How Much Does a Gold Cyanidation Plant Really Cost?

Investing in a gold cyanidation plant, whether Carbon-in-Leach (CIL) or Carbon-in-Pulp (CIP), represents a significant step towards high-recovery, industrialized gold production. However, the question of cost is complex, moving far beyond a simple equipment price tag. The total investment is a multi-faceted sum of direct capital expenditure (CAPEX), ongoing operational expenditure (OPEX), and crucial "soft" costs related to compliance and sustainability. This guide provides a detailed framework for budgeting a small to medium-scale cyanidation plant (5-50 tonnes per day), breaking down the true cost drivers.

I. Capital Expenditure (CAPEX): The Foundation Investment

CAPEX encompasses all one-time costs to design, procure, and construct a functional plant. For a cyanidation circuit, it is typically the largest financial hurdle.

1. Process Plant & Equipment (40-60% of Total CAPEX)

This is the core cost, highly dependent on throughput, ore hardness, and automation level.

• Crushing Circuit: Jaw crusher, cone crusher, screens, conveyors. Cost Range: $50,000 - $200,000+.
• Grinding Circuit: Ball mill, classifier (hydrocyclone), pumps, feeding system. The mill is often the single most expensive item. Cost Range: $150,000 - $500,000+.
• Leaching & Adsorption Circuit: Agitated leach tanks (CIL/CIP tanks), efficient agitators, inter-tank screens, carbon transfer system. Tank size and number (dictated by required retention time, typically 24-48 hours) are major cost drivers. Cost Range: $200,000 - $800,000+.
• Elution, Electrowinning & Smelting: Strip vessel, electrolyte heater, electrowinning cells, rectifier, fume hood, and induction smelting furnace. Cost Range: $80,000 - $250,000.
• Carbon Handling & Reactivation: Carbon regeneration kiln (if on-site reactivation is chosen). Cost Range: $50,000 - $150,000.
• Process Piping, Instrumentation & Controls: High-density polyethylene (HDPE) piping, valves, flowmeters, pH/ORP probes, and a basic PLC/SCADA control system. Cost: Often 15-25% of equipment cost.

2. Civil Works & Structural Steel (20-30% of Total CAPEX)

• Site Preparation: Clearing, leveling, drainage.
• Foundations: Massive concrete foundations for mills and tanks.
• Buildings & Structures: Mill shed, process plant structure, gold room (high-security), reagent storage bays.
• Tailings Storage Facility (TSF) Starter Dam & Lining: A critical, non-negotiable cost. Includes engineered dam construction and often a geomembrane liner.

3. Infrastructure & Utilities (10-20% of Total CAPEX)

• Power Supply: Transformer, distribution, cabling. Cost spikes if off-grid generators are required.
• Water Management: Boreholes, pumps, pipelines, water storage dams, and water treatment systems for recycling.
• Reagent Handling: Cyanide mixing and dosing system, lime silo, safety showers/neutralization kits.

4. Engineering, Procurement, & Construction Management (EPCM) (8-12% of Total CAPEX)

Professional fees for detailed plant design, equipment sourcing, construction supervision, and commissioning. Never underestimate this cost; poor design is infinitely more expensive.

5. Contingency (10-15% of Total CAPEX)

A mandatory budget reserve for unforeseen costs, price escalations, and scope changes.

Total CAPEX Estimate: For a 20 tpd plant with moderate complexity, a rough order-of-magnitude estimate is $1.5 million to $3.5 million. A 50 tpd plant can range from $3.5 million to $7 million+. These figures are highly sensitive to location, ore characteristics, and chosen equipment quality.

II. Operational Expenditure (OPEX): The Cost of Production

OPEX determines your break-even grade and long-term profitability.

1. Consumables & Reagents (Largest OPEX Component)

• Cyanide (NaCN or KCN): Usage depends on ore mineralogy (presence of cyanicides like copper). Can range from 0.5 to 3.0 kg/tonne of ore.
• Lime (CaO): For pH control (maintained at 10.5-11.0). Consumption can be 2-10 kg/tonne.
• Activated Carbon: Make-up cost for carbon losses (typically 10-50 grams per tonne of ore). High carbon activity is crucial for efficiency.
• Steel Grinding Media & Mill Liners: Highly abrasive ores can incur costs of $3-$10 per tonne of ore milled.
• Power: Grinding is the largest consumer. A 20 tpd plant may require 100-200 kW continuous load.

