Phytomining:
The planting (and subsequent harvesting) of vegetation that selectively concentrate specific metals from the environment into their tissues, for the primary or subsidiary purpose of commercial exploitation of the extracted metal. [Wiktionary]
Noted in “Plants that suck metals from the soil can be farmed to make our tech,” Michael Allen, NewScientist (9 January 2021):
One incident that helped draw that attention was [Anthony] van der Ent’s discovery in Borneo. The plant’s sap turned out to contain a whopping 25 per cent nickel by weight. “It is the best candidate metal crop we have ever found,” he says.
The first thing he did on seeing this plant was ask the park ranger where it came from. He couldn’t remember. So van der Ent offered local people a reward if they could tell him – to no avail. It wasn’t until 2015, a few years after the initial discovery, that he chanced upon a clump of the plants growing on a nearby hillside. From there, he began experimenting with farming metal, otherwise known as agromining or phytomining, as an environmentally friendly alternative to mining. He even named his shrub Phyllanthus rufuschaneyi in homage to the inventor of agromining.
If you go to the state of Sabah in Borneo these days, you can find what van der Ent calls the “first tropical metal farm”. There, he and his colleagues are growing that nickel-loving woody shrub. Each year, they coppice the plants, pulp them and extract the metal. In 2019, they reported a yield of 250 kilograms of nickel a year – currently worth almost $4000 – from each hectare of land.
I’ve gotta wonder how long a field can be productive. Or does the metal move upward somehow?
