Re-mining of mine wastes in Germany: Challenges and opportunities

The Fraunhofer Institute for Environmental, Safety, and Energy Technology and the Helmholtz Institute Freiberg for Resource Technology (HIF) have together compiled a mine waste cadaster for Germany on behalf of the Federal Institute for Geosciences and Natural Resources (BGR). For this purpose, a wide variety of data sources was evaluated with the aim to create a national database able to provide an overview about the content of critical raw materials (CRM) in mine waste repositories in Germany. Yet, even though mine wastes containing economically significant amounts of CRM, re-mining these anthropogenic “ore bodies” faces considerable technical and non-technical challenges. Mine wastes often create environmental problems, such as acid rock drainage with associated high sulfate and heavy metal concentrations. This creates societal pressure for remediation. Remediation, however, is usually achieved by covering the surface with a water impermeable layer, an approach that is not sustainable, because of the required follow-up care and the inaccessibility of the resources that remain contained in the mine wastes. Besides that, legislative barriers are in conflict with recovering CRM and other metals and minerals from historic mine wastes. Many sites have essentially been abandoned since mining ceased in the 20th century. High metal contents and acidity released during sulfide oxidation has facilitated the establishment of a very specific flora and fauna. Species on these sites are often rare and strictly protected by environmental legislation. Metal recovery is all but impossible from such sites, despite the fact that acid rock drainage from these sites leads to environmental degradation downstream from the mine waste site. Another important aspect is the general lack of suitable beneficiation and metallurgical infrastructure in Germany. Large capital investment would thus be necessary to enable the recovery of strategic metals from historic mine waste. Even if high metal concentrations are present in some mine wastes, small volumes will render the set-up of large, stationary plants unfeasible. Instead, flexible and semi-mobile small-scale technologies need to be developed. Such technologies are, at present, not available on the market. To work at the intersection of society, legislation, remediation and re-mining is the aim of the new rECOmine partnership. This partnership is funded by the Federal Ministry of Education and Research (BMBF) for the next five years within the WIR! Program. It will be coordinated by HIF and build up three test sites in Saxony to develop combined remediation and re-mining technologies under real conditions with local partners