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Near-zero-waste recycling of low-grade sulphidic mining waste for critical-metal, mineral and construction raw-material production in a circular economy

Periodic Reporting for period 3 - NEMO (Near-zero-waste recycling of low-grade sulphidic mining waste for critical-metal, mineral and construction raw-material production in a circular economy)

Reporting period: 2021-05-01 to 2022-11-30

With an estimated volume of 600 Mtonne/yr and a historic stockpile of 28,000 Mtonne, sulphidic mining waste from the production of Cu, Pb, Zn and Ni, represents the largest volume of extractive waste in Europe. When poorly managed, these “tailings” may cause major environmental problems such as acid mine drainage. In 2016 EIP Raw Materials launched a “call to arms” to transform the “extractive-waste problem” into a “resource-recovery opportunity”, as “tailings” still contain valuable & critical metals. Using a “4 PILOTS – 2 case-studies” concept, NEMO develops, demonstrates and exploits, therefore, new ways to valorize sulphidic mining waste. The 3 cases are the Sotkamo Ni-Co-Zn-Cu mine in Finland and the Luikonlahti processing facility in Finland and the Tara mine in Ireland; the 4 PILOTS are located at key points in the near-zero-waste flowsheet, encompassing the recovery of valuable & critical metals, the safe concentration of hazardous elements, the removal of sulphur as sulphate salts, while using the residual mineral fraction in cement, concrete and construction products.
Two bioleaching options were benchmarked in Sotkamo: bioleaching heap with enhanced operating conditions and bioleaching pond. Promising results were obtained from the demonstration of the pond bioleaching option with metal extraction above 90%, and fast leaching kinetics similar to kinetics achieved in conventional bioleaching stirred tank reactor. The enhanced heap pilot was operated during two years and provided novel and useful data on heap sizing and bacterial physiology and activities in heap leaching. In parallel to pilot operation, several complementary numerical models were developed in order to tackle the complexity of the biochemical mechanisms involved in both bioleaching processes to provide robust scale-up rules for a future application of NEMO bioleaching options at industrial scale. The models were used in particular to provide the data required to assess the economic and environmental assessments.
Several hydrometallurgical processing routes were evaluated for sulphidic tailings from the Boliden Luikonlahti site with Co, Ni and Cu as the main target elements. The routes included tank bioleaching, acid pre-leaching combined with bioleaching under atmospheric conditions, as well as pressure leaching in alkaline and neutral media. Lab and pilot scale studies were complemented by numerical simulation of pond bioleaching. Results have been promising with high metal recoveries and good concentrate grades both in the leaching process and in the downstream operations producing battery-grade products. The feasibility of producing additional byproducts such as iron, sulphates and gypsum, as well as regeneration of reagents in the processes was also investigated. Economic evaluation of the processes showed possible business cases both for the target products as well as for some of the prospective byproducts.
Pilot operations also included improved sulphide precipitation of multi-metal leach solutions, separation and purification of rare earth elements (REE), additional metal recovery processes and pressure leaching of mixed sulphide concentrate. Results show high selectivity and recovery yields in sulphide precipitation and efficient re-leach of sulphide products in pressure oxidation. Heavy REEs were successfully recovered from leachates and were separated in Tm-group and Dy-group REE products.
Promising results were obtained with tailings from Boliden's Tara mine. The material can be used both as SCM (supplementary cementitious material) and as synthetic aggregate. Calcination is required to improve product quality. Granulation is possible with low cement addition. Tests on mortar prisms and concrete trials showed that appreciable amounts of the tailings could be used. In the next phase, these results will be tested on an industrial scale.
Guidelines on CODE-compliant sampling were completed for the tailing storage sites recommending sampling methods, sample preparation and analysis. A working interface for the NEMO pilots has been developed, allowing to efficient operate the integrated pilots from a holistic point of view and to robustly operate the integrated pilot allowing a heterogeneous and variable feedstock. List of mining sites for result’s replication has been established where 3 case studies have been used for a feasibility analysis.
New, comprehensive sustainability assessment framework based on life-cycle-based indicators has been developed tailored for the case of mine residues valorization. The results of the framework can supply policy and decision-makers with an overview of several aspects linked to the sustainability of SMRs valorisation projects and identify the most important sustainability hotspots.
A stakeholder analysis of the two mining companies was carried out. Data from the local meetings that the mining companies hold with their stakeholders has been gathered and systematically analysed. A high-level expert panel has been established comprising a diverse group of experts to discuss the various aspects of recycling mining waste and the Social License to Operate at each meeting. The second video was produced, and it was released in October 2022. The video was filmed at various locations including a pilot plant and mine in Sweden, as well as during tests of concrete production by project partners. The market potential has been analysed, and exploitation plans for the NEMO innovations have been defined.
NEMO demonstrated new processes and flowsheets at three specific case studies: the Sotkamo mine in Finland, the Luikonlahti processing plant in Finland and Tara mine in Ireland. NEMO also plans to replicate the results in other locations in Europe and beyond. A comprehensive list of potential replication sites was compiled and a study on the feasibility of replicating technologies at three sites was conducted. Further steps to exploit the results will vary depending on the final outcome achieved and may include further in-house development and implementation of technologies, contract research or applying for additional funding to improve the technologies or to build industrial pilots.
To achieve maximum impact, the NEMO project made a concerted effort to disseminate project results and communicate with the public. After the project concludes, the NEMO website will continue to serve as a primary source for sharing project results and updates at A variety of videos were produced during the project and the project was active on LinkedIn. A symposium was organized bringing together representatives from the R&D community in the field of extractive waste recycling, and proceedings and presentations from the symposium can be found at NEMO publications that have undergone peer review, as well as selected presentations from various events, can be found on the website Public deliverables, including results from the NEMO high-level stakeholders panel on social license to operate, will be shared on the NEMO website at At the NEMO closing event during the EU Raw Materials Week 2022, an overview of the project's outcomes was presented and these presentations are available on the project website at