Bioleaching: case studies and examples?

Bioleaching case studies

Bioleaching uses bacteria to metabolize insoluble sulfides and iron complexes. It produces 20% of the world’s copper, and other metals; with 50% lower capex, at least 50% less CO2 and up to 80-90% recoveries; but it is currently limited to specific mineralogies. An exciting prospect for the 2020s is that new technologies may unlock more minerals for bio-leaching. This data-file is an overview of 20 bioleaching case studies.

Bioleaching produces 20% of the world’s copper, and is also used in other metals, as naturally occurring bacteria – such as Acidobacillus ferrooxidans/thiooxidans – metabolize iron, and oxidize insoluble sulfides, releasing valuable metal ions into solution. From here, they can be concentrated via solvent extraction and refined via electrowinning.

The advantages of bioleaching are low costs and low CO2, as per broader heap leaching operations. The entire process likely costs $4,000-5,000/ton, which is approximately half the level of integrated mining-smelting operation. Avoiding smelting also avoids around 2 tons/ton of CO2 emissions, which is also around a 50% reduction (model here).

The technology is mature. This data-file tabulates over 20 examples. The first full-scale commercial success was 1982, with an acceleration in the 1990s. The median average size is small, at 20kTpa. But there are also world-scale operations using bio-leaching, such as BHP’s Escondida and Spence assets in Chile, both close to 200kTpa.

However mineralogy matters. Recovery rates average above c80%, when copper ores are chalcocites (Cu2S), covellites (CuS) and other easily leached minerals. Historically, these higher recovery rates have also been achieved on low-grade copper resources, averaging 0.5% copper, and sometimes as low as 0.3%.

Conversely, chalcopyrites (CuFeS2) make up over 70% of the world’s remaining copper resources and they cannot easily be leached, as a passivating layer forms at their surface. At best 20-25% recovery rates are reported when leaching chalcopyrite-heavy ores.

There is reason for excitement in the 2020s, as several companies are developing bio-leaching technologies that can recover copper from chalcopyrites. We have previously written about Jetti Resources. Rio Tinto has also developed a new process called Nuton. At best, CO2 may be 90% less than smelting.

20 bioleaching case studies are laid out in the data-file, as a useful overview, while we also see growing importance for metals and especially copper in our energy transition research.

Mine trucks: transport economics?

Mine Truck Economics

There are around 50,000 giant mining trucks in operation globally. The largest examples are around 16m long, 10m wide, 8m high, can carry around 350-450 tons and reach top speeds of 40mph.

This data-file captures the economics of a mine haul truck. A 10% IRR requires a charge of $10/ton of material, if it is transported 100-miles from the mine to processing facility. Assumptions can be stress-tested overleaf.

Fuel consumption is large, around 40bpd, or 0.3mpg, comprising around 30% of total mine truck costs at c$1.5-2/gal diesel prices. Some lower carbon fuels are c5x more expensive, and would thus inflate mined commodity costs.

High utilization rates are also crucial to economics, to defray fixed costs, which are c50% of total costs, as our numbers assume each truck will cover an average of 500 miles per day for c20-25 years.

Copper: leading producers?

Screen of copper producers

This data-file is a screen of the world’s largest copper miners and producers, covering 16 companies that produce half of all global output.

We have tabulated each company’s size, type, headcount, patent count, production, reserves, RP ratio, relative exposure, key assets and other notes.

The average company produces around 0.8MTpa of copper, has a 30-year reserve life, and derives 30% of its EBITDA from copper.

Copper: the economics?

Economics of copper production

This data-file quantifies the economics of producing copper, across a typical mining operation and a typical smelting/refining operation, to yield 99.99% pure copper output.

Marginal cost is likely around $7,000/ton ($3.20/lb) for a high-quality future project, with an emissions intensity close to 4 kg of CO2 per kg of copper.

But it depends heavily on ore grade. We estimate that a 0.1% reduction in future copper ore grading increases marginal cost by around 9% and CO2 intensity by around 10%, which matters as copper demand is set to treble in the energy transition.

Moreover, each $100/ton of CO2 prices would increase marginal cost by another 7.5%.

It is not unimaginable that copper prices could reach $15,000/ton in an aggressive energy transition scenario, if you stress-test the model.

Copper: global demand forecasts?

Global copper demand in the energy transition

This data-file estimate the growth in global copper demand as a result of the energy transition:  specifically, the rise of renewables, electric vehicles and other new energies technologies (charts below).

Global copper demand stood at 27MTpa in 2019, and will mostly likely treble to 75MTpa by 2050, in our base case scenario.

The data-file allows you to stress test different scenarios, varying the ultimate share of electric vehicles in the vehicle fleet, the rise of long-distance power transmission, global GDP growth, reductions in copper intensity, and the ultimate share of renewables in the grid.

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