Researchers discover trees that feed off metal-rich deposits Metal Tech News Weekly Edition – March 11, 2020
Could we mine the nickel we need for lithium-ion batteries, stainless steel and other applications in much the same way as we make pure maple syrup – from the sap of trees? Research at one nickel syrup agromining grove in Malaysia is demonstrating that this concept is not as far-fetched as it might sound.
While most of Earth's flora tend to avoid the sulfide-rich and potassium-poor ultramafic deposits that host much of the world's nickel – geologists often use sparse vegetation as an early indicator of a potential orebody just below the surface – there are some plants known as hyperaccumulators that thrive in nickel-rich environments.
One such hyperaccumulating species is Antidesma montis‐silam, a fast-growing tropical tree that loves to sink its roots into ultramafic bedrock and suck up nickel and manganese.
The leaves of the Antidesma montis‐silam, which grows on the Malaysia side of the island of Borneo, contain as much as 3.3% nickel and 4.6% manganese – and the sap has much higher concentrations of these metals.
Interestingly, nickel and manganese are both important ingredients in the lithium-ion batteries that power electric vehicles, making this tropical plant on the island of Borneo a potential sustainable source of these battery metals.
Testing has shown the bright green sap tapped from these trees or squeezed from the leaves contain as much as 16.9 percent nickel. This means this industrious tree has mined and processed the ore and produced a liquid concentrate that is ready to be delivered to a refinery.
"The identification of more hyperaccumulator plants is important for advancing the evolutionary understanding of the hyperaccumulation phenomenon, for adding potentially suitable 'metal crops' to the inventory of 'agrominers'," scientist wrote in a 2017 report on Antidesma montis‐silam.
Thanks to the work of these researchers, along with the convenience of handheld x‐ray fluorescence (XRF) scanners, at least 25 species of nickel-loving species have been identified in the Sabah region of Malaysia, a global hotspot for ultramafic deposits and hyperaccumulating plants sucking metals out of them.
A group of researchers that include Alan Baker, a botany professor at the University of Melbourne, and Antony van der Ent, a researcher at the University of Queensland, are bettering our understanding of hyperaccumulating plants, especially on Borneo.
With a small plot of land on the Malaysia side of the island, these researchers have conceptually proven the concept of using hyperaccumulating species to "mine" nickel. This unique merge of farming and mining, known as agromining or phytomining, could prove to be a new industry for individuals living on this tropical island.
"Every six to 12 months, a farmer shaves off one foot of growth from these nickel-hyper-accumulating plants and either burns or squeezes the metal out. After a short purification, farmers could hold in their hands roughly 500 pounds of nickel citrate, potentially worth thousands of dollars on international markets," according to a Feb. 26 New York Times article authored by Ian Morse.
This could lead to nickel groves sitting atop the ultramafic deposits that Borneo and the Philippines are known for.
For those concerned about the natural tropical fauna of these island being replaced by another "cash crop" such as palm oil, the good news is the nickel-rich deposits shun most other species. This means that the areas that would be planted are barren of most plant-life, which cannot tolerate the natural soil chemistry.
"We can grow these plants on soils where it's already been deforested," Dr. Baker told The New York Times. "It's a way of putting back, rather than taking away."
Baker and van der Ent's work could result in other mining related uses for metal loving plants.
The research carried out by van der Ent has led to the discovery of 400 new hyperaccumulator species and 16 plant species new to science.
Some of these species thrive on arsenic, lead, mercury and selenium. It is conceivable that these plants could be used to suck up metals that are toxic to virtually every other plant and animal from abandoned or simply closed mines.
While syrup made from the neon blue-green sap of hyperaccumulator trees sitting atop ultramafic deposits on Borneo may only provide a proverbial drop in the bucket of the growing global need for nickel and manganese, agromining does provide a potential carbon negative source for these battery metals.
And the toxic metals loving cousins of these unique plants could feed off the tailings of mines long after they are closed.