I was surprised to learn that some plants absorb so much nickel, it can be "mined" by processing them. The BBC reports:
Sixteen years ago, Aiyen Tjoa was exploring a small mining town of Sorowako in the heart of the Indonesian island of Sulawesi. Sorowako once had been a home to immense diversity of plants, and most of them were found nowhere else. But then the small town became the hub of one of the largest nickel mining areas in the world, with one company alone extracting 5% of the global nickel supply.
When Tjoa, a soil biologist and lecturer in Tadulako University in Central Sulawesi, arrived in Sorowako in 2004, most of the lush vegetation had already been cleared for mining, leaving barren soil and dusty roads in its place.
But some bushes and young trees survived. Back then, Tjoa was eager to find those rare plants that were adapting well to their new, nickel-rich surroundings. These, she reasoned, could be “super plants” capable of taking up high levels of nickel from the soil and storing it in surprisingly high quantities. As well as cleaning the soil, these nickel-rich plants could be “mined” to provide an alternative source of the metal, allowing nickel to be harvested without destroying the ecosystem.
. . .
The University of Queensland’s [Antony] van der Ent [a plant ecophysiologist] has calculated that a hyper-accumulator like Phyllantus balgoyii can produce an estimated 120kg [264 pounds] of nickel per hectare every year. That translates to a market value of around $1,754 per hectare [2.47 acres]. Extracting the nickel involves pruning the shoots – which hold the highest concentrations of the metal – and burning them, after which the nickel can be separated from the ash. This involves releasing carbon dioxide through burning, but the continuous cultivation of nickel hyper-accumulators can be considered carbon neutral, says van der Ent. “All carbon released from the burning will be ‘captured’ again by the newly growing crop in a few months,” he says.
. . .
In Sabah, Malaysia, van der Ent has been conducting phytomining field trials since 2014. “We found out that phytomining really works,” he says. This could also be applied in soils that have not been mined but have naturally high levels of nickel. But van der Ent underlines that the technology is not aimed at replacing open-pit mining. That would be hard, given that Indonesia is the largest nickel producer in the world, with around 73 million tonnes of nickel exported last year. Instead, phytomining could be done in parallel. Most importantly, unlike traditional mining, which often clashes with indigenous communities, “we envisage that it will be implemented by smallholders in rural communities living on nickel-rich areas as an alternative form of agriculture”, says van der Ent.
There's more at the link.
Nature never ceases to amaze, does it? Who'd have thought that processing plants could be a viable method of "mining" a vital metal like nickel?