“Phytomining” is the Sustainable Future of Trace Metal Mining

Large tropical mining companies could soon present a green alternative to traditional open pit mining by allowing plants to draw in trace minerals rather than mining equipment.

Plant-mining, as it is called, relies on a few selected species of plants that can literally soak up dry soil for minerals like zinc, selenium, nickel, and cobalt.

Instead of polluted rivers, columns of sulfur dioxide and the multitude of heavy machinery, phytominin, as a demonstration site that began in 2015 attests, relies on locals to trim a few feet from a 20-foot-tall green bush. . These leftovers are collected and burned to create “bio-mineral” filled with 20 to 25% nickel by weight.

The mining industry is eager to see how this eco-friendly alternative to one of the more carbon-heavy industries can really work. Allowing plants to collect materials for you is better than searching the ground for it on a remote island like Borneo.

“We can now show that metal farms can produce between 150 and 250 kilograms of nickel per hectare (170 to 280 pounds per acre), annually,” said Antony van der Ent, principal investigator at the University of Queensland in Australia. Grinding, in a special report on plant breeding in Indonesia.

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“At this stage, plant mining can go full scale for nickel right away, while plant mining for cobalt, thallium and selenium is within reach,” van der Ent said.

Metal cultivation

Nickel mining companies could be drooling over the scientific modeling van der Ent and other experts in “metal farmers” have found that nickel plant mining costs similar to that of growing corn, but with a gross post-production of around $ 1,800 per hectare, making it a very important activity. profitable.

While the Grinding report details phytomining in Borneo, trials It has been done in the United States, Italy, Albania, Canada, France, Spain and New Zealand. There are around 700 recognized “hyperaccumulators”, which is the term for plant species that can absorb large amounts of these minerals before depositing them on their shoots, branches and leaves.

There are some parallels with food agriculture, for example, calcium amendment is vital, while nitrogen and organic material supplementation appears to increase available nickel in plant shoots.

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By far the most advantageous aspect of plant farming if you run a major mining company is not actually where the soil is rich, but where the soil is poor, in nickel. At concentrations of 1% or less, the only option is to strip the mine, for example, in places like Brazil, Cuba, Indonesia, the Philippines and New Caledonia.

It involves removing a top layer of rock and soil from a stretch of land and using heavy acid leaching machinery to extract the scarce nickel particles. All this unhappy work for very little metal results in a layer of toxic topsoil full of entrained metal particles that must be collected and sold in landfills at great cost to miners.

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With production at the Indonesian site slowed due to COVID, van der Ent is using this time to develop a hydrometallurgical extraction method to avoid burning the plant cuttings for nickel, thereby removing the generated CO2. In fact, it is exciting news.

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