Copper supply crisis as sulfur management challenge: process options for engineers
Reviewed by Joe Ashwell
First reported on MINING.com
30 Second Briefing
China’s sudden halt of sulfuric acid exports, after shipping 4.65 million tonnes in 2025 (about 40% from metal smelters), has doubled delivered acid prices to Chile since February and is squeezing heap-leach copper operations in Chile, the DRC and Zambia. Randy Allen argues that for each tonne of copper from sulfide concentrates, 3–3.5 tonnes of sulfuric acid can be generated and monetised, alongside co-products such as ferrous sulfate and iron oxides. He points to pressure oxidation and electrochemical reductive leaching as non-combustion routes to capture copper and fully valorise sulfur, cutting SO₂ emissions and acid mine drainage risks.
Technical Brief
- Global sulphuric acid output exceeds 260 Mt/y, with ~60% consumed by phosphate fertiliser production.
- China built nearly half of global copper smelting capacity, with ~40% of its acid exports from smelters.
- Closure of the Strait of Hormuz, Russia’s export ban extension, and Turkish/DRC curbs simultaneously constrain sulphur flows.
- Chile relies on >1 Mt/y of imported Chinese acid specifically for heap-leach copper circuits.
- Conventional sulphide processing routes push most sulphur into tailings, waste rock and off-gas, driving long-term AMD liabilities.
- Smelting-based containment still requires scrubbers, lined tailings, water treatment and SO₂-to-H₂SO₄ plants, costing billions in mitigation CAPEX/OPEX.
- Pressure oxidation and electrochemical reductive leaching are cited as non-combustion options to convert sulphides into saleable sulphur products.
- Reframing sulphur as a co-product enables polymetallic-style project economics: copper, acid, elemental sulphur, ferrous sulphate, iron oxides and precious metals.
Our Take
With heap-leach operations in Chile accounting for roughly 20% of global copper output, the recent doubling of sulfuric acid prices into Chile signals disproportionate margin and volume risk for leach-heavy producers compared with sulphide-concentrate smelter routes elsewhere.
Given that 60% of global sulfuric acid goes to fertiliser manufacture, any sustained diversion of acid towards copper leaching would likely tighten phosphate fertiliser supply, creating an indirect cost and food-security angle that policymakers in fertiliser‑reliant regions such as the Middle East and parts of Africa will need to factor into critical minerals strategies.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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