Reprocessing of mining waste: combining environmental management and metal recovery?

Abstract

Raw materials are essential for the sustainable functioning of modern societies. Access to and affordability of mineral raw materials are crucial for the sound functioning of the European Union's economy. The increasing demand for raw materials raises growing concerns regarding mineral resources and especially metals availability. Furthermore, many metals, metalloids or rare earth elements that had no application in the past are now used for the manufacture of high added-value products, especially in the domain of new and green technologies. Many of them are by-products of base metals production, and their reserves are very limited. Therefore a list of strategic and critical materials was established by the European Commission in 2010. Following the rich mining history of France, there are currently some 300 mineral deposits mined or significantly explored. These are the source of large quantities of ‘tailings’ (gangue, processing waste resulting from concentration or hydrometallurgical treatment, slag, heap). The European Directive 2006/21/EC of 15 March 2006 on the management of waste from extractive industries oversees the permit conditions, storage, monitoring and control of mining waste to ensure the protection of human health and the environment. The member states have to carry out and periodically update an inventory of closed waste facilities that cause or have the potential to cause a serious threat to human health or the environment. Moreover, the directive encourages the recovery of extractive waste by means of recycling, reuse or reclamation. Following this, an inventory was finalised in France in 2012 in which 2,100 metallic and 1,300 coal tailings were identified and prioritised according to their potential impacts on groundwaters, surface waters, soils and human health. Among these, 53 sites with major environmental issues were listed. These sites are and will be the subject of specific actions (environmental and sanitary studies, works of rehabilitation) in order to reduce their long-term impact on both human health and environment. While metallic elements present in the tailings are by nature nondegradable, these actions require long-term approaches. The paper focuses on one of these sites, former Pb-Ag mines, where operations have led to the production of 200,000 m3 of mining waste. A French Geological Survey (BRGM) rehabilitation programme, based on environmental studies, was designed to stop additional tailings erosion towards the river and the surrounding areas and to avoid any contacts between the contaminated materials and the population. Metals recovery could be envisaged to mitigate the remediation cost. Indeed, old waste deposits related to past mining and metallurgical activities can be considered as significant reserves of valuable metals because the latter were not exploited or because economically recoverable metals may remain. In France, a recently started project handled by BRGM is aimed at identifying interesting old mining wastes deposits at the national level and assessing the metal recovery potential of these dumps. In a first step, it focuses on previous sites to be rehabilitated. The objective is to develop a methodology combining mining wastes environmental management and economic valorisation in a long-term perspective.