2. Labor

Skilled plant supervisor, metallurgist, operators, maintenance technicians, and security for the gold room. Labor costs vary drastically by region.

3. Maintenance & Spares

Typically budgeted as 3-5% of total plant CAPEX annually. Critical spares (pump impellers, crusher jaws, mill liners) must be in stock.

4. Tailings Management & Environmental Compliance

• Ongoing TSF monitoring, water treatment for cyanide destruction (using SO2/Air or H2O2 processes), and environmental reporting.
• Insurance: Liability and environmental impairment insurance are essential and costly.

5. General & Administrative (G&A)

Office costs, administration, assaying fees, and regulatory fees.

OPEX Estimate: For a 20 tpd plant, all-in sustaining costs (AISC) can range from $80 to $150 per tonne of ore processed. The gold grade required to break even is calculated as: Break-even Grade (g/t) = (AISC per tonne / Gold Price per gram). At $80/tonne OPEX and $65/gold gram, the break-even grade is ~1.23 g/t.

III. The Hidden Costs: Compliance, Risk, and Sustainability

These "soft" costs can make or break a project.

1. Pre-Production Licensing & Feasibility

• Metallurgical Testwork: Locked-cycle CIL tests are essential for recovery predictions and flow sheet design. Cost: $20,000 - $50,000+.
• Environmental & Social Impact Assessment (ESIA): A mandatory requirement for permitting. Cost: $50,000 - $200,000+.
• Permitting & Licensing: Can take 12-24 months and involve significant legal and consulting fees.

2. The Cyanide Factor: A Cost Multiplier

• International Cyanide Management Code (ICMC) Compliance: Adherence is often required for financing and social license. It imposes strict standards for handling, transportation, emergency response, and decommissioning.
• Security & Safety Infrastructure: Cyanide storage requires a secure, bunded, and monitored area with neutralization systems. Worker training and medical preparedness are mandatory.
• Closure Bonding: Regulators often require a financial bond to cover future cyanide detoxification and site rehabilitation.

3. Working Capital

Funds to cover 3-6 months of OPEX before the first gold pour and revenue generation. This is a critical liquidity requirement often overlooked.

IV. Key Cost Optimization Strategies

• 1. Ore Knowledge is Financial Knowledge: Comprehensive testwork prevents over- or under-engineering the plant. Optimizing grind size and leach retention time directly reduces CAPEX and OPEX.
• 2. Design for Efficiency, Not Just Capacity: Invest in energy-efficient motors, optimized tank design, and carbon management systems. Higher initial cost often leads to far lower lifetime OPEX.
• 3. Embrace Modular/Containerized Designs: For smaller plants (<30 tpd), pre-assembled modules can reduce civil works and construction time, lowering overall CAPEX and accelerating time-to-revenue.
• 4. Plan for Water Recycling from Day One: A closed-water circuit minimizes fresh water costs, reduces tailings dam volume, and simplifies environmental permitting.
• 5. Factor in Full Life-Cycle Costs: The cheapest equipment quote often leads to the highest maintenance cost and lowest availability. Choose reliability over low upfront price.

Total Cost of Ownership

The cost of a gold cyanidation plant is the Total Cost of Ownership (TCO): the sum of CAPEX, OPEX, compliance costs, and risk mitigation over the project's life.

While the capital outlay is substantial, the economic driver is the net gold recovered. A well-designed, efficiently operated plant processing ore at a grade significantly above its break-even point can be highly profitable. The ultimate goal is not to build the cheapest plant, but to build the most cost-effective one—where robust engineering, intelligent design, and strict operational control ensure that every dollar of cost yields the maximum possible return in recovered gold. Failure to account for the full spectrum of costs detailed here is the single greatest financial risk in developing a cyanidation project.