Urban infrastructure mines: on the economic and environmental motives of cable recovery from subsurface power grids

Subsurface power grids constitute one of the largest copper stocks in many industrialized cities. Over time, parts and zones of these systems have been continuously disconnected and abandoned, resulting in the emergence of urban infrastructure ores. This study aims to assess how current conditions and practices influence economic and environmental motives of cable recovery from such power grids. By applying an infrastructure manager’s perspective and evaluating 16 scenarios involving different extraction technologies and procedures, surface materials, urban locations and types of cables, we identify key areas where solutions or changes to increase incentives for cable recovery are needed. The assessed scenarios display significantly different cable extraction costs, where excavation in city centers with asphalt or cobblestone pavements generates the highest costs while greenbelts offer the best conditions. In most cases, cable revenues are not even close to outweighing the extraction costs. This is especially true for paper-coated cables or cables with aluminum conductors, for which the revenues are much lower than for plastic-insulated copper cables. Although economic conditions could be improved by integrating cable recovery to regular system upgrade projects or by applying non-digging technologies, clear incentives rely on the cable in question being especially valuable. Most of the cable recovery scenarios display environmental motives in terms of net savings in GHG emissions due to metal recycling. In contrast to the economic results, recycling of aluminum power cables is here more awarding than that of corresponding copper cables. We conclude that under current conditions urban mining does not make economic sense to infrastructure managers unless it is integrated as an added value to system upgrade projects. Apart from such re-arrangements in infrastructure provision, several other practice-related changes to cut cable extraction costs are possibly within reach for the managers. Still, an economically motivated practice relies on several external performance drivers such as market diffusion of non-digging technologies, improved cable recycling processes, and increased scrap metal prices. Our conclusion that the arguments for urban mining are currently more environmental than financial, points towards changed perspectives where such activities are seen as a way for infrastructure managers to contribute to societal goals such as climate change mitigation and reduced mineral resource dependence.