Substantial amounts of post-consumer scrap are exported to other regions or lost during recovery and remelting, and both export and losses pose a constraint to desires for having regionally closed material cycles. To quantify the challenges and trade-offs associated with closed-loop metal recycling, we looked at the material cycles from the perspective of a single material unit and trace a unit of material through several product life cycles. Focusing on steel, we used current process parameters, loss rates, and trade patterns of the steel cycle to study how steel that was originally contained in high quality applications such as machinery or vehicles with stringent purity requirements gets subsequently distributed across different regions and product groups such as building and construction with less stringent purity requirements. We applied MaTrace Global, a supply-driven multiregional model of steel flows coupled to a dynamic stock model of steel use. We found that, depending on region and product group, up to 95% of the steel consumed today will leave the use phase of that region until 2100, and that up to 50% can get lost in obsolete stocks, landfills, or slag piles until 2100. The high losses resulting from business-as-usual scrap recovery and recycling can be reduced, both by diverting postconsumer scrap into long-lived applications such as buildings and by improving the recovery rates in the waste management and remelting industries. Because the lifetimes of high-quality (cold-rolled) steel applications are shorter and remelting occurs more often than for buildings and infrastructure, we found and quantified a tradeoff between low losses and high-quality applications in the steel cycle. Furthermore, we found that with current trade patterns, reduced overall losses will lead to higher fractions of secondary steel being exported to other regions. Current loss rates, product lifetimes, and trade patterns impede the closure of the steel cycle.

中文翻译：

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多个产品生命周期中报废钢的区域分布和损失-来自全球多区域MaTrace模型的见解。

大量的消费后废料被出口到其他地区或在回收和重熔过程中损失，出口和损失都对区域封闭材料循环的需求构成了限制。为了量化与闭环金属回收相关的挑战和权衡，我们从单个材料单元的角度考察了材料循环，并在多个产品生命周期中跟踪了一个材料单元。专注于钢铁，我们使用当前的工艺参数，损耗率和钢铁周期的贸易模式来研究最初包含在高纯度应用（例如对纯度要求严格的机械或车辆）中的钢铁随后如何分布在不同地区和产品组中例如对纯度要求不太严格的建筑。我们应用了MaTrace Global，这是一种以供应为驱动力的钢流多区域模型，再加上动态的钢用量模型。我们发现，根据地区和产品类别的不同，今天消耗的钢材中有多达95％会在该地区使用阶段直至2100年，而多达50％的钢材会因过时的库存，垃圾填埋场或炉渣堆而流失，直到2100.通过将消费后的废料转移到建筑物等长期使用的应用中，以及提高废物管理和重熔行业的回收率，可以减少因照常进行废料回收和再循环而造成的高额损失。与建筑物和基础设施相比，由于高质量（冷轧）钢应用的寿命更短且重熔发生的频率更高，我们发现并量化了钢循环中低损耗和高质量应用之间的折衷。此外，我们发现，按照当前的贸易模式，减少的总体损失将导致更多的二次钢被出口到其他地区。当前的损失率，产品寿命和贸易模式阻碍了钢周期的结束。