Nachhaltige Rückgewinnung von Rohstoffen aus buntmetallhaltigen Aufbereitungsrückständen : Ein Bewertungs- und Klassifizierungsansatz konform mit der Vorratsrahmenklassifikation für Rohstoffe der Vereinten Nationen (UNFC) zur Identifizierung von Potenzialen und Barrieren zur Projektentwicklung

  • Sustainable raw materials recovery from base metal tailings : an assessment and classification approach compliant with the United Nations Framework Classification for Resources (UNFC) to identify potentials and barriers of project development

Suppes, Rudolf; Lottermoser, Bernd G. (Thesis advisor); Greiff, Kathrin (Thesis advisor)

Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022


In general, mineral raw materials (RMs) are assessed and classified to demonstrate the viability of their exploitation to potential investors. The assessment and classification of anthropogenic RMs such as base metal tailings is currently lacking a systematic and transparent approach which considers all dimensions of sustainability. Hence, the potentials of RMs recovery from base metal tailings are widely unknown and cannot be compared to the ones of other RM sources. The conventional RMs classification with the Committee for Mineral Reserves International Reporting Standards (CRIRSCO) principles from the primary mining industry is focussed on techno- economic aspects. To enable the assessment of a RMs recovery project’s sustainability, environmental and social aspects need to be included. This can be done by applying the United Nations Framework Classification for Resources (UNFC) principles. To the knowledge of the author of this thesis, this is the first systematic application of the UNFC to base metal tailings which considers all dimensions of sustainability. The main research question is: which aspects should be considered in the assessment and classification of base metal tailings to enable a sustainable raw materials recovery? The main research question is answered with the help of 3 published peer-reviewed scientific articles summarised further below. The main research goal is to develop a systematic, transparent and UNFC-compliant assessment and classification approach for (Stage 1) a desk-based screening of tailings storage facilities (TSFs) to quickly identify potentially viable RMs recovery projects, and (Stage 2) for a consecutive assessment of project sustainability based on on-site exploration data. The developed assessment and classification approach is applicable to base metal tailings from industrial processes. A project’s development status is differentiated in terms of geological, technological, economic, environmental, social and legal aspects. Established methods from the conventional mineral RMs classification under the CRIRSCO are combined with methods to account for environmental and social potentials and barriers. In addition, it is demonstrated why tailings in general should be assessed and classified as anthropogenic RMs, what the drawbacks of the sole application of CRIRSCO principle from the primary mining industry to base metal tailings are, how a classification under the UNFC remedies these aspects, and where the current UNFC concept should be developed with respect to guidelines for an anthropogenic RMs assessment. Lastly, recommendations are made for the further development of the developed assessment and classification approach, as well as for the further development of the UNFC as a base for an integrated and sustainable RMs management system. First article: the current UNFC concept is tested for its applicability to base metal tailings with the case study TSF Cabeço do Pião (Portugal) from a private mining company’s perspective with economic focus within a very preliminary study. One rehabilitation scenario, and two RMs recovery scenarios with low and high degree of tailings valorisation are assessed. The necessity for actions to protect human health and the environment is shown with a risk assessment. With a discounted cash flow analysis, under consideration of mineral price uncertainty, the project’s economic viability is indicated. The application of the UNFC principles exemplifies the advantages over an application of the CRIRSCO principles: TSF rehabilitation is identified as a necessary base case and positive socio-environmental acting are prioritised. However, the RMs recovery scenarios cannot be differentiated with the current UNFC Classes. The assessment reveals the necessity for a stronger user guidance in the assessment and classification process. Moreover, a more detailed Subcategorisation is required to identify project potentials and barriers, particularly in social and environmental domains. Second article: a desk-based approach for a first quick, systematic and UNFC-compliant TSF screening is presented. The assessment of specified criteria can support the user of the approach in deciding if a particular TSF should be assessed in a more advanced study including costly on-site exploration. The user is guided in compiling information on a TSF at local scale in a structured manner. The approach is tested with the case study TSF Bollrich (Germany). It is situated in a complex environment close to various stakeholders and ecologically sensitive areas. The case study demonstrates that a preliminary quick assessment based on publicly accessible information is possible. The developed desk-based screening approach can help to create a TSF inventory in the future which captures project potentials and barriers under consideration of all dimensions of sustainability. Since the assessment of base metal tailings with the CRIRSCO principles neglects relevant aspects, it is concluded that tailings should be considered as anthropogenic RMs. Third article: an approach for a practical UNFC-compliant assessment of project sustainability based on on-site exploration data is presented and tested with the case study TSF Bollrich. It is shown how to develop a project from first on-site exploration to a decision whether to intensify costly on-site exploration. The development status of the overall project and the recovery of individual RMs is differentiated. For an easy comparison of the assessment results across different studies, they are summarised in a heat map-like categorisation matrix. It is concluded that with a UNFC-compliant assessment and classification approach, aspects which contribute to a local sustainable development can be identified and communicated transparently. This can serve for stakeholders as a basis for a discussion on how to derive a commonly acceptable solution. The approach presented in this thesis supports the integration of the United Nations Sustainable Development Goals (UN SDGs) into RMs classification. Overall, the following conclusions are drawn: (1) Economic, environmental, social, and legal aspects on a RMs deposit’s classification should be differentiated to so that they become equally important, and their individual development status and individual influence on the classification result becomes transparent; (2) currently uneconomically recoverable RMs deposits with a future potential should be considered for a transparent communication, as well as all contained RMs including potentially contained contaminants and their impacts; (3) local stakeholders should be identified from the beginning of project development to anticipate possible social tensions; (4) site-specific benefits and risks of RMs recovery should be considered and communicated transparently from the beginning of project development; and (5) barriers to RMs recovery from base metal tailings should always be investigated beside the potentials so that market actors can better evaluate the sustainability of an investment.


  • Division of Mineral Resources and Raw Materials Engineering [510000]
  • Chair of Sustainable Raw Materials Extraction and Institute of Mineral Resources Engineering [511110]