805 lubricants, internal material handling, water management, and related shutdown interventions. These categories are not exhaustive, but they capture the main channels typically represented in concentrator-level life cycle inventories. All four channels are incorporated within the integrated operational–LCA inventory described in Section 2, where usage rates from process optimisation studies are combined with cradle-to-gate emission factors to calculate kg CO₂e per selected functional unit. 3.2 Limitations of kWh/t in Capturing Upstream Impacts kWh/t responds primarily to changes in comminution intensity and equipment efficiency. While essential, it does not capture how upstream emissions shift when operating conditions alter wear rate, reagent demand, corrosion behaviour, or maintenance frequency. For example, reductions in target grind size (P80) are generally associated with increased specific energy consumption. Finer grinding duty often coincides with higher grinding media and liner consumption per unit throughput due to increased power intensity, impact severity, abrasion, and/or corrosion effects influenced by slurry chemistry and water quality. These consumable-related emissions are not distinguishable within energy metrics alone and can represent a significant share of total CO₂e. Similarly, operation outside optimal slurry density ranges can alter pumping efficiency, mill breakage rates, and wear behaviour. While adjustments to grinding density and slurry rheology may improve process efficiency, trade-offs in media utilisation and liner life may arise due to additional stressors or corrosion-related wear. In such cases, apparent gains in kWh/t may not correspond proportionally to reductions in overall carbon intensity. These examples illustrate that energy-focused metrics capture only part of the system response. When energy-related emissions decrease, carbon intensity does not necessarily fall proportionally, as emissions may be redistributed toward non-energy channels. 3.3 Process Decisions and Their Carbon Response When the carbon footprint is expressed as kg CO₂e per functional unit, operational variables can be evaluated by their carbon response rather than by energy response alone. Within the integrated framework presented in Section 2, this response is calculated directly from the shared inventory, where electricity use, consumable wear rates, and service requirements are already tracked in standard optimisation studies. Key optimisation levers with multi-channel carbon effects include throughput (tph) and grind size (P80), which influence energy demand, media wear, liner life, and downstream flotation performance; percent solids, affecting pumping energy, slurry rheology, and mechanical wear; grinding media charge and size distribution, altering breakage efficiency and steel consumption; and coupling between grinding and flotation, governing mass pull, regrind intensity, and reagent consumption. Because these variables are already manipulated during routine scenario analysis, integrating carbon metrics does not require additional modelling layers. Instead, it reveals how existing decisions shift emissions between channels when evaluated against a consistent functional unit. 3.4 Illustrative Operational Examples of Carbon Responses The following simplified examples illustrate how common operating decisions affect both power demand and the distribution of carbon emissions across channels. Finer P80 targeting increases specific energy consumption and may also increase grinding media and liner consumption due to higher grinding duty. Aalthough the magnitude depends on mill type and operating conditions, these consumable-related emissions can become significant when evaluated alongside energy effects. Liner selection and maintenance also influence carbon response: liner material or profile and relining strategy alter charge trajectory, shifting throughput and specific energy across the liner life as documented in liner design references16. Embedded emissions from liner materials and relining frequency are rarely surfaced, but linking liner mass to cradleto-gate factors makes them visible. Similarly, improved grind–flotation coupling—such as a moderately coarser primary grind combined with improved flotation kinetics—can reduce regrind demand and total steel consumption, lowering overall kg CO₂e per unit of metal produced despite similar kWh/t values, consistent with integrated grind–float studies.¹⁷ These examples are illustrative rather than site-specific, but they reflect
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