Metal of plant origin? The mining industry could have a lasting makeover.
Malaysia’s Kinabalu Park, which surrounds Mount Kinabalu, the world’s 20 tallest peak, is home to a nickel mine like no other. Instead of heavy machinery, plumes of sulfur dioxide, or red rivers with runoff, you will find four acres of a green leafy shrub, tended since 2015 by local villagers. Once or twice a year, they shave off about a foot of growing plants 20 feet tall. They then burn this crop to produce an ashy âbio-oreâ that contains up to 25% nickel by weight.
The production of metal by growing plants, or by phytomining, has long been seen as an environmentally sustainable alternative to reshaping, or even replacing, the mining industry. Out of 320,000 recognized plant species, only around 700 are said to be âhyperaccumulatingâ, like that of Kinabalu. P. rufuschaneyi. Over time, they suck up dry soil from metals like nickel, zinc, cobalt and even gold.
While two-thirds of nickel is used to make stainless steel, the metal is also recovered by producers of everything from cookware to cell phones, from medical equipment to power generation. Zinc, on the other hand, is essential for producing paints, rubber, cosmetics, pharmaceuticals, plastics, inks, soaps and batteries. And, as supplies of these hard-to-find metals dry up around the world, demand remains stronger than ever.
The idea of ââphytomining was first put forward in 1983 by an agronomist from the US Department of Agriculture, Rufus L. Chaney. Other research groups before the Malaysian team have shown that the solar-powered, carbon-neutral metal mining process works in practice – a key step in convincing investors in the mining industry, who insisted on field trials of several acres to prove the principle. The latest data from Kinabalu Park, a UNESCO World Heritage Site on the island of Borneo, is finally turning heads in the industry as it shows the balance has tipped in favor of sustainability commercial phytomine.
“We can now demonstrate that steel farms can produce between 150 and 250 kilograms of nickel per hectare (170 to 280 pounds per acre), per year,” said Antony van der Ent, senior researcher at the Australian University of Queensland whose thesis work spurred the Malaysian lawsuit. In the middle of that range, a farmer would earn $ 3,800 per acre of nickel at daily 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”.
Take, for example, palm oil, a crop as renowned for its profitability as its role in deforestation in Asia and Africa. Farmers planting oil palms, before the pandemic, was scheduled to remove 2.84 metric tonnes (3.12 tonnes) of crude oil per year on average – or $ 2,710 at today’s prices. For farmers in Malaysia and Indonesia, where 90 percent of the world’s palm oil is grown, nickel cultivation may well prove to be a more attractive option.
âAt this point, phytomining can immediately become large scale for nickel, while phytomining for cobalt, thallium and selenium is within reach,â said van der Ent.
While van der Ent’s team has won over some in the mining industry, the adoption of phytomining is not yet on the fast track. This is despite the intrigue of Malaysia and other examples suggesting that while factories are of course less capital intensive and more environmentally friendly than traditional mining, they are also more efficient. Yet in an industry that van der Ent characterizes as resistant to change, the immediate future of phytomine may be more of a supplement to traditional mining than a replacement.
Several Indonesian nickel mining companies are now looking to partner with van der Ent’s Malaysian team. âWe have aligned several industrial partners who have agreed to implement trials in Indonesia,â he said. âBut due to COVID, this development is currently on hold. “
When travel restrictions are lifted and borders open, van der Ent hopes to show that there are a number of benefits to phytomine that traditional mining simply cannot deliver. âThere is an abundance of unconventional minerals that could be unlocked through phytomining,â he said. One example is the soil abundant in the tropics which typically contains 0.5 to 1 percent nickel by weight, which is below the threshold where a company could profitably implement conventional surface mining.
Surface mining takes place in thick layers of soil containing more than 1% nickel by weight which occurs in places like Brazil, Cuba, Indonesia, the Philippines and New Caledonia, the territory French South Pacific. This process involves removing a layer of soil or rock, called overburden, before mining that layer for the target metal. And that comes at a high environmental cost. Because nickel is difficult to mine, the process requires heavy diesel-powered, carbon-generating machinery, as well as large acid leaching facilities needed to separate the metal from its ore.
These nickel-rich soils, however, are becoming increasingly scarce – and it may well be that an insufficient supply will ultimately push more companies to adopt phytomine. That, and the fact that bio-ore contains 20 to 30 percent nickel by weight, and is also more compact and cheaper to transport than typical ores – which hover around one to three percent by weight.
Yet no matter how the Indonesian partnerships ultimately play out, large mining companies are unlikely to trade surface mines for shrubs overnight. That’s why phytoremediation, a spin-off technology that complements mining rather than replacing it, might just be the end of the corner.
Currently, as surface mining occurs, the surrounding topsoil is littered with toxic metal tailings. This layer usually has to be excavated, transported and sold in landfills, often at great cost to the mine operator. In the case of coal mining, the reclamation cost, for surface mined land, is on average $ 71,000 per acre. In the EU alone, there are approximately 130 million acres need cleaning. It’s a hefty bill for mining companies – and that’s if they choose to pay it. High level investigations in Indonesia, Australia, and US mining companies show that mining companies are too often willing to shirk their rehabilitation responsibilities.
The residue, however, is usually composed of nickel, cobalt, sodium, and cadmium. With a little physical or chemical treatment of the soil, one can create precisely the conditions under which certain hyperaccumulators thrive – it’s as simple as planting a seed and collecting the extra ore at a later date. “From the treasure basket”, as van der Ent said.
Marcus Radford, an environmental consultant based in Western Australia, added that phytomining at these sites is a win-win solution. This would make mine remediation cheaper, faster and easier. Add to that, it would revitalize the local ecosystem. âIt’s a way of putting back in place, rather than pulling out,â he said.
Phytoremediation has been tested in France, Greece, Albania and Italy, but the experiments have had varying levels of success. In the Italian region of Tuscany, for example, researchers have planted various species of poplars and willows on pyrite waste contaminated with arsenic. While both plants have grown successfully under difficult conditions, arsenic has not been recovered to a significant level. That said, small-scale phytoremediation in France and elsewhere has been shown to recover nickel, zinc and cadmium.
For the mining industry to embrace phytoremediation, the practice will need the support of the board of directors, van der Ent explained, adding that the support hinges on large-scale implementation. Scaling up requires funding, however, so there’s a little chicken-and-egg problem.
“It is only the adoption by industry that delays the translation of phytomine into large-scale application,” said van der Ent. âThe industry invariably requests a field demonstration of phytomine to prove operational viability, but is not prepared to fund such a pilot project. I firmly believe that once a proven large-scale field demonstration exists, it will attract funding. “
Van der Ent is optimistic that the surge delayed by the pandemic in Indonesia will do the trick. To be sure, however, he also plans to expand the trial in Malaysia to nearly 50 acres – which would require the application of an industrial-scale hydrometallurgical plant, which separates the target metal, in this. case nickel, of its ore via a water-based medium. They won’t have to manually burn the crop like they currently do, which means the process will be carbon negative, unlike what van der Ent calls carbon neutral.
Once the COVID restrictions are lifted, he hopes the team will bring new life to the term “fusion factories.”