An Assessment of Environmental Sustainability of Non-Fuel Mining and Mined Materials in the U.S.

The concept of “sustainable mining” has been examined and acted upon by the industry since the 1990s, with focus on reducing the environmental footprint of mining in terms of energy consumption, water consumption, waste production, and other metrics. Despite these efforts, mined materials continue to have an ever-increasing environmental footprint, as the amount of material mined has increased with population and economic growth; waste production has increased with the transition to open pit mining from underground mining; and energy, water, and reagent use have increased as ore grades continue to decline, resulting in more greenhouse gas emissions and both water and soil pollution. This work investigated approaches for meeting current and future demand for non-fuel minerals – specifically using copper as a case study – in a more sustainable manner. Specific objectives of the research were to: establish a framework for sustainable mining that incorporates circular economy concepts; develop a model to represent stocks and flows of a mined material – copper - in the U.S.; identify and model future scenarios and assess their circularity; and finally to evaluate environmental sustainability for scenarios in the sustainable mining framework, accomplished in three chapters. These specific objectives all relate to the broader question of how much raw extractive mining is necessary to meet demand.
Several original contributions were accomplished in this research. The first is the completion of a review of existing works and initiatives in the area of sustainability and mining, including identification of an emerging field integrating circular economy concepts (circularity) and resource efficiency. This shift from environmental footprint metrics to considerations of circularity is necessary for future reduction of the major environmental impacts associated with increasing mining rates, inputs, land disruption, outputs, and closure, and also to also extend the lifetime of existing minerals reserves and resources. A framework for sustainable mining is proposed synthesizing metrics of circularity and environmental sustainability. Secondly, primary end-of-life management data were collected for copper in the U.S., providing a basis for evaluation of other datasets currently used in material flow analyses that do not use primary data or a bottom-up approach. A material flow analysis was performed for U.S. copper from 1970-2015 using these primary data and revealed a major accumulation of copper in the use phase – of which 20-40% is estimated as a potential hibernating stock for recovery and reuse going forward. Buildings and construction materials as well as electric utility equipment were identified as the largest and most readily available sources or recoverable copper of the four use phases considered. Thirdly, relationships between key drivers and major copper material flows via regression analysis were identified. These relationships were used to provide a long-term forecast for the copper life cycle in the U.S. Also, the identified relationships were employed in analysis of scenarios to assess qualitatively the circularity of the copper life cycle as it is modified by changing drivers. Finally, both circularity and environmental sustainability metrics were applied to assess quantitatively the copper life cycle and development of baseline indicators for comparisons. Results from evaluation of the scenarios demonstrate that a shift in copper demand driver growth in either direction, positive or negative, would result by 2030 in dramatic changes within the material flow system boundary, and that population dynamics appears to be the most significant driver affecting the complete life cycle of copper in the U.S.