Urban Mining potential in local power grids: Hibernating copper and aluminium in Linköping
Power grids have a high content of metal, mainly copper and aluminium. When old cables reach their end-of-life, or in some way lose their intended purpose, they are usually left lying in their subsurface position. Material no longer used, but not yet discarded as waste, is in a state known as hibernation. Over time there is an accumulation of hibernating cables under ground that potentially could be recovered or 'mined'. The aim of this study is to examine the total hibernating metal content of an urban, subsurface power grid, how it is distributed and also what reasons for disconnection are the most common. The focus of the study is the power grid of Linköping. Using a GIS based variant of material flow analysis the hibernating metal stock is examined both in terms of size and spatial distribution. The results of the study show a significant amount of hibernating copper and aluminium; in total 240 tons of metal were identified. By comparing the results with previous studies both similar and differing patterns appear. The main differences lie in the distribution of the stock within the city which is affected by the characteristics of the cities. When examining the reasons for disconnection continuous repair and maintenance work seems to be the most common reason for disconnection of cables. Further studies on how the characteristics of a city affects the formation of hibernating metal stocks in the infrastructure are suggested.