Plastic Waste

Plastic recycling is promoted in the transition toward a circular economy and a closed plastic loop, typically using mass‐based recycling targets. Plastic from household waste (HHW) is contaminated and heterogeneous, and recycled plastic from HHW often has a limited application range, due to reduced quality. To correctly assess the ability to close plastic loops via recycling, both plastic quantities and qualities need to be evaluated. This study defines a circularity potential representing the ability of a recovery system to close material loops assuming steady‐state market conditions. Based on an average plastic waste composition including impurities, 84 recovery scenarios representing a wide range of sorting schemes, source‐separation efficiencies, and material recovery facility (MRF) configurations and performances were assessed. The qualities of the recovered fractions were assessed based on contamination and the circularity potential calculated for each scenario in a European context. Across all scenarios, 17% to 100% of the generated plastic mass could be recovered, with higher source‐separation and MRF efficiencies leading to higher recovery. Including quality, however, at best 55% of the generated plastic was suitable for recycling due to contamination. Source‐separation, a high number of target fractions, and efficient MRF recovery were found to be critical. The circularity potential illustrated that less than 42% of the plastic loop can be closed with current technology and raw material demands. Hence, Europe is still far from able to close the plastic loop. When transitioning toward a circular economy, the focus should be on limiting impurities and losses through product design, technology improvement, and more targeted plastic waste management.     

Identifying Stakeholders’ Views on the Eco‐efficiency Assessment of a Municipal Solid Waste Management System

Life cycle assessment (LCA) is one of the most popular methods of technical‐environmental assessment for informing environmental policies, as, for instance, in municipal solid waste (MSW) management. Because MSW management involves many stakeholders with possibly conflicting interests, the implementation of an LCA‐based policy can, however, be blocked or delayed. A stakeholder assessment of future scenarios helps identify conflicting interests and anticipate barriers of sustainable MSW management systems. This article presents such an approach for Swiss waste glass‐packaging disposal, currently undergoing a policy review. In an online survey, stakeholders (N = 85) were asked to assess disposal scenarios showing different LCA‐based eco‐efficiencies with respect to their desirability and probability of occurrence. Scenarios with higher eco‐efficiency than the current system are more desirable and considered more probable than those with lower eco‐efficiency. A combination of inland recycling and downcycling to foam glass (insulation material) in Switzerland is desired by all stakeholders and is more eco‐efficient than the current system. In contrast, institutions of MSW management, such as national and regional environmental protection agencies, judge a scenario in which nearly all cullet would be recycled in the only Swiss glass‐packaging factory as more desirable than supply and demand stakeholders of waste glass‐packaging. Such a scenario involves a monopsony rejected by many municipalities and scrap traders. Such an assessment procedure can provide vital information guiding the formulation of environmental policies.     

Environmental Implications and Costs of Municipal Solid Waste‐Derived Ethylene

Carbon recycling, in which organic waste is recycled into chemical feedstock for material production, may provide benefits in resource efficiency and a more cyclical economy—but may also create “trade‐offs” in increased impacts elsewhere. We investigate the system‐wide environmental burdens and cost associated with carbon recycling routes capable of converting municipal solid waste (MSW) by gasification and Fischer‐Tropsch synthesis into ethylene. Results are compared to business‐as‐usual (BAU) cases in which ethylene is derived from fossil resources and waste is either landfilled with methane and energy recovery (BAU#1) or incinerated (BAU#2) with energy recovery. Monte Carlo and sensitivity analysis is used to assess uncertainties of the results. Results indicate that carbon recycling may lead to a reduction in cumulative energy demand (CED), total material requirement (TMR), and acidification, when compared to BAU#1. Global warming potential is found to be similar or slightly lower than BAU#1 and BAU#2. In comparison to BAU#2, carbon recycling results in higher CED, TMR, acidification, and smog potential, mainly as a result of larger (fossil‐based) energy offsets from energy recovery. However, if a renewable power mix (envisioned for the future) is assumed to be offset, BAU#2 impacts may be similar or higher than carbon recycling routes. Production cost per kilogram (kg) MSW‐derived ethylene range between US$1.85 and US$2.06 (Jan 2011 US$). This compares to US$1.17 per kg for fossil‐based ethylene. Waste‐derived ethylene breaks even with its fossil‐based counterpart at a tipping fee of roughly US$42 per metric ton of waste feedstock.     

Use of Incinerator Bottom Ash for Frit Production

This article presents the results of an experimental activity aimed at investigating the technical feasibility and the environmental performance of using municipal solid waste incineration bottom ash to produce glass frit for ceramic glaze (glaze frit). The process includes an industrial pretreatment of bottom ash that renders the material suitable for use in glaze frit production and allows recovery of aluminum and iron. The environmental performance of this treatment option is assessed with the life cycle assessment (LCA) methodology. The goal of the LCA study is to assess and compare the environmental impacts of two scenarios of end of life of bottom ash from municipal solid waste incineration (MSWI): landfill disposal (conventional scenario) and bottom ash recovery for glaze frit production (innovative scenario). The main results of the laboratory tests, industrial simulations, and LCA study are presented and discussed, and the environmental advantages of recycling versus landfill disposal are highlighted.     

Recovery of scrap iron metal value using biogenerated ferric iron

The utility of employing biogenerated ferric iron as an oxidant for the recycling of scrap metal has been demonstrated using continuously growing cells of the extremophilic organism Acidithiobacillus ferrooxidans. A ferric iron rich (70 mol%) lixiviant resulting from bioreactor based growth of A. ferrooxidans readily solubilized target scrap metal with the resultant generation of a leachate containing elevated ferrous iron levels and solubilized copper previously resident in the scrap metal. Recovery of the copper value was easily accomplished via a cementation reaction and the clarified leachate containing a replenished level of ferrous iron as growth substrate was shown to support the growth of A. ferrooxidans and be fully recyclable. The described process for scrap metal recycling and copper recovery was shown to be efficient and economically attractive. Additionally, the utility of employing the E(h) of the growth medium as a means for monitoring fluctuations in cell density in cultures of A. ferrooxidans is demonstrated.     

The Impact of Scale,Recycling Boundary,and Type of Waste on Symbiosis and Recycling

Innovative waste recycling through industrial processes such as industrial and urban symbiosis has long been practiced and recently received much attention in the field of industrial ecology, with researchers making efforts to identify key contributing factors to successful industrial symbiosis. By analyzing 88 sample recycling projects in 23 eco‐towns in Japan, this article focuses on the factors of project scale, recycling boundary, and types of waste in relationship to environmental benefits and operational performance. The results showed that larger eco‐towns achieved more savings of virgin materials and higher stability in operation. Large‐scale projects tended to locate closer to the users of recycled products than did small‐scale projects. For treating similar types of waste, projects producing recycled products for special users (e.g., feedstock to a blast furnace for iron production) tended to locate closer to the users than those not producing for special users. The type of waste had a strong effect on the savings of virgin materials and recycling boundaries, while local factors had significant impacts on operational performance. The results also showed that agglomeration did not significantly contribute to the environmental benefits or operational performance of eco‐town projects. Another finding was that national agencies were helpful for facilitating cross‐prefecture transportation and long‐distance transaction of wastes. Implications of the findings are also discussed.