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.     

转型期城市生态学前沿研究进展

城市是一类以人类活动为中心听社会－经济－自然复合生态系统。城市人类活动对局地、区域和全球环境的胁迫效应,自然生态系统的响应机制,城市时、空、量、构、序的耦合规律、动力学机制和控制论方法是当前国际社会和学术界关注的热点。介绍了转型期城市人类生态影响研究的一些主要国际科学计划,如ＳＣＯＰＥ及ＩＨＤＰ等,综述了城市生态学研究三大前沿领域的国际研究动向和案例,即人居生态学、产业生态学和城镇生命支持系统生态     

Are future recycling benefits misleading? Prospective life cycle assessment of lithium-ion batteries

Life cycle assessment (LCA) quantifies the whole-life environmental impacts of products and is essential for helping policymakers and manufacturers transition toward sustainable practices. However, typical LCA estimates future recycling benefits as if it happens today. For long-lived products such as lithium-ion batteries, this may be misleading since there is a considerable time gap between production and recycling. To explore this temporal mismatch problem, we apply future electricity scenarios from an integrated assessment model—IMAGE—using “premise” in Brightway2 to conduct a prospective LCA (pLCA) on the global warming potential of six battery chemistries and four recycling routes. We find that by 2050, electricity decarbonization under an RCP2.6 scenario mitigates production impacts by 57%, so to reach zero-carbon batteries it is important to decarbonize upstream heat, fuels, and direct emissions. For the best battery recycling case, data for 2020 gives a net recycling benefit of −22 kg CO₂e kWh⁻¹ which reduces the net impact of production and recycling from 71 to 49 kg CO₂e kWh⁻¹. However, for recycling in 2040 with decarbonized electricity, net recycling benefits would be nearly 75% lower (−6 kg CO₂e kWh⁻¹), giving a net impact of 65 kg CO₂e kWh⁻¹. This is because materials recycled in the future substitute lower-impact processes due to expected electricity decarbonization. Hence, more focus should be placed on mitigating production impacts today instead of relying on future recycling. These findings demonstrate the importance of pLCA in tackling problems such as temporal mismatch that are difficult to capture in typical LCA.     

Greenhouse Gas Emissions Payback for Lightweighted Vehicles Using Aluminum and High‐Strength Steel

In this article we consider interactions between life cycle emissions and materials flows associated with lightweighting (LW) automobiles. Both aluminum and high‐strength steel (HSS) lightweighting are considered, with LW ranging from 6% to 23% on the basis of literature references and input from industry experts. We compare the increase in greenhouse gas (GHG) emissions associated with producing lightweight vehicles with the saved emissions during vehicle use. This yields a calculation of how many years of vehicle use are required to offset the added GHG emissions from the production stage. Payback periods for HSS are shorter than for aluminum. Nevertheless, achieving significant LW with HSS comparable to aluminum‐intensive vehicles requires not only material substitution but also the achievement of secondary LW by downsizing of other vehicle components in addition to the vehicle structure. GHG savings for aluminum LW varies strongly with location where the aluminum is produced and whether secondary aluminum can be utilized instead of primary. HSS is less sensitive to these parameters. In principle, payback times for vehicles lightweighted with aluminum can be shortened by closed‐loop recycling of wrought aluminum (i.e., use of secondary wrought aluminum). Over a 15‐year time horizon, however, it is unlikely that this could significantly reduce emissions from the automotive industry, given the challenges involved with enabling a closed‐loop aluminum infrastructure without downcycling automotive body structures.     

How Much Sorting Is Enough

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.