U.S. industry practices and attitudes towards reprocessing mine tailings for metal recovery

Recovery of metals from mine tailings has the potential to reduce environmental liabilities and contribute to circular economy, but implementation is limited. This study uses three methods to examine the state of practice and identify knowledge gaps around tailings reprocessing: 1) a survey of Qualified Persons; 2) a review of U.S. Securities and Exchange Commission (SEC) filings; and 3) a review of the scholarly literature on tailings reprocessing. The survey of Qualified Persons shows that only a quarter of respondents, who are experts authorized to certify technical documents on mineral development in the U.S., have evaluated the reprocessing of tailings. In follow-up interviews, respondents emphasized the complexity of these considerations, encompassing geology, geochemistry, resource estimation, mineral processing, extractive metallurgy, economics, environmental science, and the social and regulatory context. The SEC filings provide an initial indication of the state of practice, showing that companies required to file in the U.S. have only conducted large-scale tailings reprocessing at 27 sites, mostly for gold, predicated on relatively little sampling or formal analysis of the tailings at the sites. The review of 98 scholarly journal articles on metal recovery from tailings shows that none incorporated more than two relevant disciplines. This study brings these three datasets together in a suggested workflow of 20 questions to guide for decision-making on tailings reprocessing, involving interdisciplinary understanding of the technical factors, the regulatory framework, and economic, environmental, and social impact.