Current concerns about lack of diversity in supply of critical metals have spurred research into utilizing domestic sources, particularly from waste streams. Sustainability strategies like urban mining, industrial symbiosis, and the circular economy suggest avenues to realize new supplies of critical metals. In this work we explore the resource and economic potential for extracting rare earth elements (REEs) from industry byproducts (e.g. coal combustion products, red mud) and secondary sources (e.g. waste electronics and light bulbs). Combining materials flow analysis and characterization data, we find that while REE concentrations in waste and byproduct streams are mostly much lower than current REE ores, some secondary sources are richer than ores in high value REEs such as scandium. The quantities of REEs contained in secondary sources could meet current global demand even with low extraction yield rates. Phosphogypsum, coal ash and red mud from aluminum production stand out as promising candidates for recovery due to high concentrations of valuable REEs and sufficient quantities to potentially meet demand. Processes to extract REEs from secondary sources are under development, it is not yet clear which will be profitable at scale and which can be achieved at least environmental impact. This work provides high level guidance on the potential of secondary sources by characterizing quality (concentrations of different rare earths) and quantity (mass of rare earths in global scale wastes and byproducts). This significant first step helps clarify directions for policy and research and development investments.

当前对关键金属供应缺乏多样性的担忧促使人们开始研究利用国内资源，特别是来自废物流的资源。城市采矿，工业共生和循环经济等可持续发展战略为实现新的关键金属供应提供了途径。在这项工作中，我们探索了从工业副产品（例如，煤燃烧产物，赤泥）和二次资源（例如，废弃电子设备和灯泡）中提取稀土元素（REE）的资源和经济潜力。结合物料流分析和特征数据，我们发现尽管废物和副产品流中的REE浓度远低于当前的REE矿石，但某些次要来源却比high等高价值REE的矿石丰富。即使提取率低，二次资源中所含稀土元素的数量仍可以满足当前的全球需求。铝生产中的磷石膏，煤灰和赤泥是可回收的有前途的候选者，因为高浓度的有价值的稀土元素和足够的数量可以潜在地满足需求。从二次资源中提取稀土元素的方法正在开发中，目前尚不清楚哪种方法可以大规模获利，至少可以实现环境影响。这项工作通过表征质量（不同稀土元素的浓度）和数量（全球范围内的废物和副产品中的稀土质量）的特性，为二级资源的潜力提供了高级指导。重要的第一步有助于弄清政策和研发投资的方向。