Rock-to-Metal Ratio: A Foundational Metric for Understanding Mine Wastes

The quantity of ore mined and waste rock (i.e., overburden or barren rock) removed to produce a refined unit of a mineral commodity, its rock-to-metal ratio (RMR), is an important metric for understanding mine wastes and environmental burdens. In this analysis, we provide a comprehensive examination...

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Bibliographic Details
Published in:Environmental science & technology 2022-05, Vol.56 (10), p.6710-6721
Main Authors: Nassar, Nedal T., Lederer, Graham W., Brainard, Jamie L., Padilla, Abraham J., Lessard, Joseph D.
Format: Article
Language:English
Subjects:
Aluminum
Cobalt
Commodities
Copper
Copper ores
Emissions
Energy requirements
Evaluation
Gold
Greenhouse gases
Heavy metals
Iron
Iron compounds
Iron ores
Life cycles
Mine tailings
Mine wastes
Minerals
Mining
Overburden
Rocks
Sustainable Systems
Wastes
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Summary:The quantity of ore mined and waste rock (i.e., overburden or barren rock) removed to produce a refined unit of a mineral commodity, its rock-to-metal ratio (RMR), is an important metric for understanding mine wastes and environmental burdens. In this analysis, we provide a comprehensive examination of RMRs for 25 commodities for 2018. The results indicate significant variability across commodities. Precious metals like gold have RMRs in the range of 105–106, while iron ore and aluminum are on the order of 101. The results also indicate significant variability across operations for a single commodity. The interquartile range of RMRs for individual cobalt operations, for example, varies from 465 to 2157, with a global RMR of 859. RMR variability is mainly driven by ore grades and revenue contribution. The total attributable ore mined and waste rock removed in the production of these 25 commodities sums to 37.6 billion metric tons, 83% of which is attributable to iron ore, copper, and gold. RMRs provide an additional dimension for evaluating the impact of materials and material choice trade-offs. The results can enhance life cycle inventories and be extended to evaluate areas of surface disturbances, mine tailings, energy requirements, and associated greenhouse gas emissions.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.1c07875