• higher direct OPEX, due to power, maintenance, and consumables associated with filtration and dry transport. However, integrated life-cycle analyses for conceptual Western Australian operations indicate that: • filtered tailings can become competitive or favourable when closure costs, water scarcity, land disturbance, and potential carbon pricing are fully internalised; • but in scenarios where energy costs are very high and carbon intensity is penalised, filtered options may rank less favourably unless conveyor-based haulage and efficient filter designs are adopted. Operationally, the main challenges include: • ensuring filter plant reliability at high throughput, • managing cake moisture variability, • designing robust materials handling and stacking systems, and • addressing dust and erosion at the stack surface. Co-Disposal of Tailings and Waste Rock Co-disposal (or co-mixing) blends tailings with waste rock to generate a composite material with improved geotechnical and hydraulic properties. Two distinct but related concepts appear in the literature: 1. Co-mixing (engineered blends): laboratory-designed mixes of waste rock and tailings, calibrated to achieve targeted hydraulic conductivity and mechanical strength. 2. Co-disposal using filtered tailings and coarse rejects: filtered tailings cake blended with coarse waste rock or aggregates, producing a material suitable for stacked or valley-fill type facilities with enhanced stability and lower permeability. Performance Characteristics Testing of co-mixed waste rock and tailings has shown that: • the addition of fine tailings can significantly reduce hydraulic conductivity compared with waste rock alone, • while maintaining adequate shear strength and resistance to erosion. Laboratory and pilot-scale work on co-disposing filtered cake with coarse rejects indicates that: • maintaining cake moisture near the optimum geotechnical range improves stability, • well-designed blends can reduce compaction and spreading effort, and • the resulting deposit can provide both mechanical support and barrier-like hydraulic performance. This makes co-disposal particularly attractive where acid rock drainage (ARD) risk is high, as the tailings component can limit oxygen ingress into sulphide-bearing waste rock. Cost and Practical Constraints Co-disposal introduces additional complexity in:
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