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Phytomining: Extracting Metals From Trees

Updated: Oct 2, 2021

Scientists are starting to mine valuable metals from an unusual source: plants.

If you haven't heard the word phytomining before, look out, it's highly likely to enter the lexicon more often in the future. That would be very good news. And not just in Malaysia’s Kinabalu Park, which surrounds Mount Kinabalu (pictured), the 20th-largest peak in the world, where there is a nickel mine like no other.

Instead of the usual heavy machinery and plumes of sulfur dioxide, there's four acres of a leafy-green shrub, tended to since 2015 by local villagers. Once or twice per year, they shave off about a foot of growth from the 20-foot-tall plants. Then, they burn that crop to produce an ashy “bio-ore” that is up to 25 percent nickel by weight.

Producing metal by growing plants, or phytomining, has long been tipped as an alternative, environmentally-sustainable way to reshape – if not replace – the mining industry. Of 320,000 recognized plant species, only around 700 are so-called “hyperaccumulators,” like Kinabalu’s P. rufuschaneyi. Over time, they suck the soil dry of metals like nickel, zinc, cobalt, and even gold.

The idea of phytomining was first proposed in 1983 by an agronomist at the U.S. Department of Agriculture named Rufus L. Chaney. Other research groups before the Malaysia team have shown that the solar-powered and carbon-neutral metal extraction process works in practice - a key step to winning over mining industry investors, who have insisted on field trials of several acres to show proof of principle. The most recent data out of Kinabalu Park, a UNESCO-listed heritage site located on the island of Borneo, is finally turning industry heads, as they shows the scales have tipped in favor of phytomining’s commercial viability.

How so? “We can now demonstrate that metal farms can produce between 150 to 250 kilograms of nickel per hectare (170 to 280 pounds per acre), annually,” said Antony van der Ent, a senior research fellow at Australia’s University of Queensland whose thesis work spurred the Malaysia trial. At the midpoint of that range, a farmer would net a cool $3,800 per acre of nickel at today’s prices – which, van der Ent added, is “on par with some of the best-performing agricultural crops on fertile soils, while operating costs are similar.”

While van der Ent’s team has won over some in the mining industry, adoption of phytomining isn’t yet on the fast track. That’s despite the Malaysia plot and other examples suggesting that while plants are of course less capital intensive and more environmentally friendly than traditional mining, they are also more efficient. Still, in an industry that van der Ent characterizes as resistant to change, phytomining’s immediate future could be more as a complement to traditional mining than its replacement.

But, in time....


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