811 grinding media measured in kg/t and liners based on replacement schedules and material inventories—the analysis expands from a single-channel to a multi-channel carbon KPI that remains directly comparable across optimization scenarios. Even when consumable consumption is constant across scenarios, their absolute contribution significantly affects total carbon intensity. The results indicate that scenario differentiation based solely on electricity may change when consumables are included. Operating options that appear favourable from a kWh/t perspective may lose their relative advantage when material-related emissions are considered, while scenarios with slightly higher energy demand may remain competitive if consumable intensity is lower. The choice of functional unit (FU) is central to interpretation. In this study, kg CO₂e per ton of ore processed was appropriate for a grinding circuit optimization focused on throughput and energy efficiency. Overall, treating carbon intensity as an operational KPI, rather than solely as a reporting metric, enables meaningful side-by-side evaluation of production, energy, and sustainability performance across optimization scenarios. Consumables serve as a critical interface between processing and sustainability. This result shows that carbon performance in mineral processing goes beyond energy efficiency. While optimisation reduces specific energy consumption, incorporating grinding media and mill liners reveals a structural emissions baseline that limits proportional carbon reductions. Sensitivity analysis across different electricity grids indicates that as power systems decarbonise, the relative significance of Scope 3 emissions increases substantially. Therefore, sustainable mineral processing requires life-cycle-based carbon metrics that extend beyond energy indicators and explicitly account for material intensity. In the context of delivering the minerals the world urgently needs - faster. smarter and responsible - embedding these metrics within routine optimisation supports production decisions aligned with both performance and decarbonisation objectives. ACKNOWLEDGEMENTS The authors acknowledge the support of their organisations and colleagues. This work reflects collaboration between Metso and the University of Queensland, combining operational and academic perspectives to develop a technically grounded and practical approach. REFERENCES 1. Napier Munn, T. (2015). Is progress in energy efficient comminution doomed? Minerals Engineering, 73, 1–6. 2. Norgate, T., & Haque, N. (2010). Energy and greenhouse gas impacts of mining and mineral processing operations. Journal of Cleaner Production, 18(3), 266–274. 3. IEA (2025). Electricity 2025 - Emissions. International Energy Agency. 4. Ember (2024). Global Electricity Review 2024. Ember Climate 5. European Commission. Corporate Sustainability Reporting Directive (CSRD). 6. European Commission (2023). European Sustainability Reporting Standard (ESRS) E1: Climate Change. 7. ICMM. Scope 3 Emissions Accounting and Reporting Guidance. 8. Segura Salazar, J., Lima, F.M., & Tavares, L.M. (2019). Life Cycle Assessment in the minerals industry: Current practice and integration with process simulation. Journal of Cleaner Production, 232, 174–192. 9. ISO 14040:2006. Environmental management - Life cycle assessment - Principles and framework. 10. ISO 14044:2006. Environmental management - Life cycle assessment - Requirements and guidelines. 11. Azadi, M., Northey, S., Ali, S.H., & Edraki, M. (2020). Transparency on greenhouse gas emissions from mining to enable climate change mitigation. Nature Geoscience, 13, 100–104. 12. Kanchibotla, S., Valery, W., & Morrell, S. (1999). Modelling and simulation of integrated mine-tomill optimisation strategies. In Proceedings of the 6th Mill Operators’ Conference. AusIMM.
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